UNITED STATES

DEPARTMENT OF COMMERCE

Penny Pritzker

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Dr. Kathryn D. Sullivan

Under Secretary for Oceans & Atmosphere 

NOAA Administrator

NAT OI NAL OCEANIC AND ATMOSPHERIC ADMINISTRAT OI N

U.S.DEPARTMENT OF COMMERCE

NOAA Technical Memorandum GLERL-169

A risk assessment of potential Great Lakes aquatic invaders

Abigail Fusaro1 

Emily Baker2

Whitney Conard2 

Alisha Davidson1

Kyle Dettloff3 

Jane Li4 

Gabriela Núñez-Mir5 

Rochelle Sturtevant6

Edward Rutherford7

1

Wayne State University, 5047 Gullen Mall, Detroit, MI 48202 

2

University of Michigan, SNRE, 440 Church St., Ann Arbor, MI 4810

3

Oregon State University, Corvallis, OR 97331

4

Skidmore College, Saratoga Springs, NY 12866

5

Worcester Polytechnic Institute, Worcester, MA 01609

6

NOAA Sea Grant, 4840 S. State Rd., Ann Arbor, MI 48108

7

NOAA Great Lakes Environmental Research Laboratory, 4840 S. State Rd., Ann Arbor, MI 48108
NOTICE

Mention of a commercial company or product does not constitute an endorsement by NOAA. 

Use of information from this publication concerning proprietary products or the tests of such 

products for publicity or advertising purposes is not authorized. This is GLERL Contribution No. 

1841.

This publication is available as a PDF file and can be downloaded from GLERL’s web site: 

www.glerl.noaa.gov. Hard copies can be requested from GLERL Information Services, 

4840 S. State Rd., Ann Arbor, MI 48108.

pubs.glerl@noaa.gov.
i 

A RISK ASSESSMENT OF POTENTIAL GREAT LAKES AQUATIC INVADERS 

Abigail Fusaro, Emily Baker, Whitney Conard, Alisha Davidson, Kyle Dettloff, Jane Li, 

Gabriela Núñez-Mir, Rochelle Sturtevant, Ed Rutherford 

TABLE OF CONTENTS 

1. INTRODUCTION ...................................................................................................................... 1

1.1 Aquatic Invasive Species in the Laurentian Great Lakes .................................................................... 1

1.2 Project Background ............................................................................................................................. 2

1.3 Review of Invasive Species Risk Assessments ................................................................................... 2

2. METHODS ................................................................................................................................. 3

2.1 Overview of Risk Assessment Structure ............................................................................................. 3

2.2 Potential for Introduction .................................................................................................................... 3

2.3 Potential for Establishment ................................................................................................................. 6

2.4 Potential for Impact ............................................................................................................................. 8

2.5 Application to Great Lakes Watchlist Species .................................................................................. 11

3. RESULTS ................................................................................................................................. 12

3.1 Framework ........................................................................................................................................ 12

3.2 Analyses ............................................................................................................................................ 32

4. DISCUSSION ........................................................................................................................... 37

5. ACKNOWLEDGEMENTS................................................................................................... 38

6. LITERATURE CITED ............................................................................................................. 38

APPENDIX A. RISK ASSESSMENTS ....................................................................................... 42

A.1 Fishes ............................................................................................................................................... 42

Scientific Name: Alburnus alburnus ............................................................................................... 42

Section A: Potential for Introduction .......................................................................................... 42

Section B: Potential for Establishment ....................................................................................... 47

Section C: Potential for Impact ................................................................................................... 56

Scientific Name: Atherina boyeri ................................................................................................... 64
ii

Section A: Potential for Introduction .......................................................................................... 64

Section B: Potential for Establishment ....................................................................................... 69

Section C: Potential for Impact ................................................................................................... 78

Scientific Name: Babko gymnotrachelus ........................................................................................ 85

Section A: Potential for Introduction .......................................................................................... 85

Section B: Potential for Establishment ....................................................................................... 91

Section C: Potential for Impact ................................................................................................. 104

Scientific Name: Benthophilus stellatus ....................................................................................... 113

Section A: Potential for Introduction ........................................................................................ 113

Section B: Potential for Establishment ..................................................................................... 118

Section C: Potential for Impact ................................................................................................. 127

Scientific Name: Carassius carassius ........................................................................................... 134

Section A: Potential for Introduction ........................................................................................ 134

Section B: Potential for Establishment ..................................................................................... 138

Section C: Potential for Impact ................................................................................................. 147

Scientific Name: Channa argus .................................................................................................... 154

Section A: Potential for Introduction ........................................................................................ 154

Section B: Potential for Establishment ..................................................................................... 159

Section C: Potential for Impact ................................................................................................. 168

Scientific Name: Clupeonella cultriventris ................................................................................... 177

Section A: Potential for Introduction ........................................................................................ 177

Section B: Potential for Establishment ..................................................................................... 182

Section C: Potential for Impact ................................................................................................. 191

Scientific Name: Cottus gobio ...................................................................................................... 200

Section A: Potential for Introduction ........................................................................................ 200

Section B: Potential for Establishment ..................................................................................... 205

Section C: Potential for Impact ................................................................................................. 213

Scientific Name: Ctenopharyngodon idella .................................................................................. 221
iii

Section A: Potential for Introduction ........................................................................................ 221

Section B: Potential for Establishment ..................................................................................... 226

Section C: Potential for Impact ................................................................................................. 234

Scientific Name: Cyprinella whipplei ........................................................................................... 243

Section A: Potential for Introduction ........................................................................................ 243

Section B: Potential for Establishment ..................................................................................... 248

Section C: Potential for Impact ................................................................................................. 258

Scientific Name: Hypophthalmichthys molitrix ............................................................................ 267

Section A: Potential for Introduction ........................................................................................ 267

Section B: Potential for Establishment ..................................................................................... 273

Section C: Potential for Impact ................................................................................................. 281

Scientific Name: Hypophthalmichthys nobilis .............................................................................. 291

Section A: Potential for Introduction ........................................................................................ 291

Section B: Potential for Establishment ..................................................................................... 297

Section C: Potential for Impact ................................................................................................. 306

Scientific Name: Ictalurus furcatus .............................................................................................. 316

Section A: Potential for Introduction ........................................................................................ 316

Section B: Potential for Establishment ..................................................................................... 321

Section C: Potential for Impact ................................................................................................. 330

Scientific Name: Knipowitschia caucasica ................................................................................... 338

Section A: Potential for Introduction ........................................................................................ 338

Section B: Potential for Establishment ..................................................................................... 344

Section C: Potential for Impact ................................................................................................. 355

Scientific Name: Leuciscus idus ................................................................................................... 362

Section A: Potential for Introduction ........................................................................................ 362

Section B: Potential for Establishment ..................................................................................... 367

Section C: Potential for Impact ................................................................................................. 375

Scientific Name: Leuciscus leuciscus ........................................................................................... 383
iv

Section A: Potential for Introduction ........................................................................................ 383

Section B: Potential for Establishment ..................................................................................... 388

Section C: Potential for Impact ................................................................................................. 397

Scientific Name: Neogobius fluviatilis ......................................................................................... 405

Section A: Potential for Introduction ........................................................................................ 405

Section B: Potential for Establishment ..................................................................................... 410

Section C: Potential for Impact ................................................................................................. 420

Scientific Name: Oncorhynchus keta ............................................................................................ 429

Section A: Potential for Introduction ........................................................................................ 429

Section B: Potential for Establishment ..................................................................................... 434

Section C: Potential for Impact ................................................................................................. 444

Scientific Name: Osmerus eperlanus ............................................................................................ 453

Section A: Potential for Introduction ........................................................................................ 453

Section B: Potential for Establishment ..................................................................................... 457

Section C: Potential for Impact ................................................................................................. 466

Scientific Name: Perca fluviatilis ................................................................................................. 475

Section A: Potential for Introduction ........................................................................................ 475

Section B: Potential for Establishment ..................................................................................... 480

Section C: Potential for Impact ................................................................................................. 489

Scientific Name: Perccottus glenii ............................................................................................... 498

Section A: Potential for Introduction ........................................................................................ 498

Section B: Potential for Establishment ..................................................................................... 503

Section C: Potential for Impact ................................................................................................. 512

Scientific Name: Phoxinus phoxinus ............................................................................................ 520

Section A: Potential for Introduction ........................................................................................ 520

Section B: Potential for Establishment ..................................................................................... 525

Section C: Potential for Impact ................................................................................................. 533

Scientific Name: Pseudorasbora parva ........................................................................................ 541
v 

Section A: Potential for Introduction ........................................................................................ 541

Section B: Potential for Establishment ..................................................................................... 546

Section C: Potential for Impact ................................................................................................. 555

Scientific Name: Rutilus rutilus .................................................................................................... 564

Section A: Potential for Introduction ........................................................................................ 564

Section B: Potential for Establishment ..................................................................................... 569

Section C: Potential for Impact ................................................................................................. 578

Scientific Name: Sander lucioperca ............................................................................................. 587

Section A: Potential for Introduction ........................................................................................ 587

Section B: Potential for Establishment ..................................................................................... 591

Section C: Potential for Impact ................................................................................................. 600

Scientific Name: Silurus glanis..................................................................................................... 608

Section A: Potential for Introduction ........................................................................................ 608

Section B: Potential for Establishment ..................................................................................... 612

Section C: Potential for Impact ................................................................................................. 621

Scientific Name: Syngnathus abaster ........................................................................................... 630

Section A: Potential for Introduction ........................................................................................ 630

Section B: Potential for Establishment ..................................................................................... 635

Section C: Potential for Impact ................................................................................................. 643

A.2 Bivalves .......................................................................................................................................... 650

Scientific Name: Limnoperna fortunei ......................................................................................... 650

Section A: Potential for Introduction ........................................................................................ 650

Section B: Potential for Establishment ..................................................................................... 655

Section C: Potential for Impact ................................................................................................. 663

Scientific Name: Monodacna colorata ......................................................................................... 672

Section A: Potential for Introduction ........................................................................................ 672

Section B: Potential for Establishment ..................................................................................... 676

Section C: Potential for Impact ................................................................................................. 685
vi

A.3 Bryozoans....................................................................................................................................... 693

Scientific Name: Fredericella sultana .......................................................................................... 693

Section A: Potential for Introduction ........................................................................................ 693

Section B: Potential for Establishment ..................................................................................... 698

Section C: Potential for Impact ................................................................................................. 707

A.4 Crustaceans - Amphipods .............................................................................................................. 716

Scientific Name: Apocorophium lacustre ..................................................................................... 716

Section A: Potential for Introduction ........................................................................................ 716

Section B: Potential for Establishment ..................................................................................... 721

Section C: Potential for Impact ................................................................................................. 730

Scientific Name: Chelicorophium curvispinum ............................................................................ 737

Section A: Potential for Introduction ........................................................................................ 737

Section B: Potential for Establishment ..................................................................................... 742

Section C: Potential for Impact ................................................................................................. 752

Scientific Name: Dikerogammarus haemobaphes ........................................................................ 761

Section A: Potential for Introduction ........................................................................................ 761

Section B: Potential for Establishment ..................................................................................... 766

Section C: Potential for Impact ................................................................................................. 775

Scientific Name: Dikerogammarus villosus.................................................................................. 782

Section A: Potential for Introduction ........................................................................................ 782

Section B: Potential for Establishment ..................................................................................... 787

Section C: Potential for Impact ................................................................................................. 796

Scientific Name: Echinogammarus warpachowskyi ..................................................................... 804

Section A: Potential for Introduction ........................................................................................ 804

Section B: Potential for Establishment ..................................................................................... 809

Section C: Potential for Impact ................................................................................................. 817

Scientific Name: Obesogammarus crassus ................................................................................... 824

Section A: Potential for Introduction ........................................................................................ 824
vii 

Section B: Potential for Establishment ..................................................................................... 829

Section C: Potential for Impact ................................................................................................. 838

Scientific Name: Obesogammarus obesus .................................................................................... 845

Section A: Potential for Introduction ........................................................................................ 845

Section B: Potential for Establishment ..................................................................................... 850

Section C: Potential for Impact ................................................................................................. 859

Scientific Name: Pontogammarus robustoides ............................................................................. 867

Section A: Potential for Introduction ........................................................................................ 867

Section B: Potential for Establishment ..................................................................................... 872

Section C: Potential for Impact ................................................................................................. 881

A.5 Crustaceans - Cladocerans ............................................................................................................. 890

Scientific Name: Cornigerius maeoticus maeoticus ..................................................................... 890

Section A: Potential for Introduction ........................................................................................ 890

Section B: Potential for Establishment ..................................................................................... 895

Section C: Potential for Impact ................................................................................................. 904

Scientific Name: Daphnia cristata ............................................................................................... 912

Section A: Potential for Introduction ........................................................................................ 912

Section B: Potential for Establishment ..................................................................................... 917

Section C: Potential for Impact ................................................................................................. 925

Scientific Name: Podonevadne trigona ovum............................................................................... 933

Section A: Potential for Introduction ........................................................................................ 933

Section B: Potential for Establishment ..................................................................................... 938

Section C: Potential for Impact ................................................................................................. 946

A.6 Crustaceans - Copepods ................................................................................................................. 953

Scientific Name: Calanipeda aquaedulcis .................................................................................... 953

Section A: Potential for Introduction ........................................................................................ 953

Section B: Potential for Establishment ..................................................................................... 958

Section C: Potential for Impact ................................................................................................. 967
viii

Scientific Name: Cyclops kolensis................................................................................................975

Section A: Potential for Introduction ........................................................................................975

Section B: Potential for Establishment .....................................................................................980

Section C: Potential for Impact.................................................................................................989

Scientific Name: Ectinosoma abrau .............................................................................................997

Section A: Potential for Introduction ........................................................................................997

Section B: Potential for Establishment ................................................................................... 1002

Section C: Potential for Impact............................................................................................... 1009

Scientific Name: Heterocope appendiculata .............................................................................. 1017

Section A: Potential for Introduction ...................................................................................... 1017

Section B: Potential for Establishment ................................................................................... 1022

Section C: Potential for Impact............................................................................................... 1030

Scientific Name: Heterocope caspia........................................................................................... 1038

Section A: Potential for Introduction ...................................................................................... 1038

Section B: Potential for Establishment ................................................................................... 1043

Section C: Potential for Impact............................................................................................... 1053

Scientific Name: Paraleptastacus spinicaudus triseta ............................................................... 1061

Section A: Potential for Introduction ...................................................................................... 1061

Section B: Potential for Establishment ................................................................................... 1066

Section C: Potential for Impact............................................................................................... 1074

A.7 Crustaceans - Mysids................................................................................................................... 1081

Scientific Name: Limnomysis benedeni ...................................................................................... 1081

Section A: Potential for Introduction ...................................................................................... 1081

Section B: Potential for Establishment ................................................................................... 1086

Section C: Potential for Impact............................................................................................... 1096

Scientific Name: Paramysis (Mesomysis) intermedia ................................................................ 1104

Section A: Potential for Introduction ...................................................................................... 1104

Section B: Potential for Establishment ................................................................................... 1109
ix

Section C: Potential for Impact ............................................................................................... 1118

Scientific Name: Paramysis (Metamysis) ullskyi ........................................................................ 1125

Section A: Potential for Introduction ...................................................................................... 1125

Section B: Potential for Establishment ................................................................................... 1130

Section C: Potential for Impact ............................................................................................... 1138

Scientific Name: Paramysis (Serrapalpisis) lacustris ................................................................ 1146

Section A: Potential for Introduction ...................................................................................... 1146

Section B: Potential for Establishment ................................................................................... 1150

Section C: Potential for Impact ............................................................................................... 1159

A.8 Crustaceans - Crayfishes .............................................................................................................. 1167

Scientific Name: Cherax destructor ........................................................................................... 1167

Section A: Potential for Introduction ...................................................................................... 1167

Section B: Potential for Establishment ................................................................................... 1172

Section C: Potential for Impact ............................................................................................... 1182

A.9 Crustaceans - Crabs ...................................................................................................................... 1189

Scientific Name: Rhithropanopeus harrisii ................................................................................ 1189

Section A: Potential for Introduction ...................................................................................... 1189

Section B: Potential for Establishment ................................................................................... 1194

Section C: Potential for Impact ............................................................................................... 1204

Scientific Name: Sinelobus stanfordi .......................................................................................... 1212

Section A: Potential for Introduction ...................................................................................... 1212

Section B: Potential for Establishment ................................................................................... 1217

Section C: Potential for Impact ............................................................................................... 1225

A.10 Platyhelminthes .......................................................................................................................... 1232

Scientific Name: Leyogonimus polyoon ..................................................................................... 1232

Section A: Potential for Introduction ...................................................................................... 1232

Section B: Potential for Establishment ................................................................................... 1237

Section C: Potential for Impact ............................................................................................... 1245
x 

A.11 Polychaetes................................................................................................................................. 1252

Scientific Name: Hypania invalida ............................................................................................. 1252

Section A: Potential for Introduction ...................................................................................... 1252

Section B: Potential for Establishment ................................................................................... 1257

Section C: Potential for Impact ............................................................................................... 1266

A.12 Rotifers ....................................................................................................................................... 1273

Scientific Name: Brachionus leydigii ......................................................................................... 1273

Section A: Potential for Introduction ...................................................................................... 1273

Section B: Potential for Establishment ................................................................................... 1279

Section C: Potential for Impact ............................................................................................... 1287

Scientific Name: Filinia cornuta ................................................................................................ 1294

Section A: Potential for Introduction ...................................................................................... 1294

Section B: Potential for Establishment ................................................................................... 1299

Section C: Potential for Impact ............................................................................................... 1306

Scientific Name: Filinia passa .................................................................................................... 1314

Section A: Potential for Introduction ...................................................................................... 1314

Section B: Potential for Establishment ................................................................................... 1318

Section C: Potential for Impact ............................................................................................... 1326

A.13 Plants .......................................................................................................................................... 1333

Scientific Name: Crassula helmsii .............................................................................................. 1333

Section A: Potential for Introduction ...................................................................................... 1333

Section B: Potential for Establishment ................................................................................... 1337

Section C: Potential for Impact ............................................................................................... 1346

Scientific Name: Egeria densa ................................................................................................... 1353

Section A: Potential for Introduction ...................................................................................... 1353

Section B: Potential for Establishment ................................................................................... 1359

Section C: Potential for Impact ............................................................................................... 1369

Scientific Name: Eichhornia crassipes ....................................................................................... 1378
xi

Section A: Potential for Introduction ...................................................................................... 1378

Section B: Potential for Establishment ................................................................................... 1384

Section C: Potential for Impact ............................................................................................... 1394

Scientific Name: Hydrilla verticillata ......................................................................................... 1403

Section A: Potential for Introduction ...................................................................................... 1403

Section B: Potential for Establishment ................................................................................... 1409

Section C: Potential for Impact ............................................................................................... 1419

Scientific Name: Hygrophila polysperma ................................................................................... 1429

Section A: Potential for Introduction ...................................................................................... 1429

Section B: Potential for Establishment ................................................................................... 1435

Section C: Potential for Impact ............................................................................................... 1444

Scientific Name: Myriophyllum aquaticum ................................................................................ 1452

Section A: Potential for Introduction ...................................................................................... 1452

Section B: Potential for Establishment ................................................................................... 1457

Section C: Potential for Impact ............................................................................................... 1466

Scientific Name: Pistia stratiotes ............................................................................................... 1475

Section A: Potential for Introduction ...................................................................................... 1475

Section B: Potential for Establishment ................................................................................... 1480

Section C: Potential for Impact ............................................................................................... 1489

Scientific Name: Stratiotes aloides ............................................................................................. 1498

Section A: Potential for Introduction ...................................................................................... 1498

Section B: Potential for Establishment ................................................................................... 1503

Section C: Potential for Impact ............................................................................................... 1510

APPENDIX B: Literature Cited in Assessments ...................................................................... 1518
A RISK ASSESSMENT OF POTENTIAL GREAT LAKES AQUATIC INVADERS 

Abigail Fusaro, Emily Baker, Whitney Conard, Alisha Davidson, Kyle Dettloff, Jane Li, 

Gabriela Núñez-Mir, Rochelle Sturtevant, Ed Rutherford 

1. INTRODUCTION

Introduced species have the potential for both ecological and socioeconomic effects. Once established, 

these species can be nearly impossible to eradicate (Hobbs & Humphries 1995). In the few successful 

eradication efforts, the cost has been substantial (Simberloff 2003). Managing spread and controlling for 

impact are also costly (Leung et al. 2002). At least 31% nonindigenous species established in the Great 

Lakes have significant impacts (Sturtevant et al. 2014). The most economically and practically effective 

strategy is therefore to prevent species introduction in the first place (Lodge et al. 2006). As a means of 

prioritizing management efforts, risk assessment tools that consider vectors and pathways of introduction, 

species life history traits, habitat suitability, historical patterns of invasion, impacts realized in other 

invaded regions have become commonly implemented (Gordon et al. 2012, Keller et al. 2009). In order to 

accurately predict risk, a thorough understanding of these potentially introduced species is needed (Keller 

et al. 2007b, Springborn et al. 2011—but see Simberloff 2003). However, species and pathway 

information can also be scarce or diffuse (e.g., 95/156 species assessed as “not enough known” in USEPA 

2008). 

1.1 Aquatic Invasive Species in the Laurentian Great Lakes 

The Laurentian Great Lakes is one of the most heavily invaded aquatic systems in the world with over 

180 documented aquatic nonindigenous species, the peak invasion rate was estimated to be 2.8 species 

introduced per year (1990-1995) (GLRI Task Force 2010, Mills et al. 1993, Ricciardi 2006). Some of 

these nonindigenous species may become invasive (i.e. “those species whose introduction does or is likely 

to cause economic or environmental harm or harm to human health” (E.O. 13112, 1999) and threaten the 

ecological and/or socio-economic value of the Great Lakes. In contrast, some nonindigenous species are 

capable of contributing value to the Great Lakes. Pacific salmonids, for instance, are stocked annually by 

the millions and provide a major support for the Great Lakes’ multi-billion dollar fishery (Kocik and 

Jones 1999, Southwick Associates 2007, Talhelm 1985, USACE 2012, USFWS/GLFC 2010). 

This study sought to identify the potential for introduction, establishment, and impact of 67 species 

identified in published literature as being highly likely to invade the Great Lakes basin. We developed 

tools that apply a consistent approach across all taxonomic groups and vectors in order to allow for 

comparison across these species, unlike previous studies. Our framework was comprised of three 

qualitative, question-driven assessments for which we relied on thorough Internet and literature searches, 

as well as expert judgment, to score and rank species’ introduction, establishment, and impact potentials. 

Scores were binned into categories of low, moderate, high, or unknown potential—the latter based on 

being unable to assess based on information availability. By ranking the potential for introduction via any 

of six major pathways; the potential for species to become established and overwinter; and the 

environmental impact, socio-economic impact, and beneficial effect of each species, this system provided 

a method of identifying and comparing impacts across taxa and type of impact. These assessments will 

inform ongoing work to map cumulative risk of invasion in the Great Lakes and guide prioritization by 

managers in their monitoring and response programs. 

1 
2 

1.2 Project Background

In cooperation with USGS, NOAA GLERL has been tracking nonindigenous aquatic species in the Great 

Lakes system since 2003 and serving that information through the GLANSIS database 

(http://www.glerl.noaa.gov/res/Programs/glansis/glansis.html). Information in the database includes an 

overview of the species life history, ecology, and invasion history as well as maps of current distribution, 

comprehensive impact assessment and overview of management options. With funding from the Great 

Lakes Restoration Initiative, beginning in 2011, we were able to begin adding information on species that 

were not yet established in the Great Lakes, but had been assessed in the peer-reviewed scientific 

literature as posing a risk of invasion. We aimed to provide a similar comprehensive risk assessment 

looking in detail at the risks for introduction, establishment and impact along with information on life 

history, ecology, invasion history, and management options to help guide early detection and rapid 

response efforts. 

1.3 Review of Invasive Species Risk Assessments

Biological invasion risk assessment continues to be a young field, with a variety of approaches, scope, 

content, and required elements (reviewed in Verbrugge et al. 2010, Dahlstrom et al. 2011). Risk 

assessment can have different endpoints, with species’ introduction commonly chosen (Andersen et al. 

2004); they are less consistent in their treatment of establishment (colonization and spread) and 

consequence (impact). However, given the number of failed introductions, an understanding of 

establishment potential remains important. Impact is necessary to give a full understanding of risk (which 

includes both the probability of an event occurring and the severity of that event). Understanding impact 

is also a key element to species’ management, as an understanding of small versus large effects allows 

better prioritization of management efforts (Parker et al. 1999). 

Structurally, invasion risk may be evaluated quantitatively (with numerical probabilities or descriptors), 

qualitatively (with categorical descriptors), semi-quantitatively (by representing quantitative data with 

categorical descriptors), or using rule sets or decision trees with arbitrary risk thresholds (in which a 

single criterion determines the outcome) (Hayes 1997, Keller et al. 2007b). Issues of objectivity and 

consistency in professional opinions can arise in qualitative assessments (Burgman et al. 1999, but see use 

of structured expert judgment in Wittmann et al. 2014). As such, quantitative approaches are often 

favored despite their sensitivity to weighting schemes (e.g., Pheloung et al. 1999) and dependence on 

complete data sets, which rarely occur (Campbell 2009). Thus, there is a tradeoff between qualitative 

approaches (often easier to complete, albeit with potentially less supportable results) and quantitative 

approaches (may be impossible to complete given available data, but are viewed as preferable). 

Extensive work has been conducted on pathway- (e.g., USACE 2011), vector- (e.g., Colautti et al. 2003), 

and taxon-specific (e.g., Mendoza-Alfaro et al. 2009) assessments, particularly relating to ballast 

introductions (e.g., Grigorovich et al. 2003), but very few of these efforts have considered live trade (but 

see Keller and Lodge 2007; Marson et al. 2009; Rixon et al. 2005) or recreational boating (e.g., 

Rothlisburger et al. 2010). Moreover, multi-vector assessments are rare and have been focused on 

ecological and economic impacts of established Great Lakes AIS (e.g., Keller et al. 2009) or on 

vector/pathway analysis alone (e.g., Kelly 2007) rather than forecasting the likelihood of introduction, 

spread, or consequence for new invaders to the system. Where assessments of existing and high risk AIS 

do exist, there has been a further scarcity of information, resulting in the inability to predict likelihood 

and consequence for those species (e.g., NOAA 2012, ‘current research is inadequate to support proper 

assessment;’ USEPA 2008, ‘NEK’ not enough known).
3

2. METHODS

2.1 Overview of Risk Assessment Structure

We employed an assessment framework for aquatic nonindigenous species that addressed several of the 

limitations discussed above. In particular, our semi-quantitative framework aimed to compare multiple 

taxa and pathways, to consider the full invasion process from introduction to impact, account for the 

breadth of possible impacts, and gauge uncertainty with each assessment. This was targeted at providing 

information needed to develop comprehensive policies that are not limited to isolated groups of organisms 

or pathways of introduction. It was also designed to allow managers to make more informed decisions 

about which pathways to monitor with greater effort, relative to threats organisms in those pathways may 

pose. It is hoped that managers will be able to adopt precautions with respect to their tolerance of risk 

concerning the likelihood of species establishment and impact. Additionally, our framework was 

constructed to be adaptable and easily amendable as more information about species or pathways 

becomes available.

This invasive species assessment framework consisted of three qualitative, question-driven assessments 

for which we relied on thorough Internet and literature searches, as well as expert judgment, to score and 

rank species’ potential for introduction, establishment, and impact. These assessment tools were modeled 

after the United Kingdom Non-Native Organism Risk Assessment scheme (Baker et al. 2008) with 

adaptations for freshwater species. This is a question-based, semiquantitative designed to work across 

diverse taxa based on ‘readily available’ information specific to the receiving system and about the 

particular species in a logical framework following established risk analysis procedures. This model was 

selected because it was one of the most comprehensive and straightforward models that could be applied 

broadly across taxa as well as being particularly transparent in that every individual score is justified with 

a written comment. This framework allows for the addition of additional assessments (questions or entire 

sections) should releavant information (e.g., climate or habitat suitability) become available either at the 

cross-taxa scale or for particular species. The three assessments of our analysis were Introduction, 

Establishment and Impact. 

We first considered a species presence and likelihood of delivery via each of six major vectors. Based on 

ecological and habitat characteristics, we then assessed its potential to become established and 

overwinter. Lastly, we predicted its potential for environmental and socio-economic impacts, and 

beneficial effects. For each sub-assessment, we binned semi-quantitative scores into categories of low, 

moderate, high, or unknown—the latter based on being unable to assess based on information availability. 

By ranking these relative scores, this system provided a method of identifying and comparing impacts 

across taxa and type of impact.

The Potential for Introduction assessment sought to identify all possible vectors of introduction and a 

species’ proximity (or ease of introduction) to pathways into the Great Lakes. This assessment considers 

paired questions for each of six vectors. The Potential for Establishment assessment consisted of 18 

questions evaluating characteristics of potential invaders, such as biological and ecological attributes, 

environmental compatibility, propagule pressure, and history of invasion and spread. The Potential for 

Impact assessment separately considers the harmful environmental and socioeconomic impacts, as well as 

beneficial effects of these species’ invasions elsewhere around the world, with six questions for each 

impact type.

2.2 Potential for Introduction
4

Species introduction assessment criteria and relative levels of introduction likelihood within each vector 

were developed based on a literature review of vectors of aquatic species introduction. It incorporated 

vectors identified by Kelly (2007, modified from Holeck et al. 2004) in a Great Lakes vector assignment 

protocol. Vectors not present in that protocol were obtained from the United States Geological Survey’s 

(USGS) Nonindigenous Aquatic Species (NAS) database’s standardized list of vectors (USGS 2011). 

These include the following vectors: canals and waterways (dispersal), trade of live organisms 

(stocking/planting/escape from recreational culture, release, escape from commercial culture), activities 

of recreational and resource users (hitchhiking/fouling), and commercial shipping (transoceanic shipping). 

In this assessment, we separated live trade into three vectors according to the distinct nature of practices 

and regulations surrounding each (e.g., water gardening practices vs. commercial culture). Assessment 

criteria and relative levels of introduction likelihood within each vector are based upon the results of a 

literature review. The tool was structured according to the United Kingdom Non-Native Organism Risk 

Assessment scheme (Baker et al. 2008) with adaptations for the Great Lakes.

The potential for introduction assessment took into account a “proximity” proxy for each pathway using a 

suite of 12 paired questions (two per vector). The first question in a pair considered potential pathways for 

introduction, assigning a score from 0 to 100—usually 100 for being in a particular pathway and 0 for 

not—while the second question evaluated the likelihood of a species to enter the Great Lakes through that 

pathway, using a multiplicative factor from 0 to 1. If a question could not be answered based on available 

data, an “unknown” option was available.

 Dispersal – (a) Does this species occur near waters (natural or artificial) connected to the Great 

Lakes basin? (b) What is the proximity of this species to the Great Lakes basin?

 Hitchhiking/Fouling - (a) Is this species likely to attach to or be otherwise transported by, or 

along with, recreational gear, boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., 

aquatic plants), or other objects (e.g., packing materials), including as parasites or pathogens, 

entering the Great Lakes basin? (b) What is the proximity of this species to the Great Lakes 

basin?

 Unauthorized intentional release – (a) Is this species sold at aquarium/pet/garden stores (“brick & 

mortar” or online), catalogs, biological supply companies, or live markets (e.g., purchased for 

human consumption, bait, ornamental, ethical, educational, or cultural reasons) and as a result 

may be released into the Great Lakes basin? (b) How easily is this species obtained within the 

Great Lakes region (states/provinces)?

 Stocking/Planting/Escape from Recreational Culture – (a) Is this species being stocked/planted to 

natural waters or outdoor water gardens around the Great Lakes region? (b) What is the nature 

and proximity of this activity to the Great Lakes basin?

 Escape from Commercial Culture – (a) Is this species known to be commercially cultured in or 

transported through the Great Lakes region? (b) What is the nature and proximity of this activity 

to the Great Lakes basin?

 Shipping – (a) Is this species likely to be taken up in ballast, and capable of surviving adverse 

environments (i.e. extreme temperatures, absence of light, low oxygen levels) and partial-tocomplete ballast water exchange/flushing (e.g., is euryhaline, buries in sediment, produces 

resistant resting stages, has other attributes or behaviors facilitating survival under these 

conditions)? (b) Does this species occur in waters from which shipping traffic to the Great Lakes 

originates?
5

A score sheet was kept for tallying the results for each species. 

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Figure 1: Score sheet for probability of introduction assessment. Example scored to maximum.

Overall probability for introduction per vector (High, Moderate, Low) was determined by the adjusted 

point score for the species in that vector. Thresholds for introduction probability were set such that 

species in the closest proximity to the Great Lakes (relative to the pathway of introduction) would be 

evaluated as having High probability, those at intermediate distances would be evaluated as having 

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 1 100 High

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x 1 100 High

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 1 100 High

Total Unknowns (U) 0 Confidence Level High
6

Moderate probability, and those either not in the pathway or at the furthest distance would be evaluated as 

having Low probability. Summary tables provide scores summed across vectors – e.g., a species which 

scores 75 (moderate) on each of two vectors has a total score of 125 and was considered to have a high 

overall probability of introduction. Although summation in this fashion led to a possible maximum score 

of 600, this was possible only if a species were to be present and in high proximity in all six vectors 

simultaneously. Scores exceeding 100 were actually quite rare. The highest score actually produced in 

our species set was 450 (for Eichhornia crassipes which is present in 5 of the 6 vectors).

Assessment confidence levels were assigned for each species assessment by taking into consideration the 

total number of questions which could not be evaluated based on available scientific literature. 

Confidence is deemed to be High if there are no unknowns, Moderate if there were unknowns for onethird or fewer of the vectors, Low if there were unknowns for more than one third of the vectors, and 

Very Low if there were unknowns for all but one vector. Overall for the 67 species assessed, only 19 of 

the 804 questions (2%) could not be answered. Confidence was high in the assessments for most species 

with no questions unanswered. Only one species (Egeria densa) was assessed with low confidence, and 

only 10 (15%) at moderate confidence (one question unanswered). 

2.3 Potential for Establishment

The establishment assessment was developed based on a literature review of variables that aid or detract 

from an invader’s establishment success and spread potential, as relevant to the Great Lakes. Contributing 

variables were broadly grouped into a total of 18 questions within four categories: invasive 

biological/ecological attributes (environmental tolerance, overwintering, diet, competitive ability, 

fecundity, reproductive mode), environmental compatibility (climate, water quality, habitat, climate 

change, food availability, interspecific dependence/facilitation/inhibition), propagule pressure (inoculum 

size, frequency), and history of invasion and spread (extent, rate of spread, prevention). Again, this 

assessment tool was modeled after the United Kingdom Non-Native Organism Risk Assessment scheme 

(Baker et al. 2008) and adapted for the Great Lakes. While important to successful establishment/spread, 

initially proposed questions concerning genetic diversity of potential source population, genetic and 

phenotypic variation, and likelihood of introduction during time of year appropriate for establishment 

were deemed unlikely to be able to answer a priori for most species; these questions were therefore 

removed from the assessment.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

 How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described? (0-9)

 How likely is it that any life stage of this species can overwinter in the Great Lakes (survive 

extremely low levels of oxygen, light, and temperature)? (0-9)

 If this species is a heterotroph, how would the flexibility of its diet be described? (0-9)

 How likely is this species to outcompete species in the Great Lakes for available resources? (0-9)

 How would the fecundity of this species be described relative to other species in the same 

taxonomic class? (0-9)

 How likely are this species’ reproductive strategy and habits to aid establishment in new 

environments, particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self-fertilization, 

vegetative fragmentation)? (0-9)

ENVIRONMENTAL COMPATIBILITY

 How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the 

native and introduced ranges of this species to those in the Great Lakes region? (0-9) 
7

 How similar are other abiotic factors that are relevant to the establishment success of this species 

(e.g., pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and 

introduced ranges to those in the Great Lakes? (0-9)

 How abundant are habitats suitable for the survival, development, and reproduction of this 

species in the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, 

oxygen)? (0-9)

 How likely is this species to adapt to or to benefit from the predicted effects of climate change on 

the Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice 

cover, altered streamflow patterns, increased salinization)? (0-9)

 How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)? (0-9)

 Does this species require another species for critical stages in its life cycle such as growth (e.g., 

root symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or 

transmission (e.g., vectors)? (0-9 OR -80% if critical species not present in GL and not likely to 

be introduced)

 How likely is the establishment of this species to be aided by the establishment and spread of 

another species already in the Great Lakes? (0-9)

 How likely is establishment of this species to be prevented by the herbivory, predation, or 

parasitism of a natural enemy this is already present in the Great Lakes and may preferentially 

target this species? (zero to -80%)

PROPAGULE PRESSURE

 On average, how large and frequent are inoculations (introduction events) from the potential 

vectors identified in Section A for this species? (What is the total number of individuals 

introduced?) (0-9)

HISTORY OF INVASION AND SPREAD

 How extensively has this species established reproducing populations in areas outside its native 

range as a direct or indirect result of human activities? (0-9)

 How rapidly has this species spread by natural means or by human activities once introduced to 

other locations? (0-9)

 Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species? (zero to -90%)

Overall species’ establishment potential was determined by its total point score. Answers to three of the 

18 questions could lead to an overall percentage reduction in a species’ score. Such adjustments were

warranted when a variable would counter or prevent the species’ establishment; these included lack of a 

critical species (e.g., host), presence of a natural enemy, and implementation of control measures. 

Species could score a High establishment potential if at least three-quarters of the questions were scored 

as 9s or a Moderate establishment potential if more than half of the questions were scored as 6s (or were 

evenly split with equivalent numbers of 3s and 9s); otherwise the species was ranked as having a Low 

establishment potential.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 144

>100 High Adjustments

B. Critical species A*(1- 0%) 144
8

51-99 Moderate C. Natural enemy B*(1- 0%) 144

Control measures C*(1- 0%) 144

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Figure 2: Score sheet for the probability for establishment. Example scored to maximum.

The assessment did not weight all 4 categories equally; biological attributes were assessed based on 6 

questions with a maximum of 54 points, environmental compatibility based on 8 questions with a 

maximum of 63 points, propagule pressure based on 1 question worth 9 points and history of invasion and 

spread based on 3 questions with a maximum of 18 points. 

Confidence levels were assigned by taking into consideration the number of questions that could not be 

evaluated based on available scientific literature. Confidence in the assessment for each species was 

deemed High if one or fewer questions could not be answered, Moderate if fewer than one third of the 

questions could not be answered, Low if more than one third of the questions could not be answered, and 

Very Low if more than half of the questions could not be answered. Among the 67 species assessed, 97 

of the 1206 questions (8%) could not be answered. Four invertebrate species assessed at low confidence 

(Ectinosoma abrau, Paraleptastacus spinicaudus triseta, Sinelobus stanfordi, and Leyogonimus polyoon) 

accounted for 28 of these unanswered questions. Lack of knowledge of propagule pressure accounted for 

39 of the unanswered questions. 

2.4 Potential for Impact

The potential for impact assessment was modeled after a tool used to assess the realized consequences of 

nonindigenous species already established in the Great Lakes (Sturtevant et al. 2014). It examines 

potential adverse environmental and socioeconomic impacts (including human health), as well as 

potential beneficial effects. 

Modifications to Organism Impact Assessment used for established species included:

 Addition of “Potential” impact

 Addition of impact consideration “from any non-native region”

 Revised and standardized use of “added pressure to threatened/endangered species” for high 

impact categories in biological/environmental effects in order to capture that any adverse effects 

against endangered species are significant/high impact, while a more extreme effect against a 

native species would be needed to consider it as being significant/high.

 Deletion of “AND/OR” significant effects “ in past invasions outside of the Great Lakes” clauses 

because we are only considering invasions outside of the Great Lakes
9

 Revised qualitative statements to “has the potential for __ impact if introduced to the Great 

Lakes”

This assessment is divided into sets of six questions within each these three impact categories: 

environmental impact (toxicity/facilitation of parasitism or viral/bacterial infections, competition, trophic 

alteration, genetic effects, degradation of water quality, degradation of physical habitat); socioeconomic 

impact (human health, infrastructural damage, degradation of water quality related to human use, harm to 

economic sectors, harm to recreational potential, diminishment of aesthetic quality); and beneficial effect 

(use for biocontrol, commercial value, recreational value, medicinal/scientific value, improvement to 

water quality, other ecological services).

POTENTIAL ENVIRONMENTAL IMPACT

 Does the species pose some hazard or threat to the health of native species (e.g., it magnifies 

toxin levels; is poisonous; is a pathogen, parasite, or a vector of either)?

 Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

 Does it alter predator-prey relationships? 

 Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

 Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, 

oxygen, or other chemical levels/cycles)?

 Does it alter physical components of the ecosystem in some way (e.g., facilitated 

erosion/siltation, altered hydrology, altered macrophyte/phytoplankton communities, physical or 

chemical changes to substrate)?

POTENTIAL SOCIO-ECONOMIC IMPACT

 Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

 Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

 Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

 Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, 

aquaculture, agriculture)?

 Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water 

closures, equipment damage, decline of recreational species)?

 Does it diminish the perceived aesthetic or natural value of the areas it inhabits? 

POTENTIAL BENEFICIAL EFFECT

 Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms? 

 Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

 Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)? 

 Does the species have some medicinal or research value (i.e. outside of research geared towards 

its control)?

 Does the species remove toxins or pollutants from the water or otherwise increase water quality? 

 Does the species have a positive ecological impact outside of biological control (e.g., increases 

the growth or reproduction rates of other species, fills an important gap in the food web, supports 

the survival of a species that is threatened, endangered species, or commercially valuable)? 
10

Scores for each criterion (0, 1, or 6) were summed per impact category (36 point maximum) and 

converted to an overall impact ranking using an established scoring table that accounts for level of 

uncertainty in the assessment (i.e. number of unknowns, see Figure 3).

Environmental Impact Total 36

Total Unknowns (U) 0

Socio-Economic Impact Total 36

Total Unknowns (U) 0

Beneficial Effect Total 36

Total Unknowns (U) 0

Scoring for EACH Subassessment

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

Figure 3: Score sheet of impact potential results. Sample scored as maximum impact.

Rather than employing a ‘confidence’ metric as with the previous two assessments, the assessment of 

potential impact followed the protocol of our earlier assessment of impact for established species in 

folding this into the risk score such that any subassessment with a score of 0 but more than two

unanswered questions is itself considered ‘unknown’ as is any subassessment with a score of 1 and more 

than one unknown – effectively no confidence in the result. Because the effect of unanswered questions 

may only result in a lower score (unanswered questions can only increase score), those subassessments 

scoring moderate to high with significant unknowns should be considered ‘at least’ moderate or ‘at least’ 

high. Across the sixty-seven species (1206 total questions), a total of 189 (16%) were unable to be 

answered based on literature review. Environmental impact was assessed as unknown for 26 of the 67 

species (39%), socioeconomic impact was assessed as unknown for five species (7%) and the benefits 

were assessed as unknown for one species (1.5%). These percentages are comparable to the state of 

knowledge for established species – fully 49% of the established species scored with unknown 

environmental impacts, 7% with unknown socioeconomic impacts and 8% with unknown benefits 

(Sturtevant 2014).
11

2.5 Application to Great Lakes Watchlist Species

We applied our assessment framework to 67 species identified as fitting the following criteria:

Geographic criterion: Lives in a known donor region (e.g., rivers adjacent to Great Lakes, inland 

lakes in the Great Lakes region, western Europe, the Ponto-Caspian region) or in a zone with high 

specialization, species pool, or climate conditions that match the Great Lakes.

Aquatic criterion: USDA wetland indicator status was used as a guideline for determining 

whether wetland plants should be included in the list obligate (OBL), facultative wetland (FACW), 

and facultative (FAC) plants were included in this list as aquatic; facultative upland (FACU) and 

upland (UPL) plants were not. Waterfowl, reptiles, and mammals spending significant time in and 

dependent on the water were not included.

Established criterion: NOT already established in the Great Lakes, but assessed as ‘likely’ to 

become so by identification in one or more peer-reviewed scientific publications as having high 

probability for survival, establishment, and/or spread if introduced to the Great Lakes OR meeting 

at least three of the following five criteria:

1. A transport vector currently exists that could move the species into the Great Lakes

2. The species is likely to tolerate/survive transport (including in resting stages) in the identified 

vector

3. The species has a probability of being introduced multiple times or in large numbers

4. The species is likely to be able to successfully reproduce in the Great Lakes

5. The species has been known to invade other areas

The potential warming of the Great Lakes due to climate change was an important factor to consider in 

light of potential future invaders. The GLANSIS watchlist includes a few species for which predicted 

increases in water temperature have led to explicit remarks concerning future invasion probability. 

Otherwise, species which may be introduced but are not likely to overwinter given the current 

temperature regime were excluded from this list of high probability invaders.

By ranking each species’ potential 1) for introduction via any of six major vectors; 2) to become 

established and overwinter; and 3) for environmental impact, socio-economic impact, and beneficial

effect, this framework provided a comprehensive and consistent method of identifying and comparing 

impacts across taxonomic groups, pathways, and impact categories. It was our intent that this multi-taxa, 

multi-vector approach will guide prioritization by managers in monitoring and response programs. The 

draft species list was circulated among regional and taxonomic experts to identify species which should 

be added or removed from the list based on more recent information and/or expert opinion. 

After species selection, we completed the introduction, establishment, and impact assessment

components for each species. We first considered a species’ presence in and likelihood of delivery via 

each of six major vectors. Based on ecological and habitat characteristics, we then assessed its potential to 

become established and overwinter. Lastly, we predicted its potential for environmental and socioeconomic impacts, and beneficial effects. The assessments were completed using an exhaustive literature 

review that included online species registries, aquatic invasive species databases, major bibliographic 

databases, peer-reviewed literature, published state and federal agency reports, reliable Internet sources 

on a variety of search terms, librarian services, expert consultation, and best professional judgment. We 
12

summarized our justification for each question’s score and documented the information’s source. Review 

was deemed sufficient after such searches exhausted novel sources of information. We sent completed 

assessments for expert review, with the instructions to evaluate its accuracy and supplement with 

additional information, if needed.

The 67 species assessed include 27 fishes, 32 invertebrates and 8 plants. As the initial list was based on 

the peer-reviewed literature, the composition of taxa in this list may reflect biases of the studies rather 

than a true reflection of the types of taxa likely to invade. For example, no studies were found which 

assessed the potential for aquatic insects to invade the Great Lakes.

We compared species’ raw assessment scores and semi-quantitative ranking for introduction, 

establishment, and impact to determine trends in predicted invasiveness. In particular, we considered

taxa, geographic origins, vectors, Great Lakes establishment, and impacts. 

3. RESULTS

3.1 Framework

The framework development yielded three separate semi-quantitative, question-driven assessment 

components for a species’ potential introduction (six pairs of questions), establishment (18 questions 

total), and impact (six questions for each of three broad categories). The final structure of each assessment 

component, based on the considerations described in the Methods above, is summarized below.

Potential for Introduction

Vectors in the introduction assessment component included 1) canals and waterways (dispersal), 2) 

activities of recreational and resource users (hitchhiking/fouling), 3) unauthorized deliberate release, 4) 

stocking/planting/escape from recreational culture, 5) escape from commercial culture and 6) commercial 

shipping (transoceanic shipping). 

In general, available data was sufficient to complete the assessment. Only 19 questions in total could not 

be answered in the entire assessment (an average of 0.28 questions per species) giving a high overall 

confidence level. Available data for plants was somewhat lower quality – over half of the missed 

questions were in regard to plant species (averaging 1.25 questions per plant species). 

Table 1: Probability of introduction of fishes to the Great Lakes basin.

Species

DispersalHitchhiking or FoulingUnauthorized ReleaseStocking, Planting, or Escape Recreation al CultureEscape Commercial CultureTransoceanic ShippingOverallUnknowns and Confidence

Alburnus alburnus 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High
13

Atherina boyeri 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Babko 

gymnotrachelus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Benthophilus 

stellatus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

8

Low

8

Low

0

High

Carassius 

carassius

0

Unlikely

0

Unlikely

10

Low

0

Unlikely

0

Unlikely

0

Unlikely

10

Low

0

High

Channa argus 25

Low

0

Unlikely

50

Moderate Unknown

0

Unlikely

0

Unlikely

75

Moderate

1

Moderate

Clupeonella 

cultriventris

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

8

Low

8

Low

0

High

Cottus gobio 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Ctenopharyngodo

n idella

100

High

0

Unlikely

50

Moderate

75

Moderate

25

Low

0

Unlikely

250

High

0

High

Cyprinella 

whipplei

75

Moderate

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

75

Moderate

0

High

Hypophthalmichth

ys molitrix

75

Moderate

0

Unlikely

50

Moderate

0

Unlikely

50

Moderate

0

Unlikely

175

High

0

High

Hypophthalmichth

ys nobilis

75

Moderate

0

Unlikely

50

Moderate

25

Low

50

Moderate

0

Unlikely

200

High

0

High

Ictalurus furcatus 25

Low

0

Low

10

Low

100

High

0

Low

0

Low

135

High

0

High

Knipowitschia 

caucasica

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Leuciscus idus

Unknown

0

Unlikely

100

High

100

High

0

Unlikely

0

Unlikely

200

High

2

Moderate
14

Leuciscus 

leuciscus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Neogobius 

fluviatilis

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Oncorhynchus 

keta

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

High

Osmerus 

eperlanus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Perca fluviatilis 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Perccottus glenii 0

Unlikely

0

Unlikely

10

Low

0

Unlikely

0

Unlikely

40

Moderate

50

Moderate

0

High

Phoxinus phoxinus 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Pseudorasbora 

parva

0

Unlikely

10

Low Unknow

n

0

Unlikely

0

Unlikely

0

Unlikely

10

Low

2

Moderate

Rutilus rutilus 0

Unlikely

0

Unlikely

10

Low

0

Unlikely

0

Unlikely

80

Moderate

90

High

0

High

Sander lucioperca 25

Low

10

Low

0

Unlikely Unknown

0

Unlikely

0

Unlikely

35

Low

1

Moderate

Silurus glanis 0

Unlikely

0

Unlikely Unknow

n

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

2

Moderate

Syngnathus 

abaster

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

50

Moderate

0

High
15

Table 2: Probability of introduction for invertebrates to the Great Lakes basin.

Species

DispersalHitchhiking or FoulingUnauthorized ReleaseStocking, Planting, or Escape Recreation al CultureEscape Commercial CultureTransoceanic ShippingOverallUnknowns andConfidence

Limnoperna fortunei 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

8

Low

8

Low

0

High

Monodacna 

colorata

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Fredericella sultana 0

Unlikely

10

Low

0

Unlikely

0

Unlikely

0

Unlikely

100

High

110

High

0

High

Apocorophium 

lacustre

50

Moderate

50

Moderate

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

150

High

0

High

Chelicorophium 

curvispinum

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Dikerogammarus 

haemobaphes

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Dikerogammarus 

villosus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Echinogammarus 

warpachowskyi

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Obesogammarus 

crassus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Obesogammarus 

obesus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

10

Low

10

Low

0

High
16

Pontogammarus 

robustoides

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Cornigerius 

maeoticus maeoticus

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Daphnia cristata 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

80

High

80

High

0

High

Podonevadne 

trigona ovum

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

8

Low

8

Low

0

High

Calanipeda 

aquaedulis

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Cyclops kolensis 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Ectinosoma abrau 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

8

Low

8

Low

0

High

Heterocope 

appendiculata

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Heterocope caspia 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Paraleptastacus 

spinicaudus triseta

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Limnomysis 

benedeni

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Paramysis 

(Mesomysis) 

intermedia

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Paramysis 

(Metamysis) ullskyi

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Paramysis 

(Serrapalpisis) 

lacustris

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High
17

Cherax destructor 0

Unlikely

0

Unlikely

50

Moderate

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

0

High

Rhithropanopeus 

harrisii

0

Unlikely

10

Low

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

60

Moderate

0

High

Sinelobus stanfordi 0

Unlikely

10

Low

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

60

Moderate

0

High

Leyogonimus 

polyoon

0

Unlikely

50

Moderate

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

50

Moderate

1

Moderate

Hypania invalida 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

40

Moderate

40

Moderate

0

High

Brachionus leydigii 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

80

High

80

High

0

High

Filinia cornuta 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

80

High

80

High

0

High

Filinia passa 0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

80

High

80

High

0

High

Table 3: Probability of introduction of plants to the Great Lakes basin.

Species

DispersalHitchhiking or FoulingUnauthorized ReleaseStocking, Planting, or Escape Recreation al CultureEscape Commercial CultureTransoceanic ShippingOverallUnknowns and Confidence

Crassula 

helmsii

0

Unlikely

0

Unlikely Unknown

0

Unlikely

0

Unlikely

0

Unlikely

0

Unlikely

2

Moderate

Egeria densa

Unknown

50

Moderate

100

High

25

Low Unknown

0

Unlikely

175

High

3

Low

Eichhornia 

crassipes

100

High

100

High

100

High

75

Moderate

75

Moderate

0

Unlikely

450

High

0

High
18

Of the assessed species, two fishes (Oncorhynchus keta and Silurus glanis) and one plant (Crassula 

helmsii) were found unlikely to be introduced to the Great Lakes. Six fishes (Ctenopharyngodon idella, 

Hypopthalmichthys molitrix, Hypopthalmichthys nobilis, Ictalurus furcatus, Leuciscus idus, Rutilus 

rutilus), and six invertebrates (Fredericella sultana, Apocorophium lacustre, Daphnia cristata, 

Brachionus leydigii, Filinia cornuta, Filinia passa) and six plants (Egeria densa, Eichhornia crassipes, 

Hydrilla verticillata, Myriophyllum aquaticum, Pistia stratiotes, Stratiotes aloides) were found to be 

highly likely to be introduced to the Great Lakes. Of these, the three rotifer species and the Daphnia were 

considered a risk solely due to the ballast water vector while all the other high risk species were a risk in 

multiple vectors. 

Thirty-five species of fishes and invertebrates (but no plants) were found to be a low to moderate risk due 

solely to the ballast water vector. The high prevalence of ballast-mediated invaders on this list (67% of 

the species listed attribute some risk due to ballast) likely reflects the large number of studies that have 

been conducted with respect to potential ballast-mediated invasion. Changes in regulation of ballast water 

for the Great Lakes region over the past 20 years may be responsible for our lower assessment of the risk 

of these species (with regard to introduction) relative to the orginal assessments in the peer-reviewed 

literature which led to their selection for inclusion in our analysis.

Species with a high potential for introduction originated from each of the included geographic regions, 

including all of the species from South America (see Figure 4). All vectors except ‘escape from 

commercial culture’ were evenly represented among those with a high potential for introduction, but the 

shipping vector was disproportionally responsible (50%) for the species with significant (high + 

moderate) potential for introduction (see Figure 5). 

Of the species assessed, fishes were present in all vectors with at least some potential for introduction, 

while plants were present in all except for the shipping vector. Nine fishes (33%) were present in more 

than one vector, with the ide (Leuciscus leuciscus) having a high potential of introduction through both 

unauthorized intentional release and stocking/planting/escape from recreational culture. The bulk of 

crustaceans (83%) were assessed as having a high or moderate potential to be introduced via shipping. 

Seven plants (88%) were present in multiple vectors; this included water hyacinth (Eichhornia crassipes), 

which was present in all except the shipping vector. Water lettuce (Pistia stratiotes) was ranked as having 

Hydrilla 

verticillata

100

High

100

High

10

Low Unknown Unknown

0

Unlikely

300

High

2

Moderate

Hygrophila 

polysperma

0

Unlikely

10

Low

50

Moderate

0

Unlikely

0

Unlikely

0

Unlikely

60

Moderate

0

High

Myriophyllum 

aquaticum

100

High

100

High

100

High

75

Moderate Unknown

0

Unlikely

375

High

1

Moderate

Pistia 

stratiotes

100

High

100

High

100

High

100

High Unknown

0

Unlikely

400

High

2

Moderate

Stratiotes 

aloides

100

High

100

High

10

Low

100

High

0

Unlikely

0

Unlikely

310

High

0

High
19

a high potential for introduction in four vectors (dispersal, hitchhiking/fouling, unauthorized intentional 

release, and stocking/planting/escape from recreational culture).

Considering the highest level of introduction potential for taxa across all vectors, high introduction 

potential was most prevalent among rotifers 3 of 3, bryozoans 1 of 1, and plants 6 of 8. Fishes 17 of 27 

(63%), annelids 1 of 1, platyhelminthes 1 of 1, and crustaceans 20 of 24 (83%) most often ranked as 

having a moderate introduction potential. Mollusks (n=2) were evenly split between moderate and low 

introduction potential. Only three of the 67 species assessed (4%) were found unlikely to be introduced to 

the Great Lakes via any vector. 

Figure 4: Likelihood of introduction of species by continent of origin. 

0

5

10

15

20

25

30

35

40

45

50

Number of Species

Continent of Origin

Unlikely Low Moderate High
20

Figure 5: Likelihood of introduction of species by vector. The shipping vector was disproportionally responsible 

(50%) for the species with significant (high + moderate) potential for introduction to the Great Lakes basin.

Potential for Establishment

In the establishment assessment component, contributing variables were broadly grouped into a total of 

18 questions within four categories: invasive biological/ecological attributes (environmental tolerance, 

overwintering, diet, competitive ability, fecundity, reproductive mode), environmental compatibility 

(climate, water quality, habitat, climate change, food availability, interspecific 

dependence/facilitation/inhibition), propagule pressure (inoculum size, frequency), and history of 

invasion and spread (extent, rate of spread, prevention). While important to successful 

establishment/spread, initially proposed questions concerning genetic diversity of potential source 

population, genetic and phenotypic variation, and likelihood of introduction during time of year 

appropriate for establishment, were deemed unlikely to be able to answer a priori for most species and 

removed from this assessment component. One question relating to propagule pressure was retained in the 

assessment; however, this question could not be answered for 39 of the 67 species (58%). Only an 

additional 48 questions (<5%) could not be answered with these being spread more evenly across the 

question types. In general, data was sufficient to complete the assessment. Confidence in the assessment 

was low for only four invertebrate species (Ectinosoma abrau, Paraleptastacus spinicaudus triseta, 

Sinelobus stanfordi, and Leyogonimus polyoon). 

Overall species’ establishment potential was determined by its total point score. Three questions included 

an adjustment factor that led to an overall reduction in a species’ score. Such adjustments were warranted 

when a variable would counter or prevent the species’ establishment. For example, if a critical prey 

species is not present in the Great Lakes, that reduces the likelihood of the species becoming established, 

0

10

20

30

40

50

60

70

80

Number of Species

Vector

Unlikely Low Moderate High Unknown
21

even if all other factors would support its establishment. The categorical probability of introduction for 

each vector (High, Moderate, Low) was determined by the quantitative score. 

Table 4: Probability of establishment for fishes in the Great Lakes basin. NE= Natural Enemy present in Great 

Lakes. C = Control measures in place in the Great Lakes.

Species Invasive 

Biological 

or 

Ecological 

Attributes

Environmental 

Compatibility

Propagule 

Pressure

History 

of 

Invasion

Adjustment Overall # 

Unknowns

& 

Confidence

Alburnus alburnus 39 50 Unknown 13 102

High

1

High

Atherina boyeri 32 51 Unknown 11 94

Moderate

2

Moderate

Babko 

gymnotrachelus

40 53 Unknown 14 107

High

3

Moderate

Benthophilus 

stellatus

28 42 Unknown 10 -20% NE 64

Moderate

1

High

Carassius carassius 31 49 0 9 -10%NE 80

Moderate

0

High

Channa argus 48 35 Unknown 13 96

Moderate

2

Moderate

Clupeonella 

cultriventris

30 44 Unknown 11 -10% NE 77

Moderate

1

High

Cottus gobio 27 36 Unknown 5 -20% NE 54

Moderate

2

Moderate

Ctenopharyngodon 

idella

32 45 4 18 -40% C 59

Moderate

0

High

Cyprinella whipplei 19 45 Unknown 4 -10% NE 61

Moderate

2

Moderate

Hypopthalmichthys 

molitrix

35 47 2 18 -40% C 61

Moderate

0

High
22

Hypophthalmichthys

nobilis

34 47 1 18 -40% C 60

Moderate

0

High

Ictalurus furcatus 33 43 0 10 86

Moderate

0

High

Knipowitschia 

caucasica

25 54 Unknown 7 86

Moderate

2

Moderate

Leuciscus idus 32 41 Unknown 12 85

Moderate

2

Moderate

Leuciscus leuciscus 29 44 Unknown 6 79

Moderate

1

High

Neogobius fluviatilis 35 53 Unknown 13 101

High

1

High

Oncorhynchus keta 33 48 2 3 86

Moderate

0

High

Osmerus eperlanus 39 37 0 2 -20% NE 62

Moderate

0

High

Perca fluviatilis 29 49 Unknown 17 95

Moderate

1

High

Perccottus glenii 40 50 Unknown 18 -5% NE 103

High

1

High

Phoxinus phoxinus 38 49 Unknown 9 -5% NE 91

Moderate

1

High

Pseudorasbora 

parva

39 45 Unknown 18 -10% NE 92

Moderate

1

High

Rutilus rutilus 37 55 Unknown 5 -10% NE 87

Moderate

2

Moderate

Sander lucioperca 45 58 Unknown 13 116

High

1

High
23

Silurus glanis 38 42 0 13 93

Moderate

0

High

Syngnathus abaster 35 42 0 14 -10% NE 82

Moderate

0

High

Table 5: Probability of establishment for invertebrates in the Great Lakes basin. NE= Natural Enemy present in 

Great Lakes. C = Control measures in place in the Great Lakes.

Species Invasive 

Biological 

or 

Ecological 

Attributes

Environmental 

Compatibility

Propagule 

Pressure

History 

of 

Invasion

Adjustment Overall # 

Unknowns

& 

Confidence

Limnoperna 

fortunei

40 56 0 13 109

High

0

High

Monodacna 

colorata

27 46 Unknown 13 86

Moderate

3

Moderate

Fredericella 

sultana 

36 48 0 0 84

Moderate

3

Moderate

Apocorophium 

lacustre

30 59 2 12 103

High

1

High

Chelicorophium 

curvispinum

42 45 Unknown 16 103

High

2

Moderate

Dikerogammarus 

haemobaphes

41 58 Unknown 16 115

High

2

Moderate

Dikerogammarus 

villosus

48 57 Unknown 16 121

High

1

High

Echinogammarus

warpachowskyi

35 48 Unknown 10 93

Moderate

1

High

Obesogammarus 

crassus

43 52 Unknown 13 108

High

3

Moderate

Obesogammarus 

obesus

40 57 2 15 -10%NE 103

High

1

High
24

Pontogammarus 

robustoides

49 51 Unknown 17 117

High

2

Moderate

Cornigerius 

maeoticus

maeoticus

36 49 1 14 -30%NE 70

Moderate

0

High

Daphnia cristata 29 41 1 8 -10%NE 71

Moderate

0

High

Podonevadne 

trigona ovum

34 50 Unknown 14 -10%NE 88

Moderate

2

Moderate

Calanipeda 

aquaedulis

37 47 2 11 -10%NE 87

Moderate

1

High

Cyclops kolensis 26 43 2 5 -10%NE 68

Moderate

0

High

Ectinosoma abrau 17 25 Unknown 0 42

Low

8

Low

Heterocope 

appendiculata

20 41 Unknown 9 70

Moderate

4

Moderate

Heterocope caspia 25 50 Unknown 12 87

Moderate

3

Moderate

Paraleptastacus 

spinicaudus triseta

17 25 Unknown 0 42

Low

8

Low

Limnomysis 

benedeni

46 52 Unknown 18 116

High

2

Moderate

Paramysis 

(Mesomysis) 

intermedia

29 47 Unknown 5 81

Moderate

1

High

Paramysis 

(Metamysis) ullskyi

33 48 Unknown 8 89

Moderate

2

Moderate

Paramysis 

(Serrapalpisis) 

lacustris

28 49 Unknown 18 95

Moderate

4

Moderate
25

Cherax destructor 33 47 0 14 -10%NE

-40%C

51

Moderate

0

High

Rhithropanopeus 

harrisii

35 55 0 15 105

High

1

High

Sinelobus stanfordi 20 26 0 4 -10%NE 45

Low

6

Low

Leyogonimus 

polyoon

11 53 Unknown 11 75

Moderate

6

Low

Hypania invalida 41 49 Unknown 12 102

High

1

High

Brachionus leydigii 21 43 3 0 67

Moderate

5

Moderate

Filinia cornuta 17 41 Unknown 7 65

Moderate

5

Moderate

Filinia passa 18 40 3 8 -10%NE 62

Moderate

3

Moderate

Table 6: Probability of establishment for plants in the Great Lakes basin. NE= Natural Enemy present in Great 

Lakes. C = Control measures in place in the Great Lakes.

Species Invasive 

Biological 

or 

Ecological 

Attributes

Environmental 

Compatibility

Propagule 

Pressure

History 

of 

Invasion

Adjustment Overall # 

Unknowns

& 

Confidence

Crassula helmsii 40 41 Unknown 10 91

Moderate

1

High

Egeria densa 34 48 7 18 -10%NE

-30%C

67

Moderate

0

High

Eichhornia 

crassipes

34 44 6 18 -30%C 71

Moderate

0

High

Hydrilla 

verticillata

35 51 3 18 -30%C 75

Moderate

0

High
26

Hygrophila 

polysperma

36 39 2 12 -5%NE 85

Moderate

0

High

Myriophyllum 

aquaticum

25 39 Unknown 14 78

Moderate

2

Moderate

Pistia stratiotes 27 33 7 16 -30%C 58

Moderate

0

High

Stratiotes aloides 34 43 0 7 84

Moderate

0

High

Perhaps unsurprisingly given preselection of the list to be assessed, no species assessed with moderate to 

high confidence were found to have a low probability of establishment in the Great Lakes. Five fishes 

scored over 100 overall (of 144 possible) and were found to have a high probability of establishment of 

the Great Lakes (Alburnus alburnus, Babko gymnotrachelus, Neogobius fluviatilis, Perccottus glenii, and

Sander lucioperca). Eleven invertebrates were also found to have a high probability of establishment 

(Limnoperna fortunei, Apocorophium lacustre, Chelicorophium curvispinum, Dikerogammarus 

haemobaphes, Dikerogammarus villosus, Obesogammarus crassus, Obesogammarus obesus, 

Pontogammarus robustoides, Limnomysis benedeni, Rhithropanopeus harrisii and Hypania invalida). 

The remaining 47 species were assessed as a moderate risk of establishment if introduced. 

Potential for Impact

The impact assessment component was divided into sets of six questions within three potential impact 

categories: environmental impact, socioeconomic impact, and beneficial effect. The numerical values 

corresponding to each score worked in conjunction with the scoring system to ensure that species with 

highly significant impacts for any criterion ranked as a high potential impact species (>5) overall in that 

category. In contrast, moderately significant potential impacts in all six criteria were required to assess a 

species as having a high potential impact. A species could have only been ranked as a low potential 

impact species for a given category if it lacked potential impacts of high significance and demonstrated a 

limited number of moderately significant and unknown impacts for the six criteria. Overall, the full 

assessment could be completed only for 37 species (55%) due to lack of information. Information was 

insufficient to assess the potential environmental impact of 10 fish and 16 invertebrates; the 

socioeconomic impact of three fish and two invertebrates, and the benefits of one fish. 

Table 7: Potential impact of fishes in the Great Lakes basin.

Environmental Socio-economic Benefit Total Unknowns

Alburnus alburnus 14

High

0

Low

7

High

1

Atherina boyeri 2

Moderate

0

Low

6

High

4
27

Babko gymnotrachelus 0

Unknown

1

Low

0

Unknown

8

Benthophilus stellatus 0

Unknown

0

Low

0

Low

5

Carassius carassius 0

Unknown

0

Low

2

Moderate

5

Channa argus 1

Unknown

2

Moderate

2

Moderate

3

Clupeonella cultriventris 0

Unknown

0

Low

1

Low

6

Cottus gobio 0

Unknown

0

Low

0

Low

6

Ctenopharyngodon idella 20

High

1

Low

8

High

1

Cyprinella whipplei 0

Unknown

0

Low

0

Low

6

Hypophthalmichthys 

molitrix

15

High

7

High

4

Moderate

2

Hypophthalmichthys 

nobilis

8

High

12

High

2

Moderate

3

Ictalurus furcatus 2

Moderate

1

Low

14

High

2

Knipowitschia caucasica 0

Unknown

0

Low

0

Low

4

Leuciscus idus 0

Unknown

0

Low

8

High

2

Leuciscus leuciscus 7

High

6

High

2

Moderate

3
28

Neogobius fluviatilis 3

Moderate

0

Low

2

Moderate

0

Oncorhynchus keta 3

Moderate

0

Low

12

High

1

Osmerus eperlanus 7

High

0

Unknown

3

Moderate

3

Perca fluviatilis 18

High

2

Moderate

12

High

2

Perccottus glenii 8

High

1

Low

2

Moderate

4

Phoxinus phoxinus 2

Moderate

1

Low

1

Low

2

Pseudorasbora parva 19

High

1

Unknown

0

Low

1

Rutilus rutilus 11

High

2

Moderate

2

Moderate

1

Sander lucioperca 8

High

0

Unknown

12

High

3

Silurus glanis 6

High

0

Low

8

High

1

Syngnathus abaster 1

Unknown

0

Low

0

Low

5

Table 8: Potential impact of invertebrates in the Great Lakes basin.

Environmental Socio-economic Benefit Total Unknowns

Limnoperna fortunei 30

High

9

High

7

High

0

Monodacna colorata 0

Unknown

0

Low

1

Low

2
29

Fredericella sultana 8

High

12

High

0

Low

3

Apocorophium lacustre 1

Unknown

0

Low

0

Low

4

Chelicorophium 

curvispinum

3

Moderate

0

Unknown

2

Moderate

1

Dikerogammarus 

haemobaphes

1

Unknown

0

Low

1

Low

1

Dikerogammarus 

villosus

7

High

0

Low

1

Low

1

Echinogammarus 

warpachowskyi

2

Moderate

0

Low

2

Moderate

4

Obesogammarus 

crassus

6

High

0

Low

0

Low

1

Obesogammarus 

obesus

8

High

0

Low

0

Low

4

Pontogammarus 

robustoides

4

Moderate

0

Low

2

Moderate

1

Cornigerius maeoticus 

maeoticus

0

Unknown

0

Low

0

Low

2

Daphnia cristata 0

Unknown

0

Low

2

Moderate

2

Podonevadne trigona 

ovum

2

Moderate

0

Low

0

Low

4

Calanipeda aquaedulis 1

Unknown

0

Low

0

Low

3

Cyclops kolensis 1

Unknown

0

Low

0

Low

6
30

Ectinosoma abrau 0

Unknown

0

Low

0

Low

6

Heterocope 

appendiculata

0

Unknown

0

Low

1

Low

6

Heterocope caspia 0

Unknown

0

Low

1

Low

6

Paraleptastacus 

spinicaudus triseta

0

Unknown

0

Low

0

Low

6

Limnomysis benedeni 4

Moderate

0

Low

2

Moderate

0

Paramysis 

(Mesomysis) 

intermedia

0

Unknown

0

Low

0

Low

6

Paramysis (Metamysis) 

ullskyi

7

High

0

Low

1

Low

3

Paramysis 

(Serrapalpisis) 

lacustris

3

Moderate

0

Low

1

Low

1

Cherax destructor 2

Moderate

1

Low

2

Moderate

3

Rhithropanopeus 

harrisii

0

Unknown

1

Low

1

Low

4

Sinelobus stanfordi 0

Low

0

Low

0

Low

1

Leyogonimus polyoon 1

Unknown

0

Unknown

0

Low

3

Hypania invalida 0

Low

0

Low

1

Low

0

Brachionus leydigii 0

Low

0

Low

0

Low

0
31

Filinia cornuta 0

Unknown

0

Low

0

Low

3

Filinia passa 1

Unknown

0

Low

0

Low

5

Table 9: Potential impact of plants in the Great Lakes basin.

Environmental Socio-economic Benefit Total Unknowns

Crassula helmsii 6

High

2

Moderate

0

Low

1

Egeria densa 18

High

25

High

3

Moderate

1

Eichhornia crassipes 15

High

26

High

4

Moderate

1

Hydrilla verticillata 19

High

30

High

5

High

2

Hygrophila 

polysperma

3

Moderate

8

High

3

Moderate

2

Myriophyllum 

aquaticum

18

High

3

Moderate

4

Moderate

5

Pistia stratiotes 14

High

30

High

4

Moderate

0

Stratiotes aloides 3

Moderate

2

Moderate

1

Low

1

Eleven fish species (Alburnus alburnus, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, 

Leuciscus leuciscus, Osmerus eperlanus, Perca fluviatilis, Perccottus glenii, Pseudorasbora parva, 

Rutilus rutilus, Sander lucioperca, and Silurus glanis) were found to have high potential environmental 

and/or socioeconomic impact as were six species of invertebrates (Limnoperna fortunei, Fredericella 

sultana, Dikerogammarus villosus, Obesogammarus crassus, Obesogammarus obesus, and Paramysis 

(Metamysis) ullskyi) and seven species of plants (Crassula helmsii, Egeria densa, Eichhornia crassipes, 

Hydrilla verticillata, Hygrophila polysperma, Myriophyllum aquaticum, and Pistia stratiotes). Ten fish 

species were determined to have a high potential beneficial impact, but only four of these (Atherina 

boyeri, Ictalurus furcatus, Leuciscus idus, and Oncorhynchus keta) did not also have high negative 
32

environmental or socioeconomic impacts. 

An additional 11 species were found to have moderate environmental and/or socioeconomic impacts 

(Channa argus, Neogobius fluviatilis, Phoxinus phoxinus, Chelicorophium curvispinum, 

Echinogammarus warpachowskyi, Pontogammarus robustoides, Podonevadne trigona ovum, Limnomysis 

benedeni, Paramysis (Serrapalpisis) lacustris, Cherax destructor, and Stratiotes aloides) and one species

(Daphnia cristata) had moderate benefits without offsetting high-moderate environmental or 

socioeconomic impacts. 

3.2 Analyses

Overall risk posed by a species to the Great Lakes system was a function of the likelihood that it is 

introduced, the probability of it becoming established if introduced and the potential for it to have serious 

environmental or socioeconomic impacts in the event it does become established.

Table 10: Summary of overall risk for each species.

Species Introduction Establishment Environmental 

Impact

Socioeconomic 

Impact

Benefits

Apocorophium lacustre High High Unknown Low Low

Eichhornia crassipes High Moderate High High Moderate

Pistia stratiotes High Moderate High High Moderate

Hydrilla verticillata High Moderate High High High

Hypophthalmichthys 

nobilis

High Moderate High High Moderate

Hypophthalmichthys 

molitrix

High Moderate High High Moderate

Egeria densa High Moderate High High Moderate

Fredericella sultana High Moderate High High Low

Myriophyllum aquaticum High Moderate High Moderate Moderate

Rutilus rutilus High Moderate High Moderate Moderate

Ctenopharyngodon idella High Moderate High Low High

Stratiotes aloides High Moderate Moderate Moderate Low

Ictalurus furcatus High Moderate Moderate Low High

Leuciscus idus High Moderate Unknown Low High
33

Daphnia cristata High Moderate Unknown Low Moderate

Brachionus leydigii High Moderate Low Low Low

Filinia cornuta High Moderate Low Low Low

Filinia passa High Moderate Low Low Low

Alburnus alburnus Moderate High High Low High

Perccottus glenii Moderate High High Low Moderate

Dikerogammarus 

villosus

Moderate High High Low Low

Obesogammarus crassus Moderate High High Low Low

Chelicorophium 

curvispinum

Moderate High Moderate Low Moderate

Neogobius fluviatilis Moderate High Moderate Low Moderate

Pontogammarus 

robustoides

Moderate High Moderate Low Moderate

Limnomysis benedeni Moderate High Moderate Low Moderate

Dikerogammarus 

haemobaphes

Moderate High Unknown Low Low

Rhithropanopeus harrisii Moderate High Unknown Low Low

Babko gymnotrachelus Moderate High Unknown Low Unknown

Hypania invalida Moderate High Low Low Low

Sander lucioperca Low High High Unknown High

Obesogammarus obesus Low High High Low Low

Leuciscus leuciscus Moderate Moderate High High Moderate

Perca fluviatilis Moderate Moderate High Moderate High

Osmerus eperlanus Moderate Moderate High Unknown Moderate

Paramysis (Metamysis) 

ullskyi

Moderate Moderate High Low Low
34

Hygrophila polysperma Moderate Moderate Moderate High Moderate

Atherina boyeri Moderate Moderate Moderate Low High

Echinogammarus 

warpachowskyi

Moderate Moderate Moderate Low Moderate

Cherax destructor Moderate Moderate Moderate Low Moderate

Paramysis 

(Serrapalpisis) lacustris

Moderate Moderate Moderate Low Low

Phoxinus phoxinus Moderate Moderate Moderate Low Low

Channa argus Moderate Moderate Unknown Moderate Moderate

Cottus gobio Moderate Moderate Unknown Low Low

Cyprinella whipplei Moderate Moderate Unknown Low Low

Knipowitschia caucasica Moderate Moderate Unknown Low Low

Syngnathus abaster Moderate Moderate Unknown Low Low

Monodacna colorata Moderate Moderate Unknown Low Low

Cornigerius maeoticus Moderate Moderate Unknown Low Low

Calanipeda aquaedulis Moderate Moderate Unknown Low Low

Cyclops kolensis Moderate Moderate Unknown Low Low

Heterocope 

appendiculata

Moderate Moderate Unknown Low Low

Heterocope caspia Moderate Moderate Unknown Low Low

Paramysis (Mesomysis) 

intermedia

Moderate Moderate Unknown Low Low

Leyogonimus polyoon Moderate Moderate Unknown Unknown Low

Paraleptastacus 

spinicaudus triseta

Moderate Low Unknown Low Low

Sinelobus stanfordi Moderate Low Low Low Low

Limnoperna fortunei Low High High High High

Crassula helmsii Low Moderate High Moderate Low

Pseudasbora parva Low Moderate High Unknown Low
35

Siluris glanis Low Moderate High Low High

Podonevadne trigona 

ovum

Low Moderate Moderate Low Low

Oncorhynchus keta Low Moderate Moderate Low High

Benthophilus stellatus Low Moderate Unknown Low Low

Carassius carassius Low Moderate Unknown Low Moderate

Clupeonella cultriventris Low Moderate Unknown Low Low

Ectinosoma abrau Low Low Unknown Low Low

Apocorophium lacustre has the distinction of being the only species in our assessment to score both 

highly likely to be introduced and highly likely to become established. Unfortunately, data were

insufficient to assess its potential environmental impact. This species should be a priority for future 

assessment.

Fifteen species scored as highly likely to be introduced and moderately likely to become established while 

12 species scored as moderately likely to be introduced and highly likely to become established if 

introduced. These species should be considered as having an overall assessment to this point of 

moderately likely to be both introduced and established. Of these 27 species, 14 were identified as likely 

to have high environmental and/or socioeconomic impacts in the event of establishment. These species 

included five plants (Eichhornia crassipes, Pistia stratiotes, Hydrilla verticillata, Egeria densa, and 

Myriophyllum aquaticum), six fishes (Hypophthalmichthys nobilis, Hypophthalmichthys molitrix, Rutilus 

rutilus, Ctenopharyngodon idella, Alburnus alburnus, and Perccottus glenii), and three invertebrates

(Fredericella sultana, Dikerogammarus villosus, and Obesogammarus crassus) which should be 

considered to pose the greatest threat to the Great Lakes.

Five species (Leuciscus leuciscus, Perca fluviatilis, Osmerus eperlanus , Paramysis ullskyi and

Hygrophila polysperma) were assessed as moderately likely to be introduced and moderately likely to 

become established as well as having high potential for environmental or socioeconomic impacts. These 

species can be considered to have only a slightly lower likelihood of posing a significant threat to the 

Great Lakes relative to the previous fourteen. 

Two species (Sander lucioperca and Obesogammarus obesus) that were assessed as having a low 

probability of introduction had a high probability of establishment and subsequent high impact. 

Within this dataset, likelihood of introduction and establishment did not correlate (see Figure 6); although 

introduction is a necessary prerequisite for establishment, it was not itself a good predictor of whether or 

not a species will be able to establish. 
36

Figure 6: The likelihood of introduction does not correlate with the likelihood of a species becoming established 

after introduction.

Similarly, neither introduction nor establishment scores are good predictors of an organism’s potential 

impact (see Figure 7). 

Figure 7: The likelihood of establishment is not correlated with an organisms potential environmental impact.

0

50

100

150

0 40 80 120 160 200 240 280 320 360 400 440 480

Establishment Score

Introduction Score

0

3

6

9

12

15

18

21

24

27

30

33

36

0 50 100 150

Environmental Impact Score

Establishment Score
37

Figure 8: The likelihood of establishment is not correlated with an organisms potential socio-economic impact.

4. DISCUSSION

This assessment provides a unique opportunity to compare the overall risk posed by various species 

across all taxa. While somewhat skewed by the biases of the available scientific literature (e.g., ready 

availability of data on ballast-water mediated invaders of Eurasian origin in contrast to lack of 

information other vectors, source populations, and taxa) and the limitations of such (e.g., data was 

insufficient to assess potential environmental impacts for many species) as well as providing only a semiquantitative assessment, nonetheless it provides insight into the patterns of invasion threats facing the 

Great Lakes region. This risk assessment approach has advantages in that it is relatively quick, most 

needed information is readily available, it allows cross-taxa comparisons, and it supports decisionmaking. Other strengths of the tool include assessment of the full suite of positive and negative impacts 

to account for multiple stakeholder values in light of potential consequences, as well as pan-invasion 

stages (introduction, establishment, consequence) to gauge risk more fully.

Like most risk assessments, this framework was faced with the challenge of addressing uncertainty, both

in its development and its application to the Great Lakes watchlist. In applying the framework to the 

Great Lakes watchlist, most of the uncertainty was epistemic in nature and associated with the 

environmental impact component. Uncertainty resulted in low confidence in the outcome with regard to 

introduction for only 1 specie (1%) and with regard to establishment for only 4 species (6%). Assessment 

of potential benefits was limited for only 1 specie (1%) and assessment of potential socioeconomic impact 

limited for only 5 species (7%). In contrast, assessment of potential environmental impact was limited for 

26 species (39%); however, this seems more a limitation of the availability of environmental knowledge 

than of risk assessment per se given that in a similar assessment of the impact of established invaders 

nearly half (49%) of species could not be assessed due to insufficient information (Sturtevant et al 2014).

Despite the overall shipping bias, species with a high potential for introduction—including those of a 

particular taxonomic group (e.g., fishes, plants)—were fairly evenly distributed among vectors. All 

assessed taxonomic groups had members with high-moderate potential for introduction. This suggests

that managers need to go beyond single vector- or taxon-based assessments when developing their

prevention and monitoring strategies.

0

3

6

9

12

15

18

21

24

27

30

33

36

0 50 100 150

Socioeconomic Impact Score

Establishment Score
38

This study identified a subset of 16 species which should be considered the highest overall risk 

(introduction + establishment + impact) to the Great Lakes region. These include five plants (Eichhornia 

crassipes, Pistia stratiotes, Hydrilla verticillata, Egeria densa, and Myriophyllum aquaticum), six fishes

(Hypophthalmichthys nobilis, Hypophthalmichthys molitrix, Rutilus rutilus, Ctenopharyngodon idella, 

Alburnus alburnus, and Perccottus glenii), and four invertebrates (Apocorophium lacustre, Fredericella 

sultana, Dikerogammarus villosus, and Obesogammarus crassus). Fact sheets have been developed for 

each of these species (available through GLANSIS 

http://www.glerl.noaa.gov/res/Programs/glansis/glansis.html) which provide information on 

identification, life history, ecology, invasion history, risk assessment, potential impacts, and management 

options as well as a summary of the individual risk assessment. It is our intent that this information 

resource should assist managers in targeting prevention programs, early detection and rapid response. 

5. ACKNOWLEDGEMENTS

We gratefully acknowledge the support of numerous students who worked with our team on literature 

review and risk assessment for individual species; this work could not have been accomplished without 

the contributions of their time and effort: Karim Alame, Marie Arnaout, Mitra Asgari, Ahmed Michael 

Beydoun, Emily Byrnes, Jacob Dombroski, Tiana Dudley, George Ibrahim Fakhouri, Aimee Faloppa, 

Mavis Gappy, Abbas Jamaluddin, Arjewan Talib Jassim, Christopher Kramb, Christina Kassis, Cathy 

Kelly, Abhin Kumar, Julie Larson, Marc Narcisse, Cody Narlock, Carly Nowicki, Chandani Patel, 

Douglas Putt, Ahmed Saad, Jomana Shayota, Heather Siersma, Cherish Stottlemyer, Amy Szczepanski, 

Madelyn Tucker, Viviana Veber, and Holly Witman. 

Many thanks are given to Donna Kashian for Wayne State University (WSU) student and postdoctoral 

researcher oversight and support, and to the GLANSIS expert review panel for valuable input and 

feedback, including Sarah Bailey, Hunter Carrick, Jeffrey Gunderson, Nicholas Mandrak, Anthony 

Ricciardi, and Robin Scribailo. 

This research was funded through Great Lakes Restoration Initiative interagency agreement 

#DW-13-92312201-0. Additional support was provided by Great Lakes Restoration Initiative award 

EPA-R5-GL2012-1 and through D. Kashian at Wayne State University. W. Conard, K. Dettloff, and J. 

Li received support from the Cooperative Institute for Limnology and Ecosystem Research (CILER) 

through the NOAA Cooperative Agreement with the University of Michigan (NA12OAR4320071). 

This is GLERL Contribution No. 1841 and CILER Contribution No. 1101.

6. LITERATURE CITED

Andersen, M., H. Adams, B. Hope, and M. Powell. Risk assessment for invasive species. Risk Analysis

24: 787-793 (2004). 

Baker, R., R. Black, G. Copp, K. Haysom, P. Hulme, M. Thomas, A. Brown, M. Brown, R. Cannon, J. 

Ellis, E. Ellis, R. Ferris, P. Glaves, R. Gozlan, H. Holt, L. Howe, J. Knight, A. MacLeod, N. Moore, J. 

Mumford, S. Murphy, D. Parrott, C. Sansford, G. Smith, S. St-Hilaire, and N. Ward. The UK risk 

assessment scheme for all non-native species. Neobiota 7: 46-57 (2007). 

Burgman, M.A., D.A. Keith, and T.V. Walshe. Uncertainty in comparative risk analysis for threatened 

Australian plant species. Risk Analysis 19: 585-598 (1999). 
39

Campbell, M. An overview of risk assessment in a marine biosecurity context. Marine Bioinvasions

Ecology, Conservation, and Management Perspectives (ed. by G. Rilov and J. Crooks). Kluwer Academic 

Publishers, Dordrecht, The Netherlands 353-373 pp. (2009).

Colautti, R.I., A.J. Niimi, C.D. van Overdijk, E.L. Mills, K. Holeck, and H.J. MacIsaac. Spatial and 

temporal analysis of transoceanic shipping vectors to the Great Lakes. Island Press: Washington DC

(2003).

Dahlstrom, A., C.L. Hewitt, and M.L. Campbell. A review of international, regional and national 

biosecurity risk assessment frameworks. Marine Policy 35 (2): 208-217 (2011).

Executive Order (E.O.) No. 13112. Federal Register 64 (25):6183-6186 (1999). 

http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=1999_register&docid=99-3184- filed.pdf.

Gordon, D.R., C.A. Gantz, C.L. Jerde, W.L. Chadderton, R.P. Keller, and P.D. Champion. Weed Risk 

Assessment for Aquatic Plants: Modification of a New Zealand System for the United States. PLoS One 7

(7): e40031 (2012).

Great Lakes Restoration Initiative (GLRI) Task Force. GLRI Action Plan FY2010-FY2014 (2010).

http://greatlakesrestoration.us/action/wp-content/uploads/glri_actionplan.pdf.

Grigorovich, I.A., R.I. Colautti, E.L. Mills, K. Holeck, A.G. Ballert, and H.J. MacIsaac. Ballast-mediated 

animal introductions in the Laurentian Great Lakes: retrospective and prospective analyses. Canadian 

Journal of Fisheries and Aquatic Sciences 69: 740-756 (2003). 

Hayes, K.R. A review of ecological risk assessment methodologies. In: Technical Report 13 (ed. Centre 

for Research on Introduced Marine Pests), Australia (1997).

Hobbs, R.J. and S.E. Humphries. An Integrated Approach to the Ecology and Management of Plant 

Invasions. Un enfoque integrado a la ecología y manejo de las invasiones de plantas. Conservation 

Biology 9: 761-770 (1995).

Holeck, K.T, E.L. Mills, H.J. MacIsaac, M.R. Dochoda, R.I. Colautti, and A. Ricciardi. Bridging troubled 

waters: biological invasions, transoceanic shipping, and the Laurentian Great Lakes. BioScience 54 (10): 

919-929 (2004).

Keller, R.P., J.M. Drake, and D.M. Lodge. Fecundity as a Basis for Risk Assessment of Nonindigenous 

Freshwater Molluscs. Conservation Biology 21: 191-200 (2007a).

Keller, R.P., D.M. Lodge, and D.C. Finnoff. Risk assessment for invasive species produces net 

bioeconomic benefits. Proceedings of the National Academy of Sciences of the United States of America 

104: 203-207 (2007b).

Keller, R.P., D.M. Lodge, M.A. Lewis, and J.F. Shogren. Bioeconomics of invasive species: integrating 

ecology, economics, policy, and management. Oxford University Press (2009).

Kelly, D.W. Vectors and pathways for nonindigenous aquatic species in the Great Lakes. Transportation 

Research Board Special Report (2007).

Kocik, J.F., and M.L. Jones. Pacific salmonines in the Great Lakes basin. Great Lakes Fisheries Policy 

and Management: A Binational Perspective. Taylor, W.W., and C.P. Ferreri (Eds.). Michigan State 

University Press, East Lansing, MI, 455-488 pp. (1999).
40

Leung, B., D.M. Lodge, D. Finnoff, J.F. Shogren, M.A. Lewis, and G. Lamberti. An ounce of prevention 

or a pound of cure: bioeconomic risk analysis of invasive species. Proceedings of the Royal Society of 

London: Biological Sciences 269 (1508): 2407-2413 (2002).

Lodge, D. M., S. Williams, H.J. MacIsaac, K.R. Hayes, B. Leung, S. Reichard, R.N. Mack, P.B. Moyle, 

M. Smith, D.A. Andow, J.T. Carlton, and A. McMichael. Biological Invasions: Recommendations for 

U.S. Policy and Management. Ecological Applications 16: 2035–2054 (2006).

Marson, D., B. Cudmore, D.A.R. Drake, and N.E. Mandrak. Summary of a survey of aquarium owners in 

Canada. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2905: 1-18 (2009). 

Mendoza, R., S. Contreras, P. Koleff, C. Ramirez, C. Escalera, P. Alvarez, B. Cudmore, N. Mandrak, J.P. 

Fisher, R. Orr, W. Courtenay, G. Greene, and D. Lee. Proposed trinational risk assessment guidelines for 

invasive alien species: test cases for the snakeheads (Channidae) and Armored Catfishes (Loricariidae) in 

North American waters. Commission for Environmental Cooperation (2009).

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. Exotic species in the Great Lakes: A history of 

biotic crises and anthropogenic introductions. Journal of Great Lakes Resources 19: 1-54 (1993).

NOAA. Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS) (2012). 

http://www.glerl.noaa.gov/res/Programs/glansis/glansis.html.

Parker, I.M., D. Simberloff, W.M. Lonsdale, K. Goodell, M. Wonham, P.M. Kareiva, M.H. Williamson, 

B. Von Holle, P.B. Moyle, J.E. Byers, and L. Goldwasser. Impact: Toward a framework for 

understanding the ecological effect of invaders. Biological Invasions 1 (1): 3-19 (1999).

Pheloung, P.C., P.A. Williams, and S.R. Halloy. A weed risk assessment model for use as a biosecurity 

tool evaluating plant introductions. Journal of Environmental Management 57 (4): 239-251 (1999).

Ricciardi, A. Patterns of invasion in the Laurentian Great Lakes in relation to changes in vector activity. 

Diversity and Distributions 12 (4): 425-433 (2006).

Rixon, C.A.M., I.C. Duggan, N.M.N. Bergeron, A. Ricciardi, and H.J. MacIsaac. Invasion risks posed by 

the aquarium trade and live fish markets on the Laurentian Great Lakes. Biodiversity and Conservation

14: 1365-1381 (2005).

Rothlisburger J.D., W.L. Chadderton, J. McNulty, and D. Lodge. Aquatic Invaisve Species Transport Via 

Trailered Boats: What is Being Moved, Who is Moving it, and What Can Be Done. Fisheries 35 (3): 121-

132 (2010).

Simberloff, D. How Much Information on Population Biology Is Needed to Manage Introduced Species? 

Conservation Biology 17: 83-92 (2003).

Southwick Associates. Sportfishing in America: An Economic Engine and Conservation Powerhouse. 

Produced for the American Sportfishing Association with funding from the Multistate Conservation Grant 

Program, Alexandria, VA, 12 pp. (2007). 

http://www.asafishing.org/images/statistics/resources/SIA_2008.pdf

Springborn M., C. Romagosa, and R. Keller. The Value of Nonindigenous Species Risk Assessment in 

International Trade. Ecological Economies 70 (11): 2145-2453 (2011).
41

Sturtevant, R.A., J. Larson, L. Berent, M. McCarthy, A. Bogdanoff, A. Fusaro and E.S. Rutherford. An 

Impact Assessment of GreatLakes Aquatic Nonindigenous Species. NOAA TM-161 (2014).

http://www.glerl.noaa.gov/ftp/publications/tech_reports/glerl-161/tm-161.pdf

Talhelm, D.R. Economics of Great Lakes fisheries: A 1985 assessment. Technical Report No. 54. Great 

Lakes Fishery Commission, Ann Arbor, MI 54 pp. (1985). 

http://www.glfc.org/pubs/TechReports/Tr54.pdf

U.S. Army Corps of Engineers (USACE). Commercial fisheries baseline economic assessment – U.S. 

waters of the Great Lakes, Upper Mississippi River, and Ohio River Basins 92 pp. (2012).

http://glmris.anl.gov/documents/docs/Commercial_Fisheries_Report.pdf

United States Army Corps of Engineers (USACE). Great Lakes and Mississippi River Interbasin Study: 

Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway 

System (2012).

United States Environmental Protection Agency (USEPA). Predicting future introductions of 

nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Office of 

Resarch and Development. Washington, D.C. (2008).

U.S. Fish and Wildlife Service and Great Lakes Fishery Commission (USFWS/GLFC). Great Lakes Fish 

Stocking Database. U.S. Fish and Wildlife Service, Region 3 Fisheries Program, and Great Lakes Fishery 

Commission (2010). http://www.glfc.org/fishstocking/

United States Geological Survey. Nonindigenous Aquatic Species Database (2011).

http://www.nas.er.usgs.gov/

Verbrugge, L.N., G. van der Velde, A.J. Hendriks, H. Verreycken, and R. Leuven. Risk classifications of 

aquatic non-native species: application of contemporary European assessment protocols in different 

biogeographical settings. Aquatic Invasions 7: 49-58 (2012).

Wittmann, M.E., R.M. Cooke, J.D. Rothlisberger, and D.M. Lodge. Using Structured Expert Judgment to 

Assess Invasive Species Prevention: Asian Carp and the Mississippi – Great Lakes Hydrologic 

Connection. Environ. Sci. Technol. 48(4)2150-2156 (2014).
42

APPENDIX A. RISK ASSESSMENTS

A.1 Fishes

Scientific Name: Alburnus alburnus 

Linnaeus, 1758

Common Name: Bleak, Alver

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Alburnus alburnus has a moderate probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

From its native range, Alburnus alburnus was locally introduced to the Iberian Peninsula, Spain, Portugal, 

and Italy (Kottelat 1997). This fish species was intentionally introduced to the Northern Iberian watershed 

by anglers in an attempt to increase the stock of forage for nonnative fish predators and was used as a 

popular live baitfish (Vinyoles et al. 2007). Alburnus alburnus is found in the Seine, Loire, and Rhine 

Rivers, which naturally discharge into the Atlantic Ocean (Leuven et al. 2009). It occurs in ports that have 

direct trade connections with the Great Lakes.

Through ballast exchange practices, A. alburnus may experience high mortality due to its inability to 

survive waters with high salinity, limiting its introduction to the Great Lakes (Wheeler 1978a). However, 

it has been shown that 35% of “No Ballast on Board” (NOBOB) vessels, which are exempt from 

mandatory ballast exchange, possess at least 1 tank with ≤ 5‰ salinity, thus enhancing the potential for A. 

alburnus to survive transport overseas to be introduced into the Great Lakes (Niimi and Reid 2003). 

Currently, the geographical distribution of Alburnus alburnus does not cover water bodies connected to 
43

the Great Lakes basin. Alburnus alburnus is not a popular aquarium fish and is not available for purchase 

online. Alburnus alburnus is not available as live baitfish for online purchase in North America. There are 

import restrictions regarding the transport of Alburnus alburnus to the United Kingdom (Clarke 2006). It 

is predicted that the geographical range of this species will expand due to climate change (Lehtonen 

1996).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Alburnus alburnus resides in slow flowing streams and temperate lakes located in Europe and Asia. Its native 

range extends north of the Pyrenees, Caucasus, and Alps, and eastward toward the Ural and Emba rivers. It 

was later locally introduced to the Iberian Peninsula and is found in Spain, Portugal, and Italy (Kottelat 1997).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?
44

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Alburnus alburnus is not a popular aquarium fish or available for purchase online. Import restrictions have 

been placed on the transfer of Alburnus alburnus to the United Kingdom (Clarke 2006).

 Alburnus alburnus was locally introduced in the Northern Iberian watershed as a result of anglers purposefully 

releasing it as a forage fish (Vinyoles et al. 2007). It is also a popular live baitfish when targeting predatory 

fish such as pike and perch (Vinyoles et al. 2007).

 Alburnus alburnus is not available for purchase as a live baitfish in North America through online vendors.

 There is no evidence to suggest that Alburnus alburnus is easily obtained even within its native range; 

therefore, obtaining it in the Great Lakes region would also be very difficult and highly unlikely.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Alburnus alburnus is not stocked near the Great Lakes.
45

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Alburnus alburnus scales are used in the artificial pearl trade and this fish is harvested commercially in the 

Seine, Loire, and the Rhine rivers (Denton and Nicol 1965). However, such commercial activity is limited to 

Europe.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 
46

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 

Unknown U

 Alburnus alburnus is a brackish water fish that lives in a salinity of 8-10 ‰ (Linden et al. 1979). Due to its 

stenohaline nature, survival of ballast water regulations is unlikely (Wheeler 1978a).

 Myers (1949) categorizes Cyprinidae as strictly intolerant of salt water. There is no indication that A. alburnus

exhibits avoidance behaviors that would allow it to survive transport.

 Niimi and Reid (2003) measured the salinity of ‘No Ballast on Board’ or NOBOB vessels which are exempt 

from mandatory ballast exchange. Out of the 26 vessels measured, 35% had at least one tank with ≤ 5 ‰ 

salinity. It is possible that the bleak would be able to survive transport under these conditions.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Alburnus alburnus is found in the Seine, Loire, and Rhine rivers, which naturally discharge into the Atlantic 

Ocean (Leuven et al. 2009). The Rhine first discharges into the North Sea, which connects to the Atlantic 

Ocean.

 Alburnus alburnus occurs in the Iberian Peninsula and is found in Spain, Portugal, and Italy (Kottelat 1997, 

Vinyoles et al. 2007). There are many ports in the Iberian Peninsula that have direct connections with the Great 

Lakes.
47

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Alburnus alburnus has a high probability of establishment if introduced to the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
48

(Confidence level: High). 

Following its introduction into the Ebro basin in Spain, this species rapidly established throughout the 

entire Iberian Peninsula, where it is currently present in all of the major Iberian water basins and a large 

number of Iberian rivers, suggesting that it has the ability to adapt to a warmer climate regime (Vinyoles 

et al. 2007). After its establishment in Britain, Alburnus alburnus consequently spread and established in 

Cyprus. It is believed that the high fecundity rate of this species is responsible for its establishment. It is a 

multiple spawner, so it spawns more frequently than Rutilus rutilus (Rinchard and Kestemont 1996). 

Where it has been introduced, Alburnus alburnus produces stunted populations that produce a large 

number of individuals that mature early at a small size (Welcomme 1988).

If Alburnus alburnus were introduced to the Great Lakes, it has the potential to spread rapidly (Kolar and 

Lodge 2002). The climate of the Great Lakes is similar to the native range of Alburnus alburnus and this 

species is likely capable of enduring overwintering conditions in the Great Lakes basin (Grigorovich et al. 

2003, Reid and Orlova 2002, USEPA 2008). It is likely that the Great Lakes contain an abundant food 

source for this species. This species has a high reproductive rate (Vinyoles et al. 2007). It has not been 

reported that any natural enemy of Alburnus alburnus such as the tapeworm Ligula intestinalis, occurs in 

the Great Lakes region. In the Thames River, Ligula intestinalis preferentially parasitizes Alburnus 

alburnus, which impairs its swimming ability and increases the risk of predation (Harris and Wheeler 

1974). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Alburnus alburnus typically lives in a temperature range of 10-20°C (Baensch and Riehl 1991). 

 A study regarding lethal temperature for various fish species indicates that the A. alburnus’ lethal temperature 

range is 37.7-40.6°C at acclimation temperatures from 25.0-27.8°C in a lake environment where temperature 

was gradually raised per hour (Horoszewicz 1973). 

 Alburnus alburnus is a brackish water fish that typically lives in salinities of 8-10 parts per thousand (Linden et 

al. 1979). There is no information to indicate that A. alburnus would be able to survive higher salinities.

 A study indicates that A. alburnus does not withstand oxygen-stressed environments particularly well 

(Willemsen 1980).

 Alburnus alburnus is tolerant to pollutants such as brominated flame retardents (Eljarrat et al. 2005).

 According to Souchon and Tissot (2012), 14°C is the minimum temperature tolerated for reproduction.
49

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

Alburnus alburnus most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Alburnus alburnus feeds on zooplankton and insects in the epilimnion. Alburnus alburnus is described to have a 

limited diet in comparison with the roach, Rutilus rutilus, a generalist (Keckeis and Schiemer 1990).

 Vinyoles et al. (2007) cited A. alburnus’ prey as widespread and attributes this characteristic to its successful 

establishment outside its native range.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6
50

 Alburnus alburnus is currently threatening endemic species in the Iberian watershed due to its high 

reproductive rate and hybridization with other cyprinids (Vinyoles et al. 2007).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

8

 The bleak’s high fecundity has allowed it to become established in Cyprus where it was accidentally introduced, 

as well as in the Iberian watershed (Vinyoles et al. 2007). 

 Alburnus alburnus and Blicca bjoerkna are multiple spawners which spawn more frequently than the single 

spawner Rutilus rutilus (Rinchard and Kestemont 1996). Compared to R. rutilus and B. bjoerkna, A. alburnus 

has a relatively moderate gonadosomatic index. 

 Where it is introduced, A. alburnus produces stunted populations that produce a large number of individuals 

that mature early at a small size (Welcomme 1988). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self-fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 Where it is introduced, Alburnus alburnus produces stunted populations that produce a large number of 

individuals that mature early at a small size (Welcomme 1988). 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
51

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The surface water temperature range of the water in the Ponto-Caspian region is similar to many of the lakes in 

the Great Lakes region (Reid and Orlova 2002). 

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 The Ponto-Caspian (Caspian, Azov, and Black seas) have similar climate and surface water temperature ranges 

as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 The bleak tends to live in shoals near the surface of slow-moving streams and lakes (Kottelat 2012, Linden et 

al. 1979). Bleak larvae inhabit the littoral zone of rivers/lakes and juveniles occur in a pelagic habitat (Kottelat 

2012). 
52

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Lehtonen (1996) predicted that European fish assemblages will shift toward cyprinid dominance and that A. 

alburnus’s range will expand as a result of global climate change.

 The Bleak’s establishment in the Iberian watershed (Vinyoles et al. 2007) points toward its ability to adapt to a 

warmer climate regime.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 The widespread nature of the Bleak’s prey has allowed it to successfully expand throughout its native and 

introduced ranges (Vinyoles et al. 2007). It is likely that the Bleak would have an abundant food source in the 

Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

9
53

assessed;

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no evidence to indicate that the Bleak requires another species to survive during critical stages in its 

life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is no evidence to indicate that A. alburnus would benefit from the spread of another species already in 

the Great Lakes.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

-80% total 

points (at 

end)
54

Great Lakes)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 There have been reports of the tapeworm Ligula intestinalis preferentially parasitizing Alburnus alburnus in the 

River Thames (Harris and Wheeler 1974). Infestation may cause impairment of swimming ability (Harris and 

Wheeler 1974), which can increase the risk of predation. Generally, however, infestation does not lead to death 

of the host. Ligula intestinalis has not been reported to occur in the Great Lakes region.

 There is no indication of a natural enemy/predator that would prevent the establishment of the Bleak.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 When a ship enters the Great Lakes it discharges approximately 3 million liters of ballast water (Ricciardi and 

MacIsaac 2000).

 Shipping traffic from Western Europe through the St. Lawrence Seaway is a major contributor of ballast water 

discharge that enters the Great Lakes (USEPA 2008).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

3
55

proximity to each other)

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 The Bleak was introduced northern Iberian watershed and is now present in all major Iberian water basins and 

a large number of Iberian rivers (Vinyoles et al. 2007).

 Vinyoles et al. (2007) also noted that Alburnus alburnus has been introduced to Cyprus from Britain where it 

has established a breeding population. 

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 Following its introduction into the Ebro basin, Alburnus alburnus quickly spread throughout the entire Iberian 

Peninsula, where it is currently present in all major Iberian basins (Vinyoles et al. 2007).

 Kolar and Lodge (2002) predicted that the Bleak would spread quickly if introduced to the Great Lakes.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no existing control measures in the Great Lakes to prevent the spread of the Bleak.
56

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 102

>100 High Adjustments

B. Critical species A*(1- 0%) 102

51-99 Moderate C. Natural enemy B*(1- 0%) 102

Control measures C*(1- 0%) 102

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: High

Alburnus alburnus has the potential for high environmental impact if introduced to the Great 

Lakes.

Alburnus alburnus is a superior competitor because of its high reproductive rate, its non-specific diet, and 

its ability to tolerate a broad range of temperatures. Alburnus alburnus exhibits large and sudden bursts in 

population size so it has outcompeted native species where established (Pérez-Bote et al. 2004, Vinyoles 

et al. 2007, Welcomme 1988). In a study done by Maceda-Veiga et al. (2010) Alburnus alburnus was the 

second most frequently occurring fish sampled in the catchments of Catalonia, Spain. The authors also 

noted that native fish populations declined by an average 60% in the Catalonian catchments, and 

amphidromous species A. arcasii had experienced local extinctions. It is able to hybridize with other 

cyprinids (Maceda-Veiga et al. 2010, Blachuta and Witkowski 1984, Crivelli and Dupont 1987). In the 

Iberian watershed, Alburnus alburnus threatens endemic species through hybridizing with other cyprinids 

and its generally high reproductive rate (Vinyoles et al. 2007). Besides impacting native fish fauna, 

Alburnus alburnus feeds on cladoceran and other small invertebrates that play an important role in 

freshwater ecosystems and directly affect the water quality (Maceda-Veiga et al. 2010). This species 

exhibits a high level of plasticity in population traits and is able to adapt to a wide variety of 
57

environmental conditions. The mortality rate of Alburnus alburnus is higher in rivers than in lakes, but 

reproduction rates are higher in rivers (Almeida et al. 2014). 

There is little or no evidence to support that Alburnus alburnus has the potential for significant 

socio-economic impact if introduced to the Great Lakes.

Alburnus alburnus may affect water quality by feeding on organisms that play a direct role in water 

quality (Maceda-Veiga et al. 2010). 

Alburnus alburnus has the potential for high beneficial effects if introduced to the Great Lakes.

This species may be commercially valuable as forage fish and baitfish (Pérez-Bote et al. 2004), and the 

artificial pearl trade (Denton and Nicol 1965). In Europe, it has been introduced into various reservoirs to 

benefit the populations of exotic fish predators such as the Northern Pike (Esox Lucius), Largemouth Bass 

(Micropterus salmoides), Zander (Sander lucioperca), and Wells Catfish (Silurus glanis) (Maceda-Veiga 

et al. 2010).

Establishment of Alburnus alburnus may increase productivity of predator fish in the Great Lakes, 

especially for predatory fish that do not have specific diets.

POTENTIAL ENVIRONMENTAL IMPACT

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 Alburnus alburnus possesses a suite of life history traits that makes it a superior competitor. Its speed and 

specialization in surface-oriented feeding gives it a competitive advantage over fishes that only occasionally 

feed on the surface. Furthermore, this species’ high fecundity allows it to displace other species. Bleak 

experiences large and sudden population increases that easily overpower and outcompete species already 

present. Such situations have been observed in Iberian rivers (Pérez-Bote et al. 2004, Vinyoles et al. 2007, 
58

Welcomme 1988). Other factors that may contribute to the bleak’s superior competitive abilities include its 

ability to exploit a widespread spectrum of prey and its wide temperature tolerance (Biró and Muskó 1995, 

Chappaz et al. 1987, Mehner et al. 2005).

 In a study done by Maceda-Veiga et al. (2010) A. alburnus was found to be the second highest non-native 

occurring fish in sampled catchments in Catalonia, Spain. Maceda-Veiga et al. noted that endemic fish 

populations have declined greatly (by a mean of 60%) in the Catalonian catchments even to the extent that the 

amphidromous species A. arcasii has suffered local extinctions. The article hypothesized that in addition to 

habitat alteration, introduced species such as C. carpio and A. alburnus have an impact on native fish fauna.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6 √

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U

 Bleak hybridizes easily with other cyprinids (Blachuta and Witkowski 1984, Crivelli and Dupont 1987). 

Squalius alburnoides resulted as a hybridization of Squalius, Bleak, and Anaecypris. 

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 √

Not significantly 0 

Unknown U

 Besides its impact on native fish fauna, Bleak feeds on cladoceran and other small invertebrates that play an 

important role in these ecosystems and directly affect the water quality (Maceda-Veiga et al. 2010).
59

 Horppila and Kairesalo (1992) examined the effects of A. alburnus on water quality by placing the fish in 

enclosures in the field. Algal production and chlorophyll-α levels were over two times more than enclosures 

without A. alburnus.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 

Unknown U

 Field studies suggest that a Bleak population can increase algal productivity and biomass (Horppila and 

Kairesalo 1992).

Environmental Impact Total 14

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?
60

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

6
61

value for future generations

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 Alburnus alburnus is exploited commercially in parts of Europe, as a baitfish or forage fish (Elvira 1995, 

Pérez-Bote et al. 2004) and in the pearl trade (Denton and Nicol 1965). Additionally, Bleak have being 
62

introduced into various reservoirs in order to improve the populations of exotic fish predators such as the 

Northern Pike (Esox lucius), the Largemouth Bass (Micropterus salmoides), the Zander (Sander lucioperca),

and the Wells Catfish (Silurus glanis) (Maceda-Veiga et al. 2010).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 

 Bleak have being frequently used to enhance the populations of exotic fish predators such as the Northern Pike 

(Esox lucius), the Largemouth Bass (Micropterus salmoides), the zander (Sander lucioperca) and the Wells 

Catfish (Silurus glanis) (Maceda-Vega et al. 2010).
63

Beneficial Effect Total 7

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
64

Scientific Name: Atherina boyeri

Risso, 1810

Common Name: Big-scale Sand Smelt, Boyer’s Sand Smelt, Black Sea Silverside

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Atherina boyeri has a moderate probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Transoceanic shipping (ballast water)

Atherina boyeri does not currently occur near waters connected to the Great Lakes. There is no indication 

that this species is sold or stocked in North America. However, it occurs in ports that have direct 

connections with the Great Lakes (NBIC).

Atherina boyeri has commercial value as a prey of highly-priced carnivorous fish such as sea bass, 

Dicentrarchus labrax. This species is introduced into freshwater lakes and reservoirs in Europe to 

enhance stock (Economidis et al. 2000). In Turkey, it has been introduced to several lakes by local 

fishermen (Innal and Erk’akan 2006). It can survive in hypersaline conditions up to 110% salinity and 

temperatures between 6-25°C (Henderson and Bamber 1987). It is likely that Atherina boyeri has the 

potential to survive ballast tank environments. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, 

including connecting channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 √
65

not mobile or able to be transported by wind or water.

Unknown U

 Atherina boyeri is a Ponto-Caspian fish that is also found in Portugal and Spain toward Nouadhibou in 

Mauritania and Madeira (Quignard and Pras 1986). Also found in the Mediterranean (Whitehead et al. 1986). 

There are isolated populations on the coasts of England and the Netherlands. 

 Atherina boyeri does not occur in North America (Kolar and Lodge 2002). 

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
66

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Atherina boyeri is a relatively important commercial fish in Greece (Leonardos and Sinis 2000).

 While commonly fried in some European and Middle Eastern cuisines (İzci et al. 2011), it does not appear 

to be sold in live trade.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 No data were found about this species in the United States.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 No data were found about this species in the United States.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE
67

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 While this species has been used for fishery purposes in some countries, no information was found regarding its 

fishery in the United States. 

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This species is a Ponto-Caspian atherinid fish identified as having high probability of invasion if introduced to 

the Great Lakes (Kolar and Lodge 2002). Its potential pathway of introduction is ballast water.

 Atherina boyeri is a very euryhaline species and can survive in temperatures 6-25 ̊C.

 Atherina boyeri can tolerate fresh to hypersaline waters (Henderson and Bamber 1987, Leonardos and Sinis 

2000).
68

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 A. boyeri occurs on the coasts of England, such as the Cornish coast (located along southern England) (Clowes 

1884). There are several ports along the southern coast of England that are in direct trade with the Great 

Lakes.

Scoring

Points (per vector) Probability for Introduction

80-100 High

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
69

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Atherina boyeri has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate). 

The native and introduced ranges of Atherina boyeri have similar climatic and abiotic conditions to that of 

the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). If introduced, Atherina 

boyeri is likely to find a suitable habitat in the Great Lakes. Although it is commonly found in estuaries, it 

has no problem establishing in freshwater due to its ability to tolerate a broad range of salinities and adapt 

quickly (Henderson and Bamber 1987, Leonardos and Sinis 2000). It is thermophilous, therefore its 

ability to survive the winters of the Great Lakes is limited (den Hartog and van der Velde 1987, 

Henderson and Bamber 1987). Atherina boyeri exhibits a rapid growth rate, early maturity, and frequent 

spawning over a long breeding season (Fernández-Delgado et al. 1988). Its reproductive strategy may 

contribute to its establishment if introduced to the Great Lakes.

Atherina boyeri can adapt to new environments rapidly. It established as a nonnative fish in Lake Ĕgirdir 

within 2 years of its introduction (Küçük et al. 2007). Atherina boyeri is capable of reaching high 

densities; it became a dominant fish in the community, comprising of nearly 50% of the ichthyofauna 

composition in the Mala Neretva estuary (Sršen 1995). The construction of levees in the Neretva River 

estuary changed the environment in a way that benefitted Atherina boyeri populations. Atherina boyeri is 

established in the Netherlands after intentional introduction, but its distribution is bound to waters that 

receive thermal discharge from the cooling systems of power plants (den Hartog and van der Velde 1987).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6
70

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Atherina boyeri survives in euryhaline conditions (coastal and estuarine waters, lagoons, salt marshes, shallow 

brackish, and inland waters) (Leonardos and Sinis 2000). Furthermore, it can tolerate a wide range of 

salinities from freshwater to hypersaline conditions (110% maximum recorded) (Henderson and Bamber 1987).

 This species can tolerate temperatures of 6-25 ̊C (Henderson and Bamber 1987).

 Juveniles have no abiotic preferences (Pombo 2005).

 It is capable of adapting rapidly, perhaps due to the great variety in longevity, reproductive years, size at 

maturity, and maximum size attributed to this species (Henderson and Bamber 1987, Küçük et al. 2012).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

3

 In general, fish from Ponto-Caspian have been able to invade Great Lakes (Ojaveer et al. 2002). 

 This species can tolerate temperatures of 6-25 ̊C (Henderson and Bamber 1987).

 The northern range of this species is limited by the amount of fat the young can lay down (Henderson and 

Bamber 1987).

 It is thermophilous and may not be able to tolerate low temperatures, especially as juvenile fish (den Hartog 

and van der Velde 1987, Henderson and Bamber 1987).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Atherina boyeri is an opportunistic feeder on zooplankton and benthic invertebrates, including copepods, 

cladocerans, gammarid amphipods, mysids and cumaceans, decapod larvae, insects, and eggs (Bartuloviç et al. 

2004). Its diet changes with the seasons and prey availability.

 In typical coastal ecosystems, it preys on zooplankton, while in lagoons and estuaries it feeds on benthic 

organisms (Kiener and Spillman 1969, Trabelsi et al. 1994). Certain studies show that it feeds mainly on 
71

zooplankton and only secondarily on benthic organisms (Rosecchi and Crivelli 1992), while others have found 

a preference for benthic prey (Scipiloti 1998).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

5

 Atheria boyeri probably starts to face intense interspecific competition for food in autumn. Specialized 

predation of A. boyeri on fish larvae, especially in autumn, is likely an ecological adaptation of this species 

against food limitation. Through this behavior, A. boyeri would reduce inter- and intra-specific competition by 

removing a number of competitors that utilize the same food sources and thus raise its energy gains for 

overwintering by consuming food of higher nutrient value (Doulka et al. 2013). However, the level of interspecific competition has not been tested in this ecosystem.

 Fish fry of Economidichthys trichonis and Atherina boyeri were found in A. boyeri stomach contents (Doulka et 

al. 2013). Larvae of Economidichtys trichonis and A. boyeri feed on zooplankton crustaceans, so they may 

compete with each other for food. Economidichthys trichonis is endemic to lakes Trichonis and Lysimachia and 

is threatened and A. boyeri may negatively impact its survival by preying on its larvae. However, the 

competitive abilities of A. boyeri have not been specifically studied. 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Atherina boyeri has a high growth rate, early maturity, frequent spawning over a long breeding season, and 

greatly reduced longevity (Fernández-Delgado et al. 1988).

 This species develops to its full external adult morphology within 2 months of hatching, and reach sexual 

maturity within their first year of life (Henderson and Bamber 1987).

 This species reproduces in the summer with an average fecundity is 110.4 per individual, or a relative fecundity 

of 29.05 eggs per g of fish (Küçük et al. 2012).
72

 Atherina presbyter has an average relative fecundity of 49.2 eggs per g of fish (Moreno et al. 2005). Atherina 

presbyter has a higher relative fecundity than A. boyeri. 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Becoming mature in their first year, A. boyeri forms dominant populations due to its abilities to quickly adapt 

and reproduce in inland waters (Küçük et al. 2012).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 There is a history of successful Ponto-Caspian fish introductions in Great Lakes (Ojaveer et al. 2002).

 Models predict that Atherina boyeri has a potential to establish in Great Lakes if it is introduced (Kolar and 

Lodge 2002).

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?
73

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions of the native and introduced ranges of Atherina boyeri are quite similar 

to the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 There is a history of successful Ponto-Caspian fish introductions in Great Lakes (Ojaveer et al. 2002).

 Atherina boyeri has a potential to establish in Great Lakes if it is introduced (Kolar and Lodge 2002).Great 

Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 2002). 

Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et al. 

2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 In lakes, this species is pelagic, preferring still or slow-flowing waters (IUCN 2008a).

 It occurs in estuarine and coastal environments (Henderson and Bamber 1987), lagoons, salt marshes, shallow 

brackish water ecosystems, and inland waters (Leonardos and Sinis 2000). It has been found in freshwater 

lakes (Doulka et al. 2013).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U
74

9

 This species is found in waters that range from 7.6-26.7°C, so A. boyeri tolerates warm waters (Pombo 2005).

 The northern range of this species is limited by the amount of fat the young can lay down (Henderson and 

Bamber 1987); thus, warmer water temperatures and shorter duration of ice cover may benefit this species 

and/or facilitate this species’ establishment in the Great Lakes. 

 It is likely that salinization of the Great Lakes due to climate change will not greatly impact A. boyeri due to its 

ability to tolerate hypersaline waters (Henderson and Bamber 1987, Leonardos and Sinis 2000). This species 

may tolerate salinization better than freshwater fish native to the Great Lakes.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Atherina boyeri is an opportunistic feeder on zooplankton and benthic invertebrates, including copepods, 

cladocerans, gammarid amphipods, mysids and cumaceans, decapod larvae, insects, and eggs (Bartuloviç et al. 

2004). Its carnivorous diet can also include worms, mollusks, and fish larvae (Quignard and Pras 1986).

 In typical coastal ecosystems, it preys on zooplankton, while in lagoons and estuaries it feeds on benthic 

organisms (Kiener and Spillman 1969, Trabelsi et al. 1994). Certain studies show that it feeds mainly on 

zooplankton and only secondarily on benthic organisms (Rosecchi and Crivelli 1992), while others have found 

a preference for benthic prey (Scipiloti 1998).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 0
75

the Great Lakes but is likely to be introduced

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Atherina boyeri lacks a species critical to its survival.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U
76

U

 Atherina boyeri is preyed on by carnivorous fish such as Sphyraena (Kalogirou et al. 2012). Sphyraena does not 

occur in the Great Lakes, but other piscivores do. It is unknown if piscivores in the Great Lakes would prey on 

A. boyeri.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Atherina boyeri forms dominant populations due to its abilities to quickly adapt and reproduce in inland 

waters. It is considered a potential threat to lentic ecosystems. At the present, it is a common invading exotic 

fish species throughout Turkey (Küçük et al. 2007).

 Atherina boyeri has become dominant in fish communities of the Mala Neretva estuary (Sršen 1995) and Lake 

Trichonis (Doulka et al. 2013). 

 Atherina boyeri was interntionally introduced to the Netherlands and became established, but its distribution is 

restricted to waters that receive thermal discharge from the cooling systems of power plants (den Hartog and 

van der Velde 1987). 

 Its occurrence has been recorded in Sapanca Lake (Geldiay and Balik 1996), Güzelhisar Stream, Köyceğiz 

Lake (Balik 1979), Küçükçekmece Lake (Altun 1999), Lake İznik (Özeren 2004), Homa Lagoon (Sezen 2005), 

Hirfanlı Dam Lake, Beysehir Lake, and Mogan Lake (Innal and Erk’akan 2006), Turkey.

 It has been reported to occur in the Aral Sea and Lake Trasimeno (Freyhof and Kottelat 2008a).
77

 This species has been naturally introduced into Lake Trichonis in Western Greece, via moving from the sea to 

the lake through river channels. It is dominant in the fish community.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 The species established in Lake Ĕgirdir in Turkey within 2 years of introduction (Küçük et al. 2012).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no control methods within the Great Lakes specific to preventing the establishment or spread of this 

species.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 94

>100 High Adjustments

B. Critical species A*(1- 0%) 94

51-99 Moderate C. Natural enemy B*(1- 0%) 94
78

Control measures C*(1- 0%) 94

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: High

Atherina boyeri has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Atherina boyeri is a carrier of the metacercariae of Labratrema minimus, a parasitic trematode that also 

infects gobies (Combes 2001).

In some cases, Atherina boyeri dominates the fish community where introduced. In the Mala Neretva 

esuary, Atherina boyeri reached high densities to the point where it made up 50% of the fish composition 

(Sršen 1995). It is considered as a potential threat to lentic ecoystems (Küçük et al. 2007).

There is little or no evidence to support that Atherina boyeri has the potential for significant socioeconomic impact if introduced to the Great Lakes.

It has not been reported that Atherina boyeri poses a threat to human health or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits.

Atherina boyeri has the potential for high beneficial effects if introduced to the Great Lakes.

Increased population size of Atherina boyeri in the Neretva River estuary enhanced the production of the 

local fishery and the stock of sea bass Dicentrarchu labrax (Küçük et al. 2007). In Greece, it is sold for 

about United States $3 per kg and is edible (El-Sahn et al. 1990, Leonardos and Sinis 2000). 

Introduction of Atherina boyeri may positively impact the populations of Great Lakes predatory fish and 

enhance recreational fishing. If Atherina boyeri were introduced, the parasitic trematode that it carries 
79

may infect invasive gobies of the Great Lakes and help decrease their populations.

POTENTIAL ENVIRONMENTAL IMPACT

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Atherina boyeri harbors the metacercariae of the parasitic trematode Labratrema minimus, which also 

infects gobies (Combes 2001). 

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Fish fry of Economidichthys trichonis and Atherina boyeri were found in A. boyeri stomach contents (Doulka et 

al. 2013). Larvae of E. trichonis and A. boyeri feed on zooplankton crustaceans, so they may compete with each 

other for food. Economidichthys trichonis is endemic to lakes Trichonis and Lysimachia and is threatened and 

A. boyeri may negatively impact its survival by preying on its larvae. However, the competitive abilities of A. 

boyeri have not been specifically studied. 

 Atheria boyeri probably starts to face intense interspecific competition for food in autumn. Specialized 

predation of A. boyeri on fish larvae, especially in autumn, is likely an ecological adaptation of this species 

against food limitation. Through this behavior, A. boyeri would reduce inter- and intra-specific competition by 

removing a number of competitors that utilize the same food sources and thus raise its energy gains for 

overwintering by consuming food of higher nutrient value (Doulka et al. 2013).

 Forming dominant populations due to its abilities to quickly adapt and reproduce in inland waters, A. boyeri is 

considered a potential threat to lentic ecosystems (Küçük et al. 2007).

 In some cases, Atherina boyeri dominates the fish community where introduced. In the Mala Neretva esuary, A. 

boyeri reached high densities to the point where it made up 50% of the fish composition (Sršen 1995). It is 

considered as a potential threat to lentic ecoystems (Küçük et al. 2007).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

6
80

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 2
81

Total Unknowns (U) 4

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?
82

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
83

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 No data were found in this regard.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 Following introduction, this species adapted to Egirdir Lake (Turkey) in a relatively short period (within 2 

years) and commercial fishing began in 2005 (Küçük et al. 2007).

 Beside its direct commercial importance, this species plays an important role in estuarine food web (Bartuloviç

et al. 2004).

 Increased population size of Atherina boyeri in the Neretva River estuary enhanced the production of the local 

fishery and the stock of sea bass Dicentrarchu labrax (Küçük et al. 2007). In Greece, it is sold for about United 

States $3 per kg and is edible (El-Sahn et al. 1990, Leonardos and Sinis 2000).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 No data were found in this regard.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 No data were found in this regard.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?
84

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U

Beneficial Effect Total 6

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
85

Scientific Name: Babko gymnotrachelus

Kessler, 1857

Common Name: Racer Goby

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Babka gymnotrachelus has a moderate probability of introduction to the Great Lakes (Confidence 

level: Moderate). 

Potential pathway(s) of introduction: Transoceanic shipping (ballast water) 

Babka gymnotrachelus currently does not occur near waters connected to the Great Lakes basin. It 

produces sticky eggs (Kottelat and Freyhof 2007); however, it is unknown whether the eggs can foul 

vessels and survive transoceanic transport. This species is not stocked, commercially cultured, or sold in 

the Great Lakes region. 

This species is present in ports that are in direct trade with the Great Lakes (NBIC). Adults can survive 

transport in ships (Kottelat and Freyhof 2007). Other species of gobies have been introduced outside their 

native range via shipping and ballast water: Round Goby (Neogobius melanostomus), Freshwater 

Tubenose Goby (Proterorhinus marmoratus), Monkey Goby (Neogobius fluviatilis), and Bighead Goby 

(Neogobius kessleri) (MacIsaac et al. 2001, Neilson and Stepien 2009a, Stepien and Tumeo 2006). Ballast 

water exchange using full strength sea water for 48 hours will result in 100% mortality of Babka 

gymnotrachelus (Ellis and MacIsaac 2009). Ballast water exchange requires filling ballast tanks with full 

strength sea water for 5 days; ballast water exchange regulations may prevent introduction of Babka 

gymnotrachelus. Babka gymnotrachelus may be introduced to the Great Lakes via ships declaring “No 

Ballast on Board” (NOBOB), which are exempt from ballast water exchange. The majority of ships 

entering the Great Lakes are NOBOB vessels and 43% of these ships contain residual water with less than 

10‰ salinity (Johengen et al. 2005). In the study, the temperature of the residual water from the vessels 

sampled ranged from -0.7 to 23.9°C; thus Babka gymnotrachelus is likely to survive the salinity and 

temperature of the NOBOB ballast water.
86

Babka gymnotrachelus is native to the Ponto-Caspian basin and is also found in the Danube, Dniester, 

and the Bug rivers (Pinchuk et al. 2003). The Main-Danube Canal is one of the main dispersal routes for 

invasive Ponto-Caspian species to move into Central Europe (Leuven et al. 2009). It is currently 

expanding its range into Eastern, Central, and Western European waters (Borcherding et al. 2011, Haertl 

et al. 2012, Kalchhauser et al. 2013), and has reached the Baltic Sea (Danilkiewicz 1998). Its increased 

distribution in Europe has been attributed to canal construction and shipping (Kalchhauser et al. 2013). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting channels, 

wetlands, and waters ordinarily attached to the Lakes) 

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Babka gymnotrachelus is not currently found in North America.

 Babka gymnotrachelus is native to the fresh and slightly brackish (oligo- to meso-haline) waters of the Black, 

Azov (Pinchuk et al. 2003, Stepien and Tumeo 2006, Svetovidov 1964), Caspian, Aral (Neilson and Stepien 

2009), and Marmara seas (Stepien and Tumeo 2006), and the lower courses of Ponto-Caspian region rivers 

(Pinchuk et al. 2003, Polaçik et al. 2009), including the lower Danube and its tributaries and connected lakes 

(Pinchuk et al. 2003), the Dniester and its tributaries (Bodareu 1993, Smirnov 1986), the southern Bug 

(Grabowska and Grabowski 2005), the Dnieper (Bilko 1968, Borcherding et al. 2011, Pinchuk et al. 2003, 

Smirnov 1986, Ulman 1967), and the Don (Borcherding et al. 2011).

 It has been spreading throughout eastern, central, and western European waters (Borcherding et al. 2011, 

Haertl et al. 2012, Kalchhauser et al. 2013, Kottelat and Freyhof 2007), both longitudinally and northward 

(Harka and Biró 2007), and it has reached the Baltic Sea basin (Danilkiewicz 1998).

 This species prefers more stagnant waters (Kakareko et al. 2009) and littoral areas (Eros et al. 2005) in rivers, 

lakes, reservoirs, estuaries, coastal lagoons, backwaters, and industrial harbors (Kalchhauser et al. 2013, 

Kottelat and Freyhof 2007, Wiesner 2005) in at least Austria (Ahnelt et al. 2001, Wiesner 2005), Belarus 

(Rizevsky et al. 2007, Semenchenko et al. 2009), Bulgaria (Dikov and Zivkov 2004, Polaçik et al. 2008), 

Georgia (Ninua and Japoshvili 2008), Germany (Borcherding et al. 2011, Brandner et al. 2013, Freyhof 2003, 

Haertl et al. 2012), Hungary (Eros et al. 2005, Guti 2006), Poland (Feldheim et al. 2009, Grabowska and 

Grabowski 2005, Grabowska et al. 2010, Kakareko et al. 2009, Kvach and Mierzejewska 2011, Witkowski and 

Grabowska 2012), Romania (Bănărescu 1964, Borcea 1934), Serbia (Brown 2009, Guti 2006, Jurajda et al. 

2005, Simonovic et al. 2006), Slovakia (Jurajda et al. 2005, Kautman 2001, Koščo et al. 2010 Ohayon and 

Stepien 2007), Turkey (Gaygusuz et al. 2007, Keskin 2010, Özulug et al. 2007, Tarkan et al. 2006), and Ukraine 

(Feldheim et al. 2009, Ohayon and Stepien 2007).

 Ohayon and Stepien (2007) suggest that based on the neogobiin traits of lacking a larval stage and a 

swimbladder (Pinchuk 1991), B. gymnotrachelus has low natural dispersal abilities.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75
87

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U √

 Grabowska (2005) suggests that hull fouling is a possible reason, along with ballast water transport, for the

relatively rapid expansion of Racer Goby range and other gobiid ranges in Europe.

 Babka gymnotrachelus has a pelvis that is fused to form a suction organ (Kottelat and Freyhof 2007), but it is 

unclear whether or not this suction organ would allow the racer goby to hitchhike on (foul) a vessel for long 

distances.

 Babka gymnotrachelus produces adhesive eggs which develop attached to stones, shells, and aquatic plants 

(Kottelat and Freyhof 2007); it is unclear whether or not this adhesion would allow Racer Goby eggs to 

hitchhike on (foul) a vessel for long distances.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 Babka gymnotrachelus is not currently found in North America.

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 

No, this species this species is rarely/never sold. 0 √

Unknown U

 Babka gymnotrachelus is a fish that is not available for purchase from any source, and there is no 

documentation of availability within the Great Lakes region (see complete reference list as lack of evidence for 

potential introduction via unauthorized intentional release).
88

 Harka and Biró (2007) mention the aquarium industry being a potential introduction pathway for PontoCaspian gobies in general. They indiscriminately cite as sources for that note and other material the following 

references: Ahnelt et al. 1998, Biró 1972, Guti 1999, Guti 2000, Lusk et al. 2000, Holčík 2003.

 In concert, this information supports that B. gymnotrachelus is no more than rarely sold and only within its 

native range as opposed to within the Great Lakes region.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Harka and Biró (2007) state that B. gymnotrachelus is not the object of recreational fisheries.

 Koščo et al. (2010) report that B. gymnotrachelus was stocked in Slovakian waters from a source in the Danube 

delta; no details on the reason(s) for the stocking are provided. 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
89

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Harka and Biró (2007) state that B. gymnotrachelus is not the object of commercial fisheries.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Babka gymnotrachelus adults or eggs are known to be transportable via shipping (Kottelat and Freyhof 2007).

 Babka gymnotrachelus dispersal in Europe has also been facilitated by shipping, in addition to shipping canal 

construction (Kalchhauser et al. 2013).

 Related taxa have been introduced via shipping/ballast water; these include the Round (Neogobius

melanostomus) and Freshwater Tubenose (Proterorhinus marmoratus) Gobies (MacIsaac et al. 2001, Neilson 

and Stepien 2009a, Stepien and Tumeo 2006), as well as the Monkey (Neogobius fluviatilis) and the Bighead 

(Neogobius kessleri) Gobies (Neilson and Stepien 2009a).

 Additionally, it has been suggested that avoiding ballast water collection during the nocturnally pelagic feeding 
90

of gobiids may further reduce their introduction to non-native waters (Hayden and Miner 2009).

 Despite regulations and suggestions, Racer Goby spread has been rapid within Europe (Grabowska et al. 2010, 

Karlson et al. 2007, Ohayon and Stepien 2007), though in this region the introduction facilitation effects of 

channelization are difficult to segregate from those of shipping/ballast water.

 Hensler and Jude (2007) and Kornis et al. (2012) have proposed that Racer Goby uptake into ballast water is 

attributable to the nocturnally pelagic gobiid feeding strategy which results in Gobies rising in the water 

column during the night to feed.

 However, current ballast water exchange (BWE) regulations require ballast tanks to be filled with ocean water 

for approximately five days; since ocean waters have salinities of around 35 ppt and since Round Goby has a 

100% mortality rate to two-day exposure to 30 ppt salinity conditions, it is predicted that these regulations may 

prevent further Round Goby inoculations (Ellis and MacIssac 2009).

 Current BWE practices are not perfect at eliminating freshwater species from ballast water, and they are 

reported to have not slowed the rate of species introduction into the Great Lakes (Ricciardi and MacIsaac 

2008, Vander Zanden et al. 2010). Kornis et al. (2010) indicate that improvement to ballast regulation is 

needed to defend against further species introductions into the Great Lakes.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 It has been spreading in and into eastern, central, and western European waters (Borcherding et al. 2011, 

Haertl et al. 2012, Kalchhauser et al. 2013, Kottelat and Freyhof 2007), both horizontally and northward 

(Harka and Biró 2007), and has reached the Baltic Sea basin (Danilkiewicz 1998).

 It has been recorded to prefer more stagnant waters (Kakareko et al. 2009) and littoral areas (Eros et al. 

2005) in rivers, lakes, reservoirs, estuaries, coastal lagoons, backwaters, and industrial harbors 

(Kalchhauser et al. 2013, Kottelat and Freyhof 2007, Wiesner 2005) in at least Austria (Ahnelt et al. 2001, 

Wiesner 2005), Belarus (Rizevsky et al. 2007, Semenchenko et al. 2009), Bulgaria (Dikov and Zivkov 2004, 

Polaçik et al. 2008), Georgia (Ninua and Japoshvili 2008), Germany (Borcherding et al. 2011, Brandner et 

al. 2013, Freyhof 2003, Haertl et al. 2012), Hungary (Eros et al. 2005, Guti 2006), Poland (Feldheim et al. 

2009, Grabowska and Grabowski 2005, Grabowska et al. 2010, Kakareko et al. 2009, Kvach and 

Mierzejewska 2011, Witkowski and Grabowska 2012), Romania (Bănărescu 1964, Borcea 1934), Serbia 

(Brown 2009, Guti 2006, Jurajda et al. 2005, Simonovic et al. 2006), Slovakia (Kautman 2001, Koščo et al. 

2010, Jurajda et al. 2005, Ohayon and Stepien 2007), Turkey (Gaygusuz et al. 2007, Keskin 2010, Özulug 

et al. 2007, Tarkan et al. 2006), and Ukraine (Feldheim et al. 2009, Ohayon and Stepien 2007).
91

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

U x 0.1 U Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 1 Confidence Level Moderate
92

Babka gymnotrachelus has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate). 

The native and introduced ranges of Babka gymnontrachelus have similar climatic and abiotic conditions 

as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species occurs in 

waters where there is ice cover in the winter and can tolerate low oxygen levels (Charlebois et al. 1997,

Reid and Orlova 2002); it is likely capable of overwintering in the Great Lakes. Babka gymnotrachelus 

feeds on soft-bodied invertebrates, which are common in the waters of the Great Lakes. Its establishment 

may be aided by the presence of Ponto-Caspian amphipods that are part of its diet (Grabowska and 

Grabowski 2005). It exhibits an extended spawning period and parental investment, which may facilitate 

the establishment of a self-sustaining population (Grabowska 2005). The models of Kolar and Lodge 

(2002) predict that Babka gymnotrachelus will quickly establish in the Great Lakes if introduced based on 

growth rate, tolerance ranges for temperature and salinity, history of invasiveness, and diet. Altered 

streamflow patterns and warming waters attributed to climate change may render the Great Lakes more 

similar to the Ponto-Caspian environment. 

In a feeding experiment, Babka gymnotrachelus exhibited aggressive behavior towards Cottus gobio, a 

European bullhead experiencing declining populations (Kakareko et al. 2013). Babka gymnotrachelus 

obtained food more quickly than Cottus gobio, and displaced it from the feeding area. Babka 

gymnotrachelus may have a competitive advantage over non-aggressive fish when foraging. If introduced 

to the Great Lakes, Babka gymnotrachelus may compete with fish that forage for invertebrates during the 

night. There is a great level of dietary overlap between Babka gymnotrachelus and native percid fish in 

the Danube River (Copp et al. 2008). However, in some cases, Babka gymnotrachelus avoids resource 

competition with native fish due to dissimilar foraging habits; in the Baltic Sea, this species exhibits 

spatial segregation while foraging to avoid competition with native fish (Grabowska and Grabowski 

2005, Kakareko et al. 2003). The opportunistic feeding strategy of Babka gymnotrachelus may aid its 

establishment. 

Although the presence of some species in the Great Lakes, such as Ponto-Caspian amphipods, may 

facilitate the establishment of Babka gymnotrachelus, the presence of other species may do the opposite. 

The round goby, a Ponto-Caspian fish that has established in the Great Lakes, is more aggressive than 

Babka gymnotrachelus and may deter its establishment (Charlebois et al. 1997). 

Babka gymnotrachelus may expand its range after introduction. It has moved from its native range and 

spread into the Danube River via the Main-Danube Canal (Haertl et al. 2012). This species has exhibited 

spontaneous range expansion from the Danube delta to waters in Slovakia (Koščo et al. 2010). This 

species expanded its range 70-100 km upstream in one year, from the Danube to the Polsko Kosovo of the 

Yantra River (Vassilev et al. 2008). In the Yantra River, Babka gymnotrachelus was the 2nd most 

abundant and 2nd most frequently found Ponto-Caspian gobiid. Babka gymnotrachelus invades habitats 

with disturbed temperature and flow regimes, such as waters altered by hydropower dams and power 

plant outlets (Harka and Bíró 2007, Kalchhauser et al. 2013).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

9
93

saturated), AND nutrient (oligotrophic-eutrophic) levels.

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Vilizzi and Copp (2012) report the climatic requirements of B. gymnotrachelus as temperate. 

 Babka gymnotrachelus is native to fresh and slightly brackish (oligo- to mesohaline) waters (within Pinchuk et 

al. 2003). Kornis et al. (2012) report a salinity tolerance range for the related Round Goby as <30 ppt. 

 Babka gymnotrachelus is routinely compared in the scientific literature as similar to the Round Goby, 

Neogobius melanostomus; the Round Goby is noted to be tolerant of a wide range of environmental conditions 

(Charlebois et al. 1997, Jude 2001), having a thermal tolerance range of -1 to 30°C (Moskal'kova 1996) and a 

critical lethal dissolved oxygen threshold of between 0.4 and 1.3 mg/L (Charlebois et al. 1997), though it is 

known to migrate from hypoxic conditions of <4 mg/L (Arend et al. 2011).

 Ponto-Caspian species in general are noted to have great adaptive capacities and tolerance to elevated water 

salinity (Ahnelt et al. 1998, Charlebois et al. 1997, Reid and Orlova 2002). 

 Babka gymnotrachelus is noted to preferentially invade habitats with disturbed temperature and flow regimes, 

such as those altered by hydropower dams and power plant outlets which both warm and calm the waters 

(Harka and Biró 2007, Kalchhauser et al. 2013).

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models, which incorporated 

five habitat needs parameters, to become established in the Great Lakes if introduced. 

 Vilizzi and Copp (2012) report that B. gymnotrachelus has a high-risk FISK (Fish Invasiveness Scoring Kit) 

score for the United Kingdom. 

 Tolerances of B. gymnotrachelus to other listed factors were not found in this literature review. 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Vilizzi and Copp (2012) report the climatic requirements of B. gymnotrachelus as temperate. 

 Babka gymnotrachelus is routinely compared in the scientific literature as similar to the Round Goby, 

Neogobius melanostomus; the Round Goby is noted to be tolerant of a wide range of environmental conditions 

(Charlebois et al. 1997, Jude 2001); Round Goby is documented to have a thermal tolerance range of -1 to 

30°C (Moskal'kova 1996) and a critical lethal dissolved oxygen threshold of between 0.4 and 1.3 mg/L 

(Charlebois et al. 1997), though it is known to migrate from hypoxic conditions of <4 mg/L (Arend et al. 2011).

 Ponto-Caspian species in general are noted to have great adaptive capacities (Ahnelt et al. 1998, Charlebois et 

al. 1997, Reid and Orlova 2002).

 Babka gymnotrachelus is noted to preferentially invade habitats with disturbed temperature and flow regimes 
94

such as those altered by hydropower dams and power plant outlets which both warm and still the waters (Harka 

and Biró 2007, Kalchhauser et al. 2013).

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models, which incorporated 

five habitat needs parameters, to become established in the Great Lakes if introduced. 

 Vilizzi and Copp (2012) report that B. gymnotrachelus has a high-risk FISK (fish Invasiveness Scoring Kit) 

score for the United Kingdom.

 Related gobiid taxa have been introduced to and have established in Great Lakes waters; these include the 

Round (Neogobius melanostomus) and Tubenose (Proterorhinus marmoratus) Gobies, as well as the Monkey 

(Neogobius fluviatilis) and the Bighead (Neogobius kessleri) Gobies (MacIsaac et al. 2001, Neilson and 

Stepien 2009a, Stepien and Tumeo 2006).

 Tolerances of B. gymnotrachelus to other listed factors were not found in this literature review.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 The broad benthivorous diet of B. gymnotrachelus in its native habitat consists of Polychaeta, Oligochaeta, 

Mollusca, Crustacea, Chironomidae larvae, fish eggs, small fishes (both larvae and juveniles), macrophytes, 

and algae (Gaygusuz et al. 2007, Grabowska and Grabowski 2005, Pinchuk et al. 2003, Smirnov 1986), and it 

exhibits an opportunistic foraging strategy and feeding plasticity (Grabowska and Grabowski 2005, 

Jaroszewska et al. 2008, Kakareko et al. 2005). 

 Its opportunistic feeding strategy may aid its establishment (Grabowska and Grabowski 2005)

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

1

 One of the potential interactions between invasive Racer Gobies and native Great Lakes species is competition 

for food (Holčík 1991). Though invasive fishes often compete for food with native fishes and eat their eggs and 

young (Witkowski and Grabowska 2012), in the Baltic basin, Racer Goby has been documented to avoid 
95

resource competition with native percid populations via spatial segregation during foraging (Grabowska and 

Grabowski 2005, Kakareko et al. 2003). Conversely, high dietary overlap was found between Racer Goby and 

native percid fishes in the Danube (Copp et al. 2008).

 In the Polish section of the Vistula River, racer gobies have been found to be predators of epifauna and 

zoobenthos, though negative impacts of invasive racer gobies to native species and ecosystem function have not 

yet been researched (Kakareko et al. 2005).

 Polaçik et al. (2008) note that Racer Goby is smaller and more delicate than are either Round Goby or Bighead 

Goby; Round Goby has been documented to be more aggressive than the Racer goby and to drive the Racer 

Goby to marginal interstitial areas (Polaçik et al. 2008). 

 Though Kolar and Lodge (2002) have predicted based on results of multiple models that Racer Goby spread 

will be fast in the Great Lakes, it is typically rare relative to other Ponto-Caspian gobiid species, such as Round 

and Bighead Goby (Jurajda et al. 2005, Kovac et al. 2009, Ohayon and Stepien 2007). Round Goby has been 

found to typically have higher distribution and abundance than even Bighead Goby (Copp et al. 2005, Jurajda 

et al. 2005, Kovac et al. 2009), and phylogenetically, Racer Goby is more closely related to Bighead Goby than 

the other three Ponto-Caspian gobiids present already in the Great Lakes (Simonovic 1999). Further, Kakereko 

et al. (2009) found low abundance (2.5%) of Racer Goby even when Round Goby and Bighead Goby were

absent from the invaded Polish Vistula River, and Ondračková et al. (2005, 2012) report that Racer Goby had 

not become abundant in the upper Danube despite its presence there for nearly a decade.

 In the Great Lakes region, round goby is currently the dominant Ponto-Caspian goby, and it is one of the most 

abundant benthic fish in the Great Lakes (Charlebois et al. 1997, Holčík 1991, Jude 1997, Jude 2001). Racer 

Goby may not obtain high density and distribution in the Great Lakes due to pre-established Round Goby 

dominance. 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6 

Moderate 3

Low 0

Unknown U

6

 Racer Gobies live four to five years in total and become sexually mature at about two years of age, producing 

small, adhesive eggs during multiple spawning periods which begin relatively early (April) in the spring (Bilko 

1968, Kottelat and Freyhof 2007) and can last into August making their reproductive period relatively long 

(Grabowska 2005). 

 Racer Gobies have been documented to have the smallest eggs among four early-spring spawning gobiid 

species in their native range (Bilko 1968).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self-fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

6
96

establishment in the Great Lakes based on these attributes)

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

9

 Racer Gobies live four to five years in total and become sexually mature at about two years of age, producing 

small, adhesive eggs during multiple spawning periods which begin relatively early (April) in the spring (Bilko 

1968, Kottelat and Freyhof 2007) and can last into August making their reproductive period relatively long 

(Grabowska 2005). Such an extended spawning period has been suggested to increase the likelihood of an 

invading species successfully establishing even despite unfavorable conditions (Grabowska 2005). 

 Males also exhibit nest-guarding behavior until eggs hatch approximately two-weeks after their laying, and this 

parental care may augment establishment (Grabowska 2005). 

 Invading Gobies tend to have other traits of altricial life history that may increase their invasion success, 

notably early maturation and increased fecundity (Grabowska 2005, Kovac et al. 2009, L’avrinčíková et al. 

2005, L’avrinčíková and Kovac 2007). In fact, invasive Racer Goby populations have demonstrated earlier 

maturation than their native counterparts (Grabowska 2005, L’avrinčíková et al. 2005); this same pattern has 

been observed for Round Gobies in both its non-native Danubian and Detroit River ranges (L’avrinčíková and 

Kovac 2007, MacInnis and Corkum 2000) as well as for Bighead Gobies in the non-native Slovak stretch of the 

Danube (Kovac et al. 2009).

 Babka gymnotrachelus exhibits an extended spawning period and parental investment, which may facilitate the 

establishment of a self-sustaining population (Grabowska 2005).

 Racer Gobies have been documented to have the smallest eggs among four early-spring spawning gobiid 

species in their native range (Bilko 1968). 

 Kolar and Lodge (2002) incorporated thirteen life-history characteristics into their models of Ponto-Caspian 

fish invasion including growth rates and egg size; their models both predict that Racer Goby will establish and 

quickly spread.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6 

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Vilizzi and Copp (2012) report the climatic requirements of B. gymnotrachelus as temperate to north temperate, 

which is the climatic condition in both the Ponto-Caspian and the Great Lakes regions (Simberloff and 

Rejmanek 2011).

 Babka gymnotrachelus is routinely compared in the scientific literature as similar to the Round Goby, 

Neogobius melanostomus; however, the Round Goby is noted to be tolerant of a wide range of environmental 
97

conditions (Charlebois et al. 1997, Jude 2001).

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models, which incorporated 

five habitat needs parameters, to become established in the Great Lakes if introduced, further suggesting 

climatic similarity between the Ponto-Caspian and Great Lakes regions. 

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (USEPA 2008, Grigorovich et al. 2003, Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Babka gymnotrachelus is noted to preferentially invade habitats with disturbed temperature and flow regimes 

such as those altered by hydropower dams and power plant outlets which both warm and still the waters (Harka 

and Biró 2007, Kalchhauser et al. 2013); the related species Round Goby is documented to have a thermal 

tolerance range of -1 to 30°C (Moskal'kova 1996) and the information provided in this assessment suggests that 

the thermal range for the Great Lakes region is somewhere within the broad range of 0 to 30°C. The 

information provided in the assessment also suggests that successfully invasive fish to the Great Lakes will be 

able to tolerate temperatures of <5°C, which is at the lower end of theRound Goby's tolerance.

 Ponto-Caspian species in general are noted to have great adaptive capacities (Ahnelt et al. 1998, Charlebois et 

al. 1997, Reid and Orlova 2002). 

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models, which incorporated 

five habitat needs parameters, to become established in the Great Lakes if introduced, further suggesting 

abiotic factor similarity between the Ponto-Caspian and Great Lakes regions. 

 Babka gymnotrachelus is routinely compared in the scientific literature as similar to the Round Goby, 

Neogobius melanostomus; however, the Round Goby is noted to be tolerant of a wide range of environmental 

conditions (Charlebois et al. 1997, Jude 2001).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U
98

6 

 In its native range, Racer Goby typically inhabits soft-bottomed river reaches with silt-clay, sand, gravel, or 

silt-clay-sand sediments (Azizova 1962, Haertl et al. 2012) including soft-bottomed backwaters (Haertl et al. 

2012, Kottelat and Freyhof 2007); it often exploits areas overgrown with aquatic vegetation for both refuge and 

foraging (Kakareko et al. 2005, Smirnov 1986).

 However, Round Goby typically inhabits coastal shallows with stony, sandy, or dreissenid shell covered 

grounds as well as areas with silty-sand or softer, well-vegetated substrates (Pinchuk et al. 2003). Due to the 

overlaps in the habitat descriptions of these two species, and that the Round Goby has already established in all 

five Great Lakes, the Great Lakes habitats available to Racer Goby invasion are likely suitable for its survival, 

development, and reproduction.

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models, which incorporated 

five habitat needs parameters, to become established in the Great Lakes if introduced, further suggesting 

habitat similarity between the Ponto-Caspian and Great Lakes regions and therefore habitat suitability within 

the Great Lakes for invading racer goby. 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9 

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 Due to warming from global climate change, we can expect the Great Lakes may improve as potential habitat 

for Ponto-Caspian gobiids (Harko and Biró 2007); northward range expansions of Ponto-Caspian gobiids and 

other fishes have been observed in Europe, and these have been posited as attributable to warming trends. 

 Babka gymnotrachelus is noted to preferentially invade habitats with disturbed temperature and flow regimes 

such as those altered by hydropower dams and power plant outlets which both warm and still the waters (Harka 

and Biró 2007, Kalchhauser et al. 2013).

 Babka gymnotrachelus is native to fresh and slightly brackish (oligo- to mesohaline) waters (Pinchuk et al. 

2003).

 Ponto-Caspian species in general are noted to have great adaptive capacities and tolerance to elevated water 

salinity (Ahnelt et al. 1998, Charlebois et al. 1997, Reid and Orlova 2002). Salt pollution of freshwaters has 

been noted to facilitate gobiid invasions (Kottelat and Freyhof 2007). This may give Racer Goby (and other 

gobies) an advantage in utilization of Great Lakes waters as habitat. 

 Babka gymnotrachelus is routinely compared in the scientific literature as similar to the Round Goby, 

Neogobius melanostomus; the Round Goby is noted to be tolerant of a wide range of environmental conditions 

(Charlebois et al. 1997, Jude 2001), and Ponto-Caspian species in general are noted to have great adaptive 

capacities (Ahnelt et al. 1998, Charlebois et al. 1997, Reid and Orlova 2002). 

 Ability of B. gymnotrachelus to adapt to or benefit from other listed effects of climate change on the Great 

Lakes freshwater ecosystem was not uncovered in this literature review. 
99

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 The broad benthivorous diet of B. gymnotrachelus in its native habitat consists of Polychaeta, Oligochaeta, 

Mollusca, Crustacea, Chironomidae larvae, fish eggs, small fishes (both larvae and juveniles), macrophytes, 

and algae (Gaygusuz et al. 2007, Grabowska and Grabowski 2005, Pinchuk et al. 2003, Smirnov 1986), and it 

exhibits an opportunistic foraging strategy and feeding plasticity (Grabowska and Grabowski 2005, 

Jaroszewska et al. 2008, Kakareko et al. 2005). 

 The Racer Goby is known to eat dreissenid mussels, which also invaded the Great Lakes from the PontoCaspian region (Gaygusuz et al. 2007). In the study done by Gaygusuz et al. (2007), the dresissenid mussels 

only made a small proportion of the Racer Goby’s diet. 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 A dependency of Racer Goby on some other critical species was not uncovered in this literature review.
100

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

7

 Racer Goby, similarly to Round Goby, is known to eat dreissenid mussels, which also invaded the Great Lakes 

from the Ponto-Caspian region (Gaygusuz et al. 2007). Dreissenid mussels are widespread and abundant in the 

Great Lakes, and they are a preferred food item of Gobies in general in areas in which the mussels are 

abundant. In the study done by Gaygusuz et al. (2007), Babka gymnnotrachelus was studied in the waters with 

high dreissenid abundance, and the mussels comprised 4% of its diet. 

 Grabowska and Grabowski (2005) mention that the presence of Ponto-Caspian amphipods may facilitate the 

establishment of Babka gymnotrachelus, which feeds on invertebrates. There are several Ponto-Caspian 

amphipods that occur in the Great Lakes.

 Ray and Corkum (1997) found that only Round Gobies larger than 7 cm in length could eat dreissenids; 

presumably a similar size threshold occurs for racer gobies. Larger Racer Gobies may incorporate these 

dreissenid mussels into their diet. Specific predictions of dreissenid mussels promoting the establishment of 

Racer Goby and specific reports of dreissenid mussels aiding the establishment of Racer Goby in other areas 

were not uncovered in this literature review, though such facilitation is suggested (Corkum et al. 2004, 

Gaygusuz et al. 2007). 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

-10% total 

points (at 
101

native ranges OR this natural enemy has low abundance in the Great Lakes) end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0 

Unknown U

U

 In both its native region and in the Great Lakes, Round Gobies are prey items of several obligate benthivores, 

facultative benthivores, and even some pelagic fishes (Corkum et al. 2004). In the Great Lakes regions, these 

Round Goby predators include Smallmouth Bass (Micropterus dolomieu), Stonecat (Noturus flavus), Burbot 

(Lota lota), and Yellow Perch (Perca flavens) as well as Freshwater Drum (Aplodinotus grunniens), Walleye 

(Stizostedion vitreum), and Lake Sturgeon (Acipenser fulvescens) (Corkum et al. 2004). Racer Gobies may be 

expected to be prey for these same species in the Great Lakes, though the literature review conducted for this 

assessment did not uncover data as to how effectively this predation might control an invading racer goby 

population. 

 Racer Gobies are known hosts for several European parasites including: the trematode Cryptocotyle concavum

and the acanthocephalan Pseudoechinorhynchus (Najdenova 1974, Smirnov 1986), the monogenean 

Gyrodactylus proterorhini (Mierzejewska et al. 2011, Mierzejewska et al. 2012), the digenean Bucephalus 

polymorphus (Kvach and Mierzejewska 2011), the ciliate Trichodina domerguei (Mierzejewska 2007), and 

others (Ondračková et al. 2012). 

 Invading populations of Racer Gobies have been documented to have lower parasite species richness than is the 

case for populations in their native range (Ondračková et al. 2012); similar findings exist for Round Gobies 

(Corkum et al. 2004). Pronin et al. (1997) notes that low parasite loads are also found in Great Lakes 

populations of Dreissena polymorpha, a primary food source for Great Lakes gobies. 

 Kvach and Stepien (2008) note that North American parasites seem poorly adapted to use gobiids as hosts.

 The distributions of the previously named parasites, specifically their presences in the Great Lakes, were not 

uncovered in this literature review. Additionally, Great Lakes native species that can serve as hosts for known 

parasites of racer goby were not uncovered in this literature review. Finally, little was uncovered in this 

literature review as to which if any North American parasites can infect invading Racer Goby populations. 

Therefore, the role of parasites in Racer Goby establishment and spread is unclear. 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Both the Round and Tubenose Goby populations across the Great Lakes have been documented to have high 

genetic diversity similar to those in their native ranges; this suggests that low/no founder effects were 

experienced by these invading populations and that instead both invasions were the result of introductions of 

many diverse individuals, either via large inocula or frequent small inocula (Brown and Stepien 2009, Stepien 

and Tumeo 2006). Additionally, Round Goby population comparisons between Lake St. Clair and Lake Eire 

reveal significant genetic differences suggestive of separate founding events and thus frequent inocula (Dillon 

and Stepien 2001). 

 Similar results have been discovered for genetic variation of dreissenid mussel populations in the Great Lakes, 
102

giving further support to that the numbers of introduction events of species transported in ballast water from 

the Ponto-Caspian region are, or were at least at one point, high (Stepien et al. 2002, Stepien and Tumeo 

2006).

 To a greater extent than has been observed for the Great Lakes, invading goby populations throughout Europe 

tend to have lower genetic diversity than is the case for populations in their native region (Stepien and Tumeo 

2006); this makes sense considering the ability of Gobies to migrate via connected waterways, which tends to 

produce founder effects, at least over the short term. However, Round Goby invasion of the Baltic Sea has also 

been reported to be via multiple inoculations (Kornis et al. 2012). 

 Not enough information was uncovered in this literature review to determine accurately either the frequency or 

size of racer goby inoculation.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Racer Goby has been spreading in and into eastern, central, and western European waters (Borcherding et al. 

2011, Haertl et al. 2012, Kalchhauser et al. 2013, Kottelat and Freyhof 2007), both horizontally and northward 

(Harka and Biró 2007), and it has reached the Baltic Sea basin (Danilkiewicz 1998). 

 Based on the information above, while racer goby has not spread beyond Europe at this time, it has spread into 

the Baltic Sea drainage basin from the Ponto-Caspian basin. Based on this, its spread to a new but proximate 

drainage basin may be characterized as a semi-wide distribution. 

17) How rapidly has this species spread by natural means or by human activities once introduced 

to other locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in 

introduced ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its 

introduced ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 Kolar and Lodge (2002) report that B. gymnotrachelus is predicted by both of their models to become 
103

established in the Great Lakes if introduced and to have a fast rate of spread. 

 Racer Goby spread around Europe has been reported to be occurring at an "explosive" rate over the past 

decade; this same rapid spread rate has been attributed to Round Goby (Grabowska et al. 2010, Karlson et al. 

2007). Other studies have similarly reported the Racer Goby (Ohayon and Stepien 2007) and Round Goby 

(Harka and Biró 2007) spread rates in Europe to be quick over about the past two decades.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment 

and/or spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There 

are no reported cases of this species adapting or avoiding current measures. These 

measures are highly effective in preventing the establishment and spread of this 

species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the

species. (There are few reported cases of this species adapting or avoiding current 

measures used to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There 

are many reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of 

this species

0

Unknown U

U

 Chemicals targeting benthic fishes have been used to attempt to control Round Goby population size and thus 

spread ability in the Great Lakes (Schreier et al. 2008). Trapping using Round Goby specific pheromones and 

commercial exploitation of Round Goby for fish meal and oil markets have also been proposed as potential 

control measures (Corkum et al. 2008, Kornis et al. 2012). It is unknown if these control strategies would be 

effective against the related racer goby.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 107

>100 High Adjustments

B. Critical species A*(1- 0%) 107

51-99 Moderate C. Natural enemy B*(1- 0%) 107

Control measures C*(1- 0%) 107

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level
104

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

Current research on the potential for environmental impacts to result from Babka gymnotrachelus 

if introduced to the Great Lakes is inadequate to support proper assessment.

Babka gymnotrachelus feeds on dreissenid mussels that may contain toxins and ingests sediment that act 

as sinks for contaminants while foraging in benthic environments. These ingested contaminants may 

undergo biomagnification at higher trophic levels, but there is not enough evidence to conclude whether 

this would occur if Babka gymnotrachelus were introduced to the Great Lakes. 

Babka gymnotrachelus is a host for several European parasites including the trematode Cryptocotyle 

concavum, the acanthocephalan Pseudoechinorhynchus (Najdenova 1974, Smirnov 1986), the 

monogenean Gyrodactylus proterorhini, the digenean Bucephalus polymorphus, and the ciliate 

Trichodina domerguei (Kvach and Mierzejewska 2011, Mierzejewska et al. 2011, Mierzejewska et al. 

2012, Mierzejewska et al. 2014). Dreissena polymorpha is an intermediate host for Bucephalus 

polymorphus and are eaten by Gobies. Pike and Perch that prey on Gobies may be infected. Evidence 

suggest that populations of Racer Gobies and Round Gobies that are introduced outside their native 

ranges have lower parasite species richness than in their native ranges (Corkum et al. 2004, Ondračková 

et al. 2012). In the Great Lakes, Dreissena polymorpha exhibits low parasite loads (Pronin et al. 1997). 

If introduced, Babka gymnotrachelus may compete with native Great Lakes species for food (Holčík 

1991). As a non-native fish in the Danube River, Babka gymnotrachelus exhibits a strong dietary overlap 

with some native fishes (Copp et al. 2008). In a laboratory experiment, Babka gymnotrachelus exhibited 

competitive and aggressive behavior towards Cottus gobio when feeding (Kakareko et al. 2013). Cottus 

bairdi, a similar cottid species, is present in the Great Lakes; however there is insufficient evidence to 

conclude whether Babka gymnotrachelus would outcompete Cottus bairdi if introduced to the Great 

Lakes. In the Baltic basin, Babka gymnotrachelus avoids resource competition with native fishes through 

spatial segregation while foraging (Grabowska and Grabowski 2005, Kakareko et al. 2003). Babka 

gymnotrachelus exhibits opportunistic feeding habits and plasticity (Grabowska and Grabowski 2005). 

Thus, it is not clear whether Babka gymnotrachelus would outcompete native species if introduced to the 

Great Lakes. 

Babka gymnotrachelus can potentially be preyed on by Great Lakes fishes if introduced; however, there is 

not enough research to determine if this species has the potential to alter predator-prey relationships. The 
105

round goby Neogobius melanstomus has altered food web structure in the Great Lakes (Corkum et al. 

2004). 

Dreissenids are native to the Ponto-Caspian and increased water clarity and altered nutrient cycling 

regimes (Qualls et al. 2007). If Babka gymnotrachelus feeds on a substantial amount of dreissenid 

mussels, water clarity and nutrient cycling regimes may be impacted, but it is unknown whether this 

impact is positive or negative.

There is little or no evidence to support that Babka gymnotrachelus has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Babka gymnotrachelus poses a threat to water quality. There is no evidence 

that this species negatively impacts infrastructure, economic sectors, recreational activities and associated 

tourism, or the aesthetic appeal of the areas it inhabits.

While foraging in benthic environments, Babka gymnotrachelus ingests sediments that are a sink for 

contaminants. Babka gymnotrachelus feeds on dreissenid musssels and may result in the bioaccumulation 

of contaminants to higher trophic levels (Kornis et al. 2012). However, the link between Babka 

gymnotrachelus and bioaccumulation of toxins has not been demonstrated. 

Current research on the potential for beneficial impacts to result from Babka gymnotrachelus if 

introduced to the Great Lakes is inadequate to support proper assessment.

Babka gymnotrachelus feed on the invasive dreissenid mussels (Gaygusuz et al. 2007), but its ability as 

an effective biological control agent is unknown. This fish is not commercially valuable and is an 

insignificant part of the fishing industry in the Caspian basin (Azizova 1962, Pinchuk et al. 2003). Babka 

gymnotrachelus is not recreationally or medically valuable. It has not been indicated that Babka 

gymnotrachelus can be used to improve water quality. It does not have significant positive ecological 

impacts.

POTENTIAL ENVIRONMENTAL IMPACT

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0

Unknown U √

 As a benthivore, Racer Goby ingests sediment, and toxins deposited in sediments are therefore also ingested by 

these fish; Goby consumption of dreissenids has also been suggested to facilitate bioaccumulation of 

contaminants to upper food web levels (Kornis et al. 2012). The toxins accumulated by the Racer and other 

Gobies are transferred up the food chain when they are eaten by larger fish, birds, or water snakes (Corkum et 

al. 2004, Kornis et al. 2012).

 Racer Gobies are known hosts for several European parasites including the trematode Cryptocotyle concavum

and the acanthocephalan Pseudoechinorhynchus (Najdenova 1974, Smirnov 1986), the monogenean 

Gyrodactylus proterorhini (Mierzejewska et al. 2011, Mierzejewska et al. 2012), the digenean Bucephalus 
106

polymorphus (Kvach and Mierzejewska 2011), the ciliate Trichodina domerguei (Mierzejewska 2007), and

others (Ondračková et al. 2012). 

 Bucephalus polymorphus also uses Dreissena polymorpha as a host for the early components of its life cycle, 

and these mussels are the source of its cercariae, which infect the Gobies (Kvach and Mierzejewska 2011); 

Gobies eaten by Pike or Perch carry the parasite to them, its definitive hosts (Kvach and Mierzejewska 2011). 

Racer goby presence could facilitate the infection of pike and/or perch in Great Lakes waters. 

 Invading populations of racer gobies have been documented to have lower parasite species richness than is the 

case for populations in their native range (Ondračková et al. 2012); similar findings exist for round gobies 

(Corkum et al. 2004). Pronin et al. (1997) notes that low parasite loads are also found in Great Lakes 

populations of Dreissena polymorpha, a primary food source for Great Lakes gobies. 

 The distributions of the previously named parasites, specifically their presences in the Great Lakes, were not 

uncovered in this literature review. Additionally, Great Lakes native species that can serve as hosts for known 

parasites of Racer Goby were not uncovered in this literature review. Therefore, the role of Racer Goby in nonindigenous parasite introduction, establishment, and spread within the Great Lakes is unclear.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0

Unknown U √

 One of the potential interactions between invasive Racer Gobies and native Great Lakes species is competition 

for food (Holčík 1991); B. gymnotrachelus in its native habitat has a broad benthivorous diet which consists of 

Polychaeta, Oligochaeta, Mollusca, Crustacea, Chironomidae larvae, fish eggs, small fishes (both larvae and 

juveniles), macrophytes, and algae (Gaygusuz et al. 2007, Grabowska and Grabowski 2005, Pinchuk et al. 

2003, Smirnov 1986), and it exhibits an opportunistic foraging strategy and feeding plasticity (Grabowska and 

Grabowski 2005, Jaroszewska et al. 2008, Kakareko et al. 2005).

 Though invasive fishes often compete for food with native fishes and eat their eggs and young (Witkowski and 

Grabowska 2012), in the Baltic basin, Racer Goby has been documented to avoid resource competition with 

native percid populations via spatial segregation during foraging (Grabowska and Grabowski 2005, Kakareko 

et al. 2003).

 Conversely, high dietary overlap was found between Racer Goby and native percid fishes in the Danube (Copp 

et al. 2008). In the Polish section of the Vistula River, Racer Goby has been found to be a predator of epifauna 

and zoobenthos, though negative impacts of invasive Racer Gobies to native species and ecosystem function 

have not yet been researched (Kakareko et al. 2005).

 In the Great Lakes, the related species Round Goby has been linked to the decline of native Great Lakes fish 

including several Sculpin, Darters, and Perch (Corkum et al. 2004, Jude et al. 1995, Kornis et al. 2012). The 

declines have been documented to be due to Round Gobies eating native fish larvae and fry (Chotkowski and 

Marsden 1999, Corkum et al. 2004) as well as interfering with native fish spawning and displacement through 

habitat competition (Dubs and Corkum 1996, Janssen and Jude 2001, Kornis et al. 2012). 

 In a laboratory experiment, Babka gymnotrachelus exhibited competitive and aggressive behavior towards 

Cottus gobio when feeding (Kakareko et al. 2013). Cottus bairdi, a similar cottid species, is present in the Great 

Lakes; however, there is insufficient evidence to conclude whether Babka gymnotrachelus would outcompete 

Cottus bairdi if introduced to the Great Lakes.

E3) Does it alter predator-prey relationships? 
107

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0

Unknown U √

 Round Goby invasion has resulted in alterations to food web structure via diet shifts among Goby predators 

(Corkum et al. 2004). In both its native region and in the Great Lakes, Round Gobies are prey items of several 

obligate benthivores, facultative benthivores, and even some pelagic fishes (Corkum et al. 2004). In the Great 

Lakes regions, these Round Goby predators include Smallmouth Bass (Micropterus dolomieu), Stonecat 

(Noturus flavus), Burbot (Lota lota), and Yellow Perch (Perca flavens) as well as Freshwater Drum 

(Aplodinotus grunniens), Walleye (Stizostedion vitreum), and Lake Sturgeon (Acipenser fulvescens) (Corkum 

et al. 2004). Racer Gobies may be expected to be prey for these same species in the Great Lakes, though the 

literature review conducted for this assessment did not uncover data as to the potential food web impacts of an 

invading racer goby population.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 No documentation of Racer or Round Gobies having genetic effects on native populations was uncovered in this 

literature review; see the complete reference list as lack of evidence for such an impact. 

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 

Unknown U √

 Racer Goby is known to eat dreissenid mussels, which also invaded the Great Lakes from the Ponto-Caspian 

region (Gaygusuz et al. 2007). Dreissenid mussels are widespread and abundant in the Great Lakes, and, 

though few native organisms eat them, they are a preferred food item of gobies in general (the study specifically 

included racer goby among the studied goby species) in areas in which the mussels are abundant (Gaygusuz et 

al. 2007). As dreissenid mussels have impacted Great Lakes water clarity and nutrient cycling regimes (Hecky 
108

et al. 2004, Johengen et al. 1995, Karatayev et al. 2002, Leach 1993), Racer Goby addition to the Great Lakes 

has the potential to decrease dreissenid mussel abundance and therefore to impact water clarity and nutrient 

cycling regimes.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 

Unknown U √

 Babka gymnotrachelus in its native habitat has a broad benthivorous diet which consists of Polychaeta, 

Oligochaeta, Mollusca, Crustacea, Chironomidae larvae, fish eggs, small fishes (both larvae and juveniles), 

macrophytes, and algae (Gaygusuz et al. 2007, Grabowska and Grabowski 2005, Pinchuk et al. 2003, Smirnov 

1986); since macrophytes and algae are among its food resources, it has the potential to alter macrophyte and 

phytoplankton communities.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √
109

Not significantly 0 

Unknown U

 As a benthivore, Racer Goby ingests sediment; toxins deposited in sediments are therefore also ingested by 

these fish. Goby consumption of dreissenids has also been suggested to facilitate bioaccumulation of 

contaminants to upper food web levels (Kornis et al. 2012). The toxins accumulated by the Racer and other 

Gobies are transferred up the food chain when they are eaten by larger fish, birds, or water snakes (Corkum et 

al. 2004, Kornis et al. 2012). This feeding activity thereby has the ability to move contaminants formerly 

relatively sequestered in the sediments into food webs.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 No documentation of Racer Goby causing infrastructure damage effects was uncovered in this literature 

review; see the complete reference list as lack of evidence for such an impact. 

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U
110

 No specific documentation of Racer Goby inhibiting recreational activities and/or associated tourism in areas it 

inhabits was uncovered in this literature review; see the complete reference list as lack of evidence for such an 

impact. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

 No specific documentation of Racer Goby altering perceptions of aesthetic or natural value of areas it inhabits 

was uncovered in this literature review; see the complete reference list as lack of evidence for such an impact. 

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 

Unknown U √

 Racer Goby is known to eat dreissenid mussels, which also invaded the Great Lakes from the Ponto-Caspian 

region (Gaygusuz et al. 2007). Dreissenid mussels are widespread and abundant in the Great Lakes, and, 

though few native organisms eat them, they are a preferred food item of gobies in general (the study specifically 
111

included Racer Goby among the studied Goby species) in areas in which the mussels are abundant (Gaygusuz 

et al. 2007). However, the ability of Racer Goby to act as an effective biological control agent is unknown.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 Pinchuk et al. (2003) states fishermen in the Dneister-Dniper estuaries dislike B. gymnotrachelus as a thin fish 

and thus it comprises <10% of the commercial Goby fishing industry in that area; similarly, low (<4%) 

representation is presented to exist for Caspian fisheries (Azizova 1962). No information is given here as to the 

representation of the Goby fishing industry as compared to the rest of the fishing industry.

 This information supports that B. gymnotrachelus is no more than rarely sold and only so within its native 

range as opposed to within the Great Lakes region; therefore, it is deemed not to be a commercially valuable 

species.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 Harka and Biró (2007) mention the aquarium industry being a potential introduction pathway for PontoCaspian gobies in general. They indiscriminately cite as sources for that note and other material the following 

references: Ahnelt et al. 1998, Biró 1972, Guti 1999, Guti 2000, Lusk et al. 2000, Holčík 2003.

 No specific documentation of Racer Goby being of recreational value was uncovered in this literature review; 

see the complete reference list as lack of evidence for such an impact. 

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 No specific documentation of Racer Goby being of medicinal or research value was uncovered in this literature 

review; see the complete reference list as lack of evidence for such an impact. 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?
112

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 No specific documentation of Racer or Round Gobies removing toxins or pollutants from water columns or 

otherwise increasing water clarity was uncovered in this literature review; see the complete reference list as 

lack of evidence for such an impact.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0

Unknown U √

 Round Goby invasion has resulted in alterations to food web structure via diet shifts among Goby predators 

(Corkum et al. 2004). In both its native region and in the Great Lakes, Round Gobies are prey items of several 

obligate benthivores, facultative benthivores, and even some pelagic fishes (Corkum et al. 2004). In the Great 

Lakes regions, these Round Goby predators include Smallmouth Bass (Micropterus dolomieu), Stonecat 

(Noturus flavus), Burbot (Lota lota), and Yellow Perch (Perca flavens) as well as Freshwater Drum 

(Aplodinotus grunniens), Walleye (Stizostedion vitreum), and Lake Sturgeon (Acipenser fulvescens) (Corkum 

et al. 2004). Racer Gobies may be expected to be prey for these same species in the Great Lakes.

Beneficial Effect Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
113

Scientific Name: Benthophilus stellatus 

Sauvage, 1874

Common Name: Stellate Tadpole-Goby, Starry Goby

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Benthophilus stellatus has a low probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Benthophilus stellatus does not currently occur near waters connected to the Great Lakes basin. This 

species is not known to hitchhike or foul. Benthophilus stellatus is not commercially cultured, stocked, or 

sold in the Great Lakes region. This species has neither been observed fouling or in ballasts of ships 

entering the Great Lakes or in ports in direct trade with the Great Lakes. This species has a temperature 

range of 4 - 20°C and can tolerate salinity levels up to 12 ppt (Kottelat and Freyhof 2007, Whitehead et 

al. 1986). Thus, ballast water exchange regulations that require filling ballast tanks with full-strength sea 

water may limit the introduction of this species to the Great Lakes. Benthophilus stellatus is predicted to 

be introduced to the Great Lakes via ballast water (Kolar and Lodge 2002, Ricciardi and Rasmussen 

1998). Benthophilus stellatus may be introduced to the Great Lakes via ships declaring “No Ballast on 

Board” (NOBOB), which are exempt from ballast water exchange. The majority of ships entering the 

Great Lakes are NOBOB vessels and 43% of these ships contain residual water with less than 10‰ 

salinity (Johengen et al. 2005). In the study, the temperature of the residual water from the vessels 

sampled ranged from -0.7 to 23.9°C; thus B. stellatus is likely to survive the salinity and temperature of 

ballast water from most NOBOB vessels.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
114

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 There is no record of Benthophilus stellatus occurring beyond the Black and Caspian basins (Neilson and 

Stepien 2009b).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U 

 There is no relevant research regarding Benthophilus stellatus’s hitchhiking or fouling ability.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
115

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 There is no mention in peer reviewed papers of Benthophilus stellatus having any commercial value. A 

thorough search of possible sales of this species for any means returned no results. 

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 There is no mention in peer reviewed papers of Benthophilus stellatus having any commercial value. A 

thorough search of possible stocking yielded no results.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
116

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There is no mention in peer reviewed papers of Benthophilus stellatus having any commercial value. A 

thorough search of possible culturing yielded no results.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Benthophilus stellatus has been shown to be tolerant of brackish water which could support the theory of it 

being transported through ballast water (Mordukhaĭ-Boltovskoĭ 1964).
117

 Benthophilus stellatus has been reported to have a temperature range of 4°C - 20°C, and tolerate salinity levels 

up to 12 ppt. This includes brackish water in shallow lagoons (Kottelat and Freyhof 2007, Whitehead et al. 

1986). It has also been recorded in the coastal regions of seas where the dissolved oxygen levels ranged 8-10 

mg/L (Snigirov et al. 2012). 

 Ballast water exchange regulations that require filling ballast tanks with full-strength sea water (35 ppt 

salinity) may limit the introduction of this species to the Great Lakes.

 Benthophilus stellatus is predicted to be able to invade the Great Lakes in ballast water (Kolar and Lodge 

2002, Ricciardi and Rassmussen 1998).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Benthophilus stellatus is native to the Black Sea, Sea of Azov, and Caspian rivers and estuaries (e.g., Dniester). 

It also occurs in the Volga River and many middle Volga reservoirs (e.g., Kuybyshev, Saratov, Cheboksary)

(Neilson and Stepien 2009b).

 In 2011, it was recorded for the first time in the upper Dnieper River basin in Belarus (Rizevsky et al. 2013).

 It is also present in the Kiev reservoir on the Dnieper River (Witkowski and Grabowska 2012).

 Benthophilus stellatus is not yet known to be in areas from which shipping traffic to the Great Lakes originates.

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely
118

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Benthophilus stellatus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

The native and introduced ranges of Benthophilus stellatus have similar climatic and abiotic conditions as 

the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). There are various 

habitats throughout the Great Lakes basin that match the requirements of Benthophilus stellatus 

(Johengen et al. 2000). This species prefers waters that are colder and less saline; thus, increased water 

temperatures and salinization due to climate change may make the Great Lakes a less suitable 

environment for it. Benthophilus stellatus has a generalist diet and feeds on invertebrates and small fishes 

(Kottelat and Freyhof 2007, Whitehead et al. 1986). It is likely that B. stellatus will find an appropriate 

food source if introduced to the Great Lakes. The presence of nonindigenous crustaceans and small fishes 

from the Ponto-Caspian may aid its establishment, but not to a significant degree (USGS 2012). Large 

piscivorous fish may prey on B. stellatus. There is potential for predators to inhibit the establishment of 

this species; however, similar Gobies such as the Round Goby (Neogobius melanostomus) have 

established despite predation pressure (Kornis et al. 2013, Whitehead et al. 1986). Relative to Gobies 

within and outside of its subfamily, B. stellatus has an average fecundity (Whitehead et al. 1986).

Benthophilus stellatus has extended its range beyond the Ponto-Caspian basin. The construction of 

reservoirs has resulted in the introduction of B. stellatus to the Volga and Don Rivers (Ermolin 2010, 

Ivancheva and Ivanchev 2008, Luzhnyak and Korneev 2006). Once established in a region, it has spread 

moderately fast, accelerated by human activities. A year after its discovery, the abundance of B. stellatus 

was high (Yashanin 1982). 

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 8 Low

Total Unknowns (U) 0 Confidence Level High
119

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Benthophilus stellatus has been reported to survive in temperatures of 4°C - 20°C, and salinity levels up to 12 

ppt. This includes brackish water in shallow lagoons (Kottelat and Freyhof 2007, Whitehead et al. 1986). It has 

also been recorded in the coastal regions of seas where the dissolved oxygen levels ranged 8-10 mg/L (Snigirov 

et al. 2012).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Benthophilus stellatus has been shown to occur in waters that do reach 4°C and in deeper waters where light 

may not be abundant (Kottelat and Freyhof 2007, Whitehead et al. 1986). However, there is no record of it 

surviving in low dissolved oxygen levels. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0
120

Unknown U

8

 Benthophilus stellatus has a benthic diet and feeds on mollusks, crustaceans, insect larvae, and small fishes 

(Kottelat and Freyhof 2007, Whitehead et al. 1986).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

4

 There is no reported data on the competitive ability of B. stellatus. Although other species in family Gobiidae 

such as the Round Goby (Neogobius melanostomus) have outcompeted species outside of their natural range 

extensively (Kornis et al. 2013).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Benthophilus stellatus has an average fecundity when compared with other gobies within and outside of its 

subfamily (Whitehead et al. 1986).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self-fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

9
121

based on these attributes)

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Benthophilus stellatus possesses no known reproductive strategies that would aid in its establishment. 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The seas and basins where B. stellatus naturally occurs has similar seasonality to that of the Great Lakes basin 

but is generally colder (Matishov et al. 2008).

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8
122

 Benthophilus stellatus occurs in the streams and seas of the Black and Azov sea basins. It can occupy either 

brackish or fresh water with various substrates (Whitehead et al. 1986). 

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 There are various habitats throughout the Great Lakes basin that match the requirements of B. stellatus

(Johengen et al. 2000). It generally occupies muddy rivers and the shallow regions of lakes and seas with 

various substrates and water temperatures (Kottelat and Freyhof 2007, Whitehead et al. 1986). This species 

occupies similar habitat to that of the Round Goby (Neogobius melanostomus) which has spread throughout 

various Great Lakes basin habitats (Kornis et al. 2013).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

0

 Benthophilus stellatus occupies water that is cool with low salinity (Kottelat and Freyhof 2007, Whitehead et 

al. 1986). While the Great Lakes ecosystem currently could possibly support it, any increase in water 

temperature or salinity would make the ecosystem less suitable.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?
123

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Benthophilus stellatus is a generalist feeding on various benthic organisms, all of which are very prevalent 

throughout the Great Lakes (Kottelat and Freyhof 2007, Whitehead et al. 1986). 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by B. stellatus at any life stage (Whitehead et al. 1986).

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9
124

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

1

 Various species that are considered non-indigenous to the Great Lakes such as crustaceans and small fishes 

could serve as potential food sources for B. stellatus but they would not facilitate its spread any more than 

naturally occurring species (USGS 2012).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-20%

 Being a small fish, B. stellatus could be targeted by any number of larger piscivorous fish as prey but most 

likely not preferentially or enough to stop its establishment in the Great Lakes basin. Benthophilus stellatus is 

similar in size and habitat selection to the Round Goby (Neogobius melanostomus), which has not been stopped 

by predation (Kornis et al. 2013, Whitehead et al. 1986).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6
125

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Benthophilus stellatus has been identified as having the potential of being introduced through transoceanic 

shipping, but there have been no recorded cases of this actually happening (USEPA 2008). 

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 There have been limited “invasions” of B. stellatus past its native range. It naturally occurs in various lakes, 

rivers, and seas throughout the Ponto-Caspian steppe (Whitehead et al. 1986). There have been documented 

reports of it spreading through the Volga and Don with the creation of reservoirs (Ermolin 2010, Luzhnyak and 

Korneev 2006, Ivancheva and Ivanchev 2008).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 Benthophilus stellatus has spread into various tributaries and reservoirs near its natural occurrence. In the 

Saratov Reservoir, fish abundance increased from very low abundance in 1969-1985 to low abundance in 1986-

1995 (low abundance maintained in 1996-2007) (Ermolin 2010). In the Saratov Reservoir, numbers increased 

from one individual caught in a fry trawl in 1974 to 146 individuals caught in 1976 (Ermolin 2010). In the 

middle stretch of the Oka River (Russia), abundance increased from rare in 1991-2000 to scarce in 2001-2006 
126

(Ivancheva and Ivanchev 2008). This spread has been accelerated by human activities such as the construction 

of reservoirs and dams. 

 A year after its discovery, the abundance of Benthophilus stellatus was high (Yashanin 1982).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There have been no reported instances of introductions by transoceanic shipping, the proposed method for 

introduction into the Great Lakes. No methods known to prevent establishment or spread of this species are 

present in this ecosystem.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 80

>100 High Adjustments

B. Critical species A*(1- 0%) 80

51-99 Moderate C. Natural enemy B*(1- 20%) 64

Control measures C*(1- 0%) 64

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low
127

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Benthophilus stellatus if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Benthophillus stellatus poses a threat to 

other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Benthophilus stellatus has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Benthophilus stellatus poses a threat to human health or water quality. There 

is no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Benthophilus stellatus has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Benthophilus stellatus can be used for the control of other organisms or 

improving water quality. Other gobies such as the Round Goby (Neogobius melanostomus) are known to 

eat nonindigenous dreissenid mussels that are invasive in the Great Lakes, and may reduce their 

populations somewhat (Baker and Li 2015). Dreissenid mussels are responsible for altering the water 

quality in the Great Lakes (Mida et al. 2010), so reducing their populations may also have an effect on 

water quality. However, there are no records suggesting that this particular species, Benthophilus 

stellatus, can act as a biological control agent for dreissenid mussels. There is no evidence to suggest that 

this species is commercially, recreationally, or medically valuable. Other Goby species are in the market 

for the aquaculture trade, but there are no records that suggest that B. stellatus is commercially valuable 

(Whitehead et al. 1986). It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 
128

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 There is no record of Benthophilus stellatus posing a hazard or threat to the health of native species.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 The competitive abilities of Benthophilus stellatus are not well known. 

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 There is no record of B. stellatus having an effect on predator prey relationships.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 There is no record of B. stellatus affecting native populations genetically.
129

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 There is no record of B. stellatus having an effect on water quality.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 There is no record of B. stellatus having an effect on the physical components of the ecosystem.

Environmental Impact Total 0

Total Unknowns (U) 5

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT
130

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There is no record of B. stellatus posing any threat to human health. 

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There is no record of B. stellatus damaging infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There is no record of B. stellatus having an effect on the water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There is no record of B. stellatus having an effect on markets or economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 6
131

and tourism 

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no record of B. stellatus inhibiting recreational activities.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no record of B. stellatus diminishing the perceived aesthetic or natural value.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √
132

Unknown U

 There is no record of B. stellatus acting as a biological control agent for non indigenous organisms. Other 

Goby species from similar regions with similar diets, such as the Round Goby (Neogobious melanostomus), 

have been speculated to curb nonindigenous mussel populations (Baker and Li 2015). 

S2) B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 There is no record of B. stellatus being commercially valuable, although some markets do exist for larger Goby 

species and others are featured in the aquaculture trade (Whitehead et al. 1986).

S3) B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is no record of B. stellatus having any recreational value.

S4) B4) Does the species have some medicinal or research value (i.e. outside of research geared towards 

its control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 There is no record of B. stellatus having any medical or research value.

S5) B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There is no record of B. stellatus having an effect on the water quality. Other Goby species from similar regions 

with similar diets, such as the Round Goby (Neogobious melanostomus), have been speculated to curb 
133

nonindigenous mussel populations (Baker and Li 2015). This affect on the mussel population could 

hypothetically alter water quality but probably not significantly.

S6) B6) Does the species have a positive ecological impact outside of biological control (e.g., increases 

the growth or reproduction rates of other species, fills an important gap in the food web, supports the 

survival of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 There is no record of B. stellatus having any ecological impact.

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
134

Scientific Name: Carassius carassius

Linnaeus, 1758

Common Name: Crucian Carp, Golden Carp, Gibele, Prussian Carp, English Carp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Carassius carassius has a low probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway of introduction: Unauthorized Intentional Release

Although Crucian Carp have been reported in in Illinois and Texas, these populations are considered 

possible misidentifications. Identification is difficult due to this species’ similarity to Goldfish (Carassius 

auratus) and Common Carp (Cyprinus carpio) (USGS 2015). This species is farmed worldwide, and 

occasionally kept in water gardens. The similarity to other cyprinids increases the risk of accidental 

transportation or introduction.

While no negative impacts have been reported from Crucian Carp, other cyprinids have had negative 

impacts due to their broad environmental tolerance and diet.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
135

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Although Crucian Carp are available from aquarium stores online (e.g., from Cob House in the United 

Kingdom, or as “Gold Crucian Carp” from Kingworld Aquarium), they were not found for sale in the US.

 There is also a significant potential for misidentification (Tarkan et al. 2010) and sale of Crucian Carp as or 

with Goldfish (Carassius auratus).
136

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 Fish identified as Crucian Carp have been found for sale only in the United Kingdom and Asia.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
137

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
138

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.1 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
139

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Carassius carassius has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Carassius carassius can survive in a wide variety of water conditions and are remarkably hardy. They are 

restricted to freshwater and are omnivores. This makes them a potential invader to the Great Lakes. 

Carassius carassius are an open substrate spawner with eggs that adhere to twigs and macrophytes 

(Holopainen et al. 1997) so they use aquatic weeds for spawning (egg attachment) (FAO 2013a). The 

Great Lakes region has many habitat types that would meet the requirements for Carassius carassius eggs 

to attach to. 

This species spread occurs primarily through human release, which has been rapid due to 

confusing/mistaken taxonomic identification, as well as its common occurrence as a pet in Europe.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 C. carassius is remarkably hardy; they can live for hours out of water (Muus and Dahlstrom 1978).

 This species is tolerant of anoxic and very low oxygen conditions (Schofield et al. 2015).

 This species can tolerate water temperatures up to 38°C (Horoszewicz 1973).

 This species can tolerate pH of 4 (Holopainen and Ikari 1992).

 This species can survive in waters with temperatures below 0°C, and can even survive for several days with 

frozen integument (Schofield et al. 2013) or burrowed into mud (Holopainen et al. 1997).

 C. carassius is restricted to freshwater.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 3
140

it is not known as an overwintering species)

Unlikely 0

Unknown U

9

 C. carassius is tolerant of anoxic and very low oxygen conditions (Schofield et al. 2013).

 This species can survive in waters with temperatures below 0°C, and can even survive for several days with 

frozen integument (Schofield et al. 2013) or burrowed into mud (Holopainen et al. 1997).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 This species is an omnivore that feeds on organic detritus, filamentous algae, small benthic animals, and pieces 

and seeds of aquatic weeds. The fry/larvae feed on zooplankton (FAO 2013a).

 Planktonic and benthic invertebrates form the dominant part of diet in all size classes; plant material, 

phytoplankon and detritus are also commonly found (Holopainen et al. 1997).

 Dominant items in this species’ diet can vary, e.g., molluscs, chironomid larvae, or cladocera (Uspenskaja 

1953).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Smaller eutrophic lakes or nutrient-rich, vegetated bays may have considerable numbers of carp (Hamrin 

1979), though not likely to dominate. This species does best in monospecific ponds (Holopainen et al. 1997).
141

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Relative fecundity of C. carassius has been reported as 119.2 (Copp et al. 2010) and 129.2 (Holopainen et al. 

1997).

 Relative fecundity for Carassius auratus has been reported at 251.7 (Copp et al. 2010) and 270 (Tarkan et al. 

2010).

 Relative fecundity of Carassius gibelio has been reported at 78-251 (Leonardos et al. 2008).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0
142

Unknown U

8

 This species is native to local areas of England, but has spread throughout England as a result of introduction. 

It is native to the fresh waters of the North Sea and Baltic Sea basins across the northern part of France and 

Germany to the Alps and throughout the Danube basin, then eastwards to Siberia (Wheeler 2000).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 This fish is found often in smaller lakes or ponds (Wheeler 2000), which differ from the Great Lakes. Otherwise, 

this species tolerates a wide variety of abiotic conditions, and the Great Lakes are within this range of 

conditions.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 C. carassius uses aquatic weeds for spawning (egg attachment) (FAO 2013a).

 This species is an open substrate spawner with eggs that adhere to twigs and macrophytes (Holopainen et al. 

1997).

 This species does not have any habitat restrictions for normal adult life.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9
143

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 C. carassius is very adaptable, and has already been shown to tolerate temperatures of up to 38°C 

(Horoszewicz 1973). 

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 C. carassius is an omnivore that naturally feeds on organic detritus, filamentous algae, small benthic animals, 

and pieces and seeds of aquatic weeds. The fry/larvae feed on zooplankton (FAO 2013a).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in -80% total 
144

the Great Lakes and is not likely to be introduced points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 C. carassius is vulnerable to predation, however, it has morphological adaptations (rapid growth to larger size) 

to avoid predation in waters with piscivores (Holopainen et al. 1997).
145

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 The main vector (aquarium release) is likely to be infrequent as C. carassius is not as common as the 

congeneric Goldfish (Carassius auratus).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

3

 C. carassius is native to local areas of England, but has been introduced in other areas of England (Wheeler 

2000).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0
146

Unknown U

6

 C. carassius spread occurs primarily through human release, which has been rapid due to confusing/mistaken 

taxonomic identification, as well as its accidental occurrence as a pet in Europe (due to misidentification with 

Carassius auratus) (Wheeler 2000).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 89

>100 High Adjustments

B. Critical species A*(1- 0%) 89

51-99 Moderate C. Natural enemy B*(1- 10%) 80.1

Control measures C*(1- 0%) 80.1

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low
147

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

Current research on the potential for environmental impacts to result from Carassius carassius if 

introduced to the Great Lakes is inadequate to support proper assessment.

While there is some evidence that C. carassius may have a negative environmental impact through food 

competition and disturbance of surface sediment, there is uncertainty as to the magnitude of these impacts 

and whether they will occur in the Great Lakes.

There is little or no evidence to support that Carassius carassius has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

Carassius carassius has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

Moderate beneficial impact may occur through its value as a bait fish or though its culture for animal 

protein.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted 6 
148

threatened/endangered species or caused critical reduction, extinction, behavioral 

changes including modified spawning behavior) on one or more native populations

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 C. carassius is likely to be a superior competitor for food when resources are limited (Fraser and Adams 1997).

 Smaller eutrophic lakes or nutrient-rich, vegetated bays may have considerable numbers of carp (Hamrin 

1979), though this speicies does best in monospecific ponds (Holopainen et al. 1997).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 C. carassius may be a food source for piscivores such as pike, leading to hyperpredation (Fraser and Adams 

1997).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 C. carassius hybridizes with a non-native species, Cyprinus carpio (Schofield et al. 2015). These hybrids have 

rapid growth, high resistance to polluted hypoxic water and high production of fry with excellent survival 

qualities (Skora and Erdmanski 1985). Others report these hybrids have low fertility (Hänfling et al. 2005).

 C. carassius also hybridizes with non-native species C. gibelio and C. auratus (Lusk et al. 2010).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

6
149

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 Benthic feeding and disturbance of surface sediment may have an important effect on nutrient cycling and 

trophic dynamics (Holopainen et al. 1997).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native 

species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and 

resulting adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 C. carassius disturbs surface sediment (Holopainen et al. 1992).

Environmental Impact Total 0

Total Unknowns (U) 4

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.
150

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
151

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6
152

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 C. carassius is a superb bait fish, but has low value as food in Europe (Holopainen et al. 1997).

 Very high growth rate in eutrophic waters makes C. carassius a potential producer of high quality animal 

protein for fodder or human food by aquaculture (Holopainen et al. 1997).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This species makes a superb bait fish (Holopainen et al. 1997).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 

Unknown U √

 A great potential for laboratory culture and wide range of feeding habits make Crucian Carp a suitable fish for 

species for routine ecotoxicologial assays (Holopainen et al. 1997).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 
153

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
154

Scientific Name: Channa argus

Cantor, 1842

Common Name: Northern Snakehead

Synonyms: Amur Snakehead, Eastern Snakehead, Ocellated Snakehead, Snakehead, Ophicephalus argus 

Cantor, 1842, Ophicephalus pekinensis Basilewsky, 1855 

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Low

Hitchhiking/fouling: Low

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Unknown

Escape from commercial culture: Low

Transoceanic shipping: Low

Channa argus has a moderate probability of introduction to the Great Lakes (Confidence level: 

Moderate).

Potential pathway of introduction: Dispersal, Unauthorized Intentional Release

According to the Northern Snakehead Working Group (NSWG) of the United States Fish and Wildlife 

Service, Channa argus (Northern Snakehead) likely arrived in United States waters by importation for the 

live food fish market (NSWG 2014). Unauthorized intentional release from this trade, as was the case in 

the founding individuals of the Crofton pond population in Maryland, continues to be the major 

mechanism for introduction (Courtenay and Williams 2004). The Northern Snakehead has become widely 

popular in ethnic markets and restaurants over the last two decades, such that this species comprised the 

greatest volume and weight of all live Snakehead species imported into the United States until 2001 

(Courtenay and Williams 2004, NSWG 2014). In Canada, Herborg et al. (2007) identified two watersheds 

in the Toronto area along Lake Ontario to be at the greatest risk for northern snakehead introduction from 

the live fish trade; the Rideau River watershed and Cedar Creek watershed (between Lake Erie and Lake 

St. Clair) posed additional vectors for introduction. Snakeheads’ resilient nature reportedly makes them 

more desirable than carps for ceremonial release, and some interest in recreational fishing may also exist 

(Mendoza-Alfaro et al. 2009, NSWG 2014).

Recognized as a highly injurious species, importation and cross-border transport of Northern Snakehead 

was prohibited in the United States by a 2002 listing under the Lacey Act and has been subsequently 

banned in Ontario. Nevertheless, cases of Northern Snakehead for sale in areas where possession is illegal 

are not uncommon (NSWG 2014). Accidental release during transport of live fish is possible, but its 

probability is unknown (Mendoza-Alfaro et al. 2009).
155

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0

Unknown U

 In 2004, a single specimen of Northern Snakehead was collected in Burnham Harbor, IL on Lake Michigan 

(NSWG 2014); no subsequent reports have been made and this introduction is considered to have failed.

 Although the Northern Snakehead can survive up to four days out of the water, overland migration is only 

possible for juveniles (Courtenay and Williams 2004).

 The closest established Northern Snakehead populations with respect to the Great Lakes are in Piney Creek, a 

tributary of the Arkansas River, AR, within the Mississippi River basin; the Potomac River basin, MD and VA; 

the Delaware River basin, PA and NJ; and on Long Island, NY, near the source of Flushing Creek (USGS 

2012).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25 

√

Unknown U

 Piney Creek is a tributary of the Arkansas River, which flows into the Mississippi River more than 100 km from 

the Great Lakes.

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U
156

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Before importation and cross-border transport of Snakehead was prohibited by the Lacey Act in 2002 (also 

banned in Ontario), this fish had been available for sale in New York, Missouri, Georgia, California, 

Massachusetts, and Ontario.

 In Canada, Herborg et al. (2007) identified two watersheds in the Toronto area along Lake Ontario to be at the 

greatest risk for northern snakehead introduction from the live fish trade; the Rideau River watershed and 

Cedar Creek watershed (between Lake Erie and Lake St. Clair) posed additional vectors for introduction.

 Quickly attaining large size and lacking the colors of other snakehead species, northern snakehead is not a 

desirable aquarium fish (Courtenay and Williams 2004).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Northern Snakehead has been widely cultured in Asian countries, particularly China, and its popularity as a 

food fish in American and Canadian ethnic markets has risen in the last decades. Snakeheads’ resilient nature 

reportedly also makes them more desirable than carps for ceremonial release (Mendoza-Alfaro et al. 2009).

 Recognized as a highly injurious species, importation and cross-border transport of Northern Snakehead was 

prohibited in the United States by a 2002 listing under the Lacey Act; possession of live Snakehead is banned in 

42 United States states and the Canadian province of Ontario (includes all Great Lakes states and provinces 

except Quebec; Courtenay and Williams 2004, IISG 2011, GLPANS 2012). Nevertheless, cases of Northern 

Snakehead for sale in areas where possession is illegal are not uncommon (NSWG 2014).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE
157

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U √

 Law enforcement officials and natural resource managers in the Potomac River have observed a growing 

interest in fishing for Snakehead by the local population (NSWG 2014).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

√

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Although cross-border transport is prohibited, accidental release during illegal transport of live fish is 

possible; the probability of this pathway into the Great Lakes is unknown (Mendoza-Alfaro et al. 2009).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

Score x 0.25
158

organisms within 20 km of the Great Lakes basin.

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
159

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in the United States, but not the Great Lakes

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.25 25 Low

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

U x 0.25 U Unknown

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 1 Confidence Level Moderate
160

Channa argus has a moderate probability for establishment if introduced to the Great Lakes 

(Confidence level: Moderate)

Channa argus is established in Arkansas, Maryland, New York, Pennsylvania, and Virginia, but is not 

established in California, Illinois, Florida, Massachusetts, or North Carolina, where only a few individual 

fish have been collected. In March 2009, eradication of the population in Little Piney Creek, Arkansas 

drainage was attempted through the application rotenone to more 700 km of creeks, ditches, and 

backwaters (Holt and Farwick 2009); however specimens were collected in Piney Creek later that year, 

indicating eradication had not been complete (L. Holt, pers. comm.). The Northern Snakehead was 

eradicated from the Crofton pond in Maryland where it was first established, but this species is well 

established in the Potomac River and several of its tributaries in Virginia and Maryland. The population 

in Catlin Creek, New York was also treated with rotenone. Although young fish were found, the status of 

the Philadelphia population is uncertain. Officials believe fish may have gotten into the lower Schuylkill 

River and Delaware River in Pennsylvania and see no practical means to eradicate them.

The Northern Snakehead’s broad physiological tolerances, capacity to overwinter—including survival 

under ice, varied and flexible diet throughout at all life history stages, predatory and competitive nature, 

high fecundity, and parental investment in offspring, give this species a suite of favorable attributes for 

establishment once introduced. Northern Snakehead can adapt to a wide range of aquatic habitats and has 

been predicted to have high environmental suitability in the northern United States and southern Canada, 

including abundant potential habitat in the Great Lakes (Herborg et al. 2007, Mendoza-Alfaro et al. 2009, 

NSWG 2014). 

Historical imports to the United States have come from a wide range of source populations, including 

Nigeria, Thailand, Indonesia, China, and Korea (NSWG 2014). Orrell and Weigt (2005) found seven 

unique mitochondrial DNA haplotypes, none of which were shared, among the five United States

populations they surveyed, indicating separate introduction events and source populations for each. Such 

high genetic diversity among introduced populations can promote their establishment and spread (Lee 

2002, Sanders 2010).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

9

 Northern Snakehead has broad physiological tolerances. While it prefers maximum air temperatures of 5-16°C 

(Herborg et al. 2007), this species has a wider latitudinal range and temperature tolerance (0 to >30°C, 

including frost days) than other Snakehead species (Dukravets and Machulin 1978, Okada 1960). Upper 

salinity tolerances have been experimentally determined to be between 15 and 18 ppt (at temperatures of 15-
161

24°C; NSWG 2014). This species is an obligate air-breather, so it is able to survive in poorly oxygenated 

waters.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 The metabolism and oxygen demand of the Northern Snakehead is reduced at low temperatures, allowing it to 

survive extended periods of ice cover (Frank 1970).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Post-larvae Northern Snakehead feed on plankton; juveniles on small crustaceans and fish larvae; and, adults 

on fishes, frogs, crustaceans, and aquatic insects (Courtenay and Williams 2004).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
162

Unknown U

9

 The voracious predatory nature of Northern Snakehead is an indication of superior competitive abilities. Its 

introduction into the Great Lakes would likely affect other populations of fish and invertebrates through direct 

predation, competition for food resources, and alteration of food webs (Courtenay and Williams 2004, NSWG 

2014).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Although fecundity for this species is very high, there are variations among individuals from different regions. 

Northern Snakehead fecundity can range from 22,000-51,000 in its native range (Amur basin; Nikol'skii 1956) 

to 28,600-115,000 in an introduced population (Syr Dar'ya basin, Turkmenistan/Uzbekistan; Dukravets and 

Machulin 1978).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Northern Snakehead has demonstrated plasticity in timing of reproduction and rapid larval growth rates. These 

characteristics are likely to contribute to this species’ success in new environments and limit significant 

invasion control (Landis et al. 2011). Additionally, both parents guard their nests from predation and continue 

to guard the hatched fry for several additional weeks (Courtenay and Williams 2004, Landis and Lapointe 

2010).
163

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species can adapt to a wide range of aquatic habitats and has been predicted to have high environmental 

suitability in the northern USA and southern Canada (Herborg et al. 2007, Mendoza-Alfaro et al. 2009, NSWG 

2014).

8) How similar are other abiotic factors (e.g., pollution, water temperature, salinity, pH, nutrient levels, 

currents) that are relevant to the establishment success of this species in the native and introduced ranges 

to those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

U

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Although this species prefers to live in stagnant shallow (< 2 m) ponds or swamps with mud substrate or 

aquatic vegetation and slow muddy streams, it also occurs in canals, reservoirs, lakes, and rivers (Courtenay 
164

and Williams 2004). Adult females build circular floating nests from clipped aquatic plants and release their 

pelagic, nonadhesive, buoyant eggs on top (Landis and Lapointe 2010).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 C. argus can adapt to a wide range of aquatic habitats and tolerate temperatures up to 30°C (Courtenay and 

Williams 2004).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 C. argus fry initially feed on zooplankton, before moving on to a diet of small insects and crustaceans (e.g., 

cladocerans, copepods, small chironimid larvae). Juveniles may feed on small fish, including Goldfish 

(Carassius spp.) and Roach (Rutilis spp.; Courtenay and Williams 2004). As an adult, the Northern Snakehead 

is a voracious feeder (Okada 1960), and its diet may include fish up to 33 percent of its body length (Courtenay 

and Williams 2004). Adult prey items include Loach (Cobitis spp.), Bream (Abramis spp.), Carp (Cyprinus 

carpio), Perch (Perca fluviatilis), Zander (Sander spp.), Grass Carp (Ctenopharyngodon idella), various 

catfishes, crayfish, dragonfly larvae, beetles, and frogs (Courtenay and Williams 2004, Okada 1960).
165

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

0

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 The success of young juvenile Northern Snakeheads in the Potomac River has been attributed to shelter and 

feeding among dense aggregations of the nonindigenous plant Hydrilla verticillata (Landis and Lapointe 2010).
166

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Although all juvenile fish are susceptible to predation by larger fish, the Northern Snakehead does not have any 

preferential predators in the Great Lakes.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

3
167

proximity to each other)

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Channa argus has been introduced and established in western Asia and eastern Europe. In the United States, 

there are reproducing populations in Arkansas and the Potomac River, VA (Courtenay and Williams 2004, 

NSWG 2014).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

4

 Although the Northern Snakehead can survive up to four days out of the water, overland migration is only 

possible for juveniles (Courtenay and Williams 2004). The rounded body of the adult Northern Snakehead is not 

as conducive to overland migration as observed in other, more horizontally flattened Snakehead species.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard
168

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 96

>100 High Adjustments

B. Critical species A*(1- 0%) 96

51-99 Moderate C. Natural enemy B*(1- 0%) 96

Control measures C*(1- 0%) 96

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Moderate

Beneficial: Moderate

Current research on the potential for environmental impacts to result from Channa argus if 

introduced to the Great Lakes is inadequate to support proper assessment.

Despite its high potential for outcompeting native species for food resources and altering food-web 

dynamics (Courtenay and Williams 2004, NSWG 2014) due to its voracious predatory nature, wide 

environmental tolerance, and varied diet, there is little published on the ecological effects of introduced 

northern snakehead. However, it has been predicted that Northern Snakehead could substantially modify 

the ecosystem balance of waters with low diversity and low abundance of native predatory species 

through top-down mechanisms (Courtenay and Williams 2004, Landis et al. 2011, NSWG 2014). 

Among the eight forage fishes consumed by Northern Snakehead in the Potomac River, Banded Killifish 

(Fundulus diaphanus), Bluegill (Lepomis macrochirus), Pumpkinseed (L. gibbosus), and White Perch 

(Morone americana) were most commonly observed (NSWG 2014). Petr and Mitrofanov (1998) noted 

that an immigration of fish species to Turkmenistan from Uzbekistan, which included C. argus 

warpachowskii, caused an observed decline in the number of native species. Furthermore, Northern 

Snakehead could highly risk threatened and endangered species. Of all the taxa listed as endangered or 

threatened in United States aquatic habitats, 16 amphibians, 115 fishes, and 5 of the 21 crustaceans 
169

(surface dwelling crayfish and shrimp), would be the most likely to be affected (Courtenay and Williams 

2004).

Northern Snakehead, like many other fishes, is a carrier of non-native parasites and other pathogens 

(including myxosporidians, cestodes, trematodes, nematodes, acanthocephalans, and copepods; 

Bykhovskaya-Pavlovskaya et al. 1964), which could potentially have a significant environmental impact 

on Great Lakes fauna. Working with researchers in Japan, the United States Fish and Wildlife Service 

(USFWS) identified nematodes observed in Northern Snakehead captured from the Potomac River as 

eustrongylides, native to United States waters; these are typically carried by the killifish the Snakehead 

feeds on (NSWF 2006). Additionally, Chiba et al. (1989) noted that C. argus (along with C. maculata) 

introduced parasites to Japan, but failed to provide details of the parasites involved or fish species 

affected.

Channa argus has the potential for moderate socio-economic impact if introduced to the Great 

Lakes.

In the Potomac River, the habitat and feeding preferences of northern snakehead appear to overlap with 

that of the recreationally important largemouth bass (Micropterus salmoides). Northern Snakehead has 

been observed to consume killifish, an important prey for white and yellow perch, as well as white perch 

itself (Odenkirk and Owens 2005), posing a potential impact on commercial and recreational fisheries.

Although there is little information on parasitic or disease transmission in the scientific literature 

available, it is known that a related species, C. striata, has been identified as an intermediate host for the 

helminth parasite that causes gnathostomiasis, a disease that can affect humans. It is still unknown if other 

Snakehead species may serve as an intermediate host for larvae of this parasite (Courtenay and Williams 

2004).

The cost of control or eradication, should northern snakehead be introduced to the Great Lakes, could be 

high. Estimated costs associated with the Crofton, MD eradication effort (limited to a small pond) were 

over $100,000, and may be financially impossible for larger water bodies (Courtenay and Williams 2004).

Channa argus has the potential for moderate beneficial effects if introduced the Great Lakes.

Northern Snakehead possesses commercial importance in both native and introduced ranges. It is not only 

the most important snakehead cultured in China (with most culture activities centered in the Yangtze 

basin), but it also became commercially valuable in the deltaic area of Syrdarya after its introduction and 

subsequent naturalization (Aladin et al. 2008, Courtenay and Williams 2004). In addition, this species has 

historically been imported for sale in live-food fish markets, was previously cultured in Arkansas, and has 

been the most widely available snakehead in the United States (Courtenay and Williams 2004).

Channa argus is frequently in recreational and cultural activities of some communities. After becoming 

established in the Potomac River, natural resource managers and law enforcement officials noted and 

became concerned with the growing interest in fishing for Snakehead by the local population (NSWG 

2014). In addition, some cultures utilize this species during prayer release (freeing captive animals into 

the wild as a ceremonial petition) (NSWG 2014).

Though not contributing uniquely significant research value, Chen et al. (2009) purified and characterized 

pepsinogens and pepsins from northern snakehead In order to investigate the digestive capacity of toplevel predators.
170

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Northern Snakehead, like many other fishes, is a carrier of non-native parasites and other pathogens (including 

myxosporidians, cestodes, trematodes, nematodes, acanthocephalans, and copepods; Bykhovskaya-Pavlovskaya 

et al. 1964), which could potentially have a significant environmental impact on Great Lakes fauna.

 Working with researchers in Japan, the United States Fish and Wildlife Service (USFWS) identified nematodes 

observed in Northern Snakehead captured from the Potomac River as eustrongylides, native to United States

waters; these are typically carried by the killifish the Snakehead feeds on (NSWG 2014).

 Additionally, Chiba et al. (1989) noted that C. argus (along with C. maculata) introduced parasites to Japan, 

but failed to provide details of the parasites involved or fish species affected.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Due to its voracious predatory nature, wide environmental tolerance, and varied diet, C. argus has a high 

potential of outcompeting native species for food resources and altering food-web dynamics (Courtenay and 

Williams 2004; NSWG 2014). Although little evidence of the ecological effects of introduced Northern 

Snakeheads can be found in the scientific literature, Petr and Mitrofanov (1998) noted that an immigration of 

fish species to Turkmenistan from Uzbekistan, which included C. argus, caused an observed decline in the 

number of native species.

 Competition for habitat is only likely to be significant during spawning seasons (Courtenay and Williams 2004).

E3) Does it alter predator-prey relationships?

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

6
171

the food web)

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 There is little published analysis of the ecological effects of introduced Northern Snakehead. However, it has 

been predicted that Northern Snakehead could substantially modify the ecosystem balance of waters with low 

diversity and low abundance of native predatory species through top-down mechanisms (Courtenay and 

Williams 2004, Landis et al. 2011, NSWG 2014). 

 Among the eight forage fishes consumed by Northern Snakehead in the Potomac River, Banded Killifish 

(Fundulus diaphanus), Bluegill (Lepomis macrochirus), Pumpkinseed (L. gibbosus), and White Perch (Morone 

americana) were most commonly observed (NSWG 2014). 

 Furthermore, Northern Snakehead could further impact threatened and endangered species. Of all the taxa 

listed as endangered or threatened in United States aquatic habitats (16 amphibians, 115 fishes, and 5 of 21 

crustaceans), those found in the Great Lakes would be the most likely species to be affected (Courtenay and 

Williams 2004).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 Because Snakeheads do not occur naturally in the United States, hybridizing or interbreeding with native fishes 

is not likely (Courtenay and Williams 2004).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?
172

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 The Northern Snakehead is not likely to cause habitat degradation or destruction (Courtenay and Williams 

2004). 

Environmental Impact Total 1

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 There is little information on parasitic or disease transmission by this species available in the scientific 

literature. However, it is known that a related species, Channa striata, has been identified as an intermediate 

host for the helminth parasite that causes gnathostomiasis, a disease that can affect humans. It is still unknown 

if other Snakehead species may serve as an intermediate host for larvae of this parasite (Courtenay and 

Williams 2004).
173

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1 

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 In the Potomac River, northern snakehead has been observed to consume Killifish, an important prey for White 

and Yellow Perch, as well as White Perch itself (Odenkirk and Owens 2005), posing a potential impact on 

commercial and recreational fisheries.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 In the Potomac River, the habitat and feeding preferences of Northern Snakehead appears to overlap with that 

of the recreationally important Largemouth Bass (Micropterus salmoides). Northern Snakehead has been 

observed to consume Killifish, an important prey for White and Yellow perch, as well as White perch itself 

(Odenkirk and Owens 2005), posing a potential impact on commercial and recreational fisheries.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 6
174

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U
175

 Northern Snakehead possesses commercial importance in both native and introduced ranges. It is not only 

the most important snakehead cultured in China (with most culture activities centered in the Yangtze 

basin), but it also became commercially valuable in the deltaic area of Syr Darya after its introduction and 

subsequent naturalization (Aladin et al. 2008, Courtenay and Williams 2004).

 In addition, this species has historically been imported for sale in live-food fish markets, was previously 

cultured in Arkansas, and has been the most widely available Snakehead in the United States (Courtenay 

and Williams 2004).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Channa argus is frequently used in recreational and cultural activities of some communities. After becoming 

established in the Potomac River, natural resource managers and law enforcement officials noted and became 

concerned with the growing interest in fishing for Snakeheads by the local population (NSWG 2014). 

 In addition, some cultures utilize this species during prayer release (freeing captive animals into the wild as a 

ceremonial petition) (NSWG 2014).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 In order to investigate the digestive capacity of top-level predators, Chen et al. (2009) purified and 

characterized pepsinogens and pepsins from Northern Snakehead.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 
176

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
177

Scientific Name: Clupeonella cultriventris

Nordmann, 1840

Common Name: Black Sea Sprat, Caspian Sea Sprat, Azov Kilka, Common Kilka, Tyulka

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Clupeonella cultriventris has a low probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Clupeonella cultriventris is native to the Ponto-Caspian region (Fazli et al. 2007). This species is not 

known to hitchhike or foul vessels. Clupeonella cultriventris is not stocked, commercially cultured, or 

sold in the Great Lakes region. Although this species occurs in waters from which shipping traffic to the 

Great Lakes originates, it does not currently occur in ports that have direct trade connections with the 

Great Lakes and has not been observed in ballast tanks of ships entering the Great Lakes. It may be able 

to survive ballast tank environment due to its high salinity tolerance (Fazli et al. 2007).

In the Rybinsk Reservoir, Clupeonella cultriventris has been locally introduced to the Dneiper, Volga, 

and Kama rivers after the construction of dams (Kiyashko et al. 2006). It has not been introduced further 

north towards the Volga-Baltic canal system (Kiyashko et al. 2012). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 √
178

not mobile or able to be transported by wind or water.

Unknown U

 Clupeonella cultriventris currently inhabits the Ponto-Caspian region, including Iranian and Turkish waters of 

the Caspian Sea (Fazli et al. 2007).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25 

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √
179

Unknown U

 An Internet search for C. cultriventris for purchase (“for sale”) suggests that this species in not sold. 

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 An Internet search provided no information that would suggest C. cultriventris is anywhere in the Great Lakes 

region.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100
180

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Clupeonella cultriventris is not currently cultured in Great Lakes region. 

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This species is euryhaline and is found in salinities up to 36‰ (Fazli et al. 2007).

 This species occurs in waters with temperatures of 2.6 - 26°C, but its optimal temperature range is 16 - 22 °C 

(Aseinova 2003, Stakenas 2011).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with Score x 0.5
181

the Great Lakes (e.g., Baltic Sea).

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Clupeonella cultriventris has successfully established in the Rhine River due to opening of Rhine-Main-Danube 

canal that connects to the Black Sea (Ricciardi and MacIsaac 2000).

 Clupeonella cultriventris spread to the Volga reservoirs to the Rybinsk Reservoir, but was unable to move 

further north through the Volga-Baltic canal system (Kiyashko et al. 2012).

 Clupeonella cultriventris is found in the Black Sea (northwestern parts), Sea of Azov, and Caspian Sea, as well 

as most of the affluent rivers of the area, reaching as far as 60 km inland. It is also found in Lake Palaeostomi 

(Bulgaria), the Bay of Feodosiya (Romania), and Lake Apolyont (Turkey) (Whitehead 1985).

 As such, it does not appear that C. cultriventris currently exists at ports in direct trade with the Great Lakes.

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 8 Low

Total Unknowns (U) 0 Confidence Level High
182

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Clupeonella cultriventris has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: High). 

The native and introduced ranges of Clupeonella cultriventris have similar climatic and abiotic conditions 

as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Clupeonella 

cultriventris can tolerate freshwaters and salinities up to 36 % (Fazli et al. 2007). It occurs in waters with 

temperatures of 2.6-26 °C and is oxyphilic (Aseinova 2003); thus this species is somewhat likely to be 

capable of overwintering in the Great Lakes, but its ability to do so is limited by the oxygen level in the 

water. Climate change may make the Great Lakes more suitable for Clupeonella cultriventris. Its optimal 

temperature range is 16-22°C and may benefit from warmer water temperatures. It is oxyphilic so it may 

benefit from shorter duration of ice cover. If introduced, it is probable that Clupeonella cultriventris will 

find an appropriate food source of copepods and cladocerans. Compared to closely related species, 

Clupeonella cultriventris has a flexible diet (Fazli et al. 2007). In its native range, Clupeonella 

cultriventris is eaten by piscivorous fish such as salmon and sturgeons (Karimzadeh 2011). Lake sturgeon 

and several types of salmon are present in the Great Lakes (MIDNR 2014). Lake sturgeon is a benthic 

feeder and occurs in the Great Lakes in low abundances (Hayes and Caroffino 2012), so it is unlikely to 

prey on this species. Clupeonella cultriventris has a shorter breeding season than Bigeye Kilka 

(Clupeonella grimmi), which reproduces year round (Karimzadeh et al. 2010). The average absolute 

fecundity of Clupeonella cultriventris 25,400 eggs (Opisov and Kiyashko 2006), which is greater than the 

absolute fecundity of Anchovy Kilka (Clupeonella engrauliformis) that is 12625 ± 5533 eggs (Janbaz et 

al. 2012). The fecundity of Clupeonella cultriventris may be greater in fresh waters such as the Great 

Lakes.

Clupeonella cultriventris dominated pelagic fish communities of the Volga and Sheksna reservoirs 

(Slynko et al. 2002) and continues to spread northwards as average water temperatures rise with the 

progression of climate change (Kiyashko et al. 2006). The lack of competitors and low predation pressure 

in these reservoirs as well as eutrophication, retarded flow, and the creation of habitats suitable for pelagic 

fish may have contributed to their spread and dominance in the fish communities. The dominance of this 

species in the reservoirs of the Volga River may have suppressed native fish populations (MordukhaĭBoltovskoĭ 1979b, Ricciardi and Rasmussen 1998). In locations where Clupeonella cultriventris is very 

abundant, its diet is similar to the diets of native species, with a feeding similarity index greater than 50% 

(Kiyashko et al. 2007). On the other hand, where this species is less numerous, its feeding similarity with 

native species is less than 40%. It may compete with planktivorous fish for zooplankton.
183

Models predicted that Clupeonella cultriventris will spread at a fast rate and have negative impacts if 

introduced (Kolar and Lodge 2002). The spread of this species throughout the Dniester, Danube, Dnieper, 

Don, Kuban, Volga, and Ural rivers is thought to be facilitated by the construction of reservoirs 

(Kiyashko et al. 2006). Clupeonella cultriventris completely colonized the Uglich and Ivan’kov Rivers 

within a span of 12 years (Kiyashko et al. 2006).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Clupeonella cultriventris is known to have broad salinity and temperature tolerance. It is considered oxyphillic 

(Aseinova 2003).

 This species is euryhaline. It can tolerate freshwaters and salinities up to 36% (Fazli et al. 2007).

 It is found in waters that have an annual average temperature of 12°C (Karimzadeh et al. 2010) and can 

tolerate water temperatures down to 3°C (Kas’yanov 2009). It occurs in waters with temperatures ranges of 

2.6-26°C, and its optimal temperature is 16-22°C (Stakenas 2011). Spawning and development occurs at 10-

25°C in the pelagic zone (Kiyashko et al. 2006). It is considered eurythermal (Ricciardi and Rasmussen 1998).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Clupeonella cultriventris is known to be an overwintering species, however oxygen requirements may limit 

overwintering (Aseinova 2003).

3) If this species is a heterotroph, how would the flexibility of its diet be described?
184

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Clupeonella cultriventris is a euryphagous species, eating wide variety of copepods, cladocerans, and rotifers 

(Aseinova 2003). 

 Clupeonella cultriventris feeds during the day (Kiyashko et al. 2007).

 Clupeonella cultriventris feeds on zooplankton and its diet is relatively diverse relative to other kilka species 

(Fazli et al. 2007).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Kolar and Lodge (2002) notes that a previous qualitative assessment suggests that Tyulka (Clupeonella 

cultriventris) may have negative effects on the Great Lakes if introduced.

 Kolar and Lodge (2002) predicted that Clupeonella cultriventris would spread quickly and be a nuisance if 

introduced to the Great Lakes. 

 It dominates the pelagic planktivorous fish assemblages in almost all reservoirs of the Volga cascade, including 

the Rybinsk Reservoir. The northward expansion of kilka is still continuing. In 2001 it dominated fish 

communities from Sheksna Reservoir to Beloye Lake (Slynko et al. 2002). Eutrophication, retarded flow, and 

formation of vast open sites suitable for these pelagic fish contributed to their dispersal and naturalization 

(Kiyashko et al. 2006). In addition, the nearly complete absence of competitors and low predator pressure may 

have been partially responsible for their spread and their dominance in the communities.

 Where this species is very abundant, it feeds on the same planktonic organisms as native species, and their 

feeding similarity indices are greater than 50%. When this species is less numerous, feeding similarity with 

native species is less than 40% (Kiyashko et al. 2007).

 It has become very abundant in the Volga River reservoirs, contributing to the decline in native populations 

(Mordukhaĭ-Boltovskoĭ 1979b, Ricciardi and Rasmussen 1998).
185

5) How would the fecundity of this species be described relative to other species in the same taxonomic

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Clupeonella cultriventris reaches maturity after one year (Kiyashko et al. 2006).

 Reproduction occurs from March to September at temperatures of 10-25°C (Fazli et al. 2007, Karimzadeh et al. 

2010, Kiyashko et al. 2006) and peaked in April-May. It has a shorter reproduction period than the bigeye kilka 

(throughout the year).

 In the Rybinsk Reservoir, it begins spawning in early June and ends in late July, peaking in early July (Opisov 

and Kiyashko 2006). It reaches maturity at age one+ years at 49 mm. Males live up to 3.5 years. Females live 

longer. Females produce at least two batches of eggs during the spawning period. Absolute fecundity range 

from 4.2 to 66.7 thousand eggs and averages at 25.4 thousand eggs. Fecundity increases in freshwater. 

 The Anchovy Kilka, Clupeonella engrauliformis, has an average absolute fecundity of 12625 ± 5533 eggs 

(Janbaz et al. 2012).

 It produces more eggs than anchovy kilka but spawns for a shorter time period than Bigeye Kilka. The number 

of eggs produced by Bigeye Kilka is unknown.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 Based on egg size, amount of eggs laid per fish, and early maturity it is likely that these will all give C. 

cultriventris a reproductive advantage. (Kiyashko et al. 2006, Opisov and Kiyashko 2006).

 Fish that produce a large number of small eggs may be more likely to establish than other fish (Kolar and 

Lodge 2002).

ENVIRONMENTAL COMPATIBILITY
186

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). 

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Although C. cultriventris is native to brackish waters of the Ponto-Caspian, it has established in freshwaters of 

the Rhine River (Ricciardi and MacIsaac 2000).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

 Abiotic factors and climatic conditions of the native and introduced ranges of C. cultriventis are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0
187

Unknown U

6

 Clupeonella cultriventris is a pelagic fish that inhabits coastal areas shallower than 50-70 m (Fazli and 

Besharat 1998). It is oxyphillic, but can tolerate a wide range of temperatures (Aseinova 2003).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

5

 Its optimal temperature range is 16 -22°C (Aseinova 2003). It may not be able to tolerate low dissolved oxygen 

levels (Aseinova 2003) created by ice cover, so shorter ice cover duration may benefit this species. Climate 

change may make the Great Lakes climate more similar to the Ponto-Caspian region (USEPA 2008).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 Clupeonella cultriventris feeds on wide variety of copepods, cladocerans, and rotifers (Aseinova 2003). These 

can be found in the Great Lakes. 

 Compared to closely related species, Clupeonella cultriventris has a flexible diet (Fazli et al. 2007).
188

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by C. cultriventris.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There are no Great Lakes species known to facilitate the establishment of C. cultriventris.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
189

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Major predators of adult C. cultriventris include larger fish (Aseinova 2003), but these are unlikely to be a 

significant deterrent to species establishment.

 In the Caspian Sea, C. cultriventris is an important part of the diet of commercially valuable fish such as 

sturgeon and salmon (Karimzadeh 2011).

 Lake Sturgeon is threatened (in low abundance) in the Great Lakes (Hayes and Caroffino 2012).

 Chinook Salmon was introduced to the Great Lakes and its populations are maintained by stocking programs 

(MIDNR 2014).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Clupeonella cultriventris has not yet been introduced into the Great Lakes and potential inoculum size and 

frequency are not known.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9
190

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 There are reported invasive C. cultriventris populations in Russia and Belarus (Khalko 2007, Kiyashko et al. 

2006, Semenchenko 2008, Slynko et al. 2002). Its distribution is continuing to spread northwards. The spread 

has been primarily attributed to the construction of reservoirs.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 C. cultriventris dominates the pelagic planktivorous fish assemblages in almost all reservoirs of the Volga 

cascade, including the Rybinsk Reservoir. The northward expansion of kilka is still continuing. In 2001 it 

dominated fish communities from Sheksna Reservoir to Beloye Lake (Slynko et al. 2002). Eutrophication, 

retarded flow, and formation of vast open sites suitable for these pelagic fish contributed to their dispersal and 

naturalization (Kiyashko et al. 2006). In addition, the nearly complete absence of competitors and low predator 

pressure may have been partially responsible for their spread and their dominance in the communities.

 Clupeonella cultriventris completely colonized the Uglich and Ivan’kov reservoirs of the Volga River within a 

span of 12 years (Kiyashko et al. 2006).

 The models developed by Kolar and Lodge (2002) predicted that Clupeonella cultriventris will spread at a fast 

rate and have negative impacts if introduced.

 It has populated the lower reaches of the Kama River in 1963-1966 (Mordukhaĭ-Boltovskoĭ 1979a).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

-20% total 

points (at 
191

its establishment and spread) end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 No control methods for this species are known to be present in the Great Lakes.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 85

>100 High Adjustments

B. Critical species A*(1- 0%) 85

51-99 Moderate C. Natural enemy B*(1- 10%) 76.5

Control measures C*(1- 0%) 76.5

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Clupeonella 

cultriventris if introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Clupeonella cultriventris poses a threat 

to water quality. It is unknown whether this species alters the physical components of the ecosystem. If 

introduced to the Great Lakes, Clupeonella cultriventris poses a threat to areas that lack important forage 

fish, which may contribute to the growing contaminant levels in piscivores (Ricciardi and Rasmussen 
192

1998); however, this effect has not been specifically documented for Clupeonella cultriventris. It 

dominates pelagic fish communities in the Volga and Sheksna reservoirs (Slynko et al. 2002). The 

dominance of Clupeonella cultriventris in the Volga may have suppressed native populations 

(Mordukhaĭ-Boltovskoĭ 1979b, Ricciardi and Rasmussen 1998); however, there is insufficient 

information available to determine which species were impacted. Clupeonella cultriventris may compete 

with other planktivorous pelagic fish if it attains a large population in the Great Lakes. In locations where 

Clupeonella cultriventris is very abundant, its diet is similar to the diets of native species, with a feeding 

similarity index greater than 50% (Kiyashko et al. 2007). On the other hand, where this species is less 

numerous, its feeding similarity with native species is less than 40%.

There is little or no evidence to support that Clupeonella cultriventris has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Clupeonella cultriventris poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Clupeonella cultriventris has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

This species one of the most abundant fish in the Caspian Sea and are commercially valuable in fisheries 

(Fazli et al. 2007). It is an important source of protein and income for people living in the Caspian Sea

(Karimzadeh et al. 2010) and is preyed on by commercially valuable fish such as sturgeon and salmon 

(Karimzadeh 2011). It is uncertain whether Clupeonella cultriventris would make a significant 

contribution to North American fisheries. It has not been indicated that Clupeonella cultriventris can be 

used for the control of other organisms or improving water quality. There is no evidence to suggest that 

this species is recreationally or medically valuable. It does not have significant positive ecological 

impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and 

ecosystems)

1 

Not significantly 0

Unknown U √

 No reports of hazardous effects on native populations were found.

 If introduced Bigeye Tulka poses the added threat of invading lakes that are currently devoid of important 

pelagic forage fish, which could result in increased contaminant levels in piscivores, an effect already 
193

documented for introduced smelt (Vander Zanden and Rasmussen 1996). However, this effect has not been 

specifically documented for Clupeonella cultriventris (Ricciardi and Rasmussen 1998).

 It dominates pelagic fish communities in the Volga and Sheksna reservoirs (Slynko et al. 2002). The dominance 

of Clupeonella cultriventris in the Volga may have suppressed native populations (Mordukhaĭ-Boltovskoĭ 

1979b, Ricciardi and Rasmussen 1998); however, it is unknown what species were impacted. 

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted 

threatened/endangered species or caused critical reduction, extinction, behavioral changes 

including modified spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 Clupeonella cultriventris is successful at establishing in non-native regions, though no data on its effect on 

specific native species were found.

 It has extended its range towards the Volga and Sheksna reservoirs, where it dominates pelagic fish 

communities (Slynko et al. 2002). The lack of competitors and low predation pressure in these reservoirs, as 

well as eutrophication, retarded flow, and the creation of habitats suitable for pelagic fish may have 

contributed to their spread and dominance over fish communities (Kiyashko et al. 2006). The dominance of this 

species in the Volga River reservoirs may have suppressed native fish populations (Mordukhaĭ-Boltovskoĭ 

1979b , Ricciardi and Rasmussen 1998). However, the identity of the species that have been impacted by 

Clupeonella cultriventris dominance remains unknown.

 In locations where Clupeonella cultriventris is very abundant, its diet is similar to the diets of native species, 

with a feeding similarity index greater than 50% (Kiyashko et al. 2007). On the other hand, where this species 

is less numerous, its feeding similarity with native species is less than 40%. Thus, it may compete with 

planktivorous fish for zooplankton if it attains a large population in the Great Lakes.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 In its native range, C. cultriventris is important as predator and prey, but nothing was found pertaining to its 

role in invaded ecosystems.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?
194

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 A genetic effect of C. cultriventris on other populations is not known.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 No reports of water quality alteration were found.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 No information about additional environmental impacts was found.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High
195

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 Clupeonella cultriventris can be consumed by humans, and there are no reports of threat to human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There are no reports of this species causing damage to infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There are no reports of this species altering water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?
196

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There are no reports of this species affecting markets or other economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There are no reports of this species inhibiting recreational activities.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There are no reports of this species diminishing aesthetic values.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
197

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There are no reports of this species acting as a biological control.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 There are suggestions for its potential use in Russian commercial fisheries (Aseinova 2003).

 In the Caspian, Clupeonella cultriventris is an important source of income and protein for many people in the 

region (Karimzadeh et al. 2010) and is preyed on by commercially valuable fish such as sturgeon and salmon 

(Karimzadeh 2011). Whether this species will make a significant contribution to North American fisheries is 

uncertain.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There are no suggestions of this species having recreational value.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

1
198

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

Not significantly 0 √

Unknown U

 There is no information about a potential medicinal or research value of this species. 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 No reports of water quality improvement by this species were found.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 Sturgeon preys on Clupeonella cultriventris (Karimzadeh 2011). Lake Sturgeon occurs in the Great Lakes and 

is listed as threatened in Michigan (MIDNR 2009). However, increasing the amount of food available for lake 

sturgeon may not contribute to their conservation; they are threatened due to overfishing and declining habitat 

quality rather than the lack of food. In addition, the Lake Sturgeon is a benthic feeder (Hayes and Caroffino 

2012), so there is a possibility that it will not feed on the pelagic Clupeonella cultriventris.

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
199

0 ≥2

Unknown

1 ≥1
200

Scientific Name: Cottus gobio 

Linnaeus, 1758

Common Name: Bullhead

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Cottus gobio has a moderate probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Cottus gobio does not occur near waters connected to the Great Lakes. It is not known to hitchhike or 

foul. Cottus gobio is not stocked, commercially cultured, or sold in the Great Lakes region. This species 

occurs in ports that have direct trade connections with the Great Lakes (NBIC 2009). Cottus gobio may 

survive ballast tank environments; however, ballast water exchange regulations that require flushing with 

full-strength seawater are likely to prevent its introduction due to its salinity tolerance. Cottus gobio may 

be introduced to the Great Lakes via ships declaring “No Ballast on Board” (NOBOB), which are exempt 

from ballast water exchange. The majority of ships entering the Great Lakes are NOBOB vessels and 

43% of these ships contain residual water with less than 10% salinity (Johengen et al. 2005). In the study, 

the temperature of the residual water from the vessels sampled ranged from -0.7 to 23.9°C; thus Cottus 

gobio is likely to survive the salinity and temperature of the NOBOB ballast water. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100
201

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Analysis of genetic structure shows Cottus gobio was first found in Northwestern Europe and then in the British 

freshwater system (Dorts et al. 2012).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Cottus gobio lives in the benthic zone but it is unlikely to attach to particular surfaces.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
202

No, this species this species is rarely/never sold. 0 √

Unknown U

 Cottus gobio is not available for purchase in North America, though it is used as bait in Europe.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Cottus gobio is not known to be stocked in the Great Lakes region.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100
203

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There is no evidence of this species being commercially cultured or transported though the Great Lakes.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Cottus gobio is predicted to be able to invade the Great Lakes in ballast water (Kolar and Lodge 2002). Cottus 

gobio may survive ballast tank environments; however, ballast water exchange regulations that require flushing 

with full-strength seawater are likely to prevent its introduction due to its salinity tolerance.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√
204

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Cottus gobio is widely distributed throughout Europe, from Greenland and Scandinavia to Italy, including 

England and Wales (Tomlinson and Perrow 2003).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points

Scored

Probability of 

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
205

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Cottus gobio has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate). 

The native and introduced ranges of Cottus gobio have similar climatic and abiotic conditions as the Great 

Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species can tolerate the 

temperature of the Great Lakes during the winter, but as an oxyphilic species, may not be capable of 

overwintering in waters with low-oxygen levels. Evidence suggests that increased water temperatures due 

to climate change may negatively impact reproductive physiology of Cottus gobio. Gonadal maturation 

for male and female fish was disrupted when water temperature was raised 8°C, reflecting complete 

reproductive failure (Dorts et al. 2012). This fish commonly inhabits cold, well-oxygenated streams and 

lakes, but has been found in large stagnant water bodies as a nonindigenous species (Nolte et al. 2005). 

Appropriate habitats are somewhat available in the Great Lakes. Hybrids of 2 Cottus gobio populations 

are thought to have greater potential to adapt to new habitats. The diet of Cottus gobio is flexible, and 

changes seasonally. The prey types in its diet are present in the Great Lakes. 

There is no indication that Cottus gobio is a strong competitor. In the River Great Ouse, Britain, a 

crayfish native to North America, Pacifastacus leniusculus (Dana), competes with Cottus gobio for 

shelter, and reduces its abundance (Guan and Wiles 1997). Pacifastacus leniusculus does not currently 

occur in the Great Lakes. Cottus gobio may be preyed on by some fish that occur in the Great Lakes 

including Salmo trutta and Esox lucius (Fuller et al. 2014, Fuller 2013). 

Cottus gobio has moderate fecundity (Hänfling and Weetman 2006, Vila-Gispert et al. 2005). It requires 

large stones to make nests in order to reproduce (Smyly 1957); it is unlikely that the reproductive strategy 

of this species will aid its establishment in the Great Lakes.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Cottus gobio predominantly occurs in stony streams and rivers where the flow is moderate and the water is cool 

and oxygen rich (Tomlinson and Perrow 2003).

 Cottus gobio found in critical thermal limits temperature of -4.2 and 27.7 ̊C (Tomlinson and Perrow 2003).
206

 Cottus gobio inhabits lakes and rivers (Smyly 1957).

 This species occurs in brackish waters such as the Baltic Sea, which has salinities < 7 ppt (Kontula and 

Väinölä 2001).

 The density of Cottus gobio is negatively correlated to DOC concentration and is absent in waters above 3 mg 

C L-1(Utzinger et al. 1998).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Cottus gobio is found in critical thermal limits temperature of -4.2 and 27.7°C (Tomlinson and Perrow 2003).

 It commonly inhabits well-oxygenated waters, but has been found in large stagnant water bodies as 

nonindigenous species (Nolte et al. 2005). It may be able to tolerate the low temperatures as low as -4.2°C over 

the winter, but it is not known whether it can tolerate low oxygen levels in the Great Lakes.

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

Cottus gobio most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Its diet changes with seasons; generally crustaceans are taken in the winter and a wide range of insect larvae in 

the summer (Tomlinson and Perrow 2003). 

 Cottus gobio feeds on benthic invertebrates (Smyly 1957). In the winter, Gammarus amphipods were a large 

component of their diet (Mills and Mann 1983), and in the summer, these fish hit their peak consumption of 

Plecoptera nymphs.These prey items occur in the Great Lakes. 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9
207

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

0

 Cottus gobio is a poor competitor and can be outcompeted by large fish (Tomlinson and Perrow 2003). 

 In the River Great Ouse in Britain, a North American crayfish Pacifastacus leniusculus competes with Cottus 

gobio for shelter and reduces its abundance (Guan and Wiles 1997). Pacifastacus leniusculus does not currently 

occur in the Great Lakes.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Cottus gobio grows rapidly, matures early but is short-lived in lowland streams, with only three age classes 

represented in the population (Tomlinson and Perrow 2003).

 Cottus gobio has moderate fecundity according to Hänfling and Weetman (2006) and Vila-Gispert et al. (2005). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0
208

Unknown U

0

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 Cottus gobio has been established in United Kingdom rivers, which are similar to Great Lakes environment 

(Tomlinson and Perrow 2003).

 Cottus gobio predominantly occurs in stony streams and rivers where the flow is moderate and the water is cool 

and oxygen rich. In the Great Lakes, temperatures vary from season to season and flow is reduced.

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Cottus gobio lives in the Ponto-Caspian and the United Kingdom.

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
209

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Water depth, moderate water flow, and cool water temperatures found in the Great Lakes during winter can 

provide suitable habitat for Cottus gobio.

 Cottus gobio requires various habitats according to its different life stages. Substrates with large stones appear 

essential for breeding, and leaf litter and macrophyte cover are preferred by adult fish (Tomlinson and Perrow 

2003).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

0

 Cottus gobio prefers cold water temperatures and moderate to high streamflow (Tomlinson and Perrow 2003).

 Cottus gobio individuals were put in three temperatures (6-10, 10-14, 14-18°C); a result from (T3) indicate that 

8°C rise in water temperature disrupted the gonadal maturation in both gender (Dorts et al. 2012). The findings 

of the study suggest that exposure to elevated temperature within the context of climate worming might affect 

the reproductive success of Cottus gobio (Dorts et al. 2012).

 Reyjol et al. (2009) did a study on water temperature and Cottus gobio life history traits and reproduction. The 

results suggest that a mean air warming of 3.7° is enough to negatively impact C. gobio populations.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 3
210

may be considered potential food items—are abundant and/or search time is moderate to 

high)

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

6

 The diet of Cottus gobio changes with the seasons and the availability of different food items. Generally 

crustaceans are taken in the winter months and a wide range of insect larvae in the summer; feeding activity 

takes place at dusk and perhaps also at night (Tomlinson and Perrow 2003).

 Cottus gobio feeds on benthic invertebrates (Smyly 1957). In the winter, Gammarus amphipods were a large 

component of their diet (Mills and Mann 1983), and in the summer, these fish hit their peak consumption of 

Plecoptera nymphs.These prey items occur in the Great Lakes. 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

6
211

and spread in the Great Lakes)

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-20%

 Larger fish (>75 g) and crayfish have a detrimental effect on bullhead population through competition for 

shelter, food, and direct predation; however, bullhead can co-exist with predators provided sutiable refuges are 

available (Tomlinson and Perrow 2003).

 Cottus gobio may be preyed on by some fish that occur in the Great Lakes including Salmo trutta and Esox 

lucius (Fuller et al. 2014, Fuller 2013).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0
212

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Cottus gobio probably colonized England when Britain was connected to mainland Europe during the last ice 

age. The explanation for its current distribution includes natural headwater capture and possibly human 

introduction (Tomlinson and Perrow 2003).

 This species is widespread in Europe. Its native range includes the Ponto-Caspian basin, the Baltic Sea basin, 

and the Iberian Peninsula (Vila-Gispert et al. 2005, Mann et al. 1984). It has extended its range to the southeastern Pyrenees watershed, the Netherlands, and Germany. It seems that the spread of Cottus gobio is 

currently restricted to middle to eastern Europe. 

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no -90% total 
213

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 No control methods are known to be present in the Great Lakes for Cottus gobio.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 68

>100 High Adjustments

B. Critical species A*(1 - 0%) 68

51-99 Moderate C. Natural enemy B*(1 - 20%) 54.4

Control measures C*(1 - 0%) 54.4

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low
214

Current research on the potential for environmental impacts to result from Cottus gobio if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Cottus gobio poses a threat to other 

species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

Phyllodistomum folium is a parasite of Cottus gobio (Smyly 1957) and infects the urinary bladder (Dawes 

1968). Three-spined sticklebacks, ruffe, grayling, and pike are also hosts of this parasite. Phyllodistomum 

folium has been found in central Europe, Sweden, and Canada. Phyllodistomum folium has been recorded 

in one specimen of pike in Lac Hertel of the Saint-Lawrence Valley, and has a limited occurrence (Todd 

1963). There is no indication that Phyllodistomum folium is currently a threat for the Great Lakes species 

or will become a threat with the introduction of Cottus gobio. 

There is little or no evidence to support that Cottus gobio has the potential for significant socioeconomic impacts if introduced to the Great Lakes.

It has not been reported that Cottus gobio poses a threat to human health or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Cottus gobio has the potential for significant beneficial 

impacts if introduced to the Great Lakes.

It has not been indicated that Cottus gobio can be used for the control of other organisms or improving 

water quality. There is no evidence to suggest that this species is recreationally or medically valuable. It 

does not have significant positive ecological impacts. Cottus gobio can be eaten or used as live bait for 

large fish (Tomlinson and Perrow 2003). 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and 

ecosystems)

1

Not significantly 0

Unknown U √

 There is no evidence that Cottus gobio is a hazard or threat to the health of native species.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?
215

Yes, and it has resulted in significant adverse effects (e.g., impacted 

threatened/endangered species or caused critical reduction, extinction, behavioral changes 

including modified spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0

Unknown U √

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 No data were found that show genetic effects of Cottus gobio on native populations.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 There was no evidence of Cottus gobio affecting water quality.
216

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0

Unknown U √

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of a 

particular impact. An “Unknown” response is appropriate if the potential for a particular impact might be 

inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U
217

 There was no evidence of Cottus gobio species posing a hazard or threat to human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
218

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of a 

particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 

Not significantly 0 √

Unknown U

 Cottus gobio was once eaten recreationally for its flavor and also used as live bait for larger fish species 

(Tomlinson and Perrow 2003).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 6
219

communities and/or tourism

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
220

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
221

Scientific Name: Ctenopharyngodon idella

Valenciennes in Cuvier and Valenciennes, 1844

Common Name: Grass Carp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Moderate

Escape from commercial culture: Low

Transoceanic shipping: Unlikely

Ctenopharyngon idella has a high probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Dispersal, Unauthorized Intentional Release, Unauthorized 

Stocking, Escape from Commercial Culture

Asian Carp introduced to the Mississippi River basin via escape from aquaculture, are identified as having 

high probability of invasion if introduced to the Great Lakes (Herborg et al. 2007, Mandrak and Cudmore 

2005, Rixon et al. 2005, USEPA 2008); and listed as having extensive invasion history (Nico et al. 2015, 

Gherardi et al. 2009, GISD 2005a). Potential pathway of introduction: Inter-basin connections. NOTE: 

Grass Carp collected in the Great Lakes have been an illegally released, non-reproductive triploid variety.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Grass Carp individuals have been found in the Great Lakes but have not shown evidence of reproduction or 

establishment (Rixon et al. 2005).
222

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Grass Carp individuals have been found in the Great Lakes but have not shown evidence of reproduction or 

establishment (Rixon et al. 2005).

 The United States Army Corps of Engineers (USACE) constructed a set of three electrical barriers, the first of 

which opened in 2002, on the Chicago Sanitary and Shipping Canal to prevent the spread of aquatic invasive 

species between the Great Lakes and Mississippi River basins (Baerwaldt et al. 2013). While this barrier will 

impede the spread of Grass Carp from the Mississippi River basin, Grass Carp has also be reported in waters 

around the Great Lakes basin (i.e. not influenced by these barriers).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 This species is not known to be transported by attaching to recreational equipment.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
223

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 This species was recorded to be found in three of the six live markets near Lakes Erie and Ontario (Rixon et al. 

2005). Also, it was sold under names such as Chinese Buffalo and China Cardfish so individuals may not be 

aware they have a potential invader.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5 

√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 An online search several stores that ship triploids to the Great Lakes States.

 The 2005 study by Rixon found this species for sale at markets near Lakes Erie and Ontario. While surveillance 

has likely increased, there is no evidence that Grass Carp is no longer for sale.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Michigan is allowed to have eggs for research, but surrounding states are allowed to stock triploid Grass Carp 

(Conover 2007).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75 

√

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 Grass Carp were illegally stocked in Michigan (Emery 1985).
224

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100 √

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U

 This species is cultured in states surrounding the Great Lakes (Conover 2007).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25 

√

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

 Very few states have no regulations and allow diploid Grass Carp, and the majority either restrict both or allow 

triploid nonreproductive Grass Carp (Conover 2007).

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 Grass Carp are not known to be taken up through ballast.
225

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 0.75 75 Moderate

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x 0.25 25 Low

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
226

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Ctenopharyngon idella has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

The climate of the Great Lakes region is suitable for Ctenopharyngon idella. They tolerate temperature 

minimums to 4oC (Herborg et al. 2007) so would have no difficulty overwintering. To the contrary, they 

have shown to have an ecological advantage for migrating to habitats with rapid temperature changes 

(Zhao et al. 2011). Spawning requires flowing rivers with a higher temperature – conditions which are

met in only a few areas of the Great Lakes, but these areas are capable of producing fish which would 

then migrate throughout the system (Schofield et al. 2005).

Grass Carp are obligate herbivores, eating massive quantities of aquatic plants (Petr and Mitrofanov 

1998). This diet preference may restrict them to the shallower littoral zones and coastal wetlands of the 

Great Lakes, where suitable food is plentiful. They are known to be successful competitors against native 

fishes (USEPA 2008).

Current regulations and control measures are in place which are somewhat likely to be effective in 

preventing the establishment of Grass Carp in the Great Lakes.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7
227

 Grass Carp have shown to have an ecological advantage for migrating to habitats with rapid temperature 

changes (Zhao et al. 2011).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Minimum temperature range is from -11–4 ̊C (Herborg et al. 2007).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

4

 Grass Carp are a strictly herbivorous species that has an intense grazing activity over aquatic vegetation (Petr 

and Mitrofanov 1998).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
228

Unknown U

8

 Has known to destroy existing food chain relationships and threatens the spawning grounds of native fish when 

in excessive numbers (Petr and Mitrofanov 1998).

 Grass Carp are known to compete with native fish and have a history of invasion throughout the United States 

(USEPA 2008).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

5

 Spawning occurs at water temperatures between 17-26 ̊C and more commonly occurs in large flowing rivers. 

Fecundity has been found to range widely from 2555,000-2,000,000 eggs (Schofield et al. 2005).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Spawning is required in flowing rivers with a higher temperature and is needed for success in early 

development, only a few areas in the Great Lakes can provide this type of environment for spawning by the 

Grass Carp (Schofield et al. 2005).

ENVIRONMENTAL COMPATIBILITY
229

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 Grass Carp native region of Eastern Asia is very similar to that of the United States with a temperate climate, 

warm summers and cold winters.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

5

 Spawning is required in flowing rivers with a higher temperature and is needed for success in early 

development, only a few areas in the Great Lakes can provide this type of environment for spawning in the 

Grass Carp (Schofield et al. 2005).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 It is estimated around 91-100% environmental suitability throughout a majority of the United States and about 

half of Canada (Herborg et al. 2007).
230

 Spawning is required in flowing rivers with a higher temperature and is needed for success in early 

development, only a few areas in the Great Lakes can provide this type of environment for spawning in the 

Grass Carp (Schofield et al. 2005).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 The effects of climate change would most likely help the establishment of the Grass Carp in the Great Lakes and 

allow it to spread throughout all 5 (Mandrak 1989).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 There appears to be no restrictions on food; Grass Carp are very diverse feeders, feeding on a majority of 

aquatic vegetation.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 9
231

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required for the critical stages of the Grass Carp life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 The establishment of this species will not be aided by an establishment of another species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)
232

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 There is bacteria that can kill the Grass Carp but they are transmitted through Bighead and Silver Carp which 

are not found in the Great Lakes (Kolar et al. 2005).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

4

 There have been recorded catches of the Grass Carp in Lake Michigan, Huron, and Erie (Rixon et al. 2005).

 Grass Carp has been found isolated in Lake Erie, Huron, Ontario (USEPA 2008).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9
233

 Grass Carp were established in numerous states in 1993, 30 years after its initial release in Arkansas (DeVaney 

et al. 2009).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 After being stocked in the Volga River it took 7 years for a reproducing population and after introduction in the 

Amu-Darya River it had a reproducing population within a year (Stanley 1976).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-40%

 The Asian Carp management and control plans can used for Grass Carp.

 The Asian Carp Control Strategy Framework can used for Grass Carp.

 The Asian Carp Regional Coordinating Committee can used for Grass Carp.

 The Asian Carp Monitoring and Rapid Response Plan can used for Grass Carp.

 eDNA monitoring can used for Grass Carp.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 99

>100 High Adjustments
234

B. Critical species A*(1- 0%) 99

51-99 Moderate C. Natural enemy B*(1- 0%) 99

Control measures C*(1- 40%) 59.4

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: High 

Ctenopharyngon idella has the potential for high environmental impact if introduced to the Great 

Lakes.

Grass Carp have environmental impacts on the ecosystems they have been introduced. For instance, Grass 

Carp is known to be the source of major alterations to the trophic structure and food chains of aquatic 

systems. Many of these changes in plant, invertebrate and fish communities are largely secondary 

consequences of reductions in the density and composition of aquatic plant communities (Bain 1993, 

Cudmore and Mandrak 2004). When stocked at high densities, Grass Carp can eliminate all vegetation in 
235

even large aquatic systems (e.g., 8100-ha Lake Conroe, Klussman et al. 1988). Declines have occurred in 

the diversity and density of organisms that are dependent on structured littoral habitats and food chains 

based on plant detritus, macrophytes, and attached algae as a consequence of reduced plant surface 

habitat, increased invertebrate food supplies (i.e. plant detritus), altered substrate conditions, and 

increased dissolved oxygen conditions (Bain 1993, Martin and Shireman 1976, Vinogradov and Zolotova 

1974).

Ctenopharyngodon idella is known to out-compete native species for both food and habitat. Research in 

small closed systems has demonstrated that due to Grass Carp’s preference for native aquatic plants over 

milfoil, these fish compete with waterfowl, which feed on these plants as well (Fowler and Robson 1978, 

McKnight and Hepp 1995, Pine et al. 1990, Pine and Anderson 1991). Furthermore, direct competition 

for plant material also occurs between Grass Carp and other herbivorous fishes, such as forage fishes

(Cudmore and Mandrak 2004). Grass Carp may compete with planktonic and benthic species, including 

catfishes and hybrid sunfishes for aquatic plants (Shireman and Smith 1983), especially during Grass 

Carp juvenile stages and at lower water temperatures (Fedorenko and Fraser 1978). Direct competition 

for habitat has been found to occur between Grass Carp and other fish species, particularly bluegill. With 

their schooling habit, Grass Carp constantly invade and disturb bluegill spawning areas, consequently 

greatly reducing Bluegill weight and numbers (Forester and Lawrence 1978).

Grazing by Grass Carp has been associated with alterations of water quality. The decay of these large 

volumes of dead aquatic plants due to Grass Carp’s grazing and waste production elevate nutrient levels 

in water, induce phytoplankton blooms, reduce water clarity, and decrease oxygen levels (Bain 1993, 

Boyd 1971, Vinogradov and Zolotova 1974).

Cyprinids, including Grass Carp, are known to be carriers of numerous parasitic organisms. Shireman and 

Smith (1983) thoroughly list a wide array of organisms, from viruses to protozoans to trematodes, that are 

parasites of Grass Carp. Worth noting is Bothriocephalus acheilognathi, the Asian Tapeworm. This 

parasite has been introduced by cyprinids, particularly by its native host the Grass Carp, to every 

continent except Antarctica (Bain 1993, Salgado-Maldonado and Pineda-Lopez 2003). Additionally, 

Grass Carp are the source of Ergacilus spp. in United Kingdom waters (Cowx 1997). However, disease 

and parasitism are not as prevalent in wild populations as in fish culture (Shireman and Smith 1983).

There is little or no evidence to support that Ctenopharyngon idella has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Ctenopharyngon idella poses a threat to human health or water quality. There 

is no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits. One of the undesirable 

consequences of stocking Grass Carp is increased turbidity, either algal or abiotic (Bonar et al. 2002, 

Lembi et al. 1978, Maceina et al. 1992, Water Environmental Services Incorporated 1994). When in 

excessive numbers it can destroy existing food chain relationships and threatening the spawning grounds 

of commercial fishes (Petr and Mitrofanov 1998).

Ctenopharyngon idella has the potential for high beneficial impact if introduced to the Great Lakes.

Because of its strong preference for aquatic vegetation, ability to be cultured easily, and hardiness, Grass 

Carp is being widely introduced throughout the United States to control aquatic vegetation in lakes and 

ponds (Chilton and Muoneke 1992, Page and Burr 1991). Grass Carp can effectively control and 

eliminate aquatic plants in a variety of situations. Private fish farms have been producing large numbers 

of sterile, triploid Grass Carp as interest in stocking open systems increases (Bain 1993). Grass Carp also 
236

are now routinely stocked in irrigation canals of the western United States (Bain 1993) and in 

Saskatchewan, Canada (Cudmore and Mandrak 2004).

Despite its bony flesh, Grass Carp is consumed as food in many regions of the world (Opuszynski and 

Shireman 1995) and are fished in some areas in their native range (Shireman and Smith 1983). However, 

they rarely comprise a large proportion of the catch and are taken incidentally in common or silver carp 

fisheries in the Amur basin (Shireman and Smith 1983). In the United States, Grass Carp has been 

harvested Mississippi River in Missouri throughout the 1990s (Pflieger 1997) and by 1996, it accounted 

for 8% of the total commercial fish harvest from this area (Cudmore and Mandrak 2004, USGS 2012).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Cyprinids, including Grass Carp, are known to be carriers of numerous parasitic organisms. Shireman and 

Smith (1983) thoroughly list a wide array of organisms, from viruses to protozoans to trematodes, that are 

parasites of Grass Carp. Worth noting is Bothriocephalus acheilognathi, the Asian tapeworm. This parasite has 

been introduced by cyprinids, particularly by its native host the Grass Carp, to every continent except 

Antarctica (Bain 1993, Salgado-Maldonado and Pineda-Lopez 2003). Additionally, Grass Carp are the source 

of Ergacilus spp. in United Kingdom waters (Cowx 1997). However, disease and parasitism are not as 

prevalent in wild populations as in fish culture (Shireman and Smith 1983).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Ctenopharyngodon idella is known to out-compete native species for both food and habitat. Research in small 

closed systems has demonstrated that due to Grass Carp’s preference for native aquatic plants over milfoil, 

these fish compete with waterfowl, which feed on these plants as well (Fowler and Robson 1978, McKnight and 

Hepp 1995, Pine et al. 1990, Pine and Anderson 1991). Furthermore, direct competition for plant material also 
237

occurs between Grass Carp and other herbivorous fishes, such as forage fishes (Cudmore and Mandrak 2004). 

Grass Carp may compete with planktonic and benthic species, including catfishes and hybrid sunfishes for 

aquatic plants (Shireman and Smith 1983), especially during Grass Carp juvenile stages and at lower water 

temperatures (Fedorenko and Fraser 1978).

 On the other hand, direct competition for habitat has been found to occur between Grass Carp and other fish 

species, particularly bluegill. With their schooling habit, Grass Carp constantly invade and disturb bluegill 

spawning areas, consequently greatly reducing bluegill weight and numbers (Forester and Lawrence 1978).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 Grass Carp have environmental impacts on the ecosystems they have been introduced. For instance, Grass 

Carp is known to be the source of major alterations to the trophic structure and food chains of aquatic systems. 

Many of these changes in plant, invertebrate and fish communities are largely secondary consequences of 

reductions in the density and composition of aquatic plant communities (Bain 1993, Cudmore and Mandrak 

2004). When stocked at high densities, Grass Carp can eliminate all vegetation in even large aquatic systems 

(e.g., 8100-ha Lake Conroe, Klussman et al. 1988). Declines have occurred in the diversity and density of 

organisms that are dependent on structured littoral habitats and food chains based on plant detritus, 

macrophytes, and attached algae as a consequence of reduced plant surface habitat, increased invertebrate 

food supplies (i.e. plant detritus), altered substrate conditions, and increased dissolved oxygen conditions (Bain 

1993, Martin and Shireman 1976, Vinogradov and Zolotova 1974).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 There has been no evidence of it affecting native populations genetically.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?
238

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 Grazing by Grass Carp has been associated with alterations of water quality. The decay of these large volumes 

of dead aquatic plants due to Grass Carp’s grazing and waste production elevate nutrient levels in water, 

induce phytoplankton blooms, reduce water clarity, and decrease oxygen levels (Bain 1993, Boyd 1971, 

Vinogradov and Zolotova 1974).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U

 The herbivorous Grass Carp has a significant impact on macrophyte communities through intense grazing 

pressure (Bain 1993).

Environmental Impact Total 20

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT
239

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There has been no evidence showing hazardous threats to human health by the Grass Carp.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There has been no evidence showing damage to infrastructure by the Grass Carp.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 One of the undesirable consequences of stocking Grass Carp is increased turbidity, either algal or abiotic 

(Bonar et al. 2002, Lembi et al. 1978, Maceina et al. 1992, Water Environmental Services Incorporated 1994).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 When in excessive numbers it destroys existing food chain relationships and threatening the spawning grounds 

of commercial fishes (Petr and Mitrofanov 1998).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?
240

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no evidence provided that it inhibits recreational activities. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 √

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 1 
241

level of effectiveness

Not significantly 0 

Unknown U

 Because of its strong preference for aquatic vegetation, ability to be cultured easily, hardiness and good flavor, 

Grass Carp is being widely introduced throughout the United States to control aquatic vegetation in lakes and 

ponds (Chilton and Muoneke 1992, Page and Burr 1991). Grass Carp can effectively control and eliminate 

aquatic plants in a variety of situations. Private fish farms have been producing large numbers of sterile, 

triploid Grass Carp as interest in stocking open systems increases (Bain 1993). Grass Carp also are now 

routinely stocked in irrigation canals of the western United States (Bain 1993) and in Saskatchewan, Canada 

(Cudmore and Mandrak 2004).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Despite its bony flesh, Grass Carp is consumed as food in many regions of the world (Opuszynski and Shireman 

1995) and are fished in some areas in their native range (Shireman and Smith 1983). However, they rarely 

comprise a large proportion of the catch and are taken incidentally in common or silver carp fisheries in the 

Amur basin (Shireman and Smith 1983). In the United States, Grass Carp has been harvested Mississippi River 

in Missouri throughout the 1990s (Pflieger 1997) and by 1996, it accounted for 8% of the total commercial fish 

harvest from this area (Cudmore and Mandrak 2004, USGS 2012).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6 

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Grass Carp are frequently used for prayer release (freeing captive animals into the wild as a form of prayer to 

accrue merits (Crossman and Cudmore 1999a, 1999b; Severinghaus and Chi 1999); these individuals can then 

be caught by recreational fisherman (Cudmore and Mandrak 2004).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 

Not significantly 0 √

Unknown U
242

 There has been no real significant medicinal or research value of the Grass Carp.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There has been no evidence showing Grass Carp removes pollutants from the water.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 Grass Carp have shown to destroy existing food chain relationships and threatening the spawning grounds of 

commercial fishes in excessive numbers (Petr and Mitrofanov 1998).

 Grass Carp are known to be vectors for B. acheilognathi which have been known to infect and kill native 

species (Kolar et al. 2005).

 Grass Carp have negative impacts on phytoplankton, invertebrate communities, and native fish (Herborg et al. 

2007).

Beneficial Effect Total 8

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
243

Scientific Name: Cyprinella whipplei 

Girard, 1856

Common Name: Steelcolor Shiner

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Moderate

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Cyprinella whipplei has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Dispersal 

Cyprinella whipplei occurs in the Mississippi River basin, Ohio River, Muskingum River, and the Fox 

River drainage, which are near waters connected to the Great Lakes basin (Page and Burr 1991, Retzer 

and Batten 2005, Sanders 1992). There are electrical barriers between the Great Lakes and Mississippi 

River basins that function to prevent the spread of aquatic invasive species (Rasmussen et al. 2011). There 

is no evidence that suggests that Cyprinella whipplei is capable of hitchhiking or fouling ships. There are 

no records of the stocking, culture, or sale of Cyprinella whipplei in the Great Lakes region.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U
244

 The Steelcolor Shiner Minnow occurs in spots throughout the Mississippi River basin extending up to the 

northern borders of the Great Lakes basin including the upper and middle Ohio River basin, spanning Ohio, 

Indiana, and Illinois (Page and Burr 1991).

 Cyprinella whipplei occurs in the Ohio and Muskingum Rivers near Marietta, Ohio (Sanders 1992).

 C. whipplei occurs in the Fox River drainage near Chicago, Illinois (Retzer and Batten 2005).

 The Steelcolor Shiner Minnow is mobile and able to swim through small bodies of water and streams if 

environmental conditions are not lethal (Gibbs 1963).

 There are electrical barriers between the Great Lakes and Mississippi River basins that function to prevent the 

spread of aquatic invasive species (Rasmussen et al. 2011).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

√

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Though barriers do exist in various locations in rivers that do and could harbor the Steelcolor Shiner Minnow 

(Sparks 2010), it is widespread enough to have true access if other variables were suitable (Schönhuth and 

Mayden 2010, Taylor 2000).

 The Steelcolor Shiner Minnow prefers the larger pools of quicker upland riverine habitats (Hocutt and Wiley 

1986). These areas are prevalent on all outside borders of the Great Lakes basin as well as within it. 

 This species has been found in the Ohio and Muskingum Rivers near Marietta, Ohio, which is approximately 

260 kilometers from Lake Erie (Sanders 1992). 

 This species occurs in the Fox River drainage near the Chicago, Illinois region (Retzer and Batten 2005). Fox 

River is about 65 kilometers from Lake Michigan. 

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Being a fish, the Steelcolor Shiner Minnow is not likely, in any part of its life cycle, to attach to surfaces (Gibbs 

1963).

 Though not likely or often, there is some possibility of fish or fish egg transport via natural (e.g., bird) or 

human (e.g., bait bucket) means.

2b) What is the proximity of this species to the Great Lakes basin?
245

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 The Steelcolor Shiner Minnow is not currently listed in Michigan’s fish surveys; however, under its previous 

taxonomic name of Notropis whipplii, it is listed as a common minnow of Michigan waters (Hubbs and Cooper 

1936). More phylogenetic and taxonomical research would be necessary to establish whether this particular 

minnow was ever present in the Great Lakes basin as a native species.

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 The Steelcolor Shiner Minnow being raised, kept, or sold as a bait fish like other minnows is a possibility, there 

is no known record of it occurring (INDNR 2013, Willoughby 1965, Yoder 1954).

 The Steelcolor Shiner Minnow is not sold legally or on the “black market” (INDNR 2013).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 There is no known instance of the Steelcolor Shiner Minnow being stocked or grown for food, bait, or 

recreational purposes in or around the Great Lakes region (INDNR 2013).
246

 Though the Steelcolor Shiner could be used as bait or stock for ponds, it is not listed in commercial listings or 

as prohibited for aquaculture sales (MacNeill et al. 2009). It is thought that this fish is not hardy enough for 

this purpose (Mayden 2003).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Though the Steelcolor Shiner Minnow is not often grown or sold as bait or food, the mere proximity of this fish 

does allow for transport. No record was found of the steelcolor shiner minnow being transported (MIDNR

2013).

 The Steelcolor Shiner Minnow is not a prohibited fish for transport (MacNeill et al. 2009).

 The Steelcolor Shiner Minnow is located in streams near the border of the Great Lakes basin and could be 

transported by individuals; however there is no record of this (Schönhuth and Mayden 2010).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U
247

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 For several reasons already discussed above, such as specific riverine habitats and delicate survival needs, it is 

unlikely that the Steelcolor Shiner Minnow would be incorporated into the ballast of large ships as a vector for 

transport (Britton et al. 2010, Clavero and Garcia-Berthou 2006, Gozlan et al. 2010b). 

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.75 75 Moderate

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely
248

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Cyprinella whipplei has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate). 

Cyprinella whipplei has a wide temperature tolerance, and has been reported to occur in streams with 

temperatures as low as -0.5°C (Felley and Hill 1983) to temperatures as high as 25°C (Risch 2004). This 

species is somewhat likely to overwinter in the Great Lakes region due to its ability to tolerate low 

temperature waters and its current geographical range that extends to Illinois and Ohio. It is native to the 

Alabama and Louisiana, so warmer water temperatures and shorter ice cover may aid the establishment of 

Cyprinella whipplei. It inhabits streams of varying sizes with sand or gravel bottoms and permanent flows 

(Ross 2001). This species reproductive behavior involves the use of crevices in submerged logs (Pflieger 

1965). These habitats are available in the Great Lakes basin. 

Cyprinella whipplei may have a low tolerance to habitat degradation. This species once occurred 

throughout central Illinois, but has retreated eastwards (Smith 2002). Its retreated distribution has been 

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
249

attributed to increasing siltation, removal of riparian vegetation, and the deterioration of water quality, as 

well as its inability to compete with the red shiner and spotfin shiner. Cyprinella whipplei was found in 

fish surveys conducted in 2008 in Killbuck Creek and Pipe Creek, Indiana, but were absent in 1978 (Doll 

2010). Since the 1978 survey, there has been an effort to increase the area of wetland coverage in Indiana, 

although there has been some clear cutting of the riparian zone in 1998. It is possible that Cyprinella 

whipplei was able to establish in these areas since 1978 due to increased habitat quality. 

Cyprinella whipplei feeds on macroinvertebrates such as aquatic and terrestrial insects, benthic 

invertebrates, crustaceans, mites, and earthworms (Ross 2001, Stauffer 2007). Its prey is readily available 

in the Great Lakes basin. Piscivorous animals such as gar, bass, sunfish, sturgeon, large chubs, kingfisher, 

heron, and turtles are known to feed on shiners (Mayden 2013 pers. comm.). These piscivores occur in the 

Great Lakes region (MDEQ 2008).

Cyprinella whipplei is established in Oklahoma (Fuller and Nico 2015a). A survey conducted by Fisher et 

al. (1998) in 1994 found that the historically uncommon Cyprinella whipplei had expanded its range in 

Tippecanoe County, Indiana since the mid-1970’s. The 1978 survey collected 2 specimens of Cyprinella 

whipplei, and the 1994 survey collected 16 specimens; however, the authors note that the historically low 

abundance of Cyprinella whipplei could be attributed to misidentification of this species during the 1978 

survey. Although historically present in Indiana, Cyprinella whipplei was first recorded in the Kankakee 

River drainage in 1990 (Simon et al. 1992). Cyprinella whipplei was found in fish surveys conducted in 

2008 in Killbuck Creek and Pipe Creek, but were absent in 1978 (Doll 2010).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

3

 Though widespread in the mid United States, the Steelcolor Shiner Minnow has a narrower habitat preference 

range than other species in its genus, and thus it is found in local “pockets” (Mayden 1989, Smith 2002, 

Trautman 1980).

 The Steelcolor Shiner Minnow prefers upland pools of quick moving riverine habitats, which are found in many 

areas of the Great Lakes; however, it is apparently not tolerant to extremes outside of this range, because it is 

not found in broad areas and immediately neighboring habitats (Doll 2010, Gibbs 1963, Hubbs and Cooper 

1936, Schönhuth and Mayden 2010).

 That the Steelcolor Shiner Minnow has not been used to stock ponds or raised for bait purposes may indicate 

that it is not hardy under variable, non-native conditions or in situations of over-crowding or low biodiversity 

(INDNR 2013, MIDNR 2013, Willoughby 1965, Yoder 1954).

 This species has been recorded in streams with temperatures as low as -0.5°C (Felley and Hill 1983) and as 

high as 25.0°C (Risch 2004).
250

 This species has been found in streams that have 7.7 – 10.0 mg/L dissolved oxygen (Risch 2004).

 Cyprinella whipplei may have a low tolerance to habitat degradation. This species once occurred throughout 

central Illinois, but has retreated eastwards (Smith 2002). Its retreated distribution has been attributed to 

increasing siltation, removal of riparian vegetation, and the deterioration of water quality. Cyprinella whipplei

was found in fish surveys conducted in 2008 in Killbuck Creek and Pipe Creek, Indiana, but were absent in 

1978 (Doll 2010). Since the 1978 survey, there has been an effort to increase the area of wetland coverage in 

Indiana, although there has been some clear cutting of the riparian zone in 1998. It is possible that Cyprinella 

whipplei was able to establish in these areas since 1978 due to increased habitat quality.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

5

 Since the Steelcolor Shiner Minnow exists so close to the southern border of the Great Lakes basin in its normal 

range, it must be able to withstand some temperature ranges of winter. However, it has not infiltrated 

simultaneously with other species in the same genus over time (Doll 2010, Felley 1983, McAllister et al. 2010, 

Schönhuth and Mayden 2010, Taylor 2000).

 The phylogenetic differentiation of the Cyprinella whipplei and Notropis spiloptera, the Spotfin Shiner, that 

occurred after 1938 can indicate that the Steelcolor Shiner Minnow may be limited to a more southern range 

than the Spotfin Shiner (Gibbs 1957, Gibbs 1963, Mayden 1989, Schönhuth and Mayden 2010, Trautman 1980).

 This species has been found in streams that have 7.7 – 10.0 mg/L dissolved oxygen and at temperatures up to 

25.0°C (Risch 2004).

 This species has been recorded in streams with temperatures as low as -0.5°C (Felley and Hill 1983).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6 

 This fish feeds on aquatic and terrestrial insects, small crustaceans, mites, and earthworms (Stauffer 2007). 

 Cyprinella whipplei generally feeds on insects in the water column, and changes its diet seasonally (Ross 2001). 

They feed on terrestrial insects that fall into the stream in the summer and fall. Cyprinella whipplei shifts to 

feeding on benthic invertebrates during colder weather. During the winter and spring, they also feed on organic 

detritus.
251

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

5

 Information and studies regarding the competitive abilities of Cyprinella whipplei are insufficient. 

 In central Illinois, the distribution of Cyprinella whipplei had retreated to the eastern side of Illinois. This 

reduction in geographical range has been attributed to its inability to tolerate declining habitat quality 

(siltation, degradation of riparian zone, poor water quality), and its inability to compete with the Red Shiner 

and Spotfin Shiner (Smith 2002).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 There is not much research on the quantity or survival rate of offspring for the Steelcolor Shiner Minnow. The 

reproductive method is described as crevice-spawning (Johnston 1999, Pflieger 1965), but more data would be 

needed for the approximate numbers of living offspring compared to other minnows of the same genus or how 

offspring numbers varied with environmental changes.

 Pflieger 1965 did note that Notropis whipplii did breed in aquaria habitats, which would demonstrate fecundity 

or hardiness but it is unknown now whether it was the renamed Cyprinella whipplei or Notropis spiloptera

species.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 9
252

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 There is literature based on the reproductive habits of the Steelcolor Shiner Minnow and it is described as 

crevice spawning (Hocutt and Wiley 1986, Johnston 1999, Pflieger 1965, Smith and Smith 1983). This minnow 

prefers habitat with fallen logs and branches in moderately moving river areas for breeding. 

 The required breeding habitat for the Steelcolor Shiner Minnow, crevices in submerged logs and roots, is 

prevalent in the Great Lakes area. This species has not been documented to exhibit reproductive strategies 

(such as parthenogenesis, self-fertilization, or vegetative states) to improve reproductive success in suboptimum environmental conditions. 

 According to several sources describing the Steelcolor Shiner Minnow’s reproductive method (Johnston 1999, 

Mayden and Simons 2003, Pflieger 1965), there is no indication it has any increase in hardiness over other 

minnows of the same genus and could even be less fit from simple observance of its distribution compared to 

other minnows of the same genus (Mayden 2013).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 This species occurs in central and eastern Illinois and Ohio, states that border the Great Lakes. This species 

has been recorded in streams with temperatures as low as -0.5°C (Felley and Hill 1983) and as high as 25°C 

(Risch 2004).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9
253

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Due to the proximity of the range limits of the Steelcolor Shiner Minnow’s habitat and that of the Great Lakes 

basin, many of the abiotic factors of the two regions are the same. Suitable habitats for the Steelcolor Shiner 

Minnow are found in the Great Lakes basin.

 In several studies where the Steelcolor Shiner Minnow is native to a river system, the minnow shows mixed 

response to abiotic or environmental changes (Daulwater et al. 2008, Doll 2010, Felley 1983, Hocutt and Wiley 

1986, Mandrak and Cudmore 2010, Pritchett and Pyron 2011). It is less tolerant to current and food choices 

and may exhibit lower fecundity if habitat is disturbed.

 It is shown that when there is a higher level of biodiversity, the Steelcolor Shiner Minnow is present and doing 

well, though never outcompeting other minnow species unless it hybridizes (Mandrak and Cudmore 2010).

 This species occurs in central and eastern Illinois and Ohio, states that border the Great Lakes. This species 

has been recorded in streams with temperatures as low as -0.5°C (Felley and Hill 1983) and as high as 25°C 

(Risch 2004). 

 Cyprinella whipplei is a freshwater fish that inhabits rivers; salinity of its native and introduced ranges is very 

similar to the salinity ranges in the Great Lakes region. 

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 This species inhabits pools and riffles of low-to-moderate gradient streams with permanent flows (Ross 2001). 

These types of habitats are available in the Great Lakes region. 

 Cyprinella whipplei uses crevices in submerged logs for reproduction (Pflieger 1965). It is likely that logs with 

crevices are somewhat abundant in the streams in the Great Lakes basin. 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6
254

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

7

 The closest phylogenetic relatives of the Steelcolor Shiner Minnow, such as Notropis spiloptera exist in more 

Northern or colder regions (Doll 2010, Mayden 1989, Page and Burr 2011, Schönhuth and Mayden 2010), so 

the limiting factor for spread could be temperature tolerance.

 Given some inability to “hop” habitats and possibly pass through less hospitable habitats to spread its range, 

the steelcolor shiner minnow may benefit from a warmer winter season (Crossman and Cudmore 2000).

 There is no data on the Steelcolor Shiner Minnows increased or decreased success based on ice cover. It is a 

riverine minnow and may not tolerate completely surface-frozen conditions (Aadland and Kuitunen 2004, 

Clavero and Garcia-Berthou 2006).

 The Steelcolor Shiner Minnow may be limited or more successful in spreading to a new region based on 

changing streamflow patterns resulting from climate change. It is a stream and river minnow with specific 

habitat preferences, such as rate of current (Gozlan et al. 2010b, Hocutt and Wiley 1986, Trautman 1980), so 

altered stream flows will surely affect this fish. The nature of the effect is unknown. 

 It is native to Alabama and Louisiana, so warmer water temperatures and shorter ice cover may aid the 

establishment of Cyprinella whipplei.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 Cyprinella whipplei generally feeds on insects in the water column, and changes its diet seasonally (Ross 2001). 

They feed on terrestrial insects that fall into the stream in the summer and fall. Cyprinella whipplei shifts to 

feeding on benthic invertebrates during colder weather. During the winter and spring, they also feed on organic 

detritus. It preys on small crustaceans, mites, and earthworms (Stauffer 2007).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

9
255

assessed;

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

-60% total 

points (at 

end)
256

Lakes)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10 %

 It is well known that the Cyprinella whipplei is food for many larger animals including any gar, bass, sunfish, 

sturgeon, large chubs, kingfisher, heron species, and turtles (Mayden 2013). These fish and other species are 

common in many lakes and rivers of the Great Lakes basin (MDEQ 2008). However, this predation may be no 

different than for native minnow species of the Great Lakes. The predation may not prevent, improve, or lessen 

the establishment.

 There is a possibility that the Cyprinella whipplei could be susceptible to the Viral Hemorrhagic Septicemia 

Virus Strain, Genotype IVb that occurs in some Michigan fish (Faisal et al. 2012), and this could spread or 

subtract from its numbers during establishment though this has not been researched.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 The Steelcolor Shiner Minnow is motile in connecting streams (Trautman 1980).

 This species occurs in the Mississippi River; however, introduction events are prevented by electrical barriers 

between the Mississippi River and the Great Lakes. The size and frequency of inocula from other rivers near the 

Great Lakes basin is unknown. 

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
257

Unknown U

3

 It is uncertain in the literature as to how far north the native range for the Steelcolor Shiner always was (Gibbs 

1963, Hubbs and Cooper 1936, Page and Burr 2011, Robins et al. 1991), since there was a phylogenetic 

revision after 1938. Data prior to this date cannot be certain as to whether it was one or another species of 

minnow. However, there is a pattern in the DNR range maps with Cyprinella spiloptera and Cyprinella camura, 

as well as Cyprinella whipplei of a northward movement in range border over time (Cucherousset and Olden 

2011, Kulhanek et al. 2011).

 It is not known through research whether this spread is simply due to a fish’s mobility or if it involves direct or 

indirect human activity (e.g., bait bucket dumping or global warming).

 A survey conducted by Fisher et al. (1998) in 1994 found that Cyprinella whipplei had expanded its range in 

Tippecanoe County, Indiana since the mid-1970’s. A 1978 survey collected 2 specimens of Cyprinella whipplei, 

and the 1994 survey collected 16 specimens; however, the authors note that the historically low abundance of 

Cyprinella whipplei could be attributed to misidentification of this species during the 1978 survey (Fisher et al. 

1998).

 Although historically present in Indiana, Cyprinella whipplei was first recorded in the Kankakee River 

drainage in 1990 (Simon 1992).

 Cyprinella whipplei is established in Oklahoma (Fuller and Nico 2015a).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

1

 According to United States DNR fish survey range maps, there has been a slow progression of this Steelcolor 

Shiner Minnow species and related species in the same genus northward. 

 The letters NI (“regarded as native but possibly introduced”) and IP (“possibly introduced”) are used to 

indicate the areas where Cyprinella whipplei is considered a native and where is it considered a long-time 

invasive (Hocutt and Wiley 1986). These data are needed to distinguish whether this species has invaded 

successfully in the long-term or recent past or whether it is indigenous.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)
258

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 Other than dams and locks in place for energy or other needs, there is no known measure established 

specifically to block the Steelcolor Shiner Minnow. However, there are currently some blockages in place that 

are being monitored to prevent other known invasive fish species (Sparks 2010, United States 109th Congress 

2005).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 68

>100 High Adjustments

B. Critical species A*(1- 0%) 68

51-99 Moderate C. Natural enemy B*(1- 10%) 61.2

Control measures C*(1- 0%) 61.2

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Cyprinella whipplei if 

introduced to the Great Lakes is inadequate to support proper assessment.
259

There is insufficient information available to determine whether Cyprinella whipplei poses a threat to 

other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Cyprinella whipplei has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Cyprinella whipplei poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Cyprinella whipplei has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Cyprinella whipplei can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Though the Steelcolor Shiner has been studied in terms of its phylogeny (Mayden 1989, Page and Burr 2011)

and community relationships (Daulwater et al. 2008, Doll 2010, Felley 1983), but it has not been studied in 

terms of carrying toxins or pathogens.

 Some comparable studies have been done with the Viral Hemorrhagic Septicemia Virus strain, Genotype IVb 

that occurs in some Michigan fish (Faisal et al. 2012). This virus is known to infect similar species of minnow 

such as Notropis atherinoides (Emerald Shiner). However, a possible infection in the Steelcolor Shiner minnow 

could work to lower its established numbers as well as increase spread of the virus though no research has 

shown this.

 Another consideration in the invasion of a new minnow that has not been studied in the Steelcolor Shiner 

Minnow is its ability to carry and spread environmental toxins as a prey species though not create the toxins 

(Levengood and Schaeffer 2011, USEPA 1990).

E2) Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?
260

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

 No specific studies have been done on populations of the Steelcolor Shiner Minnow invading an area and 

outcompeting a native species. However, several studies have been done on environmental factors affecting 

stream communities (Aadland and Kuitunen 2004, Daulwater et al. 2008, Doll 2010, Felley 1983, Knouft and 

Page 2011). These studies never demonstrated that the Steelcolor Shiner Minnow has any advantage over other 

stream fish and in fact can be delicate in certain situations.

 Studies involving the Steelcolor Shiner Minnow in its native habitat, in which it is prey for larger fish common 

in the Great Lakes basin, do not show an increase in these larger, sport/food fishes (Doll 2010).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 No specific studies have been done on populations of the Steelcolor Shiner Minnow invading an area and 

significantly altering the predator-prey relationships in those waters. However, several studies have been done 

on environmental factors affecting stream communities (Aadland and Kuitunen 2004, Daulwater et al. 2008, 

Doll 2010, Felley 1983, Knouft and Page 2011). These studies often take into account the food web and the rise 

or decline of other populations. These studies and further descriptions of the Steelcolor Shiner’s habits (Page 

and Burr 2011, Smith 2002, Trautman 1980) show it has a delicate prey-specific diet of microinvertebrates as 

well as being prey for larger fish such as gar, bass, sunfish, sturgeon, large chubs, kingfisher, heron species, 

and turtles. These relationships may be normal to any prey minnow currently in the Great Lakes basin and not 

have a great impact, though no definitive proof is available (Ross et al. 2001).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √
261

 Specific studies have been done on the hybridization between the Steelcolor Shiner Minnow and other related 

species, specifically Cyprinella spiloptera which is present in most areas of the Great Lakes basin (Mayden 

pers. comm. 2013). The long-term results of this genetic blending is not known. After 1938 one species, 

Notropis whipplii, was renamed and two or more species became more specific and described by morphology 

and zoogeography including Cyprinella whipplei and Cyprinella spiloptera (Gibbs 1963, Hubbs and Cooper 

1936, Schönhuth and Mayden 2010). It is possible that hybridization can increase the range of such a minnow 

yet it could work to decrease its actual numbers.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 Though no study specific to the Steelcolor Shiner minnow was done to reveal that it has an effect on water 

quality, general knowledge about this fish as a minnow does not reveal any outstanding abilities. Its life cycle 

and habit generally mimic those of other native minnows to the Great Lakes basin (Hocutt and Wiley 1986, 

Hubbs and Cooper 1936, Trautman 1980).

 Some notable fish assemblage studies of cognate fish could reveal whether the Steelcolor Shiner Minnow has 

some affect that would permeate post-invasion (Knouft and Page 2011, Mueller and Pyron 2010, Pritchett and 

Pyron 2011, Taylor 2000).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 Though no study specific to the Steelcolor Shiner Minnow was done to reveal that it alters the physical qualities 

of a water ecosystem, general knowledge about this fish as a minnow does not reveal any outstanding abilities. 

Its life cycle and habit generally mimic those of other native minnows to the Great Lakes basin (Hocutt and 

Wiley 1986, Hubbs and Cooper 1936, Trautman 1980).

 Some notable fish assemblage studies of cognate fish could reveal whether the Steelcolor Shiner Minnow has 

some affect that would permeate post-invasion (Knouft and Page 2011, Mueller and Pyron 2010, Pritchett and 

Pyron 2011, Taylor 2000).

Environmental Impact Total 0
262

Total Unknowns (U) 5

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 The Steelcolor Shiner Minnow, like many other fishes, can carry common parasites. Given the proximity of its 

normal range (Page and Burr 2011) it is very likely that these threats are already present. There is no study 

specific to the levels of these hazards in Cyprinella whipplei but comparable studies and the abundant presence 

of its closest relative, Cyprinella spiloptera, in the Great Lakes gives confidence to the low risk of danger 

(Mayden 1989, USDA APHIS 2008).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U 

 Though no studies have been done on infrastructure damage of the Steelcolor Shiner Minnow, it is highly 

unlikely that it will do any more damage than minnows currently in the Great Lakes basin, especially its close 

phylogenetic relative, Cyprinella spiloptera.
263

 No evidence has been shown that the Steelcolor Shiner Minnow does any damage to physical structures or 

recreation areas in its native ranges. This specific risk assessment rank is based on the absence of studies or 

reports on this specific topic.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There is little published data on the steelcolor shiner minnow adversely affecting water quality (Neff and Killian 

2003, Pritchett and Pyron 2011). This minnow prefers less turbid, moderately moving riverine environments 

and is regarded as generally less tolerant of varied habitats. In its native range, it is not reported to alter the 

environment in which it inhabits (Mueller and Pyron 2010, Page and Burr 2011).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 This minnow is not reported to be farmed or raised in aquaculture (INDNR 2013). This is most likely due to its 

more delicate nature and preference for the pools of moderate running clear rivers (Hocutt and Wiley 1986, 

Mayden 2013).

 There is no report of the steelcolor Shiner Minnow in its ranges negatively affecting any economic, sport, 

recreational or agricultural setting. It does not outcompete other native minnows nor increase predator 

numbers who feed upon it (Daulwater et al. 2008, Doll 2010, Hocutt and Wiley 1986).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 In the studies related to river habitat changes and community relationships, no report of the Steelcolor Shiner 

Minnow having adverse effects on recreational tourism, fishing, water usage, etc. It is generally regarded as 

more delicate when living in the presence of a biodiversity and not present in harsher environments (Doll 2010, 

Mayden 2013).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
264

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 In the studies related to river habitat changes and community relationships, no report of the Steelcolor Shiner 

Minnow having adverse effects on aesthetic value or natural value. It is generally regarded as more delicate 

when living in the presence of a biodiversity and not present in harsher environments (Doll 2010, Mayden 

2013).

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There are no reports of the steelcolor shiner having any control ability over aquatic vegetation or harmful 

organisms. It is itself a predator of macroinvertebrates (Page and Burr 2011). This would affect a larger food 

web, (either beneficial or invasive) but no studies have been done on this effect.
265

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 Though there seems an obvious possibility of the Steelcolor Shiner being used as bait or reared in aquaculture 

for ponds or bait, in over 50 years of literature, it is never listed as being farmed or even attempted to be 

farmed (Hubbs et al. 1933, MIDNR 2013, Willoughby 1965, Yoder and Division 1950). This may be due to its 

more sensitive nature and its need for clean river flow and crevice spawning needs (Mayden 2013, Pflieger 

1965, Taylor 2000).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0

Unknown U √

 The fact that minnows serve as prey for larger sport and food fish is an important aspect of any minnow 

species. However, the effect of the Steelcolor Shiner Minnow in the Great Lakes basin has not been studied. It 

could be assumed that the effect of the more delicate steelcolor shiner minnow would have similar affects as the 

local, related minnows that are indigenous to this area.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U 

 No research exists demonstrating that the Steelcolor Shiner Minnow has medicinal or alternate research value. 

There is some research on related minnows such as the Bluntnose Shiner and the Emerald Shiner in terms of 

the effects of invasives, toxicity levels, and the VHS virus (Faisal et al. 2012, Levengood and Schaffer 2011, 

Winton et al. 2007).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1
266

Not significantly 0 √

Unknown U

 Though toxins can be found in the bodies of several related minnow species (Levengood and Schaeffer 2011), 

there is not research specific to the Steelcolor Shiner Minnow. There is little published data on this minnow 

removing significant levels from the water or adversely affecting the predators who feed on the minnows.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
267

Scientific Name: Hypophthalmichthys molitrix

Valenciennes in Cuvier and Valenciennes, 1844

Common Name: Silver Carp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Moderate

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Moderate

Transoceanic shipping: Low

Hypophthalmichthys molitrix has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Dispersal, Unauthorized Intentional Release, Escape from 

Commercial Culture, Transoceanic Shipping

Asian carp introduced to the Mississippi River basin via escape from aquaculture, identified as having 

relatively high probability of invasion if introduced to the Great Lakes (Herborg et al. 2007, Kolar and 

Lodge 2002, Kolar et al. 2005, Mandrak and Cudmore 2005, USEPA 2008); listed as having extensive 

invasion history (GISD 2006b). Potential pathway of introduction: inter-basin connections. Currently, 

large populations of Hypophthalmichthys molitrix (Silver Carp) are already established in nearby waters 

connected to the Great Lakes basin including the Illinois river and the Chicago Area Waterway System 

(Baerwaldt et al. 2013).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 
268

Unknown U

 Large populations of Silver Carp are established in the middle and lower segments of the Illinois River, the 

upper Illinois River (Waterway), and the Chicago Area Waterway System (CAWS) (Baerwaldt et al. 2013).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75 

√

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Large populations of Silver Carp are established in the middle and lower segments of the Illinois River, the 

upper Illinois River (Waterway), and the Chicago Area Waterway System (CAWS) (Baerwaldt et al. 2013).

 The United States Army Corps of Engineers (USACE) constructed a set of three electrical barriers, the first of 

which opened in 2002, on the Chicago Sanitary and Shipping Canal (CSSC) to prevent the spread of aquatic 

invasive species between the Great Lakes and Mississippi River basins (Baerwaldt et al. 2013).

 The closest location to Lake Michigan at which Silver Carp has been collected was in the Des Plaines River 

(river mile 290.2) at the confluence with the CSSC, north of Joliet, IL and downstream of the electric barriers 

(USGS 2012).

 While not indicative of live fish, environmental DNA (eDNA) of Silver Carp was been found in water samples 

collected above the electric barriers (i.e., closer to Lake Michigan) in 2012 from Lake Calumet, the Little 

Calumet River, the North Shore Channel, and the Chicago River (USACE 2012).

 Additional eDNA of silver carp has been found in Maumee Bay, Lake Erie (OH and MI waters) (MIDNR 2012).

 It remains unclear if any ponds could connect with the Lake Michigan watershed during flooding events, but the 

presence of Silver Carp in near by ponds does provide a source of individuals in close proximity for illegal 

movement (Cudmore et al. 2012).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
269

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Silver Carp are sometimes available in live food fish markets in several major United States and Canadian 

cities. Silver Carp has been placed on a watch list of freshwater food fish species in Ontario that had not yet 

been reported by importers or wholesalers, or been observed in retail markets, but that might become popular 

as a live food fish in the future. (Kolar et al. 2005).

 Also see (Mandrak and Cudmore 2005) regarding sale in Canada

The potential for purposeful, human-mediated releases of Bigheaded Carps into the Great Lakes basin does 

exist. Humans have illegally released freshwater fishes for sport opportunities (Crossman and Cudmore 1999a, 

Bradford et al. 2008) or spiritual/ethical reasons (Crossman and Cudmore 1999b, Severinghaus and Chi 1999, 

Shiu and Stokes 2008). This behavior of illegally releasing nonnative fishes into the aquatic environment is 

difficult to characterize and quantify (Bradford et al. 2008). For this reason, the rosk of intential release has 

not been quatified, but should be noted as a potential source of introduction of Bigheaded Carps into the Great 

Lakes basin (Cudmore et al. 2012).

 The live baitfish pathway is a potential entry pathway for the arrival of small Bigheaded Carps into the Great 

Lakes (Cudmore et al. 2012).

 Feeder fishes (typically Goldfish (Carassius auratus) shipped into the Great Lakes basin could be contaminated 

with Bigheaded Carps if they originated from fish farms in the Mississippi River basin. Fathead Minnows found 

in the bait industry in Michigan are known to originate from culture in Arkansas, Minnesota, North Dakota, 

and South Dakota.. However, the volume of such movement and the extent of contamination, if any, is unknown. 

Based on a subsample of live fish import records for 2006-2007, Fathead Minnows (likely rosy reds) imported 

for the aquarium trade originated primarily from Missouri and secondarily from North (Cudmore et al. 2012).

 It is currently illegal to possess or sell live Asian carps in Ontario; however, despite this legislation, Bighead 

Carp and Grass Carp were documented in shipments for import into Ontario. Eight entry records were 

recorded from January 2010 to August 2011 that listed Grass (9.8 mt) and Bighead (16.8 mt) Carps as species 

descriptions. All of the shipments originated from Arkansas (Cudmore et al. 2012).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5 

√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Most states prohibit the use of carp as baitfish with Michigan and Ontario specifically prohibiting the use of 

Asian Carp (Cudmore et al. 2012).

 Prohibition against using carp for bait in MN, WI, IN, MI, NY, Ontario, Quebec; whitelisted bait species in 

other GL states (Cudmore et al. 2012).

 Results from Drake’s (2011) study of the baitfish industry and AIS in Ontario suggest that the entry route of 

Bigheaded Carps into the Great Lakes basin through the baitfish pathway will be largely dependent on the 
270

specific baitfish activity within each jurisdiction such as: characteristics of harvest activity in relation to 

bigheaded carp source populations; angler use, movement patterns, release rates; and, the yearly volume and 

spatial distribution of angling events within and outside of the Great Lakes basin (Cudmore et al. 2012).

 A survey of bait shops in the Chicago area was conducted in 2010 to determine if Bigheaded Carp was present

in bait tanks, it used both visual and eDNA surveillance methods (Jerde et al. 2012). No Bighead or Silver 

Carps were observed or detected by visual inspections or eDNA analysis (Cudmore et al. 2012).

 The possession and sale of live Asian carps within the province of Quebec is currently legal, but prohibition 

regulations are posted for the public (Cudmore et al. 2012).

 There is also no international trade of Bigheaded Carps identified with the Lake Superior watershed. Lake 

Michigan was ranked low for human-mediated release; higher than for Lake Superior given the proximity of 

established populations as a source of available individuals. Lakes Huron and Ontario are associated with a 

low risk, taking into consideration the lack of movement of bait and trade from Bigheaded carp areas and these 

lakes. However, these lakes are exposed to stronger fisheries from American anglers compared to Lake 

Superior, and Lake Ontario is also the location of live markets that could be involved in illegal trade. The risk 

of direct arrival to Lake Erie is also low, taking into consideration the presence of a higher number of anglers 

in lakes St. Clair and Erie, the frequent use of live bait in the area, and the potential for accidental release from 

illegal shipping of Bigheaded Carps coming from Windsor towards Toronto. Certainty associated with humanmediated releases varies by lake from low to moderate (Cudmore et al. 2012).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Silver Carp are not currently raised or stocked as biological control agents to improve water quality in the 

United States, However, there is some interest within the aquaculture industry in potentially producing Silver 

Carp on a commercial scale in the future as part of Partitioned Aquaculture (Conover et al. 2007).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25 

√

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
271

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100 √

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U

 Silver carp are prohibited for United States import and interstate transport by the Lacey Act (USFWS 2006).

 Bigheaded carps, which are listed under the injurious wildlife provisions of the Lacey Act, cannot be legally 

imported into the United States or moved interstate live without a permit. Since 2005, the eight Great Lakes 

states have amended their rules and regulations to prohibit movement and/or possession of live Bigheaded 

Carps across their jurisdictions. Even with these regulations, enforcement could be improved, given that live 

Bighead Carp have been transported through United States (Cudmore et al. 2012).

 In Canada there is no federal legislation in place regarding import of aquatic species that may pose an invasion 

risk. The Ontario Ministry of Natural Resources (OMNR) has banned the live sale of Asian Carps through the 

Fish and Wildlife Conservation Act in 2004 and banned the live possession of Asian Carps through the Ontario 

Fishery Regulations in 2005 (Cudmore et al. 2012).

 Live silver carp are sometimes available in live food fish markets in several major United States and Canadian 

cities. Goodchild (1999) placed silver carp on a watch list of freshwater food fish species in Ontario that had 

not yet been reported by importers or wholesalers, or been observed in retail markets, but that might become 

popular as a live food fish in the future(Kolar et al. 2005).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5 

√

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 40
272

chain locker) while in its active or resting stage.

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0 √

Unknown U

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.75 75 Moderate

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0.25 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x 0.5 50 Moderate

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0 Low

Total Unknowns (U) 0 Confidence Level High
273

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Hypophthalmichthys molitrix has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: High).

Although Silver Carp has not been physically detected in the Great Lakes, environmental DNA (eDNA) 

has been found in water samples collected in several areas in 2012: above electric barriers from Lake 

Calumet, the Little Calumet River, the North Shore Channel, and the Chicago River (USACE 2012), as 

well as Maumee Bay, Lake Erie (MIDNR 2012).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Silver carp are freshwater fish, preferring large river systems, lakes, or impoundments with flowing water, 

which they need to spawn. They can feed in temperatures as low as 2.5°C (36.5°F) and can withstand low levels 

of oxygen(PA Sea Grant 2013).
274

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Overwinter mortality is correlated to length of winter and becomes more important with increasing latitude. It 

is not known to be an issue for Bigheaded Carps in the Mississippi River basin; Bigheaded Carp fingerlings 

have been collected from floodplain wetlands in spring in years when the wetlands were not connected to the 

river. Overwinter mortality may influence the northern limits of the native range of Bigheaded Carps, but has 

not been modelled specifically for these species in North America. Ecological niche modeling predicting the 

potential North American distribution of Bigheaded Carps indicated that they could survive well north of the 

Great Lakes basin (Herborg et al. 2007); therefore, overwinter mortality will likely not be a limiting factor in 

most years (Cudmore B. et al. 2012).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

5

 The Silver Carp has unique, sponge-like and porous gill rakers capable of straining phytoplankton down to 4 lm 

in diameter (Robison and Buchanan 1988). Adults feed primarily on phytoplankton, but Silver Carp larvae feed 

on zooplankton (Chen et al. 2006).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3
275

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Silver Carp are thought to deplete plankton stocks for native larval fishes and mussels (Laird and Page 1996). 

They might be direct competitors for the adults of native species who feed on plankton, such as Paddle-fish 

(Polyodon spatula), Bigmouth Buffalo (Ictiobus bubalus) and the Gizzard Shad (Dorosoma cepedianum) (Chen 

et al. 2006).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Bigheaded Carps are known to spawn in rivers and it is believed that flood events are a primary spawning cue 

(Kolar et al. 2007). In its native range, Bighead Carp has a fecundity ranging from 280,000-1.1 million eggs 

(Kolar et al. 2007). In North America, fecundity ranged from 4,792-1.6 million eggs (Kipp et al. 2011). In its 

native range, Silver Carp has a fecundity ranging from 299,000-5.4 million eggs (Kolar et al. 2007). In North 

America, it has ranged from 26,650- 3.7 million eggs (Kipp et al. 2011).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

ENVIRONMENTAL COMPATIBILITY
276

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes

region)

3

Not similar 0

Unknown U

8

 Ecological niche modeling predicting the potential North American distribution of Bigheaded Carps indicated 

that they could survive well north of the Great Lakes basin (Herborg et al. 2007); therefore, overwinter 

mortality will likely not be a limiting factor in most years (Cudmore et al. 2012).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Ecological niche modeling predicting the potential North American distribution of Bigheaded Carps indicated 

that they could survive well north of the Great Lakes basin (Herborg et al. 2007); therefore, overwinter 

mortality will likely not be a limiting factor in most years (Cudmore et al. 2012).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

5

 Recent studies have examined the suitability of Great Lakes tributaries for Bigheaded Carp spawning based on 

more detailed considerations of reproductive biology. Kocovsky et al. (2012) examined eight American 

tributaries in the central and western basins of Lake Erie. They concluded that the three larger tributaries were 
277

thermally and hydrologically suitable to support spawning of Bigheaded Carps, four tributaries were less 

suited, and that one was ill suited. Mandrak et al. (2011) conducted a similar analysis for the 25 Canadian 

tributaries of the Great Lakes. They concluded suitable spawning conditions were present in nine of 14 

tributaries to Lake Superior with sufficient data; however, only one of the nine tributaries had a mean annual 

total degree-days exceeding 2,685. Therefore, Bigheaded Carps are unlikely to mature within Lake Superior 

tributaries, but may encounter sufficient growing degree-days to mature in some parts of Lake Superior such as 

near shore and bays. Mandrak et al. (2011) concluded suitable spawning conditions, including growing degreedays required for maturation, were present in 23 of 27 tributaries to Lake Huron, nine of 10 tributaries to Lake 

Erie, and 16 of 28 tributaries to Lake Ontario. Studies have not been conducted for United States tributaries in 

lakes Michigan, Huron, Superior, Ontario, nor the eastern basin of Lake Erie, but the analyses of Kocovsky et 

al. (2012) and Mandrak et al. (2011) suggest that access to tributaries with suitable thermal and hydrologic 

regimes in the Great Lakes should not limit spawning by Bigheaded Carps (Cudmore et al. 2012).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8
278

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 This species does not require another species for critical stages.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 Silver Carp will not be aided by the establishment of any other species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
279

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Silver Carp are not found to have any predators or enemies. 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
280

Unknown U

9

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-40%

 Asian Carp management and control plans can be used for Silver Carp.

 Asian Carp Control Strategy Framework can be used for Silver Carp.

 Asian Carp Regional Coordinating Committee can be used for Silver Carp.

 Asian Carp Monitoring and Rapid Response Plan can be used for Silver Carp.

 eDNA monitoring can be used for Silver Carp.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 102

>100 High Adjustments
281

B. Critical species A*(1- 0%) 102

51-99 Moderate C. Natural enemy B*(1- 0%) 102

Control measures C*(1- 40%) 61.2

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Hypophthalmichthys molitrix has a high potential environmental impact in the Great Lakes.

Silver Carp is an efficient filter feeder which competes with virtually every fish species that which 

forages on planktonic organisms during their early life history stages (Chick and Pegg 

2001). Interspecific competition for resources is known to cause pronounced and frequent declines in the 

physical condition of native fish when plankton resources are limited. Ultimately, declines in body 

condition may decrease potential fitness and the long-term sustainability of native fishes (Irons et al. 

2007). Meso- and microcosm studies (Domaizon and Devaux 1999b, Spataru and Gophen 1985, Starling 

1993) provide supporting evidence that high consumption caused by the superior filter efficiency and 

large size (>35 kg) of Silver Carp, may disproportionately deplete plankton and/or alter the assemblage of 

zooplankton communities, consequently modifying food web structure (Irons et al. 2007, Pongruktham et 

al. 2010).

These fish can excrete their own weight in 10 days (Herodek et al. 1989). This sediment enrichment has 

an ultimate negative effect on water quality. Studies (Lieberman 1996, Starling 1993) demonstrated that 

high biomass of Silver Carp causes increases in inorganic nitrogen and phosphorus levels. Decreases in 

zooplankton populations resulted in consequent increases in chlorophyll a and turbidity.

The Silver Carp has been known to be a carrier of the Asian tapeworm after the pathogen was found in 

Silver Carp stocks in the former U.S.S.R. and Philippines (Kolar et al. 2007). The Asian tapeworm, a

cestode capable of being transferred to other fishes of several different orders, has minimal effects on 

Silver Carp but can cause severe or even lethal intestinal damage to novel hosts (Kolar et al. 2005). In 
282

addition, Kolar et al. (2005) points out that this parasite has been found in several species of native North 

American fishes, including several endangered species.

Hypophthalmichthys molitrix has a high potential socio-economic impact in the Great Lakes.

One of the behaviors observed in Silver Carp is responsible for significant negative impact on the 

recreational/tourism sector. Silver Carp regularly jump out of the water, particularly in response to 

outboard motors. These leaps cause collisions between boaters and fish and have been the source of

numerous reports of injuries to human beings and damage to boats and boating equipment. Silver Carp 

also causes property damage including broken radios, depth finders, fishing equipment, and antennae 

(USFWS 2006). Jumping of Silver Carp (at least 10 feet out of the water) can result in serious injuries to 

boaters and it is probable that collisions between boaters and jumping Silver Carp will eventually result in 

human fatalities (Hoff 2004).

Silver Carp are known to harbor several disease-causing agents that pose health risks to humans. These 

pathogen have been mostly found in carp from different parts of Iran. They include Listeria 

monocytogenes (found in market and fish farm samples), Clostridium botulinum (found in 1.1% of fresh 

and smoked samples from the Mazandaran Province), the toxigenic fungi Aspergillus flavus, Alternaria, 

Penicillium, and Fusarium (found from silver carp and from pond water in which they were raised) 

(USFWS 2006). Furthermore, Silver Carp can be considered a potential carrier for Salmonella (S. 

typhimumium) (USFWS 2006).

These fish compete with native species that are important as sport and food species and whose decline 

could result in a negative economic impact on recreational angling and other industries that benefit from 

sport fishing, such as tourism (Kolar et al. 2005).

Hypophthalmichthys molitrix has the potential for moderate beneficial effects if introduced to the 

Great Lakes.

Silver Carp are of high commercial importance in many parts of the world. According to Kolar (2005) 

more Silver Carp are produced than any other species of freshwater fish in the world, especially in China 

where it continues to grow in importance. In the US, commercial harvest of silver carp is increasing in 

parts of the Mississippi River Basin (Conover et al. 2007). The combined annual commercial harvest of 

Bighead and Silver Carps from the Mississippi and Illinois rivers within Illinois increased from less than 

600 kg per year between 1988 and 1992 to in excess of 50,000 kg per year since 1997 (Chick and Pegg 

2001). A consumer market for Asian Carp species is being investigated in the United States and fishing

tournaments for Silver carp are starting to develop in the US.

Silver Carp are frequently subjects of biomanipulation research with the purpose of cleaning wastewaters 

and eutrophic lakes (Domaizon and Devaux 1999b, Henderson 1978, Spataru and Gophen 1985, Starling 

1993). These filter feeding fish were utilized in Henderson’s (1978) field tests in order to determine their 

capabilities in controlling excessive plankton blooms and converting nutrients into usable proteins. 

Henderson found that the presence of the fish did affect plankton removal and stimulate nutrient uptake. 

Nonetheless, more recent studies (Domaizon and Devaux 1999, Spataru and Gophen 1985, Starling 1993) 

had contradictory results; therefore the ability of Silver Carp to control water quality remains unknown.

Silver Carp’s ability as a biological agent for controlling cyanobacteria blooms has also been widely 

debated. Although cyanobacteria produce toxins that can be noxious to animals and humans, Silver Carp 

possess natural defenses against these microcystins and are known to consume blue-green algae (Xie et al. 

2004). Miura (1990) has attributed phytoplankton community shifts from blue-green algae domination 
283

towards green algae to grazing by silver carp (Kolar et al. 2005). On the other hand, Kucklentz (1985) 

found that blue-green algae, as well as total phytoplankton, increased rather than decreased after stocking 

Silver Carp (Kolar et al. 2005).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U

 The silver Carp has been known to be a carrier of the Asian tapeworm after the pathogen was found in silver 

carp stocks in the former U.S.S.R. and Philippines (Kolar et al. 2007). The Asian tapeworm, a cestode capable 

of being transferred to other fishes of several different orders, has minimal effects on Silver Carp but can cause 

severe or even lethal intestinal damage to novel hosts (Kolar et al. 2005). In addition, Kolar et al. (2005) points 

out that this parasite has been found in several species of native North American fishes, including several 

endangered species.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Silver Carp is a filter feeder. Being efficient consumers of phytoplankton, cyanobacteria, and zooplankton, the 

Silver Carp competes with virtually every fish species in the Mississippi River basin that forage on planktonic 

organisms (Chick and Pegg 2001). Furthermore, Silver Carp has been found to have an overlapping diet with 

two native Great Lakes filter-feeder species, the Gizzard Shad and the Bigmouth Buffalo (Sampson et al. 2009). 

The interspecific competition for resources resulting from this overlap is known to cause pronounced and 

frequent declines in the physical condition of these native fish if plankton resources are limited. Ultimately, 

declines in body condition may decrease potential fitness and the long-term sustainability of Gizzard Shad, 

Bigmouth Buffalo, and other native riverine fishes (Irons et al. 2007).

E3) Does it alter predator-prey relationships? 
284

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 Mesocosmic and microcosmic studies carried out in lakes in France, Brazil, and Israel (Domaizon and Devaux 

1999b, Spataru and Gophen 1985, Starling 1993) provide supporting evidence that high consumption caused by 

the superior filter efficiency and large size (>35 kg) of Silver Carp, may disproportionately deplete plankton 

and/or alter the assemblage of zooplankton communities, consequently modifying food web structure (Irons et 

al. 2007, Pongruktham et al. 2010).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 √

Not significantly 0 

Unknown U

 The possibility of Silver Carp as a bio-tool for improving water quality (by filtering phytoplankton and detritus) 

is still disputed. Some of the most recent studies (Lieberman 1996, Starling 1993) demonstrated that high 

biomass of Silver Carp causes increases in inorganic nitrogen and phosphorus levels. Decreases in zooplankton 

populations were shown, which in turn cause increases in microphytoplankton and consequently increases in 

chlorophyll a and turbidity. The increase in nutrient levels can be explained by the amount of feces excreted by 

Silver Carp. These fish can excrete their own weight in 10 days (Herodek et al. 1989). This sediment enrichment 

has an ultimate negative effect on water quality.
285

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 

Unknown U

 The highly efficient filtering abilities of Silver Carp, aided by the complexity of their relationship with 

phytoplankton and zooplankton communities, leads to changes in phytoplankton assemblage via the impact on 

herbivorous zooplankton (Domaizon and Devaux 1999b).

Environmental Impact Total 15

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √

Not significantly 0 

Unknown U
286

 Silver Carp is known to harbor several disease-causing agents that pose health risks to humans. These 

pathogen have been mostly found in carp from different parts of Iran. They include Listeria monocytogenes

(found in market and fish farm samples), Clostridium botulinum (found in 1.1% of fresh and smoked samples 

from the Mazandaran Province), the toxigenic fungi Aspergillus flavus, Alternaria, Penicillium, and Fusarium

(found from silver carp and from pond water in which they were raised) (USFWS 2006). Furthermore, silver 

carp can be considered a potential carrier for Salmonella (S. typhimumium) (USFWS 2006).

 It should also be noted that the jumping of Silver Carp (at least 10 feet out of the water) can result in serious 

injuries to boaters and it is probable that collisions between boaters and jumping Silver Carp will eventually 

result in human fatalities (Hoff 2004).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U √

 While the increased competition and habitat disruption may impact commercially-fished species, there has 

never been any formal analysis of this impact.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U
287

 Silver Carp regularly jump out of the water, particularly in response to outboard motors. These leaps cause 

collisions between boaters and fish and have been the source of numerous reports of injuries to human beings 

and damage to boats and boating equipment. Reported injuries include cuts from fins, black eyes, broken bones, 

neck and back injuries, and concussions. Silver Carp also causes property damage including broken radios, 

depth finders, fishing equipment, and antennae (USFWS 2006). Additionally, when a Silver Carp lands in a 

boat, it often leaves slime, scales, feces, and blood for boaters to contend with (Kolar et al. 2005). These fish 

also compete with native species that are important as sport and food species and whose decline could result in 

a negative economic impact on recreational angling and other industries that benefit from sport fishing, such as 

tourism (Kolar et al. 2005).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 7

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
288

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √

Not significantly 0 

Unknown U

 The ability if Silver Carp as a biological agent for controlling cyanobacteria blooms has been widely debated. 

Although cyanobacteria produce toxins that can be noxious to animals and humans, Silver Carp possess natural 

defenses against these microcystins and are known to consume blue-green algae (Xie et al. 2004). Miura (1990) 

has attributed phytoplankton community shifts from blue-green algae domination towards green algae to 

grazing by Silver Carp (Kolar et al. 2005). On the other hand, Kucklentz (1985) found that blue-green algae, as 

well as total phytoplankton, increased rather than decreased after stocking Silver Carp (Kolar et al. 2005); 

therefore the use of Silver Carp to control blue-green algae is not fully understood and has been met with 

varied success (Kolar et al. 2005).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Silver Carp are of high commercial importance in many parts of the world. According to Kolar (2005) more 

Silver Carp are produced than any other species of freshwater fish in the world, especially in China where it 

continues to grow in importance. In the US, commercial harvest of Silver Carp is increasing in parts of the 

Mississippi River basin (Conover et al. 2007). The combined annual commercial harvest of Bighead and Silver 

Carps from the Mississippi and Illinois rivers within Illinois increased from less than 600 kg per year between 

1988 and 1992 to in excess of 50,000 kg per year since 1997 (Chick and Pegg 2001).

 A consumer market for Asian Carp species is being investigated in the US.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Fishing tournaments for Silver Carp are starting to develop in the US.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √
289

Not significantly 0 

Unknown U

 Silver Carp are frequently subjects of biomanipulation research with the purpose of cleaning wastewaters and 

eutrophic lakes (Domaizon and Devaux 1999b, Henderson 1978, Spataru and Gophen 1985, Starling 1993).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 

Unknown U √

 The feeding habits of Silver Carp make this species capable of converting primary production into fish flesh 

without supplemental feeding. These filter feeding fish were utilized in Henderson’s (1978) field tests in order to 

determine their capabilities in controlling excessive plankton blooms and converting nutrients into usable 

proteins. Henderson found that the presence of the fish did affect plankton removal and stimulate nutrient 

uptake. Nonetheless, more recent studies (Domaizon and Devaux 1999, Spataru and Gophen 1985, Starling 

1993) had contradictory results; therefore the ability of Silver Carp to control water quality remains unknown.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U 

 According to Opuszynski 1981 and Yashouv 1971, culturing Silver Carp with other species can be an efficient 

method of increasing fishery production. It has been reported that the presence of Silver Carp in polyculture 

improves growth of Common Carp and Tilapias because benthic fishes cause resuspension of organic matter 

(Kolar et al. 2005). However, these species are not native to the Great Lakes.

Beneficial Effect Total 4

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
290

0 ≥2

Unknown

1 ≥1
291

Scientific Name: Hypophthalmichthys nobilis

Richardson, 1845

Common Name: Bighead Carp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Moderate

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Low

Escape from commercial culture: Moderate

Transoceanic shipping: Low

Hypophthalmichthys nobilis has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Dispersal, Unauthorized Intentional Release, Escape from 

Commercial Culture, Transoceanic Shipping

Asian Carp introduced to the Mississippi River basin via escape from aquaculture, identified as having 

relatively high probability of invasion if introduced to the Great Lakes (Herborg et al. 2007, Kolar et al. 

2005, Mandrak and Cudmore 2005, Rixon et al. 2005, USEPA 2008); listed as having extensive invasion 

history (GISD 2005c) and as invasive in the Baltic Sea (Leppäkoski and Olenin 2000). Potential pathway 

of introduction: inter-basin connections.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Three Bighead Carp adults were collected in Lake Erie between 1995 and 2000 (Baerwaldt et al. 2013), but 

they are not thought to represent an established population. The body condition of these individuals were 

healthy, but the individuals dissected, had reproductive organs that were not viable (Cudmore et al. 2012).
292

 Large populations of Bighead Carp are established in the middle and lower segments of the Illinois River, the 

upper Illinois River (Waterway), and the Chicago Area Waterway System (CAWS) (Baerwaldt et al. 2013).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 

0.75 √

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 

0.25

Unknown U

 Large populations of Bighead Carp are established in the middle and lower segments of the Illinois River, the 

upper Illinois River (Waterway), and the Chicago Area Waterway System (CAWS) (Baerwaldt et al. 2013).

 Bighead Carp individuals have also been collected in isolated Chicago lagoons (e.g., Schiller Park Pond, 

Columbus Park Lagoon, Garfield Park Lagoon, McKinley Park Lake, Flatfoot Lake) closer to Lake Michigan 

(Baerwaldt et al. 2013). In 2008, a Bighead Carp was found in Lincoln Park South Lagoon, which connects to 

Lake Michigan via a screened overflow drain; this pond was poisoned and drained in late 2008 (Willink 2009).

 Bighead Carp is found in ponds that could connect with the Lake Michigan watershed during flooding events, 

which provides a source of individuals in close proximity for illegal movement (Cudmore et al. 2012).

 The United States Army Corps of Engineers (USACE) constructed a set of three electrical barriers, the first of 

which opened in 2002, on the Chicago Sanitary and Shipping Canal to prevent the spread of aquatic invasive 

species between the Great Lakes and Mississippi River basins; only one live Bighead Carp has been found 

(Lake Calumet in 2010) in the waterway above the barrier (Baerwaldt et al. 2013). A dead individual was found 

on the shore of Lake George, Indiana (Baerwaldt et al. 2013).

 While not indicative of live fish, environmental DNA (eDNA) of Bighead Carp was been found in water samples 

collected above the electric barriers (i.e., closer to Lake Michigan) in 2012 from Lake Calumet (USACE 2012).

 There are no known Bigheaded Carps in or near the St. Lawrence River. Should they gain access to the St. 

Lawrence River, through ballast water or via natural dispersal, would have a direct route to Lake Ontario 

(Cudmore et al. 2012).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?
293

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 The potential for purposeful, human-mediated releases of Bigheaded Carps into the Great Lakes basin does 

exist. Humans have illegally released freshwater fishes for sport opportunities (Crossman and Cudmore 1999a, 

Bradford et al. 2008) or spiritual/ethical reasons (Crossman and Cudmore 1999b, Severinghaus and Chi 1999, 

Shiu and Stokes 2008). This human behavior of illegally releasing nonnative fishes into the aquatic environment 

is difficult to characterize and quantify; therefore it is difficult to qualify the risk of intentional release, but it 

should be noted as a potential source of introduction for Bigheaded Carps into the Great Lakes basin (Cudmore 

et al. 2012).

 Being used as a live baitfish is a potential pathway for the arrival of small Bigheaded Carps into the Great 

Lakes (Cudmore et al. 2012).

 Feeder fishes (typically Goldfish (Carassius auratus) or “rosy reds”, colour variant of Fathead Minnow 

(Pimephales promelas), shipped into the Great Lakes basin could be contaminated with Bigheaded Carps if they 

originated from fish farms in the Mississippi River basin. Fathead Minnows found in the bait industry in 

Michigan are known to originate from culture in Arkansas, Minnesota, North Dakota, and South. However, the 

volume of such movement and the extent of contamination remains unknown (Cudmore et al. 2012).

 It is currently illegal to possess or sell live Asian Carps in Ontario; however, despite this legislation, Bighead 

Carp and Grass Carp have been documented in shipments for import into Ontario (Cudmore et al. 2012).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species is 

prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5 

√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Most states prohibit the use of carp as baitfish. Michigan and Ontario specifically prohibiting the use of Asian 

carps (Cudmore et al. 2012)

 There is prohibition against using carp for bait in MN, WI, IN, MI, NY, Ontario, Quebec (Cudmore et al. 2012)

 Drake (2011) conducted a study of the baitfish industry and AIS in Ontario the results suggested that the entry 

route of Bigheaded Carps into the Great Lakes basin through the baitfish pathway will be largely dependent on 

the specifics of baitfish activity within each jurisdiction such as: characteristics of harvest activity in relation to 

bigheaded carp source populations; angler use, movement patterns, release rates; and, the yearly volume and 

spatial distribution of angling events within and outside of the Great Lakes basin (Cudmore et al. 2012)
294

 A survey of bait shops in the Chicago area was conducted in 2010 to determine presence of bigheaded carps in 

bait tanks using both visual and eDNA surveillance methods (Jerde et al. 2012). No Bighead or Silver Carps 

were observed or detected by visual inspections or eDNA analysis (Cudmore et al. 2012).

 The possession and sale of live Asian carps within the province of Quebec is currently legal, but there are 

prohibition regulations for the public (Cudmore et al. 2012).

 There is also no international trade of Bigheaded Carps identified with the Lake Superior watershed. Lake 

Michigan was ranked low for human-mediated release; higher than for Lake Superior given the proximity of 

established populations as a source of available individuals. Lakes Huron and Ontario are associated with a 

low risk, taking into consideration the lack of movement of bait and trade from Bigheaded Carp. However, 

these lakes are exposed to stronger fisheries from American anglers compared to Lake Superior, and Lake 

Ontario is also the location of live markets that could be involved in illegal trade. The risk of direct arrival to 

Lake Erie is also low, taking into consideration the presence of a higher number of anglers in lakes St. Clair 

and Erie, the frequent use of live bait in the area, and the potential for accidental release from illegal shipping 

of bigheaded carps coming from Windsor towards Toronto. (Cudmore et al. 2012).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 There are many ponds and artificial lakes in the Chicago metropolitan area. They are commonly stocked for 

fishing with Channel Catfish (Ictalurus punctatus). Channel Catfish are often purchased from southern fish 

farmers, where it is possible for the stock to be contaminated with small Bighead Carp (Cudmore et al. 2012).

 Fewer catfish farmers are raising Bighead Carp since the species was listed as ‘injurious’ under the Injurious 

Wildlife provisions of the Lacey Act. The Act prohibits interstate transport of live Bighead Carp (Cudmore et al. 

2012).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 

0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 

0.25 √

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
295

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100 √

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U

 Bigheaded Carps are listed under the injurious wildlife provisions of the Lacey Act and cannot be legally 

imported into the United States or moved interstate live without a permit. Since 2005, the eight Great Lakes 

states have amended their rules and regulations to prohibit movement and/or possession of live Bigheaded 

Carps across their jurisdictions. Even with these regulations fishes were seized in Canada in 2010-2011

(Cudmore et al. 2012).

 In Canada, there is no federal legislation in place regarding import of aquatic species that may pose an 

invasion risk. The Ontario Ministry of Natural Resources (OMNR) has banned the live sale of Asian Carps 

through the Fish and Wildlife Conservation Act in 2004 and banned the live possession of Asian Carps through 

the Ontario Fishery Regulations in 2005 (Cudmore et al. 2012).

 Some illegal shipment attempts into Ontario have been stopped by Canadian enforcement officers. In November 

2010, there was a seizure at the Bluewater Bridge, Sarnia of 1,136 kg of Bighead Carp and 727 kg of Grass 

Carp after officers from both Canada Border Services Agency and OMNR inspected incoming shipments of live 

and fresh fishes. In March 2011, a fish importer was fined $50,000 for transporting live Bighead Carp (nearly 

2,500 kg) from the United States across the Windsor- Detroit border. A few days later, an Indiana company was

caught bringing live Bighead Carp (2,727 kg) into Canada and was fined $20,000. All fishes originated in 

Arkansas and were headed to live fish markets in the Toronto area (Cudmore et al. 2012).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 

0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5 

√

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 

0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80
296

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Unlike the ballast water in freighters that originate outside of the Great Lakes, ballast water in freighters that 

remain in the St. Lawrence River basin are not treated for AIS in any way. If Bigheaded Carps were to become 

established first in the St. Lawrence River, the freighter movement may facilitate the arrival of the species into 

the Great Lakes basin (Cudmore et al. 2012).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with the 

Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0 √

Unknown U
297

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Hypophthalmichthys nobilis has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: High).

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.75 75 Moderate

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 0.25 25 Low

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x 0.5 50 Moderate

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0 Low

Total Unknowns (U) 0 Confidence Level High
298

Asian Carp introduced to the Mississippi River basin via escape from aquaculture are identified as having 

relatively high probability of invasion if introduced to the Great Lakes (Herborg et al. 2007, Kolar et al. 

2005, Mandrak and Cudmore 2005, Rixon et al. 2005, USEPA 2008); they are listed as having extensive 

invasion history (GISD 2005c) and as invasive in the Baltic Sea (Leppäkoski and Olenin 2000). Potential 

pathway of introduction: inter-basin connections.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-saturated), 

AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive in 

a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Bighead Carp have been able to establish themselves in a wide range of environments with a wide range of 

temperatures and lower salinity levels.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Bighead Carp are known to be able to tolerate a wide variety of temperature but their locations in Asia suggest 

their ability to withstand the Great Lake waters during the winter period.

 Overwinter mortality is correlated to length of winter and becomes more important with increasing latitudes. It 

is not known to be an issue for Bigheaded Carps in the Mississippi River basin; Bigheaded Carp fingerlings are 

collected from floodplain wetlands in the spring in years when those wetlands were not connected to the river. 

Overwinter mortality may influence the northern limits of the native range of Bigheaded Carps, but this has not 

been modelled for these species in North America. Ecological niche modeling in their native range predicts the 

potential for North American distribution of Bigheaded Carps and indicated that they could survive well north 

of the Great Lakes basin (Herborg et al. 2007); therefore, overwinter mortality would likely not be a limiting 

factor in most years (Cudmore B. et al. 2012).
299

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

5

 Bighead Carp are bottom feeders feeding mostly on zooplankton and often algae. 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there are 

few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species in 

the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Bighead Carp are expected to outcompete for food source in native species and could affect the prey of top 

predators in the Great Lakes.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

5

 The fecundity of Bigheaded Carp seems comparable to other species in the same taxonomic group.

 Bigheaded carps are known to spawn in rivers and it is believed that a flood event is the primary spawning cue 

(Kolar et al. 2007). In its native range, Bighead Carp has a fecundity ranging from 280,000-1.1 million eggs 
300

(Kolar et al. 2007). In North America, fecundity ranged from 4,792-1.6 million eggs (Kipp et al. 2011). In its 

native range, Silver Carp has a fecundity ranging from 299,000-5.4 million eggs (Kolar et al. 2007). In North 

America, it has ranged from 26,650- 3.7 million eggs (Kipp et al. 2011).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Bighead Carp need large, turbulent rivers and higher temperatures to spawn. The eggs float for 40-60 hours 

before hatching (Chen et al 2007). Only some rivers emptying into the Great Lakes are sufficient of this 

characteristic and at only parts of the year.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Bighead carp’s native regions are quite compatible to many regions in the United States and have already been 

found in areas surrounding the Great Lakes basin.

 Ecological niche modeling has predicted the potential for North American distribution of Bigheaded Carps and 

has indicated that they could survive well north of the Great Lakes basin (Herborg et al. 2007); therefore, 

overwinter mortality will likely not be a limiting factor (Cudmore B. et al. 2012).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?
301

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Ecological niche modeling has predicted the potential for North American distribution of Bigheaded Carps and 

has indicated that they could survive well north of the Great Lakes basin (Herborg et al. 2007); therefore, 

overwinter mortality will likely not be a limiting factor (Cudmore B. et al. 2012).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

5

 The habitats needed for reproduction are more commonly found in rivers than in lakes. Bighead Carp need 

large, turbulent rivers and higher temperatures to spawn. The eggs float for 40-60 hours before hatching. Only 

some rivers emptying into the Great Lakes are sufficient of this characteristic and at only parts of the year.

 Two recent studies examined the suitability of Great Lakes tributaries for Bigheaded Carp spawning based on 

detailed considerations of reproductive biology. Kocovsky et al. (2012) examined eight American tributaries in 

the central and western basins of Lake Erie. They concluded that the three larger tributaries were thermally 

and hydrologically suitable to support spawning of Bigheaded Carps, four tributaries were less suited, and that 

one was ill suited. Mandrak et al. (2011) conducted a similar analysis for the 25 Canadian tributaries of the 

Great Lakes. They concluded suitable spawning conditions were present in nine of 14 tributaries to Lake 

Superior with sufficient data; however, only one of the nine tributaries had a mean annual total degree-days 

exceeding 2,685. Therefore, Bigheaded Carps are unlikely to mature within Lake Superior tributaries, but may 

encounter sufficient growing degree-days to mature in some parts of Lake Superior such as near shore areas 

and bays. Mandrak et al. (2011) concluded suitable spawning conditions, including growing degree-days 

required for maturation, were present in 23 of 27 tributaries to Lake Huron, nine of 10 tributaries to Lake Erie, 

and 16 of 28 tributaries to Lake Ontario. Similar studies have not been conducted for United States tributaries 

in lakes Michigan, Huron, Superior, Ontario, nor the eastern basin of Lake Erie, but the analyses of Kocovsky 

et al. (2012) and Mandrak et al. (2011) suggest that access to tributaries with suitable thermal and hydrologic 

regimes in the Great Lakes should not limit spawning by bigheaded carps (Cudmore B. et al. 2012).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 9
302

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 This species would be able to adapt to the effects of climate change and would allow for longer periods of 

reproduction.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 It would be highly likely for the Bighead Carp to find an appropriate food source but the amount they eat might 

not be sufficiently found in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 0
303

the Great Lakes but is likely to be introduced

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 This species does not require another species for critical stages.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 Bighead Carp will not be aided by the establishment of any other species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0
304

Unknown U

0

 Bighead Carp are not found to have any predators or enemies. 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

1

 There are control measures to try and stop the introduction of bighead into the Great Lakes.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Bighead Carp have established in Europe and the Mississippi River.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3
305

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 Bighead Carp were able to establish themselves rapidly once introduced into habitats with the right conditions.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-40%

 Asian Carp management and control plans can be used for Bigheaded Carp.

 Asian Carp Control Strategy Framework can be used for Bigheaded Carp.

 Asian Carp Regional Coordinating Committee can be used for Bigheaded Carp.

 Asian Carp Monitoring and Rapid Response Plan can be used for Bigheaded Carp.

 eDNA monitoring can be used for Bigheaded Carp.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 100

>100 High Adjustments

B. Critical species A*(1- 0%) 100

51-99 Moderate C. Natural enemy B*(1- 0%) 100

Control measures C*(1- 40%) 60

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low High
306

>9 Very low Confidence Level

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Hypophthalmichthys nobilis has a high potential environmental impact in the Great Lakes.

Bighead Carp is a powerful filter-feeder with a wide food spectrum that grows fast and reproduces 

quickly (Xie and Chen 2001), which makes this species a strong competitor. Within its native China, 

Bighead Carp are considered invasive and are associated with declines in native planktivorous fishes 

when translocated outside their natural range (Li and Xie 2002). Xie and Chen found that stocking of 

bighead carp into the plateau lakes of China had disastrous effects on endemic fishes, especially filterfeeding, endemic Barbless Carp (Cyprinus pellegrini). The catch of barbless carp, that once represented 

50% of yield of total fishes caught, declined to 20% in the 1960s, to 10% in the early 1970s, and 

plummeted to <1% in the 1980s.

The species also poses a threat to the ecology of the Mississippi River Basin and connecting aquatic 

ecosystems. These fish are capable of significantly reducing zooplankton abundance, which adversely 

affects all fish in their early life stages when their diets are strictly planktonic (Chick and Pegg 2001, Xie 

and Chen 2001). Furthermore, Bighead Carp compete with fish that are filter-feeders as adults, such as 

paddlefish. Several studies have showed that when zooplankton is limited, bighead carp has a competitive 

advantage over paddlefish, negatively affecting the relative growth of the latter (Schrank et al. 2003, 

Schrank and Guy 2002).

Furthermore, Bighead Carp can host two pathogens that have the potential of affecting and native fish 

species. One of these parasites, the gill-damaging Lernaea cyprinacea, known as anchorworm, was found 

in Channel Catfish being cultured with Bighead Carp (Goodwin 1999). This parasite is also known to 

affect salmonids and eels. Anchorworm occurs worldwide, is known from 40 cyprinid species, and 

completes its life history on a single host (Hoole et al. 2001). Bighead Carp is also known to be host of 

Bothriocephalus acheilognathi, known as the Asian Carp tapeworm. This cestode parasite, introduced 

into United States waters from grass carp, erodes mucus membranes and intestinal tissues, often leading 

to death of the host (Humpback Chub Ad Hoc Advisory Committee 2003). Yet, these adverse effects are 

minimal on Bighead Carp (Kolar et al. 2005). The Asian Carp tapeworm is known to have infected native 

fishes of concern in five states: Arizona, Colorado, Nevada, New Mexico, and Utah. As the introduced 

range of Bighead and Silver carps grows in United States waters, a number of native fishes, particularly, 

but not limited to, cyprinids, percids, and centrarchids, will probably become hosts of the Asian carp 

tapeworm (Kolar et al. 2005).

Hypophthalmichthys nobilis has a high potential socio-economic impact in the Great Lakes.
307

The spread of this species adversely affects commercial fishery in parts of the Mississippi River Basin 

(Maher 2005). Bighead Carp has become a substantial portion of commercial catch, significantly 

outnumbering the catch of native species sought after commercially in several waters of the Midwest 

(Conover et al. 2007, Kolar et al. 2005). Commercial fishers on the Illinois River reported a 124% 

increase in the harvest of Bighead and Silver Carps (reported together) and a 35% decrease in buffalo 

harvest during 2002. In the lower Missouri River, between 2002 and 2004, more than twice as many 

Hypophthalmichthys spp. were caught than all other commercial species combined. Furthermore, the 

average weight of individual Hypophthalmichthys spp. was estimated to be at least double that of the 

individual commercial species caught (Kolar et al. 2005). Unless economically viable markets develop, 

the establishment of large self-sustaining populations of Bighead Carp in the United States may 

compromise commercial fishing.

The diet of this species overlaps with that of planktivorous species (fish and invertebrates) and to some 

extent with that of the young of virtually all native fishes. If food resources become limiting, Bighead 

Carps may compete directly with these native species. The decline of native species that are important as 

sport and food species are bound to have a negative economic impact on recreational angling and other 

industries that benefit from sport fishing, such as tourism (Kolar et al. 2005).

Hypophthalmichthys nobilis has the potential for high beneficial effects if introduced to the Great 

Lakes.

Bighead Carp is a popular food fish in its native China and several other countries, ranking fourth in 1999 

in world aquaculture production (FAO 1999). Although not so popular in North America, commercial 

fisheries for bighead carp exist on the Mississippi, Missouri, and Illinois rivers and are sold from small 

specialty food markets to consumers of various Asian cultures in major North American cities (Conover 

et al. 2007, Kolar et al. 2005, Stone et al. 2000). Nonetheless, the market for live Bighead Carp in the 

United States is limited (the typical consumer will buy only enough fish for the current day’s meal) and 

easily saturated. After Bighead Carp fry are produced by hatcheries and grown to market size by fish 

farmers, they are transported to live markets in Toronto, Chicago, New York, Boston, Montreal, and other 

cities (Conover et al. 2007).

Bighead Carp are frequently used in polyculture with other fish, such as Common Carp, various tilapias, 

Largemouth Bass, and Bigmouth Buffalo (Jennings 1988) to control zooplankton and phytoplankton 

populations. In the United States, Bighead Carp are cultured in ponds with channel catfish and sometimes 

with Grass Carp to control macrophytes (Conover et al. 2007).

Additionally, Bighead Carp can be an important source of revenue for catfish farmers during times of low 

catfish prices (Stone et al. 2000). Engle and Brown (1998) estimated that the net benefit of stocking 

Bighead Carp with catfish was substantially higher. Net benefits ranged from $1,628 to $2,743 annually 

from a 6-ha (15-acre) pond. Furthermore, there is evidence of Bighead Carp used as sport fish in 

Oklahoma. Relatively numerous sport fishing catches have been recorded downstream from a low-water 

dam in the Neosho River at Miami, Oklahoma (Jester et al. 1992).

The role of bighead carp as a biological control agent for plankton control and removal is largely 

debated. While Henderson (1978, 1983) suggested that both Bighead and Silver Carps would stimulate 

phytoplankton blooms that would result in removal of nutrients by phytoplankton, Opuszynski (1980) 

found that organic carbon, nitrogen, and total phosphorous increased in bottom sediments, despite the 

decrease in nitrogen, phosphorous, and dissolved. When those bottom sediments were disturbed by 

activities of other fishes, phytoplankton populations increased. Furthermore, Lieberman (1996) stocked 

Bighead and Silver Carps and found that total phosphorus and total inorganic nitrogen increased as a 
308

result. Yet, some studies have reported that Bighead Carp is able to improve water quality by continually 

removing plankton, especially blue-green algae. This stabilizes plankton and lessens the probability of 

die-offs in production ponds (Kolar et al. 2007, Schofield et al. 2005).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and 

ecosystems)

1 

Not significantly 0

Unknown U

 Bighead Carp is host to two pathogens that have the potential of affecting and native fish species. One of these 

parasites, the gill-damaging Lernaea cyprinacea, known as anchorworm, was found in channel catfish being 

cultured with Bighead Carp (Goodwin 1999). This parasite is also known to affect salmonids and eels. 

Anchorworm occurs worldwide, is known from 40 cyprinid species, and completes its life history on a single 

host (Hoole et al. 2001). Bighead Carp is also known to be host of Bothriocephalus acheilognathi, known as the 

Asian Carp Tapeworm. This cestode parasite, introduced into United States waters from Grass Carp, erodes 

mucus membranes and intestinal tissues, often leading to death of the host (Hoole et al. 2001, Humpback Chub 

Ad Hoc Advisory Committee 2003). Yet, these adverse effects are minimal on Bighead Carp (Kolar et al. 2005). 

The Asian Carp Tapeworm is known to have infected native fishes of concern in five states: Arizona, Colorado, 

Nevada, New Mexico, and Utah (Kolar et al. 2005). As the introduced range of Bighead and Silver Carps grows

in United States waters, a number of native fishes, particularly, but not limited to, cyprinids, percids, and 

centrarchids, will probably become hosts of the Asian Carp Tapeworm (Kolar et al. 2005).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted 

threatened/endangered species or caused critical reduction, extinction, behavioral changes 

including modified spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Bighead Carp is a powerful filter-feeder with a wide food spectrum that grows fast and reproduces quickly (Xie 

and Chen 2001), which makes this species a strong competitor. Within its native China, Bighead Carp are 

considered invasive and are associated with declines in native planktivorous fishes when translocated outside 

their natural range (Li and Xie 2002). Xie and Chen (2001) found that stocking of Bighead Carp into the 

plateau lakes of China had disastrous effects on endemic fishes, especially filter-feeding, endemic Barbless 
309

Carp (Cyprinus pellegrini). The catch of BarblessCcarp, that once represented 50% of yield of total fishes 

caught, declined to 20% in the 1960s, to 10% in the early 1970s, and plummeted to <1% in the 1980s.

 Bighead Carp also pose a threat to the ecology of the Mississippi River basin and connecting aquatic 

ecosystems. These fish are capable of significantly reducing zooplankton abundance, which adversely affects all 

fish in their early life stages when their diets are strictly planktonic (Chick and Pegg 2001, Xie and Chen 2001). 

Furthermore, Bighead Carp compete with fish that are filter-feeders as adults, such as paddlefish. Several 

studies have showed that when zooplankton is limited, Bighead Carp has a competitive advantage over 

Paddlefish, negatively affecting the relative growth of the latter (Chick and Pegg 2001, Schrank et al. 2003, 

Schrank and Guy 2002).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 Bighead Carp have considerable effects on zooplankton communities. This fish are known to decrease the size 

of zooplankton within a species (Kim et al. 2003, Radke and Kahl 2002), possibly removing a species from the 

size category that will be consumed effectively by Paddlefish. It seems likely that Hypophthalmichthys have the 

potential to alter the food web in ways that could negatively affect fishes such as Paddlefish that feed on large 

crustacean zooplankton (Kolar et al. 2005).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 1 
310

effects have been limited or inconsistent (as compared with above statement)

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 8

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6
311

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U

 The spread of this species adversely affects commercial fishery in parts of the Mississippi River basin (Maher 

2005). Bighead Carp has become a substantial portion of commercial catch, significantly outnumbering the 

catch of native species sought after commercially in several waters of the Midwest (Conover et al. 2007, Kolar 

et al. 2005). Commercial fishers on the Illinois River reported a 124% increase in the harvest of Bighead and 

Silver Carps (reported together) and a 35% decrease in Buffalo harvest during 2002 (Conover et al. 2007). In 

the lower Missouri River, between 2002 and 2004, more than twice as many Hypophthalmichthys were caught 

than all other commercial species combined. Furthermore, the average weight of individual 

Hypophthalmichthys was estimated to be at least double that of the individual commercial species caught 

(Kolar et al. 2005). Unless economically viable markets develop, the establishment of large self-sustaining 

populations of Bighead Carp in the United States may compromise commercial fishing (Conover et al. 2007).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0
312

Unknown U

 The diet of this species overlaps with that of planktivorous species (fish and invertebrates) and to some extent 

with that of the young of virtually all native fishes. If food resources become limiting, Bighead Carps may 

compete directly with these native species. The decline of native species that are important as sport and food 

species are bound to have a negative economic impact on recreational angling and other industries that benefit 

from sport fishing, such as tourism (Kolar et al. 2005).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 12

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √

Not significantly 0 
313

Unknown U

 The role of Bighead Carp as a biological control agent for plankton control and removal is largely debated. 

While Henderson (1978, 1983) suggested that both Bighead and Silver carps would stimulate phytoplankton 

blooms that would result in removal of nutrients by phytoplankton, Opuszynski (1980) found that organic 

carbon, nitrogen, and total phosphorous increased in bottom sediments, despite the decrease in nitrogen, 

phosphorous, and dissolved. When those bottom sediments were disturbed by activities of other fishes, 

phytoplankton populations increased. Furthermore, Lieberman (1996) stocked Bighead and Silver carps and 

found that total phosphorus and total inorganic nitrogen increased as a result.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Bighead Carp is a popular food fish in its native China and several other countries, ranking fourth in 1999 in 

world aquaculture production (FAO 1999). Although not so popular, North American commercial fisheries for 

Bighead Carp exist on the Mississippi, Missouri, and Illinois rivers and are sold from small specialty food 

markets to consumers of various Asian cultures in major North American cities (Conover et al. 2007, Kolar et 

al. 2005, Stone et al. 2000). Nonetheless, the market for live Bighead Carp in the United States is limited (the 

typical consumer will buy only enough fish for the current day’s meal) and easily saturated (Stone et al. 2000). 

After Bighead Carp fry are produced by hatcheries and grown to market size by fish farmers, they are 

transported to live markets in Toronto, Chicago, New York, Boston, Montreal, and other cities (Conover et al. 

2007).

 Furthermore, Bighead Carp are frequently used in polyculture with other fish, such as Common Carp, various 

tilapias, Largemouth Bass, and Bigmouth Buffalo (Jennings 1988) to control zooplankton and phytoplankton 

populations. In the United States, Bighead Carp are cultured in ponds with Channel Catfish and sometimes with 

Grass Carp to control macrophytes (Conover et al. 2007).

 Additionally, bighead carp can be an important source of revenue for catfish farmers during times of low 

catfish prices (Stone et al. 2000). Engle and Brown (1998) estimated that the net benefit of stocking Bighead 

Carp with catfish was substantially higher. Net benefits ranged from $1,628 to $2,743 annually from a 6-ha 

(15-acre) pond.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is evidence of Bighead Carp used as sport fish in Oklahoma. Relatively numerous sport fishing catches 

have been recorded downstream from a low-water dam in the Neosho River at Miami, Oklahoma (Jester et al. 

1992).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?
314

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 

Unknown U √

 The effects of Bighead Carp on water quality in culture ponds is highly debated due to conflicting results from 

various studies (Kolar et al. 2007, Stickney 1996). Yet, some studies have reported that Bighead Carp is able to 

improve water quality by continually removing plankton, especially blue-green algae. This stabilizes plankton 

and lessens the probability of die-offs in production ponds (Kolar et al. 2007, Schofield et al. 2005).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
315

0 ≥2

Unknown

1 ≥1
316

Scientific Name: Ictalurus furcatus

Valenciennes in Cuvier and Valenciennes, 1840

Common Name: Blue Catfish, White Cat, White Fulton, Fulton, Humpback Blue,

Forktail Cat, Blue Channel Catfish

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Low

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: High

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Ictalurus furcatus has a High probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Escape from recreational culture, dispersal, unauthorized 

intentional release

Blue Catfish can migrate up to several hundred kilometers.The closest population to the Great Lakes 

basin is likely a stocked population documented in 1981 in Indian Lake, Ohio (Logan County), less than 

20 km from the Lake Erie watershed (USGS 2012). However, this water body drains into the Ohio River 

and then into the Mississippi River, with no direct connection to the Great Lakes. Likewise, the sites of 

Minnesotan introductions (Lake St. Croix and Lake Peppin) also drain into the Mississippi River (USGS 

2012). Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial 

unconnected pond near the St. Joseph River (http://catfishacresphotos.webs.com/). 

As a result of I. furcatus growing to exceptionally large sizes, it has been widely introduced as a food and 

sport fish and now occurs in 29 states throughout the Mississippi basin as well as the Atlantic, Pacific, 

and Gulf coastal slopes (Graham et al. 1999, Fuller and Neilson 2015b). Blue Catfish are often found in 

fish markets (Graham et al. 1999).

Other reasons for nonindigenous occurrences include intentional stocking or unintentional flooding of 

private waterbodies (Bonvechio et al. 2012, Guier et al. 1984, Mettee et al. 1996).

POTENTIAL INTRODUCTION VIA DISPERSAL
317

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Ictalurus furcatus is endemic to the Mississippi, Missouri, and Ohio River basins of the central and southern 

United States and inhabits Gulf Coast streams from Alabama south into Mexico, but it has been recently 

introduced to many northern states (Graham et al. 1999, Padhi 2011).

 Ictalurus furcatus has been introduced to Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, 

Maryland, Georgia, New Jersey, New Mexico, Minnesota, North Carolina, Ohio, Oklahoma Oregon, South 

Carolina, Virginia and Washington (Tuckey and Fabrizio 2011).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25 

√

Unknown U

 Ictalurus furcatus is endemic to the Mississippi, Missouri, and Ohio River basins of the central and southern 

United States and inhabits Gulf Coast streams from Alabama south into Mexico, but it has been recently 

introduced to many northern states (Graham et al. 1999, Padhi 2011).

 Ictalurus furcatus has been introduced to Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, 

Maryland, Georgia, New Jersey, New Mexico, Minnesota, North Carolina, Ohio, Oklahoma Oregon, South 

Carolina, Virginia and Washington (Tuckey and Fabrizio 2011).

 The closest population to the Great Lakes basin is likely a stocked population documented in 1981 in Indian 

Lake, OH (Logan County), less than 20 km from the Lake Erie watershed (USGS 2012); however, this water 

body drains into the Ohio River and then into the Mississippi River, with no direct connection to the Great 

Lakes. Likewise, the sites of Minnesotan introductions (Lake St. Croix and Lake Peppin) also drain into the 

Mississippi River (USGS 2012).

 Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial unconnected pond 

near the St. Joseph River (http://catfishacresphotos.webs.com/).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 100
318

other organisms entering the Great Lakes basin.

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 As a result of I. furcatus growing to exceptionally large sizes, it has been widely introduced as a food and sport 

fish and now occurs in 29 states throughout the Mississippi basin as well as the Atlantic, Pacific, and Gulf 

coastal slopes (Graham et al. 1999, Fuller and Neilson 2015b). 

 Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial unconnected pond 

near the St. Joseph River (http://catfishacresphotos.webs.com/).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial unconnected pond 

near the St. Joseph River (http://catfishacresphotos.webs.com/).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?
319

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Other reasons for nonindigenous occurrences of Blue Catfish include intentional stocking or unintentional 

flooding of private waterbodies (Bonvechio et al. 2012, Guier et al. 1984, Mettee et al. 1996).

 Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial unconnected pond 

near the St. Joseph River (http://catfishacresphotos.webs.com/).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1 √

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 Blue Catfish is stocked for catch and keep at Litchfield Catfish Acres, Michigan, an artificial unconnected pond 

near the St. Joseph River (http://catfishacresphotos.webs.com/).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25
320

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.25 25 Low

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Low
321

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Ictalurus furcatus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Ictalurus furcatus are found in many regions with continental climate similar to the Great Lakes. For 

example, found in Missouri River near Bismarck, North Dakota (Fuller and Neilson 2015b), which is at a 

latitude of 46°N. This region experiences harsh winters and hot summers- similar to the Great Lakes. 

Literature shows no mention of pollution, but this species inhabits the lower Mississippi and the 

Chesapeake Bay watershed, both of which include polluted conditions. Areas where Ictalurus furcatus are 

found have similar temperatures and salinities to the Great Lakes. I. furcatus inhabits large rivers and 

major tributaries associated with swift chutes and flowing waters around deep pools, as well as oxbow 

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.1 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 1 100 High

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Low

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Low

Total Unknowns (U) 0 Confidence Level High
322

lakes and reservoirs (Bonvechio et al. 2012, Boschung and Mayden 2004, Jenkins and Burkhead 1994, 

Ross 2001).

This species is a dietary generalist that would likely find adequate food in the Great Lakes. Males guard 

eggs and fry (Graham et al. 1999) giving this species an advantage over other native fish that do not guard 

young.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 I. furcatus spawns in late spring to early summer at water temperatures of 21–25°C (Sublette et al. 1990) and 

have a faster growth rate during summer (at 20–28°C) (Grant and Robinette 1992, Padhi 2011).

 I. furcatus is migratory; it moves toward warmer waters during winter and to cooler waters during summer 

(Graham et al.1999).

 I. furcatus can tolerate salinities up to 15 ppt (Christmas and Waller 1973, Dennison et al. 1993, Hio et al. 

2012, Perry 1968, Ross 2001).

 I. furcatus has 87% survival in "low DO" treatment (experiment 2) with DO of 1.41 ppm (Torrans et al. 2012).

 In fish farms in Mississippi Delta, I. furcatus had 95% survival after winter with low temperature of 5.1°C 

(Bosworth 2012).

 I. furcatus is found in Missouri River near Bismarck, ND (Fuller and Neilson 2015b), which is at a latitude of 

46°N. While water temperatures are not available for this location, the harsh winters in this region make it 

likely I. furcatus can survive low temperatures.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6
323

 In fish farms in the Mississippi Delta, I. furcatus had 95% survival after winter with low temperature of 5.1°C 

(Bosworth 2012).

 I. furcatus is found in Missouri River near Bismarck, ND (Fuller and Neilson 2015b), which is at a latitude of 

46°N. While water temperatures are not available for this location, the harsh winters in this region make it 

likely I. furcatus can survive low temperatures.

 I. furcatus is migratory; it moves toward warmer waters during winter (Graham et al. 1999).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

5

Blue Catfish are highly omnivorous, utilizing more than 30 types of prey. A study done by Eggleton and Schramm 

(2004) found that collectively across all habitats, Blue Catfish diets were composed of 47% fishes (more than 15 

identifiable species), 15% molluscs, 12% chironomids and oligochaetes, 7% detritus/plant matter, 6% decapods, 6% 

scavenging, 1% terrestrial arthropods. Scavenged items were typically fishes and fish scales, but also included 

small mammals, birds, and turtles (Eggleton and Schramm 2004).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 I. furcatus is a large fish, reaching 40-50 kg (Graham et al. 1999).

 In studies of the James and Rappahannock rivers I. furcatus is estimated to make up 75% of the total fish 

biomass; associated with decline in native white catfish I. catus (Schloesser et al. 2011, Tuckey and Fabrizio 

2011).

 Commercial landings in the Maryland and Virginia have increased from 9.5-17 metric tons in 2003-2005 to 

more than 72.5 metric tons in 2008 (Schloesser et al. 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?
324

Very high 9

High 6

Moderate 3

Low 0

Unknown U

0

 I. furcatus has a relative fecundity from 900 to 1,350 eggs/kg of body weight (Graham et al. 1999).

 Relative fecundity (eggs per kg body weight) of other siluroid species is as follows (Legendre et al. 1996): 

o Silurus glunis: 10,000-25,000

o Guleichthys feliceps: 50,000

o lctalurus punctutus: 8,000

o Chtysichthys nigrodigitaius: 15,000-18,000

o Hoplosternum littorale: 45,000-75,000

o Clarias gariepinus: 60,000-150,000

o Clarias macrocephalus: 20,000-50,000

o Heterobranchus longifilis: 30,000-120,000

o Pseudoplatystoma coruscans: 120,000-130,000

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 I. furcatus males of guard the eggs and fry (Graham et al. 1999).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6
325

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 I. furcatus is found in many regions with continental climate similar to the Great Lakes. For example, they are

found in Missouri River near Bismarck, ND (Fuller and Neilson 2015b), which is at a latitude of 46°N. This 

region experiences harsh winters and hot summers.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 This species inhabits the lower Mississippi and the Chesapeake Bay watershed, both of which include polluted 

conditions.

 This species inhabits water with a range of currents, from swift chutes to oxbow lakes and floodplain lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

4

 I. furcatus inhabits large rivers and major tributaries associated with swift chutes and flowing waters around 

deep pools, as well as oxbow lakes and reservoirs (Bonvechio et al. 2012, Boschung and Mayden 2004, Jenkins 

and Burkhead 1994, Ross 2001).

 I. furcatus inhabits river channels: higher flows and harder substrates (i.e., gravel, boulders, rock rip rap); and 

floodplain lakes - lower or no flows and softer substrates (i.e., silt, sand) (Eggleton and Schramm 2004).

 Blue Catfish prefer open waters of large reservoirs and main channels, backwaters, and embayments of large, 

flowing rivers where water is normally turbid and substrate varies from gravel-sand to silt-mud (Burr and 

Warren 1986). Many rivers and reservoirs with Blue Catfish populations have only mud or silt substrate. Blue 

Catfish prefer deep, swift channels and flowing pools (Jenkins and Burkhead 1994), and large specimens were 
326

often found in tailwaters below dams where currents were swift and substrates consist of sand, gravel, and rock 

(Mettee et al. 1996, Graham et al. 1999). 

 Blue Catfish seek protected areas behind rocks, root-wads, depressions, undercut stream banks, or other areas 

where the currents are minimal to deposit eggs (Graham et al. 1999).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 I. furcatus has a faster growth rate during summer (at 20–28°C) (Grant and Robinette 1992, Padhi 2011).

 This species tolerates moderate salinity.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 I. furcaturs on floodplain lakes consumed mainly clupeid fishes, chironomids, oligochaetes, and detritus/plant 

matter (Eggleton and Schramm 2004).

 Blue Catfish are highly omnivorous, utilizing more than 30 types of prey. A study done by Eggleton and 

Schramm (2004) found that collectively across all habitats, Blue Catfish diets were composed of 47% fishes 

(more than 15 identifiable species), 15% molluscs, 12% chironomids and oligochaetes, 7% detritus/plant 

matter, 6% decapods, 6% scavenging, 1% terrestrial arthropods. Scavenged items were typically fishes and fish 

scales, but also included small mammals, birds, and turtles (Eggleton and Schramm 2004).
327

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
328

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 This species guards fry, and grows to a large size.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 As the primary vector would be unauthorized introductions or recreational escape, the inocula size would 

depend on human activity in these areas. This is not well-quantified and given the few search results for online 

suppliers, likely small.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
329

Unknown U

4

 I. furcatus is endemic to the Mississippi, Missouri and Ohio River basins of the central and southern United 

States and occupies Gulf Coast streams from Alabama, south into Mexico, but has been recently introduced to 

many northern states (Graham et al. 1999, Padhi 2011).

 I. furcatus has been introduced to Alabama, Arizona, Arkansas, California, Colorado, Florida, Idaho, 

Maryland, Georgia, New Jersey, New Mexico, Minnesota, North Carolina, Ohio, Oklahoma Oregon, South 

Carolina, Virginia and Washington (Tuckey and Fabrizio 2011).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 I. furcatus is migratory; they can travel several hundred km (Graham et al. 1999).

 I. furcatus has spread rapidly though the Chesapeake Bay watershed (Schloesser et al. 2011).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for A. Total Points (pre-adjustment) 86
330

Establishment

>100 High Adjustments

B. Critical species A*(1- 0%) 86

51-99 Moderate C. Natural enemy B*(1- 0%) 86

Control measures C*(1- 0%) 86

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: High

Ictalurus furcatus has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Ictalurus furcatus may introduce high levels of PCBs and other contaminants into avian predators 

(Schloesser et al. 2011). Homer and Jennings (2011) found shifts in the gillnet catch of Ameiurus 

catus (L.) (White Catfish) to Blue Catfish in Lake Oconee, GA, and suggested that competition by 

introduced Blue Catfish and Flathead Catfish could drive declines in the abundance of native White 

Catfish (Bonvechio et al. 2012). In studies of the James and Rappahannock rivers they are estimated to 

make up 75% of the total fish biomass; associated with decline in native White Catfish I. 

catus (Schloesser et al. 2011, Tuckey and Fabrizio 2011). In the Chesapeake watershed, Ictalurus 

furcatus may prey on economically and ecologically important estuarine fishes such as juvenile American 

Shad, Atlantic Menhaden, and River Herring (Schloesser et al. 2011). Ictalurus furcatus hybridizes with 

threatened Yaqui Catfish I. pricei in Mexico (USFWS 1994, Fuller and Neilson 2015b).

There is little or no evidence to support that Ictalurus furcatus has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

Ictalurus furcatus accumulate mercury in tissue (Nichols et al. 2002); this leads to many consumption 

advisories for this species where they are found. There is no evidence that this species negatively impacts 
331

infrastructure, economic sectors, recreational activities and associated tourism, or the aesthetic appeal of 

the areas it inhabits.

Ictalurus furcatus has the potential for high beneficial impact if introduced to the Great Lakes.

California stocks Blue Catfish for Asiatic Clam control (Graham et al. 1999) but is not very 

effective. Ictalurus furcatus are sport and commercial fisheries in 14 states, most of which are in eastcentral and southeastern states within the middle and lower Mississippi River and Ohio River basins 

(Graham et al. 1999, Holley et al. 2009, Michaletz and Dillard 1999). They are unpopular with the 

aquaculture industry because of reported slow maturation rates, poor food conversion, and poor spawning 

success in captivity (Graham et al. 1999). About one-half of the states where Blue Catfish occur (15) 

consider the species recreationally important (Graham et al. 1999, Michaletz and Dillard 1999, Schloesser 

et al. 2011).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and 

ecosystems)

1 

Not significantly 0

Unknown U √

 I. furcatus may introduce high levels of PCBs and other contaminants into avian predators (Schloesser et al. 

2011).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Homer and Jennings (2011) found shifts in the gillnet catch of Ameiurus catus (L.) (White Catfish) to Blue 

Catfish in Lake Oconee, GA, and suggested that competition by introduced Blue Catfish and Flathead Catfish 

could drive declines in the abundance of native White Catfish (Bonvechio et al. 2012).

 In studies of the James and Rappahannock rivers they are estimated to make up 75% of the total fish biomass; 

associated with decline in native White Catfish I. catus (Schloesser et al. 2011, Tuckey and Fabrizio 2011).
332

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 In the Chesapeake watershed, Blue Catfish may prey on economically and ecologically important estuarine 

fishes such as juvenile American Shad, Atlantic Menhaden and River Herring (Schloesser et al. 2011).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 √

Not significantly 0 

Unknown U

 I. furcatus hybridizes with threatened Yaqui Catfish I. pricei in Mexico (Fuller and Neilson 2015b, USFWS 

1994).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

6
333

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √

Not significantly 0 

Unknown U

 I. furcatus cccumulates mercury in it’s tissues (Nichols et al. 2002).

 There are many consumption advisories for this species in place.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1
334

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0
335

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √

Not significantly 0 

Unknown U

 California stocks Blue Catfish for Asiatic clam control (Graham et al. 1999).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 I. furcatus is in sport and commercial fisheries in 14 states, most of which are in east-central and southeastern 

states within the middle and lower Mississippi River and Ohio River basins (Graham et al. 1999, Holley et al. 

2009, Michaletz and Dillard 1999).

 This species is unpopular with the aquaculture industry because of reported slow maturation rates, poor food 

conversion, and poor spawning success in captivity (Graham et al. 1999).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6 √

It is sometimes employed recreationally, but adds little value to local communities or 1 
336

tourism 

Not significantly 0

Unknown U

 About one-half of the states where Blue Catfish occur (15) consider the species recreationally important 

(Graham et al. 1999, Michaletz and Dillard 1999, Schloesser et al. 2011).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to 

be studied

1 √

Not significantly 0 

Unknown U

 I. furcatus is used in toxicity analyses, e.g., used as bioindicator of malathion exposure (Aker et al. 2008).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 14

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High
337

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
338

Scientific Name: Knipowitschia caucasica 

Berg 1916

Common Name: Caucasian Dwarf Goby

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Knipowitschia caucasica has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Knipowitschia caucasica does not occur near waters connected to the Great Lakes basin. This species is 

not known to hitchhike or foul. Knipowitschia caucasica is not stocked, commercially cultured, or sold in 

the Great Lakes region. It occurs in the Mediterranean Sea, which has shipping traffic that goes directly to 

the Great Lakes; however, there is insufficient information to determine if this species occurs in the 

Mediterranean ports that are in direct trade with the Great Lakes. Due to its euryhaline nature, 

Knipowitschia caucasica may be able to survive ballast water management practices. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U 

 There have been no reports of K. caucasica near or in waters connected to the Great Lakes; however, the 

species has been accidently introduced to other European bodies of water from its original source in the PontoCaspian region. K. caucasica has been identified in several bodies of water in Greece (Economidis and Miller 
339

1990, Kevrekidis et al. 1990, Daoulas et al. 1993, Kovačić and Pallaoro 2003, Leonardos et al. 2008), Hungary 

(Halasi-Kovács et al. 2011), and Turkey (Van Neer et al. 1999).

 Knipowitschia caucasica has only been identified in European waters (Economidis and Miller 1990, Kevrekidis 

et al. 1990, Daoulas et al. 1993, Van Neer et al. 1999, Kovačić and Pallaoro 2003, Leonardos et al. 2008, 

Halasi-Kovács et al. 2011).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Invasion of K. caucasica into Turkish lakes was attributed to involuntary introduction by man through fish 

stocking or recreational fishing (Van Neer et al. 1999).

 Knipowitschia caucasica larvae were found in aquatic vegetation hauls in Greek lakes (Daoulas et al. 1993).

 Eggs are usually found attached to the underside of small gravel, mollusk shells, or reeds (Baimov 1963).

 In Europe, K. caucasica have been found in fish stocks of common carp (Van Neer et al. 1999).

 However, K. caucasica has only been identified in European waters (Economidis and Miller 1990, Kevrekidis et 

al. 1990, Daoulas et al. 1993, Van Neer et al. 1999, Kovačić and Pallaoro 2003, Leonardos et al. 2008, 

Halasi-Kovács et al. 2011).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
340

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Performing an online search of aquaria, catalogs, and biological supply companies (including Carolina 

Biological, Aquatic Biosystems, and Fisher-Scientific) did not yield any listings or information for K. caucasica

or the common name (caucasian dwarf goby)

 Knipowitschia caucasica is listed on the IUCN Redlist of Threatened Species, although as a low concern species 

with no known major threats (Freyhof and Kottelat 2008c). With this in mind, it may be difficult to acquire 

these species for market sales.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 An online search did not yield any listings or information for K. caucasica or the common name (caucasian 

dwarf goby)

 Knipowitschia caucasica is listed on the IUCN Redlist of Threatened Species, although as a low concern species 

with no known major threats (Freyhof and Kottelat 2008c). With this in mind, it may be difficult to acquire 

these species for market sales.

 Moreover, K. caucasica has only been identified in European waters (Economidis and Miller 1990, Kevrekidis 

et al. 1990, Daoulas et al. 1993, Van Neer et al. 1999, Kovačić and Pallaoro 2003, Leonardos et al. 2008, 

Halasi-Kovács et al. 2011).

4b) What is the nature and proximity of this activity to the Great Lakes basin?
341

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Although K. caucasica is not transported or sold commercially in the Great Lakes region according to an online 

search, there is potential for the species to accidentally enter the basin illegally or through ballast water. Van 

Neer et al. (1999) and Daoulas et al. (1993) argue that K. caucasica has been accidently introduced into some 

European waters by stocks of other fish or recreational fishing.

 However, K. caucasica has only been identified in European waters (Economidis and Miller 1990, Kevrekidis et 

al. 1990, Daoulas et al. 1993, Van Neer et al. 1999, Kovačić and Pallaoro 2003, Leonardos et al. 2008, HalasiKovács et al. 2011).

 Furthermore, K. caucasica is listed on the IUCN Redlist of Threatened Species, although as a low concern 

species with no known major threats (Freyhof and Kottelat 2008c). With this in mind, it may be difficult to 

acquire this species for market sales.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING
342

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Due to its small size (30-40mm) (Kevrekidis et al. 1990), K. caucasica can be easily taken up by ballast water 

systems.

 Knipowitschia caucasica has been found in other fish stocks, which has contributed to their introduction in 

Turkish and Greek water bodies (Van Neer et al. 1999). In addition, they have shown the ability to develop 

freshwater populations in European riverine and lake systems (Halasi-Kovács et al. 2011).

 Knipowitschia caucasica has wide ecological tolerances. They are a euryhaline species and can survive in both 

hypersaline and fresh water, allowing them to easy survive introduction to the Great Lakes from a saline source 

(Kevrekidis et al. 1990). 

 Since it feeds primarily on benthic amphipods and polychaetes, K. caucasica prefers to inhabit sandy, muddy or 

gravel substrata (Kevrekidis et al. 1990, Daoulas et al. 1993)which may facilitate its survival during ballast 

water flushing.

 However, the species may have difficulty surviving adverse environments for long periods of time in ballast 

tanks. Typical environments they have been found in have a dissolved oxygen (DO) range of 5.3-8.4ppm and pH 

range of 7.3-8.3 (Kevrekidis et al. 1990). Low DO levels or acidic/basic conditions in ballast tanks may have 

adverse effects on their survival. Also, they can survive temperatures of 3.4°C up to 27°C, but temperatures 

above 15°C are ideal (Baimov 1963, Kevrekidis et al. 1990).

 Knipowitschia caucasica is found in the freshwater Lake Trichonis of Greece, and the Evros delta that has 24-

36‰ salinity (Daoulas et al. 1993, Kevrekidis et al. 1993). This species occurs in waters with temperatures of 

1.6-26.9°C and oxygen levels of 5.3-8.96 ppm (Kevrekidis et al. 1993, Gülle et al. 2008).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Knipowitschia caucasica originates from the Ponto-Caspian region and has been confirmed in Aegean waters 

(Economidis and Miller 1990). Also, it has been identified in the Caspian, Azov, Aral, Black (Daoulas et al. 

1993), and Adriatic (Kovačić and Pallaoro 2003) seas, as well as several localities in northern Greece and 

Turkey. Since ships coming from these locations have brought other invasive species (i.e. dreissenid mussels 
343

from Ponto-Caspian region), we know that ships have the potential to bring K. caucasica from these areas. 

However, documentation of K. caucasica in ballast water from these areas was not found. 

 It occurs in the Mediterranean Sea (Kevrekidis et al. 1990), which has shipping traffic that goes directly to the 

Great Lakes; however, there is insufficient information to determine if this species occurs in the Mediterranean 

ports that are in direct trade with the Great Lakes.

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
344

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Knipowitschia caucasica has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate). 

The native and introduced ranges of Knipowitschia caucasica have similar climatic and abiotic conditions 

as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species inhabits 

shallow waters that have varied bottom structures (Kovačić and Pallaoro 2003), which are available in the 

Great Lakes region. Knipowitschia caucasica can tolerate a wide range of abiotic conditions. It resides in 

hypersaline and fresh waters (Kevrekidis et al. 1990), so it may survive the transition in salinity between 

ballast water and Great Lakes fresh water. It occurs in the eutrophic Lake Eğirdir (Gülle et al. 2008) as 

well as Lake Trichonis, a mesotrophic lake (Daoulas et al. 1993). It tolerates water temperatures of 1.6-

26.9°C and oxygen levels of 5.3-8.96 ppm (Kevrekidis et al. 1990, Gülle et al. 2008); thus it is somewhat 

likely that this species can overwinter in the Great Lakes but its capacity to do so is limited by the amount 

of dissolved oxygen in the water. In its current range, Knipowitschia caucasica migrates into deeper 

waters over the winter (Baimov 1963) where temperatures may be slightly higher, but dissolved oxygen is 

lower. Knipowitschia caucasica prefers mesohaline to hypersaline waters; thus, increased salinization due 

to climate change would make the Great Lakes a better environment for the establishment of this species. 

Knipowitschia caucasica has a broad and flexible diet, and feeds primarily on benthic amphipods, 

polychaetes, chironomid larvae, copepods, and cladocerans (Kevrekidis et al. 1990). These fish are also 

known to feed on Dreissenid polymorpha larvae (Daoulas et al. 1993), and may benefit from the presence 

of Dreissenids that are already established in the Great Lakes (Benson et al. 2014). Occasionally it feeds 

on planktonic organisms. It is likely that this species will find an appropriate food source in the Great 

Lakes. Larger fish in the Great Lakes may prey on Knipowitschia caucasica but it is unknown whether 

that would prevent establishment. In the Aral Sea, it is one of the most abundant fish and is not a very 

important component of the diets of piscivorous fish (Baimov 1963). It is unknown if the establishment of 

Knipowitschia caucasica will be prevented by parasitism. Knipowitschia caucasica is a host to parasites 

Aphalloides coelomicola, Cryptocotyle spp., Paratimonia gobii, Timoniella imbutiforme, and Dichelyne 

minutus (Krasnoyd et al. 2012); however, there is currently not enough information to determine if these 

parasites negatively impact the health of Knipowitschia caucasica, or its chances of establishing in the 

Great Lakes. Aphalloides coelomicola reduces the female gonad weight of the common goby 

(Pomatoschistus microps) (Pampouli et al. 1999). There is no evidence that suggest that Aphalloides 

coelomicola, Cryptocotyle spp., or Paratimonia gobii currently occur in the Great Lakes. Timoniella spp. 

has been found in the Great Lakes and reduces the ruffe’s ability to survive in low oxygen waters (Pronin 

et al. 1997). Dichelyne spp. is reported to occur in the St. Lawrence River, but its occurrence and 

infection of native fish is low, and has not infected the nonindigenous round goby (Gendron et al. 2012).

Knipowitschia caucasica reproduces from the end of April to the end of July at water temperatures of 15-

27°C (Kevrekidis et al. 1990). The Great Lakes basin contains a number of areas that have appropriate 

spawning temperatures during those months. Knipowitschia caucasica has a slightly lower fecundity than 

other fish in the Knipowitschia genus. Its lowest reported fecundity is 60 eggs (Kevrekidis et al. 1990) 

and its highest reported fecundity is 1389 eggs (Gheorghiev 1964). K. longecaudata has a fecundity of 

350-2045 eggs (Zelenin and Vladimirov 1975, Ragimov 1986), and K. iljini has a fecundity of 2240 eggs 
345

(Ragimov 1986). In the Caspian Sea, Knipowitschia caucasica had a moderate relative fecundity relative 

to the other Knipowitschia gobies.

Currently, there is no evidence indicating that Knipowitschia caucasica would outcompete other species 

in the Great Lakes if introduced. Its widespread distribution elsewhere has been attributed to its tolerance 

to a wide variety of environmental conditions, its non-specific diet, and early maturation (Kevrekidis et al. 

1990). This species occurs in Lake Eğirdir, Lake Eber, and Demirköprü, and is speculated to have been 

introduced by anthropogenic means due to this fish’s inability for natural introduction via crossing 

hydroelectric dams to migrate up strong currents from the Asku River (Van Neer et al. 1999). No 

specimens of Knipowitschia caucasica were found in these lakes prior to 1992, but were abundant in 

Lake Eğirdir by 1996, and were found in Lake Eber in 1997 and Demirköprü Dam Lake in 1998. There is 

a possibility that Knipowitschia caucasica was unintentionally introduced in these lakes with the stocking 

of common carp fry from Ipsala/Edirne hatcheries, which are located in the same region where this 

species is common. Kolar and Lodge (2002) predict that Knipowitschia caucasica may spread quickly 

after introduction using their models that take into account the fish’s growth rate, lower survival in high

water temperatures, and tolerance of a wide temperature range.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Knipowitschia caucasica has wide ecological tolerances. It is a euryhaline species and can survive in both 

hypersaline and fresh water, allowing it to easy survive introduction to the Great Lakes from a saline source 

(Kevrekidis et al. 1990). 

 This species occurs in waters with temperatures of 1.6-26.9°C (but temperatures above 15°C are ideal) and 

oxygen levels of 5.3-8.96 ppm (Kevrekidis et al. 1993, Gülle et al. 2008).

 The species has been found in Lake Trichonis in Greece, which is known for being mesotrophic (Daoulas et al. 

1993). It occurs in the eutrophic Lake Eğirdir (Gülle et al. 2008).

 This species prefers shallower waters, with spawning typically occurring at 0.15 to 1.5 m (Baimov 1963). 

 However, the species may be limited by low dissolved oxygen and pH conditions. Typical environments they 

have been found in have a dissolved oxygen (DO) range of 5.3-8.4 ppm and pH range of 7.3-8.3 (Kevrekidis et 

al. 1990). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?
346

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 This species occurs in waters with temperatures of 1.6-26.9°C (but temperatures above 15°C are ideal) and 

oxygen levels of 5.3-8.96 ppm (Kevrekidis et al. 1993, Gülle et al. 2008).

 After hatching in the spring, young K. caucasica typically grow rapidly in summer and autumn, and then mature 

after the first winter. They then spawn in warmer temperatures from the end of April through July (Kevrekidis et 

al. 1990).

 The species may have issues with low oxygen levels, as they have been found in environments with a dissolved 

oxygen range of 5.3-8.4ppm (Kevrekidis et al. 1990). Lower ranges have not been documented and this may be 

a limiting factor of this species success in the Great Lakes. However, the gobies have been found in freshwater 

lakes in Greece, Hungary, and Turkey that may have similar colder over-winter temperatures to the Great 

Lakes. For example, K. caucasica has been reported in Lake Trichonis, which is the largest and deepest natural 

freshwater body in Greece (Daoulas et al. 1993).

 It tolerates water temperatures of 1.6-26.9°C and oxygen levels of 5.3-8.96 ppm (Kevrekidis et al. 1990, Gülle 

et al. 2008); thus it is somewhat likely that this species can overwinter in the Great Lakes but its capacity to do 

so is limited by the amount of dissolved oxygen in the water. In its current range, Knipowitschia caucasica

migrates into deeper waters over the winter (Baimov 1963) where temperatures may be slightly higher, but 

dissolved oxygen is lower. It occurs in waters that have ice cover in the winter (Reid and Orlova 2002).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 Stomach contents of K. caucasica revealed that they feed primarily on crustaceans and benthic invertebrates, 

specifically copepods and larval molluscs (dreissenids) (Daoulas et al. 1993).

 It has also been documented that they feed on amphipods and polychaetes (Kevrekidis et al. 1990).

 There is no evidence of this species feasting on planktonic invertebrates or fish.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 6
347

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Currently, there is no evidence indicating that Knipowitschia caucasica would outcompete other species in the 

Great Lakes if introduced. Its widespread distribution elsewhere has been attributed to its tolerance to a wide 

variety of environmental conditions, its non-specific diet, and early maturation (Kevrekidis et al. 1990).

 In the Aral Sea, it is one of the most abundant fish and is not a very important component of the diets of 

piscivorous fish (Baimov 1963).

 However, this goby species has a relatively high rate of reproduction, early sexual maturation (at 20-23 mm), 

and after 8-10 months post hatching they have a high gonadosomatic index (Economidis and Miller 1990). The 

rapid reproduction of this species may allow them to outcompete some slower growing species for resources 

and breeding habitats. 

 Literature does not show evidence of the species outcompeting other goby or fish species in its native region, or 

evidence of it being a poor competitor. Also, in environments where similar goby species are present (i.e. E. 

pygmaeus), the larval forms were observed to share aquatic vegetation habitat, but showed different habitat 

preference later in life (Daoulas et al. 1993).

 Currently, there is no evidence indicating that Knipowitschia caucasica would outcompete other species in the 

Great Lakes if introduced. Its widespread distribution elsewhere has been attributed to its tolerance to a wide 

variety of environmental conditions, its non-specific diet, and early maturation (Kevrekidis et al. 1990).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Knipowitschia caucasica has a relatively high rate of reproduction, early sexual maturation (at 20-23 mm), and 

after 8-10 months post hatching they have a high gonadosomatic index (Economidis and Miller 1990). 

 Two other goby species that are endemic to the same regions as K. caucasica (Economidichthys pygmaeus and 

E. trichonis) spawn earlier between late February through May (Daoulas et al. 1993). K. caucasica breeds 

typically from end of April through July (Kevrekidis et al. 1990).

 Economidichthys pygmaeus has been reported to lay about 500 eggs per nest and E. trichonis about 200-300 

eggs per nest (Daoulas et al. 1993). Reports of K. caucasica nesting report each spawning batch consisting of 

80-100 cylindrical eggs, with only about 50 successfully hatching after 6 days incubation (Economou et al. 

1994).

 Knipowitschia caucasica has a slightly lower fecundity than other fish in the Knipowitschia genus. Its lowest 

reported fecundity is 60 eggs (Kevrekidis et al. 1990) and its highest reported fecundity is 1389 eggs 
348

(Gheorghiev 1964). K. longecaudata has a fecundity of 350-2045 eggs (Zelenin and Vladimirov 1975; Ragimov 

1986), and K. iljini has a fecundity of 2240 eggs (Ragimov 1986). In the Caspian Sea, Knipowitschia caucasica

had a moderate relative fecundity relative to the other Knipowitschia gobies.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 This species has been shown to prefer aquatic vegetative habitats during its larvae stage and has been shown to 

form nests in aquatic reeds (Daoulas et al. 1993), but unlike other related goby species that prefer deeper areas 

covered in weeds, this species prefers shallower sandy, muddy substrata close to shore (Daoulas et al. 1993). 

However, other than habitat preference, evidence of other reproductive strategies was not found. 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species has been reported in the Ponto-Caspian region, particularly in Hungary (Halasi-Kovács et al. 

2011), Turkey (Van Neer et al. 1999), Greece (Economidis and Miller 1990, Kevrekidis et al. 1990, Daoulas et 

al. 1993) and in the Adriatic Sea (Kovačić and Pallaoro 2003). All of these regions are within similar latitudes 

as the Great Lakes region. 

 This species in its native ranges is adjusted to hatching in summer/autumn (July/September) at temperatures 

around 25-28°C and overwintering at temperatures around 3-5°C (Kevrekidis et al. 1990). These are climatic 

conditions and seasonality almost identical to the Great Lakes region. 
349

 Ponto-Caspian region has similar climate and abiotic conditions as Great Lakes (Grigorovich et al. 2003, Reid 

and Orlova 2002, USEPA 2008). 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 This species has been reported in large seas such as Caspian, Azov, Aral and Black Seas, as well as several 

northern localities of Greece and Turkey (Daoulas et al. 1993).

 Knipowitschia caucasica has wide ecological tolerances. It is a euryhaline species and can survive in both 

hypersaline and fresh water, allowing them to easy survive introduction to the Great Lakes from a saline source 

(Kevrekidis et al. 1990). In addition, it has demonstrated the ability to develop freshwater populations in 

European riverine and lake systems (Halasi-Kovács et al. 2011).

 This species in its native ranges is adjusted to hatching in summer/autumn (July/September) at temperatures 

around 25-28°C and overwintering at temperatures around 3-5°C (Kevrekidis et al. 1990). These are water 

conditions similar to the Great Lakes region. 

 No evidence was found on the species chemical tolerances or required nutrient levels.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 This species prefers the shallow waters of mesohaline coastal lakes and lagoons (Kevrekidis et al. 1990); 

however, they have been found in a variety of different salinities, from fresh to sea water (0-24.5 PSU;(Kovačić

and Pallaoro 2003). The Great Lakes has several areas of freshwater coastline that has shallow marshes and 

several shallow inland lakes. 

 Recently, K. caucasica has been found in a medium flow, 2-4 m depth river in Hungary (Halasi-Kovács et al. 

2011). Similar habitats are also available in the Great Lakes basin.

 This species in its native ranges is adjusted to hatching in summer/autumn (July/September) at temperatures 

around 15-27°C (Kevrekidis et al. 1990). These are water conditions similar to the Great Lakes region.

 In order for the species to invade some of the inland lakes in Turkey and Greece, Van Neer et al. (1999) argues 

that the gobies cannot overcome strong currents of rivers and connection canals, therefore, they must have been 
350

introduced by human activities. The strong currents and deep waters of the Great Lakes may pose a challenge 

for this species to invade some of the shallower waters of the Great Lakes region.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover,

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 This species prefers the shallow waters of mesohaline and hypersaline coastal lakes and lagoons (Kevrekidis et 

al. 1990);therefore, increased salinization in the Great Lakes due to climate change would benefit the species.

 In addition, this species grows rapidly in the summer and autumn during the warmer months (July-Sept)

(Kevrekidis et al. 1990).

 However, the effects of climate change on this species has not been specifically studied, so its actual response is 

still unknown.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Knipowitschia caucasica feeds predominately on benthic amphipods and polychaetes (Kevrekidis et al. 1990). 

Stomach contents of K. caucasica also revealed crustaceans and other benthic invertebrates, including 

copepods and larval mollusks (dreissenids;(Daoulas et al. 1993)). Given the large variety of aquatic benthic 

invertebrates in the Great Lakes and the invasian of the zebra and quagga mussels (dreissenids), K. caucasica

will have abundant food sources in the Great Lakes.

 Knipowitschia caucasica has a broad and flexible diet, and feeds primarily on benthic amphipods, polychaetes, 

chironomid larvae, copepods, and cladocerans (Kevrekidis et al. 1990). These fish are also known to feed on 
351

Dreissenid polymorpha larvae (Daoulas et al. 1993), and may benefit from the presence of dreissenids that are 

already established in the Great Lakes (Benson et al. 2014).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No documentation was found indicating any symbiotic relationships necessary for species survival. 

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

6
352

 Because K. caucasica feeds heavily on dreissenid mussel larvae (Daoulas et al. 1993), the abundance of 

dreissenid mussels in the Great Lakes may provide a sufficient food source for goby establishment.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 Given the very small size of K. caucasica (30-50 mm in length), it may be eaten by larger piscivorous fish that 

are prevalent in the Great Lakes. However, there is no literature supporting piscivorous fish preventing the 

establishment of this species in its native range. 

 Larger fish in the Great Lakes may prey on Knipowitschia caucasica but it is unknown whether that would 

prevent establishment. In the Aral Sea, it is one of the most abundant fish and is not a very important 

component of the diets of piscivorous fish (Baimov 1963). 

 It is unknown if the establishment of Knipowitschia caucasica will be prevented by parasitism. Knipowitschia 

caucasica is a host to parasites Aphalloides coelomicola, Cryptocotyle spp., Paratimonia gobii, Timoniella 

imbutiforme, and Dichelyne minutus (Krasnoyd et al. 2012); however, there is currently not enough 

information to determine if these parasites negatively impact the health of Knipowitschia caucasica, or its 

chances of establishing in the Great Lakes. 

 Aphalloides coelomicola reduces the female gonad weight of the common goby (Pomatoschistus microps) 

(Pampouli et al. 1999). There is no evidence that suggest that Aphalloides coelomicola, Cryptocotyle spp., or 

Paratimonia gobii currently occur in the Great Lakes. Timoniella spp. has been found in the Great Lakes and 

reduces the ruffe’s ability to survive in low oxygen waters (Pronin et al. 1997). Dichelyne spp. is reported to 

occur in the St. Lawrence River, but its occurrence and infection of native fish is low, and has not infected the 

nonindigenous round goby (Gendron et al. 2012).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0
353

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 This species is found primarily in the Ponto-Caspian region but has established in several areas outside its 

native range including the Northern Aegean Sea (Economidis and Miller 1990, Kevrekidis et al. 1990), Azov 

Sea, Aral Sea, and Black Sea (Daoulas et al. 1993), Adriatic Sea (Kovačić and Pallaoro 2003), inland Turkish 

lakes (Van Neer et al. 1999), Szamos River in Hungary (Halasi-Kovács et al. 2011), and Lake Pamvotis in NW 

Greece (Leonardos et al. 2008).

 Van Neer (1999) argues that the majority of invasions are caused by introduction by man, most likely with fish 

stocks and recreational activities.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

3

 This species occurs in Lake Eğirdir, Lake Eber, and Demirköprü, and is speculated to have been introduced by 

anthropogenic means due to this fish’s inability to cross hydroelectric dams to migrate up strong currents from 

the Asku River (Van Neer et al. 1999). No specimens of Knipowitschia caucasica were found in these lakes prior 

to 1992, but were abundant in Lake Eğirdir by 1996, and were found in Lake Eber in 1997 and Demirköprü 

Dam Lake in 1998. There is a possibility that Knipowitschia caucasica was unintentionally introduced in these 

lakes with the stocking of common carp fry from Ipsala/Edirne hatcheries, which are located in the same region 

where this species is common. 
354

 The authors predict that this species may spread quickly using their models that take into account the fish’s 

growth rate, survival in high temperatures, and tolerance of a wide temperature range (Kolar and Lodge 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 Given that the primary mode of introduction for this species will be through ballast water tanks, current 

treatments of ballast water entering the Great Lakes may help to prevent the establishment of the species. 

However, it is unknown how these treatments will affect this species.

 The treatment of ballast water by water exchange in the ocean may not effect this species due to their 

euryhaline nature and ability to withstand salinities from 60-24.5PSU (Kovačić and Pallaoro 2003).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 86

>100 High Adjustments

B. Critical species A*(1- 0%) 86

51-99 Moderate C. Natural enemy B*(1-0%) 86

Control measures C*(1- 0%) 86

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low
355

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Knipowitschia caucasica 

if introduced to the Great Lakes is inadequate to support proper assessment.

There is no evidence that suggests that Knipowitschia caucasica poses a threat to native species or 

outcompetes native species for resources. There are no reports on how it affects or interacts with other 

species. There is insufficient information available to determine whether Knipowitschia caucasica

reduces water quality. It is unknown whether this species alters the physical components of the 

ecosystem. 

There is little or no evidence to support that Knipowitschia caucasica has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Knipowitschia caucasica poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Knipowitschia caucasica has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

It is unknown whether Knipowitschia caucasica can act as a biological control agent. Dressenid mussel 

larvae are part of their diet (Daoulas et al. 1993), but it is unknown whether this will significantly control 

dressenid populations. It is not known to be commercially, recreationally, or medically valuable. This 

species does not improve water quality or have positive ecological impacts. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 
356

Not significantly 0 √

Unknown U

 While this species has been studied, there is no evidence of it causing any adverse effects on other species, 

especially due to toxins, poisons, or pathogens.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

 The rapid growth and reproduction of the species has been well documented (Economidis and Miller 1990, 

Kevrekidis et al. 1990, Economou et al. 1994), but there is no evidence of these characteristics causing K. 

caucasica to out-compete other species.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Predatory responses of the species have not been studied, nor is there any documentation of the species 

affecting other predator-prey interactions.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √
357

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 While K. caucasica is primarily a benthic feeder (Kevrekidis et al. 1990), there is no evidence that it disturbs the 

sediments and causes a significant increase in turbidity. 

 Other parameters, such as altered nutrients, oxygen, or chemical levels have not been studied in this species or 

similar species.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 Again, while K. caucasica is primarily a benthic feeder (Kevrekidis et al. 1990), there is no evidence that it 

disturbs the sediments and causes a significant increase in erosion. Documentation of other physical alterations 

of the ecosystem have not been documented.

Environmental Impact Total 0

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
358

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There is no information on disease or parasite transmission by this species to humans.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?
359

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the 

area’s value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 
360

Not significantly 0 

Unknown U √

 Knipowitschia caucasica primary habitat is shallow coastal lakes and lagoons (Kevrekidis et al. 1990), and it 

has been documented in riverine systems (Halasi-Kovács et al. 2011). It usually prefers bare rock or vegetation, 

with varied substrate from mud to gravel, course sands, and boulders (Kovačić and Pallaoro 2003).

 This species lays its eggs attached to the underside of small gravels, dead bivalve shells, dead roots of reeds, 

etc. and require this type of foliage for building their nests (Baimov 1963). However, there is no evidence of the 

species controlling aquatic weeds.

 Since dreissenid mussel larvae are an important food item for K. caucasica (Daoulas et al. 1993), it may be able 

to aid in controlling dreissenid mussel populations. 

 No evidence of the species controlling other nonindigenous organisms. 

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 Performing an online search of aquaria, catalogs, and biological supply companies (including Carolina 

Biological, Aquatic Biosystems, and Fisher-Scientific) did not yield any listings or information for K. caucasica

or the common name (Caucasian dwarf goby). There does not appear to be a market for this fish species; 

however, there may be some individuals who would like to purchase this species for personal fish tanks.

 The small size of the species may also make it ideal as bait for larger Great Lakes fish.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U 

 While this species is not fished for recreational in its native ranges, it is frequently found in other fish hauls and 

in fish stocks (Daoulas et al. 1993, Van Neer et al. 1999).

 While there does not appear to be a market for this species, some individuals may like to purchase this species 

for personal fish tanks. 

 The small size of the species may also make it ideal as bait for larger Great Lakes fish.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1
361

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
362

Scientific Name: Leuciscus idus

Linnaeus, 1758

Common Name: Golden Orfe, Ide

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unknown

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: High

Stocking/planting/escape from recreational culture: High

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Leuciscus idus has a high probability of introduction to the Great Lakes (Confidence level: 

Moderate).

Potential pathway(s) of introduction: Dispersal, Unauthorized Intentional Release, Escape from 

Recreational Culture

Leuciscus idus has been recorded in nine states, but the documentation of its true status in the United 

States is poor and often contradictory. It was collected in the Chenango River (tributary to the 

Susquehanna River), between Hamilton and Norwich, New York, in the early 1950s (Courtenay et al. 

1984) and also Cortland County ca. 1954 (Courtenay, personal communication). There are reports from 

unspecified waters in Illinois, Indiana, and Minnesota in the 1890s (Nico et al. 2012).

Leuciscus idus is not known to be commercially cultured in the Great Lakes region but is sold as a pond 

fish in the Great Lakes region (e.g., William Tricker, Inc. in Independence, Ohio) and online hobbyists 

report keeping this fish in Michigan.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 
363

not mobile or able to be transported by wind or water.

Unknown U √

 Leuciscus idus has been recorded from nine states, but the documentation of its true status in the United States 

is poor and often contradictory. It was collected in the Chenango River (tributary to the Susquehanna River), 

between Hamilton and Norwich, New York, in the early 1950s (Courtenay et al. 1984) and also Cortland 

County ca. 1954 (Courtenay, personal communication). There are reports from unspecified waters in Illinois, 

Indiana, and Minnesota in the 1890s (Nico et al. 2012).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U √

 Leuciscus idus has been recorded from nine states, but the documentation of its true status in the United States 

is poor and often contradictory. It was collected in the Chenango River (tributary to the Susquehanna River), 

between Hamilton and Norwich, New York, in the early 1950s (Courtenay et al. 1984) and also Cortland 

County ca. 1954 (Courtenay, personal communication). There are reports from unspecified waters in Illinois, 

Indiana, and Minnesota in the 1890s (Nico et al. 2012).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
364

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 This species is being sold as a pond fish (e.g., William Tricker, Inc. in Independence, Ohio).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1 √

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 This species is being sold as a pond fish (e.g., William Tricker, Inc. in Independence, Ohio).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 This species is being sold as a pond fish (e.g., William Tricker, Inc. in Independence, Ohio).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1 √

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 This species is being sold as a pond fish (e.g., William Tricker, Inc. in Independence, Ohio).

 Online hobbyists report keeping this fish in Michigan.
365

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 This fish is not known to be commercially cultured or transported through the Great Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 This fish is not likely to be taken up in ballast or survive those conditions.
366

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind U x U U Unknown

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 1 100 High

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
367

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not likely established in North America, including the Great Lakes

Leuciscus idus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

This species is found in both freshwater and brackish habitats (Muus and Dahlstrom 1978). However, 

they do show reduced foraging success in turbid waters (Kuliskova et al. 2009).

While this species is not well studied, it lives in a variety of waters from the heavily industrialized, 

polluted Vistula River in Poland, to the pristine Pechora River basin in northwest Russia. Thus, it would 

likely experience a range of abiotic factors, some of which would be similar to the Great Lakes. It is 

found in both large rivers and nutrient-rich lakes (Froese 2013). Leuciscus idus tolerates a wide range of 

conditions (Seeley 1962) and can successfully reproduce in waters 8-23°C (Kupren et al. 

2011). Leuciscus idus are native to northern Europe through Siberia (Berg 1949, Robins et al. 1991). As 

the winter temperatures in this region are colder than the Great Lakes, this species is likely to overwinter 

in the Great Lakes successfully. This species eats larval and adult insects, snails, and other invertebrates; 

larger individuals also take small fish (Phillips and Rix 1985).

Successive year-class strengths and growth rates in northern environments are also likely to increase as 

temperatures increase. Evidence that northward colonization is already occurring comes from Russia

(Wrona et al. 2010). Over the last 10 to 15 years, Ide (Leuciscus idus) have become much more numerous 

in the Pechora River Delta and the estuary Sredinnaya Guba (~68° N) of the Barents Sea (Wrona et al. 

2010). A study from Poland confirmed that L. idus embryos can accommodate water temperature 

increases up to 23°C (Kupren et al. 2011).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3
368

Unknown U

7

 Leuciscus idus can successfully reproduce in waters 8-23°C (Kupren et al. 2011).

 This species can tolerant to a wide range of conditions (Seeley 1962).

 This species found in freshwater and brackish habitats (Muus and Dahlstrom 1978).

 This species has reduced foraging success in turbid waters (Kuliskova et al. 2009).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Leuciscus idus is native to northern Europe through Siberia (Nico et al. 2012). As the temperatures in this 

region are colder in the Great Lakes, this species is likely to overwinter in the Great Lakes successfully.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Leuciscus idus eats larval and adult insects, snails, and other invertebrates; larger individuals also take small 

fish (Nico et al. 2012).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 3
369

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

 This species has not been studied well.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

9

 Leuciscus idus has a relative fecundity mean of 44,621 eggs/kg (Targónska et al. 2012).

 Other cyprinids:

o Relative fecundity of Carassius carassius reported as 119.2; Carassius auratus reported relative 

fecundity of 251.7 (Copp et al. 2010) and 270 (Tarkan et al. 2010).

o Relative fecundity of Carassius gibelio was 78-251 (Leonardos et al. 2008)

o Other minnow species in the family Cyprinidae, subfamily Leuciscinae, include: Fathead Minnow 

(Pimephales promelas), 6803-10164 eggs per season, also a batch spawner (Gale and Buynak 

1982); Bluntnose Minnow (Pimephales notatus), 1112-4195 eggs per season, also a batch 

spawner (Gale 1983); Red Shiner (Notropis lutrensis), 4701-8248 eggs per season, also a batch 

spawner (Gale 1986); Emerald Shiner (Notropis atherinoides), mean 3410 eggs per season 

(Campbell and MacCrimmon 1970).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0
370

Unknown U

0

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 Leuciscus idus is native to northern Europe through Siberia (Nico et al. 2012). The Siberian climate is quite 

varied, but has an average of high in January of 10F, an average high in July of 78.2. Precipitation is low in 

the north, but high in the south with heavy summer rainfall (up to 850mm).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 Sensitivity to several chemicals of L. idus was similar to Rainbow Trout and Minnow Phoxinus laevis

(Hamburger et al. 1977).

 While this species is not well studied, it lives in a variety of waters from the heavily industrialized, polluted 

Vistula River in Poland, to the pristine Pechora River basin in northwest Russia. Thus, it would likely 

experience a range of abiotic factors, some of which would be similar to the Great Lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 6
371

species already present)

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Leuciscus idus is found in large rivers and nutrient-rich lakes (Froese 2013).

 This species spawns in tributaries, eggs attached to gravel, weed and stones in shallow water (Froese 2013).

 Juveniles prefer water depth up to 2 m and flow velocities of about 0.5 m (Grift et al. 2001).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

5

 Successive year-class strengths and growth rates in northern environments are also likely to increase as 

temperatures increase. Evidence that northward colonization is already occurring comes from Russia. Over the 

last 10 to 15 years, ide (Leuciscus idus) have become much more numerous in the Pechora River Delta and the 

estuary Sredinnaya Guba (~68° N) of the Barents Sea (Wrona et al. 2010).

 A study from Poland confirmed that L. idus embryos can accommodate water temperature increases up to 23°C 

(Kupren et al. 2011).

 However, given the northern most sections of the Great Lakes are currently inhabitable by L. idus, climate 

change would not significantly benefit this species.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 0
372

be considered potential food items—are relatively scarce and/or search time is high)

Unknown U

7

 Leuciscus idus eats larval and adult insects, snails, and other invertebrates; larger individuals also take small 

fish (Nico et al. 2012).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0
373

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 This would depend on popularity of this species as a backyard pond inhabitant, which is unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6
374

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Leuciscus idus has been introduced to United Kingdom, Netherlands, New Zealand, US, and France (GISD

2010).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

3

 This species has not been well studied and has no widespread reported impacts, which would suggest it has not 

become highly invasive and spread extensively. However, it is widespread in the United Kingdom. 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0
375

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 85

>100 High Adjustments

B. Critical species A*(1- 0%) 85

51-99 Moderate C. Natural enemy B*(1- 0%) 85

Control measures C*(1- 0%) 85

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: High

Current research on the potential for environmental impacts to result from Leuciscus idus if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Leuciscus idus poses a threat to other 

species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem. 

The main concern about this species in the Great Lakes results from relationship to invasive Cyprinus 

carpio (GISD 2010). There is some concern it may outcompete native species, though has not been well 

studied. Leuciscus idus has been found to host the myxospridian parasite, Thelohanellus oculileucisci in 

Poland; but effects on fish were not mentioned (Jezewski and Kamara 1999). This species has also been 

found to host the hexamitid flagellate, Spironucleus vortens, which may transfer from cultured to wild 

populations (Sterud and Poynton 2002).

There is little or no evidence to support that Leuciscus idus has the potential for significant socioeconomic impacts if introduced to the Great Lakes.
376

It has not been reported that Leuciscus idus poses a threat to human health or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits.

Leuciscus idus has the potential for high beneficial impact if introduced to the Great Lakes.

Leuciscus idus has a huge economic value in Poland, as well as many other European countries, because its 

production is very high in comparison to other rheophilic cyprinids and it is produced as a market and sport 

fish. In addition, the ornamental form of this species (golden orfe) is also cultured. For example, between 

2000 and 2002, the production of L. idus summer fry for restocking was about 4,700,000 specimens. Oneyear-old fish production (2004) was about 27,000 kg, which is 69% and 91% of the total production of 

riverine cyprinids for 2000 and 2002, respectively (Targónska et al. 2011). Leuciscus idus has been popular 

among anglers in some countries (Turkowski et al. 2008, GISD 2010, Kupren et al. 2011).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Leuciscus idus has been found to host the myxospridian parasite, Thelohanellus oculileucisci in Poland; effects 

on fish not mentioned (Jezewski and Kamara 1999).

 This species has been found to host the hexamitid flagellate Spironucleus vortens, which may transfer from 

cultured to wild populations (Sterud and Poynton 2002).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 There is some concern it may outcompete native species, though has not been well studied. Main concern 

results from relationship to invasive Cyprinus carpio (GISD 2010).
377

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6
378

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U
379

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High
380

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 Leuciscus idus has a huge economic value in Poland, as well as many other European countries, because its 

production is very high in comparison to other rheophilic cyprinids and it is produced as a market and sport 

fish. In addition, the ornamental form of this species (golden orfe) is also cultured. For example, between 2000 

and 2002, the production of L. idus summer fry for restocking was about 4,700,000 specimens. One-year-old 

fish production (2004) was about 27,000 kg, which is 69% and 91% of the total production of riverine cyprinids 

for 2000 and 2002, respectively (Targónska et al. 2011).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Leuciscus idus has some popularity for anglers in some countries (Turkowski et al. 2008, Kupren et al. 2011).
381

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 Used in research: thermal adaptation in liver function (Braunbeck et al. 1987), chemical toxicity (Braunbeck 

and Segner 1992).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 8

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
382

0 ≥2

Unknown

1 ≥1
383

Scientific Name: Leuciscus leuciscus 

Linnaeus, 1758

Common Name: Eurasian Dace

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Leuciscus leuciscus has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Leuciscus leuciscus does not currently occur near waters connected to the Great Lakes basin. It is not

known to be able to attach to recreational gear, fauna, flora, or other objects to be later transported to the 

Great Lakes. This species is not stocked, cultured, or sold in the Great Lakes region. This species is found 

in the River Exe in south-west and River Thames in England (Cowx 1988, Araújo et al. 1999), Munster 

Blackwater in Ireland (Caffrey et al. 2007), and the Baltic Sea (Voipio 1981). This species occurs in ports 

that have direct trade connections with the Great Lakes (NBIC). It is found in waters with high levels of 

dissolved oxygen, so it is unlikely to be capable of surviving ballast tank environments for weeks at a 

time. Leuciscus leuciscus cannot tolerate high salinities of full strength seawater, so ballast water 

regulations may prevent the introduction of this species to the Great Lakes. Leuciscus leucisus may be 

introduced to the Great Lakes via ships declaring “No Ballast on Board” (NOBOB), which are exempt 

from ballast water exchange. The majority of ships entering the Great Lakes are NOBOB vessels and 

43% of these ships contain residual water with less than 10‰ salinity (Johengen et al. 2005). In the study, 

the temperature of the residual water from the vessels sampled ranged from -0.7 to 23.9°C; thus Leuciscus 

leuciscus is somewhat likely to survive the salinity and temperature of NOBOB ballast water on some 

ships. The eggs of Leuciscus leuciscus stick to substrates (Mills 1981), but it is unknown whether they 

would stick to transoceanic ship structures.

POTENTIAL INTRODUCTION VIA DISPERSAL
384

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Dace is present throughout Europe from Scandinavia to south France into the former Soviet Union. Ireland 

represents its most westward presence (Wheeler 1969, Caffrey et al. 2007)

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 The eggs of Leuciscus leuciscus stick to substrates (Mills 1981), but it is unknown whether they would stick to 

transoceanic ship structures.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
385

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 This species is sold as live bait in European countries, however is not found for sale within the Great Lakes 

basin.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
386

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Turkowski et al. (2008) evaluated the profitability of culturing the dace Leuciscus leuciscus, as a restoration 

effort in parts of Europe. There is no evidence of commercial culture being in use today.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Dace is commonly associated with high levels of dissolved oxygen and low pH; it is also only tolerant to 

mild brackish salinities (Araújo et al. 1999).

 Although Dace is tolerant to some salinities, it is not likely to survive higher salinities encountered during 

ballast water exchange (Araújo et al. 1999).
387

 Dace live in swift streams and rivers with rocky bottoms (Miller and Loates 1997).

 Juvenile Dace tend to live in shallow habitats along the shore (Kottelat and Freyhof 2007).

 Dace have been present in brackish estuaries of surveyed rivers, though is unable to travel to more saline 

waters closer to sea (Caffrey et al. 2007).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Dace live in fast moving waters although can also be present in lowland lakes (Miller and Loates 1997) and 

estuaries (Caffrey et al. 2007).

 This species is present in the North, Baltic, White, and Barents Sea basins; the Volga and Ural drainages of the 

Caspian basin; from the Danube to Dniepr drainages in the Black Sea basin; the Seine drainage of the Atlantic 

basin; and the Mediterranean basin from the Rhône to the Arc drainages (France). It is also found in very 

localized populations in the main Danube River in Romania, as well as in Scandinavia north of 69°N, most of 

central Finland, and In Siberia eastwards to Kolyma drainage (Freyhof 2013).

 In Ireland, dace expansion has followed a similar but less rapid course as the invasion of roach (Caffrey et al. 

2007).

 The eggs of Leuciscus leuciscus stick to substrates (Mills 1981), but it is unknown whether they would stick to 

transoceanic ship structures.
388

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
389

Leuciscus leuciscus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Leuciscus leuciscus inhabits rivers and lakes (Caffrey et al. 2007) and is susceptible to habitat degradation 

(Copp et al. 2007). This species occurs in the upper Thames estuary, which has a salinity range of 0.34 –

2.96 p.s.u. and water temperatures of 2.5 – 20°C (Araújo et al. 1999); these ranges are salinity and 

temperature ranges are similar to those in the Great Lakes (Reid and Orlova 2002). In the upper Thames 

estuary, Leuciscus leuciscus is most common in Isleworth, which has an average dissolved oxygen 

saturation of about 100%. It may tolerate the cool waters during the winters in the Great Lakes, but its 

capacity to overwinter may be limited by the level of dissolved oxygen (Araújo et al. 1999, Leuven et al. 

2011). Warmer water temperatures and shorter duration of ice cover may aid the establishment of 

Leuciscus leuciscus. This species is more abundant in warmer waters with lower flows, high dissolved 

oxygen, and low pH (Araújo et al. 1999); although it is found in fast flowing waters as well (Caffrey et al. 

2007). Egg and larval survival is greater when the spring-fall season is warmer (Nunn et al. 2003). 

Relative fecundity of Leuciscus leuciscus is about 40 eggs g-1(Helawell 1974), which is similar to the 

relative fecundity of Leuciscus idus that is 23.584 – 48.789 eggs g-1(Targónska et al. 2012).

This species has a relatively broad diet that varies seasonally; thus it is likely to find a food source in the 

Great Lakes basin. The distribution of Leuciscus leuciscus sometimes overlaps with that of popular sport 

fish such as brown trout Salmo trutta L. and rainbow trout Oncorhynchus mykiss Walbaum, and some 

have suggested that Leuciscus leuciscus competes with these commercially important fish for food and 

habitat; however, its competitive abilities have yet to be studied (King et al. 2011, Mann and Mills 1986). 

Dace is invasive in Ireland, and is considered a potential threat to the brown trout (King et al. 2011) and 

salmonoids (Caffrey et al. 2007). 

Leuciscus leuciscus was introduced to Munster Blackwater in Ireland in 1889 and did not spread until the 

early 1990s (Caffrey et al. 2007). In 1994, this species was first reported in the River Barrow and rapidly 

spread upstream. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3 

Unknown U

5

 This species has the ability to osmoregulate (O'hara 1976).

 This species has been present in brackish estuaries of surveyed rivers, though is unable to travel to more saline 

waters closer to sea (Caffrey et al. 2007).

 This species is eurythermal, tolerating temperatures between 4-28 ̊C (Leuven et al. 2011) and pH from 6-8.
390

 This species occurs in the upper Thames estuary which has a salinity range of 0.34 – 2.96 p.s.u. and water 

temperatures of 2.5 – 20°C (Araújo et al. 1999). In the upper Thames estuary, Leuciscus leuciscus is most 

common in Isleworth, which has an average dissolved oxygen saturation of about 100%.

 This species is more abundant in warmer waters with lower flows, high dissolved oxygen, and low pH (Araújo 

et al. 1999); although it can also be found in fast flowing waters as well (Caffrey et al. 2007).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6 

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

3

 This species as an adult may be likely to survive overwintering (Hartley 1947) .

 This species may tolerate some of these conditions such as low temperature (Araújo et al. 1999, Leuven et al. 

2011), but might not be able to tolerate low dissolved oxygen levels. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3 

This species is an autotroph. 0

Unknown U

8

 This species has a highly variable omnivorous diet (Cowx 2001).

 In the summer Dace will feed on flying insects, while in the winter it may feed on detritus, plant content and 

mollusks (Helawell 1974, Mann 1974).

 This species feeds year round and its diet changes seasonally (Cowx 2001). Its feeding activity peaks in the 

summer. It has a highly varied omnivorous diet comprising of insects, algae, and detritus. 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6
391

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3 

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0 

Unknown U

6

 This species is often observed in large shoals that can reduce the amount of food available for other species 

(Kennedy 1969).

 This species primarily feeds on the same flying insects the young trout and salmon would during summer 

months (Weatherley 1987).

 This species spawns in the same habitats (graveled areas) as would trout and salmon (Caffrey et al. 2007).

 The distribution of Leuciscus leuciscus sometimes overlaps with that of popular sport fishes such as brown 

trout Salmo trutta L. and rainbow trout Oncorhynchus mykiss Walbaum, and some have suggested that

Leuciscus leuciscus competes with these commercially important fish for food and habitat; however, the 

competitive ability of Leuciscus leuciscus has not been studied (Mann and Mills 1986).

 The Ireland Red List considers Dace one of the potential threats to brown trout populations (King et al. 2011). 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6 

Moderate 3

Low 0

Unknown U

7

 Cowx (2001) estimated that the yearly fecundity of dace was 6,550 to 9,500 eggs per 20 cm female, while other 

estimates range for 1550 to 22600 eggs (Zhukov 1965, Movchan and Smirnow 1981).

 Wilkinson and Jones (1977) found average fecundity of around 80 eggs g -1.

 Dace is reported as having high fecundity (King et al. 2011).

 Relative fecundity is reported to be about 40 eggs g-1(Helawell 1974). 

 Relative fecundity of similar species, Leuciscus idus, had average fecundities ranging from 23.584 eggs g-1to 

48.789 eggs g-1(Targónska et al. 2012). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6
392

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Within its native range, this species typically reproduces between February and March when the water 

temperature is at a minimum of 10 ̊C (Kennedy 1969).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 This species occurs in the upper Thames estuary, which has a salinity range of 0.34 – 2.96 p.s.u. and water 

temperatures of 2.5 – 20°C (Araújo et al. 1999), and the Baltic Sea, which has a salinity range of 1-15 ppt and 

water temperatures of 0 - 20°C; these ranges are salinity and temperature ranges are similar to those in the 

Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 Dace is reported as being susceptible to pollution (Copp et al. 2007).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
393

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6 

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 This species typically lives in fast moving streams and rivers, though may be found in lowland lakes (Miller and 

Loates 1997).

 This species is abundant in warmer waters with lower flows, high dissolved oxygen, and low pH (Araújo et al. 

1999).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 This species is more abundant in warmer waters (Araújo et al. 1999).

 Egg and larval survival is greater when the spring-fall season is warmer, and is positively correlated with the 

number of consecutive days > 12°C (Nunn et al. 2003).

 Low dissolved oxygen due to ice cover may limit the ability of this species to overwinter in the Great Lakes, so 

shorter duration of ice cover may aid its capacity to overwinter and its establishment. 

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6 

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3
394

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 In the summer dace will feed on flying insects, as do trout and salmon (Weatherley 1987), while in the winter it 

may feed on detritus and mollusks (Helawell 1974, Mann 1974).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

No, there is no critical species required by the species being assessed 9 

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No critical species is needed for any stage in Dace’s life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0
395

 There is no species known to facilitate Dace’s establishment.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 This fish is preyed upon by the pike and its other piscivorous relatives, though for this reason it became 

introduced to Ireland while being used as a bait fish (Winfield et al. 2011).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6
396

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

3

 This species does have sustaining populations in Ireland which is not within its native habitat (Caffrey et al. 

2007).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3 

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

3

 It took Dace over 100 years to spread beyond the Munster Blackwater after its introduction to Ireland; 

however, it took only 14 years for its subsequent spread though 70 km of river (Caffrey et al. 2007).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 Physical barriers (e.g., dams) and rotenone treatment are used to control small fish (CABI.org), and may help 

in preventing the spread of this species if introduced (CABI.org).
397

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 79

>100 High Adjustments

B. Critical species A*(1- 0%) 79

51-99 Moderate C. Natural enemy B*(1- 0%) 79

Control measures C*(1- 0%) 79

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Leuciscus leuciscus has the potential for high environmental impact if introduced to the Great 

Lakes. 

Leuciscus leuciscus is suspected to compete with salmonoids for breeding habitat (Caffrey et al. 2007). 

Efforts conserve salmonoid populations in Ireland have been hampered by Leuciscus leuciscus. Leuciscus 

leuciscus were reported to use breeding grounds intended for salmon breeding, thereby reducing the 

availability of breeding grounds for salmon. It has been suggested by Caffrey et al. (2007) and King et al. 

(2011) that if Leuciscus leuciscus reaches high abundances, it may compete with brown trout and other 

native fish of Ireland for food; however, the level of competition for food and its effects on native 

populations has not been studied in-depth. It has been reported that Leuciscus leuciscus can hybridize 

with chub (Leuciscus cephalus L.) and bleak (Alburnus alburnus L.) (Bourgeois 1963, Kennedy and 

McCarthy 1965); however, these fish do not occur in the Great Lakes and are native to Europe. Leuciscus 

leuciscus is not known to impact water quality of the physical components of ecosystems. 

Leuciscus leuciscus has the potential for high socioeconomic impact if introduced to the Great 

Lakes.
398

Leuciscus leuciscus is not a threat to human health or water quality. It does not damage infrastructure. It 

has not been reported that this species negatively affects markets or economic sectors. It does not 

diminish the aesthetic or natural value of the area it inhabits. 

Leuciscus leuciscus can reach very high densities and resides in shoals. For coarse (non-game) anglers, 

the high abundance of dace is beneficial (Caffrey et al. 2007). For game anglers, the high abundance of 

dace is a nuisance because these fish often take the lure casts intended for catching trout. The breeding 

grounds created for salmon conservation are used by dace, limiting the availability of breeding grounds 

for the salmon and hindering salmon conservation. 

Leuciscus leuciscus has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

In Ireland, Leuciscus leuciscus has become an important angling species after spreading throughout the 

River Barrow (Caffrey et al. 2007). Leuciscus leuciscus was accidently released into Irish rivers while 

being used as live bait. This species has the potential to be used as live bait and used for recreational 

coarse fishing. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 When in large numbers Dace can significantly reduce the amount of available food (Kennedy and McCarthy 

1965).

 The biggest impact Dace has had on invaded systems is the impact is has on native salmonids. They occupy the 

same habitats and have significantly similar feeding habits (Caffrey et al. 2007). Efforts to conserve salmonoids 
399

by creating suitable breeding grounds have been hampered. Dace used these breeding grounds intended for 

salmon breeding which reduced the amount of available breeding grounds for salmon. 

 Efforts to increase breeding habitat for salmonids in Ireland have been intruded upon by the Dace (Caffrey et 

al. 2007).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 √

Not significantly 0

Unknown U

 It has been known to hybridize with other species in its natural range, or with those same species in systems 

that have been invaded by both species (Costedoat et al. 2006).

 It has been reported that Leuciscus leuciscus can hybridize with Chub (Leuciscus cephalus L.) and Bleak 

(Alburnus alburnus L.) (Bourgeois 1963, Kennedy and McCarthy 1965).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0

Unknown U √
400

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 This species feeds on various types of plants depending on the season and food availability (Caffrey et al. 

2007), yet there is no mention of it altering these communities. 

Environmental Impact Total 7

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U
401

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U

 This species can reach very high abundances and resides in shoals. For coarse (non-game) anglers, the high 

abundance of dace is beneficial (Caffrey et al. 2007). For game anglers, the high abundance of dace is a 

nuisance because they often take the lure casts intended for catching trout. 

 The breeding grounds created for salmon conservation are used by dace, limiting the availability of breeding 

grounds for the salmon and hindering salmon conservation (Caffrey et al. 2007)

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 
402

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 6

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Commonly feeds on mollusks depending on season and food availability (Caffrey et al. 2007, Helawell 1974, 

Mann 1974), though little information is provided on the types of mollusks consumed by the Dace. 

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 This species is consumed by fisherman, and sometimes seen in canned form.

 This species was introduced to Ireland after accidental release of live bait (Caffrey et al. 2007).
403

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This species can reach high abundances. This species is used in Ireland for coarse angling (Caffrey et al. 

2007).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2
404

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
405

Scientific Name: Neogobius fluviatilis 

Pallas, 1814

Common Name: Monkey Goby, Sand Goby, River Goby

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Neogobius fluviatilis has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water) 

Neogobius fluviatilis is predicted to be introduced to the Great Lakes via ballast water (Holeck et al. 2004, 

Kolar and Lodge 2002, Ricciardi and Rasmussen 1998). Neogobius fluviatilis is euryhaline and can 

tolerate a broad range of temperature, so it may be able to survive ballast tank environments. It has been 

found in waters with temperatures of 0-32.4°C (Biró 1997, Sasi and Berber 2010), and salinities between 

0-10 ppt (Lejk et al. 2013, Plotnikov et al. 2012). This species occurs in waters from which shipping 

traffic to the Great Lakes originates (NBIC), including the Baltic Sea (Lejk et al. 2013). Neogobius 

fluviatilis occurs in the River Vistula catchment, which is part of the Baltic Sea basin (Copp et al. 2005). 

Neogobius fluviatilis may be introduced to the Great Lakes via ships declaring “No Ballast on Board” 

(NOBOB), which are exempt from ballast water exchange. Holeck et al. (2004) specifically states this 

introduction will be through BOB water or NOBOB residual water. The majority of ships entering the 

Great Lakes are NOBOB vessels and 43% of these ships contain residual water with less than 10%

salinity (Johengen et al. 2005). Temperature of the residual water from the vessels sampled ranged from -

0.7 to 23.9°C; thus Neogobius fluviatilis is likely to survive the salinity and temperature of the NOBOB 

ballast water (Johengen et al. 2005).

Neogobius fluviatilis does not occur near waters connected to the Great Lakes basin. This species is not 

known to adhere to any surfaces or be transported by other organisms. Neogobius fluviatilis is not 

stocked, cultured, or sold in the Great Lakes region.
406

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 The Monkey Goby, Neogobius fluviatilis, occurs throughout southeastern Europe, including the Black Sea, Sea 

of Azov, and Caspian Sea and all included tributaries (Whitehead et al. 1986). It has been invading these 

tributaries and moving towards Western Europe as far Hungary and Poland (Biró 1972, Copp et al. 1986, 

Whitehead et al. 1986).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Neogobius fluviatilis is not known to adhere to any surfaces or be transported by other organisms. There is no 

record of this form of transport, but there are mentions of aquaculture and likely ballast transport (Holeck et al. 

2004, Kolar and Lodge 2002).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1
407

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Neogobius fluviatilis is not known to be sold at any stores or supply companies. There is no record of this form 

of transport, but there are mentions of aquaculture and likely ballast transport (Holeck et al. 2004, Kolar and 

Lodge 2002).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal Score x 0.25 
408

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Unknown U

 Kolar and Lodge (2002) state that the Monkey Goby is currently in water garden or aquarium trade in Europe 

and could potentially be transported to the Great Lakes as part of this trade.

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 The Monkey Goby is not known to be commercially cultured or transported through the Great Lakes region. 

There is no record of this form of transport, but there are mentions of aquaculture and likely ballast transport 

(Holeck et al. 2004, Kolar and Lodge 2002).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40
409

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Multiple papers have predicted the probability of N. fluviatilis being introduced through ballast water (Copp et 

al. 2005, Holeck et al. 2004, Kolar and Lodge 2002, USEPA 2008). Holeck et al. (2004) specifically states that 

it could survive in BOB water or NOBOB residual water.

 Neogobius fluviatilis is known to be euryhaline and occupy brackish water. It also occupies a broad range of 

temperature that could aid in survival in ballast water (Kottelat and Freyhof 2007, Whitehead et al. 1986).

 A similar very invasive species, Neogobius melanostomus, is thought to have spread to the Great Lakes through 

ballast water. These species are rather similar in tolerances and natural ranges, further supporting this 

transport vector (Kornis et al. 2012).

 Neogobius fluviatilis was introduced to parts of the Aral Sea in the mid-1950s and currently occurs there 

(Plotnikov et al. 2012). The Aral Sea is a brackish water body and has an average salinity of 10 ppt.(Plotnikov 

et al. 2012).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Neogobius fluviatilis has spread throughout much of Europe, pushing farther and farther northwest from its 

native range. This has been no direct observation in the Baltic Sea as of 2005, but it has been found in the basin 

and predicted to reach the sea (Copp et al. 2005).

 This species was introduced to Polish inland waters during the mid-1990s and has spread to the southern Baltic 

Sea (Lejk et al. 2013).
410

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
411

Neogobius fluviatilis has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

The native and introduced ranges of Neogobius fluviatilis have similar climatic and abiotic conditions as 

the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Neogobius fluviatilis has 

not been shown to have specific habitat preferences in laboratory experiments (van Kessel et al. 2011). In 

the experiments, this species was frequently observed choosing a variety of habitat types including 

shelter, vegetation, large gravel, sand, and mixtures of gravel and sand (van Kessel et al. 2011). In the 

Danube River in Slovakia, Neogobius fluviatilis were predominantly found in stretches with gravel or 

rocky substrates (Jurajda et al. 2005). Genetic Algorithm for Rule-Set Production (GARP) model predicts 

that shallower waters of the Great Lakes provide suitable habitats for Neogobius fluviatilis, including 

parts of Lake Huron, Lake Michigan, Lake Erie, and Lake Ontario (USEPA 2008). Neogobius fluviatilis 

has a broad temperature tolerance; it inhabits waters that freeze in the winter (Biró 1997), as well as 

waters with temperatures up to 32.4°C (Sasi and Berber 2010). Neogobius fluviatilis can tolerate fresh to 

brackish waters with salinities of 0-10 ppt (Lejk et al. 2013, Plotnikov et al. 2012). Neogobius fluviatilis 

occurs in waters that have ice cover in the winter, such as Lake Balaton (Biró 1997), so it is likely to be 

capable of overwintering in the Great Lakes. Lake Balaton’s water quality was impacted by 

eutrophication in the 1960s, yet this species was able to establish there in the early 1970s (Biró 1997); 

thus nutrient levels of the Great Lakes will not likely affect the establishment of Neogobius fluviatilis. 

Due to its tolerance of a wide range of water temperatures and salinity, the effects of climate change in 

the Great Lakes may not affect the establishment of Neogobius fluviatilis. 

This species has a diverse diet of macroinvertebrates, crustaceans, gastropods, and fish (Grabowska et al. 

2009); thus it is likely to find an appropriate food source in the Great Lakes basin. In laboratory 

experiments investigating habitat competition between native and invasive species, Neogobius fluviatilis 

did not significantly alter the habitat use of the native species Cottus perifretum or Barbatula barbatula

(van Kessel et al. 2011). Depending on the size of the female, fecundity ranges from 300-2000 mature 

oocytes (Pinchuk et al. 2003). Neogobius gymnotrachelus has a fecundity of 361-2236 eggs (Grabowska 

2005), which is greater than the fecundity of N. fluviatilis. Newly established populations of Neogobius 

fluviatilis may allocate more resources to reproduction, and live longer than N. fluviatilis populations in 

their native range (Plachá et al. 2010). It exhibits parental care and has an extended spawning period, 

which may contribute to reproductive success. 

Kolar and Lodge (2002) predict that Neogobius fluviatilis will spread quickly if introduced to the Great 

Lakes. In the last 3 decades of the 20th century, this species was among 4 Ponto-Caspian gobies that 

expanded their range up the Volga River (Copp et al. 2005). This species is capable of upstream 

migration, and has expanded its range from the Djerdap Gorge in Serbia to the middle sections of the 

Danube River in Slovakia (Jurajda et al. 2005). The invasion history of Neogobius fluviatilis is 

characterized by range expansions occurring Eastern towards Western Europe. Within 7 years, it spread 

836 km downstream from the Bug River to the mouth of the Vistula River (Kostrzewa and Grabowski 

2002). After its introduction to the Aral Sea in the mid-1950s, Neogobius fluviatilis naturalized and its 

abundance grew quickly (Plotnikov et al. 2012). By the mid-1960s, Neogobius fluviatilis as well as other 

undesirable introduced goby species coincided with a significant reduction in the abundance of benthic 

invertebrates (Markova 1972, Plotnikov et al. 2012, Yablonskaya et al. 1973); however, it is unknown if 

Neogobius fluviatilis was responsible for the decline of benthic invertebrates. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES
412

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Neogobius fluviatilis is a benthic fish that occurs in temperate waters ranging from fresh to brackish and from 

4°C - 20°C. It naturally occurs in the shallow regions of the Black Sea, Sea of Azov, and Caspian Sea and also 

within the tributaries of rivers. Neogobius fluviatilis spawns once water temperature reaches 13°C (Whitehead 

et al. 1986, Kottelat and Freyhof 2007).

 Neogobius fluviatilis is found in Manyas Lake, Turkey which has water temperatures of 8.80-32.40°C and 

dissolved oxygen levels of 6.10-10.90 mg/L (Sasi and Berber 2010).

 It has been found in waters with temperatures of 0-32.40°C (Biró 1997, Sasi and Berber 2010), and salinities 

between 0-10 ppt (Lejk et al. 2013, Plotnikov et al. 2012).

 This species is found in Manyas Lake, Turkey which has dissolved oxygen levels of 6.10-10.90 mg/L (Sasi and 

Berber 2010).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Neogobius fluviatilis is a benthic dwelling goby meaning that it occurs naturally in a lower oxygen 

environment. It is recorded as surviving in temperatures as low as 4°C within its natural range (Whitehead et 

al. 1986, Kottelat and Freyhof 2007).

 Neogobius fluviatilis mainly appears in littoral zones of lakes and rivers with low oxygen levels in Hungary 

(Keresztessy 1996).

 A very similar species that has invaded the Great Lakes, Neogobius melanstomus, occurs in the same natural 

range and has extremely similar physiological tolerances (Whitehead et al. 1986, Kottelat and Freyhof 2007).

 This species occurs in Lake Balaton, Hungary, which has ice cover from December to February (Biró 1997), so 

it is likely that it can overwinter in the Great Lakes. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?
413

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Neogobius fluviatilis is a generalist that feeds upon multiple benthic dwelling organisms. Included in its diet 

are crustaceans (especially corophiid amphipods), polychaetes, bivalves, small fish, and chironomid larvae 

(Whitehead et al. 1986, Kottelat and Freyhof 2007).

 Recent studies on diet and feeding strategies have confirmed that N. fluviatilis has a broad feeding spectrum 

(Grabowska et al. 2009, Abdoli et al. 2012).Its diet consists of macroinvertebrates, crustaceans, annelids, 

gastropods, and fishes, and is dominated by chironomid larvae (Grabowska et al. 2009).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Neogobius fluviatilis has been found to have average competitive abilities. In a study concerning habitat 

selection, N. fluviatilis did not significantly affect native goby populations (van Kessel et al. 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

4
414

 Neogobius fluviatilis has a lower fecundity rate when compared with other invasive gobies such as N. 

melanostomus. Neogobius fluviatilis reaches sexual maturity at age 2 and generally spawns from May 

throughout September. Females can spawn more than once in a season but not as often as other gobies. This is 

partially due to a greater parental investment in protecting eggs until they hatch (Kottelat and Freyhof 2007, 

Plachá et al. 2010, Whitehead et al. 1986).

 In a study on an invasive population of N. fluviatilis, it was found that they exhibited higher reproductive rates 

than native populations, but still lower fecundity than other invasive gobies (Plachá et al. 2010).

 Depending on the size of the female, fecundity ranges from 300-2000 mature oocytes (Pinchuk et al. 2003). 

Neogobius gymnotrachelus has a fecundity of 361-2236 eggs (Grabowska 2005), which is greater than the 

fecundity of Neogobius fluviatilis.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 There are a few reproductive strategies that would likely assist N. fluviatilis in establishing. They are one of the 

few goby species in which the male takes care of the eggs until hatching. Furthermore, males grow larger and 

live longer. Some non-native populations have been found to live longer than native populations, which would 

allow more chances for spawning, and possibly increase invasion potential (Plachá et al. 2010).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8
415

 Neogobius fluviatilis has been predicted to be very environmentally compatible with all five Great Lakes, at 

least in the shallower regions. Being closely related to N. melanostomus, which has successfully invaded all 

five Great Lakes, supports this prediction (USEPA 2008).

 In its native range Neogobius fluviatilis inhabits brackish lagoons of the Black Sea, Azov Sea, and Caspian Sea 

(Grabowska et al. 2009).

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Neogobius fluviatilis has been predicted to be very environmentally compatible with all five Great Lakes, at 

least in the shallower regions. Being closely related to N. melanostomus, which has very successfully invaded 

all five Great Lakes, supports this prediction (USEPA 2008).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

 Neogobius fluviatilis successfully established in Lake Balaton, Hungary in the early 1970s (Biró 1997). This 

lake experienced severe eutrophication in the 1960s. 

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Predictions made by USEPA (2008) show that most of Lake Erie, and parts of Lake Huron and Lake Ontario 

will be suitable habitat for N. fluviatilis. Being closely related to N. melanostomus, which has successfully 

invaded all five Great Lakes, supports this prediction (USEPA 2008).
416

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Neogobius fluviatilis, due to its wide range of tolerances, would adapt easily to warmer water temperatures and 

possibly increased salinization (Kottelat and Freyhof 2007, Whitehead et al. 1986).

 It has been found in waters with temperatures of 0-32.40°C (Biró 1997, Sasi and Berber 2010), and salinities 

between 0-10 ppt (Lejk et al. 2013, Plotnikov et al. 2012).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Neogobius fluviatilis feeds upon a wide range of benthic macroinvertebrates (Kottelat and Freyhof 2007, 

Whitehead et al. 1986), including bivalves such as the invasive zebra and quagga mussels (Kipp et al. 2012). 

 Neogobius fluviatilis has an extremely similar diet to N. melanostomus which has spread across North America 

with no dietary constraints (Kipp et al. 2012).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

9
417

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 The only reproductive requirement N. fluviatilis has is small stones and aquatic plants to which to attach its 

eggs. There are no otherwise required species in its life cycle (Kottelat and Freyhof 2007, Whitehead et al. 

1986).

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

1

 There is no species that aids the establishment and spread of N. fluviatilis, although the presence of dreissenid 

mussels may help to support its diet. Neogobius melanostomus, A related species is known to predateom 

dreissend mussels in the Great lakes absin (Hogan et al. 2007).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

-80% total 

points (at 
418

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Neogobius fluviatilis has spread across Europe with no recorded preferential predation or prevention of spread 

occurring. There are reports of predation by native pikeperch, but they only target N. fluviatilis at certain size 

classes (Specziár 2011).

 Neogobius fluviatilis can become slightly larger than other similar gobies and benthic dwelling fish, possibly 

making it a preferred target for larger piscivores, but there are no records of this (Kottelat and Freyhof 2007, 

Whitehead et al. 1986).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 There is no record of N. fluviatilis actually being transported by ballast water or through live trade. There have 

been multiple predictions that this vector will lead to its introduction, but as there are no actual cases, it is 

assumed that inoculations are very low (Kolar and Lodge 2002, Holeck et al. 2004).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6
419

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 Neogobius fluviatilis has spread from its native range of the Black and Caspian Seas to the Baltic Sea basin, 

Aral Sea, and throughout western and eastern Europe (Copp et al. 2005). 

 It is capable of upstream migration (Jurajda et al. 2005).

 This species can be found from the Ponto-Caspian to Hungary (Ahnelt et al. 1998), Slovakia (Jurajda et al. 

2005), Poland (Tockner et al. 2009), and the Netherlands (van Kessel et al. 2009). It has historically spread 

from east to west. 

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 There are documented geographical ranges of N. fluviatilis reported from the early 1970s (Biró 1972). Recent 

studies show that this range has increased extensively, almost doubling in roughly 30 years (Copp et al. 2005, 

Kottelat and Freyhof 2007, Whitehead et al. 1986).

 A primary cause of this spread is human activities, such as connecting rivers and international shipping (Copp 

et al. 2005, Kornis et al. 2012).

 It was found in the Bug River in Poland in 1997, and within 7 years it expanded 836 km to the mouth of the 

river (Kostrzewa and Grabowski 2002). 

 After its introduction to the Aral Sea in the mid-1950s, Neogobius fluviatilis naturalized and its abundance 

grew quickly (Plotnikov et al. 2012).

 Kolar and Lodge (2002) predict that Neogobius fluviatilis will spread quickly if introduced to the Great Lakes.

 Over the past few decades, it has extended its range to include the Slovakian section of the Danube (Jurujda et 

al. 2005). 

 In the last 3 decades of the 20th century, this species was among 4 Ponto-Caspian gobies that expanded their 

range up the Volga River (Copp et al. 2005).

 Within 7 years, it spread 836 km downstream from the Bug River to the mouth of the Vistula River (Kostrzewa 

and Grabowski 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

-90% total 

points (at 
420

highly effective in preventing the establishment and spread of this species) end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 Rotenone is one possibly control measure that could be used to control the establishment/spread of N. 

fluviatilis. It is a chemical measure that is mainly used to protect fisheries and only has a few other realistic 

applications. It would likely not be a realistic control measure (Abdel-Fattah 2011).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 101

>100 High Adjustments

B. Critical species A*(1- 0%) 101

51-99 Moderate C. Natural enemy B*(1- 0%) 101

Control measures C*(1- 0%) 101

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate
421

Neogobius fluviatilis has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Neogobius fluviatilis is known to be the carrier of some species of parasites, and, it had the greatest 

parasite diversity and the lowest parasite abundance compared to 2 other non-native goby species found 

in the Danube River (Ondračková et al. 2005). None of the parasites were brought to the Danube by the 

introduction of Neogobius fishes; rather, they were common in the Danube. The parasite loads in 

Neogobius fluviatilis in the Danube River were similar to the parasite loads in their native range. Parasites 

of Neogobius fluviatilis in the Danube River include trematoda Nicolla skrjabini (Iwanitzky, 1928), 

Metagonimus yokogawai (Katsurada, 1912), Apatemon cobitidis (Linstow, 1980), Pomphorhynchus laevis

(Müller, 1776), Raphidascaris acus (Bloch, 1779), ciliophora Ichthyophthirius multifiliis (Fouquet, 1876), 

Eimeria daviesae (Molnár, 2000), and Goussia kessleri (Molnár, 2000) (Molnár 2006). Specimens of 

Neogobius fluviatilis in the Vistula River were infected with the metacercariae of Bucephalus 

polymorphus, a parasite that also infects zebra mussels (Kvach and Mierzejewska 2011). The effects of 

the parasites infecting Neogobius fluviatilis on zebra mussels have not been reported.

Where introduced, Neogobius fluviatilis may potentially impact native fish populations. A marked decline 

in tubenose goby in the Danube River was attributed to the rapid expansion of round goby and monkey 

goby populations in 2004 (Molnár 2006). Experiments investigating habitat competition between nonnative and native fish of the Rhine and Meuse rivers did not find that native fish Cottus perifretum or 

Barbatula barbatula changed their selection of habitat type when they co-occurred with Neogobius 

fluviatilis. These experiments suggest that Neogobius fluviatilis does not compete with native benthic fish 

for habitat, but its competitive behavior may change during spawning season (van Kessel et al. 2011).

Neogobius fluviatilis makes up a substantial proportion of the diets of piscivorous fish such as Sander 

lucioperca and S. volgensis in Lake Balaton (Specziár 2011). The effects of non-native prey on the diets 

of S. lucioperca and S. volgensis or on predator-prey relationships has not been explored. The expansion 

of Neogobius fluviatilis as well as other undesirable introduced goby species coincided with a significant 

reduction in the abundance of benthic invertebrates (Markova 1972, Plotnikov et al. 2012, Yablonskaya et 

al. 1973); however, it is unknown if Neogobius fluviatilis was responsible for the decline of benthic 

invertebrates.

There is little or no evidence to support that Neogobius fluviatlis has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Neogobius fluviatilis poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

Neogobius fluviatilis has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

In Turkey, Neogobius fluviatilis is important to minor commercial fisheries, aquarium, and bait (Sasi and 

Berber 2010). They may serve as a source of food for economically important fish species such as pikeperch Stizostedion lucioperca (Lenhardt et al. 2011). 

POTENTIAL ENVIRONMENTAL IMPACT
422

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Neogobius fluviatilis, like other gobiids, is known to be the carrier of a large number of parasites. During a 

survey of Neogobius species that had recently invaded Hungarian reaches of the Danube River upstream from 

Budapest, it was found that Monkey Gobies introduced parasites of a wide host range, such as the trematode 

Nicolla skrjabini, the metacercariae of Metagonimus yokogawai and Apatemon cobitidis, the larval stages of 

the acanthocephalan Pomphorhynchus laevis and the nematode Rhaphidascaris acus, the glochidia of an 

Anodonta sp. (Mollusca), and the ciliophoran Ichthyophthirius multifiliis. The specific parasites of Neogobius

spp. were represented by three intestinal coccidia: Eimeria daviesae, Goussia kessleri, and a new species 

described here as Goussia szekelyi sp. (Molnár 2006).

 Kornis et al. (2012) mentioned a loose connection between trematodes infecting N. melanostomus being passed 

onto double-crested cormorants Phalacrocorax auritus.

 Neogobius fluviatilis was found to be an intermediate host of Bucephalus polymorphus which can affect 

Dreissenia polymorpha and fish that feed on these two intermediate hosts (Kvach and Mierzejewska 2011).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U 

 Neogobius fluvialitis is a potential competitor with benthic fish species native to its introduced ranges in 

Central Europe. Monkey Gobies have overlapping diets with benthic species native to Europe such as Blicca 

Bjoerkna (Freyhof and Kottelat 2008b, van Kessel et al. 2011). However, according to the results of these 

studies, interspecific competition might not be a strong factor because of dissimilarities in spatial foraging and 

shelter preferences among these species. van Kessel and others (2011) noted that due to the relatively small size 

of the gobiids used in their experiment, competition forces might have been downplayed. Another study carried 

out in the Hungarian reaches of the Danube found that previously widespread Proterorhinus marmoratus

populations were drastically reduced in the presence of N. melanostomus and N. fluviatilis (Molnár 2006).

 A study of invasive gobies in the lower Rhine found that N. fluviatilis is extremely opportunistic and did not 

outcompete other invasive goby species but rather exploited resources that were not in use (Borcherding et al. 

2013)

E3) Does it alter predator-prey relationships? 
423

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

A study done on native Pike-perch showed that N. fluviatilis can be an important prey species during ontogeny, 

reducing the predation pressure placed on other native prey fish (Specziár 2011). This has the potential to result in 

a trophic cascade.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 There is no record of a genetic effect on native populations.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

 There is no record of an effect on water quality.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6
424

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 There is no reported effect on other physical components of the ecosystem.

Environmental Impact Total 3

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 Neogobius fluviatilis carries multiple parasites that affect fish and invertebrates but none that pose any threat 

to human health (Molnár 2006).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1
425

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not cause damage to infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not negatively affect water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not negatively affect any economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not negatively affect recreational activities.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not negatively affect the natural value of invaded areas.
426

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not act as a biological control.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 The Monkey Goby does not seem to have a significant economic or commercial value, besides its importance 

for minor commercial fisheries, aquariums, and bait (Sasi and Berber 2010). However, this species may serve 

as favorable food for economically important fish species (Catfish Silurus glanis, Pike-perch Stizostedion 

lucioperca). The increase in the commercial catch of Pike-perch in the last few years in Serbia has been likely 

due in part to an increase in the amount of gobiids found in the food consumed by Pike-perch (Lenhardt et al. 

2011).
427

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Anglers use this species as good bait for catfish and pike-perch (Lenhardt et al. 2011).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not have any medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

 Neogobius fluviatilis does not improve water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 This species does not have another positive ecological effect.
428

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
429

Scientific Name: Oncorhynchus keta 

Walbaum, 1792

Common Name: Chum Salmon

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Oncorhynchus keta has a low probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: None

Oncorhynchus keta was introduced to the Great Lakes region by American and Canadian agencies in 

order to develop a self-sustaining, wild population to contribute to food, commercial, and recreational 

fisheries (Crawford 2001). From 1908 to the 1940s, Oncorhynchus keta were raised in hatcheries in 

Michigan, Pennsylvania, and Wisconsin, for release into Lakes Superior and Lake Huron (MacCrimmon 

1977). The Chum Salmon were unable to form a self-sustaining population, and stocking programs ended 

in 1945. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
430

 Oncorhynchus keta does not naturally occur near waters that are connected to the Great Lakes; they are being 

transported by environmental agencies to the Great Lakes to study their ability to survive (Crawford 2001).

 It is very unlikely that Oncorhynchus keta will be able to swim to the Great Lakes basin through streams or 

ponds (Crawford 2001).

 Chum Salmon occurs naturally in areas that are far away and not directly connected to the Great Lakes. 

According to ybersalmon.fws.gov chum salmon usually spawn in coastal rivers. They occupy the Chukchi and 

Bering Seas, disperse west along the Aleutian chain, and south into the Gulf of Alaska.

 Oncorhynchus keta is a pacific salmon with a wide geographic distribution. It occurs in North America from 

Montery, California, to the Arctic coast and east to the Mackenzie River (Salo 1991).

 Chum Salmon are strong swimmers that have been documented migrating about 2820 km to its spawning 

ground in the Yukon River from the sea (Behnke 2010).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
431

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 No research shows that it is bought by people and kept as pets, due to its size (24-48 inches long and could be 

up to 13 lbs in weight).

 An extensive review of fish sold at live fish markets and in the aquarium trade conducted by Rixon et al. (2005) 

did not show that Oncorhyncus keta is sold nearLakes Erie or Ontario.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Oncorhynchus keta was one of the many salmonine fish released by American and Canadian agencies into the 

Great Lakes during 1870-1960 for the purpose of developing a self-sustaining populations to support food, 

commercial, and/or recreational fisheries (Crawford 2001).

 From 1908 to the 1940s, Oncorhynchus keta were raised in hatcheries in Michigan, Pennsylvania, and 

Wisconsin, for release into Lakes Superior and Lake Huron (MacCrimmon 1977). The Chum Salmon were 

unable to form a self-sustaining population, and stocking programs ended in 1945.

 Chum Salmon have been introduced into Bannock County, Idaho (Simpson and Churchill County (probably 

Lahontan Reservoir); Damariscotta, Megunticook, and Swan lakes, Maine Deep Lake in Oakland 

County, Michigan; Mineral Count, and Washoe County (probably Truckee River), all in the Lahontan 

drainage, Nevada and non-specific sites in Nevada; and Strawberry Reservoir and Fish Lake in Utah (Fuller 

2006). Most of the populations did not survive.

4b) What is the nature and proximity of this activity to the Great Lakes basin?
432

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 The species does not natively exist in the Great Lakes region and as a result it is most likely not cultured in or 

transported through this region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100
433

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 According to Hale et al. (1985), temperature and other conditions affect the Chum Salmon’s ability to survive 

and spawn.

 This species is able to tolerate a variety of salinities (Clarke and Hirano 2010).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
434

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in the continental United States (Alaska), including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
435

Oncorhynchus keta has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

The native ranges of Oncorhynchus keta have similar climatic conditions as the Great Lakes. 

Oncorhynchus keta can tolerate a broad range of salinity and survive abrupt changes in salinity (Clarke 

and Hirano 2010). Optimal water temperatures for Oncorhynchus keta are between 5-27°C (Hale et al. 

1985). This species experiences high mortality when dissolved oxygen drops below 2 mg/L. 

Oncorhynchus keta is capable of surviving winter temperature in the Great Lakes, but its ability to 

overwinter is limited by its oxygen requirements. There are populations of Oncorhynchus keta that 

overwinter in the North Pacific, the Gulf of Alaska, and the Bering Sea (Urawa et al. 2004), usually in 

waters that are 4-6°C. During homing migration, Chum Salmon make vertical diel movements to deeper 

waters to feed, experiencing temperatures under 5°C regularly (Azumaya and Ishida 2005). Although 

Chum Salmon can tolerate such low temperatures, it may not be able to for long periods of time, and 

behaviorally avoids them by moving to shallower waters periodically.

Oncorhynchus keta opportunistically feeds on zooplankton, invertebrates, mollusks, and fishes, and has a 

relatively broad diet compared to other Oncorhynchus species (Behnke 2010, Kaeriyama et al. 2004). The 

Chum Salmon fry feed on small invertebrates as they migrate downstream and on crustaceans as they 

move into estuaries. Oncorhynchus keta will likely find an appropriate food source if introduced to the 

Great Lakes. Alewife, Alosa pseudoharengus, is an established nonindigenous species in the Great Lakes 

and may provide a food source for introduced salmon (Crawford 2001), such as Oncorhynchus keta. 

For successful reproduction, Chum Salmon require loose streambed gravel to lay their eggs (Bakkala 

1970). Chum Salmon migrate upstream to rivers to spawn, can reproduce successfully in intertidal zones 

at the mouth of streams (Behnke 2010) and in lakes with upwelling groundwater (Wilson 2006). Chum 

Salmon migrate upstream to spawn at temperatures under 15°C and dissolved oxygen levels greater than 

6.3 mg/L (Hale et al. 1985). They have been observed migrating upstream in waters that are as low as 

4.4°C, and temperatures above 25.5°C are lethal. The Chum Salmon fry prefer temperatures of 12-14°C, 

and have lethal water temperature limits above 23.8°C and below -0.1°C (Brett and Alderdice 1958). 

Chum fry undergoes developmental changes for life in sea water, and migration to sea water within the 

first summer is necessary for survival (Hale et al. 1985); however, chum salmon have been reared to 

maturity in freshwater in captivity (R.L. Burgner pers. comm. in Salo 1991).

Previous introductions of Onchorhynchus keta to the Great Lakes did not result in the establishment of 

self-sustaining populations (Crawford 2001, MacCrimmon 1977). It was also introduced to the Gulf of 

Riga, in the bay of the Baltic Sea, but has only been found in small numbers (Ojaveer 1995). 

Oncorhynchus keta is predicted by Kolar and Lodge (2002) to be intentionally introduced to the Great 

Lakes for the purpose of aquaculture or sport, and will spread at a fast rate if introduced. Although Kolar 

and Lodge (2002) predict high probability of establishment and spread, the history of this species in the 

Great Lakes, which includes nearly 40 years of stocking, suggest that some unknown factors prevent its 

establishment in the Great Lakes region.

There have been several studies conducted on how climate change affects Chum Salmon, but none have 

predicted how climate change in the Great Lakes may impact Chum Salmon establishment. In the 

subarctic North Pacific, increased Chum fingerling growth rates correlated with increased zooplankton 

biomass as a result of climate change in the late 1980s (Seo et al. 2006). In the Gulf of Alaska, Chum 

Salmon diets switched from one dominated by gelatinous zooplankton to one with greater diversity of 

zooplankton species due to climate alterations caused by El Niño and La Niña events (Kaeriyama et al. 

2004). Models developed by Harvey et al. (2012) predict that Chum Salmon post-spawning carcasses will 
436

decompose at a faster rate due to warming and climate change. Chum Salmon are a major component of 

overwintering bald eagle diets in the Puget Sound, and faster carcass decomposition rate may decrease the 

biomass of carcasses available for the bald eagles. The effects of climate change such as warmer water 

temperatures and shorter duration of ice cover may aid the establishment of Oncorhynchus keta and 

enable it to overwinter in the Great Lakes. Chum Salmon fry require migration to seawater (Hale et al. 

1985), so increased salinization may increase their survival in the Great Lakes. 

This species may be vulnerable to habitat degradation. Chum Salmon populations that spawned in the 

Columbia River basin had declined by the 1950s (Behnke 2010). The spawning habitat quality was 

degraded by upstream logging, pollution and water diversions, resulting in spawns of 1,000 to 5,000 fish. 

By 2011, spawning runs had attained 10,000 fish for the first time in 46 years after the implementation of 

habitat protection and enhancement (Behnke 2010?). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Chum Salmon can survive in most ranges of salinity from fresh water lakes to the Pacific Ocean; they can 

tolerate all ranges. In a study done by Hasegawa et al.1987 showed the Chum Salmon maintained good 

osmoregulatory ability when tested by direct transfer to fresh water from salt water or by direct transfer from 

salt water to fresh water and the fish was able to adept and adjust its sodium concentration within 24 hours. 

Chum Salmon can tolerate low and high temperature between 2°C and 26°C (Arntzen 2009).

 Chum Salmon can live at low oxygen saturation as long as its above 2 mg/l. Chum Salmon try to avoid 

dissolved oxygen levels below 4.5 mg/l. Dissolved oxygen level greater then 6.3 mg/l are recommended for a 

successful upstream migration of anadromous salmonids and lower DO and more likely to inhibit upstream 

migration. In 1981 when Chum Salmon migration was blocked by low flows, crowding them in to a pool where 

the dissolved oxygen levels dropped below 2.0 mg/l high mortalities of salmon was reported is southeast Alaska 

streams (Hale et al. 1985). Chum Salmon have different diets when their in fresh water compared to when they 

are in oceans; they eat a wide verity of food which range from small fishes to some insects and stoneflies.

 Chum salmon are able to resist changes in salinity (Clarke and Hirano 2010).

 Oncorhynchus keta may be vulnerable to habitat degradation. Chum Salmon populations that spawned in the 

Columbia River basin had declined by the 1950s (Behnke 2010). The spawning habitat quality was degraded by 

upstream logging, pollution and water diversions, resulting in spawns of 1,000 to 5,000 fish. By 2011, spawning 

runs had attained 10,000 fish for the first time in 46 years after the implementation of habitat protection and 

enhancement.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?
437

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 Studies done by (Hale et al. 1985) showed high mortality in Chum Salmon when dissolved oxygen levels 

dropped below 2 mg/L, salmon avoid migrating up stream when dissolve oxygen levels drop below 4.5 mg/L. 

the study by the united states energy department found that the range of temperature for salmon is between 5 

and 27 degree Celsius. No Chum has yet been found in waters below 5°C.

 On the contrary, a study conducted by Azumaya and Ishida (2005) on the thermoregulation of Chum Salmon 

during diel movements found that the fish do occur in water less than 5°C during the day to feed in the Bering 

Sea. It can tolerate low temperatures, but behaviorally avoids them for long periods of time by making vertical 

diel movements.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Chum Salmon fry feed on small invertebrates as they move downstream and on crustaceans as they move into 

estuaries (Behnke 2010).

 Adult chum opportunistically feed on invertebrates, mollusks, and fishes (Behnke 2010). 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
438

Unknown U

9

 Open lake environment studies have shown that introduced salmons forage voraciously on the same species that 

is dominant in lakes char diets, causing declines in Alewife population. Introduced salmonids outcompeted 

smaller native species for limited food cover and stream positions (Crawford 2001).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Chum Salmon reproduce once in their life time, they need about four years to sexually mature. Usually Chum 

Salmon spend about 4 years in the ocean and then migrate to fresh water where they spawn and die after 2 

weeks. Salmon return to their place of birth to spawn. They choose rivers and lakes where the water flows and 

cooler water (Crawford 1985). Chum Salmon migrate to their place of birth when the dissolved oxygen 

concentration is above 6.5 mg/L (Alaska Department of Fish and Game 2015).

 Chum Salmon are semelparous and anadromous (Salo 1991).

 Chum Salmon eggs are more resisant to saltwaters than Coho, Chinook, and Sockeye Salmon (Clarke and 

Hirano 2010).

 Chum Salmon fecundity ranges from 900 to 8,000 eggs (Bakkala 1970). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Stocking of Oncorhynchus keta stopped in 1945 after unsuccessful attempts to creating a self-sustaining chum 

salmon population in the Great Lakes (Crawford 2001).

 Chum Salmon eggs and fry exhibit a greater salinity resistance than Coho, Chinook, and Sockeye Salmon 

(Clarke and Hirano 2010).
439

 Eggs can survive varying levels of salinities (Behnke 2010). Successful reproduction can occur at the intertidal 

zones at the mouths of streams.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The air temperature, precipitation, seasonality of native range (North Pacific) is similar to the Great Lakes. 

Chum Salmon can tolerate a wide range of temperatures from 5°C to 27°Celsius (Hale et al. 1985).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Chum Salmon are very adaptive species that can tolerate a wide range of environments, the fish have well 

developed kidneys to handle the salinity changes when the fish migrate between salt and fresh water.

 All the requirements that Chum Salmon need to live and reproduce are available in the Great Lakes from 

dissolved oxygen concentration to temperature. Chum Salmon has the ability to adapt very fast to salinity 

(Clarke and Hirano 2010).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3
440

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 In the study done by (Crawford 2001) shows that salmon migrate within the lake to areas with suitable 

conditions.

 A population of Chum Salmon has spawned in Kluane Lake where there is upwelling groundwater (Wilson 

2006). 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

4

 There have been several studies conducted on how climate change affects Chum Salmon, but none have 

predicted how climate change in the Great Lakes may impact Chum Salmon establishment. 

 Increased fingerling growth rates correlated with increased zooplankton biomass as a result of climate change 

in the late 1980s in the subarctic North Pacific (Seo et al. 2006).

 In the Gulf of Alaska, Chum Salmon diets switched from one dominated by gelatinous zooplankton to one with 

greater diversity of zooplankton species due to climate alterations caused by El Niño and La Niña events 

(Kaeriyama et al. 2004). 

 Models developed by Harvey et al. (2012) predict that Chum Salmon carcasses as a result from spawning will 

decompose at a faster rate due to warming and climate change. Chum Salmon are a major component of 

overwintering bald eagle diets in the Puget Sound, and faster carcass decomposition rate may decrease the 

biomass of carcasses available for the bald eagles.

 Waters temperatures that are too high may be detrimental for chum salmon survival (≥23.8°C) and 

reproduction (≥25.5°C) (Brett and Alderdice 1958, Hale et al. 1985).

 Great Lakes’ water temperatures in the winter are around the lower limit for this species (4-6°C) (Urawa et al. 

2004).Warmer water temperatures and shorter duration of ice cover may aid the establishment of this species.

 Chum salmon cannot tolerate low oxygen levels caused by ice cover (Hale et al. 1985), so shorter duration of 

ice cover may benefit this species.

 Chum fry develop a physiology that requires sea water for survival as it matures (Hale et al. 1985), so the 

Great Lakes would be more suitable for chum salmon establishment if it exhibited increased salinization.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 9
441

be considered potential food items—are highly abundant and/or easily found)

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 Chum Salmon have a very similar diet to King Salmon (Oncorhynchus tshawytscha), the latter of which has 

successfully been introduced into the Great Lakes. They both consume insects and invertebrates while in rivers, 

and fish while in the ocean. However, Chum Salmon also consume mollusks, squid and tunicates while in the 

ocean, which are not available in the Great Lakes (NOAA Fisheries 2014).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Chum Salmon does not require any other species to reproduce.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

9
442

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

4

 Alewife is not native to the Great Lakes (USGS) but does provide a food source for introduced salmon. It would 

be expected that Alewife would be a food source for Oncorhynchus keta as well (Crawford 2001).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 While viral hemorrhagic septicemia affects salmon populations (including Chum Salmon), is has not eliminated 

any salmon species and is thus unlikely to be responsible for complete prevention.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3
443

Infrequent, small or moderate inocula 0

Unknown U

2

 Introduction of Chum Salmon to the Great Lakes started in the 1870s by American and Canadian fishery 

agencies (Crawford 2001). Recently no major introduction events have occurred in the Great Lakes, or at least 

no documentation is available to say otherwise.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

3

 Chum Salmon depends on fresh water to reproduce and they have big native areas in the northern Pacific that 

extend from the Yukon River to waters just outside of Alaska (Alaska Department of Fish and Game 2015). The 

species was introduced to the Great Lakes due to direct introduction by humans from the 1870s to 1960s 

(Crawford 2001).

 Oncorhynchus keta was released into the Gulf of Riga in the 1970s, but have only been found in small numbers 

(Ojaveer 1995). 

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

0

 Most catch and release in the Great Lakes occur within the living range of Chum Salmon therefore the spread 

is very slow and is dependent on the food abundance because salmon is documented to migrate to areas with 

high food abundant (Crawwford 2001)
444

 Oncorhynchus keta is predicted by Kolar and Lodge (2002) to be intentionally introduced to the Great Lakes 

for the purpose of aquaculture or sport, and will spread at a fast rate if introduced.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 No control methods have been set to prevent the establishment or spread of this species in the Great Lakes.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 86

>100 High Adjustments

B. Critical species A*(1- 0%) 86

51-99 Moderate C. Natural enemy B*(1- 0%) 86

Control measures C*(1- 0%) 86

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS
445

Environmental: Moderate

Socio-Economic: Low

Beneficial: High

Oncorhynchus keta has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Chum Salmon can hybridize with Chinook and Kokanee Salmon (Sasaki et al. 1968, Seeb et al. 1993), 

popular sport fish in the Great Lakes, but there is no indication that it can hybridize with fish native to the 

Great Lakes. Introduced salmon, such as Chum Salmon, may compete with native species for food 

(Crawford 2001), but what species will be impacted by the introduction of Chum Salmon has not been 

investigated. Crawford (2001) suggested that, as vectors for parasites, hatchery-reared salmon may 

threaten native fish species. Sea lice (Lepeophtheirus salmonis) infection rates in wild juvenile Chum 

Salmon and Pink Salmon were higher for populations that occurred near salmon farms than those that 

were not located near salmon farms in British Columbia, Canada (Morton et al. 2004). Sea lice are 

ectooparasites that can infect other salmonoid species, but fall off the host when they migrate to 

freshwater. When Chum Salmon create breeding nests, they create a small depression in the gravel, which 

may cause mild effects on the physical habitat.

There is little or no evidence to support that Oncorhynchus keta has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Oncorhynchus keta poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

Oncorhynchus keta has the potential for high beneficial impact if introduced to the Great Lakes.

Oncorhynchus keta quality deteriorates as it develops for spawning, and those that are ready to spawn are 

not often sold in the United States (Behnke 2010). In commercial fisheries, Oncorhynchus keta has a 

lower value than other salmon species such as Chinook, Coho, or Sockeye Salmon due to its low fat 

content and pale pink flesh that are not preferable to consumers. Oncorhynchus keta is usually caught 

from commercial fisheries to be canned. It is sometimes sold fresh or frozen under the name of “silver 

bryte salmon”. Native Americans in Canada and Alaska eat Chum Salmon, as well as dry and smoke the 

fish to feed their dogs.

In Japan, Chum Salmon goes by the name “sake”, and is ranched there (Behnke 2010). Chum Salmon 

meat is used in sushi and sashimi. Chum Salmon that have reached sexual maturity and have spawned-out 

are harvested for their thick, tough skin to create salmon leather. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.
446

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 In general, hatchery-reared salmon may present new parasites and instigate a risk to the native fish (Crawford 

2001).

 Of all the Great Lakes species, native salmonines (Lake Charr, Brook Charr) are likely the most susceptible to 

these new diseases and parasites. The intensive culture of hatchery-reared salmonines poses a threat to native 

fishes by artificially increasing the disease and 'parasite 'reservoir that native fishes are exposed to in the wild 

(Crawford 2001). However, the risk of Chum Salmon parasites infecting native fish of the Great Lakes has not 

been studied. 

 Sea Lice (Lepeophtheirus salmonis) infection rates in wild juvenile Chum Salmon and pink salmon were higher 

for populations that occurred near salmon farms than those that were not located near salmon farms in British 

Columbia, Canada (Morton et al. 2004). Sea Lice are ectooparasites that can infect other salmonoid species, 

but fall off the host when they migrate to freshwater.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 In open lake environments, studies have shown that introduced salmonids forage voraciously on the same 

species that is dominant in Lake Charr diets (the declining of alewife populations (Crawford 2001). Alewifes 

are non-native.

 Introduced salmonids outcompete smaller, native fish species for limited food, cover, and stream positions 

(Crawford 2001).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √
447

Not significantly 0

Unknown U 

 Predation by salmonids on native species in the Great Lakes is a major problem because the stocked fish are 

‘generalist’ vertebrate predators that can feed on numerous prey (Crawford 2001).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 In both tributaries and open lake environments of the Great Lakes, introduced salmon have affected native fish 

populations though hybridization and introgression (Crawford 2001).

 Chum Salmon can hybridize with Chinook Salmon and Koanee Salmon, which are not native to the Great Lakes

(Seeb et al. 1993, Sasaki et al. 1968). 

 Chum and Pink Salmon are closely related and may spawn in the same streams but avoid hybridization by 

spawning at a different time or at a different spawning ground (Behnke 2010). These two species are able to 

produce fertile hybrids, but no self-sustaining hybrid populations are known. Pink Salmon are not native to the 

Great Lakes.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

 Introduced salmonids migrating into tributaries in the Great Lakes have shown to increase levels of limiting 

nutrients and toxins accumulated while in the open lakes which changes the community ecology in these 

tributaries (Crawford 2001).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √
448

Not significantly 0 

Unknown U

 The physical alterations of digging nests or superimpose their redds have been shown to have community-level 

effects on the abundance and distribution of native fishes and invertebrates in the tributaries. Spawning runs of 

introduced salmonids have also been shown to transport significant levels of contaminants upriver from the 

lakes (Crawford 2001). 

Environmental Impact Total 3

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 Salmon are semelparous, which means they migrate upstream to spawn and die shortly afterwards. The 

migration of salmon upstream to spawn and die createas a carass-loading event in a small geographic area. 

Recent literature has suggested that spawning salmon are a potential contaminant biovector (Behnke 2010).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?
449

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There is no evidence showing Chum Salmon causes infrastructure damage.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There is no evidence that Chum Salmon negatively affect water quality for human use.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There is no evidence that Chum Salmon negatively affect any markets or economic sectors. 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 No significant research indicates Chum Salmon are associated with frequent water closures, equipment 

damage, or a decline of recreational species. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U
450

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 In Southeast Alaska, Chum Salmon are important to the commercial fishing industry. 

 Oncorhynchus keta quality deteriorates as it develops for spawning, and those that are ready to spawn are not 

often sold in the United States (Behnke 2010).

 In commercial fisheries, Oncorhynchus keta has a lower value than other salmon species such as Chinook, 

Coho, or Sockeye salmon due to its low fat content and pale pink flesh that are not preferable to consumers 

(Behnke 2010). 
451

 Oncorhynchus keta is usually caught from commercial fisheries to be canned. It is sometimes sold fresh or 

frozen under the name of “Silver Bryte Salmon” (Behnke 2010).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6 √

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0

Unknown U

 Chum Salmon support many fisheries in the Puget Sound area. These include sport, commercial (all-citizen), 

and tribal fisheries. Recreational fisheries exist when mature adults return from the Strait of Juan de Fuca 

through Puget Sound and Hood Canal to their stream of origin. Commercial and tribal fisheries use purse seine 

or gillnets in open areas (WDFW 2012).

 Natives in Canada and Alaska dry and smoke these fish to feed to their dogs (Behnke 2010).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 
452

Beneficial Effect Total 12

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
453

Scientific Name: Osmerus eperlanus

Linnaeus, 1758

Common Name: European Smelt

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Osmerus eperlanus has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Osmerlus eperlanus lives and spawns in the Elbe River (Thiel and Potter 2001), which is an extremely 

busy shipping route. In the Netherlands, Osmerus eperlanus larvae survive transport in water pumped 

from Lake llsselImeer to the Frisian lake district to maintain a constant water level for agricultural 

purposes (Lammens et al. 1985). There was found to be 80% survival of O. eperlanus after intake of a 

cooler water inflow to a power plant through a screen system (Rohlwing et al. 1998). Thus this species is 

considered likely to survive transport in a ballast tank.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
454

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical,

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1
455

This species is widely popular, and although trade, sale, and/or possession of this species

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes Score x 0.75
456

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 In the Netherlands, O. eperlanus larvae survive transport in water pumped from Lake llsselImeer to the Frisian 

lake district to maintain a constant water level for agricultural purposes (Lammens et al. 1985).

 There was found to be 80% survival of O. eperlanus after intake of a cooler water inflow to a power plant 

through a screen system (Rohlwing et al. 1998).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Osmerlus eperlanus lives and spawns in the Elbe River (Thiel and Potter 2001), which is an extremely busy 

shipping route.

 Its native range includes coastal waters and estuaries from southern Norway, around the western coast of 

Europe (including the Baltic Sea), to north-western Spain (Jakob et al. 2010).
457

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
458

Osmerus eperlanus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Osmerus eperlanus lives in large lakes in Finland, Sweden, Norway, Denmark, Poland and Russia 

(Nellbring 1989) with conditions similar to the more oligotrophic of the Great Lakes. Scandinavian lakes 

would have similar temperature regimes as the Great Lakes. Congeneric species (Osmerus mordax) have 

already been introduced into the Great Lakes and spread throughout the region (Nellbring 1989). This 

indicates (though does not guarantee), the suitability of the Great Lakes for this species' survival and 

spread. Osmerus eperlanus are tolerant of a wide salinity range; several purely freshwater populations 

occur (Jakob et al. 2010). Osmerus eperlanus are opportunistic feeders, likely to readily find sufficient 

food in the Great Lakes. This species has a relatively high rate of hermaphroditism and can be self-fertile.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 O. eperlanus is tolerant of a wide salinity range; several purely freshwater populations occur (Jakob et al. 

2010).

 Osmerus eperlanus does particularly well in pelagic areas of oligotrophic lakes (Jurvelius et al. 2005).

 O. eperlanus is a coldwater species that does not tolerate surface water temperatures over 20°C for long 

periods (~80 days) (Kangur et al. 2007b). However, this species is able to migrate to deeper, cooler waters 

during the summer (Power and Attrill 2007).

 O. eperlanus is sensitive to cyanobacteria blooms (Kangur et al. 2007b).

 This species does not tolerate low oxygen (<2 mg O2/l) in warm water temperatures (Kangur et al. 2007b), low 

growth at <4.5 mg O2/l (Sepulveda 1994) .

 O. eperlanus does less well in eutrophic waters, in part because associated siltation may lead to inconsistent 

recruitment of fish through spawning grounds (Kangur et al. 2007, Winfield et al. 1996).

 O. eperlanus can inhabit turbid river stretches (Lyle and Maitland 1997), and has been the dominant catch 

(91.8-100%) in eutrophic and turbid lakes in Finland (Peltonen et al. 2006, Reckel et al. 2003).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9
459

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Osmerus eperlanus lives in large lakes in Finland, Sweden, Norway, Denmark, Poland and Russia (Nellbring 

1989).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 An opportunistic feeding ecology, O. eperlanus consumes copepods and cladocerans (Northcote and Hammar 

2006).

 With increasing size and age, its food changes to larger crustaceans and in some cases to fish (Nilsson 1979,

Svärdson et al. 1988). According to Sterligova (1979) European Smelt also eats Vendace, Whitefish larvae and 

fry (Jurvelius et al. 2005).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 Jurvelius et al. (2005) did a study of O. eperlanus in 5 Finnish lakes: In four lakes the proportion of European 

Smelt was more than 60%.

 Young O. eperlanus are efficient planktivorous fish that affect the size structure of the zooplankton community 

easily by their size selective predation (van Densen 1985). When the density of smelt is very high, the 
460

depression of the average size of D. hyalina is so drastic that these food organisms can no longer be retained by 

the gill rakers of mature bream (Lammens et al. 1985), which has to switch to a benthivorous diet (Lammens et 

al. 1985).

 O. eperlanus can reach very high densities (Northcote and Hammar 2006).

 Evidence from congeneric species: In the Great Lakes, Rainbow Smelt Osmerus eperlanus compete with Lake 

Herring Coregonus artedii for food (Becker 1983). Christie (1974) supplied some evidence to support this, 

correlating Lake Herring decline with Rainbpw Smelt increases in most of the lakes. Todd (1986) also reported 

that Smelt may be partially responsible for the decline of Whitefish Coregonus spp. in the Great Lakes. Hrabik 

et al. (1998) found evidence of competition for food between introduced Rainbow Smelt and native Yellow 

Perch Perca flavescens in Wisconsin lake habitats (Fusaro et al. 2015).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

7

 Relative fecundity of O. eperlanus ranged 980-1718 eggs/g female (Nellbring 1989).

 Relative fecundity of O. mordax ranged 380-656 eggs/g female (Nellbring 1989).

 Relative fecundity of O. dentex ranged 491-1063 eggs/g female (Nellbring 1989).

 Relative fecundity of Surf Smelt Hypomesus pretiosus average 556.5 eggs/g female (Therriault and Hay 2003).

 O. eperlanus is highly fecund with a mean fecundity of 56,603 eggs/female (Hutchinson and Mills 1987). 

Fecundity is also estimated at 30,360 eggs/female, with average weight of fish 116.35 (Maitland and Lyle 

2010).

 Maximum fecundity of Pond Smelt Hypomesus olidus was 2523 eggs/female, with maximum weight 50 g 

(Degraaf 1986).

 Review of Landlocked Smelt maximum fecundity (eggs/fish) revealed (Chigbu and Sibley 1994):

o O. eperlanus: 4100-20000.

o O . mordax: 5500-40900.

o Spirinchus thaleichthys: 535-22210.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3
461

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 O. eperlanus exhibits relatively high rates of hermaphroditism: 2.6% of fish from the Elbe were hermaphroditic, 

and capable of self-fertilization, with other reports at 3.7% (Hutchinson 1983).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Lives in large lakes in Finland, Sweden, Norway, Denmark, Poland and Russia (Nellbring 1989).

 Congeneric species (Osmerus mordax) have already been introduced into the Great Lakes and spread 

throughout the region (Nellbring 1989). This indicates (though does not guarantee), the suitability of the Great 

Lakes for this species' survival and spread. 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 This species lives in pristine, oligotrophic habitats (Scandinavian inland lakes) as well as heavily-polluted 

habitats (lower Elbe River), though may have health issues (e.g., granulomas and physical deformities) in more 

polluted areas (Anders and Möller 1987, Pohl 1990).

 Scandinavian lakes would have similar temperature regimes as the Great Lakes.

 Congeneric species (Osmerus mordax) has already been introduced into the Great Lakes and spread 

throughout the region (Nellbring 1989). This indicates (though does not guarantee), the suitability of the Great 

Lakes for this species' survival and spread. 
462

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Osmerus eperlanus can inhabit freshwater lakes and rivers (Lyle and Maitland 1997, Nellbring 1989).

 This species does particularly well in pelagic areas of oligotrophic lakes (Jurvelius et al. 2005).

 O. eperlanus Inhabits pelagic zone; catches of smelt peak at 22-25 m depth (Northcote and Hammar 2006).

 O. eperlanus has been observed to feed at 7-9 m in a Finnish lake (Reckel et al. 2003).

 O. eperlanus uses warmer environments for larval development, and migrate to colder areas for 

growth/maturation (Power and Attrill 2007).

 Congeneric species (Osmerus mordax) has already been introduced into the Great Lakes and spread 

throughout the region (Nellbring 1989). This indicates (though does not guarantee), the suitability of habitat in 

the Great Lakes for this species' survival and spread. 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

0

 This species does poorly in surface water temperatures above 20°C, so would not likely benefit from increased 

water temperatures (Kangur et al. 2007b).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

6
463

moderate)

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 During its first summer O. eperlanus initially eats rotifers, copepods and successively larger zooplanktons 

(Nellbring 1989). With increasing size and age, its food changes to larger crustaceans and in some cases to fish 

(Nilsson 1979, Svӓrdson et al. 1988). According to Sterligova (1979) smelt also eats vendace, whitefish larvae 

and fry (Jurvelius et al. 2005).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

6
464

and spread in the Great Lakes)

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-20%

 Smelt is an important food item for predatory fish species like Pike-perch, Brown Trout and Landlocked Salmon 

(Heikinheimo et al. 2002, Keskinen and Marjomäki 2004, Jurvelius et al. 2005, Peltonen et al. 1996).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 Uptake and survival in ballast after exchange would lead to low densities of inocula.
465

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

1

 The native range of O. eperlanus is coastal waters and estuaries from southern Norway, around the western 

coast of Europe (including the Baltic Sea) to north-western Spain (Jakob et al. 2010). It has been introduced 

into several Scandinavian lakes, but not elsewhere.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

1

 This species has not been reported to spread from the landlocked lakes into which it has been introduced. 

However, the congeneric species O. mordax has spread extensively throughout the Great Lakes (Fusaro et al. 

2015). 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are -20% total 
466

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 78

>100 High Adjustments

B. Critical species A*(1- 0%) 78

51-99 Moderate C. Natural enemy B*(1- 20%) 62.4

Control measures C*(1- 0%) 62.4

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Unknown

Beneficial: Moderate

Osmerus eperlanus has the potential for high environmental impact if introduced to the Great 

Lakes.

In the Great Lakes, congeneric Rainbow Smelt, Osmerus mordax, compete with Lake Herring, Coregonus 

artedii, for food (Becker 1983). Christie (1974) supplied some evidence to support this, correlating Lake 

Herring decline with Smelt increases in most of the lakes. Todd (1986) also reported that Smelt may be 

partially responsible for the decline of Whitefish Coregonus spp. in the Great Lakes. Hrabik et al. (1998) 
467

found evidence of competition for food between introduced Rainbow Smelt and native Yellow Perch 

(Perca flavescens) in Wisconsin lake habitats (Fusaro et al. 2015).

Osmerus eperlanus was accidentally introduced (in or before 1968) into the ecosystem of the Syamozero 

lake in Karelia (north-western Russia). The population of this species has reached a high density and 

caused serious changes in the structure and trophic relationships of the fish community of the Syamozero 

ecosystem (Ieshko et al. 2000). Unfortunately, this article is in Russian and has not been translated apart 

from the abstract.

The resource partitioning of the Bream (Abramis brama) and Eel (Anguilla anguilla) populations in Lake 

Tjeukemeer, The Netherlands, was related to the variation in abundance of their most important food 

organisms, Daphnia hyalina and larval chironomids (Lammens et al. 1985). Niche shifts of both bream 

and eel populations were related to the abundance of young planktivorous fish, particularly Smelt 

(Osmerus eperlanus). When these fish were abundant the D. hyalina population was dominated by small 

individuals and bream switched from a planktivorous to a benthivorous diet, the condition of mature 

bream deteriorated, and its gonads developed poorly (Lammens et al. 1985). Under these circumstances 

the eel population switched from a diet of chironomid pupae and molluscs to one of predominantly fish. 

The condition of Eels smaller than 35 cm decreased and the chironomid population decreased in numbers 

and biomass (Lammens et al. 1985). Thus O. eperlanus has the potential to disrupt respource partitioning 

among native species and its introduction may have consequences for native populations of American Eel 

(Anguilla rostrata). Osmerus eperlanus is a paratenic host for the parasitic nematode, Anguillicola 

crassus (causing swimbladder lesions); in Europe, Osmerus eperlanus transmits the parasite when preyed 

upon by eels (Haenen et al. 1994).

Current research on the potential for socio-economic impacts to result from Osmerus eperlanus if 

introduced to the Great Lakes is inadequate to support proper assessment.

Osmerus eperlanus is the most important fish intermediate/transport host of the 

sealworm Pseudoterranova dedpiens in the Elbe estuary and probably also in adjacent coastal waters of 

the Wadden Sea (Rohlwing et al. 1998, Karl 2006). Sealworms are potentially capable of causing 

anisakiasis-like symptoms in humans (e.g. abdominal pain, nausea, fever) when consumed in lightly 

cooked or raw fish products (pseudoterranovosisi; Audicana and Kennedy 2008, Margolis 1977, 

McClelland 2002, Rae 1963, Yu et al. 2001). However, this parasite requires seals to complete its life 

cycle (Kuhn et al. 2013).

Osmerus eperlanus has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

The commercial value of Smelt is low in Finnish lakes (Jurvelius et al. 2005). Smelt is an important food 

item for predatory fish species like Pike-perch, Brown Trout and Landlocked Salmon (Heikinheimo et al. 

2002, Jurvelius et al. 2005, Keskinen and Marjomäki 2004, Peltonen et al. 1996). Evidence from 

congeneric species: Havey (1973) reported increased growth of landlocked Atlantic Salmon following the 

introduction of Smelt as a forage species in a lake in Maine (Fusaro et al. 2015).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.
468

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 O. eperlanus is a paratenic host for the parasitic nematode, Anguillicola crassus (causing swimbladder lesions); 

in Europe, transmits the parasite when preyed upon by eels (Haenen et al. 1994).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 The resource partitioning of the Bream (Abramis brama) and Eel (Anguilla anguilla) populations in Lake 

Tjeukemeer, The Netherlands, was related to the variation in abundance of their most important food 

organisms, Daphnia hyalina and larval chironomids (Lammens et al. 1985). Niche shifts of both bream and eel 

populations were related to the abundance of young planktivorous fish, particularly Smelt (Osmerus eperlanus). 

When these fish were abundant the D. hyalina population was dominated by small individuals and bream 

switched from a planktivorous to a benthivorous diet, the condition of mature bream deteriorated, and its 

gonads developed poorly (Lammens et al. 1985). Under these circumstances the eel population switched from a 

diet of chironomid pupae and molluscs to one of predominantly fish. The condition of eels smaller than 35 cm 

decreased and the chironomid population decreased in numbers and biomass (Lammens et al. 1985).

 Evidence from congeneric species: In the Great Lakes, rainbow smelt Osmerus eperlanus compete with Lake 

Herring Coregonus artedii for food (Becker 1983). Christie (1974) supplied some evidence to support this, 

correlating Lake Herring decline with Smelt increases in most of the lakes. Todd (1986) also reported that smelt 

may be partially responsible for the decline of Whitefish Coregonus spp. in the Great Lakes. Hrabik et al. 

(1998) found evidence of competition for food between introduced Rainbow Smelt and native Yellow Perch 

Perca flavescens in Wisconsin lake habitats (Fusaro et al. 2015).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

1 
469

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U 

 The European Smelt Osmerus eperlanus was accidentally introduced (in or before 1968) into the ecosystem of 

the Syamozero lake in Karelia (north-western Russia). The population of this species has reached a high density 

and caused serious changes in the structure and trophic relationships of the fish community of the Syamozero 

ecosystem (Ieshko et al. 2000). 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U
470

Environmental Impact Total 7

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 Osmerus eperlanus is the most important fish intermediate/transport host of the Sealworm Pseudoterranova

dedpiens in the Elbe estuary and probably also in adjacent coastal waters of the Wadden Sea (Karl 2006, 

Rohlwing et al. 1998). Sealworms are potentially capable of causing anisakiasis-like symptoms in humans (e.g. 

abdominal pain, nausea, fever) when consumed in lightly cooked or raw fish products (pseudoterranovosisi)

(Audicana and Kennedy 2008, Margolis 1977, McClelland 2002, Rae 1963, Yu et al. 2001). However, this 

parasite requires seals to complete its life cycle (Kuhn et al. 2013).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U
471

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U √

 O. eperlanus carries the herpesvirus of Osmerus eperlanus (HVOE1) or Comet herpesvirus of Smelt. In fish 

farming other herpesviruses are known to cause economic losses (Jakob et al. 2010).

 Osmerus eperlanus is the most important fish intermediate/transport host of the Sealworm Pseudoterranova

dedpiens in the Elbe estuary and probably also in adjacent coastal waters of the Wadden Sea (Karl 2006, 

Rohlwing et al. 1998). This leads to commercial losses for the seafood processing industry, due to the presence 

of these worms in the fillets of many important food fishes (e.g. Gadus morhua, Pollachius virens, Hippog jossus

sp.) (Kuhn et al. 2013).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
472

Socio-Economic Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 The commercial value of Smelt is low in Finnish lakes (Jurvelius et al. 2005).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6
473

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 The recreational value of Smelt is low in Finnish lakes (Jurvelius et al. 2005).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 

 Smelt is an important food item for predatory fish species like Pike-perch, Brown Trout and Landlocked Salmon 

(Heikinheimo et al. 2002, Jurvelius et al. 2005, Keskinen and Marjomäki 2004, Peltonen et al. 1996).

 Evidence from congeneric species: Havey (1973) reported increased growth of landlocked Atlantic Salmon

following the introduction of Smelt as a forage species in a lake in Maine (Fusaro et al. 2015).

Beneficial Effect Total 3

Scoring

Score # U Impact
474

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
475

Scientific Name: Perca fluviatilis 

Linnaeus, 1758

Common Name: European Perch, Eurasian Perch, River Perch, Redfin Perch

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Perca fluviatilis has a moderate probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Models developed by Kolar and Lodge (2002) predict that Perca fluviatilis will be introduced to the Great 

Lakes from the Ponto-Caspian basin by transoceanic shipping. Perca fluviatilis may be taken up by 

ballast water and survive in ballast tank environments. This species occurs in waters that have direct trade 

connections with the Great Lakes, such as the Baltic Sea (Ložys 2004, NBIC 2009). It is considered a 

eurythermal fish and can tolerate temperatures between 8-27°C, but becomes stressed between 23-26°C 

(Lehtonen 1996). However, Perca fluviatilis cannot tolerate high salinities, so its survival in ballast tanks 

environments may be limited. It can inhabit brackish waters of the Aral and Baltic Sea, up to salinities of 

10 ppt (Ložys 2004), and can survive salinities of 13 ppt at water temperatures of 12-15°C. Larvae cannot 

tolerate salinities greater than 9.6 ppt (Lehtonen 1996). Ballast water exchange regulations requiring 

flushing with full strength sea water of 35 ppt may substantially limit the introduction of Perca fluviatilis 

to the Great Lakes. Perca fluviatilis may be introduced to the Great Lakes via ships declaring “No Ballast 

on Board” (NOBOB), which are exempt from ballast water exchange. The majority of ships entering the 

Great Lakes are NOBOB vessels and 43% of these ships contain residual water with less than 10 ppt 

salinity (Johengen et al. 2005). In the study, the temperature of the residual water from the vessels 

sampled ranged from -0.7 to 23.9°C; thus Perca fluviatilis is likely to survive the salinity and temperature 

of the NOBOB ballast water on some vessels.
476

As a prized freshwater angling species, Perca fluviatilis has been introduced to a number of countries 

(GISD 2012). USEPA (2008) suggests that there is a high risk that Perca fluviatilis will be introduced to 

the Great Lakes region as a sport fish. Perca fluviatilis does not currently occur near waters connected to 

the Great Lakes basin. It is not known to hitchhike on ships or recreational gear. It is not stocked, 

cultured, or sold in the Great Lakes region. It may survive several hours out of water if packed in dry 

straw (Pinnock 1820). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, 

including connecting channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Eurasian Perch occur naturally in still or slow-moving waters throughout the Northern Hemisphere. This 

species has spread widely throughout North and South Islands of New Zealand, Australia, and Asia (Closs et al. 

2011).

 Its native range extends throughout Europe (GISD 2012).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Eurasian Perch is not recorded as a species that may be transported by fouling or hitchhiking.
477

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Live Eurasian Perch is not available for sale in North American or through online retailers.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Eurasian Perch may be stocked as a sport fish in some locations (GISD 2012), it was stocked in Tasmania 

in 1862 and Victoria in 1868 as a sport and table fish (Arthington and McKenzie 1997).

 Eurasian Perch is a popular sport fish with some anglers because of its fighting qualities and taste (NSW 

DPI 2012a).
478

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 This species has not been reported from the United States (USFWS 2014c). 

 Large perch (over 250 grams) are processed by several companies in Finland, but the domestic market for 

small perch seems to be minor. Small perch are mainly used as raw material for traditional Finnish fish 

pasty, kalakukko, in eastern Finland (Setӓlӓ et al. 1996).

 In fisheries this species is highly commercial, used for aquaculture, commercially, and for gamefish

(Froese and Pauly 2015).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING
479

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 The Redfin Perch was identified as being at high risk of introduction to the Great Lakes though ballast 

water transported from the Ponto-Caspian basin (Kolar and Lodge 2002).

 It is not euryhaline. Adults can tolerate salinities up to 10 ppt, and larvae can tolerate salinities up to 9.6 

ppt (Lehtonen 1996, Ložys 2004). They occur in relatively warm waters that reach about 22°C. Perch 

growth rate increases with increasing temperature. 

 It can tolerate water temperatures between 8-27°C, but become stressed at temperatures of 23-26°C 

(Lehtonen 1996). 

 Balast water exchange regulations requiring flushing with full strength sea water of 35 ppt may 

substantially limit the introduction of Perca fluviatilis to the Great Lakes. 

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0 

Unknown U

 This species is found throughout Europe to the northernmost extremity of Scandinavia, except the Iberian 

Peninsula, central Italy, and Adriatic basin. It is also found in the Aegean Sea basin in Matriza and from 

Struma to Aliakmon drainages, Aral Sea basin, and in Siberia in rivers draining the Arctic Ocean eastward 

to Kolyma (Papasissi 2013).

 Introduced to Australia, China, Cyprus, Italy, Morocco, New Zealand, Spain and South Africa (Papasissi

2013). The species is not a true native of Ireland (although it was introduced 100s of years ago) and it is still 

absent from parts of Scotland. (GISD 2012).

 This species occurs in the Baltic Sea, off the coast of Lithuania (Ložys 2004). 
480

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Perca fluviatilis has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Perca fluviatilis occurs in Australia, which has a similar climate to most of the US, except for the Desert 

Southwest (USFWS 2014c). Perca fluviatilis has a somewhat broad physiological tolerance. It is 

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
481

considered a eurythermal fish and can tolerate temperatures between 4-31°C (Toner and Rougeot 2008). 

It can tolerate dissolved oxygen levels of 1.3-13.5 mg/L (Toner and Rougeot 2008) and salinities up to 10 

ppt (Ložys 2004). Perca fluviatilis is likely able to overwinter in the Great Lakes. This species is known 

to overwinter in Lake Constance, Germany, at temperatures between 4°-6°C, but may experience 

depletion of lipid reserves and post-spawning mortality as a result of overwintering (Eckmann 2004). 

Perca fluviatilis requires clear waters with a considerable level of light penetration to forage effectively 

(Granqvist and Mattila 2004). High nutrient levels and turbidity may be detrimental to the growth and 

survival of this species. It is predicted by Lehtonen (1996) that increased temperatures due to climate 

change will result in Perca fluviatilis spawning later in autumn and hatching earlier. In addition, it is 

expected that larvae will be smaller and will be more vulnerable to possible predators. Juveniles are 

predicted to grow to a larger size after their first summer due to warmer water temperatures.

Perca fluviatilis is carnivorous and feeds on a wide variety of foods including insect larvae, crustaceans, 

and small fish (Toner and Rougeot 2008). Larvae feed on algae and zooplankton. It is likely that this 

species will find an appropriate food source in the Great Lakes. In its native range, Perca fluviatilis 

exhibits intraspecific competition for food with the invasive Ruffe, Gymnocephalus cernua (L.)

(Eckmann 2004, Schleuter 2007) which also occurs as a nonnative in the Great Lakes. Both species are 

benthic feeders at some point of their development and both inhabit the littoral zone. Perca fluviatilis is a 

visually oriented predator and competition favors it in ogliotrophic conditions. On the other hand, the 

Ruffe is favored in more eutrophic conditions and can feed in turbid environments. When Ruffe is the 

superior competitor, there is a decline in the growth and yields of Perca fluviatilis. 

Perca fluviatilis reproduces once a year, from March to June (Toner and Rougeot 2008). The juveniles 

require at least 160 days in water temperatures under 8°C to mature. The juveniles reach maturity at 2-3 

years. Relative fecundity averages at 102,000 eggs/kg of body weight. A similar species, Perca 

flavascens, has a relative fecundity that ranges from 79,000-223,000 eggs/kg (Sheri and Power 1969). 

Kolar and Lodge (2002) developed models that predicted that Perca fluviatilis has a high risk for 

establishment, will spread quickly, and will be a nuisance in the Great Lakes. Perca fluviatilis has been 

introduced to several countries including Australia, South Africa, China, Cyprus, Ireland, Italy, Morocco, 

New Zealand, Spain, and South Africa for its reputation as an angling species (Welcomme 1988). Perca 

fluviatilis growth is stunted in some waters in Cyprus (Welcomme 1988). In New Zealand, it is 

reproducing artificially (Welcomme 1988). The introduction of Perca fluviatilis to South Africa is 

considered marginally successful (Welcomme 1988).

In Australia, P. fluviatilis tends to outcompete native species (Welcomme 1988). Perca fluviatilis is a 

potential competitor with other fish that feed on invertebrates and small fish including Great Lakes native 

fish, such as brook trout, lake whitefish, and bluegill (Thorpe 1977). New South Wales, Australia 

considers Perca fluviatilis a noxious fish due to their ability to eliminate other fish species and for their 

negative impacts on recreational fisheries (NSW DPI 2012a).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9
482

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 European Perch are widespread in the Baltic Sea and tolerate salinities up to 7–10 psu (Privolnev 1970, Lutz

1972).

 European Perch tolerate a wide range of temperatures (4-31°C). The optimal temperature for growth is 23°C.

(Toner and Rougeot 2008)

 European Perch tolerate a wide range of environments, but prefer shallow and moderately productive 

freshwaters (Toner and Rougeot 2008).

 European Perch populations in Danish lakes have been negatively affected by eutrophication, with both 

reduced total perch biomass and average body weight as indicators of reduced growth (Jeppesen et al. 2000). 

 European Perch survive in a pH range: 7.0 to 7.5 (Froese and Pauly 2015). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

5

 European Perch tolerate a wide range of temperatures (4-31°C). The optimal temperature for growth is 23°C

(Toner and Rougeot 2008).

 Redfin Perch overwinters in the profundal zone at temperatures below 6 ̊C in Lake Constance, Germany, but 

experiences depletion of its lipid reserves and high mortality following spring spawning (Eckmann 2004).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Redfin Perch is carnivorous and feeds on a wide variety of foods ranging from small invertebrates (such as 

crustaceans, worms, molluscs and insect larvae) to fish (NSW DPI 2012a). 
483

 Larvae and small juveniles usually feed on planktonic invertebrates. During first summer, many juveniles move 

near shores to feed on benthic prey (Froese and Pauly 2015). 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6

 In large numbers, Redfin Perch can out-compete most other fish species (NSW DPI 2012a).

 In Australia, P. fluviatilis tends to outcompete native species (Welcomme 1988).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 The absolute fecundity (number of eggs per female) in perch ranges from 15,000 to 300,000 eggs under 

natural conditions. During artificial spawning, average absolute and relative fecundity (number of eggs 

per kg of body weight) was around 40,000 eggs per female and 102,000 eggs per kg of body weight (Toner 

and Rougeot 2008). 

 European Perch have adapted well to New Zealand’s environment, possessing high fecundity and flexibility 

in behavior and habitat requirements (Hutchison and Armstrong 1993). 

 Similar species, P. flavascens, has a relative fecundity that ranges from 79-223 eggs/g which is equivalent 

to 79,000-233,000 eggs/kg (Sheri and Power 1969).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?
484

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 The climate match (USFWS 2014c) was high to medium for the entire United States low matches only occurred 

in the Desert Southwest. Climate six match indicated that the United States has a high climate match. The range 

for a high climate match is 0.103 and greater, climate match of P. fluviatilis is 0.627 (USFWS 2014c). 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 Perch populations in Danish lakes have been negatively affected by eutrophication, with both reduced total 

perch biomass and average body weight as indicators of reduced growth (Jeppesen et al. 2000). 
485

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 This species inhabits a very wide range of habitats from estuarine lagoons, lakes of all types to medium- sized 

streams. Feeding larvae occur in open water (Froese and Pauly 2015). 

 European Perch tolerate a wide range of environments, but prefer shallow and moderately productive 

freshwaters. This is a freshwater species, but because of its euryhaline tolerance, perch is also present in 

brackish water in the Baltic Sea. Perch prefer lentic river conditions (with a low flow rate) and are also present 

in deep lakes, up to 40m in depth (Toner and Rougeot 2008).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 European Perch tolerate a wide range of temperatures (4-31°C). The optimal temperature for growth is 

23°C (Toner and Rougeot 2008).

 European Perch tolerate a wide range of environments, but prefer shallow and moderately productive 

freshwaters (Toner and Rougeot 2008).

 European Perch are widespread in the Baltic Sea and tolerate salinities up to 7–10 psu (Privolnev 1970, 

Lutz 1972).

 It is predicted by Lehtonen (1996) that increased temperatures due to climate change will result in Perca 

fluviatilis spawning later in autumn and hatching earlier. In addition, it is expected that larvae will be 

smaller and will be more vulnerable to possible predators. Juveniles are predicted to grow to a larger size 

after their first summer due to warmer water temperatures.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?
486

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Redfin Perch are carnivorous and feed on a wide variety of foods ranging from small invertebrates (such as 

crustaceans, worms, molluscs and insect larvae) to fish (NSW DPI 2012a). 

 Larvae and small juveniles usually feed on planktonic invertebrates. During first summer, many juveniles move 

near shores to feed on benthic prey (Froese and Pauly 2015). 

 In general the smallest perch feed upon plankton Crustacea, the middle-sized ones upon insect larvae and other 

bottom-living forms, while the largest perch feed chiefly on small fish (Allen 1935). 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 The Redfin Perch has no required species.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?
487

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is no introduced species in the Great Lakes known to facilitate redfin perch establishment.

 Gymnocephalus cernua is established in the Great Lakes and competes with Perca fluviatilis where they occur 

sympatrically (Erkmann 2004, Schleuter 2007). 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 The Redfin Perch is unlikely to be preferentially targeted as the prey of Great Lakes species.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9
488

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Its native range is throughout much of Europe, but it has been introduced to a number of countries around the 

world as a sport fish (GISD 2012).

 Perca fluviatilis is introduced to Australia, China, Cyprus, Italy, Morocco, New Zealand, Spain and South 

Africa (Papasissi 2013). The species is not a true native of Ireland (although it was introduced hundreds of 

years ago) and it is still absent from parts of Scotland (USFWS 2014c). 

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

8

 Redfin was recorded as eliminating 20,000 newly released Rainbow Trout fry from a reservoir in south-western 

Australia in less than 72 hours. Redfin are capable of rapidly populating new waterways and in stable water 

bodies (such as lakes and dams) they can form very dense populations (NSW DPI 2012a). 

 Kolar and Lodge (2002) developed models that predicted that Perca fluviatilis has a high risk for establishment, 

will spread quickly, and will be a nuisance in the Great Lakes.
489

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 95

>100 High Adjustments

B. Critical species A*(1- 0%) 95

51-99 Moderate C. Natural enemy B*(1- 0%) 95

Control measures C*(1- 0%) 95

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Moderate
490

Beneficial: High

Perca fluviatilis has the potential for high environmental impact if introduced to the Great Lakes.

Perca fluviatilis is a carrier of the epizootic haematopoeitic necrosis (EHN) virus. In Australia, the EHN 

virus carried by Perca fluviatilis may have resulted in declines of the native Macquarie Perch, Silver 

Perch, Murray Cod, and Mountain Galaxias (Lintermans 1991, NSW DPI 2012a).

Perca fluviatilis can potentially compete with native species for zooplankton, macroinvertebrates, and fish 

(Closs et al. 2003). Perca fluviatilis is said to compete for food and space with the Murray Cod 

(Maccullochella peelii peelii) and Golden Perch (Macquaria ambigua) (Lintermans et al. 1990). In New 

Zealand, Perca fluviatilis suppressed populations of a native fish, the Common Bully, by direct predation 

(Closs et al. 2003). Physical removal of Perca fluviatilis from ponds resulted in an increased abundance 

of the common bully. It has been suggested that Perca fluviatilis competition is responsible for the local 

extinction of the rare Mud Minnow, Galaxiella munda (USFWS 2014c). It has been reported that Perca 

fluviatilis preyed on native Pygmy Perch (Edlia vittata) in Australia, negatively impacting their 

populations (Arthington and McKenzie 1997). It is suspected that Perca fluviatilis negatively affects 

native fish populations by preying on vulnerable Ewen’s Pygmy Perch, Nanoperca variegata, vulnerable 

Yarra Pygmy Perch, Edelia obscura, the vulnerable Dwarf Galaxia, Galaxias pusilla, and juveniles of

Macquarie Perch, Macquaria australasica (Wager and Jackson 1993).

It is unknown if Perca fluviatilis affects native populations genetically, water quality, or the physical 

components of the ecosystem. 

Perca fluviatilis has the potential for moderate socio-economic impact if introduced to the Great 

Lakes. 

Perca fluviatilis may prey on native species and trout, negatively affecting recreational fisheries. Within a 

72-hour period, Perca fluviatilis eliminated 20,000 newly released Rainbow Trout fry from a reservoir in 

south-western Australia (NSW DPI 2012a). 

Perca fluviatilis has the potential for high beneficial impact if introduced to the Great Lakes.

Perca fluviatilis is valued as an important fish species for aquaculture, fisheries, and recreation (Setälä et 

al. 1996, Toner and Rougeot 2008, USFWS 2014c). This species is not known as a biological control 

agent, does not increase water quality, or have a positive ecological impact. It is not valuable for medical 

research. 

POTENTIAL ENVIRONMENTAL IMPACT

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 
491

Not significantly 0

Unknown U

 One of the most significant threats to native fish from Redfin is their potential to spread the viral disease 

Epizootic Haematopoietic Necrosis (EHN). This disease, which was first isolated in 1985 and is unique to 

Australia, can cause mass mortality in juvenile redfin perch during the summer months. A number of native 

species, including Silver Perch, Murray Cod, Mountain Galaxias and particularly Macquarie Perch, are highly 

susceptible to the disease, and EHN virus may be one factor responsible for the decline in various native 

species over the last couple of decades (NSW DPI 2012a).

 P.fluviatilis can destroy recreational fisheries in enclosed waters by building up large numbers of stunted fish 

and eliminating other species, and can devastate native fish populations by carrying the epizootic 

haematopoietic necrosis (EHN) virus (NSW DPI 2012a).

 In the Australian Capital Territory, mass mortality of juvenile perch has been attributed to EHN virus, and it is 

considered likely that this disease has been responsible for major declines in populations of Macquarie Perch 

in this region (Lintermans 1991). A chronic form of EHN virus with a lower mortality also occurs in farmed 

Rainbow Trout (Langdon and Humphrey 1987).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 In such large numbers, P.fluviatilis can also out-compete most other fish species (NSW DPI 2012a).

 Perca fluviatilis was introduced to Lake Bositen, Xinjiang in the 1970’s and caused the disappearance of 

endemic fish Asipiorhynchus laticeps from the lake. This species was introduced from the Ertrix River basin in 

the north Xiangjiang Autonomous Region to the Bosten Lake in the south Xiangjiang autonomous regions for 

fish resource enhancement purpose. It became a dominant fish in the new environment (Bartley 2006, Froese 

and Pauly 2015).

 This species has been implicated in the local extinction of the rare Mud Minnow, Galaxiella Munda, (Wager 

1996), as well as affecting the recruitment of a recreationally important decapod (Cherax cainii) (USFWS 

2014c). 

 Adverse interactions, in the form of food competition and possibly predation, by the redfin on the ‘endangered’ 

trout cod, Maccullochella macquariensis, are said to have contributed to the cod’s decline (Wager and Jackson 

1993).

 In New South Wales, the redfin is regarded as a significant predator on indigenous fishes, and juveniles 

probably compete with small planktivorous fishes for food (P. Gehrke, pers. comm., cited in Arthington and 

McKenzie 1997).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction 

of one or more native populations, creation of a dead end or any other significant 

alteration in the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

1 
492

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U 

 P.fluviatilis has been implicated in the local extinction of the rare Mud Minnow, Galaxiella munda (Wager 

1996).

 The Redfin is suspected of predation on the ‘vulnerable’ Ewen’s Pygmy Perch, Nannoperca variegata, and the 

‘vulnerable’ Yarra Pygmy Perch, Edelia obscura, the ‘vulnerable’ Dwarf Galaxias, Galaxias pusilla, and 

juveniles of the ‘poorly known’ Macquarie Perch, Macquaria australasica (Wager and Jackson 1993). Adverse 

interactions, in the form of food competition and possibly predation, by the Redfin on the ‘endangered’ trout 

cod, Maccullochella macquariensis, are said to have contributed to the cod’s decline (Wager and Jackson 

1993). 

 In New South Wales, the Redfin is regarded as a significant predator on indigenous fishes, and juveniles 

probably compete with small planktivorous fishes for food (P. Gehrke, pers. comm., as cited in Arthington and 

McKenzie 1997).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to 

the decline of one or more native species (or added pressure to threatened/endangered 

species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 The biggest threat would likely be to native perch, Perca flavescens, via competition and hybridization (USEPA 

2008).

 Perca flavescens is able to hybridize with introduced ruffe (Gymnocephalus cernua) (Crosier et al. 2007).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

6
493

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 In New South Wales, the Redfin Perch has not been linked with large-scale ecological degradation (P. Gehrke, 

pers. comm., as cited in Arthington and McKenzie 1997).

Environmental Impact Total 18

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6
494

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 Redfin Perch predation can seriously impact populations of native species, and can also affect recreational 

fisheries for these species. For example, Redfin was recorded as eliminating 20,000 newly released Rainbow 

Trout fry from a reservoir in south-western Australia in less than 72 hours (NPW DPI 2012). 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 Redfin Perch predation can seriously impact populations of native species, and can also affect recreational 

fisheries for these species. For example, Redfin was recorded as eliminating 20,000 newly released Rainbow 

Trout fry from a reservoir in south-western Australia in less than 72 hours (NPW DPI 2012). 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
495

Socio-Economic Impact Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 Perca flavescens is valuale for fisheries: highly commercial; aquaculture: commercial; and for gamefish

(Froese and Pauly 2015).

 The total catch of Redfin Perch in Finland was about 20,000 tonnes in 1992. 96 % of it was harvested by 

recreational fishermen, and 70% from inland waters. Only 2% (242 tonnes) of the total inland catches was 

harvested in the commercial fisheries (Karttunen 1994, Leinonen 1993, Tuunainen 1994). 

 Commercial inland fishing in Finland is mostly based on vendace (Coregonus albula L.). There are strong 

fluctuations in the vendace stocks. When the density of the stock is low, fishermen seek alternative species that 

could be profitably harvested. The main proportion of Redfin Perch is caught during the spawning season in 
496

May to June. During this period, perch may significantly contribute to the professional fishing, particularly 

since vendace catches are low in spring (Setӓlӓ et al. 1996).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6 √

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0

Unknown U

 The European Perch or Redfin, Perca fluviatilis, was introduced into Tasmania in 1862 and into Victoria in 

1868 as a sport and table fish (Arthington and McKenzie 1997).

 In fisheries this species is highly commercial, used for aquaculture, and as a gamefish (Froese and Pauly 

2015). 

 Perca flavescens is a popular sport fish with some anglers because of its fighting qualities and taste (NSW DPI 

2012a). 

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 
497

Not significantly 0 √

Unknown U 

Beneficial Effect Total 12

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
498

Scientific Name: Perccottus glenii

Dybowski, 1877

Common Name: Amur Sleeper

Synonyms: Chinese Sleeper, Rotan, Eleotris dybowskii (Herzenstein & Warpachowski, 1888), Eleotris

pleskei (Warpachowski, 1888), Perccottus glehni, Perccottus pleskei (Warpachowski, 1888)

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Perccottus glenii has a moderate probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Unauthorized Intetional Release,Transoceanic Shipping (ballast 

water)

Perccottus glenii does not currently occur near waters connected to the Great Lakes basin. This species is 

not known to hitchhike or foul recreational gear. Perccottus glenii is sold in Eurasia and was once a 

popular fish for aquariums and backyard ponds (Reshetnikov 2004). It is used as bait fish in Europe 

(Edgar and Bird 2005, Reshetnikov 2004). There is no evidence that this species can be obtained in North 

America to be released into the Great Lakes. Perccottus glenii is not cultured or stocked in the Great 

Lakes region. This species occurs in ports that have direct trade connections with the Great Lakes, such as 

those in the Baltic Sea (Koščo et al. 2003, NBIC 2009). One of the suggested pathways for the 

introduction of Perccottus glenii is ballast water (Ćaleta et al. 2010). Perccottus glenii can tolerate a 

broad range of temperatures (Golovanov and Ruchin 2011) and waters with low oxygen (Koščo et al. 

2008, Reshetnikov 2003). Its tolerance to high salinity is not fully known, but it is likely that ballast 

regulations will substantially impact the survival of Perccottus glenii.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
499

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Perccottus glenii first appeared outside of its native habitat, the Amur River basin, China (Koščo et al. 

2008) in Moscow in 1912. Since then, P. glenii has spread 100° East and West to Poland, Slovakia, 

Hungary, Bulgaria, Romania, Serbia, Croatia, Moldova and other countries (Reshetnikov 2012).

 There has been no mention of species ever being found in North America. 

 Perccottus glenii travels via connecting waters (Koščo et al. 2010)

 Long term ranges of P. glenii depend on climate variations however, as opposed to open borders 

(Reshetnikov and Ficetola 2011)

 No geographical barriers exist between the regions of Eastern Europe that have currently been inhabited 

and potential habitats in Western Europe (Reshetnikov 2012).

 Long term ranges will depend on climate variations however, as opposed to open borders (Reshetnikov and 

Ficetola 2011).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Perccottus glenii occasionally travels with stocking carp from fish farms in China to other parts of Europe, 

however there was no mention of any natural or anthropogenic products that resulted in a transfer to the 

Great Lakes region (Reshetnikov 2004).

 There has been no mention of species being found in North America. 

2b) What is the proximity of this species to the Great Lakes basin?
500

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

Perccottus glenii is sold in Eurasia and was at one point a popular fish for use in aquariums and backyard ponds 

(Reshetnikov 2004).

Perccottus glenii is often used as bait fish, including Europe (Edgar and Bird 2005, Reshetnikov 2004).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 There has been no record of P. glenii being sold in North America. 

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Perccottus glenii is sold in Eurasia and was at one point a popular fish for use in aquariums and backyard 

ponds in Russia (Reshetnikov 2004)

 Small introductions in Eurasia were attempted in an effort to reduce mosquito populations with no 

significant results (Koščo et al. 2003)
501

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 There has been no record of P. glenii being used to stock in North America 

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There has been no record of P. glenii being transported through the Great Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?
502

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 

Unknown U

 Perccottus glenii tolerates very low temperatures as well as relatively high temperatures, from lakes that 

nearly freeze solid to a maximum temperature of approximately 38.2-35.5°C (Golovanov and Ruchin 

2011).

 According to Ćaleta et al. (2010), ballast water is a possibility for introductions into new places, however 

has not been observed.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Perccottus glenii is found in the Gulf of Finland (Koščo et al. 2003) which has trade relations in the Great 

Lakes. 
503

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.1 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
504

Perccottus glenii has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

The native and introduced ranges have a similar climate to the Great Lakes region and Mountain West 

(USFWS 2014a). Perccottus glenii can tolerate a wide range of water temperatures (Golovanov and 

Ruchin 2011, Verreycken 2013). Several studies mention that this species can tolerate low dissolved 

oxygen levels (Ćaleta et al. 2010, Koščo et al. 2008, Reshetnikov 2003, Yang et al. 2012), but no specific 

ranges are reported. The optimal salinity for this species is 0-6 ppt (Golovanov and Ruchin 2011) and it 

inhabits fresh to brackish water (Froese and Pauly 2015). Perccottus glenii is also resistant to high water 

eutrophication (Koščo et al. 2003). Given its tolerances to a wide variety of environmental conditions, it 

is likely that this species can establish in the Great Lakes, especially in stagnant water bodies of a shallow 

depth. This species is known to overwinter under frozen bodies of water, and hibernates in mud 

(Golovanov and Ruchin 2011, Koščo et al. 2008, USFWS 2014a), thus it is likely that this species can 

overwinter in the Great Lakes. Perccottus glenii will likely adapt to the effects of climate change in the 

Great Lakes, including warmer water temperatures, shorter duration of ice cover, and increased 

salinization. 

Perccottus glenii feeds opportunistically, preying on animals at every trophic level, and is omnivorous 

(Koščo et al. 2008, Grabowska et al. 2009, Reshetnikov 2003). This species has the potential to compete 

with native species (Koščo et al. 2003, Orlova et al. 2006, Reshetnikov 2003). In addition, there are 

species in the Great Lakes region that may prey on Perccottus glenii such as perch and pike (Golovanov 

and Ruchin 2011), but little research has been conducted to investigate whether these predators will 

reduce this species’ probability of establishment. 

Its average fecundity ranges 7,766-9,149 per female, which increases with increasing size (Grabowska et 

al. 2011). The fecundity of Perccottus glenii is higher than that of native nest-guarders, but lower than 

fishes not exhibiting parental care. This species is characterized by early maturation and reproduction 

where it has been introduced, which may aid its establishment into new areas. Individual growth rates are 

higher in the Vistula River than in its native range (Grabowska et al. 2011). 

Historically, this species has established populations extensively outside of its native range. Its 

nonindigenous range includes western Russia (Grabowska et al. 2011, Reshetnikov 2003), Latvia 

(USFWS 2014a), Poland (Grabowska et al. 2011), Ukraine (Kutsokon et al. 2014, Kvach 2012), eastern 

Slovakia (Koščo et al. 2003), Hungary (Reshetnikov 2004), Romania (USFWS 2014a), Bulgaria (Jurajda 

et al. 2005), Serbia (Simonović et al. 2006), Croatia (Ćaleta et al. 2010), and Germany (Reshetnikov and 

Schliewen 2013).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6
505

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Perccottus glenii tolerates a wide range of conditions (Reshetnikov 2004).

 P. glenii has an extremely high tolerance to unfavorable conditions (Golovanov and Ruchin 2011). 

 P. glenii is very tolerant to high temperatures up to 38.2-35.5°C and is one of the most resistant fish to 

freezing (Golovanov and Ruchin 2011).

 Optimal conditions for P.glenii are in stagnant, muddy, littoral waters (Grabowska et al. 2011)

 P. glenii can withstand very low oxygen levels (Koščo et al. 2008), to 0.1 mg/L (Grabowska 2011).

 P. glenii lives in both fresh and brackish water (Froese and Pauly 2015).

 The optimal salinity for this species is 0-6 ppt (Golovanov and Ruchin 2011).

 It can tolerate temperatures as low as 1°C (Verreycken 2013) to as high as 35.8°C (Golovanov et al. 2013).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Perccottus glenii is one of the most resistant fish to freezing (Golovanov and Ruchin 2011).

 P. glenii burrows into the mud and hibernates if the water body is completely frozen or dried out (USFWS 

2014a).

 P. glenii can withstand very low oxygen levels (Koščo et al. 2008), to 0.1 mg/L (Grabowska 2011).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 The diet of P. glenii’s main diet is wide. The diet includes chironomid larvae, caddisflies, dragonflies, 

mollusks, tadpoles, juvenile fish, fish eggs, higher aquatic plants (Golovanov and Ruchin 2011). 

 This species is a non-selective opportunistic predator (Grabowska et al. 2009).

 This species is considered a switch predator (Grabowska et al. 2009). 
506

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6

 Perccottus glenii is able to dramatically decrease species diversity in some areas, occasionally completely 

ridding them of amphibian species (Reshetnikov and Ficetola 2011). 

 Highest growth rates are seen in places where the fish has been introduced as opposed to native ranges 

(Grabowska et al. 2011). 

 Perccottus glenii can very much affect population dynamics of aquatic ecosystems (Grabowska et al. 2009).

 Reshetnikov (2003) suggests that competition may be a factor in reducing the populations of fish and 

amphibians, but primarily attributes this to direct predation. 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Lower growth levels for older age classes have been reported for P. glenii (Grabowska et al. 2011); 

however, introduced populations have elevated fecundity (Welcomme 1988). 

 This species average fecundity ranges 7,766-9,149 per female, which increases with increasing size 

(Grabowska et al. 2011).

 Its fecundity is higher than that of native nest-guarders, but is lower than fishes no exhibiting parental care 

(Grabowska et al. 2011).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

9
507

based on these attributes)

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

5

 Perccottus glenii matures and reproduces early in life (Grabowska et al. 2011).

 Males protect the eggs and pelagic larvae (Kottelat and Freyhof 2007).

 The highest growth rates often occur right after introduction (Grabowska et al. 2011).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The climate of Western Europe is similar but not exact to that of the Great Lakes region.

 The USFWS’s Ecological Risk Screening Summary (2014a) predicted a high climate match throughout the 

Great Lakes. 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8
508

 Perccottus glenii invades a vast area, where a wide variety of abiotic factors are seen. Therefore, P. glenii

will probably be able to tolerate most of the Great Lakes conditions, not because they are optimal, but 

because its tolerance range is so large (Reshetnikov 2004).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Perccottus glenii is restricted to shallow waters, not usually found at depths deeper than 10m (Pronin and 

Bolonev 2006). 

 This species spreads best through lentic bodies of water (Golovanov and Ruchin 2011).

 P. glenii is found near coasts and in vegetation (Golovanov and Ruchin 2011). 

 P. glenii optimal conditions are stagnant muddy waters (Grabowska et al. 2009)

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Perccottus glenii has extreme tolerance to unfavorable conditions (Golovanov and Ruchin 2011). 

 This species is very tolerant to high temperatures up to 38.2-35.5°C and is one of the most resistant fish to 

freezing (Golovanov and Ruchin 2011).

 P. glenii can withstand very low oxygen levels (Koščo et al. 2008), to 0.1 mg/L (Grabowska 2011).

 P. glenii lives in both fresh and brackish water (Froese and Pauly 2015).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?
509

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Perccottus glenii’s main diet is wide. The diet includes chironomid larvae, caddisflies, dragonflies, 

mollusks, tadpoles, juvenile fish, fish eggs, and higher aquatic plants (Golovanov 2013). 

 The fish is a non-selective opportunistic predator (Grabowska et al. 2009).

 The fish is considered a switch predator (Grabowska et al. 2009). 

 Perccottus glenii feeds opportunistically, preying on animals at every trophic level, and is omnivorous 

(Koščo et al. 2008, Grabowska et al. 2009, Reshetnikov 2003).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No required critical species requirements were found in the research for this species. 

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 9
510

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 No species were found to likely aid in this species establishment or spread were found in the research. 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-5%

 Potential predators could possibly be perch and pike, but there is very little research on this possibility 

(Golovanov and Ruchin 2011). 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6
511

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Perccottus glenii has been able to spread over 100° East and West of its introduced region (Reshetnikov 

2012)

 A very high risk of future invasion within fitting climates exists in Europe (Reshetnikov and Ficetola 2011). 

 This species nonindigenous range includes western Russia (Grabowska et al. 2011, Reshetnikov 2003), 

Latvia (USFWS 2014a), Poland (Grabowska et al. 2011), Ukraine (Kutsokon et al. 2014, Kvach 2012), 

eastern Slovakia (Koščo et al. 2003), Hungary (Reshetnikov 2004), Romania (USFWS 2014a), Bulgaria 

(Jurajda et al. 2005), Serbia (Simonovic et al. 2006), Croatia (Ćaleta et al. 2010), and Germany 

(Reshetnikov and Schliewen 2013).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 Since 1912, P. glenii has been able to spread over 100° East and West of the introduction site to 15 

countries (Reshetnikov 2012).

 Considered as one of the most widespread (Reshetnikov 2010) and successful fish invaders in European 

inland waters of the last decades (Copp et al. 2005).
512

 The rate of the Amur Sleeper expansion is impressive - the rate of its expansion in the Vistula River ranged 

from an initial 44 km per year, up to 197 km per year thereafter (mean ~ 88 km per year) (Grabowska 

2011).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 No controls methods were found in an effort to prevent the establishment of P. glenii in the Great Lakes. 

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 108

>100 High Adjustments

B. Critical species A*(1- 0%) 108

51-99 Moderate C. Natural enemy B*(1- 5%) 102.6

Control measures C*(1- 0%) 102.6

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact
513

IMPACT POTENTIAL RESULTS

Environmental: High 

Socio-Economic: Low 

Beneficial: Moderate

Perccottus glenii has the potential for high environmental impact if introduced to the Great Lakes.

Perccottus glenii is a host to some parasites. Data suggests that parasites Myxidium rimskykorsakowi, 

Henneguya alexeevi, Nippotaenia mogurndae, and Gyrodactylus perccotti were introduced to new 

regions with P. glenii as a vector (Sokolov et al. 2014); these parasites infect fishes in the Odontobutidae 

family. The parasite load of this species is more diverse in its introduced ranges than in its native range. 

As a trophic competitor and a predator, Perccottus glenii has been implicated in the population declines 

of historically abundant native species such as Umbra krameri, Carassius carassius, and Leucapspius 

delineatus (Koščo et al. 2003). Habitats with high numbers of Perccottus glenii were associated with 

lower fish species richness and diversity. Perccottus glenii can potentially compete with native species 

that utilize similar microhabitats and food resources (Koščo et al. 2003). 

By feeding heavily on macroinvertebrates, larval and adult amphibians, and fish eggs, Perccottus glenii 

has the potential to alter predator-prey relationships (Reshetnikov 2003). Many aquatic larvae of 

terrestrial organisms are primary consumers and export nitrogen from the system when leaving the water 

at maturity, which is meaningful for nitrogen dynamics and the rate of eutrophication. Perccottus glenii

effectively reduces the transport of nitrogen from aquatic to terrestrial environments by feeding on these 

organisms.

Perccottus glenii has the potential for low socio-economic impact if introduced to the Great Lakes. 

Perccottus glenii is a host to the liver fluke, which is a parasite that infects humans (Mastitsky et al. 

2010), but there are no reports suggesting that Perccottus gleniii is responsible for liver fluke infection in 

humans. There is no indication that this species impacts water quality, markets, or infrastructure. There is 

no evidence suggesting that it inhibits recreation or diminishes the natural value of the areas it inhabits.

Perccottus glenii has the potential for moderate beneficial impact if introduced to the Great Lakes.

Small introductions of Perccottus glenii in Eurasia were attempted in effort to reduce mosquito 

populations with no significant results (Koščo et al. 2003). This species can be used as a bait fish and is 

sometimes kept in ponds or aquariums (Koščo et al. 2008, Reshetnikov 2004). There is no indication that 

Perccottus glenii is valuable for medical research, for removing toxins, or for positively impacting the 

ecosystem. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.
514

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Perccottus glenii is host to liver fluke as well as an exotic tapeworm (Mastitsky et al. 2010).

 This species is a potential transmitter of diseases (Golovanov and Ruchin 2011).

 P. glenii transmits parasites Nippotaenia mogundae and Eustrongylides (Ondračková et al. 2012a) Data 

suggests that parasites Myxidium rimskykorsakowi, Henneguya alexeevi, Nippotaenia mogurndae, and 

Gyrodactylus perccotti were introduced to new regions with P. glenii as a vector (Sokolov et al. 2014); these 

parasites infect fishes in the Odontobutidae family.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Perccottus glenii has led to unfavorable feeding relationships between other organisms, slower growth of native 

species, and prolonged spawning (Golovanov and Ruchin 2011).

 This species has been implicated in the decrease in populations of native species Umbra krameri, Carassius 

carassius and Leucaspius delineatus which were abundant in the past through competition for identical habitat 

requirements (Lusk et al. 2004).

 P. glenii has partially displaced local species in Tashkent (Welcomme 1988). 

 This species has displaced several species of native fishes (Solarz 2005). 

 Perccottus glenii has threatened Umbra krameri (European mud minnow), a IUCN Vulnerable species in 

Slovakia, through competition for resources and predation (Koščo et al. 2008). 

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 
515

Not significantly 0

Unknown U 

 Perccottus glenii is a severe threat to the great crested newt, T. cristatus (Reshetnikov 2012).

 This species has completely eliminated some amphibian species in some areas (Reshetnikov and Ficetola 2011).

 P. glenii has threatened Umbra krameri (European Mud Minnow), a IUCN “Vulnerable” species in Slovakia, 

through competition for resources and predation (Koščo et al. 2008). 

 Perccottus glenii has threatened Rhynchocypris percnurus (Lake Minnow), a IUCN “Endangered” species in 

Poland, through predation (Wolnicki and Kolejko 2008). 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 While P. glenii will eat aquatic plants (Golovanov 2013) and plankton (Koščo et al. 2008), the effect on these 

communities has not been reported.
516

Environmental Impact Total 8

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √

Not significantly 0 

Unknown U

 Perccottus glenii is a host to liver fluke in humans as well as an exotic tapeworm (Mastitsky et al. 2010).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U 

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √
517

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

 Perccottus glenii has been known to be mixed with stocking fish such as carp, but there do not seem to be high 

impacts on industry (Reshetnikov 2004)

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
518

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 

Unknown U √

 Perccottus glenii has impacted Crucian Carp (Carassius carassius) populations, leading either to reproductive 

failure (Reshetnikov 2003) or elimination of all individuals less than 40 mm in length (Reshetnikov 2000). While 

this species had not been introduced to the Great Lakes, it is related to other nonnative cyprinids in the basin’s 

waters (Courtenay 2006).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Perccottus glenii has no positive economic importance (Koščo et al. 2008)

 This species is sometimes used as bait fish (Koščo et al. 2008)

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Perccottus glenii has no positive economic importance (Koščo et al. 2008)

 This species is sometimes used as bait fish (Koščo et al. 2008)

 P. glenii is sometimes kept in garden ponds or aquariums (Reshetnikov 2004)
519

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
520

Scientific Name: Phoxinus phoxinus

Linnaeus, 1758

Common Name: Eurasian Minnow

Synonyms: Common Minnow, Cyprinus aphya, Cyprinus chrysoprasius, Cyprinus galian, Cyprinus 

isetensis, Cyprinus lumaireul, Cyprinus morella, Cyprinus phoxinus, Cyprinus rivularis, Leuciscus 

phoxinus, Phoxinus csikii, Phoxinus laevis, Phoxinus marsilii, Phoxinus rivularis, Phoxinus varius, 

Phoxynus montanus, Salmo rivularis

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate 

Phoxinus phoxinus has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Phoxinus phoxinus may be able to be taken up in ballast water and survive ballast tank environments. 

This species is capable of surviving over two weeks without food (Russell and Wootton 1992), and can 

tolerate a wide range of temperatures (Frost 1943, Thorman 1986) and moderately low dissolved oxygen 

levels (Jones 1952). However, current ballast regulations may substantially impact its survival. Phoxinus 

phoxinus occurs in ports that have direct trade connections with the Great Lakes (Hesthagen and 

Sandlund 2010, NBIC 2009). 

Phoxinus phoxinus does not currently occur near waters connected to the Great Lakes. This species is not 

known to hitchhike or foul recreational gear. It is not cultured, stocked, or sold in the Great Lakes region. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
521

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 The distribution of the species is currently limited to Europe (Froese and Pauly 2015, USEPA 2008).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 The distribution of the species is currently limited to Europe (Froese and Pauly 2015, USEPA 2008).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
522

Yes, this species is available for purchase. 100 

No, this species this species is rarely/never sold. 0 √

Unknown U

 Phoxinus phoxinus is commonly used as bait in Europe but not in North America (Kolar and Lodge 2002, 

Museth et al. 2007).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 There has been no record of use in North America.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
523

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There has been no record of use in North America.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Phoxinus phoxinus can survive more than two weeks without food with little to no adverse effects on long-term 

viability (Russell and Wootton 1992).

 Some brackish or freshwater species have been found to be able to persist in ballast tanks even after open 

ocean exchange due to retention of some of the fresh water within the tanks (Ricciardi and MacIsaac 2000), but 

current regulations are likely to substantially impact survival.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?
524

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Phoxinus phoxinus is found throughout Europe and is endemic in the Ponto-Caspian region (Kolar and Lodge 

2002, USEPA 2008).

 Phoxinus phoxinus occurs in the Baltic Sea (Hesthagen and Sandlund 2010).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
525

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Phoxinus phoxinus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

The Great Lakes climate is similar to the current range of Phoxinus phoxinus (USFWS 2014b). Phoxinus 

phoxinus can tolerate a broad range of temperatures and moderately low oxygen levels. This species 

occurs in the southern Bothnian Sea, Sweden, which has ice cover for about 4-5 months (Thorman 1986); 

thus it is likely that it is capable of overwintering in the Great Lakes. This species inhabits littoral zones 

with gravel and rocky bottoms (Museth et al. 2002), which are habitats that are available in the Great 

Lakes basin. Due to its broad physiological tolerance, Phoxinus phoxinus will likely be able to adapt to 

the effects of climate change in the Great Lakes. As an omnivorous fish with a broad diet, P. phoxinus is 

likely able to find an appropriate food source in the Great Lakes. It has been suggested by Borgstrøm et 

al. (2010) that introduced P. phoxinus competes with brown trout for prey, causing reduced brown trout 

recruitment and individual growth rates. The fecundity of Phoxinus phoxinus ranges from 200-1,000 eggs 

per female (Museth et al. 2002), which is slightly lower than the fecundity of P. cumberlandensis of 1,540 

eggs per female (Starnes and Starnes 1981). 

After its introduction to Lake Øvre Heimdalsvatn in the 1960s, it was heavily preyed on by Brown Trout 

(Museth et al. 2003). Brown Trout currently occurs in the Great Lakes and is non-native (Baker and Li 

2015b), but it is unknown whether it will prevent the establishment of P. phoxinus in the Great Lakes. Its 

distribution has spread primarily by anglers (Museth et al. 2007). In Norway, its spread was limited to the 

southeast during the early 1900s, but by the 1950s, translocations of P. phoxinus had become frequent. In 

Lake Øvre Heimdalsvatn, P. phoxinus were first observed in 1969 and spread to the whole lake by 1985 

(Naestad and Brittain 2010). Phoxinus phoxinus has also spread by unintentional introduction with the 

stocking of hatchery-reared brown trout, and by dispersal downstream from upstream reservoirs (Museth 

et al. 2007).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 6
526

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Phoxinus phoxinus has been documented in a wide range of habitats with diverse conditions, including varied 

pH, nutrients, temperatures, and depths (Frost 1943, Hesthagen and Sandlund 2010).

 Temperature tolerance for this species ranges from 2°C to 20°C (Riehl and Baensch 1991). 

 Phoxinus phoxinus is found in a wide range of cold and well oxygenated habitats from small, fast-flowing 

streams to large Nordic lowland river, in addition to small upland lakes to large oligotrophic lakes (Froese and 

Pauly 2015).

 This species is found in salinities up to 6 ppt (Thorman 1986).

 It occurs in waters that have ice cover over the winter and have been recorded in waters with temperatures up 

to 31°C (Frost 1943).

 Experiments by Jones (1952) suggest that this species does not react to waters 4-6 mg/L O2, but does produce a 

reaction below those dissolved oxygen levels.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 The distribution of European Minnows has been documented in Arctic streams and English ponds (Frost 1943, 

Mills 1988).

 Temperature tolerance for this species ranges from 2°C to 20°C (Riehl and Baensch 1991). 

 Phoxinus phoxinus overwinters in coarse substrate or in deep pools with low current (Kottelat and Freyhof 

2007).

 This species occurs in the southern Bothnian Sea, Sweden, which has ice cover for about 4-5 months (Thorman 

1986).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6 

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0
527

Unknown U

9

 The diet of P. phoxinus has been shown to vary among chironimids, amphipods, EPT taxa, cladocerans, 

terrestrial invertebrates, etc. and has been shown to shift in preference among these with competitive pressure 

from brown trout (Museth et al. 2010, Oscoz et al. 2006).

 Phoxinus phoxinus feeds on algae, plant debris in rivers, mollusks, crustaceans and insects (Billard 1997).

 Phoxinus phoxinus feeds on zooplankton, aquatic and terrestrial macroinvertebrates, mollusks, and plant 

material (Frost 1943).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3 

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 There is evidence of diet overlap between Brown Trout and European Minnows, with mixed evidence of 

competitive exclusion. Coexistence has been demonstrated through diet shifts (Museth et al. 2010) although 

Brown Trout populations have shown declines in both growth rates and overall biomass after P. phoxinus

invasion (Borgstrøm et al. 2010).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Phoxinus phoxinus is listed as having a high reproductive potential (USFWS 2014b).

 This species has been found in high population densities post-invasion in freshwater lakes (Museth et al. 2007).
528

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0 

Unknown U

1

 Phoxinus phoxinus generally are found in shallow, littoral waters with stony substratum, and reproduce 

sexually in these same areas (Frost 1943). 

 Phoxinus phoxinus displays high variability in rates of reproductive maturity, clutch size, and frequency of 

spawning (Mills 1988). 

 There are no documented adaptations that would be beneficial to establishment.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Phoxinus phoxinus can be found in a wide variety of conditions throughout most of Europe (Hesthagen and 

Sandlund 2010, USEPA 2008). 

 A climate match (USFWS 2014b) showed a high climate match for the Great Lakes region.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6
529

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 High amounts of ecological and phenotypic plasticity have been demonstrated in the minnows (Museth et al. 

2007), and they have a wide range of habitats throughout Europe (USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Phoxinus phoxinus is found in littoral zones with rocky substrate, with high overlap of habitat with brown trout 

(Borgstrøm et al. 2010, Museth et al. 2002, Museth et al. 2007, Museth et al. 2010, Naestad and Brittain 2010).

 Phoxinus phoxinus is also found in a wide range of cold and well oxygenated habitats from small, fast-flowing 

streams to large Nordic lowland rivers and from small upland lakes to large oligotrophic lakes (Froese and 

Pauly 2015).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Phoxinus phoxinus has a high degree of phenotypic plasticity that allows for adaptation to and wide 

distribution within diverse ecosystem properties (Museth et al. 2007, USEPA 2008).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?
530

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 The diet of P. phoxinus has considerable variation among chironimids, amphipods, EPT taxa, cladocerans, 

terrestrial invertebrates, etc. (Oscoz et al. 2006) and has been shown to shift in preference among these with 

competitive pressure from brown trout (Museth et al. 2010).

 Phoxinus phoxinus feeds on algae, plant debris (in rivers), mollusks, crustaceans and insects (Billard 1997). 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no evidence of another species needed for any stage of the P. phoxinus life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

9
531

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is no evidence of any such species needed to faclilitate the establishment and spread of P. phoxinus.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-5%

 Eurasian Minnows are often prey for salmonids (Borgstrøm et al. 2010, Museth et al. 2003), yet low 

abundances of these species within the Great Lakes makes predatory prevention unlikely.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6 

Frequent, small inocula OR infrequent, large inocula 3
532

Infrequent, small or moderate inocula 0

Unknown U

U

 Since the foremost potential vector is ballast water, frequent inoculations could be expected, yet management of 

ballast water practices should reduce the frequency. 

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

3

 Invasive populations have established and spread throughout Norway (Museth et al. 2007).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 The spread of P. phoxinus in Norway has been relatively quick, although its use as a bait species by anglers has 

been the major vector of spread (Museth et al. 2007).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

-90% total 

points (at 
533

highly effective in preventing the establishment and spread of this species) end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 96

>100 High Adjustments

B. Critical species A*(1- 0%) 96

51-99 Moderate C. Natural enemy B*(1- 0%) 91.2

Control measures C*(1- 0%) 91.2

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

Phoxinus phoxinus has the potential for moderate environmental impact if introduced to the Great 

Lakes.
534

Following the introduction of Phoxinus phoxinus, the composition of the littoral benthos changed from 

one that was once dominated by Ephemeroptera, Trichoptera, Plecoptera, and Gammarus lacustris to one 

that is dominated by chironomids and ogliochaetes (Naestad and Brittain 2010). By changing the 

composition of the lower food web, P. phoxinus has the potential to alter predator-prey relationships. In 

subalpine lakes in southern Norway, P. phoxinus has been implicated as a carrier of parasites that infect 

snails, mussels, and some insects (Hesthagen and Sandlund 2010). There are no reports that show that 

Phoxinus phoxinus has outcompeted native species or genetically impacted native species. It has not been 

indicated that P. phoxinus negatively affects water quality or the physical components of an ecosystem.

Phoxinus phoxinus has the potential for low socio-economic impact if introduced to the Great 

Lakes. 

It has been suggested that the presence of Phoxinus phoxinus in Lake Øvre Heimdalsvatn has resulted in 

reduced recruitment and reduced annual individual growth rates in brown trout, a recreationally valuable 

fish that is stocked (Borgstrøm et al. 2010, Museth et al. 2007). Phoxinus phoxinus does not pose a threat 

to human health or water quality. This species is not known to damage infrastructure. It does not affect 

any markets or economic sectors, and does not diminish the perceived natural value of the areas it 

inhabits.

Phoxinus phoxinus has the potential for low beneficial impact if introduced to the Great Lakes.

Anglers in Europe value P. phoxinus as bait fish (Museth et al. 2007). There are no reports suggesting that 

P. phoxinus can act as a biological control agent. It is not recreationally or medically valuable. This 

species is not known to improve water quality or to have a positive ecological impact.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Phoxinus phoxinus has been documented transporting parasites which infect snails, mussels, etc. (Hesthagen 

and Sandlund 2010).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 6 
535

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 Benthic macroinvertebrate populations of Gammarus lacustris and Lepidurus arcticus declined significantly in a 

Norwegian lake following introduction of P. phoxinus (Museth et al. 2010, Naestad and Brittain 2010). 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 There is no documentation of genetic effects on other populations.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 There is no documentation of negative effects on water quality caused by the minnows.
536

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 Eurasian Minnows do not alter the physical environment.

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
537

Not significantly 0 √

Unknown U

 There are no documentation of human health impacts.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There are no documentation of damage to infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There are no documentation of negative effects on water quality. 

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There are no documentation of negative effects on markets or economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 Phoxinus phoxinus has been implicated in Brown Trout declines (Borgstrøm et al. 2010, Museth et al. 2007). 

Brown Trout populations have shown declines in systems invaded by Eurasian Minnows (Borgstrøm et al. 

2010). Although not a native species in the Great Lakes, Brown Trout is currently stocked by several Great 

Lakes states as a recreational sport fish (USFWS and GLFC 2010), and adverse effects on this population 

should be considered.
538

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 
539

Yes, it is economically important to at least one of these industries 6 

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 The European Minnow is frequently used for bait in Europe (USFWS 2012).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 
540

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
541

Scientific Name: Pseudorasbora parva

Common Name: Stone Moroko, Topmouth Gudgeon, False Rasbora

Synonyms: Leuciscus parvus Schlegel, 1842; L. pusillus Temmnick et Schlegel, 1846; Fundulus 

virescens Temmnick et Schlegel, 1846; Leuciscus pusillus Temmnick et Schlegel, 1846; Micraspius 

mianowski Dybowski, 1869; Aphiocypris chinensis Fowler, 1924; Pseudorasbora altipinna Nichols, 

1925; Pseudorasbora fowleri Nichols, 1925; Pseudorasbora depressirostris Nichols, 1925; 

Pseudorasbora monstruosa Nichols, 1925; Pseudorasbora parva parvula Nichols

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Low

Unauthorized intentional release: Unknown

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Pseudorasbora parva has a low probability of introduction to the Great Lakes (Confidence level: 

Moderate).

Potential pathway(s) of introduction: Hitchhiking/Fouling, Unauthorized Intentional Release

This species has been introduced into Europe as a contaminant of imported fish, particularly Golden Orfe 

and the Common Carp. Whether these species are imported into the Great Lakes region will dictate the 

likelihood of introduction.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
542

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Pseudorasbora parva was introduced in Europe with stockings of herbivorous fishes (Cyprinus carpio, 

Ctenopharyngodon idella, Aristichthys nobilis, Hypophathalmichthys molitrix) imported from China (Panov 

2006, Gozlan et al. 2010a).

 The introduction and spread of Topmouth Gudgeon in the United Kingdom has been linked to imports and 

movements of the ornamental variety (Golden Orfe) of Ide, Leuciscus idus (Copp et al. 2010). Golden Orfe is 

sold in the Great Lakes area (e.g., William Tricker, Inc: http://www.tricker.com/Category/golden-orfe-fish).

 After Golden Orfe, other species associated with P. parva in the United Kingdom include European Catfish 

(Silurus glanis), North American Landlocked Salmon (Salmo salar), Silver Bream (Abramis bjoerkna), Grass 

Carp (Ctenopharyngodon idella), andKkoi Carp (Cyprinus carpio haematopterus) (Copp et al. 2010, Kohlmann 

et al. 2003).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 Pseudorasbora parva is not present in North America.

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
543

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 

Unknown U √

 In Europe, has spread via private stocking/introductions, because it is often kept in ponds and sold as 

ornamental fish or bait fish (S. Nehring, pers. comm. in Gozlan et al. 2010a, Witkowski 2011).

 Other secondary pathways, such as cultural or religious acts, have also been responsible for some secondary 

spread (C. Zhang, pers. comm. in Gozlan et al. 2010a.). For example, people in Tibet traditionally buy small 

live fish in local fish markets and return them to the wild; in the last decade, P. parva has been reported from 

fish markets in big cities of Tibet such as Lhasa and Xigaze (C. Zhang, pers. comm.in Gozlan et al. 2010a).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U √

 Pseudorasbora parva is not known to sold in North America, but it may contaminate other fish stocks.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

Score x 0.25
544

occur within 20 km of the basin because of the species’ popularity/value.

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U
545

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

U x U U Unknown

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
546

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Pseudorasbora parva has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

The life history traints of this species that would suggest its establishment success include a wide 

tolerance of environmental conditions, reaching sexual maturity in the first year of life, batch spawning, 

and nest guarding (Pinder et al. 2005).

The combination of these life history traits, and the range of invaded countries with contrasting climates 

(i.e. Algeria, Iran, Poland, Tibet) reveal the considerable plasticity and adaptability of P. parva to lentic 

and lotic conditions, Mediterranean, continental and Northern climates, and new food resources and 

spawning substrata (Gozlan et al. 2010a).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 This species has a wide tolerance of environmental conditions (Pinder et al. 2005).

 The combination of its life history traits, and the range of invaded countries with contrasting climates (i.e. 

Algeria, Iran, Poland, Tibet) reveal the considerable plasticity and adaptability of P. parva (Gozlan et al. 

2010a).

 This species is limited to freshwater habitats.
547

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 This species is found in Scandinavia (Denmark) (Olesen et al. 2003), so is likely to also overwinter in the Great 

Lakes.

 In Czech Republic and Slovakia this specieshas been found to overwinter in lakes that freeze over for 3 months 

(Rosecchi et al. 1993).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Although there is limited information about the feeding of the introduced populations, isopods, plecoptera and 

trichoptera larvae as well as sponges and detritus were found among the stomach contents and it was 

concluded that P. parva is omnivorous hence eats any food at its disposal (Yalçın-Özdilek et al. 2013).

 The items most frequently ingested by P. parva were benthic crustaceans, insect larvae and zooplankton 

(Cladocera and Cyclopoid Copepoda). The main benthic crustaceans were Gammaridae, Asellidae, 

Conchostraca and harpacticoid Copepoda. Among the insects were larvae of Chironomidae, Chaoboridae, 

Ephemeroptera, Trichoptera and Coleoptera (Rosecchi et al. 1993).

 P. parva, particularly juveniles, feeds on phytoplankton (Hliwa et al. 2002); Bacillariophyta and Cyanobacteria 

were also identified in high proportions in the foregut contents of P. parva particularly during summer (YalçınÖzdilek et al. 2013).

 P. parva mainly feeds on zooplankton such as Cladocera, Copepoda, and Rotifera (Yalçın-Özdilek et al. 2013). 

 In water bodies in China and Germany, P. parva was reported to feed on eggs and larvae of native fish species 

(Stein and Herl 1986, Yang 1996, Xie et al. 2000).

 P. parva has also been reported to be a carnivore (Billard 1997).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9
548

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 Introduction of the invasive Asian Cyprinid fish Pseudorasbora parva into a 0.3 ha pond in England with a fish 

assemblage that included Cyprinus carpio, Rutilus rutilus and Scardinius erythrophthalmus resulted in their 

establishment of a numerically dominant population in only 2 years; density estimates exceeded 60 ind./m2and 

they comprised >99% of fish present (Britton et al. 2010). 

 The effect of P. parva competition on Common Carp was tested, and found to have no greater effect than 

intraspecific competition: Additive treatments revealed that the growth of C. carpio was significantly 

suppressed following the introduction of P. parva with the magnitude of growth suppression directly 

proportional to P. parva density and biomass. A substitutive treatment that tested for the effect of intraspecific 

competition revealed that when C. carpio was introduced at a similar biomass to P. parva, there was no 

significant difference in the extent of the suppressed growth. At the same density, however, the effect of C. 

carpio (higher biomass) on growth was significantly above that of P. parva (lower biomass). This was 

independent of the initial body sizes of the introduced fishes. Thus, the interspecific competition imposed by P. 

parva was only as strong as the intraspecific competition of C. carpio when present at a similar biomass. 

Notwithstanding, the introduction of such small-bodied fishes remains of great concern because of their 

increased ability to rapidly establish and form pest populations of high biomass when compared with largerbodied fishes (Britton et al. 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

2

 Absolute fecundity has ranged from 121-7124 eggs (Záhorská and Kováč 2009) , with a mean of 963-1054 eggs 

per season (Yunzhi 2009). Spawning is multi-litter, wish several dozen eggs in a batch (Panov 2006).

 Other minnow species in the family Cyprinidae, subfamily Leuciscinae, include: Fathead Minnow (Pimephales 

promelas), 6803-10164 eggs per season, also a batch spawner (Gale and Buynak 1982); Bluntnose Minnow 

(Pimephales notatus), 1112-4195 eggs per season, also a batch spawner (Gale 1983); red shiner (Notropis 

lutrensis), 4701-8248 eggs per season, also a batch spawner (Gale 1986); Emerald Shiner (Notropis 

atherinoides), mean 3410 eggs per season (Campbell and MacCrimmon 1970).
549

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 This species is a nest guarder (Pinder et al. 2005).

 P. parva Sexually matures within the first year of life (Gozlan et al. 2002).

 This species exhibits high phenotypic plasticity, i.e., in response to habitat disturbance, increases the number of 

oocytes and decreases their size (2009).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 P. parva inhabits regions with a wide range of climatic conditions, these include areas similar to the Great 

Lakes. For example, Slovakia has warm summers and cold, cloudy and humid winters. There are almost no 

extremes below minimal −20 °C (−4 °F) or above maximal 37 °C (99 °F). 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6
550

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 The wide distribution of P. parva, including lakes, rivers and artificial canals, indicates it encounters abiotic 

conditions similar to those of the Great Lakes. 

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 A study done by Kapusta et al. (2008) found that P. parva preferred habitats that were abundantly overgrown 

with submerged vegetation and avoided areas devoid of macrophytes. Thus, as the bottom cover increased, so 

did the relative number of this fish.

 Spawning occurs at temperatures of 15-19°C (Panov 2006).

 The spawning is multi-litter and takes place in the littoral zone. The eggs are laid on plants, sand, stones, 

mollusc shells, artificial materials such as plastic pipes and other substrata (Gozlan et al. 2010a , Panov 2006).

 P. parva inhabits ponds, lakes, rivers, agricultural channels. The species adapts to artificial ditches easily and 

successfully (Onikura and Nakajima 2013).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

4

 As this species can inhabit a wide range of conditions, climate change would likely not be a significant event for 

this species.
551

 It may do better than native species as it exhibits high phenotypic plasticity in response to habitat disturbance 

(Záhorská and Kováč 2013).

 The impacts of increased salinization are unknown.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Although there is limited information about the feeding of the introduced populations, isopods, plecoptera and 

trichoptera larvae as well as sponges and detritus were found among the stomach contents and it was 

concluded that P. parva is omnivorous hence eats any food at its disposal (Yalçın-Özdilek et al. 2013).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9
552

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Predators include Pike (Esox lucius), Pike-perch (Sander lucioperca), Perch (Perca fluviatilis), and potentially 

other piscivores, but these predators have not prevented P. parva from establishing throughout Europe (Britton 

et al. 2010, Panov 2006).

 The biotic resistance against introduced Topmouth Gudgeon (Pseudorasbora parva) (a highly invasive fish in 

Europe) by Resident Carp Cyprinus carpio was tested in experimental mesocosms. The introduction scenario 

was six adult P. parva (three male, three female) on a single occasion. Resistance to their establishment was 

provided by three and six resident C. carpio whose effects on P. parva growth and reproduction were compared 

to a Control (no resident fish at the time of introduction) and treatments containing three and six P. parva. After 

120 days, the growth rates of the introduced P. parva were significantly depressed in C. carpio presence and in 

mesocosms with three C. carpio present, significantly decreased numbers of 0+P. parva were recorded. Where 
553

six C. carpio were present, no 0+P. parva were recorded, indicating resistance strength increased with carp 

abundance. However, the authors acknowledge the small mesocosms allowed no opportunity for resource 

segregation, and as such this effect may not occur so strong in the wild (Britton 2012).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 This will depend on importation of stock at risk of contamination.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species is native to east Asia, in Europe it was first recorded in 1961 from southern Romania and Albania. 

In 1972 the species was recorded from the European part of the former USSR – the Danube delta and Dniester. 

In slightly over 40 years it has almost entirely colonized Europe, proceeding rapidly from east to west, invading 

32 countries including Hungary, former Czechoslovakia, France, Austria, Germany, Belgium, the Netherlands, 

Bulgaria, northern Greece, Turkey and the western part of the Balkans, Poland, Italy, England and Denmark 

(Gozlan et al. 2002, Panov 2006).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 6
554

ranges)

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 This species was first noted in Poland in 1990. By the end of the 1990s, this fish had spread throughout all the 

regions of Poland inhabiting lakes, ponds, and rivers (Kotusz and Witkowski 1998).

 In slightly over 40 years this species has almost entirely colonized Europe (Panov 2006).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 102

>100 High Adjustments

B. Critical species A*(1- 0%) 102

51-99 Moderate C. Natural enemy B*(1- 0%) 91.8

Control measures C*(1- 0%) 91.8

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High 1
555

2-5 Moderate Total # of questions unknown

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Unknown

Beneficial: Low

Pseudorasbora parva has the potential for high environmental impact if introduced to the Great 

Lakes.

Pseudorasbora parva has 84 parasite species although generally only a few of these are transferred to a 

new site of introduction. Specifically, these are typically zoosporic fungi (Czeczuga et al. 2002), parasites 

such as Diplostomum spataceum in Georgia (Kakalova and Shonia 2008), and viruses such as fry 

rhabdovirus (PFR) in Germany (Ahne and Thomsen 1986). The PFR virus, which causes acute disease of 

Esox lucius fry, has been isolated from P. parva. The two most severe parasites found associated with P. 

parva in its invasive range are Anguillicola crassus and rosette agent Sphaerothecum destruans (Gozlan 

et al. 2005, Gozlan et al. 2009, Gozlan et al. 2010b, Witkowski 2011). These parasites if carried over after 

introduction could have destructive impacts on similar native Great Lakes species. 

Pseudorasbora parva is one of the most (or the most) dominant species in fish assemblages where it is 

established (Kapusta et al. 2008, Tang et al. 2013). If introduced into the Great lakes, P. parva could 

cause noticeable stress or decline in at least one native population. Predator-prey relationships would be 

significantly adversely affected by the introduction of P. parva. 

Current research on the potential for socio-economic impacts to result from Pseudorasbora parva if 

introduced to the Great Lakes is inadequate to support proper assessment.

It is unknown whether P. parva poses hazards or threats to human health. P. parva does carry parasites 

that are able to infect humans (Bao 2012, Pak et al. 2009, Xu et al. 2010, Zhou et al. 2008) but there are 

no documentations of P. parva directly transferring these to humans (Gozlan et al. 2010a). A series of 

three (successful) eradication exercises from United Kingdom lakes has cost approximately £130,000 in 

public funds (Britton et al. 2008).

There is little or no evidence to support that Pseudorasbora parva has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Psuedorasbora parva can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not pose significant positive ecological impacts. P. parva has no economic 

value and it is only used by sport fishermen as bait fish (Lenhardt et al. 2011). 
556

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U

 P. parva has 84 parasite species: Protozoa (40), Monogenea (10), Cestoda (3), Trematoda (16), Nematoda (3), 

Acanhocephala (6), Bivalvia (1), Crustacea (4), Hirudinea (1) (Margaritov and Kiritsis 2011), although 

generally only a few of these are transferred to a new site of introduction.

 Specifically, these are typically zoosporic fungi (Czeczuga et al. 2002), parasites such as Diplostomum

spataceum in Georgia (Kakalova and Shonia 2008) and viruses such as fry rhabdovirus (PFR) in Germany 

(Ahne and Thomsen 1986). The PFR virus, which causes acute disease of Esox lucius fry, has been isolated 

from P. parva. The two most severe parasites found associated with P. parva in its invasive range are 

Anguillicola crassus and rosette agent Sphaerothecum destruans (Gozlan et al. 2005, Gozlan et al. 2009, 

Gozlan et al. 2010b, Witkowski 2011).

 Sphaerothecum destruans: 

o P. parva carries a pathogen that has caused increased mortality and completely inhibited 

spawning in an endangered European cyprinid, Leucaspius delineatus. Mortality in laboratory 

experiments was 69%; mortality in a large outdoor pond was 96%. Preliminary examination 

indicates other cyprinids and salmonids are also susceptible. This threat is caused by an infectious 

pathogen, a rosette-like intracellular eukaryotic parasite that is a deadly, nonspecific agent. It is 

probably carried by healthy P. parva fish, and could decrease fish biodiversity in Europe, as well 

as having implications for commercial aquaculture (Gozlan et al. 2005).

o The emerging rosette-like agent is Sphaerothecum destruens, originally found to be responsible 

for disease outbreaks in captive salmon in the United States. Unlike the situation in the United 

States, its low host specificity and occurrence in invasive fishes presents a risk of spread from wild 

invasive populations to sympatric populations of susceptible native fish and as such represents a 

risk for fisheries, as movement of fish for stocking purposes is common practice. Fish transmission 

may occur when infected fish release the parasite with bile, urine, and seminal and ovarian fluids 

during spawning. Shedding from the gut epithelium and even the skin and gills may be additional 

sources (Gozlan et al. 2009).

 The prevalence of Clonorchis sinensis metacercariae was 100% in Pseudorasbora parva. Human beings and 

other piscivorous mammals become infected with C. sinensis when they consume raw or undercooked 

freshwater fishes and shrimp infected by C. sinensis metacercaria (Zhou et al. 2008). The parasite causes 

clonorchiasis and is often associated with many human diseases such as biliary calculi, cholecystitis, liver 

cirrhosis, and even cholangiocarcinoma (Bao 2012, Pak et al. 2009, Xu et al. 2010)..

 The marked isotopic shifts shown in all taxa in the P. parva invaded pond (13C-enriched, 15N depleted) were 

indicative of a shift to a cyanobacteria-dominated phytoplankton community. This may have resulted from 

grazing by P. parva of zooplankton, which in turn would have consumed unpalatable phytoplankton such as 

cyano-bacteria (Britton et al. 2010).
557

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Where established, this species is one of the most (or the most) dominant species in the fish assemblage. In 

Poland, P. parva was the most dominant fish caught: it comprised 32.6% of all the fish caught, and its 

permanence of occurrence in the samples was 60% (Kapusta et al. 2008). In China, P. parva was the most 

dominant fish caught comprised 25.432% of all fish caught, its permanence of occurrence in the samples was 

87.50% (Tang et al. 2013).

 Introduction of the invasive Asian cyprinid fish Pseudorasbora parva into a 0.3 ha pond in England with a fish 

assemblage that included Cyprinus carpio, Rutilus rutilus and Scardinius erythrophthalmus resulted in their 

establishment of a numerically dominant population in only 2 years; density estimates exceeded 60 ind./m2and 

they comprised >99% of fish present (Britton et al. 2010). 

 The effect on Common Carp was tested, and found no greater effect than intraspecific competition: Additive 

treatments revealed that the growth of C. carpio was significantly suppressed following the introduction of P. 

parva with the magnitude of growth suppression directly proportional to P. parva density and biomass. A 

substitutive treatment that tested for the effect of intraspecific competition revealed that when C. carpio were 

introduced at a similar biomass to P. parva, there was no significant difference in the extent of the suppressed 

growth. At the same density, however, the effect of C. carpio (higher biomass) on growth was significantly 

above that of P. parva (lower biomass). This was independent of the initial body sizes of the introduced fishes. 

Thus, the interspecific competition imposed by P. parva was only as strong as the intraspecific competition of C. 

carpio when present at a similar biomass. Notwithstanding, the introduction of such small-bodied fishes 

remains of great concern because of their increased ability to rapidly establish and form pest populations of 

high biomass when compared with larger-bodied fishes (Britton et al. 2011).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 P. parva feeds on juveniles of native fish. In the open waters of southern Europe it has probably contributed to a 

decrease in abundance or even disappearance of some autochthonous cyprinids (Panov 2006).

 Consumes larger species of planktonic crustaceans, which results in an increase in the quantity of 

phytoplankton, increasing eutrophication of the water bodies (Adamek and Sukop 2000).

 Comparison with stable isotope analysis values collected from an adjacent pond free of P. parva revealed a 

simplified food web in P. parva presence, but with an apparent trophic position shift for several fishes, including 

S. erythrophthalmus which appeared to assimilate energy at a higher trophic level, probably through P. parva

consumption (Britton et al. 2010).
558

 In laboratory experiments at densities similar to that in the environment, P. parva larvae depressed the 

populations of most planktonic cladoceran and rotifer species but not the abundances of copepod nauplii or the 

periphytic rotifers Monostyla spp. and Lecane spp. Gut content analyses showed that the fish larvae strongly 

selected for the periphytic rotifer Lecane spp. (Nagata et al. 2005).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6 √

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U

 Pseudorasbora pumila, an indigenous species in Japan and ranked as an endangered species in the Japanese 

Red Data Book, has largely been replaced by the accidental introduction of the gudgeon because of intensive 

hybridization (Konishi and Takata 2004, Konishi et al. 2003).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 19

Total Unknowns (U) 0
559

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 The prevalences of Clonorchis sinensis metacercariae was 100% in Pseudorasbora parva. Human beings and 

other piscivorous mammals become infected with C. sinensis when they consume raw or undercooked 

freshwater fishes and shrimp infected by C. sinensis metacercaria (Zhou et al. 2008). The parasite causes 

clonorchiasis and is often associated with many human diseases such as biliary calculi, cholecystitis, liver 

cirrhosis, and even cholangiocarcinoma (Bao 2012, Pak et al. 2009, Xu et al. 2010).. However, this fish is 

rarely intentionally consumed raw, and these species have not been reported in introduced range (Fan 1998).

 Other food-borne trematodes, for which P. parva acts as an intermediate host and so may result in transmission 

to humans, include Opisthorchis viverrini (Sithithaworn and Haswell-Elkins 2003) and Clinostonum 

complanatum (Aohagi et al. 1992) O. viverrini poses the highest risk to human health causing opisthorchiasis 

by parasitizing the liver and biliary passages of their hosts, and there are approximately 9 million people 

infected globally. These species have not been reported in introduced range (Gozlan et al. 2010a).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U
560

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 The prevalence of Pseudocapillaria tomentosa in Topmouth Gudgeon was 45.1%. Pseudocapillaria tomentosa

infection was associated with mortality in captive Tiger Barbs, Puntius tetrazona, and other ornamental fish 

(Moravec et al. 1984). Heavy infections of P. tomentosa in pond-reared carp or other fish species of economic 

importance can cause economic problems with fish production (Mihok et al. 2011).

 In the native range, P. parva is the second intermediate host for cosmopolitan ligulid tapeworms and to species 

of the Digramma genus that have been the cause of high mortalities in freshwater commercial fisheries in China 

and Russia. These species have not been reported in introduced range (Gozlan et al. 2010b).

 A series of three (successful) eradication exercises from United Kingdom lakes that has cost approximately 

£130,000 of public funds (Britton et al. 2008).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
561

Socio-Economic Impact Total 1

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 This species has no economic value and it is only used by sport fishermen as bait fish (Lenhardt et al. 2011).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 6
562

communities and/or tourism

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 The marked improvement in growth of a piscivore (Scardinius erythrophthalmus) following the invasion of P. 

parva in England indicates that feeding conditions certainly improved for this species (Britton et al. 2010).

Beneficial Effect Total 0

Total Unknowns (U) 0
563

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
564

Scientific Name: Rutilus rutilus

Linnaeus, 1758

Common Name: Roach

Synonyms: Cyprinus rutlius, Cyprinus ruttilus, Gardonus rutilus, Leuciscus rutilus

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Rutilus rutilus has a moderate probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Unauthorized Intentional Release, Transoceanic Shipping (ballast 

water)

Rutilus rutilus is sold as baitfish and is used for recreational fishing in Europe (Froese and Pauly 2015, 

Griffiths 1997); however, this species is not easily obtained in the Great Lakes region. This species may 

be taken up in ballast but its survival may be substantially impacted by current ballast regulatory 

requirements. Rutilus rutilus occurs in ports that have direct trade connections with the Great Lakes 

(Härmä et al. 2008, Lappalainen et al. 2001, NBIC 2009). 

Rutilus rutilus does not currently occur near waters connected to the Great Lakes basin. It is not known to 

hitchhike or foul recreational gear. This species is not cultured, stocked, or sold in the Great Lakes region. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100
565

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 There are no known introductions of Rutilus rutilus in the United (USFWS 2012).

 The species is found in the United Kingdom and Northern Europe (Froese and Pauly 2015).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 There is no reported transport of R. rutilus in North America (USFWS 2012). 

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √
566

No, this species this species is rarely/never sold. 0 

Unknown U

 Rutilus rutilus is used very little for commercial fishing, but it is used as bait and for recreational fishing 

(Froese and Pauly 2015). 

 Rutilus rutilus was introduced to Italy and other countries unintentionally by anglers using it as live bait 

(Griffiths 1997).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 Roach is not found in the Great Lakes nor can it be obtained live in North America.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Roach is not found in the Great Lakes nor can it be obtained live in North America.

 Roach has a low commercial value and is used just for recreational fishing (Froese and Pauly 2015). 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
567

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Ireland is the closest region where Roach have been reported (Ferguson 2008).

 It has low commercial value and is used just for recreational fishing (Froese and Pauly 2015). 

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Rutilus rutilus has not been reported to be found in ballast water, but it has high survival in a variety of 

environments (USFWS 2012).
568

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 The species is prevalent in the Baltic and Black seas near coastal area (Hӓrmӓ et al. 2008).

 In the Northern Baltic Sea, Roach was abundant in gill net catches (Lappalainen et al. 2001). 

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 1.0 80 Moderate

Total Unknowns (U) 0 Confidence Level High
569

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes.

Rutilus rutilus has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate). 

The climate of the introduced and native range of R. rutilus is moderately similar to the climate of the 

Great Lakes (USFWS 2012). Rutilus rutilus primarily occurs in brackish and estuarine waters, but it has 

become abundant in the freshwater Lower Lough Erne (Griffiths 1997). Rutilus rutilus occurs in waters 

that have ice cover over the winter (Geraudie et al. 2010, Härmä et al. 2008), so it is likely that it can 

overwinter in the Great Lakes. Predictions on how climate change affects R. rutilus are contradictory 

(Härmä et al. 2008). Shorter duration of ice cover and warmer temperatures may benefit reproductive 

success; however, salinity negatively impacts embryonic development, so salinization may reduce its 

ability to establish in the Great Lakes. 

This species has a broad, flexible omnivorous diet (Horppila et al. 2000, Volta and Jepsen 2008) and will 

likely find a suitable food source in the Great Lakes. It has the potential to compete with native species, 

but there are no predictions regarding species in the Great Lakes. After the introduction of R. rutilus to 

Northern Ireland, there was a decline in Tufted Duck (Aythya fuligula) populations, and it was suggested 

that it was caused by competition for zoobenthos (Winfield et al. 1992). Zebra mussels are preyed on by 

R. rutilus (Lappalainen et al. 2005) and may potentially facilitate its establishment as an abundant food 

source in the Great Lakes. 

Rutilus rutilus has a slightly higher fecundity compared to fish in the same taxon. Rutilus rutilus has a 

relative fecundity of 87 eggs/g (Jamet and Desmolles 1994) while R. frisii kutum has a relative fecundity 

of 57 eggs/g (Yousefian and Mosavi 2008). Freshwater habitats and eutrophication of the Great Lakes 

may enhance R. rutilus reproduction and development (Härmä et al. 2008, Sandström and Karås 2002).

The survey that led to the first report of R. rutilus in Lake Maggiore, Italy, had evidence that it had 

become one of the most abundant fish in the lake (Volta and Jepsen 2008). In Lake Maggiore, R. rutilus

had a higher growth rate than in other European waters. In Ireland, the spread of R. rutilus was relatively 

slower; after introduction in 1889, it took several decades for it to become abundant (Griffiths 1997). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?
570

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Adult Roaches like to live in brackish waters with salinities of 10% to 15%, while reproduction occurs in ranges 

of <3.5% (.35 ppt) (Bănărescu and Coad 1991, Hӓrmӓ et al. 2008). Upper salinity ranges for reproduction 

have been experimentally determined to be between 7.5% to 10% (Hӓrmӓ et al. 2008).

 However, other reports of this species state that it lives in both fresh and brackish water, and breeds among 

dense submerged vegetation in backwaters or lakes, flooded meadows or in shallow, fast-flowing river habitats 

on plant or gravel bottom (Froese and Pauly 2015).

 Rutilus rutilus is found in a varieties of waters such as the Baltic, Caspian, and Aral Sea with a temperature 

tolerance of <12-28°C and an optimum growth temperature of 20-27°C (Linlokken et al. 2010). Lower 

temperature ranges have not been researched experimentally.

 Feeding and growth of R. rutilus is reduced at temperatures <12°C (Linlokken et al. 2010). 

 Early life stages of R. rutilus are sensitive to salinity (Hӓrmӓ et al. 2008).

 It occurs in waters that have temperatures of 4°C (Geraudie et al. 2010) and have been shown to tolerate 

temperatures up to 30°C (Cocking 1958). At high temperatures of 30°C, it cannot tolerate oxygen levels under 1 

mg/L.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 Studies were not done in lower temperatures to see the survival of R. rutilus, but it is hypothesized that the 

swimming speed and metabolism would be lowered and the feeding habits would be affected (Linlokken et al. 

2010). 

 This species occurs in waters in France, which experience water temperatures of 4-6°C in the winter (Geraudie 

et al. 2010).

 This species occurs in the Baltic Sea,and spawn shortly after ice breakup (Hӓrmӓ et al. 2008).

 The optimum factors for reproduction are temperatures between 4° to 19.5 °C and salinity ranges from 0% to 

3.5%, allowing it to reproduce up to 100,000 pale yellow eggs that are adhesive to submersed aquatic 

vegetation (Hӓrmӓ et al. 2008).

 Other temperatures beneficial to R. rutilus’ survival are 8° to 28°C because they are known to thrive in those 

waters (Nõges and Jarvet 2005).
571

 Rutilus rutilus is found in a varieties of waters such as the Baltic, Caspian, Black Sea and Aral Sea with a 

temperature tolerance of <12°C - 28°C and an optimum growth temperature of 20-27°C (Linlokken et al. 

2010).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 Rutilus rutilus prefers a diet consisting of primary producers and small plankton but can also widen its 

spectrum to things such as detritus in the presence of other competitors such as perch (Horppila 2000). It also 

likes to feed on algae, crustaceans, water plants and insect larvae based on the life stage it is in (Ferguson 

2008).

 Rutilus rutilus has the ability to shift its diet from the littoral to the pelagic zones in order to avoid high 

predation and competition (Froese and Pauly 2015). Research in Finland showed that juvenile roach feed on 

zooplankton and switch their diet to plant material during their adult stage (Horppila 2000). 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 Rutilus rutilus is a dominant competitor and it has been shown to reduce abundance of species such as Atlantic 

Salmon, Brown Trout, Pollan, and its biggest competitor, Perch (Ferguson 2008).

 Rutilus rutilus can comprise up to 70% of the fish biomass due to the feeding habits that can directly and 

indirectly deplete food resources (Ferguson 2008, Griffiths 1997).

 Ireland had the latest invasion of R. rutilus and it was found that Zebra mussels act as a control for the Roach 

population by eating the plankton which is the roach’s primary food source (Minchin et al. 2003). 

 After the introduction of R. rutilus, the once common Tufted Duck, Aythya fuligula experienced a decline in 

their population (Winfield et al. 1992). 
572

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Rutilus rutilus has a high fecundity that can vary with the different regions and habitats. In Ireland it was found 

to reproduce <100,000 eggs, which can tend to have dramatic variations from year to year (Ferguson 2008).

 Rutilus rutilus has a high fecundity compared to fish in the same taxon. Rutilus rutilus has a relative fecundity 

of 87 eggs/g (Jamet 1994) while R. frisii kutum has a relative fecundity of 57 eggs/g (Yousefian and Mosavi 

2008).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

5

 Roach has a high rate of reproduction and can spawn from April to June. It produces adhesive eggs that can 

stick to plants and stones in shallow waters (Ferguson 2008).

 Its schooling behavior can be beneficial by protecting its young and keeping the abundance high (Linlokken et 

al. 2010).

 The Great Lakes would provide an optimum habitat for reproduction because R. rutilus prefers ranges of 0 to 

3.5 ppt during its spawning season, therefore the freshwater of Great Lakes would be ideal (Hӓrmӓ et al. 2008).

 Research has shown that R. rutilus spawns at temperature between 8° - 19.4 °C optimally (Nõges and Jarvet 

2005). 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
573

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The R. rutilus native range has been found to be in latitude 68-71°N, but can tolerate ranges of 71°N to 36°N 

(Froese and Pauly 2015). The Great Lakes latitudes are around 41° - 49° N, which matches the ranges of the 

Caspian Sea (40° N), where R. rutilus can be found in high abundance.

 R. rutilus prefers backwaters or deep parts of lakes to live in over the winter (Froese and Pauly 2015). 

 Climate, of locations where R. rutilus is documented, is highly matched with that of the continental United 

States (USFWS 2012).

 Rutilus rutilus is found in a varieties of waters such as the Baltic, Caspian, Black Sea and Aral Sea. The 

Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002)

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Roach can live in low oxygen environment and nutrient enriched waters (Ferguson 2008). According to the map 

from the Global Biodiversity Information Facility (GBIF 2010), which shows the distributions of R. rutilus

throughout the globe, Great Lakes seems to somewhat match the climate and areas where Roach is found 

(USFWS 2012). 

 Although with this information Roach might have a small chance to adapt to the Great Lakes, it is most likely 

not going to because it prefers to spend its adulthood in brackish waters. 

 Rutilus rutilus lives in both fresh and brackish water and pH range of 10 to 15 (Froese and Pauly 2015).

 Rutilus rutilus primarily occurs in brackish and estuarine waters, but it has become abundant in the freshwater 

Lower Lough Erne (Griffiths 1997).

 Abiotic factors and climatic conditions of the native and introduced ranges of this species are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
574

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Although this species prefers mainly lowland areas, it can also be seen abundantly in nutrient-rich lakes and 

large to medium sized rivers and backwaters (Froese and Pauly 2015). Roach prefer eutrophic lakes because it 

gives them the benefit to capture more zooplankton because of their ability to switch from submerged vegetation 

to primary producers in the instance of increased turbidity or decrease in vegetation (Horppila et al. 2000). 

Adult roach will move to the pelagic zone during growing season in the early summer due to metabolic 

requirements and feeding habits (Horppilla et al. 2000).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 Climate change would be beneficial in many ways for adult roach. Studies shown that with increasing 

temperatures, shorter winters, and lower salinity, R. rutilus is able to spawn sooner for longer periods of time 

(Nõges and Jarvet 2005).

 Predictions on how climate change affects R. rutilus are contradictory (Hӓrmӓ et al. 2008). Shorter duration of 

ice cover and warmer temperatures may benefit reproductive success; however, salinity negatively impacts 

embryonic development, so salinization may reduce its ability to establish in the Great Lakes.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6
575

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Rutilus rutilus initially feeds on plankton and in the case of predators or other environmental changes, it can 

broaden their feeding range. Being an omnivorous fish, it has the advantage to feed on zooplankton, 

zoobenthos, detritus, macrophytes, and aquatic vegetation (Horpilla et al. 2000, Winfield 1986).

 In eutrophic lakes, in the presence of predators or other competitors such as perch, R. rutilus is able to switch 

to detritus and primary producers (Horppila et al. 2000). 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Rutilus rutilus does not depend on any other species to survive (Horppila et al. 2000, USFWS). 

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

6
576

and spread in the Great Lakes)

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

6

 Rutilus rutilus feeds on Zebra mussels (Lappalainen et al. 2005), which have established in the Great Lakes in 

high abundance. 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Stokes et al. (2006) suggest that the recent invasion of Zebra mussel may reduce plankton and somewhat 

control R. rutilus populations, but there is no current evidence that this is effective at reducing R. rutilus 

populations. 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0
577

Unknown U

U

 According to Ferguson (2008), R. rutilus was introduced in Ireland illegally by anglers that used the fish as 

bait.

 The United States Fish and Wildlife Services (2012) surveyed that Roach has little commercial use and it mostly 

used for recreational fishing.

 Its propagule pressure via ballast water introduction has not been reported.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

U

 Roach has been introduced to Spain, northern Italy, Ireland, the lakes region of the United Kingdom, the Azores 

Islands, Portugal, Kazakhstan, Cyprus, Morocco, Australia, and Madagascar (USFWS 2012).

 Rutilus rutilus is established and expanding in almost all introduced locations except for Madagascar (Froese 

and Pauly 2015).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

5

 Ferguson (2008) states that R. rutilus was introduced in Ireland in 1889 but was not seen in high abundance for 

a few decades. Roaches are known to rapidly reproduce in high numbers during their spawning season 

depending on temperatures and salinity levels (Ferguson 2008, Hӓrmӓ et al. 2008). 

 The survey that led to the first report of R. rutilus in Lake Maggiore, Italy, had evidence that it had become one 

of the most abundant fish in the lake (Volta and Jepsen 2008).
578

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 No control methods to prevent the establishment or spread of the roach are in place in the Great Lakes.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 97

>100 High Adjustments

B. Critical species A*(1- 0%) 97

51-99 Moderate C. Natural enemy B*(1- 10%) 87.3

Control measures C*(1- 0%) 87.3

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High
579

Socio-Economic: Moderate 

Beneficial: Moderate

Rutilus rutilus has the potential for high environmental impact if introduced to the Great Lakes.

Arctic Charr (Salvelinus alpinus) has been recently impacted by eutrophication, climate change, and the 

growing populations of R. rutilus. It has been suggested that R. rutilus may compete with Arctic Charr in 

England for zooplankton (Winfield et al. 2008). After its introduction to Lake Erne, the rudd disappeared 

(Cragg-Hine 1973). After the introduction of R. rutilus to Northern Ireland, there was a decline in the 

Tufted Duck (Aythya fuligula) populations, and it has been implicated that it was caused by competition 

for zoobenthos (Winfield et al. 1992). Rutilus rutilus may have altered predatory-prey relationships as a 

food source for the piscivorous Great Crested Grebes (Podiceps cristatus), which experienced a 

population increase after its introduction. Rutilus rutilus may be a carrier of parasites such as tapeworm 

(Ligula intestinalis) (Carter et al. 2005).

Studies conducted by Horppila and Kairesalo (1990) provided evidence that Rutilus rutilus has negatively 

impacted water quality and maintained high algal productivity in southern Finland. Bioturbation occurred 

when R. rutilus was feeding, which released nutrients from the sediments. During times of low 

zooplankton abundance, R. rutilus caused high phosphorous loading and turbidity (Horppila and 

Kairesalo 1992).

Rutilus rutilus has the potential for moderate socio-economic impact if introduced to the Great 

Lakes. 

Rutilus rutilus may curtail efforts to improve water quality; after initial recovery of a lake in southern 

Finland, algal blooms increased and it was suggested that R. rutilus had maintained high algal 

productivity and biomass (Horppila and Kairesalo 1990). Rutilus rutilus may negatively impact 

commercially fisheries and recreational fishing by affecting Atlantic Salmon and Brown Trout stocks 

(Stokes et al. 2006). Rutilus rutilus does not pose a threat to human health and does not damage 

infrastructure. 

Rutilus rutilus has the potential for moderate beneficial impact if introduced to the Great Lakes.

In Europe, Rutilus rutilus is not economically valued for commercial fisheries (Härmä et al. 2008). It is 

valued as a bait fish for recreational fishing (Stokes et al. 2006). It has not been used as biological control. 

Rutilus rutilus is not valued for medicinal or research purposes. It does not remove toxins, increase water 

quality, or have a positive ecological impact. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?
580

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0 

Unknown U

 Parasitic infestations such as worm cataract and blackspot disease have been assessed and tied to Roach 

(USFWS 2012). 

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0

Unknown U

 Rudd populations have been forced to move to other habitats while having a large decline in abundance 

because of high competition with R. rutilus (Stokes et al. 2006).

 Atlantic Salmon and Brown Trout abundances have been negatively impacted as well by Roach (Ferguson 

2008). 

 Perch found in the Baltic Sea has been forced to alter behaviors due to competition against Roach population. 

Decrease in fecundity, and growth were observed through several studies comparing the two (Lappalainen et 

al. 2001).

 The introduction of R. rutilus has been linked to the extinction of the Arctic Charr in Lough Corrib, alongside 

the severe decline in pollan numbers in Lower Lough Erne (Ferguson 2008).

 Arctic Charr (Salvelinus alpinus) has been recently impacted by eutrophication, climate change, and the 

growing populations of R. rutilus. It has been suggested that R. rutilus may compete with Arctic Charr in 

England for zooplankton (Winfield et al. 2008). 

 After its introduction to Lake Erne, the Rudd disappeared (Cragg-Hine 1973). 

 After the introduction of R. rutilus to Northern Ireland, there was a decline in the Tufted Duck (Aythya fuligula) 

populations, and it has been implicated that it was caused by competition for zoobenthos (Winfield et al. 1992).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U
581

 Rutilus rutilus could alter the trophic assemblages in portions of the Great Lakes and food webs near shore and 

bays will be most affected by this species according to how the invaded lakes in Ireland projected (USFWS 

2012).

 After the introduction of R. rutilus to Northern Ireland, populations of the once abundant Tufted Duck, Aythya 

fuligula, experienced a decline in its population (Winfield et al. 1992). Competition for benthos is suggested to 

be the cause. There was an increase in the populations of a piscivorous bird, the great crested grebes (Podiceps 

cristatus), and it is thought that R. rutilus is a food resources for the bird.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 √

Not significantly 0

Unknown U

 Rutilus rutilus produces fertile hybrids with Abramis brama (Common Bream) (Kottelat and Freyhof 2007).

 Neither of these species is native to the Great Lakes.

 Hybrids of Roach and Rudd were recorded in Lough Melvin in 2002 (Stokes et al. 2006).

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 √

Not significantly 0 

Unknown U

 Water quality has been decreased in some lakes due to increased eutrophication by R. rutilus (Stokes et al. 

2006).

 Increased turbidity and algal blooms have been observed in result of zooplanktons being overgrazed by Roach 

(Stokes et al. 2006). 

 Rutilus rutilus has negatively impacted water quality and maintained high algal productivity in southern 

Finland. Bioturbation occurred when R. rutilus was feeding, which released nutrients from the sediments 

(Horppila and Kairesalo 1990). 

 During times of low zooplankton abundance, R. rutilus caused high phosphorous loading and turbidity 

(Horppila and Kairesalo 1992).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

6 
582

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 

Unknown U

 Many studies have shown in different regions around the world a tremendous decrease in the plankton and 

altered macrophyte communities (USFWS 2012).

Environmental Impact Total 11

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U 

 There are no reported threats to humans or any other hazards, but it could be potential pest (Kottelat and 

Freyhof 2007). 

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6
583

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U 

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0

Unknown U √

 Rutilus rutilus reduce water quality in lakes by heavily grazing the zooplankton, which leads to faster 

eutrophication by accelerating algal blooms and causing the waters to become more turbid (Stokes et al. 2006). 

However, there have not been any reports of water quality degradation with respect to human use. 

 Water quality increased when Roach was removed at a large scale in Finland (Stokes et al. 2006). 

 Rutilus rutilus may curtail efforts to improve water quality; after initial recovery of a lake in southern Finland, 

algal blooms increased and it was suggested that R. rutilus had maintained high algal productivity and biomass 

(Horppila and Kairesalo 1990).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 Atlantic Salmon and Brown Trout are important fish on the market with high sales. Roach has reduced some 

abundance in Atlantic Salmon and Brown Trout, but not enough to significantly cause a negative impact on the 

commercial fisheries (Ferguson 2008).

 Rudd, another introduced species in the Great Lakes, has been forced to move in weeded areas and has been 

disappearing everywhere in freshwater lakes in Ireland due to R. rutilus (Stokes et al. 2006). 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0 

Unknown U

 Atlantic Salmon and other species that are affected by Roach are known to be used in recreational fishing, 

therefore they might be slightly impacted, but great damage is not likely to be seen (Ferguson 2008). 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 6
584

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U 

 There have been no reported decreases in natural values of any regions.

Socio-Economic Impact Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Roach prefers to feed on submersed vegetation, yet no significant changes are noticed. 

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0
585

Unknown U

 The United States Fish and Wildlife Services (2012) reported Roach being used for live bait as well as in 

recreational fishing.

 Anglers in Ireland used Rroach as bait for Pike in the early 1990 (Stokes et al. 2006). 

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 The United States Fish and Wildlife Services (2012) reported Roach being used and introduced for live bait as 

well as in recreational fishing.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 
586

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
587

Scientific Name: Sander lucioperca

Linnaeus, 1758

Common Name: Zander, Pikeperch, Sandart

Synonyms: Stizostedion lucioperca

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Low

Hitchhiking/fouling: Low

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unknown

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Sander lucioperca has a low probability of introduction to the Great Lakes (Confidence level: 

Moderate).

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentional 

Release, Stocking

Sander lucioperca eggs may be transported on macrophytes and in substrate. Sander lucioperca would 

have to be transported from where it occurs in North Dakota to the Great Lakes (USFWS 2014e). Many 

think that S. lucioperca would benefit North American fisheries (USFWS 2014e). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Sander lucioperca occurs in North Dakota (USFWS 2014e).

1b) What is the proximity of this species to the Great Lakes basin?
588

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25 

√

Unknown U

 Sander lucioperca occurs in North Dakota (USFWS 2014e).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Sander lucioperca eggs may be transported on macrophytes and in substrate (FAO 2012).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 Sander lucioperca occurs in North Dakota (USFWS 2014e).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 

No, this species this species is rarely/never sold. 0 √

Unknown U

 Many think that S. lucioperca would benefit North American fisheries (USFWS 2014e). While not for sale, it 

would not be difficult to catch fish from North Dakota and transport them into the Great Lakes.
589

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0

Unknown U

 Many think that S. lucioperca would benefit North American fisheries (USFWS 2014e). 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U √

 Sander lucioperca would have to be transported from where it occurs in North Dakota (USFWS 2014e).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
590

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 Sander lucioperca eggs can survive salinities <5 ppm (Gröger et al. 2007).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
591

 Sander lucioperca is cultured in Sweden (Baltic Sea) (Abdolmalaki and Psuty 2007).

 This fish lives in coastal marine waters (catchment areas) of Baltic Sea and North Sea (FAO 2013b).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.25 25 Low

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x U U Unknown

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 1 Confidence Level Moderate
592

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Sander lucioperca has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Sander lucioperca have a tolerance for a wide range of salinities, water temperatures, and nutrient loads. 

They are already found in locations in Europe with more extreme temperatures and salinities than the 

Great Lakes which suggest that it would survive winter temperatures if introduced into the Great Lakes. S. 

lucioperca have demonstrated an ability to adapt to available prey sources. In other introduced lakes, S. 

lucioperca has become a top predator. This species is a nest guarder which offers it an advantage over 

other native fish that do not guard young. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 S. lucioperca lives in freshwater and brackish water with salinities <12 ppm (Abdolmalaki and Psuty 2007).

 This species inhabits water with temperatures ranging from <4-30°C (Çelik et al. 2005).

 S. lucioperca prefer deep, calm, temperate waters. This species is found in both clear and turbid waters but 

requires a high oxygen concentration (FAO 2012).

 This species inhabits productive, eutrophic waters in Europe (Kangur et al. 2007a).

 The preferred temperature for this species is 24-29°C (Hokanson 1977).

 S. lucioperca can tolerate salinities 29-32 psu after a gradual increase over 6 hours (Brown et al. 2001).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0
593

Unknown U

8

 This species has high abundance in Egirdir Lake (Turkey), which freezes over in January, and has water 

temperatures 4-5°C in December and February (Çelik et al. 2005).

 S. lucioperca inhabits Estonian lakes that are frozen November-April, and which may have an oxygen deficit 

under the ice (Kangur et al. 2007).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 S. lucioperca consumes arthropods (including isopods and insects) and fish (including cyprinids, percids, and 

salmonids) (Argillier et al. 2012).

 This species consumes zooplankton when young (Gröger et al. 2007).

 Pikeperch can change their prey selection relatively rapidly in response to changes in the abundance and 

vulnerability of prey species (Popova 1978).

 This species can adapt a planktivore diet during the first year if fish prey aren’t available, i.e., adapts an 

optimal foraging strategy (Persson and Brönmark 2008).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 Egirdir Lake is the second biggest natural fresh water lake in Turkey. S. lucioperca was stocked into Egirdir 

Lake in 1955. Other carp species evidently decreased and some species became extinct while S. lucioperca

population increased in subsequent years. Eventually, only carp, S. lucioperca, and crayfish fishing in the lake 

had commercial value (Çelik et al. 2005).
594

 S. lucioperca is a top predator in introduced habitats (France), i.e., preys on other predators (Kopp et al. 

2009).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

7

 The relative fecundity of this species averages between 150 and 400 eggs (Lappalainen et al. 2003).

 S. lucioperca has greater fecundity than walleye (Smith et al. 1998).

 European percids have total fecundity of 3000-1,185,000; maximum total fecundity of S. lucioperca recorded as 

2,500,000 (Collette et al. 1977).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 S. lucioperca is a nest guarder.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6
595

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 S. lucioperca has a very high climate match (USFWS 2014e).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 This species is favored in turbid waters, as they have visual adaptations to enhance foraging capacity (Ali et al. 

1977, Karås and Sandström 2002).

 Reproduction is impacted in high pollution: Total suspended solids in concentrations even below 25 mg · dm-3 

(the generally accepted threshold level) were found to inhibit fish embryogenesis by affecting fertilisation (% 

fertilisation: untreated, filtered riverine water and tap water: 75; 91; 85, respectively), perivitelline space 

formation, organogenesis, and hatching. The total suspended solids were also found to affect the larval size: the 

larvae hatched in water containing suspended particulates were smaller than those hatched in clean water; the

larval malformation rate was higher in the suspended solids-rich water than in clean water (Bonisławska 

2011).

 S. lucioperca inhabits water with temperatures from <4-30°C (Çelik et al. 2005).

 S. lucioperca prefers deep, calm, temperate waters. This species are found in both clear and turbid waters but 

require a high oxygen concentration (FAO 2012). 

 Inhabits productive, eutrophic waters in Europe (Kangur et al. 2007b).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Reproduction can occur in deep water, this species does not need macrophytes (Laurent et al. 1973).
596

 This species can inhabit a range of conditions: reservoirs with primarily artificial substrate with little habitat 

diversity and deep oligotrophic waters, and also shallow eutrophic reservoirs with macrophyte growth 

(Argillier et al. 2012).

 Within suitable habitat this species uses different microhabitats during different seasons. In the autumn they 

prefer waters with a depth of 1.2-1.8 m with a substrate made of large pebbles. They then move to much deeper 

waters where they spend the winter. Following this they migrate to shallower waters with a gravel/pebble 

substrate for spawning. Habitat preferences are more varied in the summer. Optimal conditions for egg 

development: water temperature between 12-20°C; high oxygen concentration (> 4.5 mg O2/l); low salinity <5 

ppm (FAO 2012).

 The spawning behaviour, nest building, guarding and care taking of the eggs has enabled the Pikeperch to 

expand its spawning sites into less oxygenated waters with silted or muddy bottoms (Balon et al. 1977).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Successive year-class strengths and growth rates in northern environments are also likely to increase as 

temperatures increase. Increases in both abundance and size are likely (Wrona et al. 2010).

 S. lucioperca can reproduce in salinity of <5ppm, increased salinization my favor this species over natives.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9
597

 S. lucioperca consumes arthropods (including isopods and insects) and fish (including cyprinids, percids, and 

salmonids) (Argillier et al. 2012).

 Pikeperch can change their prey selection relatively rapidly in response to changes in the abundance and 

vulnerability of prey species (Popova 1978).

 This species can adapt a planktivore diet during the first year if fish prey aren’t available, i.e., adapts an 

optimal foraging strategy (Persson and Brönmark 2008).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0
598

Unknown U

6

 Ruffe was the main prey item for S. lucioperca in a large lake in Estonia (Kangur et al. 2007b).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 This would depend on intentional movement for stocking purposes, or unintentional movement of eggs via 

recreational boats.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?
599

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 This species is native to the Caspian watershed, and in the basins of the Black, Azov, Aral and Baltic Seas 

(Craig 2000).

 Introduced into France, Finland (Archipelago Sea, Baltic Sea), Spain, Azores Islands, Belgium, Croatia, 

Denmark, Italy, Netherlands, Portugal, Slovenia, Switzerland, United Kingdom) and a range of other countries 

(Algeria, China, Kyrgyzstan, Morocco, Tunisia, Turkey, USA) (Argillier et al. 2012, Clavero and GarciaBerthou 2006, FAO 2012).

 Although it was thought that S. lucioperca stocked into a North Dakota lake for sport fishing did not survive 

(Anderson 1992b), the capture of a fish in August 1999, and another 2+ year old fish in 2000 shows that at 

least some survived and reproduced. Five young-of-the-year fish were collected in 2005. As of 2009, the state 

reports that they are established in Spiritwood Lake. The North Dakota Game and Fish Department reports 

capture of yearlings and 2-year olds, although they [say] the population is very small. Genetic sampling of fish 

has found that all are pure zander, there has been no hybridization. Spiritwood Lake is normally a closed basin, 

however it did flood several years ago (1998-2001) (USFWS 2014e).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 Pikeperch populations spread easily and can colonize neighboring waters provided there is relatively good 

access (Linfield and Rickards 1979).

 This species was introduced to a single canal in France in 1912, has since spread to most part of the 

hydrographic network (Argillier et al. 2012).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)
600

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 116

>100 High Adjustments

B. Critical species A*(1- 0%) 116

51-99 Moderate C. Natural enemy B*(1- 0%) 116

Control measures C*(1- 0%) 116

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Unknown

Beneficial: High

Sander lucioperca has the potential for high environmental impact if introduced to the Great Lakes.
601

When S. lucioperca was stocked into Egirdir Lake in 1955, other carp species evidently decreased and 

some species became extinct while S. lucioperca population increased in subsequent years. Eventually, 

only carp, S. lucioperca, and crayfish fishing in the lake had commercial value (Çelik et al. 2005). S. 

lucioperca can prey upon Brown Trout and Perch. This raises questions about the impact of S. lucioperca

introduction, which is suspected of being significant, on the stocks and exploitation of native species 

(Cowx 1997, Kershner et al. 1998, Smith et al. 1996, Smith et al. 1998). 

Current research on the potential for socio-economic impacts to result from Sander lucioperca if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine how Sander lucioperca would impact socioeconomics in the Great Lakes region. S. lucioperca is a top predator of Brown Trout, Perch and 

salmonids, and as such could impact commercial fisheries for these species. However, it is not known to 

what extent S. lucioperca could affect these commercial fisheries.

Sander lucioperca has the potential for high beneficial impact if introduced to the Great Lakes.

S. lucioperca has been commercially valuable since the 1920s, when it constituted about one-third of the 

total taken from the southern Caspian Sea. Due to overfishing and habitat degradation, it declined and has 

remained at low levels. In 2009, annual aquaculture production of Pikeperch exceeded 100 tonnes in three 

countries: Denmark, Tunisia and Ukraine. Total Pikeperch production in aquaculture (653 tonnes) in 2009 

was less than 5 percent of the level caught in open waters (14,739 tonnes). Stocking can yield the 

equivalent of an annual interest rate of 43% (based on capital invested in the stocked young of the year 

fish) (Hansson et al. 1997). A popular angling fish, with highly desired meat (Larsen and Berg 2011). 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Brabrand and Faafeng (1993) showed how young Roach shifted from pelagic to littoral habitats as a result of 

S. lucioperca introduction in a Norwegian lake. An indirect effect of the changed behaviour of Roach was 

increased infection rate of Roach with the ectoparasite Ichthyophthirius multifiliis, as Roach was more often 

exposed to the free swimming state of Ichthyophthirius multifiliis when living in shallow water near the 

substrate compared to their previously more pelagic lifestyle (Brabrand et al. 1994).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?
602

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Egirdir Lake is the second biggest natural fresh water lake in Turkey. S. lucioperca was stocked into Egirdir 

Lake in 1955. Other carp species evidently decreased and some species became extinct while S. lucioperca

population increased in subsequent years. Eventually, only carp, S. lucioperca, and crayfish fishing in the lake 

had commercial value (Çelik et al. 2005).

 S. lucioperca is a top predator in introduced habitats (France), i.e., preys on other predators (Kopp et al. 

2009).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 S. lucioperca can prey upon Brown Trout and Perch. This raises questions about the impact of S. lucioperca

introduction, which is suspected of being significant, on the stocks and exploitation of native species (Cowx 

1997, Kershner et al. 1999, Smith et al. 1996, Smith et al. 1998)..

 S. lucioperca is a top predator in introduced habitats (France), i.e., preys on other predators (Kopp et al. 

2009).

 Schulze et al. (2006) found that the Perch (Perca fluviatilis) population in a shallow, mesotrophic lake with 

natural occurrence of Perch and Pike (Esox lucius) were negatively affected by S. lucioperca introduction. In 

an experiment they showed that Perch was forced away from its preferred habitat, the pelagic zone, by S. 

lucioperca.

 Jeppesen et al. (2001) found evidence of reduced population densities of cyprinids in a paleolimnologic study in 

the Danish Lake Skanderborg, where S. lucioperca was introduced in 1903-04. After this a permanent reduction 

in cyprinid densities was found.

 Cowx (1997) found that introducing S. lucioperca to English rivers created a crash in the cyprinid fish 

community.

 In the Turkish Lake Egredir, S. lucioperca was introduced in 1955 and from 1961 it became an important 

species in commercial fisheries in the lake. The introduction also had the result that 5 out of 9 indigenous fish 

species disappeared, among these three species of Phoxinellus, two of which were endemic to Lake Egredir 

(Crivelli 1995). Consequently these two species must now be considered extinct worldwide.

 Denmark has shown that predation on smolts in the lower part of the river has an adverse effect on the 

population of sea-trout (Koed et al. 2002).
603

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 8

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
604

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 
605

Unknown U √

 This species is a top predator of Brown Trout, Perch and salmonids, and as such could impact commercial 

fisheries for these species.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U √

 This species is a top predator of Brown Trout, Perch and salmonids, and as such could impact recreational 

fisheries for these species.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT
606

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 

Unknown U √

 Ruffe was the main prey item for S. lucioperca in a large lake in Estonia (Kangur et al. 2007b).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 S. lucioperca has been commercially valuable since the 1920s, when it constituted about one-third of the total 

taken from the southern Caspian Sea. Due to overfishing and habitat degradation, it declined and has remained 

at low levels. In 1990, the Iranian government initiated a S. lucioperca stock enhancement program 

(Abdolmalaki and Psuty 2007).

 In 2009, annual aquaculture production of pike-perch exceeded 100 tonnes in three countries - Denmark, 

Tunisia and Ukraine. Total Pike-perch production in aquaculture (653 tonnes) in 2009 was less than 5 percent 

of the level caught in open waters (14,739 tonnes). Wholesale prices for Pike-perch fluctuate significantly but 

usually range from USD 5.6-12.5/kg (whole fish) with a mean of about ~USD 8.3/kg. In some countries, such as 

Germany and France, prices can be as high as USD 22.2/kg (FAO 2013b).

 Thanks to its low fat content (usually 1-2%) and highly assimilable protein, pike-perch meat is highly valued by 

dieticians (FAO 2013b).

 Stocking can yield the equivalent of an annual interest rate of 43% (based on capital invested in the stocked 

young of the year fish) (Hansson et al. 1997).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6 √

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0

Unknown U

 This species is a popular angling fish, with highly desired meat (Larsen and Berg 2011).

 Thanks to its low fat content (usually 1-2%) and highly assimilable protein, pike-perch meat is highly valued by 

dieticians (FAO 2013b).
607

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 12

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
608

Scientific Name: Silurus glanis 

Linnaeus, 1758

Common Name: Wels Catfish, Sheatfish, European Catfish

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unknown

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Silurus glanis has an unknown/low probability of introduction to the Great Lakes (Confidence 

level: Moderate).

Potential pathway(s) of introduction: Unauthorized Intentional Release

Siluris glanis is the largest freshwater fish in the world. Silurus glanis is reportedly robust to transport 

(Copp et al. 2009) but it is uncertain whether it is available for sale in the United States.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1
609

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 

Unknown U √

 Several hobbyist forums included posts by individuals seeking this fish, and one indicated they had Wels Catfish 

for sale in the United States (http://www.monsterfishkeepers.com/forums/showthread.php?224509-WelsCatfish-anyone-in-the-US-get-one). However, these claims cannot be verified, so this vector remains unknown. 

It is being sold in Europe (e.g., http://www.homersfieldlake.com/Fish_Farm.html).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1
610

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U √

 Several hobbyist forums included posts by individuals seeking this fish, and one indicated they had Wels Catfidh 

for sale in the United States (http://www.monsterfishkeepers.com/forums/showthread.php?224509-WelsCatfish-anyone-in-the-US-get-one). However, these claims cannot be verified, so this vector remains unknown. 

It is being sold in Europe (e.g., http://www.homersfieldlake.com/Fish_Farm.html).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?
611

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
612

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

U x U U Unknown

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
613

Silurus glanis has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

It is likely S. glanis would be able to survive in the Great Lakes since it tolerates a range of climates 

including many of the conditions found in the Great Lakes. Wels Catfish is able to adjust its diet based on 

availability of prey making it adaptable to Great Lakes food webs. This species is a nest guarder which 

gives it an advantage over other native fish that do not nest guard young.

This species would only be introduced through intentional release or escape from a stocked pond. 

However, this species is difficult to purchase in the United States, so these would be infrequent 

occurrences.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 S. glanis survives water temperatures 0-27°C, though success may be limited in lower water temperatures 

(Britton et al. 2007, David 2006).

 This species spawns at 18-22°C (Copp et al. 2009)

 S. glanis tolerates salinity up to 15 ppm (Copp et al. 2009).

 This species can inhabit eutrophic and turbid waters (Castaldelli et al. 2013).

 Wels Catfish is able to withstand prolonged periods of hypoxia (Massabuau and Forgue 1995).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8
614

 S. glanis inhabits waters 0-5°C (Britton et al. 2007).

 This species is able to withstand prolonged periods of hypoxia (Massabuau and Forgue 1995), due to high 

levels of hemoglobin (Copp et al. 2009).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 In a study performed by Carol (2009) Wels Catfish diet depended on site and catfish size. Catfish measuring 

less than 30 cm consumed mostly invertebrates, thereafter shifting to Red Swamp Crayfish (Procambarus 

clarkia) (old introductions) or fish (recent introductions). A number of fish species were present in stomachs but 

Common Carp (Cyprinus carpio) and birds were only present in very large fish (> 120 cm.

 It is well documented that Wels Catfish take advantage of its diet plasticity and ability to prey upon the most 

abundant available species of a suitable size within its habitat (Carol 2009, Castaldelli et al. 2013, Martino et 

al. 2011, Syväranta et al. 2010)..

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 There is limited data, but Wels Catfish is considered abundant where introduced on the Iberian peninsula 

(Carol et al. 2007).

 In the Po River basin in 1991, Wels Catfish accounted for 6.1% of the total biomass. With optimal foraging 

conditions, abundant prey, and few competitors, it reached 77%, 71%, and 62% of the overall biomass in 1997, 

2003, and 2009, respectively (Castaldelli et al. 2013).

 This species has remained rare in the River Thames (Copp 2007).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?
615

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 The absolute fecundity of female S. glanis ranges from 14 600 to 354 000 eggs (Copp et al. 2009).

 Relative fecundity (eggs per kg body weight) of siluroid species is as follows (Legendre et al. 1996): 

o Silurus glunis: 10,000-25,000

o Guleichthys feliceps: 50,000

o lctalurus punctutus: 8,000

o Chtysichthys nigrodigitaius: 15,000-18,000

o Hoplosternum littorale: 45,000-75,000

o Clarias gariepinus: 60,000-150,000

o Clarias macrocephalus: 20,000-50,000

o Heterobranchus longifilis: 30,000-120,000

o Pseudoplatystoma coruscans: 120,000-130,000

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 S. glanis is a nest guarder (Copp et al. 2009).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6
616

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 S. glanis native distribution extends from Germany eastwards through to Poland, up to Southern Sweden and 

down to Southern Turkey and north Iran stretching through the Baltic States to Russia (Greenhalgh 1999) and 

to the Aral Sea of Kazakhstan and Uzbekistan (Copp et al. 2009, Phillips and Rix 1988)..

 This range of climates include many of the conditions found in the Great Lakes.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 High levels of hemoglobin also make Wels Catfish relatively tolerant of pollution (Lelek 1987).

 This species has a well-developed non-visual sensors make it well adapted to waters with low visibility (Copp et 

al. 2009).

 S. glanis survives water temperatures 0-27°C, though success may be limited in lower water temperatures 

(Britton et al. 2007, David 2006).

 This species can inhabit eutrophic and turbid waters (Castaldelli et al. 2013).

 Wels Catfish is also able to withstand prolonged periods of hypoxia (Massabuau and Forgue 1995).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 S. glanis inhabits the lower reaches of large rivers and muddy lakes (Alp et al. 2011)

 Wels Catfish individuals are usually strongly associated with areas with a high density of woody debris, 

boulders, low flow and tree roots (Abdullayev et al. 1978). The species, therefore, appears to prefer large water 

bodies with cryptic habitat (Britton et al. 2007). 
617

 Wels Catfish has thrived in degraded habitats (Italy), i.e., canals that were eutrophic and turbid, without 

morphological complexity, and with sparse vegetation (Castaldelli et al. 2013).

 The species is normally encountered throughout their range in large rivers, lakes and coastal areas of low 

salinity (<15 ppm). Primarily a fish of rich, weedy lakes and slow, deep lowland rivers, in its native range, the 

species is known to shift during their first year of life into mid channel habitats (Wolter and Vilcinskas 1996,

Wolter and Freyhof 2004), which are important for reproduction and habitat partitioning between different age 

groups (Wolter and Bischoff 2001). However, the preferred habitat of S. glanis is still waters (Greenhalgh 

1999, Wheeler 1969). During winter, it hibernates in rivers in deep holes, dens and crevices in the bed; in lakes, 

it lies in the lower third of the water column or on soft mud (Copp et al. 2009, Lelek et al. 1964, Lelek 1987)..

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

7

 S. glanis maximum growth occurs at 25-27°C, so warming waters would benefit this species (David 2006).

 It can withstand low salinity, so it may be able to outcompete native species limited to freshwater if salinization 

increases (Copp et al. 2009).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 This species consumes whatever is most abundant, from crustaceans to fish (Castaldelli et al. 2013).
618

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
619

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 This species would only be introduced through intentional release, or escape from a stocked pond. However, 

this species is difficult or impossible to purchase in the US, so these would be infrequent occurrences.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U
620

7

 Wels Catfish is native to eastern Europe and western Asia. This species has been introduced to many European 

countries, including France, Italy, the Netherlands, Spain and the United Kingdom due to its popularity among 

anglers (Alp et al. 2011, Bănărescu 1989, Britton et al. 2007, Carol et al. 2007, Carol 2009, Copp et al. 2009,

Krieg et al. 2000). This includes intentional, unauthorized introduction (Pérez-Bote 2009).

 This species is farmed in Austria, Bulgaria, Croatia, Czech Republic, France, Hungary, Greece, Macedonia, 

Poland, and Romania (Linhart et al. 2002)

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 This species has spread rapidly though human introductions, but slowly via natural dispersal (Copp et al. 

2009).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 93
621

>100 High Adjustments

B. Critical species A*(1- 0%) 93

51-99 Moderate C. Natural enemy B*(1- 0%) 93

Control measures C*(1- 0%) 93

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: High

Silurus glanis has the potential for high environmental impact if introduced to the Great Lakes.

S. glanis has an association with several parasites that can have an impact on wild populations.

In early stage invasion sites, S. glanis mainly consumed fish because of a high abundance of small 

cyprinid species, such as Roach and Bleak (Carol et al. 2007). In contrast, crayfish was the main prey of 

Wels Catfish in advanced stage invasion sites and the ontogenetic shift to piscivory was delayed until the 

catfish grew larger. Accordingly, these advanced stage invasion reservoirs had size structures dominated 

by larger sizes of Common Carp. Although further data are needed to see how frequent these patterns are, 

results from Carol (2009) strongly suggest that at the early stages of invasion, catfish grow faster and are 

in better condition because they prey more on fish. As invasion proceeds, however, the catfish reduce fish 

numbers, particularly of smaller fish, indirectly favoring crayfish and eventually resulting in their own 

reduced growth rates (Carol 2009).

In addition to fish prey, another likely ecological impact of Wels Catfish is on some groups of waterbirds, 

especially in the Anatidae family. Few birds have been observed in the catfish stomach contents 

(Czarnecki et al. 2003, Omarov and Popova 1985). Carol (2009) also found that waterbird abundance 

varied significantly with the invasion sequence (advance stage correlated with lower bird abundance) and 

this was not due to correlation or confounding with abiotic factors (such as reservoir size, altitude or 

trophic state) (Carol 2009). The significantly lower abundance of waterbirds in reservoirs with Wels 
622

Catfish could be due to either a direct ecological impact (predation) by Wels Catfish and/or to avoidance 

behavior by waterbirds to reduce predation risk (Carol 2009).

It is well documented that Wels Catfish take advantage of its diet plasticity and ability to prey upon the 

most abundant available species of a suitable size within its habitat (Carol 2009, Martino et al. 2011, 

Syväranta et al. 2010). Wels Catfish may adapt foraging behaviors in new habitats and introduced 

populations have started breaching onto shores to capture birds on land (Cucherousset et al. 2012, 

Syväranta et al. 2010).

There is little or no evidence to support that Silurus glanis has the potential for significant socioeconomic impacts if introduced to the Great Lakes.

It has not been reported that Silurus glanis poses a threat to human health or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits.

Silurus glanis has the potential for high beneficial impact if introduced to the Great Lakes.

The Wels Catfish has an economic importance in commercial and recreational fisheries as well as in 

aquaculture. Its aquaculture production has increased from 600 tonnes in 1993 to 2,000 tonnes in 2002 in 

ten European countries (Copp et al. 2009, Linhart et al. 2002). Silurus glanis is considered a delicacy in 

some countries (Hungary, Poland, Slovakia, Lithuania), where it is exploited for its flesh (tender white 

meat), skin (for leather and glue production), and eggs (for caviar) (Copp et al. 2009). The popularity of 

S. glanis relates to the large sizes they can reach; they are perceived as an attractive big-game species by 

many United Kingdom anglers (Hickley and Chare 2004). 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 S. glanis has several associated parasites (Copp et al. 2009):

o Myxobolidae can have a significant pathological impact on wild and cultured fishes, and such 

episodes are often preceded by environmental stressors such as oxygen depletion of the water 

(Lom and Dykova 1992). 

o Acanthocephalans (e.g. L. plagicephalus) can cause extensive damage such as lesions to the 

intestinal tract of fish where they attach leading secondarily to infections by bacteria (Dezfuli et 

al. 1990). 
623

o High intensities of parasitic crustaceans such as Ergasilus sieboldi can inflict severe damage to 

the gills (Dezfuli et al. 2003) resulting in large scale mortalities of fish (Kabata 1979).

 Further introductions of S. glanis may extend the distribution of specialist species such as Trichodina siluri, M. 

miyarii, L. plagicephalus and Pseudotracheliastes stellifer, the latter of which may have pathogenic potential as 

its congener, P. stellatus, is known to be pathogenic to sturgeons (Bauer et al. 2002, Copp et al. 2009).

 European sheatfish virus (ESV) is known to affect S. glanis only, though little work has been done to establish 

the susceptibility of other species. ESV was identified by Copp et al. (2009) as the pathogen of most concern.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

 No evidence of competition was found.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 The differences in condition and growth rates between recent and older introductionsof Wels Catfish may be 

related to diet. In early stage invasion sites, Wels Catfish mainly consumed fish because of a high abundance of 

small cyprinid species, such as Roach and Bleak (Carol et al. 2007). In contrast, crayfish was the main prey of 

Wels Catfish in advanced stage invasion sites and the ontogenetic shift to piscivory was delayed until the catfish 

grew larger. Accordingly, these advanced stage invasion reservoirs had size structures dominated by larger 

sizes of Common Carp. Although further data are needed to see how frequent these patterns are, our results 

strongly suggest that at the early stages of invasion, catfish grow faster and are in better condition because they 

prey more on fish. As invasion proceeds, however, the catfish reduce fish numbers, particularly of smaller fish, 

indirectly favoring crayfish and eventually resulting in their own reduced growth rates (Carol 2009).

 In addition to fish prey, another likely ecological impact of catfish is on some groups of waterbirds, especially 

in the Anatidae family. Few birds have been observed in the catfish stomach contents (Czarnecki et al. 2003, 

Omarov and Popova 1984). Carol (2009) found that waterbird abundance varied significantly with the 

invasion sequence (advance stage correlated with lower bird abundance) and this was not due to correlation or 

confounding with abiotic factors (e.g. reservoir size, altitude or trophic state) (Carol 2009). The significantly 

lower abundance of waterbirds in reservoirs with catfish could be due to either a direct ecological impact 

(predation) by Wels Catfish and/or to avoidance behavior by waterbirds to reduce predation risk (Carol 2009).
624

 Data from Castaldelli et al. (2013) showed a clear temporal gradient in fish community structure. After the 

establishment of the exotic predator Silurus glanis, some native species significantly declined in abundance and 

biomass (i.e. Alburnus arborella and Scardinius erythrophthalmus) or disappeared (i.e. Rutilus aula and Tinca 

tinca). It is well documented that Wels Catfish takes advantage of its diet plasticity and ability to prey upon the 

most abundant available species of a suitable size within its habitat (Carol 2009, Martino et al. 2011, Syväranta 

et al. 2010). This may have contributed to the sequence of the decline in species. Among the most abundant 

native species in 1991, Tench and Italian Red-eye Roach were the first to disappear, with none captured in 

2003. These are small fish with a marked benthic lifestyle. The population of Italian Bleak and Rudd, which 

differ from the abovementioned species in having fewer marked benthic traits, decreased more slowly, and they 

were still present in 2009, although greatly reduced (Castaldelli et al. 2013).

 Wels Catfish may adapt foraging behaviors in new habitats, e.g., introduced populations have started breaching 

onto shores to capture birds on land (Cucherousset et al. 2012, Syväranta et al. 2010).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U
625

Environmental Impact Total 6

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6
626

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
627

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √

Not significantly 0 

Unknown U

 S. glanis has been introduced to regulate cyprinid fish numbers in the Netherlands, where it escaped and 

dispersed to other waters (Copp et al. 2009).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 √

Yes, but its economic contribution is small 1

Not significantly 0 

Unknown U

 The Wels Catfish has an economic importance in commercial and recreational fisheries as well as in 

aquaculture. Its aquaculture production has increased from 600 tonnes in 1993 to 2,000 tonnes in 2002 in ten 

European countries (Copp et al. 2009, Linhart et al. 2002).

 This species is considered a delicacy in some countries (e.g. Hungary, Poland, Slovakia, Lithuania), where it is 

exploited for its flesh (tender white meat), skin (for leather and glue production) and eggs (for caviar) (Copp et 

al. 2009).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 The popularity of S. glanis relates to the large sizes they can reach; they are perceived as an attractive biggame species by many United Kingdom anglers (Hickley and Chare 2004).
628

 Not a species of interest in Italy (Castaldelli et al. 2013).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 8

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
629

0 ≥2

Unknown

1 ≥1
630

Scientific Name: Syngnathus abaster

Risso, 1827

Common Name: Black-striped Pipefish, Shortsnouted Pipefish

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Syngnathus abaster has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Ballast water exchange is predicted to have a low effectiveness for Syngnathus abaster, as it has high 

salinity tolerances (Snyder et al. 2014). This suggests that it could survive transportation via ballast water 

for introduction into the Great Lakes. This species is not extremely abundant so the frequency of ballast 

uptake is likely small.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 The original S. abaster distribution area includes coastal habitats and the lower reaches of rivers of the 

Caspian, Azov, Black, and Mediterranean Sea basins, as well as the Atlantic coast from Gibraltar to the 

southern Bay of Biscay (Kottelat and Freyhof 2007). During the 20th century, this fish species expanded its 
631

range upstream in the rivers Danube, Dniester, Dnieper, Don, and Volga (Bogutskaya and Naseka 2002b,

Cakić et al. 2002, Movchan 1988) as well as Lake Bafa in Turkey (Sarı et al. 1999).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U 

 As a large (~15 cm) fish, S. abaster is not likely to adhere or be transported.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 An online search for this species did not yield any for sale. 
632

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 There is no indication that S. abaster occurs naturally in North America or that there would be any interest 

stocking.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U
633

 There is no record either in the literature or online of S. abaster of being commercially cultured or transported.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Ballast water exchange is predicted to have a low effectiveness for this species, as it has high salinity tolerances 

(Snyder et al. 2014).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

No, this species does not occur in waters from which shipping traffic to the Great Lakes Score x 0
634

originates.

Unknown U

 The original S. abaster distribution area includes coastal habitats and the lower reaches of rivers of the 

Caspian, Azov, Black, and Mediterranean Sea basins, as well as the Atlantic coast from Gibraltar to the 

southern Bay of Biscay (Kottelat and Freyhof 2007). During the 20th century, this fish species expanded its 

range upstream in the rivers Danube, Dniester, Dnieper, Don, and Volga (Bogutskaya and Naseka 2002a and 

2002b, Cakić et al. 2002, Movchan 1988) as well as Lake Bafa in Turkey (Sarı et al. 1999).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0.5 50 Moderate

Total Unknowns (U) 0 Confidence Level High
635

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Syngnathus abaster has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

The Great Lakes include a large amount of the preferred habitat for Syngnathus abaster (muddy vegetated 

bottoms with slow current). The wide distribution of this species in heavily-disturbed rivers of Europe 

indicates it would tolerate pollution and other disturbances, which are found in various parts of the Great 

Lakes.

Syngnathus abaster prefer harpaciticoids of the genus Tisbe; several harpacticoid copepods from Eurasia 

have been introduced into the Great Lakes. In addition to this, there are no reported enemies in either its 

native or introduced range; however, it is a slow-moving species so it may be vulnerable to predation by 

larger fish, such as salmon and trout.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 This species is euryhaline and can survive in marine, fresh, and brackish water (Dawson 1986).

 S. abaster can survive in a wide range of temperature between 8° to 24°C (Dawson 1986), has been recorded in 

water from 4° to 5.5°C (Franzoi et al. 1993).

 This species lives among sand-, mud-, or seagrass beds between depths of 0.5m and 5 m (Dawson 1986), 

though muddy vegetated habitat with slow current preferred (Ondračková et al. 2012b).

 The Black-striped Pipefish has a high salinity tolerance (>28 ppt) across all life history stages (Snyder et al. 

2014)

 This species has suceesfully established in freshwater habitats (Tutman et al. 2012)

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?
636

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U 

8

 This species survisies in a wide range of temperature between 8° to 24°C (Dawson 1986), has been recorded in 

water from 4° to 5.5°C (Franzoi et al. 1993)

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 The most important food item for S. abaster are harpaciticoids of the genus Tisbe, though phytal amphipods and 

other phytal organisms also contribute to its diet (Franzoi et al. 1993). 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Where this species has spread in the River Danube, it represents 3.7% of all fish collected (Ondračková et al. 

2012b). 

 The species has invaded areas with high diversity of ichthyofauna (Lenhardt et al. 2011).
637

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 This species produces twice as many eggs as the congener S. taenionotus and has four broods per reproductive 

season as opposed to two (Franzoi et al. 1993). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

5

 Reproductive strategy by S.abaster, in which the males carry eggs and larvae in brood pouches, make it more 

likely the early life history stages of Balck-striped Pipefish can survive harsh environments (Snyder et al. 2014).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0
638

Unknown U

4

 This species is found at range of latitudes, including the Dneiper River near Kiev, Ukraine, 50°N (Tutman et al. 

2012), so will likely experience similar climatic conditions.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 This species can survive a wide range of temperature between 8° to 24°C (Dawson 1986), has been recorded in 

water from 4° to 5.5°C (Franzoi et al. 1993).

 The Great Lakes include a large amount of the preferred habitat (muddy vegetated bottoms with slow current). 

 The wide distribution of this species in heavily-disturbed rivers of Europe indicate it would tolerate pollution 

and other disturbances.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 This species can survive a wide range of temperature between 8° to 24°C (Dawson 1986), has been recorded in 

water from 4° to 5.5°C (Franzoi et al. 1993)

 This species lives among sand-, mud-, or seagrass beds between depths of 0.5 and 5 m (Dawson 1986), though 

muddy vegetated habitat with slow current preferred (Ondračková et al. 2012b)

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

9
639

changes due to its wide environmental tolerances)

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 This species survives a wide range of temperature between 8° to 24°C (Dawson 1986), has been recorded in 

water from 4° to 5.5°C (Franzoi et al. 1993). As such, moderate water temperature increases are likely to 

benefit this species.

 As a euryhaline species, increased salinization may give it competitive superiority over freshwater-only species.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 The most important food item for this species are harpaciticoids of the genus Tisbe, though phytal amphipods 

and other phytal organisms also contribute to its diet (Franzoi et al. 1993). There are over 34 harpaciticoids 

species in the Great Lakes area (Hudson et al. 1998).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 3
640

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No information was found in required to requiring another species for a critical stage in its life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

2

 Several harpacticoid copepods from Eurasia have been introduced into the Great Lakes (Kitokra hibernica and 

N. incerta).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the -10% total 
641

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 No enemies have been mentioned in the native or introduced range; however as a slow-moving species it may 

be vulnerable to predation by larger fish such as salmon and trout.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 Average brood size ~100 eggs, so inocula would be small. This species is not extremely abundant so the 

frequency of ballast uptake is likely small.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 During the 20th century, this fish species expanded its range upstream in the rivers Danube, Dniester, Dnieper, 

Don, and Volga (Bogutskaya and Naseka 2002, Cakić et al. 200, Movchan 19882).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?
642

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

8

 This species is likely to have extensive natural spread, over 100s of kilometers (Lenhardt et al. 2011, 

Ondračková et al. 2012b).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0
643

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 91

>100 High Adjustments

B. Critical species A*(1- 0%) 91

51-99 Moderate C. Natural enemy B*(1- 10%) 81.9

Control measures C*(1- 0%) 81.9

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Syngnathus abaster if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Syngnathus abaster poses as threat to 

other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Syngnathus abaster has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Syngnathus abster poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the area it inhabits.

There is little or no evidence to support that Syngnathus abaster has the potential for significant 

beneficial impacts if introduced to the Great Lakes.
644

It has not been reported that Syngnathus abster can be used for the control of other organisms or 

improving water quality. There is no evidence that this species is commercially, recreationally, or 

medically valuable. It does not have a significant positive ecological impact.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Black-striped Pipefish have been predicted to have negative impacts due to proxies such as history of invasion, 

small egg diameters and low minimum temperatures (Snyder et al. 2014).

 There was very little mention of impact in the literature. It has been described as "without apparent impact" 

(Lenhardt et al. 2011)

 It has been found to carry 17 parasites in native range, though only one has been found in freshwater habitats 

where S. abaster has been introduced.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 1 
645

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √
646

Environmental Impact Total 1

Total Unknowns (U) 5

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U 

 There is no information on disease or parasite transmission by this species to humans.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U 

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6 
647

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U 

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
648

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 Considered a 'discard' fish of no economic importance (Pranovi et al. 2013)

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 No information was found in regards to its recreational value

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?
649

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
650

A.2 Bivalves 

Scientific Name: Limnoperna fortunei

Dunker, 1857

Common Name: Golden Mussel

Synonyms: Limnoperna siamensis, Limnoperna lacustris

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Limnoperna fortunei has a low probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping

Limnoperna fortunei has a high tolerance to fluctuating salinities; no significant mortality was observed 

in mussels exposed to a salinity cycle with abrupt salinity changes ranging 1–23% (mean 2.68%) over a 

month (Sylvester et al. 2013). This will affect probability of uptake (many ports located in estuarine 

environments with fluctuating salinity) and survival after ballast exchange (Sylvester et al. 2013). Though 

tolerance of larvae has not been specifically examined, larval survival is likely due to presence of colonies 

in saline regions (unlikely formed by drifting adults) (Sylvester et al. 2013). Though little to no ship 

traffic arrives to the Great Lakes from South American or Asian ports, the potential exists.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 √
651

not mobile or able to be transported by wind or water.

Unknown U

 This species does not occur near waters connected to the Great Lakes basin.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 The Golden Mussel may have been introduced to Japan as contaminant of shipments of live Asian clams from 

China (Crosier and Molloy 2004, Ghabooli et al. 2013, Magara et al. 2001), but Asian clams are not known to 

be shipped to the Great Lakes region.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
652

No, this species this species is rarely/never sold. 0 √

Unknown U

 The Golden Mussel is not sold or available for purchase in the Great Lakes basin.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 The Golden Mussel is not stocked or planted in the Great Lakes basin.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100
653

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There is no commercial culture of transport of Golden Mussel in the Great Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Limnoperna fortunei has a high tolerance to fluctuating salinities; no significant mortality was observed in 

mussels exposed to a salinity cycle with abrupt salinity changes ranging 1–23 % (mean 2.68 %) over a month 

(Sylvester et al. 2013). Tolerance to this type of regime was unaffected by different temperatures within ambient 

ranges, and survival was 90% over 9 hours (Sylvester et al. 2013). In terms of the distance covered by a 

commercial vessel typically sailing at 13–24 knots (24–44 km/h), 9 h represents anywhere between 217 and 400 

km, which in many areas exceeds the distance between the destination port and the site of mid-ocean exchange 

(Sylvester et al. 2013).

 This will affect probability of uptake (many ports located in estuarine environments with fluctuating salinity) 

and survival after ballast exchange (Sylvester et al. 2013). Though tolerance of larvae has not been specifically 

examined, larval survival is likely due to presence of colonies in saline regions (unlikely formed by drifting 

adults) (Sylvester et al. 2013).
654

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Though little to no ship traffic arrives to the Great Lakes from South American or Asian ports, the potential 

exists.

Scoring

Points (per vector) Probability for Introduction

80-100 High

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 8 Low

Total Unknowns (U) 0 Confidence Level High
655

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Limnoperna fortunei has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Limnoperna fortunei can survive salinity shocks and changes allowing it transportation into the Great 

Lakes and the ability to acclimate to salinities around the Great Lakes. This species is already found in 

regions with climates similar to the Great Lakes and shows the ability to survive overwinter temperatures 

as low as 0°C. L. fortunei consumes a variety of phytoplankton and zooplankton making it able to adjust 

its diet based on prey availability in the Great Lakes if introduced.

The native and introduced ranges of L. fortunei include extremes of pollution, water temperature, pH, and 

nutrient levels, making it able to adapt to the many microhabitats throughout the Great Lakes. 

Limnoperna fortunei attaches well to hard substrate (including of biological origin), minimally to soft 

substrate, as well as macrophytes and reeds (Karatayev et al. 2007) and plastic bottles (Karatayev et al. 

2010). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 The Golden Mussel can survive (90%) up to a salinity shock of 2 ppt for periods of at least 10 days (Angonesi et 

al. 2008).
656

 This species has a high tolerance to fluctuating salinities; no significant mortality was observed in Golden 

Mussels exposed to a salinity cycle with abrupt salinity changes ranging 1–23 % (mean 2.68 %) over a month. 

Tolerance to this type of regime was unaffected by different temperatures within ambient ranges (Sylvester et al. 

2013).

 Deaton et al. (1989) had 41% Golden Mussel survival in 800mOsm (seawater ~1000mOsm) water.

 Compared to Dreissena polymorpha, Limnoperna fortunei has higher resistance to anoxia, pollution (including 

eutrophication), pH, and high temperatures, longer reproduction periods and lower calcium requirements (3-

4mg/L) (Karatayev et al. 2007). This broader tolerance indicates this species could have an even broader 

distribution in the Great Lakes than D. polymorpha.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 This species overwinters in South Korea, with water temperature as low as 0°C (Oliveira et al. 2010). In 

Japan, minimum temperature in a reservoir with Golden Mussels was 4.2°C (Nakano et al. 2011)

 Experimental research supports the 5°C threshold for prolonged exposure (Oliveira et al. 2010)

 Based on broad thermal tolerances, Ricciardi (1998) predicts colonization into the lower North American 

Great Lakes.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 L. fortunei consumes a variety of phytoplankton and zooplankton (Frau et al. 2013, Rojas Molina 2012, Rojas 

Molina et al. 2010). Adults do well despite low food availability (Oliveira et al. 2010).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9
657

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 This species negatively effects burrowing invertebrates and unionids (Karatayev et al. 2010) in South America, 

and may do the same in the Great Lakes given if in high densities. Such competitive exclusion is also seen in a 

similar species, D. polymorpha.

 This species may have outcompeted/overgrown the native gastropods in South America, Chilina fluminae and 

Biomphalaria straminea, as they became rare and eventually disappeared from study sites (Spaccesi and 

Capitulo 2012).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

7

 No data was found on natural L. fortunei fecundity, though very high rates of colonization suggest it is high 

(Karatayev et al. 2007). 

 In the laboratory, it is similar to D. polymorpha (~11,000 eggs) (Cataldo and Boltovskoy, unpublished data in 

Karatayev et al. 2007).

 L. fortunei spawns continually, while D. polymorpha is a batch spawner, which may contribute to the former's 

success (Boltovskoy et al. 2006).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

3
658

establishment in the Great Lakes based on these attributes)

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 L. fortunei spawns continually (Boltovskoy et al. 2006).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 While the climate in South America is quite mild, South Korea climate is similar to the Great Lakes. South 

Korea has a humid continental climate and a humid subtropical climate. Winters can be extremely cold with the 

minimum temperature dropping below −20 °C (−4 °F) in the inland region of the country: in Seoul, the 

average January temperature range is -7 to 1 °C (19 to 34 °F), and the average August temperature range is 22 

to 30 °C (72 to 86 °F).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 Levels of these abiotic factors are very similar between the Great Lakes and the native/introduced ranges. That 

is, like the Great Lakes, the native/introduced ranges include extremes of pollution, water temperature, pH and 

nutrient levels. Salinity is similar (or more extreme) in native/introduced habitats. Notably, L. fortunei inhabits 

heavily polluted areas, as well as water with low calcium (3-4mg/L). 
659

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 L. fortunei reproduction was triggered at 17°C in a study performed by Nakano et al. (2011).

 This species has a depth range of a few centimeters to 10m (Karatayev et al. 2010). 

 This species attaches well to hard substrate (including of biological origin), minimally to soft substrate, as well 

as macrophytes and reeds (Karatayev et al. 2007) and plastic bottles (Karatayev et al. 2010).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 This species can withstand very warm temperatures, as well as low levels of salinization.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0
660

Unknown U

9

 This species consumes a variety of phytoplankton and zooplankton (Frau et al. 2013, Rojas Molina 2012, Rojas 

Molina et al. 2010).. Adults do well despite low food availability (Oliveira et al. 2010).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0
661

Unknown U

8

 As L. fortunei can settle on biogenic substrate, the presence of dead shells from D. polymorpha and D. bugensis

will likely facilitate establishment and spread by providing hard substrate.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 While L. fortunei is preyed upon by fish, there is no evidence of prevention or mitigation of colonization in 

other areas (Molloy et al. 1997, Sylvester et al. 2005).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 With little traffic from South America or Asia into the Great Lakes, the inoculation potential would be small.

HISTORY OF INVASION AND SPREAD
662

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 This species was introduced into Hong Kong in 1965 and into Taiwan, Japan, and Argentina around 1990, in 

the latter case most probably through the Rio de la Plata estuary via ship’s ballast water (Boltovskoy et al. 

2009). It has since colonized practically the entire Rı ́o de la Plata Catchment, including parts of Bolivia, 

Paraguay, Uruguay and Brazil (Paolucci et al. 2010).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 This species was introduced into Argentina around 1990, and by the early 2000s L. fortunei had colonized 

practically all of the Rıo de la Plata watershed extending to Paraguay, Brazil, Uruguay, and Bolivia, and 

swiftly became the sole dominant organism on hard substrates (Boltovskoy et al. 2006).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)
663

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 109

>100 High Adjustments

B. Critical species A*(1- 0%) 109

51-99 Moderate C. Natural enemy B*(1- 0%) 109

Control measures C*(1- 0%) 109

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: High

Limnoperna fortunei has the potential for high environmental impact if introduced to the Great 

Lakes.

Limnoperna fortunei reach large densities (5000-250,000 individuals/m2 on hard substrate, and 90-2000 

individuals/m2 on soft substrate (Frau et al. 2013); shifting productivity in the nutrient cycle from the 

pelagic zone to the benthic zone. This species filters water quickly clarifying water causing a reduction in 

primary production occurring within the water column. Nutrient concentrations and proportion are shifted 

to promote aggregation of solitary Microcystis spp. cells; this favors blooms of the noxious cyanobacteria 

(Cataldo et al. 2012a).
664

Limnoperna fortunei has the potential for high socio-economic impact if introduced to the Great 

Lakes.

L. fortunei modifies nutrient concentrations and proportions, and promotes aggregation of solitary 

Microcystis spp. cells into colonies; both these effects can favor blooms of this often noxious 

cyanobacteria (Cataldo et al. 2012a). Gazulha et al. (2012) found that while single cells of cyanobacteria 

were accepted, filamentous and colonial cyanobacteria were rejected as pseudofeces, a preference that 

could enhance blooms.

Limnoperna fortunei can clog fouling water intake sieves and filters, pipes, heat exchangers, and 

condensers has become a common difficulty in industrial and power plants that use raw water, chiefly for 

cooling purposes (Boltovskoy et al. 2009, Cataldo et al. 2003, Goto 2002).

Limnoperna fortunei has the potential for high beneficial impact if introduced to the Great Lakes.

Limnoperna fortunei has had similar impacts to Dreissena polymorpha, i.e., has led to a dramatic shift in 

the benthic trophic structure and a homogenization of freshwater communities, regardless of original 

substrate and community structure (Burlakova et al. 2012, Darrigran and Damborenea 2011, Sardiña et al. 

2011). Also, this species has led to an increase in water transparency, a decrease in suspended matter, 

chlorophyll a, and primary production (Boltovskoy et al. 2009). The structure of functional feeding 

groups in the new community, including invasive bivalves, is overwhelmingly dominated by collectorsfilterers (Burlakova et al. 2012).

Parallels with the Dreissena polymorpha highlight several important differences, including Limnoperna

fortunei’s higher resistance to anoxia, pollution, pH, and high temperatures, longer reproduction periods 

and lower calcium requirements (Karatayev et al. 2007), suggesting that, should Limnoperna fortunei

reach North America or Europe, it will become an even more aggressive invader, especially in regions 

dominated by acidic, soft and contaminated waters (Boltovskoy et al. 2009).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U

 In a mesocosm experiment, cell density, proportion of colonial cells and colony size of Microcystis spp. 

increased in all enclosures, but these increases were dramatically (and very significantly) higher in enclosures 
665

with 100 and, especially, with 300 Golden mussels, than in the controls. Enclosure density reflected realistic 

densities. The results indicated that L. fortunei modifies nutrient concentrations and proportions, and promotes 

aggregation of solitary Microcystis spp. cells into colonies; both these effects can favor blooms of this often 

noxious cyanobacteria (Cataldo et al. 2012a).

 Mechanisms through which this can occur may include: (i) modification of nutrient concentrations and the N : 

P ratio, (ii) selective grazing of solitary Microcystis spp. cells over colonial ones and (iii) production of 

chemical cues that trigger the formation of colonies (Boltovskoy et al. 2009).

 Gazulha et al. (2012) found that while single cells of cyanobacteria were accepted, filamentous and colonial 

cyanobacteria were rejected as pseudofeces, a preference that could enhance blooms.

 L. fortunei may also biomagnify contaminants, i.e., the pseudofeces that primarily consist of rejected 

contaminants are consumed by amphipods (Sardiña et al. 2011).

 This species has been found to attach to a native crab, Trichodactylus borellianus, which leads to higher 

energetic costs for locomotion and reduces ability to escape predators (Rojas Molina and Williner 2013).

 Another potential threat posed by this invader was reported by Ogawa et al. (2004). The authors identified 

widespread parasitic infections by bucephalid trematodes in several cyprinid fishes from the Uji river (Japan), 

suggesting that the infections started with the accidental introduction of infested first intermediate hosts 

(Limnoperna fortunei) (Ogawa et al. 2004).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 This species may outcompete/overgrow the native South American gastropods, Chilina fluminae and 

Biomphalaria straminea, as they became rare and eventually disappeared from study sites (Spaccesi and

Capitulo 2012).

 This species negatively effects burrowing invertebrates and unionids (Karatayev et al. 2010).

 This species negatively impacts zooplankton, and part of zooplankton decline may be due to starvation (i.e., 

mussel outcompetes zooplankton for food resources) (Rojas Molina 2012).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U 

 L. fortunei has increased food availability in the benthic zone, which in part has increased invertebrate 

(excluding mussels) density 1.9 to 22 times and biomass 1.7 to 19 times (Burlakova et al. 2012). 
666

 Karatayev et al. (2010) found a threefold increase in benthic invertebrate density and biomass.

 This species has homogenized benthic communities (Darrigran and Damborenea 2011, Sardiña et al. 2011); 

e.g., in one study 99.9% of community biomass consisted of the filtering collector trophic group (Burlakova et 

al. 2012)

 L. fortunei has shunted the dominant nutrient cycling from the pelagic to the benthic zone (Cataldo et al. 2012b, 

Darrigran and Damborenea 2011, Rojas Molina 2012).

 This species has been found to significantly reduced phytoplankton densities (>60%). Also, it has changed 

composition of the algae assemblages, most notably an increase in the flagellate group, relative to the diatom, 

single celled and colonial groups (Frau et al. 2013).

 Phytoplankton decreased 55-90% in mesocosm experiment with Gloden Mussel (Rojas Molina 2012).

 This species filters water substantially faster than D. polymorpha (Karatayev et al. 2010).

 This species consumes zooplankton: 

o Copepodites experienced 30% mortality in mussel treatments, compared to controls (Rojas 

Molina et al. 2013). 

o Gut content analysis found that microcrustaceans constitute about 67% of mussel diet biomass 

(Rojas Molina et al. 2010). 

o Significant declines in rotifers and cladocerans in mesocosm experiments with mussels 

 L. fortunei can reach densities of 5000-250,000 ind/m2 on hard substrate, and 90-2000 ind/m2 on soft substrate 

(Frau et al. 2013).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 An increase in water transparency, and a decrease in suspended matter, chlorophyll a, and primary production 

has been observed after Golden Mussel establishment (Boltovskoy et al. 2009).

 A decrease in turbidity and an increase in dissolved nitrogen has been found when Golden Mussels are present

(Rojas Molina 2012).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?
667

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U

 Increased habitat complexity can lead to significant (e.g., threefold) increase in community taxonomic richness. 

Gloden Mussel shells increase surface area for settling organisms, and also provide refuges from predation and 

physical stressors (Burlakova et al. 2012, Darrigran et al. 1998, Darrigran and Damborenea 2011, Spaccesi 

and Capitulo 2012). This species transforms sand or mostly bare sediment into reef-like druses (Burlakova et 

al. 2012).

Environmental Impact Total 30

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √

Not significantly 0 

Unknown U
668

 In a mesocosm experiment, cell density, proportion of colonial cells and colony size of Microcystis spp. 

increased in all enclosures, but these increases were dramatically (and very significantly) higher in enclosures 

with 100 and, especially, with 300 Golden Mussels, than in the controls. Enclosure density reflected realistic 

densities. The results indicate that L. fortunei modifies nutrient concentrations and proportions, and promotes 

aggregation of solitary Microcystis spp. cells into colonies; both these effects can favor blooms of this often 

noxious cyanobacteria (Cataldo et al. 2012a).

 Gazulha et al. (2012) found that while single cells of cyanobacteria were accepted, filamentous and colonial 

cyanobacteria were rejected as pseudofeces, a preference that could enhance blooms.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 L. fortunei can clog or foul water intake sieves and filters, pipes, heat exchangers, and condensers has become 

a common difficulty in industrial and power plants that use raw water, chiefly for cooling purposes (Boltovskoy 

et al. 2009, Cataldo et al. 2003, Goto 2002,).

 Grit chambers and flocculators have been found heavily clogged with sediment of broken shell and tissue 

material (Crosier and Molloy 2004 , Goto 2002, Magara et al. 2001).

 This increases operational costs (complete shutdown of plant; clogging of mussels, shell material, and sediment 

may need to manually removed) (Crosier and Molloy 2004, Goto 2002).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1 √

Not significantly 0 

Unknown U

 Decaying Golden Mussels pollute drinking water systems (Crosier and Molloy 2004).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 6
669

tourism 

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 √

Not significantly 0 

Unknown U

 Decaying dead Golden Mussels emit a noxious odor (Crosier and Molloy 2004)

Socio-Economic Impact Total 9

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 
670

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 

 In experiments performed by Di Fiori et al. (2012) glyphosate decreased by 40% under large mussel presence, 

and was reduced by25% in empty shell treatments. The authors believe that part of the herbicide that 

disappeared from the water column was adsorbed in Golden Mussel valvae surface, while another was

mineralized by microbial communities in shells’ biofilm. Glyphosate is an herbicide with negative impacts on 

aquatic filtering organisms and sediment feeders. However, the Golden Mussel may speed up the bioavailability 
671

of the phosphorous in glyphosate, leading to eutrophication, but this is expected to be outweighed by the 

remediation of the herbicide (Di Fiori et al. 2012).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6 √

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0

Unknown U 

 An increase in Golden Mmussel densities have been associated with a threefold increase in Argentina's 

freshwater fish landings in the Rio do la Plata basin after 1995, due to its status as a new, abundant food 

source (Boltovskoy et al. 2006). The Rio de la Plata system is otherwise poor in plankton (Boltovskoy et al. 

2006).

 In a study of 15 fish taxa, 11 had veligers of L. fortunei in their gut (several of these fish species economically 

and environmentally important). Fish larvae with empty guts represented 60% (San Nicola ́ s) to 72% (Parana ́ 

River) of the total number of fish. Proportions of feeding fish larvae with L. fortunei veligers in their guts varied 

between 20% (San Nicola ́ s) and 56% (Parana ́ River); in 15% of the guts analyzed, L. fortunei was the only 

food item recorded. For those specimens that had consumed L. fortunei larvae and any other food item, L. 

fortunei was the most important item in 55% (Parana ́ River) to 71% (San Nicola ́ s) of the animals in terms of 

biomass. Consumption of L. fortunei veligers decreased as fish larvae grew and were able to capture more 

difficult prey (Paolucci et al. 2007). 

 Feeding on veligers of L. fortunei significantly enhanced the growth of P. lineatus larvae and supported the 

idea that this new and abundant resource is selectively preyed upon by P. lineatus during its larval stage. 

Higher growth rates may have stemmed from the higher energy contents of veligers compared to crustaceans 

and/or from the lower energy costs of capturing slower prey (Paolucci et al. 2010). 

 According to Boltovskoy et al. (2006), positive impacts of L. fortunei are not limited to fishes that directly 

consume Golden Mussels, but there are also indirect positive effects on ichthyophagous and detritivorous fish 

species. Fish larvae, e.g. Salminus maxillosus, Rhaphiodon vulpinus, Pseudoplatystoma coruscans, 

Pseudoplatystoma fasciatum, and metalarvae of other Pimelodidae that prey on other larval fish probably 

benefit from the mussel-enhanced growth rates of their prey.

Beneficial Effect Total 7

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
672

Scientific Name: Monodacna colorata

Eichwald, 1829

Common Name: Colored Lagoon Cockle

Synonyms: Monodacna colorata

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate 

Monodacna colorata has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping (NOBOB vessels)

The introduction and spread of Monodacna colorata to non-native locations throughout Europe was 

facilitated by direct involvement from human vectors, likely including shipping (Grigorovich et al. 2003). 

Grigorovich et al. (2003) classify this species as a potential Great Lakes invader through ballast-mediated 

(NOBOB) introduction from ships originating in the Black-Azov Sea basin, though with reduced invasion 

likelihood due to ballast exchange or flushing. Specimens from the Caspian Sea are known to tolerate 

salinities up to 10 ppt (Karpevich 1960), while those from the Azov Sea quickly perish with salinities 

greater than 5 ppt (Zenkevich 1963). These physiological restrictions are expected to reduce the 

probability of introduction under current ballast water regulations (30 ppt flushing).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
673

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical,

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?
674

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1
675

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Grigorovich et al. (2003) classify this species as a potential Great Lakes invader through ballast-mediated 

(NOBOB) introduction, though with reduced invasion likelihood due to ballast exchange or flushing.

 The introduction of this species to non-native locations in Europe was facilitated by direct involvement from 

human vectors, likely including shipping (Grigorovich et al. 2003).

 Specimens from the Caspian Sea are known to tolerate salinities up to 10 ppt (Karpevich 1960), while those 

from the Azov Sea quickly perish with salinities greater than 5 ppt (Zenkevich 1963). These physiological 

restrictions are expected to reduce the probability of introduction under current ballast water regulations (30 

ppt flushing).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
676

 Monodacna colorata is likely to be introduced by ships originating in the Black-Azov Sea basin (Grigorovich et 

al. 2003).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
677

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Monodacna colorata has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

Specimens from the Caspian Sea are known to tolerate salinities of 1-10 ppt (Karpevich 1960), while 

those from the Azov quickly perish in salinities greater than 5 ppt (Zenkevich 1963). This is well within 

the range of the Great Lakes; however, Shokhin et al. (2006) reported that juveniles best develop at a 

salinity of 5 ppt. This is higher than the typical range within the Great Lakes and may be a physiological 

factor that restricts establishment. Establishment may be further restricted by the inability of juveniles to 

overwinter; when shallow water regions become chilled, sexually immature individuals die out. Older (2-

3 year old) individuals have adapted behaviorally to avoid these conditions by migrating to deeper waters 

of 4-5 m (Shokhin et al. 2006), but populations are still negatively affected. In 2003, severe winter 

conditions caused average biomass densities of M. colorata in areas of the Azov Sea to drop to 3.2 g/m2, 

down from usual densities of up to 600 g/m2(Shokhin et al. 2006).

Monodacna colorata requires a sandy bottom environment with high oxygen content (Shokhin et al. 

2006) and is reported to co-occur with the invasive Dreissena polymorpha in substrate at depths of 20-50 

m (Kosova 1963). This habitat type is readily abundant in the Great Lakes, with possibly the exception of 

Lake Erie’s periodic anoxic conditions (Summers 2001). It feeds upon planktonic green algae, diatoms, 

and detritus (Zaitsev and Öztürk 2001), none of which are limiting within the Great Lakes. Monodacna

colorata is likely to benefit from the predicted effects of climate change, including reduced ice-cover 

duration and warmer temperatures. This is evidenced by the massive reduction in biomass density in areas 

of the Azov Sea following harsh winter conditions in 2003 (Shokhin et al. 2006). Increased salinization, 

as predicted in the Great Lakes (Rahel and Olden 2008) is also likely to benefit this species, as juveniles 

best develop in salinity of 5 ppt and adults best dwell and reproduce in 8-9 ppt (Shokhin et al. 2006). This 

effect may also benefit M.. colorata is terms of reduced competition with native bivalves (more than 40 

species) that may be intolerant of salinity increases.

There are no reported occurrences of M. colorata outcompeting another species within its native or 

introduced ranges throughout Europe. This species shows relatively low biomass densities in comparison 

to other species within benthic communities of Taganrog Bay in the Azov Sea (Shokhin et al. 2006) after 

once being reported as the dominant species there (Karatayev et al. 1997, Nekrasova 1971, Vorobiev 

1949). In recent years, it has experienced native population reductions in areas of the Black Sea and is 

under strict protection in Romania (Popa et al. 2011).

Monodacna colorata is preyed upon by bottom dwelling fish (Zaitsev and Öztürk 2001); however, the 

extent to which this predation will prevent the establishment of populations in the Great Lakes is 

unknown. It was intentionally stocked into the Veselovsky Reservoir, Russia from 1951-1956 for the 

purpose of enhancing fish diet (Grigorovich et al. 2003, Kruglova 1961, Zhuravel 1969, Zhuravel 1975). 

From there, it spread relatively quickly to other canals and reservoirs and reached the Caspian Sea and 

Volga delta—probably as a result of shipping traffic with the opening of the Volga-Don Canal 

(Grigorovich et al. 2003). Within 7 years of the opening of the canal in 1952, this species had spread from 

the Black-Azov Sea basin into the Caspian Sea (Saenkova 1956). In 1960, one year after appearing in the 

Caspian, this species was observed in the lower Volga River (Kosova 1963). Panov et al. (2009) classify 

this species as having a high probability of dispersal as well as a high probability of establishment once 

introduced to a new inland waterway based on information from Son (2007).
678

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

4

 Specimens of this species from the Caspian Sea are known to tolerate salinities of 1-10 ppt (Karpevich 1960), 

while those from the Azov quickly perish in salinities greater than 5 ppt (Zenkevich 1963).

 Monodacna colorata inhabits areas of shallow sand and sand-aleuritic benthic deposits with high oxygen 

content (Nabozhenko and Kovalenko 2011).

 The physiological tolerance of this species to other parameters is unreported.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

5

 When shallow water regions become chilled, sexually immature individuals of this species die out; while 2-3 

year old individuals have adapted behaviorally to avoid these conditions by migrating to deeper waters of 4-5 

m (Shokhin et al. 2006).

 In 2003, severe winter conditions caused average biomass densities of M. colorata in areas of the Azov to drop 

to 3.2 g/m2, down from usual densities of up to 600 g/m2(Shokhin et al. 2006).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3
679

This species is an autotroph. 0

Unknown U

9

 This species filter feeds on planktonic green algae, diatoms, and detritus (Zaitsev and Öztürk 2001).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 There are no reported occurrences of M. colorata outcompeting another species within its native or introduced 

ranges throughout Europe. This species shows relatively low biomass densities in comparison to other species 

within benthic communities of Taganrog Bay in the Azov Sea (Shokhin et al. 2006) after once being reported as 

the dominant species there (Karatayev et al. 1997).

 This species shows relatively low biomass densities in comparison to other species within benthic communities

of Taganrog Bay in the Azov Sea (Shokhin et al. 2006).

 In recent years, it has experienced native population reductions in areas of the Black Sea and is under strict 

protection in Romania (Popa et al. 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 The fecundity of the related Monodacna angusticostata may reach several hundred thousand eggs 

(Malinovskaya 1961).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?
680

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species originates in the Black and Azov Seas where climatic conditions are very similar to those of the 

Great Lakes.

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

3
681

 The reported salinity ranges tolerated by M. colorata (<10 ppt (Karpevich 1960), <5 ppt (Zenkevich 1963)) are 

well within Great Lakes ranges.

 Shokhin et al. (2006) reported that juveniles best develop at a salinity of 5 ppt, which is higher than the typical 

salinity range in the Great Lakes.

 Abiotic factors and climatic conditions of the native range is quite similar to the Great Lakes, making the 

region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Monodacna colorata requires a sandy bottom environment with high oxygen content (Shokhin et al. 2006) 

and is reported to co-occur with the Great Lakes invasive Dreissena polymorpha in substrate at depths of 

20-50 m (Kosova 1963). This habitat type is readily abundant in the Great Lakes, with possibly the 

exception of Lake Erie’s periodic anoxic conditions (Summers 2001).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Monodacna colorata is likely to benefit from the predicted effects of climate change, including reduced icecover duration and warmer temperatures. This is evidenced by the massive reduction in biomass density in 

areas of the Azov Sea following harsh winter conditions in 2003 (Shokhin et al. 2006). Increased salinization as 

predicted in the Great Lakes (Rahel and Olden 2008) is also likely to benefit this species, as Shokhin et al. 

(2006) report that it best develops in salinity of 5 ppt and adults best dwell and reproduce in 8-9 ppt. This effect 

may also benefit M. colorata is terms of reduced competition with native bivalves (more than 40 species) that

may be intolerant of salinity increases.
682

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Monodacna colorata filter feeds on planktonic green algae, diatoms, and detritus (Zaitsev and Öztürk 2001), 

none of which are limiting within the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by M. colorata.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?
683

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 Monodacna colorata is preyed upon by bottom dwelling fish (Zaitsev and Öztürk 2001); however, the extent to 

which this predation will prevent the establishment of populations in the Great Lakes is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6
684

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 Monodacna colorata was intentionally stocked into the Veselovsky Reservoir, Russia from 1951-1956 for the 

purpose of enhancing fish diet (Grigorovich et al. 2003, Kruglova 1961, Zhuravel 1969, Zhuravel 1975). From 

there, it spread to other canals and reservoirs and reached the Caspian Sea and Volga delta—likely as a result 

of shipping traffic with the opening of the Volga-Don canal (Grigorovich et al. 2003).

 Panov et al. (2009) classify this species as having a high probability of dispersal as well as a high probability 

of establishment once introduced to a new inland waterway based on information from Son (2007).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 Within 7 years of the opening of the Volga-Don canal in 1952, this species had spread from the Black-Azov Sea 

basin into the Caspian (Saenkova 1956).

 In 1960, one year after appearing in the Caspian Sea, this species was observed in the lower Volga River 

(Kosova 1963).
685

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 86

>100 High Adjustments

B. Critical species A*(1- 0%) 86

51-99 Moderate C. Natural enemy B*(1- 0%) 86

Control measures C*(1- 0%) 86

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low
686

Beneficial: Low

Current research on the potential for environmental impacts to result from Monodacna colorata if 

introduced to the Great Lakes is inadequate to support proper assessment.

There are no reported cases of M. colorata outcompeting other species within its native or introduced 

ranges throughout Europe, though at one time it was the dominant species over D. polymorpha in 

Taganrog Bay of the Azov Sea (Karatayev et al. 1997, Nekrasova 1971, Vorobiev 1949). Any negative 

effects on water quality or substrate composition caused by filter feeding (Zaitsev and Öztürk 2001) and 

its inhabitance of high-oxygen sandy benthic communities (Shokhin et al. 2006) are unreported.

There is little or no evidence to support that Monodacna colorata has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

Panov et al. (2009) classify M. colorata as a white-list species, able to readily disperse and establish but 

not at high risk for causing significant socio-economic impacts.

There is little or no evidence to support that Monodacna colorata has the potential for significant 

beneficial effects if introduced to the Great Lakes.

Monodacna invalida was intentionally stocked into the Veselovsky Reservoir from 1951-1956 for the 

purpose of enhancing fish diet (Grigorovich et al. 2003, Kruglova 1961, Zhuravel 1969, Zhuravel 1975), 

though substantial increases in fishery production since its introduction have not been reported. This 

species is also listed as being edible to humans (Bourquin 2002).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

6
687

spawning behavior) on one or more native populations

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0 √

Unknown U

 There are no reported cases of M. colorata outcompeting another species within its native or introduced 

ranges throughout Europe.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0 √

Unknown U

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0

Unknown U √

 Monodacna colorata filter feeds on green planktonic algae, diatoms, and detritus (Zaitsev and Öztürk 2001), 

though any resulting effects on water quality are unreported.
688

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0

Unknown U √

 This species inhabits sandy bottom environments with high oxygen content (Shokhin et al. 2006), though any 

physical effect it may have on the benthic ecosystem is unreported.

Environmental Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √
689

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √
690

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U

 Monodacna invalida was intentionally stocked into the Veselovsky Reservoir from 1951-1956 for the purpose of 

enhancing fish diet (Grigorovich et al. 2003, Kruglova 1961, Zhuravel 1969, Zhuravel 1975), though 

substantial increases in fishery production since its introduction have not been reported.

 This species is also listed as being edible by humans (Bourquin 2002).
691

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 1

Total Unknowns (U) 0
692

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
693

A.3 Bryozoans

Scientific Name: Fredericella sultana

Blumenbach, 1779

Common Name: Branching Bryozoan, Moss Animal

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Low

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: High

Fredericella sultana has a high probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping, Hitchhiking/Fouling

The production of resting stage statoblasts provide F. sultana with resistance to a variety of chemical and 

physical stressors, including extreme temperatures, periods of drought, and a variety of chemical 

treatments (Kipp et al. 2010, Wood 2005a). Statoblasts will generally remain viable after being exposed 

to a 1-2 ppt medium for up to two years and will quickly germinate upon return to freshwater (Kipp et al. 

2010, Wood 2005b). The properties and hardiness exhibited by these statoblasts make this species a prime 

candidate to be taken up and transported in the ballast water of transoceanic ships (Bailey et al. 2005a, 

Kipp et al. 2010). In a survey of 33 randomly chosen ships with NOBOB tanks visiting the Great Lakes 

between December 2000 and December 2002, 3 ships (9.1%) possessed statoblasts of F. sultana within 

their ballast sediment (Kipp et al. 2010). This species made up only 0.7% of total bryozoan statoblast 

abundance (n=409) within the ships surveyed, for a total of 3 individuals. Statoblasts produced by this 

organism are also known to thrive in slightly brackish water, increasing the likelihood of transport via 

ballast tanks (Bailey et al. 2005a, Everitt 1975, Kipp et al. 2010, Massard and Geimer 2008). It is 

estimated that in ships with NOBOB tanks, up to one million statoblasts may be transported in a single 

voyage (Kipp et al. 2010).

As F. sultana lacks buoyant statoblasts, individuals are likely to be distributed by drifting fragments of 

colonies or by substrata such as aquatic plants and other dormant structures (Wood 2005). However, this 

species has not been observed in any waterways directly connected to the Great Lakes basin, thus 
694

diminishing the threat of introduction by dispersal and/or fouling. Bryozoan species have been known to 

exhibit distributions following those of bird migration routes (Wood 2002), and wastewater treatment 

plants noticing bryozoans present in their secondary water clarifiers tend to note frequent visits by ducks, 

possibly transporting viable statoblasts from their natural habitats (Wood 2005).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 While F. sultana lacks buoyant statoblasts, it is likely to be distributed by drifting colony fragments or by 

substrata such as aquatic plants or other dormant structures (Wood 2005).

 This species has not been observed in any waterways directly connected to the Great Lakes basin, thus 

diminishing the threat of introduction by dispersal.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Bryozoan species have been known to exhibit distributions following those of bird migration routes (Wood 

2002), and wastewater treatment plants noticing bryozoans present in their secondary water clarifiers tend to 
695

note frequent visits by ducks, possibly transporting viable statoblasts from their natural habitats (Wood 2005). 

Substrata, such as drifting aquatic plants and other non-living materials are thought to be likely transport 

mechanisms for this species.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 As a cosmopolitan species, F. sultana may be present in North America, but specimens previously thought to be 

this species have alternatively been proposed to be F. indica (Wood and Backus 1992).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U
696

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?
697

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 The production of resting stage statoblasts provides F. sultana with resistance to a variety of chemical and 

physical stressors, including extreme temperatures, periods of drought, and a variety of chemical treatments 

(Kipp et al. 2010, Wood 2005).

 Statoblasts will generally remain viable after being exposed to a 1-2 ppt medium for up to two years and will 

quickly germinate upon return to freshwater (Kipp et al. 2010, Wood 2005b). 

 The hardiness exhibited by their statoblasts make this species a prime candidate to be taken up and transported 

in the ballast water of transoceanic ships (Bailey et al. 2005a, Kipp et al. 2010).

 Ballast flushing regulations are currently in place for the purpose of purging statoblasts at sea and reducing 

the number of retained statoblasts when exposed to open ocean seawater in tanks. Since these measures were 

implemented in 2006, there has been no apparent decline in statoblast occurrence or abundance among 

bryozoans as a group (Briski et al. 2010).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 √

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 In a survey of 33 randomly chosen ships with NOBOB tanks visiting the Great Lakes between December 2000 

and December 2002, 3 ships (9.1%) possessed statoblasts of F. sultana within their ballast sediment (Kipp et al. 

2010). This species made up 0.7% of total bryozoan statoblast abundance (n=409) within the ships surveyed, 

for a total of 3 individuals (Kipp et al. 2010).
698

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 1 100 High

Total Unknowns (U) 0 Confidence Level High
699

Fredericella sultana has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

Fredericella sultana is able to survive a broad range of physiological conditions from a resting stage 

statoblast through the adult phase. The production of highly resistant statoblasts as the primary 

reproductive mechanism in this species increase the likelihood of establishment to new areas, as they are 

tolerant of extreme temperatures, periods of drought, and exposure to organic pollution, heavy metals, 

toxins, pesticides, and herbicides (Kipp et al. 2010). It can persist in water temperatures ranging from 0°C 

in the resting stage to over 20°C as adult colonies (Tops et al. 2009). Colonies occur naturally at salinities 

of 0 ppt and are known to tolerate slightly brackish conditions of 3-4 ppt (Occhipinti Ambrogi and 

d’Hondt 1981). Increasing temperatures and elevated nutrient levels from increased runoff predicted by 

climate change are expected to increase the invasion success of this species. Greatest growth is achieved 

in high nutrient conditions (1 mg P/L and 10 mg N/L); however increased mortality occurs as nutrient 

levels decrease. At low nutrient levels (.06 mg P/L and 1 mg N/L), average colony mortality of 30% has 

been observed (Hartikainen et al. 2009). Additionally, Tops et al. (2009) observe a positive correlation 

between temperature and colony size, with colonies exposed to 20°C temperatures growing up to 160% of 

the size of colonies exposed to 14°C water. This prolific growth exhibited in high temperature and 

nutrient conditions makes F. sultana a great competitor for space. Colonies have been reported to reach 

biomass densities of up to 117 g/m2by the end of a growing season (Raddum and Johnsen 1983). Freeze 

resistant statoblasts have the ability to overwinter under ice and regenerate a new colony when conditions 

become favorable (Kipp et al. 2010, Thorp and Covich 2001, Wood 2005). Freezing and desiccation may 

be tolerated by these statoblasts for months to even years (Bushnell and Rao 1974).

Fredericella sultana is a filter feeding organism and diet preference is determined based upon prey 

availability throughout different seasons. Prey items are comprised primarily of flagellates, monads, 

cyanophyceans, and diatoms, none of which are expected to be a limiting resource for this species in the 

Great Lakes. The size of the mouth opening is the only limit to which particles can be consumed, with a 

maximum consumable particle size of about 240 micrometers (Raddum and Johnsen 1983). 

Multiplication by colonial fragmentation is an additional trait likely to increase invasion success. This 

species is considered cosmopolitan (Økland and Økland 2005), and likely exists or is able to exist in 

climatic conditions similar to those of the Great Lakes. Fredericella sultana is a common prey item for 

the Great Lakes native bluegill (Lepomis macrochirus), comprising over 75% of the diet of this fish at 

certain times of the year (Applegate 1966). However, the extent to which this predation will be effective 

in preventing the establishment of this species in the Great Lakes is unknown.

While no data exists for the spread of this particular species in non-native ranges, freshwater bryozoans 

with non-buoyant statoblasts are known to disperse rapidly through attachment to drifting substratum 

(such as plants and non-living objects), and through migrating waterfowl (Wood 2005). Ballast flushing 

regulations are currently in place for the purpose of purging statoblasts at sea and reducing the number of 

viable individuals entering the Great Lakes (see management). Ever since these measures were 

implemented in 2006, there has been no apparent decline in statoblast occurrence or abundance among 

bryozoans as a group in ballast sediment (Briski et al. 2010). However, no specific data is available on the 

effect of these regulations with regard to this particular species.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 9
700

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 F. sultana is able to survive a broad range of physiological conditions from a resting stage statoblast to the 

adult phase. It can survive in water temperatures ranging from 0°C as freeze resistant statoblasts to over 20°C 

as adult colonies (Tops et al. 2009). Colonies occur naturally at salinities of 0 ppt and are known to tolerate 

slightly brackish conditions of 3-4 ppt (Occhipinti Ambrogi and d’Hondt 1981).

 Greatest growth is achieved in high nutrient conditions (1 mg P/L and 10 mg N/L); however, increased 

mortality occurs as nutrient levels decrease. At low nutrient levels (.06 mg P/L and 1 mg N/L), average colony 

mortality of 30% has been observed (Hartikainen et al. 2009).

 Adult bryozoan colonies are usually unable to survive 3 hours of expose to anoxic conditions or water 

temperatures of 35°C or greater (Wood 2005a).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Freeze resistant statoblasts have the ability to overwinter under ice and regenerate a new colony when 

conditions become favorable (Kipp et al. 2010, Thorp and Covich 2001, Wood 2005). Freezing and desiccation 

may be tolerated by these statoblasts for months to even years (Bushnell and Rao 1974).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6
701

 F. sultana is a filter feeding organism, with diet preference determined by prey availability throughout different 

seasons. The size of the mouth opening is the only restriction on what particles can be consumed, with a 

maximum consumable size of 240 micrometers (Raddum and Johnsen 1983).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6

 This species exhibits prolific growth in high temperature and nutrient conditions (Hartikainen et al. 2009, 

Tops et al. 2009), making it a great competitor for space. Colonies have been reported to reach biomass 

densities of up to 117 g/m2by the end of a growing season (Raddum and Johnsen 1983).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6
702

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

9

 The production of highly resistant statoblasts as the primary reproductive mechanism in this species increases 

the likelihood of establishment to new areas, as they are tolerant of extreme temperatures, periods of drought, 

and exposure to organic pollution, heavy metals, toxins, pesticides, and herbicides (Kipp et al. 2010).

 Multiplication by fragmentation is an additional trait likely to increase invasion success.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 This species is considered cosmopolitan (Økland and Økland 2005), and likely exists or is able to exist in 

climatic conditions similar to those of the Great Lakes.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 F. sultana is able to tolerate a wide range of water temperatures, ranging from 0°C as freeze resistant 

statoblasts and over 20°C as adult colonies (Tops et al. 2009). Colonies occur naturally at salinities of 0 ppt 

and are known to tolerate slightly brackish conditions of 3-4 ppt (Occhipinti Ambrogi and d’Hondt 1981).

 Greatest growth is achieved in high nutrient conditions (1 mg P/L and 10 mg N/L); however, increased 

mortality occurs as nutrient levels decrease (Hartikainen et al. 2009).
703

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 This species has a broad global distribution, occurring in freshwater habitats throughout Europe, Asia, 

Australasia, and one location in western North America (Kipp et al. 2010, Wood 2002, Wood and Okamura 

2005).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 Increasing temperatures and elevated nutrient levels from increased runoff are expected to increase the success 

of this species. Hartikainen et al. (2009) provides evidence for significantly increased growth rates with high 

nutrient concentrations (1 mg P/L and 10 mg N/L) and significantly greater mortality rates with low nutrient 

concentrations (.06 mg P/L and 1 mg N/L).

 Tops et al. (2009) observe a positive correlation between temperature and colony size, with colonies exposed to 

20°C temperatures growing to 160% of the size of colonies exposed to 14°C.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9
704

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 The primary diet of F. sultana is comprised of flagellates, monads, cyanophyceans, and diatoms, none of which 

are expected to be a limiting resource for this species in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There are no critical species required for survival by F. sultana.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

6
705

and spread in the Great Lakes)

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 F. sultana is a common prey item for the Great Lakes native Bluegill (Lepomis macrochirus), comprising over 

75% of the diet of this fish at certain times of the year (Applegate 1966). However, the effect of this predation 

on the establishment of this species is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U
706

0

 In a survey of 33 vessels entering the Great Lakes over a two year period from 2000 to 2002, only 3 statoblasts 

of this species were collected in total, comprising just 0.7% of the total number of bryozoan statoblasts 

collected (Kipp et al. 2010).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

0

 There are no reported nonindigenous occurrences of this species.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

 While no data exist for the spread of this particular species in non-native ranges, freshwater bryozoans with 

non-buoyant statoblasts are known to disperse rapidly through attachment to drifting substratum (such as 

plants and non-living objects), and through migrating waterfowl (Wood 2005).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)
707

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 84

>100 High Adjustments

B. Critical species A*(1- 0%) 84

51-99 Moderate C. Natural enemy B*(1- 0%) 84

Control measures C*(1- 0%) 84

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

POTENTIAL IMPACT RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Low

Fredericella sultana has the potential for high environmental impact if introduced to the Great 

Lakes.
708

Once established, this species is likely to be a great competitor for space in areas of high nutrient 

concentration, able to reach biomass densities of up to 117 g/m2by the end of the growing season 

(Raddum and Johnsen 1983).

Fredericella sultana is the most common host of the myxozoan parasite Tetracapsuloides bryosalmonae, 

which causes proliferative kidney disease (PKD) in salmonid fish (Anderson et al. 1999, Feist et al. 2001, 

McGurk et al. 2005, McGurk et al. 2006, Morris and Adams 2006, Okamura and Wood 2002). PKD is a 

serious infection of both wild and farmed salmonids affecting mainly the kidney and spleen, and it can 

become systemic in many host fishes. It has been observed experimentally that native Rainbow Trout 

(Oncorhynchus mykiss) exposed for both short-term and long-term periods to bryozoans infected with T. 

bryosalmonae became infected with PKD as a result of the parasite (Feist et al. 2001). Recent research 

has indicted that widespread cases of PKD in Swiss rivers have caused over 25% mortality of the native 

wild Brown Trout populations (Borsuk et al. 2006, Wahli et al. 2002). Due to the capability of very few 

spores to cause infection in wild populations, mortality rates of individuals infected with PKD are able to 

reach 100% (Feist et al. 2001). PKD outbreaks are highly seasonal, typically occurring when water 

temperatures have reached 15°C (Hedrick et al. 1993). When water temperatures are below 10°C, PKD 

will not develop (Gay et al. 2001). In addition to disease development, higher temperatures seem to be 

associated with greater disease severity (Naich et al. 2003). Due to the strong effect of water temperature 

on the proliferation of PKD, climate change is likely to be a factor that will lead to an increase in the 

prevalence of this disease, especially in farmed fish populations (Tops et al. 2006). The clonal nature of 

F. sultana provides a highly suitable place for the cryptic stages of this parasite to settle, and it is 

presumed that multiplication of the parasite occurs in union with the multiplication of the bryozoan 

colony (Tops et al. 2004).

Fredericella sultana has the potential for high socioeconomic impact if introduced to the Great 

Lakes.

Proliferative kidney disease has resulted in significant economic loss to both salmonid hatcheries and the 

rainbow trout fish farming industry (Anderson et al. 1999, Feist et al. 2001, Hedrick et al. 1993). While 

the effects of PKD on wild fish stocks tend to be poorly known (Feist et al. 2002, Hedrick et al. 1993), a 

recent study observed up to 25% mortality of a native brown trout population in a Swiss river containing 

the T. bryosalmonae parasite (Borsuk et al. 2006, Wahli et al. 2002).

It is also possible that this species could cause significant damage to infrastructure (e.g., water intake 

pipes). Bryozoans are one of the most common fouling animals and can impose serious economic costs 

by blocking conduits and end use devices. An extreme case of this occurred in Europe at the beginning of 

the century, when hundreds of tons F. sultana had to be removed from water pipelines throughout major 

cities (Harmer 1913). However, cases of such rapid colony production are extremely rare. The three major 

aspects of its life history that hinder biofouling control efforts are, first, the production of dormant 

statoblasts that can tolerate a wide range of physical and chemical conditions; second, the ability of 

bryozoan colonies to regenerate from pockets of living tissue; and third, its easy dispersal through air and 

water (Wood 2005a). Very few reliable experimental data are available on practical methods to control 

bryozoan fouling.

There is little or no evidence to support that Fredericella sultana has the potential for significant 

beneficial effects if introduced to the Great Lakes.

Due to the very poor digestion efficiency of F. sultana, this species must maintain a high turnover of 

nutrient particles. Therefore, colonies undergoing rapid growth may play an important role in nutrient 

cycling in a freshwater system as well as in determining phytoplankton dynamics (Raddum and Johnsen 
709

1983). However, whether this will provide any ecologically significant beneficial impact in any part of 

the Great Lakes is unknown.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels, is poisonous, a virus, bacteria, parasite, or a vector of one)? 

Yes, and it has resulted in the reduction or extinction of one or more native species 

populations, affects multiple species, or is a reportable disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems, 

etc.)

1

Not significantly 0

Unknown U

 The freshwater bryozoan Fredericella sultana is the most common host of the myxozoan parasite 

Tetracapsuloides bryosalmonae, which causes proliferative kidney disease (PKD) in salmonoid fish 

(Anderson et al. 1999, Feist et al. 2001, Okamura and Wood 2002). PKD is a serious infection of both wild 

and farmed salmonids affecting mainly the kidney and spleen, and it can become systemic in many host 

fishes. It has been observed experimentally that native Rainbow Trout (Oncorhynchus mykiss) exposed to 

these bryozoans infected with Tetracapsuloides bryosalmonae for both short-term and long-term periods 

ended up becoming infected with PKD as a result of the parasite (Feist et al. 2001).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light, etc.)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, 

behavioral changes, etc.) on one or more native species populations

6

Yes, and it has caused some noticeable stress to or decline of at least one native species 

population

1 √

Not significantly 0

Unknown U

 Once established, this species is likely to be a great competitor for space with other settling and colonizing 

organisms in areas of high nutrient concentration, able to reach extremely high biomass densities by the 

end of the growing season. This species is also able to remove nutrients from the water at rapid rates, 

potentially limiting their availability to plant species (Raddum and Johnsen 1983).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., added pressure to threatened/endangered species, significant reduction or extinction 

of any native species populations, creation of a dead end or any other significant alteration 

in the food web, etc.)

6
710

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression, etc.)?

Yes, and it has caused a loss or alteration of genes which may be irreversible or has led to 

the decline or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles, etc.)?

Yes, and it has had a widespread, long term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been mild

1

Not significantly 0

Unknown U √

E6) Does it alter the physical ecosystem in some way (e.g., facilitated erosion/siltation, altered hydrology, 

altered macrophyte/phytoplankton communities, changes to substrate (physical or chemical), etc.)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0

Unknown U

 Colonies undergoing rapid growth may play an important role in nutrient cycling in a freshwater system as 

well as in determining phytoplankton dynamics (Raddum and Johnsen 1983).

Environmental Impact Total 8
711

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (such as water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 Bryozoans are probably the most common among fouling animals and can impose serious economic costs 

by blocking conduits and end use devices. An extreme case of this occurred in Europe at the beginning of 

the century, when hundreds of tons F. sultana had to be removed from water pipelines throughout major 

cities (Harmer 1913).

S3) Does it negatively affect water quality?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6
712

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture, 

etc.)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0

Unknown U

 Proliferative kidney disease has resulted in significant economic loss to both salmonid hatcheries and the 

rainbow trout fish farming industry (Anderson et al. 1999, Feist et al. 2001, Hedrick et al. 1993). While the 

effects of PKD on wild fish stocks tend to be poorly known (Feist et al. 2002, Hedrick et al. 1993), a recent 

study observed up to 25% mortality of a native Brown Trout population in a Swiss river containing the 

Tetracapsuloides bryosalmonae parasite (Borsuk et al. 2006, Wahli et al. 2002).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species, etc.)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 12

Total Unknowns (U) 0

Scoring

Score # U Impact
713

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g. for fisheries, aquaculture, agriculture, bait, ornamental trade, etc.)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g. for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (outside of research geared towards its 

control)?
714

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0

Unknown U √

 Due to the very poor digestion efficiency of F. sultana, this species must maintain a high turnover of 

nutrient particles. Therefore, colonies undergoing rapid growth may play an important role in nutrient 

cycling in a freshwater system as well as in determining phytoplankton dynamics (Raddum and Johnsen 

1983). However, whether this will provide any ecologically significant beneficial impact in any part of the 

Great Lakes is unknown.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species which is threatened, endangered species, or commercially valuable, etc.)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
715

0 ≥2

Unknown

1 ≥1
716

A.4 Crustaceans - Amphipods

Scientific Name: Apocorophium lacustre

Vanhoffen, 1911

Common Name: Scud

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Moderate

Hitchhiking/fouling: Moderate

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Apocorophium lacustre has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Transoceanic Shipping

Apocorophium lacustre already occurs in waters connecting to the Great Lakes (Upper Mississippi River 

near Joliet, Illinois and the Ohio River (USGS 2013). Apocorophium lacustre could easily expand within 

the upper Mississippi River waterway via hull fouling associated with dreissenid mussel colonies 

(Grigorovich et al. 2008). Apocorophium lacustre is an abundant fouler (Llansó and Sillett 2009) and 

could easily be transported by recreational boaters and angerls from neighboring waters via fouling 

colonies. The strength of this recreational vector is unknown but is likely relatively infrequent and small. 

Apocorophium lacustre can be transported by ballast water (Power et al. 2006) and is able to survive large 

ranges of salinity (Wolf et al. 2009) making it capable of surviving to destinations within the Great Lakes. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 100 √
717

able to be transported by wind or water.

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Apocorophium lacustre has been introduced into the Upper Mississippi River, Illinois River (near Joliet, 

Illinois), and Ohio River (USGS 2013) .

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5 

√

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Joliet, Illinois is 72 km from Lake Michigan.

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Apocorophium lacustre likely expanded within the Upper Mississippi River waterway via hull fouling, 

associated with dreissenid mussel colonies (Grigorovich et al. 2008).

 Apocorophium lacustre is an abundant fouler, accounting for 1-2% of total abundance on three vessels in 

Beaumont (Texas), and found in 18, 44 and 42% of samples. Cleaning of vessel with 42% frequency only 

reduced its frequency to 32% (Llansó and Sillett 2009).

 This species occurs in Florida waters (Camp et al. 1998), including the St. Johns River basin (Evans et al. 

2004), which is the most significant river in Florida for recreational use.

 This species is present in Jacksonville (Florida), Wilmington (North Carolina), and Savannah (Georgia) 

(Power et al. 2006), as well as the Upper Mississippi River, Illinois River (near Joliet, Illinois), and Ohio River 

(USGS 2013).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5 
718

√

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 Joliet, Illinois is 72 km from Lake Michigan.

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5
719

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0
720

Unknown U

 Apocorophium lacustre is believed to be transported by ballast water (Power et al. 2006).

 It is euryhaline, surviving in salinities from 0-30 ppt (Wolf et al. 2009).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species occurs in the Rhine River and North Sea (Faasse and van Moorsel 2003).

 This species occurs in Florida waters (Camp et al. 1998), including the St. Johns River basin (Evans et al. 

2004), which is the most significant river in Florida for commercial use.

 Apocorophium lacustre is native to the North American Atlantic coast from the Bay of Fundy, New Brunswick 

to the St. Johns River estuary, Florida (Bousfield 1973). It is regarded as introduced in the Gulf of Mexico and 

the southern North Sea coast of Europe (Bousfield 1973, Power et al. 2006, Grigorovich et al. 2008). 

 Apocorophium lacustre was found in the Ohio River in 1996, and first detected in the Upper Mississippi River 

in 2005 (Grigorovich et al. 2008).
721

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 0.5 50 Moderate

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.5 50 Moderate

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0.5 50 Moderate

Total Unknowns (U) 0 Confidence Level High
722

Apocorophium lacustre has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Apocorophium lacustre is pollution tolerant (Evans et al. 2004), survives wide ranges of dissolved oxygen 

(DO) (Llansó and Sillett 2009), is salt tolerant (Wolf et al. 2009), and inhabits freshwater environments 

(USGS 2013). Apocorophium lacustre is already present in North American rivers where winter 

temperatures reach 1°C (Harmeson and Schnepper 1965) which suggest that it could survive the winter 

temperatures experienced in the Great Lakes. Apocorophium lacustre is a dietary generalist with a 

flexible diet (Llansó and Sillett 2009, Power et al. 2006) and could adjust its diet in the Great Lakes.

In other ranges where Apocorophium lacustre has been introduced, there are no existing control methods 

set to prevent the introduction or spread of Apocorophium lacustre. The tube-building habit of A. lacustre

is unique but its effect is likely to be non-specific. This behavior may protect A. lacustre from predation 

by other species thereby facilitating its survival and establishment in novel habitats (Armsby and Tisch 

2006, Grigorovich et al. 2008). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Apocorophium lacustre is pollution tolerant (Evans et al. 2004) and inhabits the mouth of the Rhine, which is 

very polluted.

 It is found in waters with DO ranging from 1.2-6.9 mg/L (Llansó and Sillett 2009).

 This species is described as salt tolerant (Evans et al. 2004), from 0-30 ppt (Wolf et al. 2009), and euryhaline, 

but it tends to be found in the least saline environments (Faasse and van Moorsel 2003).

 Apocorophium lacustre also inhabits freshwater, being found in the Upper Mississippi River, Illinois River, and 

Ohio River (USGS 2013).

 It is present in the Illinois River near Peoria and Pekin, IL (USGS 2013), where the mean water temperatures in 

January is 1°C (Harmeson and Schnepper 1965).

 Apocorophium lacustre has been found in temperatures up to 31.4°C (Llansó and Sillett 2009).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9
723

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Apocorophium lacustre is present in the Illinois river near Peoria and Pekin (Camp et al. 1998), where the 

mean water temperatures in January is 1°C (Harmeson and Schnepper 1965).

 This species has a recorded DO tolerance minimum of 1.2 mg/L (Llansó and Sillett 2009).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Apocorophium lacustre is a detritus, suspension, and surface-deposit feeder (Llansó and Sillett 2009, Power et 

al. 2006).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

4

 This species is found in low abundance in its native range (Faasse and van Moorsel 2003).

 Its relative abundance and frequency of occurrence increased in the Ohio River from 2004 through 2006 (from 

1.7-13.8%) and the Upper Mississippi River between 2004 and 2006 (0-11%) (Grigorovich et al. 2008).

 In a community studied in Germany, A. lacustre was the second-most dense arthropod, found in 14% of samples 

(Ysebaert et al. 2000).
724

 Apocorophium lacustre is ecologically very similar to Chelicorophium curvispinum and apparently does not do 

well in competition with this species; it disappeared from several previously-inhabited sites following invasion 

by C. curvispinum (Noordhuis et al. 2009).

 Apocorophium lacustre will compete with native mussels for food and habitat space and has been known to 

overwhelm populations (USACE 2013). 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 The fecundity of A. lacustre is not known, but this species is in the Corophiidae Family. 

 Brood size for other species in the Family Corophiidae (Cunha et al. 2000) include:

o Corophium multisetosum ranged from 8-138 eggs/female.

o Corophium acherusicum averaged 8-19 eggs/female.

o Corophium arenarium ranged from 6-22 eggs/female.

o Corophium bonellii ranged from 3-8 eggs/female.

o Corophium insidiosum ranged from ~1-40 eggs/female.

o Corophium volutator ranged from 4-70 eggs/female.

 Species from the Family Ampithoidae (in the Superfamily Corophioidea, containing Families Corophiidae and 

Ampithoidae) include the following fecundities (Best and Stachowicz 2013):

o Ampithoe dalli: 30 eggs/brooding female

o Ampithoe lacertosa: 40 eggs/brooding female

o Ampithoe sectimanus: 20 eggs/brooding female

o Ampithoe valida: 12 eggs/brooding female

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3
725

 Like other amphipods, A. lacustre broods its young, a strategy associated with enhanced colonization success.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 Apocorophium lacustre inhabits the Upper Mississippi River, Illinois River, and Ohio River (USGS 2013). 

These regions are very similar or identical to the Great Lakes region.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Apocorophium lacustre inhabits the Upper Mississippi River, Illinois River, and Ohio River (USGS 2013). 

These regions are very similar or identical to the Great Lakes region.

 Also, this species inhabits regions with a wide variety of abiotic factors, a range that includes those conditions 

found in the Great Lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0
726

Unknown U

9

 In its native habitat (Rhine River), A. lacustre is found in lower littoral and sublittoral regions and on boulder 

(10-50 cm diameter) substrate (Faasse and van Moorsel 2003).

 In the Upper Mississippi River, A. lacustre was found associated with hard, stable substrates – rocks and snags; 

in the Ohio River, where cobble and boulder habitats were less available, it colonized primarily sand and 

snags. This species is epibenthic and typically associated with inorganic substrates, aquatic vegetation, or 

zebra mussel colonies (Grigorovich et al. 2008).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 This species is described as salt tolerant (Evans et al. 2004), from 0-30 ppt (Wolf et al. 2009).

 It is found in temperatures up to 31.4°C (Llansó and Sillett 2009).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 Apocorophium lacustre is a detritus, suspension, and surface-deposit feeder (Llansó and Sillett 2009, Power et 

al. 2006).
727

 With widespread dreissenid mussel colonies, benthic production is very high in the Great Lakes (Hecky et al. 

2004).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at

end)

Unknown U

9

 There is no critical species required.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

7
728

 Amphipod invaders benefit from antecedent dreissenid invasion, which increases the structural complexity of 

bottom substrate for epibenthic organisms (Gonzalez and Burkart 2004, Stewart et al. 1998, van Overdijk et al. 

2003). The mussels also remove seston from the water column and transform it into feces and pseudofeces 

consumed by amphipods (Grigorovich et al. 2008, Mordukhaĭ-Boltovskoĭ 1960, Stewart et al. 1998).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 The tube-building habit of A. lacustre is unique but its effect is likely to be non-specific. This behavior may 

protect A. lacustre from predation by other species thereby facilitating its survival and establishment in novel 

habitats (Armsby and Tisch 2006, Grigorovich et al. 2008).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

 This species is quite small (up to 6 mm) and could easily be transported by recreational boaters and anglers 

from neighboring waters, or arrive via fouling colonies. The strength of this recreational vector is unknown but 

is likely relatively infrequent and small.

HISTORY OF INVASION AND SPREAD
729

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 This species is native to the Vistula lagoon, the Rhine River, and the North Sea (Ezhova et al. 2005, Faasse and 

van Moorsel 2003).

 This species occurs in Florida waters (Camp et al. 1998), including the St. Johns River basin (Evans et al. 

2004), which is the most significant river in Florida for commercial and recreational use.

 Apocorophium lacustre is native to the North American Atlantic coast from the Bay of Fundy, New Brunswick 

to the St. Johns River estuary, Florida (Bousfield 1973). It is regarded as introduced in the Gulf of Mexico and 

the southern North Sea coast of Europe (Bousfield 1973, Grigorovich et al. 2008, Power et al. 2006).

 This species has been introduced into the Upper Mississippi River, Illinois River, and Ohio River (USGS 2013).

 It has also been introduced to the River Werra in central Germany (Szöcs et al. 2014).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 This species’ range is rapidly expanding in the Upper Mississippi River system (Grigorovich et al. 2008).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are -20% total 
730

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no existing control methods set to prevent the introduction or spread of this species.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 103

>100 High Adjustments

B. Critical species A*(1- 0%) 103

51-99 Moderate C. Natural enemy B*(1- 0%) 103

Control measures C*(1- 0%) 103

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Apocorophium lacustre

if introduced to the Great Lakes is inadequate to support proper assessment.
731

There is insufficient information available to determine whether Apocorophium lacustre poses a threat to 

other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Apocorophium lacustre has the potential for significant 

socio-economic impacts of introduced to the Great Lakes.

It has not been reported that Apocorophium lacustre poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Apocorophium lacustre has the potential for significant 

beneficial impacts of introduced to the Great Lakes.

It has not been indicated that Apocorophium lacustre can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted 

threatened/endangered species or caused critical reduction, extinction, behavioral 

changes including modified spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 A. lacustre may have contributed to a decline in the native Gammarus pseudolimnaeus; though likely, it is 

uncertain (Grigorovich et al. 2008).
732

 A. lacustre is ecologically very similar to C. curvispinum and apparently does not do well in competition; it 

disappeared from several previously-inhabited sites following invasion by C. curvispinum (Noordhuis et al. 

2009).

 This species was abundant in survey of South Atlantic Bight (Jacksonville, Savannah, Charleston and 

Wilmington) (Power et al. 2006).

 A. lacustre will compete with native mussels for food and habitat space and have been known to overwhelm 

populations (USACE 2013). 

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 A. lacustre has been found to alter food webs and decrease faunal diversity in areas of non-native establishment 

(USACE 2013).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √
733

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native 

species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and 

resulting adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 A. lacustremay smother native mussels (Northeast Aquatic Nuisance Species Panel 2003).

Environmental Impact Total 1

Total Unknowns (U) 4

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U
734

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
735

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 1 
736

tourism 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
737

1 0

0 ≥2

Unknown

1 ≥1

Scientific Name: Chelicorophium curvispinum

G.O. Sars, 1895

Common Name: Caspian Mud Shrimp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Chelicorophium curvispinum has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Chelicorophium curvispinum is indigenous and widespread throughout the Ponto-Caspian region and 

recently has invaded the Baltic Sea and many large European river systems (bij de Vaate et al. 2002). In 

Europe, shipping—including transport by ballast water and hull fouling—has been the primary vector of 

dispersal of this species outside of its native range (den Hartog et al. 1992, Harris 1991, Leppäkoski and 

Olenin 2001, van der Velde et al. 2000). Introduction to Great Britain, for instance, likely occurred via 

ballast water released from ships trading with ports on the Elbe River in northern Germany (Harris 1991). 

The discovery of C. curvispinum west of the Rhine River system before it was discovered in the Rhine 

lends further support to shipping mediated spread (den Hartog et al. 1992), as this sort of “jump” dispersal 

is a common indicator of human-mediated transport (MacIsaac et al. 2001).

As Great Lakes shipping traffic commonly originates in areas where this species has become established, 

Ricciardi and Rasmussen (1998) identified C. curvispinum as a species likely to be transported to the 

Great Lakes via ballast water. The discovery (but not subsequent establishment) of a related Ponto-
738

Caspian amphipod, Corophium mucronatum, in a benthic sample collected from Lake St. Clair in 1997, 

suggests that C. curvispinum may at least have the potential for introduction to the Great Lakes 

(Grigorovich and MacIsaac 1999, Ricciardi and MacIsaac 2000). Corophium spp. appear to be unaffected 

by flow-through salinity shock experiments (increase of roughly 5 ppt from ambient salinity), but undergo 

~35% mortality in empty-refill treatments after 48 hours of exposure (Johengen et al. 2005). However, 

given this species’ physiological salinity constraints, under current mandatory ballast water regulations 

(saltwater flushing of at least 30 ppt), the risk of its entry into the Great Lakes has been modeled as 

having low likelihood (Grigorovich et al. 2003).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Chelicorophium curvispinum is native to the Ponto-Caspian region and has spread throughout Europe (bij de 

Vaate et al. 2002).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U
739

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75
740

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 0
741

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

Unknown U

 In Europe, shipping—including transport by ballast water and hull fouling—has been the primary vector of 

dispersal of this species outside of its native range (den Hartog et al. 1992, Harris 1991, Leppäkoski and 

Olenin 2001, van der Velde et al. 2000). Introduction to Great Britain, for instance, likely occurred via ballast 

water released from ships trading with ports on the Elbe River in northern Germany (Harris 1991). The 

discovery of C. curvispinum west of the Rhine River system before it was discovered in the Rhine lends further 

support to shipping mediated spread (den Hartog et al. 1992), as this sort of “jump” dispersal is a common 

indicator of human-mediated transport (MacIsaac et al. 2001).

 The discovery (but not subsequent establishment) of a related Ponto-Caspian amphipod, Corophium 

mucronatum, in a benthic sample collected from Lake St. Clair in 1997, suggests that C. curvispinum may at 

least have the potential for introduction to the Great Lakes (Grigorovich and MacIsaac 1999, Ricciardi and 

MacIsaac 2000). 

 Corophium spp. appear to be unaffected by flow-through salinity shock experiments (increase of roughly 5 ppt 

from ambient salinity), but undergo ~35% mortality in empty-refill treatments after 48 hours of exposure 

(Johengen et al. 2005).

 However, given this species’ physiological salinity constraints, under current mandatory ballast water 

regulations (saltwater flushing of at least 30 ppt), the risk of its entry into the Great Lakes has been modeled as 

having low likelihood (Grigorovich et al. 2003).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 As Great Lakes shipping traffic commonly originates in areas where this species has become established, 

Ricciardi and Rasmussen (1998) identified C. curvispinum as a species likely to be transported to the Great 

Lakes via ballast water.
742

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
743

Chelicorophium curvispinum has a high probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

This species has been one of the most successful macroinvertebrate invaders in Europe, establishing 

populations much larger than those of any native invertebrate species within a few years of colonization 

(bij de Vaate et al. 2002, den Hartog et al. 1992, van den Brink et al. 1993). Densities have reached 

750,000 individuals/m2in some areas of the Rhine (van den Brink et al. 1993). With a high fecundity (see 

Ecology), reproducing populations are now established throughout all major European river systems and 

as far west as Great Britain (bij de Vaate et al. 2002). This species is able to readily disperse through 

ballast water transport, ship hull fouling, passive drift, and active migration (van Riel et al. 2006, van der 

Velde et al. 2000), with secondary spread across Europe occurring in a pattern similar to, though at a 

much slower rate than, that of the zebra mussel (Tittizer et al. 1994).

Chelicorophium curvispinum is a non-specific feeder (bij de Vaate et al. 2002), filtering diatoms, organic 

particles, and small minerals from the water column. Its superior competitive abilities—including spatial 

adaptation, gregarious behavior, and relatively short lifespan and generation time—have contributed to 

this species’ invasion success (bij de Vaate et al. 2002, van den Brink et al. 1993). Competition with other 

macroinvertebrate species has been well documented, most notably with the highly successful Great 

Lakes invader, the zebra mussel (Dreissena polymorpha) (see Impacts).

The water temperature (up to 31.8°C) and salinity (<6 ppt) ranges tolerated by C. curvispinum are well 

within those of the Great Lakes and have allowed this species to be extremely successful in invasions of 

European rivers. Furthermore, C. curvispinum produces overwintering populations of smaller individuals 

(van den Brink et al. 1993) in waters of the Ponto-Caspian basin with very similar climatic conditions to 

those of the Great Lakes. However, its physiological tolerance is restricted by other factors, such as ion 

concentrations, oxygen availability, chlorophyll a concentrations, flow rate, and organic pollution levels 

(van der Velde et al. 2000). Individuals’ ability to retain and replace Na+and Clvaries among 

populations in different locations, and some populations have adapted to freshwater by means of lower 

ion permeability (Harris 1991, van der Velde et al. 2000). The changing conditions of the Rhine River 

throughout the 20th century, specifically increases in temperature and salinity, have created more suitable 

conditions for the invasion of foreign species originating in brackish waters, including C. curvispinum 

(den Hartog et al. 1992, van den Brink et al. 1993). These conditions are consistent with the physical 

changes forecast for the Great Lakes as a result of climate change (Rahel and Olden 2008), suggesting 

that this species may benefit from the resulting habitat shifts if introduced.

Chlorophyll a concentrations required by this species are currently present only in Lake Erie’s central 

basin, with less than 3 μg/L typically occurring in the other lake basins (USEPA 2012). This is consistent 

with the predicted distribution of C. curvispinum in the Great Lakes according to the Genetic Algorithm 

for Rule-Set Production (GARP) model, which incorporates variable chlorophyll a levels (USEPA 2008).

However, anoxic conditions have recently been present in the central basin of Lake Erie, dropping below 

0.5 mg/L at certain times of year (USEPA 2012). As a result, C. curvispinum distribution is likely to be 

restricted to areas with sufficient flow rates, high dissolved oxygen levels, and high phytoplankton 

productivity.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?
744

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Chelicorophium curvispinum is found in salt, brackish, and fresh water (de Kluijver and Ingalsuo 1999). It is 

originally a brackish water species occurring in salinities of less than 6 ppt (Romanova 1975), with the ability 

to tolerate very low salinities (Bayliss and Harris 1988, Harris and Bayliss 1990, Taylor and Harris 1986b, 

van den Brink et al. 1993). In Black Sea lagoons and estuaries, its distribution follows the 1.5 ppt isohaline 

(Bortkevitch 1988).

 The lethal minimum oxygen concentration for C. curvispinum is 0.300 mg O2/L (Dedyu 1980).

 This species is most successful in waters with relatively high ionic content and requires a minimum sodium ion 

(Na+) concentration of 0.5 mM (Harris and Aladin 1997).

 By some reports it is intolerant of heavy organic pollution levels (Harris and Muskó 1999, Jażdżewski 1980); by 

others it does well in organically polluted and eutrophic waters (van den Brink et al. 1993).

 The species is variable, adaptable and widely distributed (Crawford 1937).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 C. curvispinum produces overwintering populations of smaller individuals (van den Brink et al. 1993) in waters 

of the Ponto-Caspian basin with very similar climatic conditions to those of the Great Lakes.

 The lethal minimum oxygen concentration for C. curvispinum is 0.300 mg O2/L (Dedyu 1980).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0
745

Unknown U

6

 Chelicorophium curvispinum is a non-specific feeder (bij de Vaate et al. 2002), filtering diatoms, organic 

particles, and small minerals from the water column.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 Its superior competitive abilities—including spatial adaptation, gregarious behavior, and relatively short 

lifespan and generation time—have contributed to this species’ invasion success (bij de Vaate et al. 2002, van 

den Brink et al. 1993).

 Competition with other macroinvertebrate species has been well documented, most notably with the highly 

successful Great Lakes invader, the Zebra Mussel (Dreissena polymorpha) (van der Velde et al. 1994). In areas 

where these species have colonized together, C. curvispinum has either greatly reduced or eliminated D. 

polymorpha populations by smothering settled individuals and larvae with a thick layer of dense, muddy 

material used for construction of tubes (van der Velde et al. 1994). After introduction of C. curvispinum to the 

Rhine, Zebra Mussel populations were seen to decrease from 1000s of individuals/m2 to 100s of individuals/m2

within four years (Paffen et al. 1994, Rajagopal et al. 1998a, van der Velde et al. 1994).

 This species has outcompeted the freshwater isopod Asellus aquaticus and several species of chironomid larvae 

within their native ranges in the Rhine (Kinzelbach 1997).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

7

 Bij de Vaate et al. (2002) classify C. curvispinum as a species with high fecundity.
746

 Reproduction in C. curvispinum occurs from May to October in the Black Sea (Bortkevitch 1988) and from 

April to September in the Baltic (van den Brink et al. 1993).

 The number of eggs carried by females and total female body length are correlated, ranging in the Rhine from 3 

to 34 eggs (mean = 12) (van den Brink et al. 1993) and in Lake Balaton from 1 to 25 (mean = 6) (Muskó 1989, 

Muskó 1990).

 Related species, such as C. volutator, C. bonnelli., C. arenarium and C. insidiosum have only two generations 

each year. The egg clutch size of C. curvispinum showed a much higher increase with length than the number of 

eggs carried by C. insidiosum or by C. arenarium, C. volutator and C. bonnelli (van den Brink et al. 1993).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Three generations of brooded offspring are produced each year, following an overwintering period—the first in 

April to May, the second in June to July, and the third in September to October (den Hartog et al. 1992).

 In addition, this species has a short developmental time (a few weeks in summer) (van den Brink et al. 1993).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species is a Ponto-Caspian native, a region where climatic conditions are very similar to those of the 

Great Lakes.

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).
747

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 The water temperature (up to 31.8°C) and salinity (<6 ppt) ranges tolerated by C. curvispinum are well within 

those of the Great Lakes and have allowed this species to be extremely successful in invasions of European 

rivers.

 This species is most successful in waters with relatively high ionic content and requires a minimum sodium ion 

(Na+) concentration of 0.5 mM (Harris and Aladin 1997).

 Individuals’ ability to retain and replace Na+ and Cl- varies among populations in different locations, and 

some populations have adapted to freshwater by means of lower ion permeability (Harris 1991, van der Velde 

et al. 2000).

 By some reports it is intolerant of heavy organic pollution levels (Harris and Muskó 1999, Jażdżewski 1980); by 

others it does well in organically polluted and eutrophic waters (van den Brink et al. 1993).

 It seems to prefer waters with some water movement and higher oxygen levels, though is reported in areas 

without these conditions (van der Velde et al. 2000).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Chlorophyll a concentrations required by this species are currently present only in Lake Erie’s central basin, 

with less than 3 μg/L typically occurring in the other lake basins (USEPA 2012). This is consistent with the 

predicted distribution of C. curvispinum in the Great Lakes according to the Genetic Algorithm for Rule-Set 

Production (GARP) model, which incorporates variable chlorophyll a levels (USEPA 2008).

 However, anoxic conditions have recently been present in the central basin of Lake Erie, dropping below 0.5 

mg/L at certain times of year (USEPA 2012). As a result, C. curvispinum distribution is likely to be restricted to 

areas with sufficient flow rates, high dissolved oxygen levels, and high phytoplankton productivity.

 However, van den Brink et al. (1993) stated that the high organic pollution and eutrophication of the Rhine 

ecosystem provided ideal food for high fecundity, and found high population densities.
748

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 The changing conditions of the Rhine River throughout the 20th century, specifically increases in temperature 

and salinity, have created more suitable conditions for the invasion of foreign species originating in brackish 

waters, including C. curvispinum (den Hartog et al. 1992, van den Brink et al. 1993).

 These conditions are consistent with the physical changes forecast for the Great Lakes as a result of climate 

change (Rahel and Olden 2008), suggesting that this species may benefit from the resulting habitat shifts if 

introduced.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

6

 Chelicorophium curvispinum is a non-specific feeder (bij de Vaate et al. 2002), filtering diatoms, organic 

particles, and small minerals from the water column.

 Both average clutch size (Rajagopal 1998b) and growth rate (Rajagopal 1998a) have been positively correlated 

with the availability of chlorophyll a, which leads to increased planktonic development and greater food 

availability (van der Velde et al. 2000). Chlorophyll a concentrations required by this species are currently 

present only in Lake Erie’s central basin, with less than 3 μg/L typically occurring in the other lake basins 

(USEPA 2012).
749

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by C. curvispinum.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
750

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 This species is an important food source for a variety of fish species, including sculpin, eels, perch, ruffe, and 

pike perch, all of which are represented in the Great Lakes (van den Brink et al. 1993). Other predators include 

birds, crayfish, and other predatory macroinvertebrates (Biró 1974, Kelleher et al. 1998, 1999; Marguillier et 

al. 1998). However, the extent to which this predation will have an effect on potential populations of C. 

curvispinum in the Great Lakes is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6
751

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species has been one of the most successful macroinvertebrate invaders in Europe, establishing 

populations much larger than those of any native invertebrate species within a few years of colonization (bij de 

Vaate et al. 2002, den Hartog et al. 1992, van den Brink et al. 1993). Densities have reached up to 750,000 

individuals/m2in some areas of the Rhine (van den Brink et al. 1993). Reproducing populations are now 

established throughout all major European river systems and as far west as Great Britain (bij de Vaate et al. 

2002).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 This species is able to readily disperse through ballast water transport, ship hulls fouling, passive drift, and 

active migration (van Riel et al. 2006, van der Velde et al. 2000), with secondary spread across Europe 

occurring in a pattern similar to, though at a much slower rate than, that of the zebra mussel (Tittizer et al. 

1994).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0
752

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 103

>100 High Adjustments

B. Critical species A*(1- 0%) 103

51-99 Moderate C. Natural enemy B*(1- 0%) 103

Control measures C*(1- 0%) 103

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

Chelicorophium curvispinum has the potential for moderate environmental impact if introduced to 

the Great Lakes.

In invasions across Europe, high densities of C. curvispinum have been associated with reductions in 

macroinvertebrate species richness (van den Brink et al. 1991, van der Velde et al. 1998). This species has 

outcompeted several native macroinvertebrates, including the Great Lakes invader Dreissena polymorpha

(Zebra Mussel) (van der Velde et al. 1994). Additionally, this species has outcompeted the freshwater 

isopod Asellus aquaticus and several species of chironomid larvae within their native ranges in the Rhine 

(Kinzelbach 1997). Competition for food with other filter feeding species is expected if this species were 

to reach the Great Lakes (van den Brink et al. 1993), though competition for space (due to the smothering 

of settled individuals with their tube-building material and creating future unsuitable settling surface) has 

been the primary factor in reducing macroinvertebrate abundance in invaded areas of the Rhine (van der 

Velde et al. 1994). This species may have prevented the Great Lakes non-native Echinogammarus ischnus
753

from forming dense populations in the Rhine (where it is native) due to the smothering of potential hard 

substrate settlement areas (van der Velde et al. 2000), and the production of these mud tubes has 

additionally led to the displacement of native filter-feeding caddisflies (Hydropsyche sp.) (van der Velde 

et al. 1994).

This species plays an important role in the food web of the Rhine as well as other invaded areas, driving 

prey switching among some fish predators (van der Velde et al. 2000). Due to the reduction in 

invertebrate diversity in areas where C. curvispinum has invaded, a decline in the number of predators, 

such as leeches, has been observed (van der Velde et al. 2000). It has been hypothesized that the 

prevalence of C. curvispinum in invaded rivers may lead to alterations of entire food webs (Ricciardi and 

Rasmussen 1998), although its role as a food source for predatory macroinvertebrates (e.g., as crayfish) 

requires further study (Rajagopal et al. 1998a).

The population explosion of C. curvispinum in the Rhine from 1989-1991 coincided with a decrease in 

the levels of total organic carbon and total suspended matter (van den Brink et al. 1993). An increase in 

water clarity due to particle filtration by large populations of C. curvispinum is thought to have expanded 

the euphotic zone, increasing the transfer of energy and nutrients to the benthos and leading to greater 

levels of benthic production (Rajagopal et al. 1998a).

There is little or no evidence to support that Chelicorophium curvispinum has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

The resulting reduction in macroinvertebrate abundance associated with C. curvispinum invasions may 

have a negative impact on the diet of native fish species; however, predation pressure on exotic 

amphipods changes rapidly depending upon prey availability. Hence, further biological monitoring is 

necessary in order to determine the full extent of the impact of C. curvispinum on fish diet and subsequent 

effect on commercial fisheries (van der Velde et al. 2000).

Chelicorophium curvispinum has the potential for moderate beneficial effect if introduced to the 

Great Lakes.

In areas where these species have colonized together, C. curvispinum has either greatly reduced or 

eliminated D. polymorpha populations by smothering settled individuals and larvae with a thick layer of 

dense, muddy material used for construction of tubes (van der Velde et al. 1994). After introduction of C. 

curvispinum to the Rhine, zebra mussel populations were seen to decrease from 1000s of individuals/m2

to 100s of individuals/m2 within four years (Paffen et al. 1994, Rajagopal et al. 1998a, van der Velde et al. 

1994). This species has also potentially prevented populations of another Great Lakes invader, 

Echinogammarus ischnus, from forming dense populations in the Rhine (van der Velde et al. 2000). 

While populations of previously established invaders in the Great Lakes may be reduced by the 

introduction of this species, its effectiveness as a control agent is likely to be limited due to independent 

negative ecological consequences.

Chelicorophium curvispinum is fed upon by many fish genera, including those with species represented in 

the Great Lakes (van den Brink et al. 1993). In the past, this species was intentionally introduced to large 

rivers in the Ponto-Caspian region to increase faunal diversity and to feed fish (Jażdżewski 1980, 

Karpevich 1975, Mordukhaĭ-Boltovskoĭ 1979a). However, its potential beneficial impact as a food source 

for commercial fisheries in the Great Lakes is unknown.

Lastly, while water clarity is increased by the presence of large populations of this species (Rajagopal 

1998a), the positive impact of this effect for humans and/or native species is likely limited.
754

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 In invasions across Europe, high densities of C. curvispinum have been associated with reductions in 

macroinvertebrate species richness (van den Brink et al. 1993). This species has outcompeted several native 

macroinvertebrates, including the Great Lakes invader Dreissena polymorpha (Zebra Mussel) (van der Velde et 

al. 1994).

 Additionally, this species has outcompeted the native freshwater isopod Asellus aquaticus and several species of 

chironomid larvae within their native ranges (Kinzelbach 1997).

 Competition for food with other filter feeding species is expected if this species were to reach the Great Lakes 

(van den Brink et al. 1993), though competition for space (due to the smothering of settled individuals with their 

tube-building material and creating future unsuitable settling surface) has been the primary factor in reducing 

macroinvertebrate abundance in invaded areas of the Rhine (van der Velde et al. 1994).

 This species may have prevented the Great Lakes non-native Echinogammarus ischnus from forming dense 

populations in the Rhine (where it is native) due to the smothering of potential hard substrate settlement areas 

(van der Velde et al. 2000).

 The production of these mud tubes has additionally led to the displacement of native filter-feeding caddisflies 

(Hydropsyche sp.) (van der Velde et al. 1994).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

6
755

the food web)

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U

 This species plays an important role in the food web of the Rhine as well as other invaded areas, driving prey 

switching among some fish predators (van der Velde et al. 2000).

 Due to the reduction in invertebrate abundance in areas where C. curvispinum has invaded, a decline in the 

number of predators, such as leeches, has been observed (van der Velde et al. 2000).

 It has been hypothesized that the prevalence of C. curvispinum in invaded rivers may lead to alterations of 

entire food webs (Ricciardi and Rasmussen 1998), although its role as a food source for predatory 

macroinvertebrates (e.g., crayfish) requires further study (Rajagopal et al. 1998a).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 √

Not significantly 0

Unknown U

 The population explosion of C. curvispinum in the Rhine from 1989-1991 coincided with a decrease in the 

levels of total organic carbon and total suspended matter (van den Brink et al. 1993).

 An increase in water clarity due to particle filtration by large populations of C. curvispinum is thought to have 

expanded the euphotic zone, increasing the transfer of energy and nutrients to the benthos and leading to 

greater levels of benthic production (Rajagopal et al. 1998a).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 6
756

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 3

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1
757

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0

Unknown U √

 The resulting reduction in macroinvertebrate abundance associated with C. curvispinum invasions may have a 

negative impact on the diets of native fish species, however, predation pressure on exotic amphipods changes 

rapidly depending upon prey availability. Hence, further biological monitoring is necessary in order to 

determine the full extent of the impact of C. curvispinum on fish diet and subsequent effect on commercial 

fisheries (van der Velde et al. 2000).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U
758

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired level 

of effectiveness

1 √

Not significantly 0

Unknown U

 In areas where these species have colonized together, C. curvispinum has either greatly reduced or eliminated 

D. polymorpha populations by smothering settled individuals and larvae with a thick layer of dense, muddy 

material used for construction of tubes (van der Velde et al. 1994). After introduction of C. curvispinum to the 

Rhine, Zebra Mussel populations were seen to decrease from 1000s of individuals /m2to 100s of individuals/m2

within four years (Paffen et al. 1994, Rajagopal et al. 1998a, van der Velde et al. 1994, van der Velde et al. 

1998).

 This species has also potentially prevented populations of another Great Lakes invader, Echinogammarus 

ischnus, from forming dense populations in the Rhine (van der Velde et al. 2000).

 While populations of previously established invaders in the Great Lakes may be reduced by the introduction of 

this species, its effectiveness as a control agent is likely to be limited due to independent negative ecological 

consequences.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1
759

Not significantly 0 √

Unknown U

 Chelicorophium curvispinum is fed upon by many fish genera, including those with species represented in the 

Great Lakes (van den Brink et al. 1993). In the past, this species was intentionally introduced to large rivers in 

the Ponto-Caspian region to increase faunal diversity and to feed fish (Jażdżewski 1980, Karpevich 1975, 

Mordukhaĭ-Boltovskoĭ 1979). However, its potential beneficial impact as a food source for commercial fisheries 

in the Great Lakes is unknown.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0

Unknown U

 While water clarity is increased by the presence of large populations of this species (Rajagopal 1998a), the 

positive impact of this effect for humans and/or native species is likely limited.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1
760

Not significantly 0 √

Unknown U

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
761

Scientific Name: Dikerogammarus haemobaphes

Eichwalk, 1841

Common Name: Small-humped Amphipod

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Dikerogammarus haemobaphes has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Dikerogammarus haemobaphes has been proposed to be able to survive partial to complete ballast water 

exchange due to one reported natural occurrence in 17 ppt salinity waters (Grigorovich et al. 2003), but 

other estimates of this species’ salinity tolerance are more restrictive (0-8 ppt) (Ponomareva 1976). Based 

on the former, Grigorovich et al. (2003) assessed D. haemobaphes as having a high Great Lakes invasion 

risk mediated by both BOB and NOBOB vessels. However, the closely related European invader D. 

villosus exhibited 0% survival after 24 hours in 34 PSU empty-refill and flow-through salinity treatments 

(Santagata et al. 2008), suggesting that D. haemobaphes may be similarly impacted by current ballast 

water regulations.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
762

 Dikerogammarus haemobaphes is native to the Ponto-Caspian region and now present across European rivers 

and into the Baltic Sea (bij de Vaate et al. 2002).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U
763

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?
764

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Dikerogammarus haemobaphes has been proposed to be able to survive partial to complete ballast water 

exchange due to one reported natural occurrence in 17 ppt salinity waters (Grigorovich et al. 2003), but other 

estimates of this species’ salinity tolerance are more restrictive (0-8 ppt) (Ponomareva 1976). Based on the 

former, Grigorovich et al. (2003) assessed D. haemobaphes as having a high Great Lakes invasion risk 

mediated by both BOB and NOBOB vessels.

 However, the closely related European invader D. villosus exhibited 0% survival after 24 hours in 34 PSU 

empty-refill and flow-through salinity treatments (Santagata et al. 2008), suggesting that D. haemobaphes may 

be similarly impacted by current ballast water regulations.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1
765

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species has expanded its range from the Ponto-Caspian basin and is now present in coastal waters of the 

Baltic Sea, as well as connecting European river systems (bij de Vaate et al. 2002).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
766

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Dikerogammarus haemobaphes has a high probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

The climatic conditions of the native (Ponto-Caspian) and introduced (Baltic) ranges of D. haemobaphes

are very similar to those of the Great Lakes. While D. haemobaphes is able survive in moderately wide 

temperature and salinity ranges, as well as hypoxic conditions, it is primarily a freshwater, riverine 

species. Its westward spread through all major European river systems connecting the Ponto-Caspian with 

the Baltic may have been limited by salinity levels to inland water courses (bij de Vaate et al. 2002). 

Nevertheless, its physiological tolerances are well within conditions occurring in the Great Lakes. 

Increased salinization as a potential effect of climate change (Rahel and Olden 2008) may be 

inconsequential to this species’ establishment in the Great Lakes, as it tolerates salinities up to 8 ppt 

(Ponomareva 1976). Arbačiauskas (2002) hypothesized that oxygen concentration is the principal limiting 

factor in determining the survival and sustainability of populations of Ponto-Caspian amphipods. 

Therefore, anoxic conditions, as present in the central basin of Lake Erie (Summers 2001), may prevent 

D. haemobaphes from establishing in some regions of the Great Lakes.

Feeding plasticity, high reproductive capacity, relatively small eggs, short egg development time, fast 

sexual maturation, brooding, and production of multiple generations per year are factors thought to 

contribute to the invasion success of this species (Bacela et al. 2009, bij de Vaate et al. 2002). 

Dikerogammarus haemobaphes fecundity is moderate compared to that of the invasive gammarids D. 

villosus and P. robustoides (Bacela et al. 2009), but it is high in relation to invasive European gammarids 

as a group (Grabowski et al. 2007a). The autumn generation typically overwinters, but in thermally 

polluted waters (e.g., hydroelectric cooling water discharge), this species may reproduce year round 

(Kiticyna 1980); therefore, warming waters as a result of climate change could be beneficial to its 

invasion success.

Regarding interspecific interactions, D. haemobaphes has outcompeted and displaced native European 

gammarids, but it has also experienced declines in European waterways following expansion of the 

related invasive amphipod Dikerogammarus villosus (Jażdżewski et al. 2004, Jażdżewski et al. 2005,

Kinzler et al. 2009). Dikerogammarus haemobaphes constitutes a food base for multiple fish genera 

(Grabowska and Grabowski 2005, Kelleher et al. 1998, Kelleher et al. 2000, Kostrzewa and Grabowski 

2003), though the extent to which this predation will have an effect on potential populations in the Great 

Lakes is unknown.

Invasive dreissenid mussels are likely to facilitate the establishment of D. haemobaphes in the Great 

Lakes, as this amphipod preferentially colonizes living zebra mussel shells over other substrate types, 

including empty shells and stones, in the Ponto-Caspian and other newly invaded regions.

The dispersal rate of D. haemobaphes across Europe is similar to that of many other Ponto-Caspian 

invasive amphipods (D. villosus), spreading across the entire European continent in roughly 50 years (bij 

de Vaate et al. 2002).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES
767

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Dikerogammarus haemobaphes is able to tolerate a relatively wide temperature range (6-30°C) (Kiticyna 

1980).

 Although Grigorovich et al. (2003) listed D. haemobaphes as occurring naturally in waters of 17 ppt salinity, 

this species is most likely restricted to 0-8 ppt (Ponomareva 1976). It is more commonly found near mouths of 

freshwater rivers (typically 1-1.5 PSU) than in more saline waters (2-8 PSU) (Grabowski et al. 2006,

Jażdżewski et al. 2002, Jazdewski et al. 2004, Jażdżewski et al. 2005).

 The lethal minimum oxygen concentration for D. haemobaphes is 0.345 mg O2/L; while such conditions are 

considered hypoxic, several other Ponto-Caspian amphipods invaders in the Baltic Sea can tolerate even lower 

oxygen concentrations (Dedyu 1980).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 This species is able to overwinter in its native European range (Ponto-Caspian) by producing an autumn 

generation that survives to reproduce in the following spring (Bacela et al. 2009).

 The lethal minimum oxygen concentration for D. haemobaphes is 0.345 mg O2/L (Dedyu 1980).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0
768

Unknown U

9

 Dikerogammarus haemobaphes is a dietary generalist (bij de Vaate et al. 2002), feeding on detritus, sediments, 

unicellular and filamentous algae, and other small crustaceans.

 Its predation intensity on animal food sources such as chironomids, oligochaetes, crustaceans, and mayflies 

increases during the summer months when water temperatures are higher (van der Velde et al. 2009).

 Feeding plasticity is one aspect that may explain its rapid expansion across Europe (Bacela et al. 2009).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

5

 Dikerogammarus haemobaphes has outcompeted and displaced native European gammarids, but it has also 

experienced declines (been outcompeted itself) in European waterways following expansion of the related 

invasive D. villosus (Kinzler et al. 2009).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Dikerogammarus haemobaphes fecundity is moderate compared to that of the invasive gammarids D. villosus 

and P. robustoides (Bacela et al. 2009), but it is high in relation to invasive European gammarids as a group 

(Grabowski et al. 2007).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?
769

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 High reproductive capacity, relatively small eggs, short egg development time, fast sexual maturation, 

brooding, and production of multiple generations per year are factors thought to contribute to the invasion 

success of this species in Europe (Bacela et al. 2009, bij de Vaate et al. 2002).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The climatic conditions of the native (Ponto-Caspian) and introduced (Baltic) ranges of D. haemobaphes are 

very similar to those of the Great Lakes.

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0
770

Unknown U

8

 Dikerogammarus haemobaphes is euryoecious (adapted to varied ecological conditions), preferring to inhabit 

solid substrates, macrophytes, and filamentous algae in large rivers and lakes (Kiticyna 1980, Muskó 1994).

 It is most commonly found near mouths of freshwater rivers (typically 1-1.5 PSU) than in more saline waters 

(2-8 PSU) (Grabowski et al. 2006, Jażdżewski et al. 2002, Jażdżewski et al. 2004, Jażdżewski et al. 2005).

 Abiotic factors and climatic conditions of the native and introduced ranges of this species are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Arbačiauskas (2002) hypothesized that oxygen concentration is the principal limiting factor in determining the 

survival and sustainability of populations of Ponto-Caspian amphipods. Therefore, anoxic conditions, as 

present in the central basin of Lake Erie (Summers 2001), may prevent D. haemobaphes from establishing in 

some regions of the Great Lakes.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

7

 In thermally polluted waters (e.g., hydroelectric cooling water discharge), this species may reproduce year 

round (Kiticyna 1980); therefore, warming waters as a result of climate change could be beneficial to its 

invasion success.
771

 Increased salinization as a potential effect of climate change (Rahel and Olden 2008) may be inconsequential to 

this species’ establishment in the Great Lakes, as it tolerates salinities up to 8 ppt (Ponomareva 1976).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 This species is a dietary generalist (bij de Vaate et al. 2002), feeding on detritus, sediments, unicellular and 

filamentous algae, and other small crustaceans. None of these food sources are limiting in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by D. haemobaphes.
772

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

9

 Dikerogammarus haemobaphes is frequently found in association with another Ponto-Caspian invader, 

Dreissena polymorpha, preferring to settle on living zebra mussel shells over other substrate types, including 

empty shells and stones, in the Ponto-Caspian and other newly invaded regions (bij de Vaate et al. 2002, Kobak 

et al. 2009, Muskó 1993, Wawrzyniak- Wydrowska and Gruszka 2005).

 Dreissenid shell surface properties are thought to attract D. haemobaphes, with a distinct preference shown for 

living mussels over empty shells as well as clean shells over varnished shells (Kobak et al. 2009).

 Additionally, the living mussel shells serve as a better habitat for prey items, including chironomids (Botts et al. 

1996, Mörtl and Otto-Rothhaupt 2003, Ricciardi et al. 1997, Stewart et al. 1998).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U
773

 Dikerogammarus haemobaphes constitutes a food base for multiple fish genera (Grabowska and Grabowski 

2005, Kelleher et al. 1998, Kelleher et al. 2000, Kostrzewa and Grabowski 2003), though the extent to which 

this predation will have an effect on potential populations in the Great Lakes is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Dikerogammarus haemobaphes was first observed in a non-native location in 1976, when it migrated up the 

Danube River through the southern corridor and arrived in the German section of the upper Danube (Tittizer 

1996). It was subsequently observed in the Main-Danube canal in 1993 (Schleuter et al. 1994), through which it 

migrated to the North Sea basin via the Rhine River (Schöll et al. 1995). In 1997, this species was first 

discovered in Poland in the Vistula River (Konopacka 1998). Around this time, it was also discovered in the 

Notec and Bug rivers, tributaries of the Oder and Vistula rivers, respectively (Jażdżewski and Konopacka 2000, 

Jażdżewski and Konopacka 2002, Jażdżewski et al. 2002). Dikerogammarus haemobaphes was observed in the 

central and southern corridors of the Volga River, as well as the upper Volga basin, for the first time around 

the year 2000 and quickly became abundant (L’vova et al. 1996, Jażdżewski et al. 2004). It is now also present 

in the Great Masurian Lakes (Jażdżewski 2003) and in a small mesotrophic lake in the Vistula valley 

(Grabowski and Bacela 2005).

 The westward spread of D. haemobaphes through all major European river systems connecting the PontoCaspian with the Baltic may have been limited by salinity levels to inland water courses (bij de Vaate et al. 

2002).
774

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 The dispersal rate of D. haemobaphes across Europe is similar to that of many other Ponto-Caspian invasive 

amphipods (e.g., D. villosus), spreading across the entire European continent in roughly 50 years (bij de Vaate 

et al. 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 115

>100 High Adjustments

B. Critical species A*(1- 0%) 115

51-99 Moderate C. Natural enemy B*(1- 0%) 115

Control measures C*(1- 0%) 115
775

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impact of Dikerogammarus haemobaphes if 

introduced to the Great Lakes is inadequate to support proper assessment.

Upon introduction to new waterways, D. haemobaphes has outcompeted native European gammarids, 

including displacing Chaetogammarus ischnus in the lower Vistula Lagoon (Jażdżewski et al. 2004, 

2005). Additionally, D. haemobaphes is a vector of gregarines, a group of unicellular parasites that infect 

the intestines of invertebrates (Codreanu-Balcescu 1995). However, the transfer of these parasites to 

native species is unknown (Grabowski et al. 2007b).

There is little or no evidence to support that Dikerogammarus haemobaphes has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Dikerogammarus haemobaphes poses a threat to human health or water 

quality. There is no evidence that this negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Dikerogammarus haemobaphes has the potential for 

significant beneficial effects if introduced to the Great Lakes.

Dikerogammarus haemobaphes constitutes a food base for perches, gobies, and eels (Grabowska and 

Grabowski 2005, Kelleher et al. 1998, Kelleher et al. 2000, Kostrzewa and Grabowski 2003). It was 

intentionally stocked in large European rivers prior to the 1970s to enhance the fish fauna (Karpevich 

1975, Jażdżewski 1980, bij de Vaate et al. 2002).

POTENTIAL ENVIRONMENTAL IMPACT
776

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0

Unknown U √

 Dikerogammarus haemobaphes is a vector of gregarines, a group of unicellular parasites that infect the 

intestines of invertebrates (Codreanu-Balcescu 1995). However, the transfer of these parasites to native species 

is unknown (Grabowski et al. 2007b).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Upon introduction to new waterways, D. haemobaphes has outcompeted native European gammarids, including 

displacing Chaetogammarus ischnus in the lower Vistula Lagoon (Jażdżewski et al. 2004, Jażdżewski et al. 

2005).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0 √

Unknown U
777

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
778

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √
779

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.
780

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U

 Dikerogammarus haemobaphes constitutes a food base for perches, gobies, and eels (Grabowska and 

Grabowski 2005, Kelleher et al. 1998, Kelleher et al. 2000, Kostrzewa and Grabowski 2003).

 This species was intentionally stocked in large European rivers prior to the 1970s to enhance the fish fauna (bij 

de Vaate et al. 2002, Karpevich 1975, Jażdżewski 1980).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 6
781

humans and/or native species

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
782

Scientific Name: Dikerogammarus villosus

Sowinsky, 1894

Common Name: Killer Shrimp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Dikerogammarus villosus has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Dikerogammarus villosus is native to the Ponto-Caspian region, an invasion donor “hot spot,” and has 

expanded its range throughout Western Europe. Due to its high tolerance to varying salinities, oxygen 

concentrations, and temperatures, D. villosus has been proposed to be a highly likely candidate for 

introduction to the Great Lakes via ballast water transport from European ships (Bruijs et al. 2001, Dick 

and Platvoet 2001, Dick et al. 2002, Grigorovich et al. 2003, Maclsaac 1999, Mills et al. 1993, Ricciardi 

and Rasmussen 1998). However, under current mandatory ballast water regulations (saltwater flushing of 

at least 30 ppt), the risk of entry for this species is likely reduced. Santagata et al. (2008) report 0% D. 

villosus survival after exposure to full strength seawater (34 PSU) for 24 hours in both empty-refill and 

flow-through ballast treatments. As a benthic amphipod able to bury in sediment (where conditions may 

be less saline), less stringent ballast water flushing and/or exchange is likely to have diminished 

effectiveness.

While there has been mention of hull fouling of ocean-going vessels as an alternate pathway of 

introduction (Devin and Beisel 2006), supporting evidence is unavailable at this time.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
783

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Dikerogammarus villosus is native to the Ponto-Caspian region and has spread throughout western Europe (bij 

de Vaate et al. 2002).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 At present, it is unlikely for D. villosus to be introduced into the Great Lakes via hitchhiking on recreational 

gear or boat structures that enter the Lakes from other parts of the United States or Canada. However, as this 

was the most probable vector for its introduction in Lake Garda, Italy—tourist boats coming from central 

European lakes (Casellato et al. 2005)—it could become a potential vector if the species arrives and becomes 

established on the North American continent.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
784

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
785

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Due to its high tolerance to varying salinities, oxygen concentrations, and temperatures, D. villosus has been 

proposed to be a highly likely candidate for introduction to the Great Lakes via ballast water transport from 

European ships (Bruijs et al. 2001, Dick and Platvoet 2001, Dick et al. 2002, Grigorovich et al. 2003, Maclsaac 

1999, Mills et al. 1993, Ricciardi and Rasmussen 1998).

 Under current mandatory ballast water regulations (saltwater flushing of at least 30 ppt), the risk of entry for 

this species is likely reduced. Santagata et al. (2008) report 0% D. villosus survival after exposure to full 

strength seawater (34 PSU) for 24 hours in both empty-refill and flow-through ballast treatments.

 As a benthic amphipod able to bury in sediment (where conditions may be less saline), less stringent ballast 

water flushing and/or exchange is likely to have diminished effectiveness.
786

 While there has been mention of hull fouling of ocean-going vessels as an alternate pathway of introduction 

(Devin and Beisel 2006), supporting evidence is unavailable at this time.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Dikerogammarus villosus is native to the Ponto-Caspian region, an invasion donor “hot spot,” and has 

expanded its range throughout Western Europe. Ballast water of transoceanic shipping has been considered a 

likely invasion vector to the Great Lakes (Dick et al. 2002).

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
787

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Dikerogammarus villosus has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Dikerogammarus villosus has not yet been recorded in the Great Lakes, but this species has a history of 

successful invasions throughout Europe (Devin et al. 2001). In addition to a physiology that facilitates 

ballast water transport (relatively wide temperature and salinity tolerance), this species possesses many 

advantageous life history traits conducive to successful invasions, including: short generation time, rapid 

growth rate, female-biased sex ratio, early sexual maturity, high fecundity, brooding, production of 

multiple generations per year, exceptional predatory and competitive capabilities, ecological plasticity, 

and large size compared to related species (bij de Vaate et al. 2002, Bruijs et al. 2001, Devin and Beisel 

2006, Devin et al. 2004, Dick and Platvoet 2000, Wijnhoven et al. 2003). These characteristics, combined 

with abundant potential food sources, make D. villosus a species expected to have high potential for 

spread if introduced to the Great Lakes ecosystem (Devin et al. 2003 and 2004, Dick and Platvoet 2000, 

Dick et al. 2002, Grigorovich et al. 2003, MacIsaac et al. 2001, Ricciardi and Rasmussen 1998). Its 

propagule pressure during the shipping season (May-October) is likely to be high, as this period overlaps 

with D. villosus’ reproductive peak (May/June) (Pöckl 2009). Following introduction, this species is also 

likely to spread by hitchhiking on recreational gear, boats, or trailers, as was a probable vector for its 

introduction to Lake Garda, Italy (Casellato et al. 2005).

Climatic conditions (e.g., temperature, precipitation, seasonality) and abiotic factors (e.g., pollution, water 

temperature, salinity, pH, nutrient levels and current) relevant to the success of D. villosus in its native 

and introduced ranges are similar to those in the Great Lakes. One such adaptation enabling this species to 

overwinter is that its oxygen demand is greatly reduced at temperatures around 1°C (Wijnhoven et al. 

2003).

A strong ecological connection exists between D. villosus and other Great Lakes invaders from the PontoCaspian, such as Dreissena polymorpha; under the theory of “invasional meltdown,” it has been predicted 

that invasion of the killer shrimp will be facilitated by these companion species (Devin et al. 2003, Dick 

and Platvoet 2000 and 2002, Ricciardi and Rasmussen 1998). For instance, beds of D. polymorpha may 

facilitate establishment of this large amphipod by providing colonization substrate (Devin et al. 2003, 
788

Dick et al. 2002). Dikerogammarus villosus also exhibits variable morphology and coloration (Nesemann 

et al. 1995, Pjatakova and Tarasov 1996), which could facilitate its concealment and establishment in new 

environments.

Increased water temperature as a result of climate change is likely to enhance breeding, as has been 

observed with its relative D. haemobaphes (Kiticyna 1980). However, although D. villosus has broad 

environmental tolerances, particularly with respect to high salinity, it is not known to survive in waters 

warmer than 35°C and may not typically survive prolonged exposure to temperatures in excess of 27°C 

(Bruijs et al. 2001, Maazouzi et al. 2011, van der Velde et al. 2009, Wijnhoven et al. 2003). This species 

prefers temperatures from 5 to 15°C and exhibits a limited potential to adjust to waters warmer than 20°C 

(Maazouzi et al. 2011).

The dispersal rate of this species across Europe is similar to that of many other Ponto-Caspian invasive 

amphipods (e.g., Dikerogammarus haemobaphes), spreading across the entire European continent in 

roughly 50 years (bij de Vaate et al. 2002).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Dikerogammarus villosus is able to tolerate temperatures from 0-35°C, with an optimal temperature range of 

5-15°C (Bruijs et al. 2001, Maazouzi et al. 2011, van der Velde et al. 2009, Wijnhoven et al. 2003).

 It naturally occurs at 17 ppt but can tolerate salinities ranging from 0 to 20 ppt (Bruijs et al. 2001, Grigorovich 

et al. 2003). While able to survive short exposure (3 hours) to full strength seawater, D. villosus experiences 

100% mortality when exposed to 34 PSU (practical salinity units) for 24 hours (Santagata et al. 2008).

 The minimum lethal oxygen concentration for this species is 0.380 mg O2/L; while such conditions are 

considered hypoxic, other Ponto-Caspian amphipods invaders in the Baltic Sea can tolerate even lower oxygen 

concentrations (Dedyu 1980).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 3
789

it is not known as an overwintering species)

Unlikely 0

Unknown U

8

 Oxygen demand for this species is greatly reduced at temperatures around 1°C (Wijnhoven et al. 2003).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Dikerogammarus villosus is an omnivorous predator of many macroinvertebrates, including other gammarids, 

and is also able to collect detritus and to filter out suspended algae (Mayer et al. 2008). It exhibits a 

cannibalistic nature by occasionally eating conspecific newborns and weak adults (Devin and Beisel 2006, Dick 

and Platvoet 2000, Dick et al. 2002, Mordukhaĭ-Boltovskoĭ 1979a, Platvoet et al. 2009).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Dikerogammarus villosus is a fierce predator and superior competitor. It eats and displaces other amphipods 

and is predicted to greatly reduce amphipod diversity in a variety of North American freshwater habitats,

particularly in the Great Lakes where its invasion has been facilitated by an “invasional meltdown” (Dick et al. 

2002, Dick and Platvoet 2000, Ricciardi and Rasmussen 1998).

 In the Netherlands, D. villosus has threatened the European native amphipod species Gammarus duebeni, but it 

has also controlled populations of the North American invader G. tigrinus (Dick and Platvoet 2000).
790

 Dikerogammarus villosus is thought to have displaced additional Dikerogammarus invaders (D. bispinosus and 

D. haemobaphes) in the Danube River (Müller et al. 2002). This species also has the potential to consume eggs 

or juvenile stages of small fish, causing potential concern for game fish populations if introduced to the Great 

Lakes (Devin and Beisel 2006).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

8

 Dikerogammarus villosus is reproductive year round in its native range (Devin et al. 2004, MordukhaĭBoltovskoĭ 1979a). Mean fecundity is around 30 eggs per female; however, females can to lay up to 194 eggs 

clutch, giving this species the highest fecundity of the European gammarids (Devin et al. 2004, Kley and Maier 

2003, Kley and Maier 2006, Pöckl 2007).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 Rapid growth and sexual maturation (leading to short generation time), brooding, production of multiple 

generations per year, and a female-biased sex ratio increasing reproductive capacity of populations are factors 

thought to contribute to the invasion success of this species in Europe (bij de Vaate et al. 2002, Devin et al. 

2004).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
791

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The climatic conditions of the native (Ponto-Caspian) and introduced (Baltic) ranges of D. villosus are very 

similar to those of the Great Lakes.

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Dikerogammarus villosus inhabits fresh/brackish water, lakes, rivers, and canals in areas with low current 

velocity (Devin and Beisel 2006). It can adapt to a wide variety of substrates as well as a wide range of 

temperature, salinity, and oxygen levels.

 Dikerogammarus villosus is able to tolerate temperatures from 0-35°C, with an optimal temperature range of 

5-15°C (Bruijs et al. 2001, Maazouzi et al. 2011, van der Velde et al. 2009, Wijnhoven et al. 2003). It can 

tolerate salinities ranging from 0 to 20 ppt (Bruijs et al. 2001, Grigorovich et al. 2003).

 Abiotic factors and climatic conditions of the native and introduced ranges of this species are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3
792

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 This species attaches itself to fastened banks, sheet-pile walls, and surface algae mats and can inhabit any 

substrate except sand (Crosier et al. 2011, Devin and Beisel 2006). It can also anchor itself within deep rock 

pools and under porous stones (Nesemann et al. 1995). In the lower Rhine, this species reaches its highest 

densities on hard substrates, primarily boulders, rocks, and pebbles within 3 meters of the shoreline (Kelleher 

et al. 1998, Platvoet et al. 2009). Different size classes of individuals tend to separate spatially, with the 

smallest individuals typically found on roots or macrophytes and larger individuals found in cobble (Mayer et 

al. 2008).

 The ability of D. villosus to occupy a range of habitats and wide environmental tolerances allows it to colonize 

the preferred habitats of both native and exotic species in Europe (Dick and Platvoet 2000).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

5

 The suitable yearly breeding period is likely to be lengthened with warmer water temperatures, as has been 

observed with its relative Dikerogammarus haemobaphes (Kiticyna 1980).

 Although D. villosus has broad environmental tolerances, particularly with respect to high salinity, it is not 

known to survive in waters warmer than 35°C and may not typically survive prolonged exposure to 

temperatures in excess of 27°C (Bruijs et al. 2001, Maazouzi et al. 2011, van der Velde et al. 2009, Wijnhoven 

et al. 2003). However, this species prefers temperatures from 5 to 15°C and exhibits a limited potential to 

adjust to waters warmer than 20°C (Maazouzi et al. 2011).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3
793

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Dikerogammarus villosus is an omnivorous predator of many macroinvertebrates, including other gammarids, 

and is also able to collect detritus and to filter out suspended algae (Mayer et al. 2008). It exhibits a 

cannibalistic nature by occasionally eating conspecific newborns and weak adults (Devin and Beisel 2006, Dick 

and Platvoet 2000, Dick et al. 2002, Mordukhaĭ-Boltovskoĭ 1979a, Platvoet et al. 2009).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by D. villosus.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

3
794

of encounter with this species assessed is hard to predict)

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

9

 A strong ecological connection exists between D. villosus and other Great Lakes invaders from the PontoCaspian, such as Dreissena polymorpha; under the theory of “invasional meltdown,” it has been predicted that 

invasion of the killer shrimp will be facilitated by these companion species (Devin et al. 2003, Dick and 

Platvoet 2000, Ricciardi and Rasmussen 1998). For instance, beds of D. polymorpha may facilitate 

establishment of this large amphipod by providing colonization substrate (Devin et al. 2003, Dick et al. 2002).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD
795

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species has been spreading rapidly since it began invading the Danube River in 1989. It has reached the 

Austro-German border, the Rhine estuary, and the Moselle River (Devin et al. 2001). It is also suspected to be 

the next successful invader of the Great Lakes (Bruijs et al. 2001, Ricciardi and Rasmussen 1998).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 The dispersal rate of this species across Europe is similar to that of many other Ponto-Caspian invasive 

amphipods (e.g., Dikerogammarus haemobaphes), spreading across the entire European continent in roughly 

50 years (bij de Vaate et al. 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this species 0
796

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 121

>100 High Adjustments

B. Critical species A*(1- 0%) 121

51-99 Moderate C. Natural enemy B*(1- 0%) 121

Control measures C*(1- 0%) 121

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: Low

Dikerogammarus villosus has the potential for high environmental impact if introduced to the Great 

Lakes.

Native to the lower Danube river system and Caspian Sea basin, D. villosus has recently invaded and 

spread throughout most of Western Europe, causing significant ecological disruption. Dikerogammarus 

villosus is a fierce predator and superior competitor. Its ability to eat and displace other amphipods has led 

to the prediction of a great reduction in amphipod diversity if introduced to a variety of North American 

freshwater habitats (Dick and Platvoet 2000). In the Netherlands, D. villosus has replaced many 

populations of the European native amphipod species Gammarus duebeni, as well as those of the North 

American invader G. tigrinus (Dick and Platvoet 2000). Dikerogammarus villosus has displaced an 
797

additional Dikerogammarus invader (D. haemobaphes) in portions of the Danube and Rhine rivers 

(Müller et al. 2002). This species also consumes eggs or juvenile stages of small fish, causing potential 

concern for game fish populations if introduced to the Great Lakes (Devin and Beisel 2006).

The short generation time, rapid growth rate, early sexual maturity, high fecundity, female-biased sex 

ratio, and large size of D. villosus as compared to related species make it a species expected to 

outcompete native species for resources (bij de Vaate et al. 2002). Dikerogammarus villosus also has been 

predicted to have serious direct and indirect negative environmental effects if introduced to the Great 

Lakes ecosystem (Dick et al. 2002).

Dikerogammarus villosus is host to several microsporidian parasites that may become emerging diseases 

in other crustaceans following host introduction (Bacela-Spychalska et al. 2012, Ovcharenko et al. 2010). 

Moreover, while many freshwater amphipods also serve as an intermediate host to acanthocephalan 

worms (parasites with birds and fish as final hosts), infection of D. villosus has not been confirmed 

(Médoc et al. 2006, in contrast to interpretation by Crosier et al. 2011 and others). 

There is little or no evidence to support that Dikerogammarus villosus has the potential for 

significant socioeconomic impacts if introduced to the Great Lakes.

The socio-economic impact of this species on invaded areas of Western Europe is largely unknown. 

However, the ability of this species to consume eggs or juvenile stages of small fish creates a potential 

concern for fishery populations (Devin and Beisel 2006).

There is little or no evidence to support that Dikerogammarus villosus has the potential for 

significant beneficial effects if introduced to the Great Lakes.

Dikerogammarus villosus has displaced populations of other invading amphipods in Europe, including D. 

haemobaphes (another potential Great Lakes invader) (Müller et al. 2002).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0 √

Unknown U
798

 Dikerogammarus villosus is host to several microsporidian parasites that may become emerging diseases in 

other crustaceans following host introduction (Bacela-Spychalska et al. 2012, Ovcharenko et al. 2010). 

 Moreover, while many freshwater amphipods also serve as an intermediate host to acanthocephalan worms 

(parasites with birds and fish as final hosts), infection of D. villosus has not been confirmed (Médoc et al. 2006, 

in contrast to interpretation by Crosier et al. 2011 and others).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 The short generation time, rapid growth rate, early sexual maturity, high fecundity, female-biased sex ratio, and 

large size of D. villosus as compared to related species make it a species expected to outcompete native species 

for resources (bij de Vaate et al. 2002). Dikerogammarus villosus also has been predicted to have serious direct 

and indirect negative environmental effects if introduced to the Great Lakes ecosystem (Dick et al. 2002).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 √

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0

Unknown U

 Dikerogammarus villosus is a fierce predator and superior competitor. Its ability to eat and displace other 

amphipods has led to the prediction of a great reduction in amphipod diversity if introduced to a variety of 

North American freshwater habitats (Dick and Platvoet 2000)

 In the Netherlands, D. villosus has replaced many populations of the European native amphipod species

Gammarus duebeni, as well as those of the North American invader G. tigrinus (Dick and Platvoet 2000). 

Dikerogammarus villosus has displaced an additional Dikerogammarus invader (D. haemobaphes) in portions 

of the Danube and Rhine rivers (Müller et al. 2002).

 This species also consumes eggs or juvenile stages of small fish, causing potential concern for game fish 

populations if introduced to the Great Lakes (Devin and Beisel 2006).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6
799

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 7

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
800

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0

Unknown U √

 The socio-economic impact of this species on invaded areas of Western Europe is largely unknown. However, 

the ability of this species to consume eggs and juvenile stages of small fish creates a potential concern for 

fishery populations (Devin and Beisel 2006).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?
801

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √
802

Not significantly 0

Unknown U

 Dikerogammarus villosus has displaced populations of other invading amphipods in Europe, including D. 

haemobaphes (another potential Great Lakes invader) (Müller et al. 2002).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U
803

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
804

Scientific Name: Echinogammarus warpachowskyi

G.O. Sars, 1894

Common Name: Scud

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Echinogammarus warpachowskyi has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Echinogammarus warpachowskyi has expanded its range from the Ponto-Caspian basin via human 

mediated vectors and is currently present in Northwest Russia, Gulf of Finland, as well as the Baltic Sea 

and its tributaries (Berezina 2007). This species occurs in ports that have direct trade connections with the 

Great Lakes (NBIC 2009).

Although Echinogammarus warpachowskyi posseses the ability to survive a wide range of salinities, it 

experiences partial mortality with exposure to full-strength seawater for 1 hour, and 100% mortality after 

48 hours (Santagata et al. 2008). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
805

 Echinogammarus warpachowskyi is native to the Ponto-Caspian region, invasive throughout northwest 

Russia, as far as the Gulf of Finland, as well as the Baltic Sea and its tributaries (Berezina 2007).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Echinogammarus warpachowskyi is native of the Ponto-Caspian region, invasive throughout Northwest 

Russia, as far as the Gulf of Finland, as well as the Baltic Sea and its tributaries (Berezina 2007).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U
806

 Echinogammarus warpachowskyi is not known to be sold.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Echinogammarus warpachowskyi is not known to be stocked.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
807

Unknown U

 Echinogammarus warpachowskyi is not cultured or transported through the Great Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This species is known to survive a wide range of salinity (0-20‰). However, with exposure to full-strength 

seawater, E. warpachowskyi will experience some mortality within an hour and 100% mortality within 48 

hours (Santagata et al. 2008).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1
808

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Echinogammarus warpachowskyi is invasive throughout Northwest Russia, the Gulf of Finland, and the 

Baltic Sea and its tributaries (Berezina 2007).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
809

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Echinogammarus warpachowskyi has a moderate probability of establishment if introduced to the 

Great Lakes (Confidence level: High).

The native and introduced ranges of Echinogammarus warpachowskyi have similar climate and abiotic 

conditions to that of the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). The 

Great Lakes has similar chlorophyll α concentrations as the Ponto-Caspian basin, which may facilitate 

Echinogammarus warpachowskyi establishment. With the progression of climate change, it is predicted 

that warmer waters and increased salinization of the Great Lakes will make it more similar to the 

conditions of the Ponto-Caspian (USEPA 2008). This species can tolerate mesotrophic and well-drained 

eutrophic lakes with high oxygen demands (Arbačiauskas 2005); it is likely to find a suitable habitat in 

the Great Lakes basin. This species is highly mobile, and may migrate to favorable conditions (Olenin and 

Leppäkoski 1999). Echinogammarus warpachowskyi may be capable of surviving low oxygen levels

under the ice during the winters of the Great Lakes; it can tolerate dissolved oxygen levels as low as 0.308 

mg/L (Arbačiauskas and Gumuliauskaité 2007). This species is omnivorous with shifting food strategies 

(Berezina 2007); Echinogammarus warpachowskyi is likely to find a food source in the Great Lakes. 

Echinogammarus warpachowskyi may be preyed on by fish in the Great Lakes, which may reduce its 

probability for establishment to some degree. It produces 2-3 broods each summer and the size of the 

brood is temperature dependent. The temperatures in the Great Lakes basin are slightly lower than the 

Ponto-Caspian region (USEPA 2008); broods of Echinogammarus warpachowskyi may be relatively 

smaller in the Great Lakes. However, warmer temperatures due to climate change may result in larger 

broods, aiding the establishment of this species. Historically, Echinogammarus warpachowskyi has 

spread locally from where it has been introduced (Arbačiauskas 2005). It is mobile (Olenin and 

Leppäkoski 1999). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6
810

 Echinogammarus warpachowskyi has high tolerances to salinity 0-20‰ (Berezina 2007, Grigorovich et al. 

2003). Echinogammarus warpachowskyi can tolerate mesotrophic or well-drained eutrophic lakes, with 

high oxygen demands (Arbačiauskas 2005).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Echinogammarus warpachowskyi is mobile, can migrate, and may retreat to more favorable conditions 

(Berezina 2007).

 This species’ lethal level of dissolved oxygen is 0.308 mg L-1 (Arbačiauskas and Gumuliauskaité 2007).

 This species originated in the Ponto-Caspian region, then spread within the Baltic and North Seas, so 

could likely withstand Great Lakes water temperatures (Grabowski et al. 2007a) .

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Echinogammarus warpachowskyi has an omnivorous diet with shifting/mixed food strategies (Berezina 

2007, Berezina et al. 2011)

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

3
811

in the Great Lakes)

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6

 With large E. warpachowskyi populations, native macroinvertebrates experience lower biodiversity and 

biomass, Echinogammarus warpachowskyi is likely to compete with other species (Arbačiauskas et al. 

2010). Echinogammarus warpachowskyi is omnivorous (Berezina 2007).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 Echinogammarus warpachowskyi has 2-3 broods in summer months, the brood size being temperature 

dependent (Berezina 2007). 

 Echinogammarus ischnus may produce 2 broods over the summer ( Kley and Maier 2003, Kley and Maier 

2006, Witt et al. 1997).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 Variation from species to species varies greatly, Echinogammarus warpachowskyi has no species-specific 

information. However, the congeneric species E. ischnus has similar reproduction methods and has spread 

widely in the Great Lakes.
812

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Echinogammarus warpachowskyi is native to the Ponto-Caspian region (Pinkster 1993). 

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 Abiotic factors and climatic conditions of the native and introduced ranges of this species are quite similar 

to the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0
813

Unknown U

9

 Echinogammarus warpachowskyi is able to establish in mesotrophic or well-drained eutrophic lakes with a 

high turnover rate, and prefers the lower littoral zone; establishment improves as lake area increases 

(Arbačiauskas 2005).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 The brood size of Echinogammarus warpachowskyi increases with temperature (Berezina 2007).

 Furthermore, this species tolerates salinities of 0-20‰ and exhibits morphological changes in different 

habitats (Berezina 2007).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6 

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Echinogammarus warpachowskyi is omnivorous (Berezina 2007).
814

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No critical species to this species were found.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
815

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Potential inoculum size and frequency are unknown.

 Intentional stocking of Echinogammarus warpachowskyi in Russia ended in the 1970s (Berezina 2007).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
816

Unknown U

4

 This species has been introduced from the Ponto-Caspian region to the Baltic and North Seas, where it has 

spread widely and rapidly (Grabowski et al. 2007b).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 This species has been introduced from the Ponto-Caspian region to the Baltic and North Seas, where it has 

spread widely and rapidly (Grabowski et al. 2007b).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 93

>100 High Adjustments

B. Critical species A*(1- 0%) 93
817

51-99 Moderate C. Natural enemy B*(1- 0%) 93

Control measures C*(1- 0%) 93

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

Echinogammarus warpachowskyi has the potential for a moderate environmental impact if 

introduced to the Great Lakes. 

Establishment of Echinogammarus warpachowskyi in other areas resulted in a 2-fold decrease in 

community diversity (Arbačiauskas et al. 2010). Due to the high fitness of Echinogammarus 

warpachowskyi, there is an increase in its biomass where it has been established. 

Echinogammarus warpachowskyi has the potential for low socio-economic impact if introduced to 

the Great Lakes. 

There is little or no evidence to support that Echinogammarus warpachowskyi has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Echinogammarus warpachowskyi poses a threat to human health or water 

quality. There is no evidence that this species negatively impacts infrastructure, economic sectors, 

recreational activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

Echinogammarus warpachowskyi has the potential for moderate beneficial effects if introduced to 

the Great Lakes.

Echinogammarus warpachowskyi has historically been used to increase the yields of certain types of fish 

(Berezina 2007). Establishment of Echinogammarus warpachowskyi may increase the production of 

perch in the Great Lakes.
818

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 The presence of this species has resulted in a two-fold decrease in community diversity, coupled with 

increased biomass (Arbačiauskas et al. 2010). Echinogammarus warpachowskyi is omnivorous (Berezina 

2007) and produces up to three broods during summer months (Arbačiauskas 2002).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival,

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 There may be one to one replacement of native amphipods (Berezina 2007). 
819

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 2

Total Unknowns (U) 4

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
820

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √
821

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.
822

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Echinogammarus warpachowskyi is used in Russia to supplement fish food web to bolster fisheries 

(Berezina 2007). Echinogammarus warpachowskyi may have similar effectiveness in charter fishing 

industry for perch. 

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Echinogammarus warpachowskyi is used in Russia to supplement fish food web to bolster fisheries 

(Berezina 2007). Echinogammarus warpachowskyi may have similar effectiveness for perch. 

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U
823

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
824

Scientific Name: Obesogammarus crassus

G.O. Sars

Common Name: Scud

Synonyms: Pontogammarus crassus, Niphargoides crassus

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Obesogammarus crassus has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential Pathway(s): Transoceanic Shipping

Currently, this species has not been found near waters connected to the Great Lakes, although it occurs in 

waters that have direct trade connections with the Great Lakes, such as the Baltic Sea (Sala et al. 2000,

NBIC 2009). Ballast water may be a potential vector for the introduction of Obesogammarus crassus 

(Ricciardi and Rasmussen 1998). It should be noted that where Obesogammarus crassus is introduced, it 

is frequently inoculated in high numbers by ballast water exchange (Grabowski et al. 2007b). The 

distribution of this species has already spread extensively beyond its native range; it has been introduced 

to western European waters via ballast water transport (Holdrich and Pöckl 2007). However, 

Obesogarmmarus crassus experiences complete mortality under flow through, full strength seawater for 

24 hours (Santagata et al. 2008).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, 

including connecting channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
825

 Obesogammarus crassus is a Ponto-Caspian species and has recently been found in the Curonian and Vistula 

Lagoon on the Russian part of the Baltic Sea (Berezina et al. 2011). This species does not occur near waters 

connected to the Great Lakes.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Obesogammarus crassus is not known to be able to attach or be transported by recreational gear, trailers, 

fauna, or flora. 

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √
826

Unknown U 

 Obesogammarus crassus is not known to be sold at aquarium/pet/garden stores or purchased for human 

consumption, ornamental, ethical, or cultural reasons. 

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Although stocking is one of the vectors of introduction of Obesogammarus crassus (Olenin et al. 2010), it is 

currently in the Baltic Sea so there is not enough interest to stock this species in the Great Lakes region, or at 

least it is not known to be stocked in the Great Lakes region at present. 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 100
827

region.

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Obesogammarus crassus is not known to be commercially cultured in or transported through the Great Lakes 

region.

 Whether Obesogammarus crassus is commercially cultured near the Baltic sea is unknown. 

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Ballast water has been identified as a vector of introduction of Obesogammarus crassus to the Great Lakes 

(Ricciardi and Rasmussen 1998). Obesogammarus crassus is also known to survive extreme temperatures 

and absence of light.

 Obesogammarus crassus is a euryhaline species (Ricciardi and Rasmussen 1998).

 Obesogammarus crassus is eurythermic and able to tolerate temperatures up to 30°C, although the optimal 

temperature for reproduction maybe lower (Olenin 2011).

 This species is recorded as being introduced to western European waters through ballast water transport 

(Holdich and Pöckl 2007).
828

 Experimental data suggests that O. crassus may experience 100% mortality after 3 hours with empty-refill 

ballast water exchange and after 24 hours with flow-through exchange with full strength seawater 

(Santagata et al. 2008). 

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Obesogammarus crassus occurs in waters from which shipping traffic to the Great Lakes originates (Sala et 

al. 2000), including the Baltic Sea.

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High 
829

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Obesogammarus crassus has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

The climatic conditions in the Ponto-Caspian and Baltic Sea are very similar to those in the Great Lakes. 

If Obesogammarus crassus is introduced, it can tolerate wide ranges of salinity and temperature. 

Obesogammarus crassus is eurythermic; able to tolerate temperatures up to 30°C (Olenin 2011). It can 

tolerate salinities from 0 to 20 psu (Santagata et al. 2008) and poorly oxygenated water about <2 mg/l O2 

(Olenin 2011). Obesogammarus crassus is an omnivore (Hänfling et al. 2011), meaning, it will find the 

available nutritive foods easily in the Great Lakes. It has non-specific food preference (bij de Vaate et al.

2002) and, thus, O. crassus is dietary generalist with a broad, assorted, and flexible diet. O. crassus has 

outcompeted various native species in the introduced area and has a high fecundity (bij de Vaate et al.

2002). 

O. crassus is inoculated in high numbers and very frequently by ballast water exchange (Grabowski et al.

2007b). This species has spread very extensively outside of its native range. O. crassus is known to 

spread from Lithuania in the Neman River to Curonian lagoon to Vistula lagoon to Oder Lagoon to Elbe 

River and now to Baltic Sea within ~50 years (bij de Vaate et al. 2002). However, due to ballast water 

management, the probability of establishment in the Great Lakes is low.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

6 
830

factors is narrower, unknown, or unreported.

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

9

 Obesogammarus crassus has salinity tolerance of 0 to 20 psu (Santagata et al. 2008). Obesogammarus crassus

is found in littoral zone of the Vistula lagoon and of the Dead Vistula, both brackish with salinities between 1-6 

psu, thus the presence of this species would only occur in oligohaline water bodies (Grabowski et al. 2007b). 

 Obesogammarus crassus can tolerate both fresh waters and brackish waters (Jażdżewski et al. 2004).

 Broad diet, high genetic variability, and tolerance of a fairly broad range of salinity, temperature and oxygen 

concentration has led to successful invasion and rapid increase in new habitats by this species (Surowiec and 

Dobrzycka-Krahel 2008)

 Obesogammarus crassus is eurythermic; able to tolerate temperatures up to 30°C, although the optimal 

temperature for reproduction maybe lower (Olenin 2011).

 Obesogammarus crassus can handle poorly oxygenated water about <2 mg/l O2 (Olenin 2011).

 Obesogammarus crassus is a euryoecious species; it can survive in a broad range of ecological living 

conditions (bij de Vaate et al. 2002). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

9

 Obesogammarus crassus can survive extremely low levels of oxygen, light, and temperature in the Great Lakes.

 Obesogammarus crassus can handle poorly oxygenated water about <2 mg/l O2 (Olenin 2011)

 Obesogammarus crassus is a euryoecious species; it can survive in a broad range of ecological living 

conditions (bij de Vaate et al. 2002). 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9
831

 Obesogammarus crassus has a non-specific food preference (bij de Vaate et al. 2002); this species is an 

omnivore (Hänfling et al. 2011).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 In the Curonian Lagoon, O. crassus has caused a severe reduction of the relative abundance of the former 

community dominant species or even population extinction within the ecosystem (Zaiko et al. 2010).

 The most visible change In the Vistula Lagoon is the increasing dominance of O. crassus (Grabowski et al.

2006).

 Based on the evidence presented in the above areas, this species is likely to outcompete species in the Great 

Lakes for available resources. 

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 One of the most fecund amphipods as reported (Grabowski et al. 2007b) is P. robustoides. The partial fecundity 

of P. robustoides is 5.10, while the partial fecundity of O. crassus and G roeselii is 2.87 and 0.87, respectively 

(Grabowski et al. 2007b). The fecundity of O. crassus is intermediated compared to other amphipods. 

 Obesogammarus crassus does not have high fecundity (bij de Vaate et al. 2002).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 9
832

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

4

 The female carries the eggs in a brood pouch, the mean brood size being 25.33. O. crassus has an average of 3 

generations per year (Grabowski et al. 2007b). 

 Obesogammarus crassus has a relatively short life span and generation time and does not have rapid growth 

nor early sexual maturity (bij de Vaate et al. 2002).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The climatic conditions in the native area, Ponto-Caspian, and introduced area, Baltic Sea, are similar to those 

in the Great Lakes region. 

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0
833

Unknown U

8

 The salinity in the native range is 0 to 18 psu (Paavola et al. 2005), and O. crassus has a tolerance of 0 to 20 

psu (Santagata et al. 2008), thus, it can easily find suitable habitats in fresh waters of Great Lakes.

 Obesogammarus crassus is eurythermic; able to tolerate temperatures up to 30°C, although the optimal 

temperature for reproduction maybe lower (Olenin 2011).

 No reports have been found on the pollution, nutrient levels, or currents.

 Abiotic factors and climatic conditions of the native and introduced ranges of this species are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 The native habitats of O. crassus is limnetic (Olenin et al. 2010), however, O. crassus is classified as nektobenthic ecofunctional group of invertebrates (Olenin et al. 2010). Thus, it has been found in both the benthic 

and limnetic zones. O. crassus can find suitable habitats in the Great Lakes. 

 Obesogammarus crassus has been found in both fresh waters and brackish waters (Grabowski et al. 2007b). 

 Obesogammarus crassus can handle poorly oxygenated water about <2 mg/l O2 (Olenin 2011). 

 Obesogammarus crassus is a euryoecious species; it can survive in a broad range of ecological living 

conditions (bij de Vaate et al. 2002).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0
834

Unknown U

9

 Obesogammarus crassus is likely to adapt to warmer water temperatures, shorter duration of ice cover, and 

increases salinization due to its wide environment tolerances. 

 Obesogammarus crassus has salinity tolerance of 0 to 20 psu (Santagata et al. 2008).

 Obesogammarus crassus is eurythermic; able to tolerate temperatures up to 30°C, although the optimal 

temperature for reproduction maybe lower (Olenin et al 2010).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Obesogammarus crassus has a non-specific food preference (bij de Vaate et al. 2002); this species is an 

omnivore (Hänfling et al. 2011).

 Obesogammarus crassus is a dietary generalist with a broad, assorted, and flexible diet, therefore, O. crassus is 

likely to find an appropriate food source including, species in the Great Lakes that may be considered potential 

food items.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in -80% total 
835

the Great Lakes and is not likely to be introduced points (at 

end)

Unknown U

9

 There has been no report of critical species being required by O. crassus during any of the stages of its life 

cycle, therefore, it can be concluded that O. crassus does not require any other species. 

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

U

 There has been no report of the establishment of O. crassus to be aided by the establishment and spread of 

another species already in the Great Lakes, therefore, it is unknown. 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U
836

 There is no report of natural enemy of O. crassus in the literature, therefore, it is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Ballast water transport allows for the introduction of O. crassus at distant places. Ballast water exchange 

creates a high propagule pressure at the points of discharge (Hänfling et al. 2011). 

 According to the reports from 1993 and 1996, the world’s major cargo vessels transfer 8–10 billion tons of 

ballast water per year, and that on average 3000 to 4000 species are transported by ships each day (Grabowski 

et al. 2007b). 

 The frequency of O. crassus in ballast tanks is unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

8

 Obesogammarus crassus is a Ponto-Caspian species that has been found in Curonian lagoon and Vistula 

lagoon (Berezina et al. 2011), in Szczecin lagoon and Elbe river in Germany (Grabowski et al. 2007b). It has 

spread from Caspian Sea to Black Sea and Baltic Sea areas.

 The central corridor of dispersal covers the route Dnieper River → Vistula River → Oder River → Elbe River 

→ Rhine River, and from there, O. crassus was able to reach the Baltic Sea and western Europe (bij de Vaate et 

al. 2002). 

 Obesogammarus crassus has very extensively spread in many areas. 
837

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

5

 Obesogammarus crassus has very extensively spread in wide ranges of areas.

 Obesogammarus crassus is known to spread from Lithuania in the Neman River to Curonian lagoon to Vistula 

lagoon to Oder Lagoon to Elbe River and now to Baltic Sea within ~50 years (bij de Vaate et al. 2002). 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 108

>100 High Adjustments

B. Critical species A*(1- 0%) 108

51-99 Moderate C. Natural enemy B*(1- 0%) 108

Control measures C*(1- 0%) 108

0-50 Low Potential for Establishment High

# of questions 

answered as Confidence 
838

“unable to 

determine”

Level

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: Low 

Obesogammarus crassus has the potential for high environmental impact if introduced to the Great 

Lakes.

The presence of Obesogammarus crassus, Pontogammarus robustoides, and Dreissena polymorpha in the 

Curonian Lagoon resulted in a severe reduction in the relative abundance of the former community and 

even population extinction within the ecosystem (Zaiko et al. 2011). However, the species identity of the 

populations that faced extinction is unknown. Whether the introduction of Obesogammarus crassus alone 

caused the reduction in the relative abundance of the former community is not specified. Where it is 

introduced, there is a significant reduction in native species, especially in the Curonian Lagoon (Zaiko et 

al. 2011). The relative abundance of the species that dominated the former community was significantly 

reduced. The populations of certain species faced extinction within this particular community. In the 

lower and upper reaches of the Pripyat River, Obesogammarus crassus comprises 80% of the total 

species abundance (Semenchenko and Vezhnovetz 2008). 

There is little or no evidence to support that Obesogammarus crassus has the potential for 

significant socio-economic impacts if introduced in the Great Lakes. 

Establishment of Obesogammarus crassus has not been known to cause a hazard or threat to human 

health, damage to infrastructure, or negative impacts on water quality. It has not been documented that 

this species is detrimental to markets or economic sectors, recreational activities or associated tourism, or 

the perceived aesthetic or natural value of the areas it inhabits. 

There is little or no evidence to support that Obesogammarus crassus has the potential for 

significant beneficial effects if introduced in the Great Lakes.

It is stocked in some areas, but there are no reports concluding that it is commercially valuable.

POTENTIAL ENVIRONMENTAL IMPACT
839

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 Obesogammarus crassus does not carry any microparasites (Ovcharenko et al. 2010).

 Obesogammarus crassus is not known to be poisonous. 

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 In the Curonian lagoon, O. crassus have caused a severe reduction of the relative abundance of the former 

community dominant species or even population extinction within the ecosystem (Zaiko et al. 2010). 

 In the middle and lower parts of Pripyat river, the abundance of O. crassus is more higher and equal 80% from 

total abundance of other amphipods (Semenchenko and Vezhnovetz 2008).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 In the Curonian lagoon, O. crassus have caused a severe reduction of the relative abundance of the former 

community dominant species or even population extinction within the ecosystem” (Zaiko et al. 2010). However, 

it is unknown whether this is caused by predation.
840

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus affecting any native populations genetically. 

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus negatively affecting water quality. 

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 O. crassus is not known to alter physical components of the ecosystem in some way. 

Environmental Impact Total 6

Total Unknowns (U) 1
841

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of a 

particular impact. An “Unknown” response is appropriate if the potential for a particular impact might be 

inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus posing hazard or threat to human health. 

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus causing damage to infrastructure. 

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus negatively affecting water quality. 
842

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus negatively affecting any markets or economic sectors. 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There have been no reports of O. crassus inhibiting recreational activities and/or associated tourism.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 Obesogammarus crassus has not been known to diminish the perceived aesthetic or natural value of the areas it 

inhabits.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
843

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of a 

particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Obesogammarus crassus is not known to act as a biological control agent for aquatic weeds or other harmful 

nonindigenous organisms.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

1
844

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

Not significantly 0 √

Unknown U

 Obesogammarus crassus is not known to have any medicinal or research value. 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 Obesogammarus crassus is not known to remove toxins or pollutants from the water of otherwise increase water 

quality. 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 O. crassus is not known to have any positive ecological impact outside of biological control. 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
845

Scientific Name: Obesogammarus obesus 

G.O. Sars, 1894

Common Name: Scud

Synonyms: Pontogammarus obesus, Gammarus obesus

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Obesogammarus obesus has a low probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping

From its native range, Obesogammarus obesus was introduced to Germany through ballast water and 

sediment, and to Austria via floating structures, ballast water, and sediments (NOBANIS 2014, DAISIE

2008b). Cooling water systems of ships may also be a vector for introduction of Obesogammarus obesus

(Tittizer and Banning 2000). Currently, Obesogammarus obesus does not occur near waters connected to 

the Great Lakes basin. Obesogammarus obesus occurs within a major shipping route in Europe (Locke et 

al. 1993, Mills et al. 1993). It does not currently occur in a port that is in direct trade with the Great 

Lakes, it is spreading in that direction (Nehring 2006). Obesogammarus obesus is capable of surviving 

oceanic transport (Ricciardi and Rasmussen 1998). Obesogammarus obesus can tolerate salinities 

between 0.1 – 20 ppm (Berezina 2007, bij de Vaate et al. 2002). It does not produce resistant resting egg 

stages; ballast water exchange and flushing may limit egg transport and survival (Grigorovich et al. 

2003).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100
846

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Obesogammarus obesus is a Ponto-Caspian amphipod that has spread through the Danube River to the Rhine 

River (Nehring 2006).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √
847

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U
848

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Obesogammarus obesus is a euryhaline species (bij de Vaate et al. 2002).

 The survival of amphipods during transportation in ballast tanks (water or sediments) is possible in most cases 

because of the high tolerance of this group of animals to different abiotic factors, mainly salinity, surviving 0.1-

20 ppm (Berezina 2007).

 Obesogammarus obesus is not likely to survive ballast water exchange (no resistant adult or resting stages) 

(Grigorovich et al. 2003).

 Obesogammarus obesus can survive oceanic transport (Ricciardi 1998).

 Obesogammarus obesus has been introduced via ballast water and sediments to Germany (NOBANIS 2014); 

Austria via floating structures, ballast water and/or sediments in tanks (DAISIE 2008b).

 Other vector includes cooling water systems of ships (Tittizer and Banning 2000).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1
849

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species is present within a major shipping route in Europe (Locke et al. 1993, Mills et al. 1993), and while 

not yet in a port, such as the lower Rhine River and Baltic Sea, with direct trade between Great Lakes and 

Ponto-Caspian, it continues to spread in that direction (Nehring 2006).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 10 Low

Total Unknowns (U) 0 Confidence Level High
850

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Obesogammarus obesus has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: high).

The native and introduced ranges of Obesogammarus obesus have similar climate and abiotic conditions 

to that of the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species 

occurs in Belarus, which is located in similar latitudes as the Great Lakes basin (Semenchenko and 

Vezhnovetz 2008). The level of light penetration in the Black Sea is similar to that of the Great Lakes 

basin (Ojaveer et al. 2002). The primary productivity of the Black Sea (150 - 200 g C m-2yr-1) is similar 

to that of the Great Lakes (100 – 310 g C m-2yr-1). This species can tolerate and adapt to a variety of 

environmental conditions and habitats (Bacela and Konopacka 2005, Mordukhaĭ-Boltovskoĭ 1960, 

Mordukhaĭ-Boltovskoĭ and Chirkova 1971, Pjatakova and Tarasov 1996). It is able to avoid unsuitable 

conditions and migrate to locate more suitable habitats (Berezina 2007). It can tolerate salinities from 0.1 

– 20 ppm (bij de Vaate et al. 2002, Berezina 2007). It is likely that Obesogammarus obesus can 

overwinter in the Great Lakes; it occurs in waters that have low temperatures and ice cover (Reid and 

Orlova 2002). Climate change may facilitate the establishment of this species in the Great Lakes basin; it 

occurs in areas that are warmer than the Great Lakes and is capable of surviving in higher salinities. 

Obesogammarus obesus is a dietary generalist (bij de Vaate et al. 2002, Elexová and Némethová 2003); it 

is likely that the Great Lakes contain an abundant food source for this species. This species is a significant 

portion of the diet of round gobies, which are nonindigenous fish established in the Great Lakes basin; 

however, predation by these fish has not prevented the establishment of other amphipods to the Great 

Lakes such as Echinogammarus ischnus and Gammarus tigrinis, nor the establishment of 

Obesogammarus obesus where it has been introduced beyond its native range (Borza et al. 2009). The 

short generation time of Obesogammarus obesus may facilitate its establishment (bij de Vaate et al. 

2002). Dreissenid mussels, which are already established in the Great Lakes, may aid the establishment of 

Obesogammarus obesus; evidence suggests there is a positive relationship between the density of 

Obesogammarus obesus and the biomass of dreissenid mussels (Alexander Protasov pers comm). A 

closely related scud species, Echinogammarus ischnus, has a greater dominance over native Gammarus 

fasciatus in dreissenid beds (Dermott et al. 1998). 

In the upper reaches of impoundments of the Danube River, Germany, Obesogammarus obesus attained 

densities up to 3,300 individuals/m2, which was associated with a displacement of several other amphipod 

species such as Dikerogammarus species. Obesogammarus obesus reaches high densities that are greater 

than or similar to the densities of the serious invaders or dominant species in the community (Žganec et 

al. 2009). This species is capable of migrating and dispersing with an average rate of 130km/year (Leuven 

et al. 2009). Obesogammarus obesus has immigrated over 4,000 km from their native area to the middle 

part of the Volga River (Lyakhov 1961, Mordukhaĭ-Boltovskoĭ 1960).
851

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 It would be described as euryocious, euryhaline (bij de Vaate et al. 2002).

 Obesogammarus obesus can adapt to new habitats, morphological and physiological adaptation (Dedyu 1967, 

Mordukhaĭ-Boltovskoĭ 1960, Mordukhaĭ-Boltovskoĭ and Chirkova 1971).

 Obesogammarus obesus can migrate to find suitable conditions (Berezina 2007).

 Obesogammarus obesus is most characteristic for the potamon (lower part of a river in which the water is 

typically slow-moving, still-surfaced, deep, and relatively warm, favouring limnophilous, stenothermous 

organisms that are thrifty in their use of dissolved oxygen) (Nesemann et al. 1996).

 Obesogammarus obesus may be able to adapt to different environmental conditions (Pjatakova and Tarasov 

1996).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Obesogammarus obesus occurs in Belarus, which is located at 52-56°N (Great Lakes at 41-49°N) 

(Semenchenko and Vezhnovetz 2008).

 Obesogammarus obesus can adapt to and/or avoid unsuitable conditions (Dedyu 1967, MordukhaĭBoltovskoĭ 1960,, Mordukhaĭ-Boltovskoĭ and Chirkova 1971).

 Water surface temperatures in Black sea reach -0.5°C in winter, to 23-26°C in summer (Encyclopedia 

Brittanica 2015).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 

2002). O. obesus most likely endures similar overwintering conditions in its native range. 
852

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Obesogammarus obesus have nonspecific food preference (bij de Vaate et al. 2002).

 Obesogammarus obesus are generalist: 20% Shredder, 10% Scraper, 20% Collector of fine organic 

material, 30% Predator) (Elexová and Némethová 2003).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Obesogammarus obesus can attain densities of up to 3,300 individuals/m2 in the upper reaches of 

impoundments of the navigable section of the Danube River in German which are characterized by 

widespread silt deposits (Tittizer et al. 2000). These high abundances of O. obesus were associated with a 

displacement of several other amphipod species (i.e., Dikerogammarus spp.) (Tittizer et al. 2000).

 While no studies in the Great Lakes, it has been found to be more numerous than many serious invaders 

like Dikerogammarus villosus (Žganec et al. 2009) or with abundances just below species abundant in the 

Great Lakes (e.g., E. ishnus) (Pockl 1994 pers comm. in Holdich and Pöckl 2007).

 Obesogammarus obesus was found to be highly abundant in several areas (40-100%) (Elexová and 

Némethová 2003, Bódis et al. 2012).

 Obesogammarus obesus dominates periphyton in shallow depths (Protasov and Silaeva 2010).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9
853

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 This species broods its young and protects its juveniles (bij de Vaate et al. 2002).

 Obesogammarus obesus has a relatively short generation time (bij de Vaate et al. 2002).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and the Black Sea (where present) are very similar: latitude 41-49°N and 41-46°N, 

respectively. While the climate around the Black Sea varies, it is generally continental (pronounced 

seasonal variations). Northwestern Black Sea seas have ice formation. Mean temperature over central 

portion of the sea is 8°C, over western portion 2-3°C in January; spring about 16°C, summer about 24°C. 

Extremes of -30°C to 37°C (Encyclopedia Britanica 2015).
854

 While precipitation varies by region/city, many are very similar to a Great Lakes city (e.g., Istanbul and 

Detroit at 850mm).

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 Primary production for Black Sea ranges from 150-200 C m-2 yr-1, and the Great Lakes range from 100-

310g C m-2 yr-1 (Ojaveer et al. 2002). O. obesus found in many freshwater habitats, as in the Great Lakes 

region. 

 Obesogammarus obesus is most characteristic of the potamon (which prefers slow-moving, still-sufaced 

deep waters); found in lower and middle reaches of rivers as well as Black Sea and dam lakes (Nehring 

2006). 

 Abiotic factors and climatic conditions of the native and introduced ranges of O. obesus are quite similar 

to the Great Lakes, making the region compatible (Reid and Orlova 2002, Grigorovich et al. 2003).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Sunlight (water transparency in meters) similar between Lake Erie and Black Sea (>8m) is suitable (Ojaveer et 

al. 2002).

 Obesogammarus obesus migrates between deep and shallow waters to find ideal conditions (Berezina 2007).

 Obesogammarus obesus is found in gravel, gravel-sand, sand/mud ( Borza et al. 2009, Nesemann et al. 1996, 

Elexová and Némethová 2003, Nehring 2006).
855

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Obesogammarus obesus lives in areas warmer than the Great Lakes (southern Black Sea and inland 

Europe), many without any ice cover year-round. The can migrate to find better conditions, and do well in 

high salinities (potentially outcompete natives).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Obesogammarus obesus have nonspecific food preference (bij de Vaate et al. 2002).

 Obesogammarus obesus are generalist: 20% Shredder, 10% Scraper, 20% Collector of fine organic material, 

30% Predator) (Elexová and Némethová 2003).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

9
856

assessed;

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No, there is no critical species required 

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

7

 A positive relationship between number of O. obesus (ind/m2) and dreissenid biomass (g/m2) has been found 

(R2=0.347) (Alexander Protasov pers comm.).

 Also seen in related species present in the Great Lakes: the Great Lakes invader (and a similar species found in 

similar areas) E. ischnus may have benefited from a co-evolved relationship with dreissenid mussels (e.g., 

greater dominance over native G. fasciatus in dreissenid beds) (Ricciardi and MacIsaac 2000).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
857

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Obesogammarus obesus is a significant portion of round and bighead goby diet (Borza et al. 2009), 

however, similar predation has not prevented establishment of other amphipods into the Great Lakes (e.g., 

E. ischnus and G. tigrinis) nor introduction and dominance of O. obesus in other invaded ranges.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

 Ballast Water Exchange would eliminate most individuals of this species from ballast tanks, but given the 

frequency of travel of ships between Great Lakes and Europe, inoculation could be frequent.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3
858

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

8

 Obesogammarus obesus reached the middle part of the Volga River spreading upstream more than 4,000 

km from their native area (Dedyu 1980, Lyakhov 1961, Mordukhaĭ-Boltovskoĭ 1960).

 Obesogammarus obesus has a wide distribution in Caspian, Azov, Black Seas. Originally low in Danube, 

now as high as Budapest (middle Danube) (Nesemann et al. 1996).

 Obesogammarus obesus was also found in Ukraine, Austria, Germany, Russia.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 Obesogammarus obesus has disperal rates: 130 km/yr (mean); 424km/yr (max) (Leuven et al. 2009).

 In particular, the amphipod O. obesus extended its distribution area 500 km upstream in the river during a 

short period from 1958 to 1972 (Shakhmatova and Antonov 1988). 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are none; only control meausres to prevent this species introduction.
859

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 114

>100 High Adjustments

B. Critical species A*(1- 0%) 114

51-99 Moderate C. Natural enemy B*(1-10%) 102.6

Control measures C*(1- 0%) 102.6

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: Low

Obesogammarus obesus has the potential for high environmental impact if introduced to the Great 

Lakes. 

Obesogammarus obesus is an intermediate host of the tapeworm Amphilina foliacea (Dubinina 1974). 

Amphilina foliacea affects Acipenserideae species at 20-93% infection rates and reduces reproductive 

success (Bauer et al. 2002). Acipenserideae fish get infected this tapeworm when it feeds on amphipods 

that carry it. Amphilina foliacea can potentially pose a hazard to lake sturgeon (Acipenser fulvescens), a 

near-threatened species of concern in the Great Lakes. Another host of Amphilina foliacea, Gammarus 

fasciatus currently occurs in the Great Lakes (Kipp 2014). Amphilina foliacea has not been reported in the 

Great Lakes but occurs in western North America (Choudhury and Dick 2001), so the threat of Amphilina 

foliacea due to the introduction of Obesogammarus obesus may be novel, but it is likely that its effects 

would be local. There is evidence that it may outcompete other species; the high density of 

Obesogammarus obesus (3,300 individuals/m2) in the Danube River in Germany was associated with the 

displacement of several other amphipod species (Tittizer et al. 2000). By reaching high densities and 

preying on zoobenthos, Obesogammarus obesus has the potential to negatively impact zoobentos 

populations (Elexová and Némethová 2003). As a prey of non-native round goby (Neogobius 
860

melanostomus), the presence of Obesogammarus obesus may result in an increase in population size of 

these invasive fish (Borza et al. 2009).

There is little or no evidence to support that Obesogammarus obesus has the potential for significant 

socio-economic impact if introduced to the Great Lakes.

It has not been reported that Obesogammarus obesus poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, or the aesthetic 

appeal of the areas it inhabit. It has the potential to impact recreation by reducing the abundance of lake 

sturgeon; however, it is unknown if it has significant impacts.

There is little or no evidence to support that Obesogammarus obesus has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Obesogammarus obesus can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 √

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U

 Obesogammarus obesus is an intermediate host of the tapeworm Amphilina foliacea, which can infect sturgeon 

species in Acipenserideae at 20-93% infection rates and can affect reproductive success. The Lake 

Sturgeon (Acipenser fulvescens) in the Great Lakes is a near-threatened species of concern, and any disruption 

to reproduction could impact this species (Dubinina 1974).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U
861

 Obesogammarus obesus can attain densities of up to 3,300 individuals/m2 in the upper reaches of 

impoundments of the navigable section of the Danube River in German which are characterized by widespread 

silt deposits (Tittizer et al. 2000). These high abundances of O. obesus were associated with a displacement of 

several other amphipod species (i.e., Dikerogammarus spp.) (Tittizer et al. 2000).

 While no studies in the Great Lakes, has been found to be more numerous than many serious invaders like 

Dikerogammarus villosus (Žganec et al. 2009) or with abundances just below species abundant in the Great 

Lakes (e.g., E. ishnus) (Pockl 1994 pers comm. in Holdich and Pöckl 2007).

 Obesogammarus obesus is found to be highly abundant in several areas (40-100%) (Bódis et al. 2012, Elexová 

and Némethová 2003).

 Obesogammarus obesus dominates periphyton in shallow depths (Protasov and Silaeva 2010).

 Obesogammarus obesus is more common than D. villosus and P. robustoides in the damlake (PopescuMarinescu et al. 2001).

 Obesogammarus obesus is the largest size class distribution (>50% of Danube and its main tributaries); 

dominant in communities (Borza et al. 2009).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 With 30% of its diet as a predator, the significant densities of O. obesus have potential to have predation 

effects. This may contribute to displacement of other zoobenthos (Elexová and Némethová 2003).

 Obesogammarus obesus is a significant portion of round and bighead goby diet (Borza et al. 2009).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √
862

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0

Unknown U √

Environmental Impact Total 8

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT
863

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0
864

Unknown U √

 Obesogammarus obesus could impact recreation through decline of lake sturgeon.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U
865

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 
866

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
867

Scientific Name: Pontogammarus robustoides

G.O. Sars, 1894

Common Name: Scud

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Pontogammarus robustoides has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Pontogammarus robustoides has expanded its range from the Ponto-Caspian basin and is now present in 

coastal waters of the Baltic Sea, as well as connecting river basins (bij de Vaate et al. 2002). Within the 

Baltic, this species has dispersed via both by ballast water transport and hull fouling (Arbačiauskas and 

Gumuliauskaite 2007, Grabowski et al. 2003, Grabowski and Bacela 2005, Jażdżewski et al. 2002,

Reinhold and Tittizer 1997, Reinhold and Tittizer 1999). As a high volume of Great Lakes shipping 

traffic originates from this region, ballast is a likely mechanism of further species spread (Grigorovich et 

al. 2003).

It has been proposed that based on its natural occurrence in brackish waters, P. robustoides may be able 

survive partial to complete ballast water exchange (Grigorovich et al. 2003). As a result, this species has 

been assessed by some researchers as having a high Great Lakes invasion risk from both BOB and 

NOBOB vessels (Grigorovich et al. 2003). However, under current mandatory ballast water regulations 

(saltwater flushing of at least 30 ppt), the number of individuals entering the Great Lakes is likely to be 

reduced due to physiological salinity constraints. Nevertheless, Santagata et al. (2008) reported partial 

survival of P. robustoides individuals exposed for 48 hours to full strength seawater (34 PSU).

POTENTIAL INTRODUCTION VIA DISPERSAL
868

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Pontogammarus robustoides is a Ponto-Caspian species that has invaded much of Europe (bij de Vaate et al. 

2002).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
869

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
870

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Within the Baltic, this species has dispersed via both ballast water transport and hull fouling (Arbačiauskas and 

Gumuliauskaite 2007, Grabowski et al. 2003, Grabowski and Bacela 2005, Jażdżewski et al. 2002, Reinhold 

and Tittizer 1997, Reinhold and Tittizer 1999). As a high volume of Great Lakes shipping traffic originates from 

this region, ballast is a likely mechanism of further species spread (Grigorovich et al. 2003).

 It has been proposed that based on its natural occurrence in brackish waters, P. robustoides may be able 

survive partial to complete ballast water exchange (Grigorovich et al. 2003). As a result, this species has been 

assessed by some researchers as having a high Great Lakes invasion risk from both BOB and NOBOB vessels 

(Grigorovich et al. 2003).
871

 However, under current mandatory ballast water regulations (saltwater flushing of at least 30 ppt), the number 

of individuals entering the Great Lakes is likely to be reduced due to physiological salinity constraints. 

Nevertheless, Santagata et al. (2008) reported partial survival of P. robustoides individuals exposed for 48 

hours to full strength seawater (34 ppt).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Pontogammarus robustoides has expanded its range from the Ponto-Caspian basin and is now present in 

coastal waters of the Baltic Sea, as well as connecting river basins (bij de Vaate et al. 2002).

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
872

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Pontogammarus robustoides has a high probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

Pontogammarus robustoides is a non-specific feeder (bij de Vaate et al. 2002), consuming detritus, 

sediments, unicellular green algae, and filamentous green algae, as well as oligochaetes and chironomids 

(Berezina et al. 2005). It has an invasion history of outcompeting a variety of other macroinvertebrate 

species in Europe, including the North American native amphipod Gammarus lacustris (see Impacts). 

When abundant, P. robustoides significantly contributes to the diets of various fish species (Arbačiauskas

and Gumuliauskaite 2007, Bubinas 1979), but the extent to which this predation will have an effect on 

potential populations in the Great Lakes is unknown.

The climatic conditions of the native (Ponto-Caspian) and introduced (Baltic) ranges of P. robustoides are 

very similar to those of the Great Lakes. Pontogammarus robustoides overwinters in its native range 

(Ponto-Caspian) and introduced areas (Baltic Sea and major river basins) (Bacela and Konopacka 2005). 

This species is able to survive in moderately wide temperature and salinity ranges encompassing 

conditions occurring in the Great Lakes. Its preferred ionic concentrations may limit the distribution of P. 

robustoides to the four lower Lakes (Michigan, Huron, Erie, Ontario), as spring chloride concentrations in 

Lake Superior are regularly very low (< 2 mg/L) (USEPA 2012).

Increased salinization is likely to be beneficial to the establishment of P. robustoides, as this species 

occurs naturally in brackish water (Dobrzycka-Krahel and Surowiec 2011, Romanova 1959). This species 

is likely to benefit from shorter ice cover duration. 

Arbačiauskas (2002) hypothesized that oxygen concentration is the principal limiting factor in 

determining the survival and sustainability of populations of Ponto-Caspian amphipods, but P. 

robustoides has greater tolerance to low oxygen these other amphipod invaders in the Baltic Sea (Dedyu 

1980). As oxygen content in higher latitude eutrophic waters that are ice covered for a substantial portion 

of the year is often reduced (Arbačiauskas 2002 and 2005), P. robustoides tends to occur in eutrophic 

waters only when ice cover is infrequent (Grabowski 2011); ice covered eutrophic waters may kill off 
873

established populations (Arbačiauskas and Gumuliauskaite 2007). Anoxic conditions, as present in the 

central basin of Lake Erie (USEPA 2012), may prevent P. robustoides from establishing in some regions 

of the Great Lakes.

Disturbance factors such as eutrophication, macroalgal blooms, and oxygen deficiency may facilitate the 

success of this species when introduced to a new environment, as competition for resources with 

established species becomes reduced (Berezina 2007).This species prefers to inhabit lenthic as opposed to 

lotic environments due to its inability to disperse against flow (Bacela and Konopacka 2005, Berezina and 

Panov 2003, Grabowski and Grudule et al. 2007, Jażdżewski et al. 2002, Zettler 2002), making the 

majority of the Great Lakes basin suitable habitat for establishment with respect to water movement. A 

high diversity of available habitats in a colonized area may facilitate survival and establishment of 

populations of P. robustoides by reducing niche overlap between various size classes (Czarnecka et al. 

2010).

Pontogammarus robustoides is a highly fecund species among Ponto-Caspian invaders in Europe and one 

of Poland’s most fecund amphipods, producing more eggs than other species of similar size, (Bacela and 

Konopacka 2005, bij de Vaate et al. 2002). This species undergoes rapid maturity, producing three 

generations per year with short (4-5 week) generation times (Bacela and Konopacka 2005). The autumn 

generation typically overwinters, but in thermally polluted waters (e.g., hydroelectric cooling water 

discharge), this species may reproduce year round (Kiticyna 1980); therefore, warming waters as a result 

of climate change could be beneficial to its invasion success. 

The invasion pattern of P. robustoides across Europe was very similar in magnitude and rate to another 

European mass invader, Dikerogammarus villosus, both of which have spread across the entire European 

continent in roughly 50 years (bij de Vaate et al. 2002). The spread of P. robustoides follows “jump” 

dispersal patterns, suggesting the involvement of anthropogenic factors in its expansion (Arbačiauskas

and Gumuliauskaite 2007). Once introduced, it has quickly become established throughout many major 

European water bodies, reaching densities of up to 2700 individuals/m2in some locations (Arbačiauskas 

and Gumuliauskaite 2007, Berezina et al. 2005).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Pontogammarus robustoides is able to survive in a relatively wide range of temperature (able to coexist with 

other invasive European amphipods tolerating water temperatures of ~5-30°C), and salinity, occurring 

naturally in salinities of 13 PSU (Romanova 1959) and showing partial survival (~50%) when exposed to 34 

PSU for 48 hours (Santagata et al. 2008).
874

 It is able to survive at oxygen concentrations as low as 0.209 mg/L, the lowest reported for any of the invasive 

European amphipods (Dedyu 1980).

 Viable populations are able to exist with sodium concentrations as low as 3.4 mg/L (Arbačiauskas and 

Gumuliauskaite 2007) and to reproduce at potassium concentrations as low as 10-15 mg/L (Berezina and 

Panov 2003). Disturbance factors such as eutrophication, macroalgal blooms and oxygen deficiency may 

facilitate the success of this species when introduced to a new environment, as competition for resources with 

established species becomes reduced (Berezina 2007).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Pontogammarus robustoides overwinters in its native range (Ponto-Caspian) and introduced areas (Baltic Sea 

and major river basins), undergoing a breeding peak in early October to produce individuals that will survive 

to breed early the following April (Bacela and Konopacka 2005).This species is able to survive at oxygen 

concentrations as low as 0.209 mg/L (Dedyu 1980). When water temperatures drop below 5°C, this species 

migrates to deeper waters habitats (Berezina et al. 2005)

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 This species shows a non-specific food preference (bij de Vaate et al. 2002) and diet flexibility, able to feed on 

detritus, sediments, unicellular green algae, and filamentous green algae, as well as oligochaetes and 

chironomids (Berezina et al. 2005).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 6
875

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 This species has a history of outcompeting a variety of other macroinvertebrate species throughout its invaded 

European territory, including the North American native amphipod Gammarus lacustris (see Impact section).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

9

 Bij de Vaate et al. (2002) classify P. robustoides as a species with high fecundity among the successful PontoCaspian invaders across Europe.

 Bacela and Konopacka (2005) have observed this species to be one of Poland’s most fecund amphipods, with 

females laying more eggs than individuals of other species with similar body size. 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 This species undergoes rapid maturity, producing three generations per year with short (4-5 week) generation 

times (Bacela and Konopacka 2005).
876

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species is a Ponto-Caspian native, a region where climatic conditions are very similar to those of the 

Great Lakes.

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 The water temperature (~6-30°C) and salinity range (0-13 ppt) tolerated by P. robustoides within its native 

range are well within the ranges occurring in the Great Lakes.

 This species prefers to inhabit lentic as opposed to lotic environments due to its inability to disperse against 

flow (Bacela and Konopacka 2005, Berezina and Panov 2003, Grabowski and Grudule et al. 2007, Jażdżewski

et al. 2002, Zettler 2002), making the majority of the Great Lakes basin suitable habitat for establishment with 

respect to water movement.

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
877

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 A high diversity of habitats available in a colonized area may facilitate survival and establishment of 

populations of P. robustoides by reducing niche overlap between various size classes (Czarnecka et al. 2010).

 Pontogammarus robustoides is known to exist in waters with ionic concentrations as low at 185 mg/L total, with 

3.4 mg Na+/L and therefore ~5.0 mg Cl-/L (Arbačiauskas and Gumuliauskaite 2007). Such preferred ionic 

concentrations may limit this species distribution to the four lower Lakes (Michigan, Huron, Erie, Ontario), as 

spring chloride concentrations in Lake Superior are regularly below 2 mg/L (USEPA 2012).

 It is hypothesized that O2 concentrations are the principal limiting factor in determining the survival and 

sustainability of populations of Ponto-Caspian amphipods (Arbačiauskas 2002). Anoxic conditions present in 

the central basin of Lake Erie (USEPA 2012) may prevent P. robustoides from establishing there, as eutrophic 

conditions under ice cover may destroy an established populations (Arbačiauskas and Gumuliauskaite 2007). 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 This species is likely to benefit from shorter ice cover duration, as oxygen content in higher latitude eutrophic 

waters that are ice covered for a substantial portion of the year is often reduced (Arbačiauskas 2002, 

Arbačiauskas 2005). Therefore, this species tends to occur only in eutrophic waters where ice cover is 

infrequent (Grabowski 2011).

 Increased salinization (Rahel and Olden 2008) is also likely to be beneficial to the establishment of P. 

robustoides in the Great Lakes, as this species occurs naturally in salinities up to 13 ppt (Romanova 1959) and 

is able to survive in waters with much higher salinity (Dobrzycka-Krahel and Surowiec 2011).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9
878

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 This species displays a non-specific food preference (bij de Vaate et al. 2002) and a flexible diet, able to feed on 

detritus, sediments, unicellular green algae, and filamentous green algae, as well as oligochaetes and 

chironomids (Berezina et al. 2005). None of these food sources are limiting in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by P. robustoides.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 6
879

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 When abundant, P. robustoides significantly contributes to the diets of various fish species (Arbačiauskas and 

Gumuliauskaite 2007, Bubinas 1979), though the extent to which this predation will have an effect on potential 

populations in the Great Lakes is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U
880

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 The invasion pattern of this species across Europe was very similar in magnitude and rate to another European 

mass invader, Dikerogammarus villosus, both of which have spread across the entire European continent in 

roughly 50 years (bij de Vaate et al. 2002).

 It has quickly become established throughout many major European water bodies, reaching densities of 2700 

individuals/m2in some locations (Arbačiauskas and Gumuliauskaite 2007, Berezina et al. 2005).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

8

 Within the Baltic, this species is known to have dispersed via both ballast water transport and hull fouling 

(Arbačiauskas and Gumuliauskaite 2007, Grabowski et al. 2003, Grabowski and Bacela 2005, Jażdżewski et al. 

2002, Reinhold and Tittizer 1997, Reinhold and Tittizer 1999).

 Hull fouling is likely the most important dispersal mechanism over short distances by slow moving vessels 

(Arbačiauskas and Gumuliauskaite 2007). The spread of P. robustoides follows jump dispersal patterns, 

suggesting the involvement of anthropogenic factors in its expansion (Arbačiauskas and Gumuliauskaite 2007).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

-90% total 

points (at 
881

highly effective in preventing the establishment and spread of this species) end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 117

>100 High Adjustments

B. Critical species A*(1- 0%) 117

51-99 Moderate C. Natural enemy B*(1- 0%) 117

Control measures C*(1- 0%) 117

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate
882

Pontogammarus robustoides has the potential for moderate environmental impact if introduced to 

the Great Lakes.

In habitats across Europe where P. robustoides is well established and numerous, significant declines in 

species richness and diversity, as well as reductions in body length of other macroinvertebrates, have been 

observed (Arbačiauskas and Gumuliauskaite 2007). In Lithuanian water bodies with abundant populations 

of P. robustoides, competitive exclusion of the native amphipod Gammarus lacustris has been observed 

(Arbačiauskas 2002, Arbačiauskas 2005). Additionally, asymmetrical intraguild predation may be 

primarily responsible for the displacement of other Baltic Sea gammarid species (Arbačiauskas and 

Gumuliauskaite 2007), including a smaller invasive amphipod, Gmelinoides fasciatus in some habitats in 

the eastern Gulf of Finland (Berezina and Panov 2003), and indigenous Gammarus duebeni and 

Gammarus zaddachi in the Vistula Lagoon (Jażdżewski et al. 2004). Large numbers of P. robustoides

have reduced the densities of benthic detritivores in the stony littoral zone of Neva Bay in the Gulf of 

Finland (Berezina and Panov 2003). When abundant, this species may also negatively affect populations 

of the freshwater isopod Asellus aquaticus as a result of direct predation (Arbačiauskas 2005). However, 

in moderate abundances, the negative impacts exerted by P. robustoides on species diversity are less 

severe (Arbačiauskas and Gumuliauskaite 2007).

Pontogammarus robustoides may be a vector of non-native fish parasites (e.g., Trematoda, 

Acanthocephala) (Sulgostowska and Vojtkova 1992). Additionally, P. robustoides may affect the 

composition and abundance of littoral macrophytes through heavy grazing pressure, as seen with the 

Great Lakes nuisance algae Cladophora in the eastern Gulf of Finland (Berezina et al. 2005). Populations 

in this study were able to consume 4-5 g (dry weight) Cladophora per day.

There is little or no evidence to support that Pontogammarus robustoides has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

The reductions in size and diversity of macroinvertebrate communities associated with the introduction of 

P. robustoides (Arbačiauskas and Gumuliauskaite 2007) may diminish food availability for native fish 

species; however, these specific effects have not yet been documented. Additionally, this species is not 

known to be a vector of any human pathogens (Grabowski 2011).

Pontogammarus robustoides has the potential for moderate beneficial effects if introduced to the 

Great Lakes.

The initial and subsequent intentional introductions of this species into the Baltic Sea were intended to 

improve fishery production (Arbačiauskas and Gumuliauskaite 2007); when abundant, P. robustoides

makes significant contributions to fish diet (Bubinas 1979). However, its contribution to the diet of fish 

species has never been precisely quantified, except for an unconfirmed 20% increase in fishery 

production in a few reports (Arbačiauskas and Gumuliauskaite 2007). Further, this species is considered 

an important factor in macroalgal bloom control through food web interactions. When populations are 

dense, P. robustoides can have a dramatic grazing impact on Cladophora (a widespread nuisance 

macroalgae in the Great Lakes) biomass in the littoral zone (Berezina et al. 2005).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.
883

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Pontogammarus robustoides may be a vector of non-native fish parasites (e.g., Trematoda, Acanthocephala) 

(Sulgostowska and Vojtkova 1992).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Pontogammarus robustoides has a history of outcompeting other macroinvertebrate species throughout its 

invaded range in Europe. In habitats where P. robustoides is well established and numerous, significant 

declines in species richness and diversity, as well as reductions in body length of other macroinvertebrates, 

have been observed (Arbačiauskas and Gumuliauskaite 2007).

 In Lithuanian water bodies with abundant populations of P. robustoides, competitive exclusion of the native 

amphipod Gammarus lacustris has been observed (Arbačiauskas 2002, Arbačiauskas 2005).

 In the brackish Vistula Lagoon, a decline of indigenous Gammarus duebeni and Gammarus zaddachi was 

reported parallel to the appearance of P. robustoides as a result of intraguild predation (Jażdżewski et al. 

2004).

 Large numbers of P. robustoides have reduced the densities of benthic detritivores in the stony littoral zone of 

Neva Bay in the Gulf of Finland (Berezina and Panov 2003).

 In moderate abundances, the negative impacts exerted by P. robustoides on species diversity are less severe 

(Arbačiauskas and Gumuliauskaite 2007).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √
884

Not significantly 0

Unknown U

 Additionally, asymmetrical intraguild predation may be primarily responsible for the displacement of other 

Baltic Sea gammarid species when P. robustoides is introduced (Arbačiauskas and Gumuliauskaite 2007), 

including a smaller invasive amphipod, Gmelinoides fasciatus in some habitats in the eastern Gulf of Finland 

(Berezina and Panov 2003).

 When abundant, this species may negatively affect populations of the freshwater isopod Asellus aquaticus as a 

result of direct predation (Arbačiauskas 2005).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0

Unknown U

 Pontogammarus robustoides may affect the composition and abundance of littoral macrophytes through heavy 

grazing pressure, as seen with Great Lakes nuisance algae Cladophora in the eastern Gulf of Finland. 

Populations in this study were able to consume 4-5 g (dry weight) Cladophora per day (Berezina et al. 2005).
885

Environmental Impact Total 4

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 This species is not known to be a vector of any human pathogens (Grabowski 2011).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6
886

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0

Unknown U √

 The reductions in size and diversity of macroinvertebrate communities associated with the introduction of P. 

robustoides (Arbačiauskas and Gumuliauskaite 2007) may diminish food availability for native fish species; 

however, these specific effects have not yet been documented.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
887

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 √

Not significantly 0

Unknown U

 This species is considered an important factor in macroalgal bloom control through food web interactions 

(Berezina et al. 2005).

 When populations are dense, P. robustoides can have a dramatic grazing impact on Cladophora biomass (a 

nuisance macroalgae present in the Great Lakes) in the littoral zone (Berezina et al. 2005).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U

 The initial and subsequent intentional introductions of this species into the Baltic Sea were intended to improve 

fishery production (Arbačiauskas and Gumuliauskaite 2007); when abundant, P. robustoides = makes 

significant contributions to fish diet (Bubinas 1979). However, its contribution to the diet of fish species has 

never been precisely quantified, except for an unconfirmed 20% increase in fishery production in a few reports 

(Arbačiauskas and Gumuliauskaite 2007).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √
888

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
889

0 ≥2

Unknown

1 ≥1
890

A.5 Crustaceans - Cladocerans

Scientific Name: Cornigerius maeoticus maeoticus

Pengo, 1879

Common Name: Waterflea

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate 

Cornigerius maeoticus maeoticus has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Cornigerius maeoticus maeoticus is not known to hitchhike or foul, and is not stocked or commercially 

cultured in the Great Lakes basin. It does not currently occur near waters connected to the Great Lakes 

basin and has yet to be observed in the ballast water of ships entering the Great Lakes.

Cornigerius maeoticus maeoticus is present in the Baltic Sea, which has trade connections to the Great 

Lakes (Krylov et al. 1999, Panov et al. 2007, Rodionova 2005, Sopanen 2008); thus Cornigerius 

maeoticus maeoticus may be transported to the Great Lakes via shipping. This species produces resting 

eggs that may survive transport in ballast water (Sopanen 2008). Cornigerius maeoticus maeoticus can 

tolerate temperatures ranging from 11 to 23°C and salinities up to 24% (Aladin 1995, Panov et al. 2007). 

Cornigerius maeoticus maeoticus may be introduced to the Great Lakes via ships declaring “No Ballast 

on Board” (NOBOB) that are exempt from ballast water exchanage. A study showed that the majority of 

ships entering the Great Lakes are NOBOB vessels and 43% of these ships contain residual water with 

less than 10‰ salinity (Johengen et al. 2005). In that study, the temperature of the residual water from the 

vessels sampled ranged from -0.7 to 23.9°C; thus Cornigerius maeoticus maeoticus is likely to survive the 

salinity and temperature of the NOBOB ballast water.

POTENTIAL INTRODUCTION VIA DISPERSAL
891

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Cornigerius maeoticus maeoticus occurs naturally in the Ponto-Caspian basin. Its native and invaded range 

includes the Black Sea, the Sea of Azov, and the freshwater rivers of the basin (Mordukhaĭ-Boltovskoĭ and 

Rivier 1971, Panov et al. 2007).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Cornigerius maeoticus maeoticus is most likely to be introduced to the Great Lakes basin through ballast water. 

There is no indication in the literature of biofouling or hitchhiking (Panov et al. 2007, USEPA 2008). 

 Cornigerius maeoticus maeoticus produces resting eggs that could possibly foul ships, but it is unlikely (Panov 

et al. 2007, Sopanen 2008).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
892

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 The only commercial use for C. maeoticus maeoticus would be through scientific supply companies. A thorough 

search of companies (Fisher Scientific, Carolina Biological Supply, and various companies found through 

Google searches) concluded with no evidence of this species being used by scientific supply companies.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus occurs naturally in North America or that 

there would be any interest stocking (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5
893

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There is no record either in the literature or online of C. maeoticus maeoticus being commercially cultured or 

transported.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

0
894

ballast water regulations.

Unknown U

 Cornigerius maeoticus maeoticus has been shown to survive in a range of temperature from 11 to 23 ̊C, and can 

tolerate both fresh and brackish water, up to 13‰ (Panov et al. 2007).

 Cornigerius maeoticus maeoticus also produces resting eggs which could aid in its invasion (Sopanen 2008).

 Multiple papers have stated that ballast water is a likely vector for transport of C. maeoticus maeoticus (Krylov 

et al. 1999, Rodionova 2005).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Cornigerius maeoticus maeoticus is native to the Black, Azov, and Caspian seas and the lower reaches of the 

lower reaches of Danube, Dnieper, and Bug rivers (Panov et al. 2007).

 It has spread throughout the Ponto-Caspian region into areas where shipping is prevalent (e.g., Volga, Don, 

and Dnieper reservoirs), as well as into the eastern Baltic Sea; this shipping traffic provides an invasion 

corridor from the eastern Baltic Sea to the Great Lakes (Krylov et al. 1999, Panov et al. 2007, Rodionova 2005, 

Sopanen 2008).
895

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
896

Cornigerius maeoticus maeoticus has a moderate probability of establishment if introduced to the 

Great Lakes (Confidence level: High).

Cornigerius maeoticus maeoticus is native to the Ponto-Caspian basin, occurring in the Black Sea, the 

Sea of Azov, and the freshwater rivers of the basin (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 

2007). Where it has been already introduced, it is inoculated in small quantities and infrequently 

(Rodionova 2005). Historically, it has been established locally outside its native range and its spread was 

facilitated by human activities (Panov et al. 2007, Rodionova 2005). The native and introduced ranges of 

Cornigerius maeoticus maeoticus have similar climate and abiotic conditions to that of the Great Lakes 

(USEPA 2008, Reid and Orlova 2002, Grigorovich et al. 2003). This species prefers inhabiting the 

metalimnion in large lakes; thus it is likely to find a suitable habitat in the Great Lakes. It is unlikely that 

the adult forms of this species are capable of overwintering in the Great Lakes due to its temperature 

range of 11-23°C (Panov et al. 2007). Cornigerius maeoticus maeoticus produces resting stages that are 

likely to survive winters in the Great Lakes. Cornigerius maeoticus maeoticus may adapt well to climate 

change in the Great Lakes; increase in salinization and temperature may render the Great Lakes more 

suitable for this species (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007, Reid and Orlova 

2002). 

Cornigerius maeoticus maeoticus feeds on smaller planktonic organisms such as microcrustaceans that 

are abundant in the Great Lakes. This species will likely find a suitable food source if introduced to the 

Great Lakes (Panov et al. 2007). Cornigerius maeoticus maeoticus is preyed on by planktivorous fish and 

larger predatory zooplankton. If this species is introduced to the Great Lakes, its establishment may be 

limited by predation. 

Several studies predict that Cornigerius maeoticus maeoticus will establish in the Great Lakes due to its 

ability to produce resting eggs (Panov et al. 2007, Rodionova 2005, Sopanen 2008). It is capable of 

parthenogenesis (Mordukhaĭ-Boltovskoĭ 1967). This species has a higher fecundity that other similar 

species in the Baltic Sea (Panov et al. 2007); however, its fecundity may be more moderate in waters of 

lower salinity (Aladin 1995, Mordukhaĭ-Boltovskoĭ and Rivier 1971).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

5

 Cornigerius maeoticus maeoticus has been recorded to survive from 11 to 23 ̊C, a salinity range from 

freshwater to 1.7 ppt, and in a variety of nutrient levels (Panov et al. 2007).
897

 A study of salinity tolerance by Aladin (1995) found that under laboratory conditions C. maeoticus maeoticus

showed upper limits of 20 and 24 g L-1in Caspian and Aral Sea water respectively. Aladin (1995) also found 

individuals within the Caspian Sea in the range of 6.0 g L-1to 12.5 g L-1.

 Mordukhaĭ-Boltovskoĭ and Rivier (1971) noted that C. maeoticus maeoticus preferred 3-8% salinity levels in 

the north Caspian Sea, also tolerating fresh waters. 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Cornigerius maeoticus maeoticus could not survive these conditions during most life stages. However, it 

produces resting “winter” eggs that would survive the conditions specified (Panov et al. 2007).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

4

 Research on the particular diet of C. maeoticus maeoticus and its relatives is limited. However, it is known to 

prey upon small planktonic organisms, such as other microcrustaceans (Mordukhaĭ-Boltovskoĭ and Rivier 

1971, Panov et al. 2007).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6
898

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

4

 Research on the competitive ability of C. maeoticus maeoticus is limited; however, some closely related species 

that have successfully invaded the Great Lakes have been studied more thoroughly. Cercopagis pengoi has been 

shown to be controlled effectively by larger local planktivorous fish populations, but in some cases it has 

outcompeted the smaller planktivorous fishes (Panov et al. 2007).

 Cercopagis pengoi comes from the same order and section (Onychopoda) as C. maeoticus maeoticus but from a 

different family (Cristescu and Hebert 2005). Cercopagis pengoi has similar physiological tolerances and 

feeding behaviors, although it is more motile (Panov et al. 2007). In papers discussing the invasion history of 

cladocerans in the Ponto-Caspian region, C. maeoticus maeoticus and C. pengoi are cited as the most probable 

or most recent to invade, along with Evadne anonyx (Panov et al. 2007, Rodionova 2005, Sopanen 2008).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Panov et al. 2007 found that C. maeoticus maeoticus had higher fecundity than other similar species in the 

Baltic Sea, including C. pengoi that has successfully invaded the Great Lakes. Other papers have found the 

fecundity rates of C. maeoticus maeoticus to be more moderate in less saline regions (Aladin 1995, MordukhaĭBoltovskoĭ and Rivier 1971).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 0
899

establishment in new environments)

Unknown U

9

 Multiple papers have predicted that C. maeoticus maeoticus will successfully invade the Great Lakes due to its 

ability to produce resting eggs (Panov et al. 2007, Rodionova 2005, Sopanen 2008).

 Cercopagis pengoi has similar physiological tolerances and reproductive strategies as C. maeoticus maeoticus

and it invaded the Great Lakes 15 years ago (Panov et al. 2007).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions of the native and introduced ranges of C. maeoticus maeoticus are quite 

similar to the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
900

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Like most related species, C. maeoticus maeoticus prefers the metalimnion (middle water layer) in larger lakes, 

at around 10-20 m deep, during the peak season (Mordukhaĭ-Boltovskoĭ and Rivier 1971). This habitat is 

readily available in the Great Lakes, although it may already be in high demand.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Cornigerius maeoticus maeoticus would benefit from an increase in salinity and slightly warmer water 

temperatures in the Great Lakes (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007, Reid and Orlova 

2002).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0
901

Unknown U

9

 Cornigerius maeoticus maeoticus preys upon smaller planktonic organisms such as microcrustaceans (Panov et 

al. 2007). These plankton are extremely plentiful in the Great Lakes basin. An already established invasive 

predator, C. pengoi, demonstrates that similar predators will have an appropriate food source readily available 

(Bushnoe et al. 2003, Panov et al. 2007).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no indication in any literature that C. maeoticus maeoticus requires another species for a critical life 

stage. There is definitely room for more research to be done concerning the basic biology and ecology of the 

species, but of the research that has been done, there is no mention (Aladin 1995, Mordukhaĭ-Boltovskoĭ and 

Rivier 1971, Panov et al. 2007)

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

3
902

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 Cornigerius maeoticus maeoticus could possibly benefit from nonindigenous plankton being established as an 

extra food source (Aladin 1995, Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007). Although this is a 

possibility, there is no recorded example of this happening, and there is already an established food source 

available.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-30%

 Cornigerius maeoticus maeoticus, as well as its relatives, are naturally predated upon by planktivorous fish and 

other predatory zooplankton. While there is no record of C. maeoticus maeoticus being specifically controlled 

by any particular predator, this has sometimes been the case for its relative C. pengoi, a well established 

invasive species in the Great Lakes (Panov et al. 2007). Local indigenous and nonindigenous species have been 

shown to have varying levels of control on C. pengoi in its native and introduced ranges. 

 A Lake Ontario study found that C. pengoi is effectively consumed by Alewife, Alosa pseudoharengus, and 

Rainbow Smelt, Osmerus mordax. This study also found that even in areas with strong fish predation, C. pengoi

still could reach high abundances (Bushnoe et al. 2003, Panov et al. 2007).

 Various studies looking at the relationship between Bythotrephes longimanus and C. pengoi have been 

conducted ( Panov et al. 2007). Bythotrephes longimanus is a larger onychopod that also preys upon smaller 

plankton in both native and introduced ranges. Panov et al. (2007) note that B. longimanus seems to be the 

most effective predator of C. pengoi.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)
903

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

1

 In the cases where C. maeoticus maeoticus was introduced by transoceanic shipping, it was an infrequent 

inoculum that was very small (e.g., a few individuals) (Rodionova 2005).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

7

 Cornigerius maeoticus maeoticus has spread throughout the Ponto-Caspian region. This is greatly aided by 

human activity along one specific invasion corridor. There are multiple papers documenting the annual spread 

of this species and its relatives (Panov et al. 2007, Rodionova 2005).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 Over the past 40 years, C. maeoticus maeoticus has spread throughout the Ponto-Caspian region. This spread 

was greatly accelerated by human activities (Panov et al. 2007, Rodionova 2005). 
904

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 The major control measure in the Great Lakes would be ballast water management options such as ballast 

water exchange. While this could be an effective measure, relatives of C. maeoticus maeoticus have successfully 

invaded the Great Lakes after the implantation of these measures (Panov et al. 2007, Rodionova 2005). This 

however relates to the introduction of a species, not establishment.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 100

>100 High Adjustments

B. Critical species A*(1- 0%) 100

51-99 Moderate C. Natural enemy B*(1- 30%) 70

Control measures C*(1- 0%) 70

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS
905

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Cornigerius maeoticus 

maeoticus if introduced to the Great Lakes is inadequate to support proper assessment. 

There is insufficient information available to determine if Cornigerius maeoticus maeoticus poses a threat 

to other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Cornigerius maeoticus maeoticus has the potential for 

significant socio-economic impact if introduced to the Great Lakes.

It has not been reported that Cornigerius maeoticus maeoticus poses a threat to human health or water 

quality. There is no evidence that this species negatively impacts infrastructure, economic sectors, 

recreational activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Cornigerius maeoticus maeoticus has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Cornigerius maeoticus maeoticus can be used for the control of other 

organisms or improving water quality. There is no evidence to suggest that this species is commercially, 

recreationally, or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 There is little literature describing the biology of this species in particular. Some papers compare Cornigerius 

maeoticus maeoticus to its relatives, which do not pose any particular threat or hazard to native species 

(Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).
906

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0

Unknown U √

 Cornigerius maeoticus maeoticus is a predatory cladoceran that generally feeds on smaller planktonic 

crustaceans. There is no direct evidence that C. maeoticus maeoticus would out-compete native species for food 

sources, however closely related species such as Cercopagis pengoi have been shown to do so once introduced 

in the Great Lakes (Panov et al. 2007, Rodionova 2005).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

 There is no direct evidence of C. maeoticus maeoticus altering predator prey relationships. 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 1 
907

effects have been limited or inconsistent (as compared with above statement)

Not significantly 0 √

Unknown U

 There has been some work done on the basic biology and ecology of this species but in general it is lacking. 

There is however no indication that C. maeoticus maeoticus would have any effect on water quality 

(Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 There has been some work done on the basic biology and ecology of this species but in general it is lacking. 

There is however no indication that C. maeoticus maeoticus would have any effect on the physical components 

of the ecosystem (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

Environmental Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.
908

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would have any adverse effects on human 

health. It is not a known carrier of any disease or pathogen and there is no record suggesting it would magnify 

toxin levels (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would cause damage to any infrastructure. 

It is a planktonic crustacean that does not possess any means to damage infrastructure (Mordukhaĭ-Boltovskoĭ

and Rivier 1971, Panov et al. 2007).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would negatively affect water quality. It 

does prey upon other planktonic crustaceans that could possibly prey upon algae, but there is no record of a 

significant effect resulting from this predation (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would negatively affect any markets or 

economic sectors. It could pose competition for smaller planktivorous fish, but there has been no explicit record 

of this occurring (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007)

 A closely related species, C. pengoi, which has invaded the Great Lakes has demonstrated competition with 

smaller planktivorous fish (Panov et al. 2007).
909

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would inhibit any recreational activities. It 

could pose competition for smaller planktivorous fish, but there has been no explicit record of this occurring 

(Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007)

 A closely related species, C. pengoi, has been shown to be competitive with smaller planktivorous fish and to 

foul fishing lines (Panov et al. 2007).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would diminish any aesthetic or natural 

value (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT
910

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would act as a biological control for any 

nonindigenous organisms (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

 However, a closely related species, C. pengoi, has been shown to control and be controlled by other 

nonindigenous species in its native and introduced habitats (Panov et al. 2007).

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would be commercially valuable.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would be recreationally valuable.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √
911

Unknown U

 There is no indication in the literature that C. maeoticus maeoticus would be valuable for research. The only 

research that has been done on it has been related to its invasion and distribution (Mordukhaĭ-Boltovskoĭ and 

Rivier 1971, Panov et al. 2007, Rodionova 2005).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There is no indication in the literature that C. maeoticus maeoticus would remove toxins or pollutants or 

otherwise improve water quality. It is a predatory cladoceran that feeds upon smaller cladocerans and plankton 

that would not have any effect on water quality (Mordukhaĭ-Boltovskoĭ and Rivier 1971, Panov et al. 2007).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 There is no indication in the literature that C. maeoticus maeoticus would have a positive ecological impact. 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
912

Scientific Name: Daphnia cristata

G.O. Sars, 1862

Common Name: Waterflea

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: High

Daphnia cristata has a high probability of introduction to the Great Lakes (Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Daphnia cristata is predicted to have potential for introduction to the Great Lakes via ballasts of vessels 

as well as ships that declare “No Ballast on Board” (Grigorovich et al. 2003). In general, this species does 

not tolerate a wide range of adverse conditions, but it has been found in residual water from a ship that 

entered the Great Lakes basin (Duggan et al. 2005, Wonham et al. 2005). In addition, this species is 

capable of producing ephippia eggs that are resistant to harsh conditions (Benzie 2005). It has been 

reported that Daphnia cristata has a high risk of introduction to the Great Lakes (Grigorovich et al. 2003).

Daphnia cristata does not currently occur near waters connected to the Great Lakes basin. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Daphnia cristata is widely distributed in temperate regions in Europe and Asia but not recorded from North 

America (Benzie 2005).
913

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 The only recorded vector that could transport this species to the Great Lakes basin is within ballast water 

(Duggan et al. 2005).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 The only commercial use for Daphnia cristata would be through scientific supply companies. A thorough search 

of companies (Fisher Scientific, Carolina Biological Supply, and various companies found through Google 

searches) concluded with no evidence of this species being used by scientific supply companies.
914

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Daphnia cristata is widely distributed in temperate regions in Europe and Asia but not recorded from North 

America (Benzie 2005).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U
915

 The only commercial use for Daphnia cristata would be through scientific supply companies. A thorough search 

of companies (Fisher Scientific, Carolina Biological Supply, and various companies found through Google 

searches) concluded with no evidence of this species being used by scientific supply companies.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Daphnia cristata does not generally tolerate a wide range of adverse conditions, but a study has shown 

individuals surviving in ballast water transported to the Great Lakes basin (Duggan et al. 2005, Wonham et al. 

2005). 

 Ships declaring NOBOB have been shown to harbor water habitable to Daphnia cristata (Johengen et al. 2005).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 √

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great Score x 0.1
916

Lakes nor in ports in direct trade with the Great Lakes.

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Daphnia cristata does not generally tolerate a wide range of adverse conditions, but a study has shown 

individuals surviving in ballast water transported to the Great Lakes basin (Duggan et al. 2005, Wonham et al. 

2005).

 Daphnia cristata is widely distributed in temperate regions in Europe and Asia (Benzie 2005).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 1 80 High

Total Unknowns (U) 0 Confidence Level High
917

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Daphnia cristata has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Daphnia cristata is widely distributed in temperate regions in Europe and Asia (Benzie 2005). The native 

range of this species, the Ponto-Caspian basin, has a similar climate to the Great Lakes (USEPA 2008). 

The Great Lakes exhibit seasonality and similar stratification as its native range. Daphnia cristata may be 

capable of overwintering in the Great Lakes basin; it naturally occurs in waters that are 0-3°C and can 

tolerate waters with low oxygen levels (Rivier 2005). This species has the potential to tolerate pollution in 

the Great Lakes; in Finland, this species is present in eutrophic lakes (Horppila et al. 2000). It has been 

suggested that Daphnia cristata is released from ships that enter the Great Lakes in low number and 

frequency, so its potential for establishment may be somewhat limited (Duggan et al. 2005, Johengen et 

al. 2005).

Daphnia cristata is likely to find a food source in the Great Lakes. It feeds on phytoplankton (Benzie 

2005). Daphnia cristata may be resistant to predation by fish and benefits from high predation pressure 

(Hessen et al. 1995). It can avoid predation by planktivorous fish by avoiding predators in space and 

changing its morphology in times of high predation pressure (Pijanowska 1992). This species benefits 

from the presence of planktivorous fish that eat other cladocerans (Amundsen et al. 2009, Nyberg 1998). 

Daphnia cristata is among the most abundant cladoceran in Lake Hiidenvesi, Finland, making up 38-88% 

of the cladoceran biomass (Alajärvi and Horppila 2004, Tallberg et al. 1999). Evidence suggests that a 

predatory cladoceran Leptodora kindti feeds on Daphnia cristata and regulates their population in Lake 

Hiidenvesi (Uusitalo et al. 2003). Leptodora kindti is also found in the Laurentian Great lakes (Barbiero et 

al. 2001); thus, Leptodora kindti may limit the establishment of Daphnia cristata in the Great Lakes, if 

introduced. 

The ability of Daphnia cristata for parthogenesis may facilitate its establishment, especially if only 

females get introduced to the Great Lakes (Petrusek et al. 2005). It reproduces sexually in harsh 

conditions, producing ephippia that are highly resistant (Benzie 2005). This species is able to expand its 

distribution by migrating from lakes to connected reservoirs (Mordukhaǐ- Boltovskoǐ 1979). 
918

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

5

 Daphnia cristata tolerates an overall moderate to low range of conditions. It has been shown to occur in pH 

levels greater than 5, low calcium levels, moderate (2.5-8 mg/L) dissolved oxygen levels, temperatures at 0-3 ̊C, 

and has been shown to be positively correlated with chlorophyll a levels but no reported ranges (Cairns and 

Yan 2009, Rivier 2005, Wærvågen et al. 2002).

 Daphnia cristata can tolerate lake temperatures in southern Norway average 13-14°C during summer (Hobaek 

et al. 2012, Holtan 1973).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Daphnia cristata has been shown to occur naturally in waters that are 0-3 ̊C. It has been shown to survive in 

low oxygen levels (0.1 mg/L) but has been recorded in higher abundance in 2.5-8 mg/L (Rivier 2005).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

3
919

 Daphnia cristata, as any other Daphnia, feeds on particles in the water column. They can survive off of various 

types of plankton and bacteria but not for long. For continued survival they need a diet of phytoplankton that is 

particular to their filtering capacity (Benzie 2005).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

5

 Daphnia cristata is not a strong competitor for resources but can withstand predation pressure better than other 

cladocerans. Whenever large predation pressure is present, D. cristata is the dominant or one of the dominant 

cladocerans. When this pressure is removed, larger species of cladocerans prevail (Amundsen et al. 2009, 

Nyberg 1998).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

2

 Daphnia cristata has been shown to have similar fecundity to a closely related species, Daphnia longispina

(Rivier 2005). D. longispina may have 3 eggs per clutch, which is small compared to larger Daphnia species 

such as D. magna (up to 100 eggs per clutch) (Ebert 2005).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9
920

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Daphnia cristata is known to produce ephippia that are highly resistant and could aid in establishment and has 

been known to survive in ballast water. However, literature has only predicted the invasion of the Great Lakes 

but not the establishment (Grigorovich et al. 2003, Wonham et al. 2005).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Daphnia cristata occurs mostly in sub arctic regions in Europe and Asia; lakes here experience seasonality and 

develop similar stratification (Benzie 2005, Rivier 2005, Russia 2013)

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8
921

 Daphnia cristata occurs mostly in sub arctic regions in Europe and Asia (Benzie 2005). Water conditions such 

as dissolved oxygen, and temperature can be somewhat similar but not exactly the same (Horppila 1997, 

Johengen et al. 2000, Rivier 2005). This species has been shown to occur in lakes with a specific calcium 

threshold which the Great Lakes can meet (Beeton et al. 1965).

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Daphnia cristata occurs naturally in systems that have similar habitats to the Great Lakes, specifically Lake 

Huron (Johengen et al. 2000, NINA 2007).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

0

 Daphnia cristata naturally occurs in waters that are similar to the larger Great Lakes but are generally colder 

and experience ice cover. If the Great Lakes were to increase in water temperature or lose ice cover, they 

would become unsuitable for D. cristata (Rivier 2005).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?
922

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 Daphnia cristata, as with any other daphnid species, feeds on algae and phytoplankton (Benzie 2005). The 

amount of algae and phytoplankton in a lake can be indicated by the levels of chlorophyll in the lake. Many of 

the Great Lakes still contain relatively high levels of algae, for instance, Saginaw Bay (Johengen et al. 2000).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Daphnia spp. do not require another species for any critical stages in their life cycles. They reproduce largely 

by cyclic parthenogenesis and will only switch to sexual reproduction in response to environmental cues 

(Benzie 2005).

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 9
923

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

1

 Various species of algae and phytoplankton have successfully established in the Great Lakes basin (USGS 

2012). These species could be potential food sources for Daphnia cristata but would not facilitate its 

establishment anymore than naturally occurring algae and phytoplankton.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Daphnia cristata is preyed upon by planktivorous fish which are prevalent in the Great Lakes basin. However 

being one of the smallest Daphnia species, it is known to be resistant to predation pressure and often becomes 

the dominant cladoceran species with high predation levels (NINA 2007, Nyberg 1998, Tallberg et al. 1999).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9
924

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

1

 The possible vector for introduction of Daphnia cristata is through ballast water. However a study done on 

ballast water entering the Great Lakes only showed single individuals surviving (Johengen et al. 2005).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

2

 There is little record of invasion as a possible result of human activities of Daphnia cristata. There is a detailed 

account of D. cristata immigrating downstream into the Volgograd reservoir as a result of more reservoirs 

being constructed (Mordukhaĭ-Boltovskoĭ 1979). These reservoirs are connected directly to lakes where D. 

cristata occurs naturally.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 In the instance of D. cristata spreading into the Volgograd reservoir it spread quickly to other reservoirs 

(Mordukhaĭ-Boltovskoĭ 1979). This is attributed to a very high rate of introduction (simply flowing 

downstream), which would be a combination of human activities (creating the reservoir) and natural means.
925

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no existing control measure that could prevent the establishment of Daphnia cristata once introduced.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 79

>100 High Adjustments

B. Critical species A*(1- 0%) 79

51-99 Moderate C. Natural enemy B*(1- 10%) 71.1

Control measures C*(1- 0%) 71.1

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown
926

Socio-Economic: Low

Beneficial: Moderate

Current research on the potential for environmental impacts to result from Daphnia cristata if 

introduced to the Great Lakes is inadequate to support proper assessment. 

Daphnia cristata does not pose a threat to other species or water quality. It does not out-compete native 

species for available resources. It is not a strong competitor, but becomes abundant by escaping predation 

in the presence of planktivorous fish, which consume other zooplankton species (Amundsen et al. 2009, 

Nyberg 1998). 

There is little or no evidence to support that Daphnia cristata has the potential for significant socioeconomic impact if introduced to the Great Lakes.

It has not been reported that Daphnia cristata poses a threat to human health or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits. 

Daphnia cristata has the potential for moderate beneficial effects if introduced to the Great Lakes.

Its diet may include toxic algae (Benzie 2005). It may be able to remove a negligible amount of toxic 

algae. When predation pressure from planktivorous fish is high, the abundance of Daphnia cristata 

increases (Amundsen et al. 2009, Nyberg 1998). If fish predation removes a large portion of 

phytoplankton consumers from the water body, it may result in an increase in chlorophyll concentration 

and an algal bloom (Andersson et al. 1978). The increase in abundance of Daphnia cristata during times 

of high predation pressure may replace the loss of phytoplankton consumers and suppress an algal bloom 

to some extent. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 Daphnia cristata poses no natural hazard to other species.
927

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

 Daphnia cristata is not a strong competitor. It generally loses out in competition and is recorded in higher 

abundances only in the presence of planktivorous fish (Amundsen et al. 2009, Nyberg 1998).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

 Daphnia cristata has been shown to occupy available niches when present (Wærvågen et al. 2002). It is 

generally is recorded only in the presence of planktivorous fish (Amundsen et al. 2009, Nyberg 1998, 

Wærvågen et al. 2002).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 1 
928

effects have been limited or inconsistent (as compared with above statement)

Not significantly 0 √

Unknown U

 There have been no reports of any environmental effects from this organism. Daphnia cristata is a very small 

organism and generally fills a specialized niche (Amundsen et al. 2009, NINA 2007). Its effect on water quality 

would be negligible.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 There have been no reports of any environmental effects from this organism.

Environmental Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 
929

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata posing any threat to human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata damaging infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata affecting water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata affecting markets or economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6
930

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata inhibiting recreational activities or tourism.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There has been no evidence of Daphnia cristata diminishing the aesthetic or natural value of the lakes it 

inhabits.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 
931

Not significantly 0 √

Unknown U

 Daphnia cristata as a filter feeder could possibly be used to control algae species although there have been no 

reports of it successfully doing so.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 There is no evidence of Daphnia cristata having any sort of commercial value.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is no evidence of Daphnia cristata having any sort of recreational value.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 There is no evidence of Daphnia cristata having significant medicinal or research value. It has been recorded in 

various natural observations and studies but not in any significant way.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 
932

 Daphnia cristata is a filter feeder and part of its diet could include toxic algae but this effect would be negligible 

compared to larger filter feeders (Benzie 2005).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 

 Daphnia cristata could possibly fill in a gap in natural food webs. It has been known to occur when fish 

predation pressure is very high ( Amundsen et al. 2009, Nyberg 1998).

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
933

Scientific Name: Podonevadne trigona ovum

Zernov, 1901

Common Name: Waterflea

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Podonevadne trigona ovum has a low probability of introduction to the Great Lakes (Confidence 

level: high).

Potential pathway(s) of introduction: Transoceanic Shipping

Podonevadne trigona ovum has not been reported in or near the Great Lakes basin. This species has 

limited mobility (Zinevici et al. 2011). The eggs of Podonevadne trigona ovum may be transported by 

birds, but it is unlikely that it would be carried overseas. The resting egg stage of this species is hardy and 

may be able to survive ballast tank environments for long periods of time; however, it may be flushed out 

during ballast exchange. 

It has the potential to be introduced to the Great Lakes if the distribution of Podonevadne trigona ovum 

spreads to the eastern Baltic, and survives transport via an existing invasion corridor between the eastern 

Baltic and the Great Lakes (Grigorovich et al. 2003, Panov et al. 1999). This species has already been 

observed outside its native range in the Danube-Black Sea canal, the reservoirs and lagoons of the Bug, 

Dneipr, Dniestr, Don, and Volga rivers (Zinevici et al. 2011), and Kahovka (Rivier 1998). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 √
934

not mobile or able to be transported by wind or water.

Unknown U

 Podonevadne trigona ovum has not been reported in or near the Great Lakes basin. A characteristic of the 

Podonevadne genus is limited mobility (Zinevici et al. 2011).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 While Podonevadne trigona ovum eggs may be able to be transported by birds (Zinevici et al. 2011), it is 

unlikely that the carrier would be capable of transoceanic travel.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
935

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
936

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Podonevadne trigona ovum has a resting egg stage of its life history that is hardy. However, the species has 

extremely limited mobility and may be flushed out during ballast exchange.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes Score x 0
937

originates.

Unknown U

 Zinevici et al. (2011) observed Podonevadne trigona ovum in nearly the entire basin of the Danube-Black Sea 

canal. Podonevadne trigona ovum spread rapidly over 20 years from being an occasional species in 1985 to 

being a persistent species by 2005—64 km in 87 months or less (Zinevici et al. 2011).

 Podonevadne trigona ovum has also been recorded in the Black and Caspian seas (Cristescu 2003), as well as 

the waters of Romania and the reservoirs and lagoons of the Bug, Dnieper, Dniester, Don, and Volga rivers 

(Zinevici et al. 2011).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 8 Low

Total Unknowns (U) 0 Confidence Level High
938

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Podonevadne trigona ovum has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

The climate of the Great Lakes is similar to the Ponto Caspian basin (USEPA 2008). Its life cycle aligns 

with the seasons (Zinevici et al. 2011). The resting egg stage that occurs over the winter is hardy and may 

be able to survive the harsh winters of the Great Lakes basin, but this has not been specifically tested. It 

reproduces rapidly and has a short generation time. If introduced to the Great Lakes, this species may 

establish a population via asexual reproduction; in the Danube-Black Sea Canal, the population of 

Podonevadne trigona ovum was formed primarily by parthenogenetic females, a common method of 

reproduction in favorable environmental conditions. It is likely to find a food source in the Great Lakes 

because it feeds on ciliates, rotifers, nauplii, small cladocerans, and nanoplanktonic algae (Egloff et al. 

1996, Zinevici et al. 2011). If established, it may be preyed on by macroinvertebrates and small fish, but 

may not impact establishment significantly. It has been reported to occur in the Aral Sea as a nonnative 

species twice (Aladin 1995) and has extended its range to include the Danube-Black Sea canal (Zinevici 

2011). It has spread rapidly through all parts of the Danube-Black Sea canal ecosystem in 20 years. It has 

been reported as a species of concern in Finnish waters (Pienimӓki and Leppäkoski 2004).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Podonevadne trigona ovum has an upper salinity tolerance of 22 g l-1(Aladin and Potts 1995). Tolerance 

appears to depend on the concentration of chloride, rather than total salinity. Cladocerans in general cannot 

tolerate anoxic conditions (Havel et al. 2009).
939

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Podonevadne trigona ovum has a resting egg stage that occurs during the winter months that may be capable of 

surviving harsh winters typical of the Great Lakes region. However, the limits of the resting egg stage have not 

been tested.

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Podonevadne trigona ovum feed mainly on ciliates, rotifers, nauplii, small cladocerans and, in addition, 

nanoplanktonic algae (Egloff et al. 1996).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
940

Unknown U

6

 In the 2011 article, Zinevici et al. described an environment in which Podonevadne trigona ovum was the 

strongest positioned predacious zooplankton in the community found in the Danube canal. This suggests that 

Podonevadne trigona ovum is a strong competitor at certain times of the year.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 The methods of reproduction are known for Podonevadne trigona ovum, but fecundity has not been documented 

and/or compared to other species in its taxonomic class. 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Podonevadne trigona ovum population in Danube-Black Sea was formed exclusively by parthenogenetic 

females, which is a common situation for cladocerans living in permanent aquatic ecosystems characterized by 

favorable environmental conditions (Zinevici et al. 2011).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
941

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Podonevadne trigona ovum is found in Danube-Black Sea canal , prefers very low to no water flow velocity; 

also, found in heterogeneous environment, submerged and emergent macrophytes in Zinevici et al. (2011), with 

no specific habitat requirements.
942

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Podonevadne trigona ovum has a high salinity tolerance (Aladin and Potts 1995), and is known to exist in an 

environment somewhat warmer than the Great Lakes currently are. Podonevadne trigona ovum has limited to 

no mobility, making it susceptible to streamflow patterns.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 It is likely that Podonevadne trigona ovum feed mainly on ciliates, rotifers, nauplii, small cladocerans and, in 

addition, nanoplanktonic algae (Egloff et al. 1996).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

9
943

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Podonevadne trigona ovum has not been observed to require a critical species in order advance to the next 

stage of the life cycle.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 The relationships between Podonevadne trigona ovum and other species are not documented, but it appears 

that this species is self-sufficient. Podonevadne trigona ovum’s prey may be the only possibility of aid.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)
944

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Some predation by macroinvertebrates and small fish, but not enough to impact establishment significantly. 

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Ballast exchange may remove most of the viable adults and resting eggs.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 Podonevadne trigona ovum has been reported to be invasive to the Aral Sea twice (Aladin and Potts 1995), as 

well as expanding its range in the Danube-Black Sea Canal (Zinevici et al. 2011). Podonevadne trigona ovum
945

has also been reported in the Aral Sea, and is a species of concern for Finnish waters (Pienimӓki and 

Leppӓkoski 2004).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

8

 Podonevadne trigona ovum has a life cycle that aligns with the seasons, allowing it to have a short life history 

and quick reproduction. It has spread through all parts of the Danube-Black Sea Canal ecosystem in 20 years 

(Zinevici et al. 2011).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0
946

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 98

>100 High Adjustments

B. Critical species A*(1- 0%) 98

51-99 Moderate C. Natural enemy B*(1- 10%) 88.2

Control measures C*(1- 0%) 88.2

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

Podonevadne trigona ovum has the potential for moderate environmental impact if introduced to 

the Great Lakes.

This species established in the Danube-Black Sea canal, subsequently outcompeted indigenous species, 

and was one of the few dominant species in the zooplankton structure (Zinevici et al. 2011). Its presence 

there has significantly altered the zooplantonic food web. It is not yet known whether this species affects 

the health or genetics of native populations, impacts water quality, or alters the physical components of 

the ecosystem. 

There is little or no evidence to support that Podonevadne trigona ovum has the potential for 

significant socio-economic impacts if introduced to the Great Lakes. 

It has not been reported that Podonevadne trigona ovum poses hazards to human health, damages 

infrastructure, negatively effects water quality, adversely impacts economic sectors, inhibits recreational 

activities or associated tourism, or diminishes the perceived aesthetic or natural value of the areas it 

inhabits in a significant manner. 
947

There is little or no evidence to support that Podonevadne trigona ovum has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

There have not been studies that show that Podonevadne trigona ovum can act as a biological control 

agent for aquatic weeds or other harmful nonindigenous organisms. This species is a predatory 

zooplankton, but is not selective in its feeding behavior, so it is unlikely that it can significantly control 

populations of other nonindigenous zooplankton. Podonevadne trigona ovum does not have significant 

commercial, recreational, or medical value. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 Zinevici et al. (2011) observed Podonevadne trigona ovum outcompete the indigenous species in the DanubeBlack Sea canal. 

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √
948

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U 

 Zinevici et al. (2011) indicated that the presence of P. t. ovum significantly altered the zooplantonic food web of 

the environment into which it had invaded, and has also become the dominant predator.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 2

Total Unknowns (U) 4
949

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U 
950

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U 

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
951

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 As a predatory zooplankton, Podonevadne trigona ovum may be capable of controlling populations of 

nonindigenous zooplankton. However, Podonevadne trigona ovum’s prey is not well studied.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U 
952

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
953

A.6 Crustaceans - Copepods

Scientific Name: Calanipeda aquaedulcis

Kritchagin 1873

Common Name: Calanoid Copepod

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Calanipeda aquaedulcis has a moderate probability of introduction to the Great Lakes (Confidence 

Level: High)

Potential Pathway(s): Transoceanic Shipping (ballast water)

Calanipeda aquaedulcis has not been reported to occur in North or South America (Svetlichny et al. 

2012b). There is no evidence that suggests that Calanipeda aquaedulcis is currently stocked, cultured, or 

sold commercially in the Great Lakes region. This species is not known to attach to recreational gear and 

is not being transported through the Great Lakes region. The potential risk for invasion originates from 

the established populations in the Baltic Sea basin, which is an area that has direct trade connections with 

the Great Lakes (NBIC 2009). 

There is a possibility for Calanipeda aquaedulcis to be introduced to the Great Lakes if it survives 

overseas transport originating in the Baltic Sea. It produces resting eggs that may be resistant to salinity 

increases during ballast exchange, but may be flushed in the process (Frisch et al. 2006, Svetlichny et al. 

2012b, Wonham et al. 2005). The adult forms are osmo-conformers that can tolerate a wide range of 

salinity and may survive ballast water exchange as well (Svetlichny et al. 2012a).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, 
954

including connecting channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Calanipeda aquaedulcis has not yet been identified in North or South America (Svetlichny et al. 2012b).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 There is no evidence that C. aquaedulcis has been found attached to recreational gear.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
955

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 After searching different commercial stores, nothing was found on the sale of C. aquaedulcis.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 Nothing found on stocking of C. aquaedulcis.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 100
956

region.

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There was no evidence showing that C. aquaedulcis is commercially cultured or transported through the Great 

Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Since C. aquaedulcis produces resting eggs, it would not be affected heavily by salinity increases during ballast 

exchange (Frisch et al. 2006, Svetlichny et al. 2012b), but it could potentially be flushed.

 It has the potential to survive ballast water exchange due to its high adaptability. Calanipeda aquaedulcis is an 

osmo-conformer that can survive at varying salinity levels (Svetlichny et al. 2012a).

 Calanipeda aquaedulcis likely entered the Bilbao estuary, along with other copepods, through the transport of 

ballast water (Albaina et al. 2009).
957

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the 

Great Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections 

with the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the 

Great Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

No, this species does not occur in waters from which shipping traffic to the Great 

Lakes originates.

Score x 0

Unknown U

 While there is no direct shipping between the Great Lakes and the Ponto-Caspian (USEPA 2008), where C. 

aquaedulcis is native, this species is also found in Europe (Morocco, Spain, Mediterranean coastal areas), 

Russia, and North Africa.

 Calanipeda aquaedulcis is found in the Caspian Sea basin (including reservoirs of the Dnieper, Don, and Volga 

rivers) and Mediterranean; it is reported from Mallorca, Minorca, Camargue (France), Corsica, Sardinia, 

Sicily, North Africa (Morocco, Algeria, Tunisia), Portugal, Turkey, and Ukraine (Boxshall and Defaye 2009).

 It is also found in Italy, including in Lake Lesina (Lesina Lagoon) on the Adriatic Sea coast (Brugnano et al. 

2011).

 Calanipeda aquaedulcis invaded the Aral Sea in the 1960s (Mirabdullayev et al. 2004) and the Bilbao estuary, 

Spain in 2001 (Albaina et al. 2009).

 The USEPA (2008) identified in their report the risk of invasion of this species from established populations in 

the Baltic Sea basin.
958

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not currently established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
959

Calanipeda aquaedulcis has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: High)

The native range of Calanipeda aquaedulcis has similar climatic and abiotic conditions to that of the 

Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Calanipeda aquaedulcis is 

found in the Mediterranean coastal areas of Europe, which has summers similar to the Great Lakes, and 

the Azov Sea, which has winters as cold as those in the Great Lakes (Svetlichny et al. 2012b). Calanipeda 

aquaedulcis can tolerate a broad range of temperatures, oxygen levels, and salinities. Due to its ability to 

thrive in low temperatures and tolerate low oxygen levels, it is likely that Calanipeda aquaedulcis is able 

to overwinter in the Great Lakes basin if introduced. This species can adapt rapidly to fresh and salt water 

environments due to its osmo-independent metabolism (Svetlichny et al. 2012b). Increased salinization 

attributed to climate change may render the Great Lakes more suitable for this estuarine species (Brucet et 

al. 2008). It is found primarily in ogliotrophic waters, but can survive in eutrophic environments (Saygi et 

al. 2011, Svetlichny et al. 2012b). It has established in Lesina Lagoon, Italy, which experiences many of 

the same pollution issues that affects the Great Lakes (agricultural, wastewater treatment plants, 

watershed resident populations (Brugnano et al. 2011).

Due to its flexible, omnivorous diet, it is likely that Calanipeda aquaedulcis will find a suitable food 

source if introduced to the Great Lakes (Brucet et al. 2008). Calanipeda aquaedulcis may be preyed on by 

freshwater fish; however, it is unlikely that these predators will specifically target Calanipeda 

aquaedulcis. Calanipeda aquaedulcis produces resting eggs that may be capable of overwintering in the 

Great Lakes (Frisch et al. 2006, Svetlichny et al. 2012b). The egg densities that this species produces may 

be larger than those produced in its native range due to the lower salinity of the Great Lakes. The 

discharge of resting eggs in ballast sediment is thought to be infrequent and moderate in size. 

Calanipeda aquaedulcis has expanded outside its native range considerably. This species can rapidly 

establish a dominant population after introduction. Ten years after its introduction to the Aral Sea in the 

1960s, Calanipeda aquaedulcis became one of the dominant zooplankton species and consequently 

eliminated other zooplankton (Mirabdullayev et al. 2004). However, this species disappeared from the 

region in 1997. It has been suggested that Calanipeda aquaedulcis was introduced to the Bilbao estuary 

through the transport of ballast water (Albaina et al. 2009). This species was established there in 2001. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

9

 Calanipeda aquaedulcis can adapt rapidly to fresh and salt water environments and has an osmo- and 

oxygen-independent metabolism (Svetlichny et al. 2012b)
960

 This species was shown to have a broad pH and temperature tolerance (at least 3-30°C) (Frisch et al. 

2006, Marques et al. 2008). 

 Calanipeda aquaedulcis is found primarily in oligotrophic environments independent of light and oxygen 

levels, but it is also able to survive in eutrophic environments (Saygi et al. 2011, Svetlichny et al. 2012b). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Calanipeda aquaedulcis has been known to thrive during the winter periods and has little effects from oxygen 

levels (Brugnano et al. 2011).

 Calanipeda aquaedulcis has a temperature range of about 3-30 ̊C but prefers cooler temperatures (Frisch et al. 

2006).

 As this species produces resting eggs, it is likely to survive harsh conditions.

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Calanipeda aquaedulcis was shown to have a diverse diet, having varying dietary habits at different stages of 

life and based on what is readily available (Brucet et al. 2008).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

6
961

species in the Great Lakes)

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

6

 The introduction of C. aquaedulcis into the Aral Sea in the 1960s resulted in it being the dominant species and 

eliminating other zooplankton. However, in 1997, it disappeared (Mirabdullayev et al. 2004).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 Calanipeda aquaedulcis ovisacs usually stay attached to the female until they are hatched, unless under stressful 

conditions (Frisch et al. 2006, Svetlichny et al. 2012b). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

5

 The reproductive strategy of these species involves more parental investment than related species. Calanipeda 

aquaedulcis females keep their eggs attached to them until they are hatched compared to other that having 

resting eggs (Svetlichny et al. 2012b).
962

 At 18 ppt salinity, the C. aquaedulcis had significantly higher egg density compared to the related species 

Arctodiaptomus alinus. Calanipeda aquaedulcis was not tested at near fresh water salinity but A. salinus

increased egg density at lower salinities (Svetlichny et al. 2012a).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Calanipeda aquaedulcis can be found in the Mediterranean coastal areas of Europe, which experiences 

summers much like that of the Great Lakes, and in the Azov Sea, which has winters reaching temperatures as 

cold as those in the Great Lakes (Svetlichny et al. 2012b).

 The Ponto-Caspian (Caspian, Azov, and Black Seas) have similar climate and surface water temperature 

ranges as the Great Lakes ( Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Calanipeda aquaedulcis of the Lesina Lagoon in Italy experiences many of the same pollution issues as the 

Great Lakes (agricultural, wastewater treatment plants, watershed resident population) and many different 

natural disturbances. The zooplankton community is able to respond rapidly to a change in these conditions 

(Brugnano et al. 2011).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?
963

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Calanipeda aquaedulcis is found primarily in oligotrophic environments independent of light and oxygen levels, 

but it is also able to survive in eutrophic environments (Saygi et al. 2011, Svetlichny et al. 2012b). 

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Calanipeda aquaedulcis is commonly found in estuarine or brackish waters, making an increase in salinity a 

more suitable environment (Brucet et al. 2008).

 This species was shown to have a broad pH and temperature tolerance (Marques et al. 2008).

 Calanipeda aquaedulcis has a temperature range of about 3-30 ̊C but prefers the cooler temperatures (Frisch et 

al. 2006).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0
964

Unknown U

7

 Calanipeda aquaedulcis can change dietary habitats throughout development based on what is available (Brucet 

et al. 2008).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Calanipeda aquaedulcis shows no reliance on other species for reproduction or survival.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0
965

Unknown U

0

 No species has been shown to facilitate the development of this species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 Calanipeda aquaedulcis is a macroinvertebrate that could have a natural predator in the Great Lakes but would 

not specifically target this species since most freshwater fish feed on copepods (Saygi et al. 2011).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

 Discharge of resting eggs in sediment would likely be infrequent and moderate in size.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?
966

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Calanipeda aquaedulcis invaded the Bilbao estuary in 2001 (Albaina et al. 2009) and also the Aral Sea in the 

1960s (Mirabdullayev et al. 2004).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 Calanipeda aquaedulcis was expected to enter the Bilbao estuary through the transport of ballast water 

(Albaina et al. 2009).

 The introduction of C. aquaedulcis into the Aral Sea in the 1960s resulted in it being the dominant species by 

1970 (Mirabdullayev et al. 2004).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0
967

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 97

>100 High Adjustments

B. Critical species A*(1- 0%) 97

51-99 Moderate C. Natural enemy B*(1- 0%) 87.3

Control measures C*(1- 0%) 87.3

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Calanipeda aquaedulcis 

if introduced to the Great Lakes is inadequate to support proper assessment

If Calanipeda aquaedulcis is established in the Great Lakes, it may outcompete native species for 

available resources. It became one of the dominant species in the zooplankton communities after 

establishing in the Aral Sea and Bilbao estuary (Albaina et al. 2009, Mirabdullayev et al. 2004). There is 

no evidence suggesting that Calanipeda aquaedulcis alters its habitat or exhibits toxic effects. It is 

unknown if Calanipeda aquaedulcis modifies the physical components of the ecosystem, alters predatorprey relationships, or affects native populations genetically. 
968

There is little or no evidence to support that Calanipeda aquaedulcis has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Calanipeda aquaedulcis poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Calanipeda aquaedulcis has the potential for beneficial 

impacts if introduced to the Great Lakes.

It has not been indicated that Calanipeda aquaedulcis can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts. 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 There is no direct evidence of C. aquaedulcis having a toxic effect.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 When introduced in the Aral Sea in the 1960s, it became the dominant species by the 1970s (Mirabdullayev et 

al. 2004).

 It also became one of the dominant species in the Bilbao estuary after potential invasion through ballast water 

(Albaina et al. 2009).
969

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 There has been no evidence provided that C. aquaedulcis alters predator-prey relationships; however, by 

replacing other species during invasion, it may have unreported trophic impacts.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 It is unknown whether C. aquaedulcis affects native populations genetically.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

 Calanipeda aquaedulcis is not known to alter its habitat, as it is known as a conformer and can adapt to 

different habitats (Svetlichny et al. 2012a).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

6
970

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 It is unknown if C. aquaedulcis alters the physical components of an ecosystem.

Environmental Impact Total 1

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There is no indication that C. aquaedulcis poses a threat to human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1
971

Not significantly 0 √

Unknown U

 There is no indication that C. aquaedulcis causes damage to the infrastructure, but since it does not attach and 

is small in size, it can be inferred it would not cause significant damage.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 Calanipeda aquaedulcis is not known to alter the water quality positively or negatively.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 Calanipeda aquaedulcis does not cause a strong decrease in any species that would negatively affect an

economic sector.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no evidence that C. aquaedulcis would inhibit recreational activities. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There is no impact reported for C. aquaedulcis on the aesthetic appeal of a habitat.
972

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There is no record of this species as a control for other organisms.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 There is no indication that it is commercially valuable.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6
973

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is no indication that it is recreationally valuable.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 There is no indication that it has medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There is no indication that it removes toxins or pollutants from the water.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 Calanipeda aquaedulcis could potentially contribute to another food source in the food web since the majority of 

freshwater fish eat copepods.

Beneficial Effect Total 0

Total Unknowns (U) 0
974

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
975

Scientific Name: Cyclops kolensis

Lilljeborg, 1901

Common Name: Waterflea

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Cyclops kolensis has a moderate probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Cyclops kolensis does not currently occur near waters connected to the Great Lakes basin. Although 

uncommon, aquarists sell Cyclops copepods as frozen fish food, but it is unlikely that this particular 

species, Cyclops kolensis, is sold. 

Cyclops kolensis produces resting eggs that may be carried in ballast water or sediment and may survive 

overseas transport (Grigorovich et al. 2003, USEPA 2008, Wonham et al. 2005). They produce a large 

number of eggs (0.8 million eggs/m2) that float at the surface of the water and sink slowly when disturbed 

(Rivier 1996).

This species occurs in ports that have direct trade connections with the Great Lakes (NBIC 2009). It 

inhabits areas from southern Sweden through Poland, and from Germany to Lake Baikal (Reed 1968). 

There is a second distribution belt from the Arctic coast of Eurasia to Alaska. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 100
976

able to be transported by wind or water.

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 There are no data found that states Cyclops kolensis occurs near waters connected to the Great Lakes basin 

and is mobile or able to be transported by wind or water. Data show that this species occurs near the PontoCaspian region (Grigorovich et al. 2003) and around Alaska (Reed 1968).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
977

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 No data have been found about if this species is being stocked or planted to natural waters or outdoor water 

gardens around the Great Lakes region. 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 No data have been found about if this species is being stocked or planted to natural waters or outdoor water 

gardens around the Great Lakes region. 

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100
978

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 No articles mention that this species is being commercially cultured.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U 

 There were no data found that state that Cyclops kolensis occurs near waters connected to the Great Lake 

basin. Data show that this species occurs near the Ponto-Caspian region (Grigorovich et al. 2003) and around 

Alaska (Reed 1968).

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This Ponto-Caspian copepod was identified as having high probability of invasion if introduced to the Great 

Lakes via ballast water or sediment, where it may survive as a resting stage (Grigorovich et al. 2003, USEPA 

2008, Wonham et al. 2005).

 Cyclops kolensis is a summer diapausing species (Frisch 2002).

 Cyclops kolensis eggs can reach densities of 0.8 million individuals/m2. The eggs have a specific gravity close 

to water, and, when disturbed, remain at the water surface and sink slowly (Rivier 1996).
979

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species inhabits areas from southern Sweden through Poland and Germany to Lake Baikal; there is a 

second distribution belt from the Arctic coast of Eurasia to Alaska (Reed 1968).
980

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
981

Cyclops kolensis has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

The native and introduced ranges of Cyclops kolensis have similar climate and abiotic conditions to that 

of the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Cyclops kolensis 

inhabits areas of similar latitudes to the Great Lakes; it occurs in southern Sweden through Poland, and 

Germany to Lake Baikal, and a second distribution belt from the Arctic coast of Eurasia to Alaska (Reed 

1968). Due to the ability of this species to tolerate ice-covered waters, it is likely that it will be able to 

overwinter in the Great Lakes. Cyclops kolensis inhabits environments with similar anthropogenic 

stressors as the Great Lakes. This species thrives in eutrophic water bodies, so pollution in the Great 

Lakes may facilitate its establishment (Kozminski 1936). The abundance of its preferred prey, calanoid 

copepods, in the Great Lakes may further facilitate Cyclops kolensis establishment (Wickham 1995). 

Inoculations are likely to consist of small numbers of diapausing eggs.

This species has been documented at relatively high densities (400 individuals/m2), at numbers greater 

than endemic copepods (Pislegina and Silow 2009). In Lake Baikal, it has been reported that Cyclops 

kolensis dominated zooplankton communities in some years, reaching 80-90% of the total zooplankton 

biomass (Mazepova 1998). Consequently, there was a decrease in the abundance of their preferred prey, 

Epischura.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Cyclops kolensis thrives in eutrophic lakes and occurs sparingly in oligotrophic areas (Kozminski 1936).

 Temperature tolerance ranges from from ice-covered waters (Kozminski 1933) to temperatures of 18-20°C in 

the summer (Reed 1968).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6
982

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Cyclops kolensis is a cold water species (Reed 1968).

 In Poland, maximum population density occurs under the ice during February and March (Kozminski 1933).

 This species congregates in almost oxygen-free waters of Lake Wigry, Poland in February and March 

(Kozminski 1936).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

3

 Cyclops kolensis species is a small predator (e.g., feeds mainly on larvae of Epischura) (Mazepova 1998).

 Cyclops kolensis is known to be highly selective of prey (Adrian 1991).

 Cyclops kolensis prefers small prey over larger prey and is raptorial (Wickham 1995).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

5

 Cyclops kolensis has been documented at relatively high densities (400 individuals/m2), with higher densities 

than endemic copepods (Pislegina and Silow 2009).

 In the abundant years, 1946 and 1950, Cyclops reached 80–90% of the total biomass of the zooplankton 

(Mazepova 1998).
983

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

2

 Cyclops kolensis is univoltine, with one brood per year which is released in multiple clutches. It has a clutch 

size mean of 20-30 eggs and can produce at least 5 clutches a year with about 8 days in between (Jamieson 

2003).

 Cyclops kolensis has three generations a year (Mazepova 1998).

 A study by Phong et al. (2008) of six cyclopoid species (genus Mesocyclops) found a range of 2.6-10.3 clutches 

per mating event (with mode between 4-5 clutches/event). Total clutch size ranged from 51.7-117. 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

2

 Cyclops kolensis requires sexual reproduction, but can produce resting eggs.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6
984

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Cyclops kolensisi inhabits areas of similar latitudes to the Great Lakes, from southern Sweden through Poland 

and Germany to Lake Baikal and a second distribution belt from the Arctic coast of Eurasia to Alaska (Reed 

1968).

 Cyclops kolensis is a Ponto-Caspian species. The Great Lakes and Ponto-Caspian region are climatically 

compatible, which is one of the attributing factors to the success of Ponto-Caspian species in the Great Lakes 

(Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Cyclops kolensis inhabits areas with similar anthropogenic stressors as the Great Lakes.

 Cyclops kolensis dwells in freshwater habitats and prefers lotic areas.

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Cyclops kolensis is typical of the pelagic region of permanent lakes (Einsle 1996, Santer and Lampert 1995, 

Schubert 1986).

 Cyclops kolensis was shown to have a capacity for dispersal (Frisch 2002).
985

 Cyclops kolensis thrives in eutrophic lakes and occurs sparingly in oligotrophic areas (Kozminski 1936).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

4

 Cyclops kolensis has mixed effects and will depend on lake and degree of warming:

 Species numbers have shown a positive correlation with temperature (from about 3.8°C to78°C) (Pislegina and 

Silow 2009).

 Cyclops kolensis gradually declined in long-term study of warming German waters, 2.58°C in April, from 

about 7.5°C to just over 10°C, and was functionally replaced by the larger cyclopoid Cyclops vicinus (Adrian 

and Deneke 1996).

 Cyclops kolensis reproduction ceases and diapauses begins at 12-15°C (Rivier 1996).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 Cyclops kolensis consumes calanoid copepods, which are plentiful in the Great Lakes.

 Cyclops kolensis consumes ciliates and cladocerans (Wickham 1995).
986

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?
987

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

 Inoculations are likely to consist of small numbers of diapausing eggs in ballast water or sediment.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
988

Unknown U

3

 Cyclops kolensis was shown to have a capacity for dispersal (Frisch 2002).

 Cyclops kolensis established in the European part of Russia (DAISIE 2008a).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

2

 No data on rate of spread were found, but C. kolensis dispersal has been documented (Frisch 2002).

 Cyclops kolensis is an active migrant from the northern water-bodies of Russia to the Volga reservoirs (Rivier 

1996).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 76

>100 High Adjustments
989

B. Critical species A*(1 - 0%) 76

51-99 Moderate C. Natural enemy B*(1 - 10%) 68.4

Control measures C*(1 - 0%) 68.4

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Cyclops kolensis if 

introduced to the Great Lakes is inadequate to support proper assessment.

It has been reported that Cyclops kolensis can dominate zooplankton communities. In Lake Baikal, it 

reached 80-90% of the total zooplankton biomass during a couple of years (Mazepova 1998). Cyclops 

kolensis has the potential to reduce the abundance of its prey. As a consequence of their population 

growth, Cyclops kolensis reduced the abundance of their preferred prey, Epischura. It is possible that 

Cyclops kolensis may compete with other organisms that feed on Epischura. This species has been 

documented at relatively high densities (400 individuals/m2), at numbers greater than endemic copepods 

(Pislegina and Silow 2009). As a prey item, Cyclops kolensis has the potential to alter trophic dynamics 

by providing a source of food for the juvenile ruffe, Gymnocephalus cernua (Rivier 1996).

Cyclops is also an intermediate host for the tapeworm Diphyllobothrium, which infects fish such as 

salmon (CDC 2013). It has not been reported that this particular species, Cyclops kolensis, is a host for 

this tapeworm.

There is little or no evidence to support that Cyclops kolensis has the potential for significant socioeconomic impact if introduced to the Great Lakes.

Cyclops species are vectors of several parasites. Members of this genus are an intermediate host for 

Dracunculus medinensis (Guinea Worm) which affects humans who drink water contaminated with 

infected water fleas. In dracunculiasis, or Guinea Worm disease, female worms are liberated from the 

water fleas after digestion, and subsequently move through the person’s subcutaneous tissue, causing 
990

intense pain (WHO 2013). It eventually emerges through the skin, usually at the feet, producing oedema, 

a blister that will become an ulcer. Guinea Worm disease is accompanied by fever, nausea, and vomiting. 

Cyclops is also an intermediate host for the tapeworm Diphyllobothrium, which infects fish such as 

salmon (CDC 2013). Humans can be infected by ingesting undercooked fish. It is not known if this 

particular species Cyclcops kolensis is a vector for these diseases. 

It has not been reported that Cyclops kolensis poses a threat to water quality. There is no evidence that 

this species negatively impacts infrastructure, economic sectors. There is no indication that Cyclops 

kolensis affects recreational activities and associated tourism, or the aesthetic appeal of the areas it 

inhabits.

There is little or no evidence to support that Cyclops kolensis has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Cyclops kolensis can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 This species is a vector of several parasites. The rate of infection is unknown.

 Cyclops species are an intermediate host for Dracunculus medinensis (Guinea worm). In dracunculiasis 

(Guinea worm disease), female worms move through the person’s subcutaneous tissue, causing intense pain, 

and eventually emerge through the skin, usually at the feet, producing oedema, a blister and eventually an 

ulcer, accompanied by fever, nausea, and vomiting (WHO 2013).

 Copepods are intermediate host for the tapeworm Diphyllobothrium, which can infect fish (particularly salmon) 

and can be passed to humans through ingestion of undercooked fish. The resulting diphyllobothriasis can 

include diarrhea, abdominal pain, vomiting, weight loss, fatigue, constipation and discomfort (CDC 2013).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 1 
991

fecundity) or decline of at least one native population

Not significantly 0

Unknown U √

 While its competitive effects are unknown, this species has been documented at relatively high densities (400 

individuals/m2), with higher densities than endemic copepods (Pislegina and Silow 2009).

 In abundant years (1946 and 1950), Cyclops reached 80–90% of the total biomass of the zooplankton in Lake 

Baikal (Mazepova 1998).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Cyclops kolensis forms 0.9% of the net primary production in Lake Baikal (Mazepova 1998). It is also seen in 

other water basins (Odum 1968). Thus, it is unlikely to cause significant shifts in food webs.

 Cyclops kolensis is the major food source for juvenile ruffe, Gymnocephalus cernua (Rivier 1996).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 No information was provided in located articles.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 
992

Unknown U √

 No information was provided in located articles.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 No information was provided in located articles.

Environmental Impact Total 1

Total Unknowns (U) 5

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
993

Not significantly 0 

Unknown U √

 Cyclops species are an intermediate host for Dracunculus medinensis (Guinea worm). In dracunculiasis 

(Guinea worm disease), female worms move through the person’s subcutaneous tissue, causing intense pain, 

and eventually emerge through the skin, usually at the feet, producing oedema, a blister and eventually an 

ulcer, accompanied by fever, nausea, and vomiting (WHO 2013).

 Copepods are intermediate host for the tapeworm Diphyllobothrium, which can infect fish (particularly salmon) 

and can be passed to humans through ingestion of undercooked fish. The resulting diphyllobothriasis can 

include diarrhea, abdominal pain, vomiting, weight loss, fatigue, constipation, and discomfort (CDC 2013) .

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 No article mentioned how water quality might change if this species was introduced.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 No information was available.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
994

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 No reports were found.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 
995

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 
996

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
997

Scientific Name: Ectinosoma abrau

Kritchagin, 1877

Common Name: Oarsman, Harpacticoid Copepod

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Ectinosoma abrau has a low probability of introduction to the Great Lakes (Confidence level:

High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Ectinosoma abrau is occurs in the Black Sea and Azov Sea in eastern Europe, including Lake Ohrid of 

the Balkan peninsula, which drains into the Adriatic Sea and Lake Balaton (Grigorovich et al. 2003,

Petkovski and Karanovic 1997). Ships originating in eastern Europe can potentially pick up this species 

and introduce it to the Great Lakes; however, this has not been observed (Grigorovich et al. 2003).

Ectinosoma abrau produces resting stage eggs that are capable of surviving harsh conditions such as 

ballast water and sediment (Wonham et al. 2005). This species can tolerate salinities up to 30 ‰ (Aladin 

et al. 2008); Ectinosoma abrau is a marine organism so it is likely that it is capable of surviving overseas 

transport. Ectinosoma abrau does not currently occur in waters near the Great Lakes.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
998

 Ectinsoma abrau does not occur in waters near the Great Lakes; it is found in the Black Sea region of eastern 

Europe (Grigorovich et al. 2003).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Ectinosoma abrau is found in eastern Europe (Grigorovich et al. 2003).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 This species is not known to be sold. 
999

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 This species is not known to be stocked or recreationally cultured.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 This species is not known to be commercially cultured or transported in North America.
1000

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This species is listed as being capable of survival in ballast tanks (Grigorovich et al. 2003).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1 

√

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
1001

 Ectinosoma abrau is found in the Black and Azov Sea region of eastern Europe (Grigorovich et al. 2003), 

including Lake Ohrid on the Balkan peninsula (Petkovski and Karanovic 1997), which drains into the Adriatic 

Sea, and Lake Balaton.

 Ectinosoma abrau has the potential to be picked up by ships originating in eastern Europe; however it has not 

yet been observed in ships entering the Great Lakes (Grigorovich et al. 2003).

 In Moldova, including the Nistru River reservoirs Cuciurgan and Dubosari, Lake Cahul, Prut and Nistru lakes. 

Central, Western, steppes of Kazakhstan, Kyrgyzstan. (hydrobiologist.wordpress.com/tag/ectinosoma-abrau/)

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.1 8 Low

Total Unknowns (U) 0 Confidence Level High
1002

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Ectinosoma abrau has a low probability of establishment if introduced to the Great Lakes 

(Confidence level: Low).

The native range of Ectinosoma abrau has similar climatic and abiotic conditions to that of the Great 

Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Although it is a marine species, it 

is able tolerate freshwater (Aladin et al. 2008).

There is not enough information on the diet of Ectinosoma abrau, the tolerance of Ectinosoma abrau to 

various environmental conditions, the fecundity of Ectinosoma abrau, and the previous invasion history 

of Ectinosoma abrau to fully predict its establishment to the Great Lakes basin. It is unknown how this 

species will respond to the effects of climate change in the Great Lakes. It is unknown how this species 

will interact with native species in the Great Lakes. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Ectinosoma abrau is from the Black Sea region (Grigorovich et al. 2003).

 The Ponto-Caspian (Caspian, Azov, and Black seas) have similar climate and surface water temperature ranges 

as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6
1003

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

U

 No Information was found on the diet of E. abrau.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 No information was found about the species’ ability to outcompete native species, but as a copepod, it is 

unlikely to pose a major threat.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6
1004

Moderate 3

Low 0

Unknown U

U

 Information on the fecundity of E. abrau was not found. 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Information on this species’ reproductive strategy was not found, but it is unlikely to aid establishment.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?
1005

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions of the native and introduced ranges of E. abrau are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

U

 Little information was found on this subject.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

U

 The adaptability of this species to climate change is unknown.
1006

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

U

 Information on this subject is unknown.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No information on this subject could be found; from that it can be inferred that this species does not require 

other critical species.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

9
1007

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 No information was found on this subject. It is unlikely that the establishment of this species will be aided by 

another species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 No natural predators of this species were found.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3
1008

Infrequent, small or moderate inocula 0

Unknown U

U

 The size and frequency of potential introductions of this species are unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

U

 No previous history of invasion has been found.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

 No information has been found regarding spread via human activities.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

-50% total 

points (at 
1009

to control its establishment and spread) end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no control measures for this species. 

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 42

>100 High Adjustments

B. Critical species A*(1- 0%) 42

51-99 Moderate C. Natural enemy B*(1- 0%) 42

Control measures C*(1- 0%) 42

0-50 Low Potential for Establishment Low

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 8

2-5 Moderate 

6-9 Low

Confidence Level Low

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Ectinosoma abrau if 

introduced to the Great Lakes is inadequate to support proper assessment. 
1010

There is insufficient available information to determine whether Ectinosoma abrau poses a threat to other 

species or water quality. There are no reports that on how it affects or interacts with other species.

There is little or no evidence to support that Ectinosoma abrau has the potential for significant 

socio-economic impact if introduced to the Great Lakes.

It has not been reported that Ectinosoma abrau poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Ectinosoma abrau has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Ectinosoma abrau can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 No information was found on whether E. abrau is a threat to the health of native species.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 Information on species competition was not found.
1011

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Information on predator prey relationships was not found.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 Information on whether or not this species has affected any native population genetically was not found.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 Information about this species’ effect on water quality was not found on this subject.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

6
1012

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 Information about this species’ effect on the physical ecosystem was not found.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 No information on threats posed to human health was found. 

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1
1013

Not significantly 0 √

Unknown U

 No information on damage to infrastructure caused by this species was found.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 No information on this species’ effect on water quality was found.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on commercial markets was found.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on recreational activities was found.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on the natural value or aesthetics of an area was found.
1014

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Information on if it is possible for this species can act as a biological control agent was not found.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 It is not known to be a commercially valuable species.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 6
1015

communities and/or tourism

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 It is not known to be a recreationally valuable species.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 This species is not known to have medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 No information was found on whether this species can improve water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 No information on this species’ ability to have a positive ecological effect was found.

Beneficial Effect Total 0

Total Unknowns (U) 0
1016

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1017

Scientific Name: Heterocope appendiculata 

G.O. Sars, 1863

Common Name: Oarsman, Calanoid Copepod

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Heterocope appendiculata has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

It is predicted that Heterocope appendiculata will be introduced to the Great Lakes via ballast water 

(USEPA 2008, Wonham et al. 2005). Heterocope appendiculata individuals and eggs can be taken up by 

the ballast of both Ballast on Board (BOB) and No Ballast on Board (NOBOB) vessels (Wonham et al. 

2005). Adults produce resting stages that may be able to survive the harsh ballast tank environments. 

Heterocope appendiculata may be introduced to the Great Lakes via ships declaring “No Ballast on 

Board” (NOBOB), which are exempt from ballast water exchange. The majority of ships entering the 

Great Lakes are NOBOB vessels and 43% of these ships contain residual water with less than 10‰ 

salinity (Johengen et al. 2005). In the study, the temperature of the residual water from the vessels 

sampled ranged from -0.7 to 23.9°C; thus, Heterocope appendiculata is likely to survive the salinity and 

temperature of the NOBOB ballast water. Heterocope appendiculata is established in the Baltic Sea 

basin, which contains ports in direct trade with the Great Lakes (NBIC 2009, USEPA 2008). 

Heterocope appendiculata does not currently occur near waters connected to the Great Lakes basin. This 

species is not known to hitchhike or foul recreational gear. It is not cultured, stocked, or sold in the Great 

Lakes region. 
1018

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Although the species Heterocope appendiculata is under high risk for invading the Great Lakes (Grigorovich et 

al. 2003), this organism has not been reported from North America.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 This species is not known to be present in North America. 

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
1019

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 This species is not known to be sold. 

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 This species is a copepod and is not known to be stocked or recreationally cultured.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
1020

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 This species is a copepod and is not known to be commercially cultured or transported in North America.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin. 

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e.

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40 

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Copepods were commonly reported in ballast and predicted to invade new water bodies; although resting eggs 

have been collected frequently from ballast sediments, few have been identified to species (Wonham et al. 

2005).
1021

 Heterocope appendiculata is known to be distributed through ballast water. Vessels may enter the Great Lakes 

carrying residual ballast water and sediment that contain viable organisms (Wonham et al. 2005). 

 This species can be transported by no ballast on board ships, which present a larger risk of ballast-mediated 

invasions due to high trade into the Great Lakes (Grigorovich et al. 2003).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Heterocope appendiculata is widely distributed in the southern part of Norway, in central Sweden, and in 

Finland from the Baltic Sea basin (GBIF 2010, Wesenberg-Lund 1908).

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1022

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Heterocope appendiculata has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

The native and introduced ranges of Heterocope appendiculata have similar climatic and abiotic 

conditions as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Heterocope 

appendiculata inhabits the pelagic and littoral zone of large, deep lakes (Samchyshyna 2008, Walseng et 

al. 2006); there are abundant habitats suitable for this species in the Great Lakes. Heterocope 

appendiculata has a moderately broad physiological tolerance. This species can tolerate a somewhat wide 

range of water temperatures, oxygen levels, and pH. This species occurs in the Baltic Sea, which has a 

salinity range of 1-8 ppt (Reid and Orlova 2002). High nutrient conditions are not favorable for this 

species; 3 years after the fertilization of a lake, its biomass declined considerably (Langeland and 

Reinertsen 1982). Heterocope appendiculata overwinters as resting eggs in sub-arctic lakes (Persson and 

Vrede 2006) and occurs in waters that have temperatures under 5°, so it is somewhat likely that this 

species can overwinter in the Great Lakes. It is unknown if climate change will impact this species’ 

establishment in the Great Lakes. 

Heterocope appendiculata is carnivorous and raptorial. It primarily feeds on protozoa, rotifers, and small 

crustaceans, but feeds on phytoplankton as well (Persson and Vrede 2006); these prey types are available 

in the Great Lakes. Little is known about the competitive abilities and fecundity of Heterocope 

appendiculata. 

This species has established somewhat extensively outside its native range, but its distribution is still 

restricted to central and eastern Europe. Glacial boundaries are thought to delimit the European 

distribution of Heterocope appendiculata (Engman 1994). Heterocope appendiculata is native to the 

Ponto-Caspian basin, and is thought to have spread up the Volga River and to the Baltic Sea basin 

(Slynko et al. 2002). It had spread into the Kuybyshev Reservoir in 1957 and the Oka River after 2000 

(Tockner et al. 2009). The spread of this species may have been facilitated by the impoundment of 

reservoirs. After the impoundment of the Uglich and Ivankova reservoirs, specimens of Heterocope 

appendiculata were collected (Slynko et al. 2002). About 5 years after the impoundment of the Rybinsk 
1023

Reservoir, Heterocope appendiculata and other zooplankton invaders developed large populations. This 

species is now one of the most abundant zooplankton species in the Kama River (Tockner et al. 2009). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Heterocope appendiculata can be found in the Baltic Sea, where the temperature ranges from 0-20°C, which is 

similar to the temperature in the Great Lakes (0.2-25.5°C). The salinity range in the Baltic Sea is 1-8 ppt and < 

0.2 ppt in the Great Lakes (Reid and Orlova 2002). 

 Heterocope appendiculata can survive between 3-23°C, but its optimal temperature tolerance (based on 

maximum abundance) is approximately 17°C (Bertilsson et al. 1995). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Heterocope overwinter as resting eggs in oligotrophic sub-arctic lakes and therefore does not need to store 

fatty acids as energy reserves (Persson and Vrede 2006). 

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6
1024

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 Heterocope are primarily carnivorous raptorial feeders—mainly on protozoa, rotifers, and small crustaceans, 

but phytoplankton may constitute a substantial fraction of their diets (Persson and Vrede 2006).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

 The competitive abilities of H. appendiculata are not known.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 The fecundity of this species is unknown, although in general, copepods reproduce sexually (Engman 1994). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9
1025

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 The reproductive strategy of this species is not known to aid establishment in new environments.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Baltic Sea and the Great Lakes share many similar climate characteristics (Knight 2008). 

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Surface temperature in the Baltic Sea ranges from 0-20°C, which is similar to the surface temperature in the 

Great Lakes (0.2-25.5°C). The salinity ranges in the Baltic Sea range from 1-8 ppt and < 0.2 ppt in the Great 

Lakes (Reid and Orlova 2002). 
1026

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Heterocope appendiculata lives in open water.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

U

 The adaptability of this species to climate change is unknown.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 3
1027

may be considered potential food items—are abundant and/or search time is moderate to 

high)

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 Heterocope mainly feeds on protozoa, rotifers, phytoplankton, and small crustaceans (Persson and Vrede 

2006).

 Heterocope has predatory tendencies and feed on other zooplankton as well as algae. These predators cruise 

through the water, attack their prey with a pounce and grasp them with their first and second maxillae. If the 

capture attempt fails, the copepod may swim into a vertical loop and try again (Thorp and Covich 2001). 

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 Heterocope appendiculata requires no critical species.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6
1028

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 This species is unlikely to be aided by another species. 

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Heterocope appendiculata is unlikely to be prevented from establishment by a natural enemy present in the 

Great Lakes.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 The size and frequency of potential introductions of this species are unknown.
1029

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Nonindigenous species with diapause stages, Heterocope appendiculata was predicted to invade from the 

Ponto-Caspian region (Wonham et al. 2005).

 Heterocope appendiculata was likely to be introduced to the Kuibyshev reservoir in 1957. Although this species’ 

native region was northern Europe, through hydro technical construction, H. appendiculata was also found in 

the Volga and Dnieper reservoirs (Grigorovich et al. 2003). 

 Heterocope appendiculata entered the upper basin of the Volga from downstream. Currently, it is likely to be 

found in the middle Volga. Zooplankton biomass is made up of mostly rotifer from May to June and Crustacea 

from July to September. Heterocope appendiculata is one of the most abundant zooplankters in the Volga, not 

only in near-shore areas but also in the main river channel (Tockner et al. 2009).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

4

 Initially, Heterocope appendiculata was represented by single specimens in the Volga River. In the 

northernmost reservoir (Rybinsk), conditions were more favorable. Between 1946-1948, the regular inflow of 

northern invaders to this body of water allowed for the development of large populations of Heterocope 

appendiculata. These new zooplankton species of northern origins formed the base of a new food chain for 

planktivorous fish (Leppäkoski et al. 2002). 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?
1030

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no control measures for this species. 

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 70

>100 High Adjustments

B. Critical species A*(1- 0%) 70

51-99 Moderate C. Natural enemy B*(1- 0%) 70

Control measures C*(1- 0%) 70

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 4

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low
1031

Current research on the potential for environmental impacts to result from Heterocope 

appenediculata if introduced to the Great Lakes is inadequate to support proper assessment. 

After its introduction to the Volga River basin, Heterocope appendiculata and other non-native 

zooplankton species may have formed the basis of a new food chain for planktivorous fish (Slynko et al. 

2002); however, there is not enough evidence to suggest that Heterocope appendiculata will significantly 

alter the food web if introduced to the Great Lakes. There is insufficient information available to 

determine whether Heterocope appendiculata poses a threat to other species or water quality. There are 

no reports on how it affects or interacts with other species. It is unknown whether this species alters the 

physical components of the ecosystem.

There is little or no evidence to support that Heterocope appendiculata has the potential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Heterocope appendiculata poses a threat to human health or water quality. 

There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational 

activities and associated tourism, or the aesthetic appeal of the areas it inhabits. 

There is little or no evidence to support that Heterocope appendiculata has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Heterocope appendiculata can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Hazardous characteristics of this species are unknown.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 6 
1032

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 The competitive character of this species is unknown.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 The food web influence of this species is unknown. 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 The potential for genetic effects from this species is unknown.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 The ability of this species to affect water quality is unknown.
1033

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 The ability of this species to alter the physical ecosystem is unknown.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U
1034

 There have been no reports of this species affecting human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 There have been no reports of this species causing damage to infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There have been no reports of this species affecting water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There have been no reports of this species affecting commercial markets.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There have been no reports of this species inhibiting recreational activities. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

6
1035

value for future generations

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There have been no reports of this species to having affected the natural values of areas it inhabits.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There have been no reports of this species acting as a control agent.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √
1036

Unknown U

 There have been no reports of this species being commercially valuable.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There have been no reports of this species being recreationally valuable.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 There have been no reports of this species having medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There have been no reports of this species improving water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 
1037

 As part of the new zooplankton community in the Volga, H. appendiculata helped form the base of a new food 

chain for planktivorous fish (Leppäkoski et al. 2002).

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1038

Scientific Name: Heterocope caspia

G.O. Sars 1897

Common Name: Oarsman, Calanoid Copepod

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Heterocope caspia has a modeate probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping

It is predicted that Heterocope caspia will be introduced to the Great Lakes via ballast water (USEPA 

2008, Wonham et al. 2005). Heterocope caspia individuals and eggs can be taken up by the ballast of 

both Ballast on Board (BOB) and No Ballast on Board (NOBOB) vessels (Wonham et al. 2005). Adults 

produce resting stages that may be able to survive the harsh ballast tank environments. Heterocope caspia 

may be introduced to the Great Lakes via ships declaring “No Ballast on Board” (NOBOB), which are 

exempt from ballast water exchange. The majority of ships entering the Great Lakes are NOBOB vessels 

and 43% of these ships contain residual water with less than 10‰ salinity (Johengen et al. 2005). In the 

study, the temperature of the residual water from the vessels sampled ranged from -0.7 to 23.9°C; thus,

Heterocope caspia is likely to survive the salinity and temperature of the NOBOB ballast water on some 

ships. Heterocope caspia is established in the Baltic Sea basin, which contains ports in direct trade with

the Great Lakes (NBIC 2009, USEPA 2008). This species may be introduced to the Great Lakes via the 

Lake Ladoga-Neva estuary-Gulf of Finland corridor, a transoceanic route with ships travelling between 

the Gulf of Finland and the Great Lakes (Berg et al. 2002).

Heterocope caspia does not currently occur near waters connected to the Great Lakes basin. This species 

is not known to hitchhike or foul recreational gear. It is not cultured, stocked, or sold in the Great Lakes 

region. 

POTENTIAL INTRODUCTION VIA DISPERSAL
1039

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Heterocope caspia is not found in North America.

 Heterocope caspia is a Caspian-complex copepod native to the Ponto-Caspian/Black Sea-Azov Sea coast and 

present in reservoirs of the Volga River (Berg et al. 2002, Ketelaars 2004).

 Heterocope caspia is naturalized in both the Kubyshev and Saratov reservoirs of the Volga River (Popov 2011). 

Beyond the Volga water transit zone, H. caspia is absent (Zonn et al. 2009).

 Heterocope caspia is found in the slightly brackish water of the Caspian Sea near the Volga estuary, as well as 

its middle and southern basins; Karabuga Bay, Turkey; and various places in the Asov Sea (Tollinger 1911).

 Heterocope caspia is one of the most widespread zooplankton species in the Don River (Sukhodolov et al. 2009).

 It is characteristic of the Gulf of Taganrog and the Kuchurgan inlet (Zenkevitch 1963).

 Heterocope caspia is present in the Black Sea (Moldoveanu and Timofte 2004) and inland waters of Romania 

(Demeter and Morrone 2009), including the Danube (Dunare/Dunaiskyi) Delta Biosphere Reserve and the 

Kyliiske Mouth and Dnipro River Delta wetlands in Ukraine (Stetsenko et al. 2000). It has been recorded as 

common in southern Ukraine (Samchyshyna 2011), with particularly large summer populations in Lake Cahul

(Naberezhny 1984).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Heterocope caspia is not found in North America, nor is it considered to be a fouling organism.
1040

 Heterocope caspia is a Caspian-complex copepod native to the Ponto-Caspian/Black Sea-Azov Sea coast and 

present in reservoirs of the Volga River (Berg et al. 2002, Ketelaars 2004).

 Heterocope caspia is naturalized in both the Kubyshev and Saratov reservoirs of the Volga River (Popov 2011). 

Beyond the Volga water transit zone, H. caspia is absent (Zonn et al. 2009).

 Heterocope caspia is found in the slightly brackish water of the Caspian Sea near the Volga estuary, as well as 

its middle and southern basins; Karabuga Bay, Turkey; and various places in the Asov Sea (Tollinger 1911).

 Heterocope caspia is one of the most widespread zooplankton species in the Don River (Sukhodolov et al. 2009).

 It is characteristic of the Gulf of Taganrog and the Kuchurgan inlet (Zenkevitch 1963).

 Heterocope caspia is present in the Black Sea (Moldoveanu and Timofte 2004) and inland waters of Romania 

(Demeter and Morrone 2009), including the Danube (Dunare/Dunaiskyi) Delta Biosphere Reserve and the 

Kyliiske Mouth and Dnipro River Delta wetlands in Ukraine (Stetsenko et al. 2000). It has been recorded as 

common in southern Ukraine (Samchyshyna 2011), with particularly large summer populations in Lake Cahul

(Naberezhny 1984).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 This species is not known to be sold.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?
1041

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 This species is not known to be stocked in the Great Lakes region, but it was unsuccessfully introduced to the 

Aral Sea in 1971 as part of efforts to strengthen pelagic trophic links (Aladin et al. 2008b, Plotnikov et al. 2012, 

Zonn et al. 2009).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 There is no known commercial culture of this species in the Great Lakes region.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U
1042

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Heterocope caspia was identified as a candidate species for introduction to the Great Lakes via northward 

spread through the Lake Ladoga-Neva estuary-Gulf of Finland river/reservoir/canal system connecting the 

Ponto-Caspian and Baltic Sea basins; St. Petersburg harbor would be the likeliest source for ballast water 

uptake by Great Lakes-bound freighters (Berg et al. 2002).

 While some reports suggest this species is stenohaline (Zenkevitch 1963), others note it clearly as euryhaline 

(Marsh 1933). Maximum salinity tolerance has been reported at 10.8‰ (Naberezhny 1984). In the Sea of Azov, 

it is present from 1-10‰ (not measured below 1‰) (Zenkevitch 1963).

 Heterocope caspia produces resistant resting (diapausing) stages that are predicted to invade the Great Lakes 

via transport in the sediments of no ballast on board (NOBOB) vessels (Grigorovich et al. 2003, Wonham et al. 

2005). Copepod eggs are frequently found in the sediments of ballast tanks but are less common than those of 

rotifers and cladocerans; however, identification of copepod eggs to species is rare (Wonham et al. 2005). 

Ballast water is therefore predicted to be a more likely pathway of copepod introduction to the Great Lakes, as 

they are more often found there than in ballast sediments (Wonham et al. 2005).

 Copepods tend to be slower growing and more starvation-resistant, and are therefore predicted to remain in 

high abundance even after two weeks in a ballast environment (Wonham et al. 2005).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Heterocope caspia was identified as a candidate species for introduction to the Great Lakes via northward 

spread through the Lake Ladoga-Neva estuary-Gulf of Finland river/reservoir/canal system connecting the 

Ponto-Caspian and Baltic Sea basins; St. Petersburg harbor would be the likeliest source for ballast water 

uptake by Great Lakes-bound freighters (Berg et al. 2002).
1043

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1044

Heterocope caspia has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

The native and introduced ranges of Heterocope caspia have similar climatic and abiotic conditions as the 

Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). Heterocope caspia inhabits 

the pelagic zone above the thermocline in the dimictic part of Caspian lakes (Dumont 1998); there are 

pelagic habitats suitable for this species in the Great Lakes. Heterocope caspia has a moderately broad 

physiological tolerance. This species can tolerate a somewhat wide range of salinity, water temperatures, 

and oxygen levels. Heterocope caspia produces resistant life stages (Grigorovich et al. 2003), so it is 

somewhat likely that this species can overwinter in the Great Lakes. Increased salinization and warmer 

water temperatures due to climate change may make the Great Lakes more habitable for Heterocope 

caspia.

Heterocope caspia is omnivorous. It primarily feeds smaller zooplankton and algae (Kling et al. 1992); 

these prey types are available in the Great Lakes. Little is known about the competitive abilities and 

fecundity of Heterocope caspia. 

This species has established somewhat extensively outside its native range, but its distribution is still 

restricted to central and eastern Europe. Heterocope caspia is native to the Ponto-Caspian basin, and is 

thought to have spread up the Volga River after the construction of locks that removed the natural barriers 

such as rapids (Slynko et al. 2002). Heterocope caspia is numerous in the Kuybyshev reservoir during the 

summer. It has been recorded in the lower and middle Volga (Tockner et al. 2009). This species was 

introduced to the Aral Sea in 1971 in efforts to strengthen pelagic trophic links (Plotnikov et al. 2012). It 

was also unsuccessfully introduced to the Volga foredelta in 1971, and resulted in the introduction of 

Limnomysis brandti and Evande trigona (Zonn et al. 2009).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 While some reports suggest this species is stenohaline (Zenkevitch 1963), others note it clearly as euryhaline 

(Marsh 1933). Maximum salinity tolerance has been reported at 10.8‰ (Naberezhny 1984). In the Sea of Azov, 

it is present from 1-10‰ (not measured below 1‰) (Zenkevitch 1963).

 It is found both in fresh and salt water, and some consider it to have originally been a saltwater form that 

gradually adapted to a freshwater environment (Marsh 1933).

 Copepods tend to be slower growing and starvation-resistant (Wonham et al. 2005).

 Heterocope caspia was found at depths ranging from 20-60 m in the Shah Deniz gas field off the Aspheron 

Peninsula (Caspian Sea), but only comprised roughly 0.2% of the copepod biomass (ERT 2000). Nutrients 
1045

concentrations at these sites included 0.1 mg/l nitrite, <2-4.5 mg/l nitrate, <1.0 mg/l ammonia, and <0.05 mg/l 

phosphate, while pH was between 7.9-8.2, dissolved oxygen between 11.6-14.3 mg/l, turbidity between 0-1 

NTU, salinity roughly 12 ppt, and temperature 12.3-22.7 ̊C (ERT 2000).

 Heterocope caspia is a thermophilic stenothermic species, active only during the warmer parts of the year; as 

such, it forms diapausing eggs to survive through the winter (Samchyshyna 2008).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Heterocope caspia is a thermophilic stenothermic species, active only during the warmer parts of the year; as 

such, it forms diapausing eggs to survive through the winter (Samchyshyna 2008).

 Heterocope caspia is present in the Kyliiske Mouth wetland of Ukraine, where average turbidity levels are 325 

g/m3(Stoilovskyi and Kivganov 1998).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 Heterocope caspia is both a predator and a suspension feeder (Popov 2012).

 As with a few other Heterocope species, the diet of H. caspia may shift under variable trophic conditions, and 

include algae, bacteria, detritus, cladoceran neonats, nauplii, copepodites, protozoans, and rotifers 

(Samchyshyna 2008).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 6
1046

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

 The competitive abilities of H. caspia are not known. However, it is often found in high abundances and is 

reported to be one of most important components of the summer zooplankton; in reservoirs of the Volga River, 

it occurs in average densities of 800 individuals/m3from May to September, peaking from July to August with 

up to 4000 individuals/m3(Popov 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 The fecundity of H. caspia is not known.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

2

 Heterocope caspia eggs, unlike in other species of this genus, hatch in egg sacs instead of in the water column 

(Naberezhny 1984).
1047

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Heterocope caspia is a Caspian-complex copepod native to the Ponto-Caspian/Black Sea-Azov Sea coast and 

present in reservoirs of the Volga River (Berg et al. 2002, Ketelaars 2004).

o The Caspian Sea consists of three basins, with salinities ranging from 0.1‰ in the northern basin 

to 10-13‰ in the middle and southern basins (CEP 2004). Summer temperatures vary by 1-2 ̊C 

among the basins (24-28 ̊C); however, in winter, the northern basin freezes (0-0.5 ̊C surface 

water), while the southern basin remains 10-11 ̊C (CEP 2004, Shiganova et al. 2004).

 Heterocope caspia is one of the most widespread zooplankton species in the Don River (Sukhodolov et al. 2009).

o The Don experiences a period of stable air temperatures <0 ̊C that lasts up to 110 days in the 

northern catchment but only 30 days in the southwest. Mean temperatures in January decrease 

from southwest to northeast from -2 ̊C to -12 ̊C, and with a minimum of -44 ̊C. Snow cover usually 

appears in early November (averaging ~30 cm deep) in the north and late December (averaging 

~5–10 cm) in the southwest. Spring air temperatures range between 4 and 15 ̊C for 40–50 days in 

the north and 60–70 days in the southwest. Summer is hot and dry, beginning in mid-May for 140 

days in the south and late May for 100 days in the northeast. The mean temperature in July 

reaches 20 ̊C in the northeast and 25–30 ̊C in the south, and with a maximum of 45 ̊C. Autumn 

typically lasts for 60–70 days with gradual decreases in mean air temperature from 15 to 0 ̊C.

 Heterocope caspia is present in the Black Sea (Moldoveanu and Timofte 2004) and inland waters of Romania 

(Demeter and Morrone 2009), including the Danube (Dunare/Dunaiskyi) Delta Biosphere Reserve and the 

Kyliiske Mouth and Dnipro River Delta wetlands in Ukraine (Stetsenko et al. 2000).

o The Dnipro River Delta has a temperate continental climate that is droughty with a hot summer 

with rainstorms and a short, mild winter. Annual snow cover fluctuates from 0 to 40 days with 

frequent thaws. The period without frost is 180–210 days, and the average monthly temperature

fluctuates from -2.5°C to 20°C (Stetsenko et al. 2000).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0
1048

Unknown U

8

 Heterocope caspia is found in the slightly brackish water of the Caspian Sea near the Volga estuary, as well as 

its middle and southern basins; Karabuga Bay, Turkey; and various places in the Asov Sea (Tollinger 1911).

 The Caspian Sea consists of three basins, with salinities ranging from 0.1‰ in the northern basin to 10-13‰ in 

the middle and southern basins (CEP 2004). Summer temperatures vary by 1-2 ̊C among the basins (24-28 ̊C); 

however, in winter, the northern basin freezes (0-0.5 ̊C surface water), while the southern basin remains 10-

11 ̊C (CEP 2004, Shiganova et al. 2004). Salinity ranges from 0.1‰ near the Volga and Ural River mouths to 

10-11‰ near the Middle Caspian boundary, increasing to 13‰ in the southern basin (Shiganova et al. 2004).

 Heterocope caspia biomass in the Sea of Azov is at its peak (~200 mg/m3) between 2 and 3‰ salinity, but is 

present from 1-10‰ (not measured below 1‰) (Zenkevitch 1963).

 Heterocope caspia is suggested by some to be more stenohaline than other northern Caspian copepods, 

avoiding both increases and decreases in salinity (Zenkevitch 1963), but others consider it to be euryhaline and 

originally a saltwater species that gradually adapted to a freshwater environment (Marsh 1933). As a PontoCaspian species, H. caspia develops optimally in brackish waters, but has successfully migrated into fresh 

waters (Samchyshyna 2008).

 Heterocope caspia is characteristic of the Gulf of Taganrog and the Kuchurgan inlet, which is characterized by 

very low salinity (0.5-2‰) (Zenkevitch 1963).

 Heterocope caspia was found at depths ranging from 20-60 m in the Shah Deniz gas field off the Aspheron 

Peninsula (Caspian Sea), but only comprised roughly 0.2% of the copepod biomass (ERT 2000). Nutrients 

concentrations at these sites included 0.1 mg/l nitrite, <2-4.5 mg/l nitrate, <1.0 mg/l ammonia, and <0.05 mg/l 

phosphate, while pH was between 7.9-8.2, dissolved oxygen between 11.6-14.3 mg/l, turbidity between 0-1 

NTU, salinity roughly 12 ppt, and temperature 12.3-22.7 ̊C (ERT 2000).

 Heterocope caspia is present in the Kyliiske Mouth wetland of Ukraine (Stoilovskyi and Kivganov 1998). The 

Kyliiske Mouth wetland is characterized by average mineralization, oxygen within the limits of normal 

saturation (though sometimes deficient in winter and in abundance in summer), average turbidity of 325 g/m3, 

and sharp salinity (typically 1.8‰) and temperature fluctuations, particularly in the near-mouth areas 

(Stoilovskyi and Kivganov 1998).

 Low pH appears to be a limiting factor for calanoid copepods, but further research is needed (Samchyshyna 

2008).

 In general, calanoid copepods of Ukraine’s inland waters (e.g., along the Azov and Black Sea coasts) exhibit 

wide ecological plasticity (Samchyshyna 2008).

 Heterocope caspia is one of the most widespread zooplankton species in the Don River, a river characterized as 

being mildly to heavily polluted (Sukhodolov et al. 2009).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Heterocope caspia is a pelagic, open water species. As such, habitats in the Great Lakes are likely to be 

abundant.
1049

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 As a euryhaline species, increased salinity (to a point) is not likely to pose a difficulty for H. caspia. However, 

H. caspia was unsuccessfully introduced to the Aral Sea in 1971 as part of efforts to introduce species able to 

survive that lake’s ever increasing salinity (Aladin et al. 2008b, Plotnikov et al. 2012, Zonn et al. 2009).

 In general, calanoid copepods of Ukraine’s inland waters (e.g., along the Azov and Black Sea coasts) exhibit 

wide ecological plasticity (Samchyshyna 2008).

 Warmer temperatures are also likely to favor H. caspia, as it active only during the warmer parts of the year 

(Samchyshyna 2008).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 As both a predator and a suspension feeder (Popov 2012), the diet of H. caspia may shift under variable trophic 

conditions, and include algae, bacteria, detritus, cladoceran neonats, nauplii, copepodites, protozoans, and 

rotifers (Samchyshyna 2008). This diet should be easily satisfied in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?
1050

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No critical species is required by H. caspia.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is no species likely to facilitate the establishment of spread of H. caspia in the Great Lakes.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

-80% total 

points (at 

end)
1051

Great Lakes)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Adult calanoid copepods are preyed upon by age-1 freshwater, marine, and semi-anadromous fishes in 

Ukraine’s nursery ponds, while juveniles and eggs form an important component of the diets of carnivorous 

cladocerans, cyclopoid copepods, mosquito larvae, and comb jellies (ctenophores) (Samchyshyna 2008).

 Heterocope caspia is a main food item for kilka fish in the Caspian Sea, but this copepod population has sharply 

declined (and in some cases may be locally extinct) due to predation by the invasive Mnemiopsis leidyi comb 

jelly (Shiganova et al. 2004).

 However, in the Great Lakes, there is unlikely to be a predator that preferentially targets this species.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 Copepod eggs are frequently found in the sediments of ballast tanks but are less common than those of rotifers 

and cladocerans; however, identification of copepod eggs to species is rare (Wonham et al. 2005). As such, the 

propagule pressure of this species is unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

3
1052

proximity to each other)

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 Heterocope caspia is recognized as an alien species in Europe outside of its native range. It is thought to have 

extended its range to Volga and Dnieper reservoirs via shipping traffic associated with 1960s and 1970s 

waterway construction projects which provided new habitats and promoted dispersal along a northern 

migration corridor; it was first found in the Kremenchug reservoir (of Dnieper) in 1962 (Grigorovich et al. 

2003, Ketelaars 2004).

 Heterocope caspia is naturalized in both the Kubyshev and Saratov reservoirs of the Volga River (Popov 2011). 

Beyond the Volga water transit zone, H. caspia is absent (Zonn et al. 2009).

 Heterocope caspia was identified as a candidate species for introduction to the Great Lakes via northward 

spread through the Lake Ladoga-Neva estuary-Gulf of Finland river/reservoir/canal system connecting the 

Ponto-Caspian and Baltic Sea basins (Berg et al. 2002).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 Heterocope caspia is recognized as an alien species in Europe outside of its native range. It is thought to have 

extended its range to Volga and Dnieper reservoirs via shipping traffic associated with 1960s and 1970s 

waterway construction projects which provided new habitats and promoted dispersal along a northern 

migration corridor; it was first found in the Kremenchug reservoir (of Dnieper) in 1962 (Grigorovich et al. 

2003, Ketelaars 2004).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this species 0
1053

Unknown U

0

 There are no control measures for this species.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 87

>100 High Adjustments

B. Critical species A*(1- 0%) 87

51-99 Moderate C. Natural enemy B*(1- 0%) 87

Control measures C*(1- 0%) 87

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Heterocope caspia if 

introduced to the Great Lakes is inadequate to support proper assessment. 

There is insufficient information available to determine whether Heterocope caspia poses a threat to other 

species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Heterocope caspia has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.
1054

It has not been reported that Heterocope caspia poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits. 

There is little or no evidence to support that Heterocope caspia has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

Heterocope caspia could potentially contribute as a food source for planktivorous fish, but it is unknown 

if they would be beneficial to species in the Great Lakes. It has not been indicated that Heterocope caspia 

can be used for the control of other organisms or improving water quality. There is no evidence to suggest 

that this species is commercially, recreationally, or medically valuable. It does not have significant 

positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Hazards to the health of native species associated with H. caspia are unknown.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 This species’ competitive characteristics have not been described.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

6
1055

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Adult calanoid copepods are preyed upon by age-1 freshwater, marine, and semi-anadromous fishes in 

Ukraine’s nursery ponds, while juveniles and eggs form an important component of the diets of carnivorous 

cladocerans, cyclopoid copepods, mosquito larvae, and comb jellies (ctenophores) (Samchyshyna 2008).

 The effect of this on trophic relationships within the food web is not known.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 The potential for genetic effects from this species is unknown.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 The influence of this species on water quality is unknown.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 1 
1056

adverse effects have been mild

Not significantly 0 

Unknown U √

 The influence of this species on the physical ecosystem is unknown.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There have been no reports of this species affecting human health.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U
1057

 There have been no reports of this species causing damage to infrastructure.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There have been no reports of this species affecting water quality.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 There have been no reports of this species affecting commercial markets.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There have been no reports of this species inhibiting recreational activities. 

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 There have been no reports of this species to having affected the natural values of areas it inhabits.

Socio-Economic Impact Total 0

Total Unknowns (U) 0
1058

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There have been no reports of this species acting as a control agent.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 There have been no reports of this species being commercially valuable

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √
1059

Unknown U

 There have been no reports of this species being recreationally valuable.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 There have been no reports of this species having medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 There have been no reports of this species improving water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 

 This species could potentially contribute to another food source in the food web since the majority of freshwater 

fish eat copepods.

 While unsuccessful, H. caspia was attempted to be introduced to the Aral Sea in 1971 as part of efforts to 

strengthen pelagic trophic links (Aladin et al. 2008b, Plotnikov et al. 2012, Zonn et al. 2009).

 Adult calanoid copepods are preyed upon by age-1 freshwater, marine, and semi-anadromous fishes in 

Ukraine’s nursery ponds, while juveniles and eggs form an important component of the diets of carnivorous 

cladocerans, cyclopoid copepods, mosquito larvae, and comb jellies (ctenophores) (Samchyshyna 2008).

 Heterocope caspia is a main food item for kilka fish in the Caspian Sea (Shiganova et al. 2004).

 Copepod larvae, including that of H. caspia, have been recorded as playing a major role in the summer 

zooplankton community in the Sea of Azov, making up to 42% of the zooplankton biomass in June, with smaller 

numbers in the Gulf of Taganrog (Zenkevitch 1963).
1060

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1061

Scientific Name: Paraleptastacus spinicaudus triseta

Noodt, 1954

Common Name: Oarsman, Harpacticoid Copepod

Synonyms: Paraleptastacus spinicaudata triseta, Paraleptastacus spinicauda triseta

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Paraleptastacus spinicaudus triseta has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

It is predicted that Paraleptastacus spinicaudus triseta will be introduced to the Great Lakes via ballast 

water (USEPA 2008, Wonham et al. 2005). Paraleptastacus spinicaudus triseta may be introduced to the 

Great Lakes via ships declaring “No Ballast on Board” (NOBOB) (Grigorovich et al. 2003), which are 

exempt from ballast water exchange. The majority of ships entering the Great Lakes are NOBOB vessels 

and 43% of these ships contain residual water with less than 10‰ salinity (Johengen et al. 2005). In the 

study, the temperature of the residual water from the vessels sampled ranged from -0.7 to 23.9°C; thus, 

Paraleptastacus spinicaudus triseta is likely to survive the salinity and temperature of the NOBOB 

ballast water of some ships. Adults are able to enter diapause and may survive anoxic ballast 

environments (Grigorovich et al. 2003). Paraleptastacus spinicaudus has been recorded in drifting algae 

collected in the Baltic Sea (Arroyo et al. 2006), a water body with ports in direct trade with the Great 

Lakes (NBIC 2009, USEPA 2008). 

Paraleptastacus spinicaudus does not currently occur near waters connected to the Great Lakes basin. 

This species is not known to hitchhike or foul recreational gear. It is not cultured, stocked, or sold in the 

Great Lakes region. 
1062

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Paraleptastacus spinicaudus triseta is from the Ponto-Caspian region of eastern Europe.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Paraleptastacus spinicaudus triseta is found in eastern Europe 

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
1063

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 This species is not known to be sold. 

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 This species is not known to be stocked or recreationally cultured.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
1064

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 This species is not known to be commercially cultured or transported in North America.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 This species is listed as being capable of survival in no-ballast-on-board ships (Grigorovich et al. 2003).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?
1065

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species has the potential to be picked up by ships originating in eastern Europe; however it has not yet 

been observed in ships entering the Great Lakes (Grigorovich et al. 2003).

 This species has been recorded in Loch Fyne, along the western coast of Ireland (Nicholls 1935).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1066

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Paraleptastacus spinicaudus triseta has a low probability of establishment if introduced to the Great 

Lakes (Confidence level: Low).

The native and introduced ranges of Paraleptastacus spinicaudus triseta have similar climatic and abiotic 

conditions as the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). 

Paraleptastacus spinicaudus primarily inhabits sand and sediments of coastal marine and estuarine 

environments, but it has been introduced to inland fresh waters before (Alexandrov et al. 2007); there are 

habitats available for this species in the Great Lakes region. Paraleptastacus spinicaudus has a 

moderately broad physiological tolerance. This species can tolerate a somewhat wide range of salinity, 

water temperatures, and oxygen levels. As a coastal marine and estuarine organism, increased salinization 

and warmer water temperatures due to climate change may make the Great Lakes more habitable for P. 

spinicaudus.

Paraleptastacus spinicaudus feeds on bacteria (Cnudde 2013), so it is likely that this species will find an 

appropriate food source in the Great Lakes. Little is known about the competitive abilities and fecundity 

of P. spinicaudus. 

This species has established extensively outside its native range, and occurs through much of Europe and 

on the coasts of British Columbia. The rate of its spread is unknown. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3
1067

Unknown U

6

 Paraleptastacus spinicaudus triseta is predicted to be able to survive in the Great Lakes region (Grigorovich et 

al. 2003).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

U

 No information was found on the diet of P. spinicaudus triseta. 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 0
1068

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

Unknown U

3

 No information was found about the species’ ability to outcompete native species, but as a copepod, it is 

unlikely to pose a major threat.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 Information on the fecundity of P. spinicaudus triseta was not found.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

 Information on this species’ reproductive strategy was not found, but it is unlikely to aid establishment.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9
1069

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Grigorovich et al. (2003) stated that conditions were similar enough to allow survival in the Great Lakes.

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

U

 Little information was found on this subject.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?
1070

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

U

 The adaptability of this species to climate change is unknown.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

U

 Information on this subject is unknown.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3
1071

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No information on this subject could be found; from that it can be inferred that this species does not require 

other critical species.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 No information was found on this subject. It is unlikely that the establishment of this species will be aided by 

another species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)
1072

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 No natural predators of this species were found.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 The size and frequency of potential introductions of this species are unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

U

 No previous history of invasion has been found.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6
1073

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

 No information has been found regarding spread via human activities.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no control measures for this species. 

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 42

>100 High Adjustments

B. Critical species A*(1- 0%) 42

51-99 Moderate C. Natural enemy B*(1- 0%) 42

Control measures C*(1- 0%) 42

0-50 Low Potential for Establishment Low

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 8

2-5 Moderate 

6-9 Low

Confidence Level Low

>9 Very low
1074

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Paraleptastacus 

spinicaudus triseta if introduced to the Great Lakes is inadequate to support proper assessment. 

There is insufficient information available to determine whether Paraleptastacus spinicaudus triseta 

poses a threat to other species or water quality. There are no reports on how it affects or interacts with 

other species. It is unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Paraleptastacus spinicaudus triseta has thepotential for 

significant socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Paraleptastacus spinicaudus triseta poses a threat to human health or water 

quality. There is no evidence that this species negatively impacts infrastructure, economic sectors, 

recreational activities and associated tourism, or the aesthetic appeal of the areas it inhabits. 

There is little or no evidence to support that Paraleptastacus spinicaudus has the potential for 

significant beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Paraleptastacus spinicaudus can be used for the control of other organisms 

or improving water quality. There is no evidence to suggest that this species is commercially, 

recreationally, or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 No information was found on whether P. spinicaudus triseta is a threat to the health of native species.
1075

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 Information on species competition was not found.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Information on predator prey relationships was not found.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 Information on whether or not this species has affected any native population genetically was not found.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 1 
1076

effects have been limited or inconsistent (as compared with above statement)

Not significantly 0 

Unknown U √

 Information about this species’ effect on water quality was not found on this subject.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 Information about this species’ effect on the physical ecosystem was not found.

Environmental Impact Total 0

Total Unknowns (U) 6

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?
1077

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 No information on threats posed to human health was found. 

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

 No information on damage to infrastructure caused by this species was found.

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 No information on this species’ effect on water quality was found.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on commercial markets was found.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on recreational activities was found.
1078

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

 No information on this species’ effect on the natural value or aesthetics of an area was found.

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Information on if it is possible for this species can act as a biological control agent was not found.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 
1079

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

 It is not known to be a commercially valuable species.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 It is not known to be a recreationally valuable species.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 This species is not known to have medicinal or research value.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 No information was found on whether this species can improve water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 
1080

Not significantly 0 √

Unknown U 

 No information on this species’ ability to have a positive ecological effect was found.

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1081

A.7 Crustaceans - Mysids

Scientific Name: Limnomysis benedeni

Czerniavsky, 1882

Common Name: Caspian Slender Mysid, Danube Mysid, Pontian Mysid

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate 

Limnomysis benedeni has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Ricciardi and Rasmussen (1998) listed this species among five Ponto-Caspian mysids that, due to their 

salinity tolerance, are likely to be transported to the Great Lakes via ballast water. The related Hemimysis 

anomala fulfilled this prediction in 2006 (Pothoven et al. 2007). Grigorovich et al. (2003), however, 

identified L. benedeni as having a reduced probability of invasion due to the effects of ballast water 

exchange or flushing, while they classified H. anomala as having a greater likelihood of introduction.

This species is currently widespread throughout the entire North Sea basin (lower Rhine River), Baltic 

Sea basin, and Black-Azov Sea basin (bij de Vaate et al. 2002, Grigorovich et al. 2003), all of which 

sustain heavy amounts of Great Lakes shipping traffic.

Ovcarenko et al. (2006) reported that L. benedeni was largely unaffected by salinity increases up to 19 

PSU and showed only about 25% mortality when exposed to 23 PSU for 24 hours. It was not until 24 

hours of exposure to 34 PSU that a 100% mortality rate was observed. This high salinity tolerance was 

confirmed by Santagata et al. (2008), who reported 60+14% and 55+13% (mean + s.d.) survival rates for 

freshwater individuals exposed to full-strength (34 PSU) seawater for 48 hours in flow-through and 

empty-refill treatments, respectively. These results provide evidence that current ballast water control 

measures may not be completely effective in preventing the introduction of this species to the Great 

Lakes.
1082

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
1083

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
1084

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Ricciardi and Rasmussen (1998) listed this species among five Ponto-Caspian mysids that, due to their salinity 

tolerance, are likely to be transported to the Great Lakes via ballast water. The related Hemimysis anomala

fulfilled this prediction in 2006 (Pothoven et al. 2007).

 Grigorovich et al. (2003), however, identified L. benedeni as having a reduced probability of invasion due to 

the effects of ballast water exchange or flushing, while they classified H. anomala as having a greater likelihood 

of introduction.
1085

 Ovcarenko et al. (2006) reported that L. benedeni was largely unaffected by salinity increases up to 19 PSU 

and showed only about 25% mortality when exposed to 23 PSU for 24 hours. It was not until 24 hours of 

exposure to 34 PSU that a 100% mortality rate was observed.

 This high salinity tolerance was confirmed by Santagata et al. (2008), who reported 60+14% and 55+13% 

(mean + s.d.) survival rates for freshwater individuals exposed to full-strength (34 PSU) seawater for 48 hours 

in flow-through and empty-refill treatments, respectively. These results provide evidence that current ballast 

water control measures may not be completely effective in preventing the introduction of this species to the 

Great Lakes.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species is currently widespread throughout the entire North Sea basin (lower Rhine River), Baltic Sea 

basin, and Black-Azov Sea basin, all of which sustain heavy amounts of Great Lakes shipping traffic (bij de 

Vaate et al. 2002, Grigorovich et al. 2003, Wittmann 2009).
1086

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1087

Limnomysis benedeni has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

This species is able to survive in a relatively wide range of temperature (0-31°C) and salinity (0-14 ppt), 

though its minimum dissolved oxygen requirement (3.75 mg/L) is higher than that of many other 

freshwater invertebrates (Wittmann 2009). Limnomysis benedeni is able to tolerate a relatively wide range 

of pH (5.5-9.6), though it prefers slightly alkaline conditions (Wittmann 2009). All five Lakes would 

likely serve as suitable habitat under these physiological requirements; however, due to the relatively high 

oxygen demands, it may be restricted from establishing populations in portions of Lake Erie that undergo 

anoxic conditions. This species produces an overwintering generation in autumn that is able to survive in 

0°C waters until the following spring (Wittmann 2009), making it a likely candidate to overwinter in the 

Great Lakes. It is possible that this relatively high oxygen demand may interfere with its ability to 

overwinter in the Great Lakes.

This species is classified as an omnivore-herbivore (Gergs et al. 2008), with a non-specific food 

preference (bij de Vaate et al. 2002). None of its food sources are limiting within the Great Lakes. While 

L. benedeni contributes significantly to the diets of various fish species, including perch (Bacescu 1940,

Bacescu 1954, Hanselmann et al. 2011, Kelleher et al. 1999, Mordukhaĭ-Boltovskoĭ 1979b, Zhadin and 

Gerd 1961, Zhuravel 1956), the extent to which this predation will have an effect on preventing the 

establishment of potential populations in the Great Lakes is unknown.

Limnomysis benedeni has a history of outcompeting other species within its exotic range. Olenin et al. 

(2007) assessed the invasion effect of this species in the Curonian Lagoon as causing a moderate decline 

in abundance and reduction in range of native species. If it succeeds in invading fresh and brackish water 

Mediterranean tributaries, it has been predicted to outcompete the closely related genus Diamysis

(Wittmann and Ariani 2000). Additionally, a loss of native macroinvertebrate species in the upper Rhine 

was noticed after the appearance of L. benedeni (Bernauer and Jansen 2006). 

This species is classified as having a high fecundity (bij de Vaate et al. 2002). This, together with 

iteroparity and multiple generations per year give L. benedeni a high reproductive potential and increase 

its competitive ability. A single female with fertilized eggs or larvae in the brood pouch may be sufficient 

for founding a new population (Wittmann 2009).

Climatic conditions throughout the native range of this species are very similar to those experienced by 

the Great Lakes–a continental climate with dry summers (warm average temperatures > 10°C, coldest 

month < 0°C) (Wittmann 2009). Limnomysis benedeni prefers current velocities less than 0.5 m/s 

(Wittmann 1995), making most of the Great Lakes suitable habitat with respect to water motion. 

Increased salinization as a result of climate change (Rahel and Olden 2008) will likely give this species a 

competitive advantage over the only Great Lakes native mysid, Mysis diluviana (salinity tolerance 0-3 

ppt) (Audzijonytė and Väinölä 2005, Ricciardi et al. 2011), as it is tolerant of salinities up to 14 ppt. 

Shorter ice cover duration and warmer water temperatures may also benefit this species by lengthening 

the suitable yearly breeding period.

Limnomysis benedeni has spread extensively throughout European waterways as a result of both 

intentional and unintentional introductions. Following a large number of stocking events in the Soviet 

Union beginning in 1947 and extending through the 1960s, this species became established in the Dnieper 

River (Ukraine), Lake Balaton (Hungary), and the Kaunas Reservoir (Lithuania). Genetic data suggest 

that this species colonized Western Europe along the southern invasion corridor from the Danube Delta, 

via the Main-Danube Canal, and River Rhine down to the North Sea (Audzijonytė et al. 2009). As 

harbors throughout Europe often mark the extent this species is distributed, shipping appears to be the 
1088

main vector of dispersal (Wittmann 1995, Wittmann 2007), with construction and widening of canals 

contributing to its rapid spread across large distances (Wittmann 2009).

Overland transfers may also play a significant role in the spread of this species, as it has recently been 

found in poorly accessible water bodies in Europe (Fritz et al. 2006, Iftime and Tatole 2006, Wittmann et 

al. 1999, Wittmann and Ariani 2009). Proposed mechanisms of this dispersal mode include inadvertent 

stocking with aquatic plants or commercially valuable animals (Dumont 2006, Iftime and Tatole 2006, 

van der Velde et al. 2000), the aquarium trade, and overland boat transport (Wittmann and Ariani 2009). 

Prior to human-mediated transport, observations suggest that active swimming and passive drift along 

waterways were once its only means of spread (Bacescu 1940, Behning 1938). Extrapolations from its 

range extensions in the 1990s and 2000s suggest that eventually L. benedeni will be present in all major 

river systems of the European subcontinent that have appropriate environmental conditions (Wittmann 

2009).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 This species is able to survive in a relatively wide range of temperature (0-31°C) and salinity (0-14 ppt), though 

its minimum dissolved oxygen requirement (3.75 mg/L) is higher than that of many other freshwater 

invertebrates (Wittmann 2009).

 It is able to tolerate a relatively wide range of pH (5.5-9.6), though it prefers slightly alkaline conditions 

(Wittmann 2009).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 mg/L) 9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8
1089

 This species produces an overwintering generation in autumn that is able to survive in 0°C waters until the 

following spring (Wittmann 2009).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Limnomysis benedeni is primarily microphagous, with a diet consisting of phytoplankton, epilithon, detritus, 

and biofilms on macrophytes, while animal prey (chironomids, etc.) play only a minor role (Dediu 1966, Gergs 

et al. 2008, Wittmann 2002, Wittmann and Ariani 2000).This species is classified as an omnivore-herbivore 

(Gergs et al. 2008), with a non-specific food preference (bij de Vaate et al. 2002). 

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 Olenin et al. (2007) assessed the invasion effect of this species in the Curonian Lagoon as causing a moderate 

decline in abundance and reduction in range of native species.

 If it succeeds in invading fresh and brackish water Mediterranean tributaries, it has been predicted to 

outcompete the closely related genus Diamysis (Wittmann and Ariani 2000). A loss of native macroinvertebrate 

species in the upper Rhine was noticed after the appearance of L. benedeni (Bernauer and Jansen 2006).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9
1090

High 6

Moderate 3

Low 0

Unknown U

6

 This species is classified as having a high fecundity by bij de Vaate et al. (2002) and Wittmann (2009).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

9

 High fecundity, together with iteroparity and multiple generations per year, give L. benedeni a high 

reproductive potential. A single female with fertilized eggs or larvae in the brood pouch may be sufficient for 

founding a new population (Wittmann 2009).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Climatic conditions throughout the native range of this species are very similar to those experienced by the 

Great Lakes–a continental climate with dry summers (warm average temperatures > 10°C, coldest month < 

0°C) (Wittmann 2009). 
1091

 The Great Lakes and Ponto-Caspian region are “climatically compatible,” which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 The temperature (0-31°C), pH (5.5-9.6), and salinity (0-14 ppt) ranges tolerated by this species (see Ecology) 

are all within the ranges occurring in the Great Lakes.

 Limnomysis benedeni prefers current velocities less than 0.5 m/s (Wittmann 1995), making most of the Great 

Lakes suitable habitat with respect to water motion.

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 All five Great Lakes would likely serve as suitable habitat under physiological requirements; however, due to 

the relatively high oxygen demands, this species may be restricted from establishing populations in portions of 

Lake Erie that undergo anoxic conditions.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

9
1092

changes due to its wide environmental tolerances)

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Increased salinization as a result of climate change (Rahel and Olden 2008) will likely give this species a 

competitive advantage over the only Great Lakes native mysid, Mysis diluviana (salinity tolerance 0-3 ppt) 

(Audzijonytė and Väinölä 2005, Ricciardi et al. 2011), as it is tolerant of salinities up to 14 ppt. Shorter ice 

cover duration and warmer water temperatures may also benefit this species by lengthening the suitable yearly 

breeding period.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Limnomysis benedeni is primarily microphagous, with a diet consisting of phytoplankton, epilithon, detritus, 

biofilms on macrophytes, and occasionally animal prey (chironomids, etc.) (Dediu 1966, Gergs et al. 2008, 

Wittmann 2002, Wittmann and Ariani 2000). None of these food sources are limiting within the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 3
1093

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by L. benedeni.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)
1094

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

 While L. benedeni contributes significantly to the diets of various fish species, including perch (Bacescu 1940,

Bacescu 1954, Hanselmann et al. 2011, Kelleher et al. 1999, Mordukhaĭ-Boltovskoĭ 1979b, Zhadin and Gerd 

1961, Zhuravel 1956), the extent to which this predation will have an effect on potential populations in the 

Great Lakes is unknown.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Limnomysis benedeni has spread extensively throughout European waterways as a result of both intentional 

and unintentional introductions. Following a large number of stocking events in the Soviet Union beginning in 

1947 and extending through the 1960s, this species became established in the Dnieper River (Ukraine), Lake 

Balaton (Hungary), and the Kaunas Reservoir (Lithuania). Genetic data suggest that this species colonized 

Western Europe along the southern invasion corridor from the Danube Delta, via the Main-Danube Canal, and 

River Rhine down to the North Sea (Audzijonytė et al. 2009). As harbors throughout Europe often mark the 

extent this species is distributed, shipping appears to be the main vector of dispersal (Wittmann 1995, Wittmann

2007), with construction and widening of canals contributing to its rapid spread across large distances 
1095

(Wittmann 2009).Overland transfers may also play a significant role in the spread of this species, as it has 

recently been found in poorly accessible water bodies in Europe (Fritz et al. 2006, Iftime and Tatole 2006, 

Wittmann et al. 1999, Wittmann and Ariani 2009). Proposed mechanisms of this dispersal mode include 

inadvertent stocking with aquatic plants or commercially valuable animals (Dumont 2006, Iftime and Tatole 

2006, van der Velde et al. 2000), the aquarium trade, and overland boat transport (Wittmann and Ariani 2009). 

Prior to human-mediated transport, data suggest that active swimming and passive drift along waterways were 

once its only means of spread (Bacescu 1940, Behning 1938).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 Extrapolations from its range extensions in the 1990s and 2000s suggest that eventually L. benedeni will be 

present in all major river systems of the European subcontinent that have appropriate environmental conditions 

(Wittmann 2009).

 With shipping as its main vector of dispersal, large distances can be crossed rapidly (Wittmann 2009).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for A. Total Points (pre-adjustment) 116
1096

Establishment

>100 High Adjustments

B. Critical species A*(1- 0%) 116

51-99 Moderate C. Natural enemy B*(1- 0%) 116

Control measures C*(1- 0%) 116

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

Limnomysis benedeni has the potential for moderate environmental impact if introduced to the 

Great Lakes.

The effect of L. benedeni invasion in the Curonian Lagoon has been a moderate decline in abundance and 

reduction in range of native species (Olenin et al. 2007). Bernauer and Jansen (2006) noted a loss of 

native macroinvertebrate species in the upper Rhine River, Germany after the appearance of a number of 

invasive macroinvertebrates, including L. benedeni. Additionally, this species may have altered the 

freshwater food web in Switzerland (Gauer and Imesch 2008). Its impact on ecosystem functioning has 

been classified as moderate (i.e. weak modification of ecosystem performance and/or addition of a new, 

or reduction of existing, functional groups) (Olenin et al. 2007). It is predicted to outcompete the closely 

related genus Diamysis if it succeeds in invading fresh and brackish water Mediterranean tributaries 

(Wittmann and Ariani 2000).

The non-native population of L. benedeni in the strongly eutrophic Curonian Lagoon is reported to be a 

biomass dominant component of the nektobenthic community, with major significance in modifying 

sediment/habitat by pelletization (Olenin and Leppäkoski 1999). According to Olenin et al. (2007), this 

species causes alteration to the physical habitat without reducing total habitat area.
1097

Limnomysis benedeni is a host species of burn spot disease (Austin and Alderman 1987), a bacterial shell 

disease causing fungal infection of the exoskeleton and gills found in a number of crustacean taxa 

including crayfish.

There is little or no evidence to support that Limnomysis benedeni has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

According to Austin and Alderman (1987), L. benedeni is vulnerable to burn spot disease, a bacterial shell 

disease found in shellfish, including Oroconectes crayfish, though the frequency and severity of possible 

impacts on aquaculture are unknown.

Limnomysis benedeni has the potential for moderate beneficial effects if introduced to the Great 

Lakes.

Limnomysis benedeni is often found in the stomach of freshwater fish and has been emphasized as 

important food source, particularly for foraging fish (Rezsu and Specziár 2006, Zhuravel 1956). 

Additionally, increasing aquarist use of this species as fish fodder and as ornamental shrimp (Piepiorka 

and Walter 2006) is accompanied by increasing numbers of Internet offers for its sale (Wittmann and 

Ariani 2009) – though so far apparently only in Europe.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Limnomysis benedeni is a host species of burn spot disease (Austin and Alderman 1987), a bacterial shell 

disease causing fungal infection of the exoskeleton and gills found in a number of crustacean taxa, including

Oroconectes crayfish.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √
1098

Not significantly 0

Unknown U

 Based on its abundance and distribution, Olenin et al. (2007) assess the invasion effect of L. benedeni in the 

Curonian Lagoon as causing a moderate decline in abundance and reduction in range of native species.

 This species may outcompete the closely related genus Diamysis if it succeeds in invading fresh and brackish 

water Mediterranean tributaries (Wittmann and Ariani 2000). Bernauer and Jansen (2006) noted a loss of 

native macroinvertebrate species in the upper Rhine River, Germany after the appearance of a number of 

invasive macroinvertebrates, including L. benedeni.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U

 Additionally, this species may have altered the freshwater food web in Switzerland (Gauer and Imesch 2008).

Its impact on ecosystem functioning has been classified as moderate (i.e. weak modification of ecosystem 

performance and/or addition of a new, or reduction of existing, functional groups) (Olenin et al. 2007).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U
1099

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0

Unknown U

 The non-native population of L. benedeni in the strongly eutrophic Curonian Lagoon is reported to be a 

biomass dominant component of the nektobenthic community, with major significance in modifying 

sediment/habitat by pelletization (Olenin and Leppäkoski 1999). According to Olenin et al. (2007), this species 

causes alteration to the physical habitat without reducing total habitat area.

Environmental Impact Total 4

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6
1100

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U 

 According to Austin and Alderman (1987), L. benedeni is vulnerable to burn spot disease, a bacterial shell 

disease found in shellfish, (e.g., crayfish), though the frequency and severity of possible impacts on 

aquaculture are unknown.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 6
1101

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 

Not significantly 0 √

Unknown U
1102

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Increasing aquarist use of this species as fish fodder and as ornamental shrimp (Piepiorka and Walter 2006) is 

accompanied by increasing numbers of internet offers for its sale (Wittmann and Ariani 2009).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U

 L. benedeni is often found in the stomach of freshwater fish, and is therefore often emphasized as important 

food source, particularly for foraging fish (Rezsu and Specziár 2006, Zhuravel 1956).
1103

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1104

Scientific Name: Paramysis (Mesomysis) intermedia

Czerniavsky, 1882

Common Name:

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Paramysis intermedia has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Paramysis intermedia does not currently occur near the Great Lakes basin. Paramysis intermedia is not 

sold, stocked, or commercially cultured. Its eggs are contained in the female’s brood pouch (Borodich and 

Havlena 1973); thus, it is unlikely that the eggs can hitchhike or survive in ballast water. The adult forms 

are likely able to survive in ballast water due to their tolerance of a broad range of salinities (Ricciardi 

and Rasmussen 1998). 

Paramysis intermedia is native to the rivers connected to the Black and Caspian seas (Birshteina et al. 

1968). This species can travel downstream by moving with the current (Borodich and Havlena 1973). 

Paramysis intermedia was introduced to Lake Peipsi in the 1970s (Herkül et al. 2009). In 2008, this 

species was first recorded in the Gulf of Riga and the Gulf of Finland of the Baltic Sea. Paramysis 

intermedia occurs in ports that have direct trade connections with the Great Lakes (NBIC 2009). There 

are nonindigenous occurrences of Paramysis intermedia in waters that contain species that were 

introduced via ballast water (Ricciardi and Rasmussen 1998). 

Paramysis intermedia may be introduced to the Great Lakes via ships declaring “No Ballast on Board” 

(NOBOB), which are exempt from ballast water exchange. The majority of ships entering the Great Lakes 

are NOBOB vessels and 43% of these ships contain residual water with less than 10‰ salinity (Johengen 

et al. 2005). In the study, the temperature of the residual water from the vessels sampled ranged from -0.7 

to 23.9°C; thus Paramysis intermedia is likely to survive the salinity and temperature of the NOBOB 

ballast water.
1105

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 The species Paramysis intermedia does not occur in waters near the Great Lakes basin. P. intermedia is native 

to rivers connected to the Caspian Sea, Azov Sea and Black Sea.(Birshteina et. Al 1968) 

 Paramysis intermedia has been known to inhabit the Ponto-Caspian region and has also been introduced to 

Lake Peispi (Herkül et.al 2009).

 Observations of Ponto-Caspian species outside of their native range in European continental waters make clear 

that there are at least three main vectors for their spread west-ward. I) Construction of canals connecting river 

basins, II) water management in some canals and III) transportation attached to a vessel’s hull in ballast water 

(bij de Vaate et al. 2002).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Mysid crustaceans in general have poor dispersal due to their morphology. They carry their eggs and 

developing young in a brood pouch, cannot withstand desiccation and typically cannot actively disperse 

upstream; their continental distributions have therefore been largely defined by direct (lentic) waterway 

connections (Audzijonytė et al. 2006, Bănărescu 1991). 

 The species is not proximal to the Great Lakes basin. Paramysis species can be found in the Ponto-Caspian 

basin, Mediterranean Sea and Black and Azov Sea.
1106

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km Score x 0.75
1107

of the Great Lakes basin.

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40
1108

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 With the exception of some microbes, little is known regarding survival of freshwater organism in saline water. 

The survival rate of freshwater organisms immersed in saline ballast water is certainly much lower than that in 

fresh water (MacIssac et al. 2002). 

 Ponto-Caspian mysids exhibit a variety of salinity tolerances, involving both strictly stenohaline (<3%) and 

relatively euryhaline (0-12%) taxa (Daneliya 2003, Komarova 1991). 

 According to (Daneliya 2003), euryhalinity should have been an important ecophysiological property 

controlling the dispersal of species. 

 Ricciardi and Rasmussen (1998) identified P. intermedia as one of the Ponto-Caspian euryhaline 

macroinvertebrate species with invasion history. They also reported that P. intermedia along with other species 

were transported in ballast water. 

 This species occupies estuaries and lagoons (Audzijonytė et al. 2006) and estuaries are naturally highly 

stressed environments. They are inhabited by stress-tolerant biota (Dauvin et al. 2007) that has to cope with 

high natural loads of organic matter and decreased salinity. 

 (Bonsdorff and Pearson 1999) report that in Northeastern Baltic Sea, harsh environmental conditions result in 

a low number of benthic species. These species can be considered very tolerant to various disturbances 

including anthropogenic stresses .

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Present in: Azov sea, Baltic sea, Black Sea, Caspian Sea, United Kingdom Exclusive Economic Zone
1109

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1110

Paramysis intermedia has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

The native and introduced ranges of Paramysis intermedia have similar climate and abiotic conditions to 

that of the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species is 

likely capable of overwintering in the Great Lakes; it occurs in reservoirs elsewhere that have ice cover in 

the winter (Borodich and Havlena 1973). Paramysis intermedia prefers shallow, sandy habitats; thus this 

species is likely to find a suitable habitat in the Great Lakes. This species may benefit from increased 

salinization attributed to climate change because it can better tolerate higher salinities compared to 

species native to the Great Lakes. Paramysis intermedia has the potential to invade North American lakes 

that currently lack other mysid shrimp (Ricciardi and Rasmussen 1998). 

Paramysis intermedia has a non-specific, omnivorous diet; it will probably find an appropriate food 

source in the Great Lakes. Paramysis intermedia can produce up to 3 broods per year (Borodich and 

Havlena 1973). Paramysis intermedia produces an average of 7-30 embryos, which is slightly less than 

the number of embryos produced by Paramysis ullskyi. 

Paramysis intermedia was intentionally introduced to Lake Peipsi, but did not establish a permanent 

population (Herkül et al. 2009). This species was deliberately introduced to the Volga River and 

successfully established a population in its lower reaches and predominates the mysid community there 

(Borodich and Havlena 1973). In the 1960s, Paramysis intermedia was introduced from the Don River to 

the Aral Sea and became numerous in 1961 (Aladin et al. 2004). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 Ponto-Caspian mysids exhibit a variety of salinity tolerances, involving both strictly stenohaline (<3%) and 

relatively euryhaline (0-12%) taxa (Daneliya 2003, Komarova 1991).

 This species occupies estuaries and lagoons (Audzijonytė et al. 2006) and estuaries are naturally highly 

stressed environments. They are inhabited by stress-tolerant biota (Dauvin et al. 2007) that has to cope with 

high natural loads of organic matter and decreased salinity.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9
1111

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Paramysis intermedia has been found in the rivers of the Ponto-Caspian, as well as the Baltic Sea (Herkül et al. 

2009, Kotta and Möller 2009).

 This species inhabits cold freshwaters, though reproduction ceased below 10°C (Wooldridge 1986).

 Paramysis intermedia exist in reservoirs that have ice cover over winter, reproduce at 6-7°C (Borodich and 

Havlena 1973).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Ponto-Caspian macroinvertebrates have a non-specific food preference which is one of the biological factors 

that contributes to the invasion of regions beyond their native range (bij de Vaate et al. 2002)

 Mysidopsis species are omnivorous and cannibalistic, feeding on diatoms and small crustaceans such as 

copepods (Mauchline 1980). However, this particular species of mysid has a non-specific food source and 

therefore should not have trouble finding an appropriate food source.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
1112

Unknown U

2

 When studied, this species is found in low relative abundance (Herkül et al. 2009, Kotta and Möller 2009); 

however, has been found co-occuring with two other Ponto-Caspian invaders (C. cuvispinum and P. 

robustoides) (Herkül et al. 2009)

 Paramysis intermedia has reached 200-500 individuals/m2in Volga river (Borodich and Havlena 1973)

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

2

 Number of embryos of this species ranges from a mean of 7-30, based on female body size (3 generations). This 

is slightly less than P. ullskyi, which has mean range from 17-55 embryos (2 generations) (Borodich and 

Havlena 1973).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

3

 Paramysis intermedia is commonly called possum shrimp because the females carry their developing young in a 

bulging pouch or marsupium formed by at the base of their legs. The young mysids are not released until they 

are well-developed juveniles. Females produce young continuously, refilling their pouch with eggs as soon as 

their latest brood is released. The juvenile Mysids will reach their adult size of 1 inch (1.25 cm) in about 3 

weeks, creating a new generation every 30 days (Marini and Moe 2003).
1113

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Paramysis intermedia has been found in the rivers of the Ponto-Caspian, as well as the Baltic Sea (Herkül et al. 

2009, Kotta and Möller 2009). The Great Lakes and Ponto-Caspian region are climatically compatible, which 

is one of the attributing factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 

2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Paramysis intermedia has been found in the rivers of the Ponto-Caspian, as well as the Baltic Sea (Herkül et al. 

2009, Kotta and Möller 2009).

 Abiotic factors and climatic conditions of the native and introduced ranges of P. intermedia are quite similar to 

the Great Lakes, making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3
1114

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 This species has been found at depths of 1-2.1m, with sandy bottom (Herkül et al. 2009)

 Paramysis intermedia prefers sandy shallow-water habitat (Borodich and Havlena 1973)

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 This mysid can tolerate higher salinity waters, especially relative to native Great Lakes species.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Mysidopsis species are omnivorous and cannibalistic, feeding on diatoms and small crustaceans such as 

copepods (Mauchline 1980). However, this particular species of mysid has a non-specific food source and 

therefore should not have trouble finding an appropriate food source.
1115

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in -80% total 
1116

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 While juvenile fish may feed on this mysid, it will likely not prevent its establishment.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 With no resting stage, ballast introductions of this species would be rare.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

3
1117

 In 2008 P. intermedia was found for the first time in the Baltic Sea. There were two separate records in 2008, 

one from the Gulf of Riga and the other from the eastern Gulf of Finland. Although P. intermedia did not form a 

permanent population in Lake Peipsi after its deliberate introduction in the 1970s, the species might have 

survived in the Narva River and is currently invading the coastal sea. The invasion corridor of the Gulf of Riga 

population remains unknown (Herkül et al. 2009).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

2

 Although P. intermedia did not form a permanent population in Lake Peipsi after its deliberate introduction in 

the 1970s, the species might have survived in the Narva River and is currently invading the coastal sea.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 81

>100 High Adjustments

B. Critical species A*(1- 0%) 81
1118

51-99 Moderate C. Natural enemy B*(1- 0%) 81

Control measures C*(1- 0%) 81

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Paramysis intermedia if 

introduced to the Great Lakes is inadequate to support proper assessment.

If introduced to the Great Lakes, Paramysis intermedia may reduce zooplankton biomass through 

feeding, and consequently impact planktivorous fish populations (Ricciardi and Rasmussen 1998, Spencer 

et al. 1991); however, studies have not been conducted to determine if these effects are significant where 

Paramysis intermedia has been introduced. Studies suggest that due to biomagnification of contaminants 

from mysids to fish, levels of PCB and mercury in pelagic fish are higher in North American lakes that 

contain mysids compared to those that lack mysids (Cabana et al. 1994, Rasmussen et al. 1990); however, 

the aforementioned studies do not specifically investigate the impacts of Paramysis intermedia on 

biomagnification of contaminants. 

There is little or no evidence to support that Paramysis intermedia has the potential for significant 

socio-economic impact if introduced to the Great Lakes.

It has not been reported that Paramysis intermedia poses a threat to human health or water quality. There 

is no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Paramysis intermedia has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It is unknown if the introduction of Paramysis intermedia to the Great Lakes would increase fish 

productivity. Paramysis intermedia was intentionally introduced to fisheries in Europe to improve 
1119

productivity. However, it can potentially compete with fish for zooplankton and harm fish populations 

(Ricciardi and Rasmussen 1998, Spencer et al. 1991). It has not been indicated that Paramysis intermedia 

can be used for the control of other organisms or improving water quality. There is no evidence to suggest 

that this species is medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 When studied this species has been found in low relative abundance (Herkül et al. 2009, Kotta and Möller 

2009); however, has been found co-occuring with two other Ponto-Caspian invaders (C. cuvispinum and P. 

robustoides) (Herkül et al. 2009)

 Paramysis intermedia has reached 200-500 individuals/m2 in Volga river (Borodich and Havlena 1973)

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

1 
1120

effects of which have not been widespread or severe

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 0

Total Unknowns (U) 6
1121

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?
1122

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1123

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?
1124

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1125

Scientific Name: Paramysis (Metamysis) ullskyi

Czerniavsky, 1882

Common Name: Mysid Shrimp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Paramysis ullskyi has a moderate probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping (ballast water)

Paramysis intermedia does not currently occur near the Great Lakes Basin. Paramysis intermedia is not 

sold, stocked, or commercially cultured. Its eggs are contained in the female’s brood pouch (Borodich and 

Havlena 1973); thus, it is unlikely that the eggs can hitchhike or survive in ballast water. The adult forms 

are likely able to survive in ballast water due to their tolerance of a broad range of salinities (Ricciardi 

and Rasmussen 1998). 

Paramysis intermedia may be introduced to the Great Lakes via ships declaring “No Ballast on Board” 

(NOBOB), which are exempt from ballast water exchange. The majority of ships entering the Great Lakes 

are NOBOB vessels and 43% of these ships contain residual water with less than 10‰ salinity (Johengen 

et al. 2005). In the study, the temperature of the residual water from the vessels sampled ranged from -0.7 

to 23.9°C; thus Paramysis intermedia is likely to survive the salinity and temperature of the NOBOB 

ballast water. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
1126

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 This species occurs in European part of Russia, Baltic Sea, Caspian Sea, North Atlantic near Russia.

 The species is indigenous to waters surrounding the western part of Russia, as well as the Baltic, Caspian, and 

north Atlantic near Russia.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Paramysis ullskyi is indigenous to the European part of Russia in the Ponto-Caspian basin.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
1127

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 While the specific species is not stated, similar mysid shrimp indigenous to the same area has been used as fish 

food for fauna enrichment in the Soviet Union back in the 1970s. However, it is unknown whether this is still in 

practice today, or if particular mysids are used for fish farms in the United States.

 No evidence was shown that this particular species has arrived to the Great Lakes nor is there any recent 

evidence of this species being used currently in either Russia or the United States.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

 It is only known to be used for fish and fauna enrichment around the Ponto-Caspian area around Russia. 

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U
1128

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 While there has been history of transport, similar species have been transported only throughout Russia, and 

not to the Great Lakes.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 While Paramysis has a broad range in salinity tolerance, Ovcarenko (2006) has shown that there is high 

mortality when the salinity change is really sudden, such as when changing ballast water. Mortality occurs 

when they approach 15 PSU.
1129

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 The species is indigenous to the European part of Russia in the Ponto-Caspian basin.

 This species occurs in European part of Russia, Baltic Sea, Caspian Sea, North Atlantic near Russia.

 The species is indigenous to waters surrounding the western part of Russia, as well as the Baltic, Caspian, and 

north Atlantic near Russia.

Scoring

Points (per vector) Probability for Introduction

80-100 High

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1130

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Paramysis ullskyi has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: moderate)

The native and introduced ranges of Paramysis intermedia have similar climate and abiotic conditions to 

that of the Great Lakes (Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008). This species is 

likely capable of overwintering in the Great Lakes; it occurs in reservoirs elsewhere that have ice cover in 

the winter (Borodich and Havlena 1973). Paramysis intermedia prefers shallow, sandy habitats; thus this 

species is likely to find a suitable habitat in the Great Lakes. This species may benefit from increased 

salinization attributed to climate change because it can better tolerate higher salinities compared to 

species native to the Great Lakes. Paramysis intermedia has the potential to invade North American lakes 

that currently lack other mysid shrimp (Ricciardi and Rasmussen 1998). 

Paramysis intermedia has a non-specific, omnivorous diet; it will probably find an appropriate food 

source in the Great Lakes. Paramysis intermedia can produce up to 3 broods per year (Borodich and 

Havlena 1973). Paramysis intermedia produces an average of 7-30 embryos, which is slightly less than 

the number of embryos produced by Paramysis ullskyi. 

Paramysis intermedia was intentionally introduced to Lake Peipsi, but did not establish a permanent 

population (Herkül et al. 2009). This species was deliberately introduced to the Volga River and 

successfully established a population in its lower reaches and predominates the mysid community there 

(Borodich and Havlena 1973). In the 1960s, Paramysis intermedia was introduced from the Don River to 

the Aral Sea and became numerous in 1961 (Aladin et al. 2004). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 6
1131

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 The Ponto-Caspian region, where P. ullskyi originates, is quite similar to the Great Lakes. The spatial 

temperature mean is 13.7 degrees with a range of 12.1 to 16.1. 

 Paramysis ullskyi cannot tolerate a sudden salinity change to 18 PSU levels of salinities, and its natural salinity 

environment was 3 psu. (Ovcarenko 2006).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Given their origins around northern Russia, mysid shrimp can survive long periods of time within colder and 

deeper waters.

 Parmysis ullskyi exist in reservoirs that have ice cover over winter, reproduce at 6-7 ̊C (Borodich and Havlena 

1973).

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

7

 Paramysis ullskyi mainly consumes the detritus of surface ground laters (Borodich and Havlena 1973).

4) How likely is this species to outcompete species in the Great Lakes for available resources?
1132

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 Mysids can cause a lowering of zooplankton abundance (Ketelaars et al. 1999).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

5

 Nothing specific has been shown to differentiate the reproductive ability from other similar species within the 

same taxa.

 The number of embryos ranges from a mean of 17-55, based on female body size (2 generations). This is 

slightly more than P. intermedia, which has mean range from 7-30 embryos (3 generations) (Borodich and 

Havlena 1973).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 0
1133

establishment in new environments)

Unknown U

3

 This species is a brooder.

 Paramysis ullskyi abilities and tolerances make it likely, but only literature found on invasions of other 

European lakes have been found.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 The Great Lakes are known to change seasons, having an average temperature of less than 5 ̊C on the surface 

in the winter months, then 5 – 15 degrees with the onset of spring, and up to 25 degrees in the summer (data 

from the NOAA Coastwatch Great Lakes website, specifically to Lake Ontario.

 The Ponto-Caspian region, where P. ullskyi originates, is actually quite similar. The spatial temperature mean 

is 13.7 degrees with a range of 12.1 to 16.1. This is warmer, but climate change would cause the Great Lakes to 

be more similar (USEPA 2008).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Paramysis ullskyi is known to live in 0-4% salinity (Audzijonytė et al. 2006), and their native lake salinities 

have a wide range, with the Black Sea reaching salinities of 22 ppt, the Azov up to 12 ppt, and the Caspian 

reaching 13 ppt. The Great Lakes salinities tend to be close to 0.

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing factors 

to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).
1134

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Paramysis intermedia prefers sandy shallow-water habitat (Borodich and Havlena 1973).

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

7

 The Ponto-Caspian region, where P. ullskyi originates, is actually quite similar to the Great Lakes.. The spatial 

temperature mean is 13.7 degrees with a range of 12.1 to 16.1. This is warmer, but climate change would cause 

the Great Lakes to be more similar (USEPA 2008).

 Due to their wider temperature tolerances, Paramysis ullskyi can be very adaptable to warmer temperatures 

and shallower waters. Even though the Great Lakes may be slightly colder in the winters than what the species 

may be used to, climate change would adjust that factor in the future (USEPA 2008).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9
1135

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Much of the sustenance of Paramysis ullskyi can be found both in their native waters and in the Great Lakes. 

They survive on algae and zooplankton (Ketelaars et al. 1999).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6
1136

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There was no indication of this species that would facilitate their establishment.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Larger fish have always been the main predator of mysid shrimp, though a specific one is not mentioned. This 

hasn’t really controlled the native mysid shrimp in the Great Lakes region.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 There were multiple reports of invasions in Europe outside the Ponto-Caspian but it did not mention anything 

on frequency (Ketelaars 1997).
1137

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

8

 Paramysis ullskyi was spread via ballast water to other Baltic lakes throughout Europe. This was shown 

through actual physical observation and mitochondrial DNA tracking of migrating species. (Audzijonytė 2008, 

bij de Vaate et al. 2002)

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

 In the 1950s, H. anomala, a similar species with nearly the same origins in the Ponto-Caspian area, were 

intentionally introduced in fisheries in the Dnieper River, and in the Dubossart reservoir in Moldovia. 

Throughout the 70s and onward, mysids distributed through Europe vie rivers and tributaries (bij de Vaate et 

al. 2002)

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

-50% total 

points (at 
1138

to control its establishment and spread) end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 89

>100 High Adjustments

B. Critical species A*(1- 0%) 89

51-99 Moderate C. Natural enemy B*(1- 0%) 89

Control measures C*(1- 0%) 89

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 2

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Low

Beneficial: Low

Current research on the potential for environmental impacts to result from Paramysis intermedia if 

introduced to the Great Lakes is inadequate to support proper assessment.

If introduced to the Great Lakes, Paramysis intermedia may reduce zooplankton biomass through 

feeding, and consequently impact planktivorous fish populations (Ricciardi and Rasmussen 1998, Spencer 
1139

et al. 1991); however, studies have not been conducted to determine if these effects are significant where 

Paramysis intermedia has been introduced. Studies suggest that due to biomagnification of contaminants 

from mysids to fish, levels of PCB and mercury in pelagic fish are higher in North American lakes that 

contain mysids compared to those that lack mysids (Cabana et al. 1994, Rasmussen et al. 1990); however, 

the aforementioned studies do not specifically investigate the impacts of Paramysis intermedia on 

biomagnification of contaminants. 

There is little or no evidence to support that Paramysis intermedia has the potential for significant 

socio-economic impact if introduced to the Great Lakes.

It has not been reported that Paramysis intermedia poses a threat to human health or water quality. There 

is no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Paramysis intermedia has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It is unknown if the introduction of Paramysis intermedia to the Great Lakes would increase fish 

productivity. Paramysis intermedia was intentionally introduced to fisheries in Europe to improve 

productivity. However, it can potentially compete with fish for zooplankton and harm fish populations 

(Ricciardi and Rasmussen 1998, Spencer et al. 1991). It has not been indicated that Paramysis intermedia 

can be used for the control of other organisms or improving water quality. There is no evidence to suggest 

that this species is medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 1 
1140

fecundity) or decline of at least one native population

Not significantly 0

Unknown U

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 Ketelaars (1997) mentions an almost absent population of in zooplankton and phytoplankton biomass as a 

result of invasion, in a span of almost a decade. While this is referencing Hemimysis anomola, this reference 

also indicates that Paramysis is part of the most frequent Ponto-Caspian invaders they are researching, and it is 

known that H. anomala and Paramysis are part of the same taxonomic subfamily, only differing in genus (Mees 

2015).

 Mysid shrimp tend to be the preferred choice of prey for many fish species, but this does not impact their 

invasiveness significantly.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

 There was no mention of any alteration to species.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 

Unknown U √
1141

 It can be speculated that it can, considering that colonies of paramysis and feed on vast quantities of algae as 

well as reduce populations of zooplankton and phytoplankton (Porter et al. 2008). Theoretically, it can increase 

clarity and alter certain chemical content.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 7

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
1142

Not significantly 0 √

Unknown U

 There was no mention other than possible ecological effects.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 It has only been reported to have decreased alga levels as well as overall diversity of the food web.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 Not negatively, but in fact related paramysis species have been a frequent choice of commercial fisheries since 

they are prime food sources for new fauna.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 6
1143

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6 

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U
1144

 Mysid shrimp has been used extensively to feed fisheries, mainly because they are relatively easy to culture 

because to their wide habitat tolerances (Marini and Moe 2003). 

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 1

Total Unknowns (U) 0
1145

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1146

Scientific Name: Paramysis (Serrapalpisis) lacustris

Czerniavsky, 1882

Common Name: Opossum Shrimp

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Paramysis lacustris has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Paramysis lacustris has been observed in ballast waters of ships in the North Sea (Gollasch 2002) and is 

considered to have the potential for introduction to the Great Lakes via European ballast water transport 

(Ricciardi and Rasmussen 1998). In a recent study, P. lacustris showed a mortality rate of 60% after 24 

hours of exposure to a salinity of 19 PSU, and a mortality rate of 100% with exposure to 23 PSU 

(Ovcarenko et al. 2006). Considering this relatively high short-term salinity tolerance, ballast water 

regulations requiring salinities of at least 30 PSU are believed to be an appropriate means of control 

(Ovcarenko et al. 2006). More recently, under current mandatory ballast water regulations (flushing with 

at least 30 ppt), the risk of entry for this particular species has been modeled as low due to these 

physiological salinity constraints (Grigorovich et al. 2003).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √
1147

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U
1148

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?
1149

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Paramysis lacustris is considered to have the potential for introduction to the Great Lakes via European ballast 

water transport (Ricciardi and Rasmussen 1998).

 This species showed a mortality rate of 60% after 24 hours of exposure to salinity of 19 PSU, and a mortality 

rate of 100% with exposure to 23 PSU (Ovcarenko et al. 2006). Considering this relatively high short-term 

salinity tolerance, ballast water regulations requiring salinity flushing with at least 30 PSU are believed to be 

an appropriate means of control (Ovcarenko et al. 2006).

 Under mandatory ballast water regulations, the risk of entry for this particular species has been modeled as 

low due to physiological salinity constraints (Grigorovich et al. 2003).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0
1150

Unknown U

 Paramysis lacustris has been observed in ballast waters of the North Sea, a region where Great Lakes shipping 

traffic originates (Gollasch 2002). There are no current records of this species being observed in ships entering 

the Great Lakes.

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1151

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Paramysis lacustris has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

Paramysis lacustris is recognized as a stenohaline species, typically occurring in salinities of 0-3 PSU 

(Daneliya 2002, Komarova 1991); however, it has been able to survive short-term salinity exposures of 

up to 24 PSU (Santagata 2008). A particular trait of P. lacustris that causes increased concern over 

invasion is its adaptation to water temperatures up to 20°C, while the coldwater mysids already present in 

the Great Lakes only tolerate temperatures of up to about 10°C (Bondarenko and Yablonskaya 1979). 

Paramysis lacustris have been known to survive in situ in temperatures up to 28°C (Baychorov 1980), 

although this may not be the upper bound for survival (Horan and Lupi 2003). This species can tolerate 

up to 110 days of ice cover per year (Olenin and Leppäkoski 1999), and is thus expected to have the 

ability to overwinter within the Great Lakes. The effects of climate change (warming water temperatures) 

are likely to have a positive effect on this species as compared with Great Lakes native mysids due to its 

greater degree of adaptation to warm, shallow waters (Bondarenko and Yablonskaya 1979, Ricciardi and 

Rasmussen 1998).

The range of this species has showed continued expansion throughout the waters of Eastern Europe and 

Russia over recent decades (Mordukhaĭ-Boltovskoĭ 1979a, Mordukhaĭ-Boltovskoĭ 1979b, Salemaa and 

Hietalahti 1993, Tarasov 1996), and it has become numerically dominant by biomass in invaded 

communities (Olenin and Leppäkoski 1999). This species has been intentionally transplanted with great 

success into many lakes and reservoirs in Eurasia and the Baltic Peninsula, where it has rapidly formed 

dense populations (Mordukhaĭ-Boltovskoĭ 1964 and 1979a). Current North American ballast water 

regulations requiring flushing with water of at least 30 ppt have thus far been effective in preventing the 

establishment of this species in the Great Lakes.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Paramysis lacustris is recognized as a stenohaline species, typically occurring in salinities of 0-3 PSU 

(Daneliya 2002, Komarova 1991); however, it has been able to survive short-term salinity exposures of up to 24 

PSU (Santagata 2008).
1152

 A particular trait of P. lacustris that causes increased concern over invasion is its adaptation to water 

temperatures up to 20°C, while the coldwater mysids already present in the Great Lakes only tolerate 

temperatures of up to about 10°C (Bondarenko and Yablonskaya 1979).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Paramysis lacustris can tolerate ice cover for periods of up to 110 days per year (Olenin and Leppäkoski 1999).

 Within its introduced range in the Curonian Lagoon, P. lacustris is likely exposed to water temperatures 

averaging 0.1–19.3°C (monthly average) (Gasiunaite et al. 2008).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 As an adult, P. lacustris is omnivorous, although the diet of immature individuals is considered largely 

herbivorous. During development, prey shifts from primarily phytoplankton in juveniles to include a larger 

proportion of mesoplankton in adults, while immature or subadult individuals show mixed diets (Lesutiene et al. 

2007).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3
1153

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 In waters void of other mysids, P. lacustris tends to quickly build dense populations (Olenin and Leppäkoski 

1999).

 The range of this species has showed continued expansion throughout the waters of Eastern Europe and Russia 

over recent decades (Mordukhaĭ-Boltovskoĭ 1979a, Mordukhaĭ-Boltovskoĭ 1979b, Salemaa and Hietalahti 

1993, Tarasov 1996), and it has become numerically dominant by biomass in invaded communities (Olenin and 

Leppäkoski 1999).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
1154

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and 

Orlova 2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas 

(Grigorovich et al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9
1155

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

 Ponto-Caspian mysids, such as P. lacustris, differ greatly from their North American counterparts in their level 

of adaptation to shallow, warm waters. For instance, the metabolic rate of P. lacustris at 20°C is similar to that 

of cold-water mysids at 10°C (Bondarenko and Yablonskaya 1979).

 The effects of climate change (warming water temperatures) are likely to have a positive effect on this species 

as compared with Great Lakes native mysids due to its greater degree of adaptation to warm, shallow waters 

(Bondarenko and Yablonskaya 1979, Ricciardi and Rasmussen 1998).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Phytoplankton and mesoplankton comprise the diets of juveniles and adults, respectively. Neither of these prey 

items are limiting within the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

9
1156

assessed;

OR,

No, there is no critical species required by the species being assessed

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by P. lacustris.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

-60% total 

points (at 
1157

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

U

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species has been intentionally transplanted with great success into many lakes and reservoirs in Eurasia 

and the Baltic Peninsula, where it has rapidly formed dense populations (Mordukhaĭ-Boltovskoĭ 1964,

Mordukhaĭ-Boltovskoĭ 1979a).
1158

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 The range of P. lacustris has showed continued expansion throughout the waters of Eastern Europe and Russia 

over recent decades (Mordukhaĭ-Boltovskoĭ 1979a, Mordukhaĭ-Boltovskoĭ 1979b, Salemaa and Hietalahti 

1993, Tarasov 1996), and it has become numerically dominant by biomass in the communities into which it has 

become incorporated (Olenin and Leppäkoski 1999).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 95

>100 High Adjustments

B. Critical species A*(1- 0%) 95

51-99 Moderate C. Natural enemy B*(1- 0%) 95

Control measures C*(1- 0%) 95

0-50 Low Potential for Establishment Moderate
1159

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 4

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

Paramysis lacustris has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Prior to its introduction into the Curonian lagoon, studies showed that P. lacustris exhibited preferential 

feeding on detritus and phytoplankton; its establishment was expected to improve the efficiency of 

detritus and primary production utilization in the autotrophic waters of the lagoon (Komarova 1991). 

However, gut samples later taken from introduced individuals revealed a significant proportion of 

planktonic crustaceans, suggesting active feeding on mesoplankton as opposed to detritus and 

phytoplankton (Jankauskiene 2003, Lesutiene et al. 2007). Therefore, if introduced to the Great Lakes, 

this species is expected to cause a zooplankton reduction in areas it invades, leading to spiraling negative 

effects on planktivorus fish and higher trophic levels (Ricciardi and Rasmussen 1998, Spencer et al. 

1991). Hence, P. lacustris could potentially become the dominant species in many areas of the Great 

Lakes currently absent of mysids (Ricciardi and Rasmussen 1998). An expected negative effect of this is 

the biomagnification of contaminants, such as PCB and mercury, in higher trophic levels due to 

lengthening of the food chain (Ricciardi and Rasmussen 1998). 

In the Baltic Sea, P. lacustris has significantly modified invaded habitat through pelletization of the 

substrate (Olenin and Leppäkoski 1999).

There is little or no evidence to support that Paramysis lacustris has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

Biomagnification of contaminants in higher trophic levels would likely occur as the result of a 

lengthening in food chain length where this species invades (Ricciardi and Rasmussen 1998). This would 

result in higher PCB and mercury levels in pelagic fish, causing potential harm to commercial fisheries. 

Studies have already shown mercury and PCB levels to be significantly higher in North American mysidcontaining lakes as opposed to mysid-free lakes (Cabana et al. 1994, Rasmussen et al. 1990). However, 

the scale of the resulting economic effects on fisheries is unknown.
1160

There is little or no evidence to support that Paramysis lacustris has the potential for significant 

beneficial effects if introduced to the Great Lakes.

Paramysis lacustris has been recognized as an important food source for many fishes (Ricciardi and 

Rasmussen 1998), and was intentionally introduced into many lakes and reservoirs in the Baltic Peninsula 

to support commercial fisheries in the early 1960s (Arbačiauskas 2002, Gasiunas 1964, Komarova 1991,

Leppäkoski et al. 2002, Mordukhaĭ-Boltovskoĭ 1964, Mordukhaĭ-Boltovskoĭ 1979a). However, in areas 

where introduced, the negative impacts of this species have been far more significant than any beneficial 

effect provided.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has resulted in the reduction or extinction of one or more native species 

populations, affects multiple species, or is a reportable disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems, 

etc.)

1 √

Not significantly 0

Unknown U

 If introduced to the Great Lakes, this species is expected to cause a zooplankton reduction in areas it 

invades, leading to spiraling negative effects on planktivorus fish and higher trophic levels (Ricciardi and 

Rasmussen 1998, Spencer et al. 1991). An expected negative effect of this is the biomagnification of 

contaminants, such as PCB and mercury, in higher trophic levels due to lengthening of the food chain 

(Ricciardi and Rasmussen 1998).

 Studies have already shown mercury and PCB levels to be significantly higher in North American mysidcontaining lakes as opposed to mysid-free lakes (Cabana et al. 1994, Rasmussen et al. 1990).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light, etc.)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, 

behavioral changes, etc.) on one or more native species populations

6

Yes, and it has caused some noticeable stress to or decline of at least one native species 

population

1

Not significantly 0

Unknown U √

 Paramysis lacustris could potentially become the dominant species in many areas of the Great Lakes 

currently absent of mysids (Ricciardi and Rasmussen 1998).
1161

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., added pressure to threatened/endangered species, significant reduction or extinction 

of any native species populations, creation of a dead end or any other significant alteration 

in the food web, etc.)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U

 Prior to its introduction into the Curonian lagoon, studies showed that P. lacustris exhibited preferential 

feeding on detritus and phytoplankton; its establishment was expected to improve the efficiency of detritus 

and primary production utilization in the autotrophic waters of the lagoon (Komarova 1991). However, gut 

samples later taken from introduced individuals revealed a significant proportion of planktonic 

crustaceans, suggesting active feeding on mesoplankton as opposed to on detritus and phytoplankton 

(Jankauskiene 2003, Lesutiene et al. 2007).

 If introduced to the Great Lakes, this species is expected to cause a zooplankton reduction in areas it 

invades, leading to spiraling negative effects on planktivorus fish and higher trophic levels (Ricciardi and 

Rasmussen 1998, Spencer et al. 1991).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression, etc.)?

Yes, and it has caused a loss or alteration of genes which may be irreversible or has led to 

the decline or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles, etc.)?

Yes, and it has had a widespread, long term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been mild

1

Not significantly 0 √

Unknown U

Does it alter the physical ecosystem in some way (e.g., facilitated erosion/siltation, altered hydrology, 

altered macrophyte/phytoplankton communities, changes to substrate (physical or chemical), etc.)?
1162

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0

Unknown U

 In the Baltic Sea, P. lacustris has significantly modified invaded habitat through pelletization of the 

substrate (Olenin and Leppäkoski 1999).

Environmental Impact Total 3

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (such as water intakes, pipes, or any other industrial or 

recreational infrastructure)?
1163

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

Does it negatively affect water quality?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture, etc.)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

 Biomagnification of contaminants to higher trophic levels would likely occur as the result of a lengthening 

in food chain length where this species invades. This would result in higher PCB and mercury levels in 

pelagic fish, causing potential harm to commercial fisheries (Ricciardi and Rasmussen 1998). However, 

the scale of the resulting economic effects on fisheries is unknown.

S5) Does it inhibit recreational activities and/or associated tourism (e.g. through frequent water closures, 

equipment damage, decline of recreational species, etc.)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U
1164

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g. for fisheries, aquaculture, agriculture, bait, ornamental trade, etc.)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U

 Paramysis lacustris has been recognized as an important food source for many fishes (Ricciardi and 

Rasmussen 1998), and was intentionally introduced into many lakes and reservoirs in the Baltic Peninsula 

to support commercial fisheries in the early 1960s (Arbačiauskas 2002, Gasiunas 1964, Komarova 1991,

Leppäkoski et al. 2002, Mordukhaĭ-Boltovskoĭ 1964, Mordukhaĭ-Boltovskoĭ 1979a). However, in areas 

where introduced, the negative impacts of this species have been far more significant than any beneficial 

effect provided.
1165

B3) Is it recreationally valuable (e.g. for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U 

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species which is threatened, endangered species, or commercially valuable, etc.)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 1

Total Unknowns (U) 0
1166

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1167

A.8 Crustaceans - Crayfishes

Scientific Name: Cherax destructor

Clark, 1936

Common Name: Yabby

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Low

Cherax destructor has a low probability of introduction to the Great Lakes (Confidence level: High).

Potential pathway(s) of introduction: Unauthorized Intentional Release

Cherax destructor is not currently in waters connecting to the Great Lakes and is not known to be 

transported through the Great Lakes region. However, it has been increasingly transported globally which 

could increase the future risk of introduction into the Great Lakes. Cherax destructor was originally 

transported for aquaculture and food, but more recently, it has gained popularity as a pet (Chucholl 2013). 

Cherax destructor has a relatively high commercial value (Chucholl 2013). When used as bait, unused 

live bait is often directly discarded in to water (Gherardi 2007). The potential for specimens to be released 

and become established is extremely high, especially in temperate and warmer climates (Allen and 

Gherardi 2011). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 0 √
1168

not mobile or able to be transported by wind or water.

Unknown U

 Cherax destructor in naturally found in Australia; it has been found in Victoria, New South Wales, and Southern 

Queensland (USFWS 2014d).

 This species has been introduced to Switzerland, Austria, Netherlands, England, and Germany (Chucholl 2013).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 The yabby is usually found buried in the settlement of muddy waters (Withnall 2000).

 Cherax destructor is currently a restricted species in Minnesota, Michigan, Illinois, and Ohio.

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?
1169

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Cherax destructor has a relatively high commercial value (Chucholl 2013).

 This species is used as bait, and unused live bait is often being discarded directly into the water (Gherardi 

2007).

 The Yabby is considered a culinary delicacy Europe and farmed in some countries (e.g. Italy).

 Yabby is an aquarium species that is easy to maintain; it can be purchased through e-commerce and is 

increasingly used in research.

 The potential for specimens to be released and become established is extremely high, especially in temperate 

and warmer climates (Allen and Gherardi 2011).

 In 2009, Cherax destructor was one of the most popular species in aquarium trade in the Netherlands; 

popularity was found to have direct link to chance of introduction/establishment (Chucholl 2013).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5 

√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Cherax destructor is accessible in the United States in areas outside the Great Lakes region. There are none 

currently found in the Great Lakes region.

 Shipping for aquarium trade between the United States and Europe decreased due to crayfish plague, which 

originated from the crayfish brought from the US; the plague was first recorded in 1859 and removed up to 

95% of the indigenous European crayfish species (Chucholl 2013).

 Cherax destructor is currently a restricted species in Minnesota, Michigan, Illinois, and Ohio.

 It is available for sale online in the United States and could easily be purchased by someone in the Great Lakes

region (e.g., Ebay ).

 They can also be purchased from outside the United States and shipped (e.g., Blue Yabby Australia).

 Sixteen online shops offer 37 different nonindigenous crayfish species, including C. destructor, and on a scale 

from very rare to very common, the Yabby was considered a common species to be found in aquariums 

(Chucholl 2013).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U
1170

 At the time of this assessment, there is no record of C. destructor being stocked in close proximity to the 

Great Lakes.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

 Cherax destructor is not known to be transported through the Great Lakes region, but its transport has been 

increasing globally, increasing the future risk of introduction.

 This species was originally transported for aquaculture and food, but more recently, it has gained popularity as 

a pet (Chucholl 2013).

 Out of the 600 crayfish species that are found worldwide, the Yabby is one of the few with commercial value 

(Harlioglu and Harlioglu 2006).

 Since the 1970s, C. destructor was intentionally introduced into different areas, specifically in Africa and China 

for aquacultural purposes (Harlioglu and Harlioglu 2006).

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1
1171

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Cherax destructor has a large tolerance to changing environments (such as temperature, water levels, oxygen 

levels, and salinity); it can occupy different habitats for a short period of time and can quickly colonize in new 

environments (USFWS 2014d).

 The Yabby has a temperature tolerance of 1-35°C. It stops growing when salinity levels reach 8 ppt and death 

occurs at 16 ppt. Oxygen levels reaching less than 1 mg/L and a pH range of 7 to 9 can be tolerated (USFWS 

2014d).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0 √

Unknown U

 There is no evidence at this time showing that there is shipping traffic to the Great Lakes region from waters 

where the Yabby is present.

 Due to the crayfish plague, shipping has been more restricted.
1172

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0 0 Low

Total Unknowns (U) 0 Confidence Level High
1173

Cherax destructor has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Since 1932, Cherax destructor has become a growing problem. Its original invasion occurred within the 

Australian continent. Once people started developing an interest in this species, it spread across the globe 

to Europe and Africa. Wild populations have been established and posed a threat to native crayfish

populations and other species.

The biology of the Yabby has aided in its survival. The Yabby has proven to have a high tolerance to 

many different environments and high fecundity. It also has an aggressive behavior that allows it to 

compete with other species for food. Cherax destructor does not have many predators in the Great Lakes 

region nor does it rely on certain species for survival. There are some regulatory measures set in place to 

prevent the further spread of C. destructor.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Cherax destructor is known to have a high tolerance to a variety of environments.

 This species is generally found where there are high oxygen levels and a good source of vegetation (Withnall 

2000).

 This species’ ideal temperature range is 20-25°C, but they are able to survive in 1-35°C while growth stops 

below 16°C and above 35°C (Withnall 2000).

 High salinity levels are tolerated by the Yabby, but only for a period of time. They can survive in sea water for 

up to 48 hours, but after this stress on their systems, they stop growing (Withnall 2000).

 Yabby can tolerate low oxygen levels, but after long periods of time, their growth will stop (Withnall 2000).

 The Yabby prefers muddy waters opposed to clear water environments (Withnall 2000), and this species

survivse dry periods by burrowing in the mud (Geddes and Smallridge 1993).

 They are polytrophic and have high fecundity, which increases their ability to survive (Geddes and Smallridge 

1993).

 The eggs of Cherax destructor were tested and were able to tolerate stress of changes environments, but they 

were not as harvestable. The conditions they tested were temperature, oxygen levels, salinity, and light (Geddes 

and Smallridge 1993).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?
1174

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Cherax destructor has a high climate match with the United States, particularly in the East, Texas, and 

Northwest. A climate match of 0.103 and higher is considered a high match, and the Yabby has a match of 

0.388 (USFWS 2014d).

 The extreme temperatures near the Great Lakes may affect the growth of the Yabby during some seasons, but 

their high proliferation would help them survive. They have two spawning events per season and produce 

approximately 1000 eggs per spawn. Reproduction is linked to water temperature, so the spring and summer 

would be ideal seasons (Withnall 2000).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

8

 The diet of C. destructor is not fully know, but it is known to be an omnivorous species that feeds on plants, 

detritus, and some arthopods (Allen and Gherardi 2011).

 Their diet also switches according to climate. During summer seasons, they tend to eat fish, and in the winter, 

they eat plants and detritus (USFWS 2014d).

 Cherax destructor may have cannibalistic tendencies in areas where there is an overabundance of the species 

and low levels of natural food sources (Allen and Gherardi 2011).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

0
1175

species in the Great Lakes)

Unknown U

7

 The Yabby has shown antagonistic behavior to get access to limited resources. In a trial competition between 

the Yabby and the Marron, Cherax tenuimanus, the Yabby won. They concluded that its aggression led to 

success (Gherardi 2007).

 Another crayfish species, Rusty Crayfish or Orconectes rusticus, is native to the United States but has invaded 

Minnesota, Wisconsin, Michigan, Illinois, and other states. Its spread has caused a reduction in the native 

crayfish population, aquatic plants, and fish populations (University of Minnesota 2009).

 The Rusty Crayfish is similar to the yabby because it is a larger crayfish species with an aggressive behavior 

and an opportunistic diet (University of Minnesota 2009).

 The success of the Rusty Crayfish’s invasion could give some insight to how the Yabby would compete in the 

Great Lakes region.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

3

 The Yabby is polytrophic and have high fecundity which increases their ability to survive (Geddes and 

Smallridge 1993).

 When considering other crayfish species, the Yabby is mostly considered a r-selected species which has 

characteristics of short life cycles, high fecundity, and fast growth. These are also characteristics of good 

invaders (Gherardi 2007). 

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0
1176

Unknown U

0

 The reproductive habits of this species is affected by increased day length and water temperature. The eggs rest 

on the females swimming legs while waiting to hatch (USFWS 2014d).

 The seasonal changes in the spring that cause reproduction to begin would be suitable for the Yabby, but its 

reproductive habits would not affect its ability to become established in the new environment.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

5

 Cherax destructor has a high climate match with the United States, particularly in the East, Texas, and 

Northwest. A climate match of 0.103 and higher is considered a high match, and the yabby has a match of 0.388 

(USFWS 2014d).

 When comparing climate conditions of a native region (New South Wales, Australia) to a potential new region 

in the Great Lakes (Detroit, Michigan) ,there are some similarities and differences. The temperature range in 

Australia is less drastic than in Michigan, but they reach similar values. In Australia, the average maximum 

temperature ranges from 63°F to79°F, and the average minimum temperature ranges from 45°F to 66°F. In 

Michigan, the average maximum temperature ranges from 29°F to 84°F, and the average minimum 

temperature ranges from 15°F to 63°F. The seasonal changes occur at opposite times with spring being from 

September to November, summer being from December to February, autumn being from March to May, and 

winter being from June to August (Australia climate, Michigan climate). 

 The two locations have similar rainfall measurements but during different months. The most rainfall occurs 

from January to June in Australia and from May to September in Michigan (Average Australia rainfall, 

Average Michigan rainfall).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0
1177

Unknown U

7

 C. destructor is adapted to a wide range of water temperatures, between 1°C and 35°C. It does not grow at 

water temperatures below 15°C and falls into a state of partial hibernation (i.e. metabolism and feeding cease) 

when water temperature drops below 16°C (Withnall 2000). 

 It tolerates high salinities, with growth ceasing at 8 ppt (approximately equal to 25% seawater) and mortalities 

starting to occur at 16 ppt (Mills and Geddes 1980). It tolerates oxygen concentration <1 mg L1, being able to 

survive for a short time at 0 mg L-1oxygen (Mills and Mann 1983, Morrissy and Cassells 1992).

 Yabbies are commonly found on muddy or silted bottoms and are rarely found in clear water habitats; they 

seem to prefer water with moderate levels of turbidity. Possibly, muddy waters afford some protection from 

predators such as fish and birds, giving the yabby a better chance of survival (Withnall 2000).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 The Great Lakes provide an abundant habitat that is suitable for the survival, development, and reproduction of 

this species.

 The Yabby’s ideal habitat consists of high oxygen levels and vegetation; they are most likely to be found in 

swamps, streams, rivers, and dams (Withnall 2000).

 This species prefers muddy water and does not need to be fully covered by water unless mating; they require a 

certain water hardness that comes from dissolved calcium (NSW DPI 2013a).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8
1178

 Cherax destructor may not benefit from the environmental differences, but it is known to have a high tolerance 

to a variety of environments. (Allen and Gherardi 2011).

 The extreme temperatures near the Great Lakes may affect the growth of the Yabby during some seasons, but 

their high proliferation would help them survive. They have two spawning events per season and produce 

approximately 1000 eggs per spawn. Reproduction is linked to water temperature, so the spring and summer 

would be ideal seasons (Withnall 2000).

 The Yabby has been the most successful and abundant crayfish in Australian freshwater; it has adapted to the 

cold waters in the mountains as well as the hot waters of central Australia (NSW DPI 2013a).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Cherax destructor is an opportunistic feeder and would be able to find a food source in most environments 

(Withnall 2000).

 The diet of C. destructor is not fully known, but it is known to be an omnivorous species that feeds on plants, 

detritus, and some arthopods (Allen and Gherardi 2011).

 Their diet also switches according to climate. During summer seasons, they tend to eat fish, and in the winter, 

they eat plants and detritus (USFWS 2014d).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0
1179

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 At the time of this assessment, C. destructor does not have any known organisms that is depends on.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is not currently a species established in the Great Lakes region known to help establish the Yabby.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%
1180

 Cherax destructor prefers to settle in the mud or bottoms of muddy water which acts as protection and aids in 

survival (Withnall 2000).

 Predators are aquatic birds such as Cormorants, Herons and the Ibis, and fish species such as Murray Cod and 

Callop. Carp compete with Yabbies for food (Withnall 2000).

 All three bird species can be found in the Great Lakes region (MSG 2007).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 There have been no introductions of C. destructor in the Great Lakes region.

 While this species is potentially being sold in the United States, there have been no reports of releases.

 There are increased restrictions in areas outside the United States to further prevent their release; in New 

South Wales Australia, it is illegal to release any crayfish into natural waters without government permission 

(NSW DPI 2013a).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

7

 Cherax destructor is naturally found in Australia; it has been found in Victoria, New South Wales, and Southern 

Queensland (USFWS 2014d).

 Its indigenous regions in Australia are South Australia, southern Northern territory, Victoria, and South 

Australia (Gherardi 2007).

 The Yabby was introduced to Western Australia in 1932 by spreading through natural river systems (Gherardi

2007).

 It has been introduced to Switzerland, Austria, Netherlands, England, and Germany (Chucholl 2013).
1181

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 Cherax destructor was first moved out of Australia and introduced to Spain in 1983 for commericial reasons 

and was originally restricted to Spanish waters (Gherardi 2007). 

 Since then, the Yabby has moved throughout Europe and into Africa and was able to become established as a 

wild species (Gherardi 2007).

 As human interest in crayfish increased, so did the spread of the Yabby (Gherardi 2007).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-40%

 Regulations have been set to prohibit species in the Great Lakes; the yabby is prohibited in Illinois, Minnesota, 

and Ohio (GLPANS 2012).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 94

>100 High Adjustments

B. Critical species A*(1- 0%) 94
1182

51-99 Moderate C. Natural enemy B*(1- 10%) 84.6

Control measures C*(1- 50%) 50.8

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

Cherax destructor has the potential for moderate environmental impact if introduced to the Great 

Lakes.

Cherax destructor is not known be toxic, parasitic, or poisonous. There have been cases where C. 

destructor has spread diseases and affected indigenous crayfish species. The crayfish plague in 1859 was 

caused by a parasite, Aphanomyces astaci, which was fatal to all European indigenous crayfish. Yabby 

was a carrier of this parasite (Chucholl 2013). Yabby is also known to carry Thelohania parastaci which 

is a microsporidian disease that causes the destruction of striated and cardiac muscle tissue and eventually 

leads to death of the affected crayfish (Gherardi 2007).

There is little or no evidence to support that Cherax destructor has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Cherax destructor poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or the aesthetic appeal of the areas it inhabits. 

Cherax destructor has the potential for moderate beneficial impact if introduced to the Great Lakes.

Cherax destructor has commercial value but its economic contribution is small. It is sometimes employed 

recreationally, but adds little value to local communities or tourism. 
1183

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Cherax destructor is not known be toxic, parasitic, or poisonous.

 There have been cases where C. destructor has spread diseases and affected indigenous crayfish species.

 The crayfish plague in 1859 was caused by a parasite, Aphanomyces astaci, which was fatal to all 

European indigenous crayfish. The Yabby was a carrier of this parasite. (Chucholl 2013)

 The Yabby is also known to carry Thelohania parastaci which is a microsporidian disease that causes the 

destruction of striated and cardiac muscle tissue and eventually leads to death of the affected crayfish. 

(Gherardi 2007)

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 C. destructor has the ability to switch trophic positions, when an otherwise abundant, high protein food sources 

(i.e. fish) becomes limited. Furthermore, the ability of C. destructor to switch from a diet of fish in summer to a 

predominantly herbaceous/detrital diet in winter suggests that it may compete for food resources with the other 

smaller native freshwater crayfishes in Australia (Beatty 2005).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

1 
1184

effects of which have not been widespread or severe

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 Burrowing activity of the Yabby may increase turbidity.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 Burrowing activity of the Yabby may increase erosion/siltation.

Environmental Impact Total 2

Total Unknowns (U) 3
1185

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1 √

Not significantly 0

Unknown U

 The burrowing behaviour of C. destructor is a cause for concern for farmers. Yabbies are capable of digging 

very deep burrows which can be 50 cm to 2 meters deep depending on the species. Burrows are connected by 

access shafts to the water. In the event of the water drying up, the yabby is able to survive over summer in the 

burrows. Unfortunately, this behaviour may also destroy the integrity of dam walls causing problems for 

farmers (Withnall 2000).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √
1186

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2 Unknown
1187

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 This is a popular species for aquaculture for purposes of eating and using in aquaria (NSW DPI 2013a).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This is a popular species for recreational “catching” for purposes of eating and using as bait or in aquaria 

(NSW DPI 2013a).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

1
1188

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1189

A.9 Crustaceans - Crabs

Scientific Name: Rhithropanopeus harrisii

(Gould, 1841)

Common Name: Harris Mud Crab, Estuarine Mud Crab, Dwarf Mud Crab, White-fingered (or whitetipped) Mud Crab

Synonyms: Pilumnus tridentatus Maitland, 1874; Heteropanope tridentata De Man, 1892; Pilumnopeus 

tridentatus Balss,1933; Pilumnus harrisii Gould, 1841; Rhithropanopeus harrisii ssp. tridentatus

Buitendijk & Holthuis, 1949; Panopeus wurdemannii Gibbes, 1850

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Low

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic Shipping: Moderate

Rhithropanopeus harrisii has a moderate probability of introduction to the Great Lakes 

(Confidence level: High).

Potential pathway(s) of introduction: Hitchhiking/Fouling, Transoceanic Shipping

Introduction of Gulf of Mexico populations of Rhithropanopeus harrisii into inland Texas reservoirs may 

have occurred through bait bucket or accidental angler and boater release (Howells 2001).

Rhithropanopeus harrisii has been found in ten freshwater impoundments in Texas (Boyle et al. 

2010). While this species could arrive in the Great Lakes via ballast or hitchhiking/fouling, it seems more 

likely that a population able to establish in freshwater would arrive via hitchhiking/fouling from the 

Texan reservoirs, as these populations are already adapted to freshwater. While recreational boat traffic 

does occur between Texas and the Great Lakes (Davidson pers. observation), the frequency would likely 

be very low given the distance.

A gravid R. harrisii female has been found in ships arriving from coastal traffic to east Canadian ports 

following mid-ocean ballast exchange (Briski et al. 2012). Female R. harrisii individuals are able to 

release fertilized egg clutches up to four separate times following a single mating. Multiple spawnings 

may also assure continued reproduction under stressful or hazardous conditions, when mating activity 

may be reduced (Morgan et al. 1983). Rhithropanopeus harrisii larvae can detect vertical gradients in 

temperature, salinity, and hydrostatic pressure, which are used for depth regulation and avoidance of 
1190

adverse environmental conditions (Forward 2009). Thus this species is highly like to survive transit in 

ballast tanks and reproduce enroute.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Introduction of Gulf of Mexico populations of R. harrisii into inland Texas reservoirs may have occurred 

through bait bucket or accidental angler and boater release (Howells 2001).

 Boaters travel between Texas and Great Lakes waters (Davidson pers. observation).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5
1191

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 Rhithropanopeus harrisii has been found in ten freshwater impoundments in Texas (Boyle et al. 2010).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal Score x 0.25
1192

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U
1193

 A gravid R. harrisii female has been found in ships arriving from coastal traffic to east Canadian ports 

following mid-ocean ballast exchange (Briski et al. 2012).

 Female R. harrisii individuals are able to release fertilized egg clutches up to four separate times following a 

single mating. Multiple spawnings may also assure continued reproduction under stressful or hazardous 

conditions, when mating activity may be reduced (Morgan et al. 1983).

 Rhithropanopeus harrisii larvae can detect vertical gradients in temperature, salinity, and hydrostatic pressure, 

which are used for depth regulation and avoidance of adverse environmental conditions (Forward 2009).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 The native range of R. harrisii extends along the Atlantic coast of North America, from the southern Gulf of 

Saint Lawrence, Canada to Veracruz in the Gulf of Mexico (Williams 1984).

 Rhithropanopeus harrisii is present in many European waters, including the Baltic Sea and North Sea (GISD

2008).
1194

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Rhithropanopeus harrisii has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Vector Potential Scorecard

 

Vector

Raw

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0.5 50 Moderate

Total Unknowns (U) 0 Confidence Level High
1195

This species inhabits areas with climates similar to the Great Lakes (e.g., mid-Atlantic and northern 

European climates have hot summers, cold winters and significant rainfall). Water temperatures in 

inhabited areas include the range of Great Lakes temperatures, e.g., highs in the Panama Canal (up to 

30.3°C) (Roche et al. 2009), and lows in the Miramichi Estuary, Canada (near freezing for up to six 

months of the year) (Chadwick 1995). While much previous literature describes Rhithropanopeus 

harrisii as intolerant of freshwater conditions, populations have recently been found in near-freshwater 

conditions. This species is likely to tolerate suboptimal conditions including a wide range of salinity, 

temperature and oxygen depletion. This species inhabits polluted areas, including the Baltic Sea, which is 

heavily polluted (though improvements have been made) (Glasby and Szefer 1998). The ability to tolerate 

high salinities may give R. harrisii a competitive edge over native species in areas polluted by road 

salt. R. harrisii is able to reproduce when the water temperature is above 14°C (Turoboyski 1973). The 

Mud Crab thrives on a diverse diet of plants and animals, including Zebra Mussels (Dreissena 

polymorpha) and will likely find plenty to eat in the Great Lakes ecosystems.

R. harrisii is parasitized and sterilized by the rhizocephalan parasite Loxothylaxus panopaei in saline 

environments. Larvae of L. panopaei survive poorly at salinities below 10 ppt (Forward 1991, Reisser and 

Forward 1991) which may release the freshwater populations from control by this parasite.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 While much previous literature describes R. harrisii as intolerant of freshwater conditions, populations have 

recently been found in near-freshwater conditions.

 R. harrisii populations have been found well-established (metamorphosis and reproduction) in Tradinghouse 

Creek reservoir (Texas), which has a salinity of 0.4-0.5 ppt (Boyle et al. 2010).

 High percentage of eggs from these Texan reservoirs hatched in lab at salinity of 0.5 ppt (Richey 2004).

 R. harrisii is well established and successfully reproducing in the Northern Lagoon (Panama), with constantly 

recorded salinities between 0.4% and 0.6% (Roche et al. 2009).

 Reasons for freshwater tolerance (where none had been found before) include (Boyle et al. 2010): 

1. Source population is more tolerant to low salinity. Texas populations may be from Florida and/or 

Gulf of Mexico populations, which show greater tolerance to low salinity (Richey 2004). 

Louisiana populations are genetically distinct from American East Coast and Europe populations 

(Projecto-Garcia et al. 2010).

2. Tolerance to freshwater is a recent result of natural selection, based on the ability of a small 

number of individuals. This ability was not detected previously in laboratory studies due to small 

sample size.
1196

 Wurtz and Roback (1955) found species in rivers emptying into the Gulf of Mexico in salinities from 0.006 

to 22.6 ppt (Costlow et al. 1966).

 Larvae develop in salinities up to 40 ppt (Costlow et al. 1966).

 In its introduced range in Poland, R. harrisii is able to reproduce when the water temperature is above 

14°C (Turoboyski 1973); larvae develop at temperatures below 30°C (Costlow et al. 1966). 

 Since zoeae are retained in estuaries, they develop in a highly variable environment. Accordingly, they can 

complete development in a very wide range of temperatures and salinities (Forward 2009).

 Reid et al. (2007) and Klein et al. (2010) measured rapid declines in dissolved oxygen concentration inside 

ballast tanks to 2 mg/L within 5 to 7 days, with 90% of initial oxygen content lost within 10 days at 

temperatures above 20°C. A gravid R. harrisii female survived 5 days in ballast water with temperatures 

often over 20°C (Briski et al. 2012), thus indicating this species is likely to tolerate suboptimal conditions.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Turoboyski (1973) reported that populations in the Vistula River, Poland could survive winter temperatures 

below 1°C and could even survive being frozen in ice for a short time. This is not particularly unusual as 

populations at the northern edge of their natural range in the Miramichi Estuary, Canada are exposed to salt 

water near freezing for up to six months of the year (Chadwick 1995, Fowler et al. 2013).

 Has been recorded in water with DO of 0.554 mg/L (Turoboyski 1973).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 The mud crab feeds on both plants and animals, the proportions between these two major components differing 

between areas (Kujawa 1957, Turoboyski 1973). For example, while the mud crabs dwelling in the Vistula 

Lagoon fed mainly on Dreissena polymorpha, the major food items in the Dead Vistula included Nereis 

diversicolor, Mytilus edulis, and Cordylophora caspia, as well as the algae Cladophora sp. and Enteromorpha

sp. The Odra estuary population was found to feed mainly on detritus, which accounted for 61.1 % of the gut 

content; the animal food items, making up 12.9% of the contents, contained remains of appendages of copepods 

and insects, as well as fragments of the Blue Mussel (M. edulis) and the Zebra Mussel (D. polymorpha) 

(Czerniejewski and Rybczyk 2008).
1197

 The type of food consumed has been found to be significantly (P<0.05) dependent on the locality inhabited: the 

greater the biodiversity of the habitat, the richer the dietary composition. In Baltic coastal waters this species 

feeds on detritus, and also on animal and plant matter. Remains of Chlorophyta, Amphipoda, Ostracoda, 

Polychaeta, Gastropoda and Bivalvia were found in the stomachs of the specimens analysed (Hegele-Drywa 

and Normant 2009).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

 R. harrisii one of the most important benthic species in the Vistula lagoon (Baltic Sea), where it is non-native 

(Ezhova et al. 2005). 

 The R. harrisii appears to occupy the same niche as crayfish, which means it could be easily displaced if R. 

harrisii is the better competitor. Observations over the past three summers at Possum Kingdom have indicated 

an abundance of crabs and a paucity of crayfish (Richey 2004).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

5

 Typically produces 1000-4000 eggs, up to 7500 eggs per clutch (Morgan et al. 1983).

 For 5 species in infraorder Brachyura (Rodgers et al. 2011):

o Eurypanopeus depressus: 2,263 eggs/brood (SE 1,021); 2 broods/year; 4.5 x 103eggs/year

o R. harrisii: 1,901 eggs/brood (SE 532); 4 broods/year; 7.6 x 103 eggs/year

o Pachygrapsus transversus: 4,935 eggs/brood (SE 908); unknown broods/year and eggs/year 

o Uca beebei: 4,028 eggs/brood (SE 1,192); 5 broods/year; 2.0 x 104 eggs/year

o U. terpsichores: 6,016 eggs/brood (SE 966); 5 broods/year; 3.0 x 104eggs/year
1198

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

5

 Females of R. harrisii are able to release fertilized egg clutches up to four separate times following a single 

mating. Multiple spawnings may also assure continued reproduction under stressful or hazardous conditions, 

when mating activity may be reduced. (Morgan et al. 1983).

 R. harrisii is parasitized and sterilized by the rhizocephalan parasite Loxothylaxus panopaei in saline 

environments. Larvae of L. panopaei survive poorly at salinities below 10 ppt (Forward 2009, Reisser and 

Forward 1991).

 After R. harrisii megalopae settle out in a suitable habitat, they quickly grow to reproductive size. R. harrisii is 

physiologically able to reproduce by the fifth crab stage (Payen 1975), which takes only a month to attain after 

metamorphosis at 25°C (Morgan et al. 1983).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 This species inhabits areas with climates similar to the Great Lakes. E.g., mid-Atlantic and northern European 

climates have hot summers, cold winters and significant rainfall.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?
1199

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 This species inhabits polluted areas, including the Baltic Sea, which is heavily polluted (though improvements 

have been made) (Glasby and Szefer 1998). 

 Water temperatures in inhabited areas of R. harrisii include the range of Great Lakes temperatures, e.g., highs 

in the Panama Canal (up to 30.3°C) (Roche et al. 2009), and lows in the Miramichi Estuary, Canada (near 

freezing for up to six months of the year) (Chadwick 1995).

 Lives in salinities of 0.4-0.5 ppt (Boyle et al. 2010).

 Live in pH range of 5.4-7.8 (Roche et al. 2009).

 Baltic Sea has received heavy nutrient inputs from agricultural land and is mesotrophic (Glasby and Szefer 

1998); native habitat includes the eutrophic Gulf of Mexico.

 Inhabits areas with no current (Texan reservoirs) and areas with current (Eider, Elbe, Ems, and Weser Rivers) 

(Jensen 2010). 

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 In Texan reservoirs, habitat of R. harrisii includes sand and gravel mix with a few stones for cover (Richey 

2004).

 In the Baltic Sea, this species can opportunistically occupy extremely diverse habitats, such as shafts of dead 

marsh plants, self-made burrows in muddy bottoms, under small stones along the shore, and the brown algae 

Fucus vesiculosus in hard bottoms sometimes exposed to heavy wind and waves, up to 37 m depth (Fowler et al. 

2013).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6
1200

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 This species is highly adaptable, and can survive in a wide range of temperatures, as well as salinities. The 

ability to tolerate high salinities may give R. harrisii a competitive edge to native species.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 R. harrisii feeds on both plants and animals, the proportions between these two major components differing 

between areas (Kujawa 1957, Turoboyski 1973). For example, while R. harrisii dwelling in the Vistula Lagoon 

fed mainly on Dreissena polymorpha, the major food items in the Dead Vistula included Nereis diversicolor, 

Mytilus edulis, and Cordylophora caspia, as well as the algae Cladophora sp. and Enteromorpha sp. The Odra 

estuary population was found to feed mainly on detritus, which accounted for 61.1 % of the gut content; the 

animal food items, making up 12.9% of the contents, contained remains of appendages of copepods and insects, 

as well as fragments of the Blue Mussel (M. edulis) and the Zebra Mussel (D. polymorpha) (Czerniejewski and 

Rybczyk 2008).

 The type of food consumed has been found to be significantly (P<0.05) dependent on the locality inhabited: the 

greater the biodiversity of the habitat, the richer the dietary composition. In Baltic coastal waters this species 

feeds on detritus, and also on animal and plant matter. Remains of Chlorophyta, Amphipoda, Ostracoda, 

Polychaeta, Gastropoda, and Bivalvia were found in the stomachs of the specimens analysed (Hegele-Drywa 

and Normant 2009).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9
1201

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There are no critical species required by R. harrisii.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

5

 R. harrisii is significantly more abundant in non-native Phragmites australis than in native Spartina alterniflora 

(Able and Hagan 2000).

 In 2001-2004, large numbers of young crabs have been recorded inhabiting aggregations of Dreissena 

polymorpha in the Vistula Lagoon. Colonies of this common Ponto-Caspian bivalve invader apparently serve as 

a perfect hiding place for these crabs (Grabowski et al. 2005).

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)
1202

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 Larvae have several safeguards against predation: they undergo nocturnal diel vertical migration (DVM) and 

have a shadow response to avoid encountering predators, and they bear long spines as a deterrent (Forward 

2009).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 While this species could arrive via ballast or hitchhiking/fouling, it seems more likely that a population able to 

establish in freshwater would arrive via hitchhiking/fouling from the Texan reservoirs, as these populations are 

already adapted to freshwater. While recreational boat traffic does occur between Texas and the Great Lakes 

(Davidson pers. observation), the frequency would likely be very low given the distance.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0
1203

Unknown U

9

 The native range of R. harrisii extends along the Atlantic coast of North America, from the southern Gulf of 

Saint Lawrence, Canada to Veracruz in the Gulf of Mexico (Williams 1984).

 R. harrisii has invaded over 20 countries, two oceans, ten seas, and ten freshwater inland reservoirs across four 

continents, which span over 45 degrees of latitude, most likely due to anthropogenic means (Roche and Torchin 

2007).

 Adriatic Sea, Aral Sea, Azerbaijan, Azov Sea, Baltic Sea, Belgium, Black Sea, Britain, Bulgaria, Caspian Sea, 

Denmark, France, Germany, Iran, Italy, Kazakhstan. Lithuania, Mediterranean Sea, Netherlands, North Sea, 

Panama Canal, Poland, Portugal, Romania, Russia, Spain, Tunisia, Turkmenistan, Ukraine, Uzbekistan, 

Pacific Coast and Texas lakes of United States (GISD 2008).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 The first European record of R. harrisii dates back to before 1874 when it was described as a new species from 

the Zuiderzee in the Netherlands (Wolff 2005). The first German record is from 1936 in the Kiel Canal 

connecting the North and Baltic Seas (Gollasch and Nehring 2006, Nehring 2000). It first appeared on the 

Baltic coast of Germany between 1948 and 1950. Since then it has spread to estuaries of several rivers, 

including the Eider, Elbe, Ems, Weser and on a few occasions even the German section of the Rhine. The 

increase in abundance has taken place chiefly during the 1990s (Nehring 2000). There are a few Danish 

records from the harbour of Copenhagen in 1953 and 1954 (Rasmussen 1958). The next record is from 2008, 

just south of Copenhagen, but recently R. harrisii has become established in south-eastern Denmark (Olesen 

and Tendal 2009). In the Baltic it has been found in Poland since 1951 (Grabowski et al. 2005, Normant et al.

2004) and in Lithuania since 2000 (Bacevičius and Gasiūnaitė 2008). In France it first appeared in 1955-1956 

(Goulletquer et al. 2002), in Portugal in 1989 (Gonçalves et al. 1995), and in Spain in 1990 (Roche and 

Torchin 2007). In the United Kingdom, R. harrisii only occurs in one locality, Cardiff Docks in Wales, where it 

was first found in 1996 (Eno et al. 1997, Jensen 2010).

 This species was first reported in Finland in 2009 from the archipelago close to Turku and has been found from 

82 locations within a 30 km radius in 2012 (Fowler et al. 2013).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. -50% total 
1204

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

 There are no existing control measures to prevent establishment or spread of this species.

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 105

>100 High Adjustments

B. Critical species A*(1- 0%) 105

51-99 Moderate C. Natural enemy B*(1- 0%) 105

Control measures C*(1- 0%) 105

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

There is little or no evidence to support that Rhithropanopeus harrisi has the potential for 

significant environmental impacts if introduced to the Great Lakes.
1205

R. harrisii commonly carry strains of the white spot baculovirus (Payen and Bonami 1979) While impact 

studies are scarce, Fowler et al. (2013) predicts that regarding the introduction of this species in Finland, 

alterations to the benthic community are expected, as it is a completely new functional species to that 

area. The Mud Crab appears to occupy the same niche as crayfish, which means crayfish species could be 

displaced if the mud crab is the better competitor. Observations from 2000-2003 at Possum Kingdom 

have indicated an abundance of crabs and a paucity of crayfish (Richey 2004). Declines in Aral Sea 

biodiversity are in part attributed to introduction of alien species such as R. harrisii (Aladin and Potts 

1992). A number of coastal mud crabs (Xanthidae, Panopew and other genera) are reported as major 

predators on young oysters and hard clams (Gosner et al. 1979). R. harrisii may have a negative impact 

upon local unionid populations, but this remains to be determined (Howells 1992). R. harrisii likely plays 

a minor role in reduction of Crassostrea virginica spat (Kulp et al. 2011). Along with M. viridis and P. 

antipodarum, R. harrisii has contributed to habitat modification (Ezhova et al. 2005). 

Current research on the potential for socio-economic impacts to result from Rhithropanopeus 

harrisi if introduced to the Great lakes is inadequate to support proper assessment.

In Texas, the crab has become very abundant in almost freshwater reservoirs and is reported to foul PVC 

intakes in lakeside homes (Richey 2004). In the Caspian Sea, where it has reached very high densities, the 

crab causes economic loss to fishermen by spoiling fishes in gill nets (Zaitsev and Öztürk 2001). 

Current research on the potential for beneficial impacts to result from Rhithropanopeus harrisi if 

introduced to the Great lakes is inadequate to support proper assessment.

R. harrisii larvae have been used for a variety of toxicology studies to identify lethal and sublethal 

concentrations. The attributes of R. harrisii for these studies are that (1) the larvae are easy to rear in the 

laboratory with low mortality; (2) they are robust and can complete development in a wide range of 

temperatures and salinities; and (3) since they are retained in estuaries, they would be exposed to land 

runoff that could contain pesticides, herbicides, and other potential toxicants (Forward 2009). This species 

can consume Dreissena polymorpha (Kujawa 1957) but the degree of its potential impact on Dreissenid 

populations is unknown.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 R. harrisii commonly carry strains of the white spot baculovirus (Payen and Bonami 1979).
1206

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 While impact studies are scarce, Fowler et al. (2013) predicts that regarding the introduction of this species in 

Finland, alterations to the benthic community are expected, as it is a completely new functional species to that

area.

 The Mud Crab appears to occupy the same niche as crayfish, which means it could be displaced if the mud crab 

is the better competitor. Observations from 2000-2003 at Possum Kingdom have indicated an abundance of 

crabs and a paucity of crayfish (Richey 2004).

 Declines in Aral Sea biodiversity are in part attributed to introduction of alien species such as R. harrisii

(Aladin and Potts 1992).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 A number of coastal mud crabs (Xanthidae, Panopew and other genera) are reported as major predators on 

young oysters and hard clams (Gosner 1979). R. harrisii may have a negative impact upon local unionid 

populations, but this remains to be determined (Howells 1992).

 R. harrisii likely plays a minor role in reduction of Crassostrea virginica spat (Kulp et al. 2011).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U
1207

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 Along with M. viridis and P. antipodarum, R. harrisii has contributed to habitat modification (Ezhova et al. 

2005).

Environmental Impact Total 0

Total Unknowns (U) 4

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1208

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1√

Not significantly 0

Unknown U

 In Texas, the crab has become very abundant in almost freshwater reservoirs and is reported to foul PVC 

intakes in lakeside homes (Richey 2004).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 In the Caspian Sea, where it has reached very high densities, the crab causes economic loss to fishermen by 

spoiling fishes in gill nets (Zaitsev and Öztürk 2001). 
1209

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
1210

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 R. harrisii larvae have been used for a variety of toxicology studies to identify lethal and sublethal 

concentrations. The attributes of R. harrisii for these studies are that (1) the larvae are easy to rear in the 

laboratory with low mortality; (2) they are robust and can complete development in a wide range of 

temperatures and salinities; and (3) since they are retained in estuaries, they would be exposed to land runoff 

that could contain pesticides, herbicides, and other potential toxicants (Forward 2009).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1
1211

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1212

Scientific Name: Sinelobus stanfordi

(Richardson, 1901)

Common Name:

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Low

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate

Sinelobus standfordi has a moderate probability of introduction to the Great Lakes (Confidence 

level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Transport in ballast water is a likely vector responsible for the arrival of S. stanfordi in the Netherlands 

(van Haaren and Soors 2009). Sinelobus stanfordi has been collected in Argentina, Brazil, Uruguay, West 

Indies, Florida (Coral Gables Waterway), Galapagos, Sri Lanka, Sudan, South Africa (Gardiner 1975); 

Mexico (Hendrickx and Ibarra 2008); British Columbia (Levings and Rafi 1978); Dutch and Belgian 

North Sea coast, including port of Antwerp (van Haaren and Soors 2009); San Francisco Bay and delta 

(Cohen and Carlton 1995); Lower Colombia River and Coos Bay, Oregon (Ruiz et al. 2000, Sytsma et al. 

2004), South Carolina (SC DNR 2008), and Washington (Joyce 2005, van Haaren and Soors 2009).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
1213

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Fouling is a likely vector responsible for the arrival of S. stanfordi in the Netherlands (van Haaren and Soors 

2009).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 Sinelobus stanfordi is present in Florida (Coral Gables Waterway) (Gardiner 1975); San Francisco Bay and 

delta (Cohen and Carlton 1995); Lower Colombia River and Coos Bay, Oregon (Ruiz et al. 2000, Sytsma et al. 

2004), South Carolina (South Carolina Department of Natural Resources 2008), and Washington (Joyce 2005, 

van Haaren and Soors 2009).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
1214

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
1215

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100 √

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Transport in ballast water is a likely vector responsible for the arrival of S. stanfordi in the Netherlands (van 

Haaren and Soors 2009).

 Sinelobus stanfordi can withstand huge fluctuations in salinity. This species is able to survive these fluctuations 

presumably by active control of the osmotic concentration of the body fluids (Kikuchi and Matsumasa 1993, van 

Haaren and Soors 2009).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great Score x 0.1
1216

Lakes nor in ports in direct trade with the Great Lakes.

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Sinelobus stanfordi has been collected in Argentina, Brazil, Uruguay, West Indies, Florida (Coral Gables 

Waterway), Galapagos, Sri Lanka, Sudan, South Africa (Gardiner 1975); Mexico (Hendrickx and Ibarra 2008); 

British Columbia (Levings and Rafi 1978); Dutch and Belgian North Sea coast, including port of Antwerp (van 

Haaren and Soors 2009); San Francisco Bay and delta (Cohen and Carlton 1995); Lower Colombia River and 

Coos Bay, Oregon (Ruiz et al. 2000, Sytsma et al. 2004), South Carolina (SC DNR 2008), and Washington 

(Joyce 2005, van Haaren and Soors 2009).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

100 x 0.5 50 Moderate

Total Unknowns (U) 0 Confidence Level High
1217

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Sinelobus standfordi has a low probability of establishment if introduced to the Great Lakes 

(Confidence level: Low).

Sinelobus stanfordi is in Antwerp, which is a major shipping/industrial area, and likely has high 

population levels there. If individuals found their way into ballast water, ballast exchange would eliminate 

most individuals from ballast water. Also, traffic from United States water bodies with this species is low 

to the Great Lakes, so the inoculation via fouling would be low.

First recorded in east equatorial Pacific (Gardiner 1975). Sinelobus stanfordi has been collected in 

Argentina, Brazil, Uruguay, West Indies, Florida (Coral Gables Waterway), Galapagos, Sri Lanka, Sudan, 

South Africa (Gardiner 1975), Mexico (Hendrickx and Ibarra 2008), British Columbia (Levings and Rafi 

1978), Dutch and Belgian North Sea coast, including port of Antwerp (van Haaren and Soors 2009), San 

Fransisco Bay and delta (Cohen and Carlton 1995); Lower Colombia River and Coos Bay, Oregon 

(Sytsma et al. 2004, Ruiz et al. 2000), South Carolina (South Carolina Department of Natural Resources 

2008), and Washington (Joyce 2005, van Haaren and Soors 2009). Only one study documents the 

presence of this species specifically as an invasive population (van Haaren and Soors 2009); thus, spread 

is not known.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 Sinelobus stanfordi tolerates fresh to very saline water, 0-52 ppt (Gardiner 1975).

 This species is found in Arcturus Lake (Galapagos), with has very low DO at 10m, nearly no DO at 25m and is 

exceedingly eutrophic (Gardiner 1975).

 In Netherlands Sinelobus stanfordi is found in O2% from 61-102%; found in O2 as low as 5.8 mg/L (van Haaren 

and Soors 2009).
1218

 This species is found in sediment with temperatures of -2C-23.5C (Levings and Rafi 1978). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Sinelobus stanfordi is found in sediment with temperatures of -2C-23.5C (Levings and Rafi 1978). 

 Sinelobus stanfordi is found in Arcturus Lake (Galapagos), with has very low DO at 10m, nearly no DO at 25m 

(Gardiner 1975).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

U

 A paucity of data exists for this species’ diet.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
1219

Unknown U

U

 In Fraser River estuary (British Columbia), densities of 17,400 individuals/0.25m2(Levings and Rafi 1978).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

5

 Female of this species have been observed with 57 eggs (Gardiner 1975).

 For family Tanaidacea:

o Mean number of eggs per female of Tanais dulongii was 47.2 (Rumbold et al. 2012).

o Mean number of eggs per female of Monokalliapseudes schubarti was 37 (Freitas-Júnior et al. 

2013).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

0

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9
1220

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

3

 While the number of purely freshwater populations of this species is low, one location has been in Japan, where 

the winters are cold and the precipitation is relatively high. Other estuarine populations (e.g., the Netherlands) 

are known from areas with seasonal weather, including cold winters.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

U

 This species is found in freshwater (Gardiner 1975).

 Sinelobus stanfordi is found in Arcturus Lake (Galapagos), which is exceedingly eutrophic (Gardiner 1975).

 This species is found in sediment with temperatures of -2C-23.5C (Levings and Rafi 1978). 

 This species is found in Antwerp, which is a major shipping/industrial area and likely has high levels of 

population (van Haaren and Soors 2009).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 Sinelobus stanfordi is a benthic species, found in detritus among mangroves, on fine filamentous algae; 

constructs tubes on hard or soft bottoms, and on plants (Gardiner 1975).

 This species has been found in stony and artificial substrate in the Antwerp harbor; prefers hard substrate (van 

Haaren and Soors 2009).
1221

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 Sinelobus stanfordi is tolerant of warmer waters, e.g., collected in Argentina, Brazil, Uruguay, West Indies, 

Florida (Coral Gables Waterway), Galapagos, Sri Lanka, Sudan, South Africa (Gardiner 1975); Mexico 

(Hendrickx and Ibarra 2008); British Columbia (Levings and Rafi 1978).

 This species is tolerant of a range of salinities.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

U

 A paucity of data exists for this species’ diet.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9
1222

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

U

 A paucity of data exists for this species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)
1223

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

 As a small benthic species Sinelobus stanfordi is likely to be preyed upon. But has established in a variety of 

locations, so not likely to be impeded by predation.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 Ballast exchange would eliminate most individuals from ballast water. Also, traffic from United States water 

bodies with this species is low to the Great Lakes, so the inocula via fouling would be low, as well.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 This species was first recorded in east equatorial Pacific (Gardiner 1975).

 This species has been collected in Argentina, Brazil, Uruguay, West Indies, Florida (Coral Gables Waterway), 

Galapagos, Sri Lanka, Sudan, South Africa (Gardiner 1975); Mexico (Hendrickx and Ibarra 2008); British 

Columbia (Levings and Rafi 1978); Dutch and Belgian North Sea coast, including port of Antwerp (van Haaren 

and Soors 2009); San Fransisco Bay and delta (Cohen and Carlton 1995); Lower Colombia River and Coos 
1224

Bay, Oregon (Sytsma et al. 2004, Ruiz et al. 2000), South Carolina (South Carolina Department of Natural 

Resources 2008) and Washington (Joyce 2005, van Haaren and Soors 2009).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

 Only one study documents the presence of this species specifically as an invasive population (van Haaren and 

Soors 2009); thus, spread is not known.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 50

>100 High Adjustments

B. Critical species A*(1- 0%) 50

51-99 Moderate C. Natural enemy B*(1- 0%) 45

Control measures C*(1- 0%) 45
1225

0-50 Low Potential for Establishment Low

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 6

2-5 Moderate 

6-9 Low

Confidence Level Low

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Low

Socio-Economic: Low

Beneficial: Low

Current research on the potential environmental impacts to result from Sinelobus stanfordi if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Sinelobus stanfordi poses a threat to 

other species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this species alters the physical components of the ecosystem.

There is little or no evidence to support that Sinelobus stanfordi has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

It has not been reported that Sinelobus stanfordi poses a threat to human health or water quality. There is 

no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities 

and associated tourism, or aesthetic appeals of the areas it inhabits.

There is little or no evidence to support that Sinelobus stanfordi has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Sinelobus stanfordi can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.
1226

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 As a small benthic crustacean, this species is not likely to pose a hazard to the health of native species.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

 A paucity of data exists for this species.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

 As a small benthic crustacean, this species is not likely to alter predator-prey relationships.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 1 
1227

individual level

Not significantly 0 √

Unknown U

 As a small benthic crustacean, this species is not likely to affect any native populations genetically..

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

 As a small benthic crustacean, this species is not likely to negatively affect water quality.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

 As a small benthic crustacean, this species is not likely to alter the physical eocsystem.

Environmental Impact Total 0

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
1228

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U
1229

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
1230

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √
1231

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 There is no evience that Sinelobus stanfordi is utilized as a food source for juvenile salmonids at estuarine 

environments (Levings and Rafi 1978).

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1232

A.10 Platyhelminthes

Scientific Name: Leyogonimus polyoon

Linstow, 1887

Common Name: Trematode Flatworm

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Moderate

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Leyogonimus polyoon has a moderate probability of introduction to the Great Lakes (Confidence 

level: Moderate).

Potential pathway(s) of introduction: Hitchhiking/Fouling

Introduction of L. polyoon to North America could have resulted from migration of an infected coot from

Europe to Canada and then to Wisconsin (Slota et al. 1998). Spread to the Great Lakes could occur via 

migration of infected birds from Wisconsin or Minnesota to the Great Lakes and subsequent transmission 

of the parasite to previously uninfected faucet snails. R. Cole (pers. comm.) notes that this parasite likely 

infects other gallinules, which also would also contribute to its spread potential. 

Infected Faucet Snails attached to boats or other equipment could also transport this parasite (Cole and 

Jankowski 2007).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100
1233

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 The parasite L. polyoon is dependent on Faucet Snails (Bithynia tentaculata) and aquatic insects, such as 

trichopterans (caddisflies) and odonates (dragonflies and damselflies), as its intermediate hosts and coots as its 

definitive host (Cole 2001, Cole and Franson 2006, Cole and Jankowski 2007). These species are found in 

several lakes and rivers in some Great Lakes states, as well as in the Great Lakes themselves. 

 Introduction of L. polyoon to North America could have resulted from migration of an infected coot from 

Europe to Canada and then to Wisconsin (Slota et al. 1998). Spread to the Great Lakes could occur via 

migration of infected birds from Wisconsin or Minnesota to the Great Lakes and subsequent transmission of the 

parasite to previously uninfected faucet snails. R. Cole (pers. comm.) notes that this parasite likely infects other 

gallinules, which also would also contribute to its spread potential. 

 Infected Faucet Snails attached to boats or other equipment could also transport this parasite (Cole and 

Jankowski 2007).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5 

√

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U
1234

 Leyogonimus polyoon is established in several water bodies in the upper mid-western United States, including 

Lake Winnibigoshish, MN and Lake Butte des Morts, Lake Onalaska, Shewano Lake, and Lake Winneconne, WI 

(Cole 2001, Cole and Franson 2006, Cole and Jankowski 2007). The geographic range of this species is 

predicted to be limited to the Great Lakes basin (Cole and Franson 2006).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal Score x 0.25
1235

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U √
1236

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0 √

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.5 50 Moderate

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

U x 0 Unlikely

Total Unknowns (U) 1 Confidence Level Moderate
1237

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Leyogonimus polyoon has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Low).

In North America, L. polyoon is predicted to be geographically restricted to the Great Lakes basin, though 

it is not yet found below ordinary mean high water or directly connecting waters (Cole and Franson 

2006). Establishment in lakes in Minnesota and Wisconsin over the course of a decade suggests that L. 

polyoon could also spread to and overwinter in the Great Lakes, but its environmental parameters are 

uncharacterized. One of its intermediate hosts, the Faucet Snail, is a non-indigenous aquatic snail from 

Eurasia that was introduced into Lake Michigan in 1871; this snail has spread to the Great Lakes region, 

as well as to the mid-Atlantic states and Montana (Invasive Species Program 2011). The trematode’s 

additional required hosts, aquatic insects and American coots, are also widespread in the Great Lakes 

(Cole 2001). Shallow, protected shorelines where birds feed or rest along the Great Lakes may offer more 

of an opportunity for L. polyoon eggs to hatch from released feces and infect B. tentaculata (Cole and 

Jankowski 2007).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

U
1238

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Establishment in lakes in Minnesota and Wisconsin suggests that L. polyoon could also overwinter in the Great 

Lakes.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

3

 Leyogonimus polyoon parasitizes Faucet Snails and aquatic insect larvae. As an adult, it feeds on blood and 

tissue of its host coot (Cole 2001, Cole and Franson 2006, Cole and Jankowski 2007).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U
1239

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

 To complete its complex life history, L. polyoon requires snail and larval insect intermediate hosts and one 

definitive avian (gallinule) host (Cole 2001, Cole and Franson 2006, Cole and Jankowski 2007). All elements 

are present in the Great Lakes region.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0
1240

Unknown U

9

 Leyogonimus polyoon is established in lakes in Minnesota and Wisconsin, where the climate is similar to that 

of the Great Lakes.

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

9

 Leyogonimus polyoon is established in lakes in Minnesota and Wisconsin, where the abiotic environment is 

similar to that of the Great Lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Shallow, protected shorelines where birds feed or rest may offer more of an opportunity for L. polyoon eggs to 

hatch from released feces and infect B. tentaculata (Cole and Jankowski 2007).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 3
1241

better environment for establishment and spread of this species)

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

U

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Faucet Snails, aquatic insect larvae, and coots are all present in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9
1242

 The Faucet Snail, Bithynia tentaculata, a non-indigenous aquatic snail from Eurasia, was introduced into Lake 

Michigan in 1871 and has spread to the mid-Atlantic states, Great Lakes region, Montana, and the Mississippi 

River basin in Lake Winnibigoshish, MN (Invasive Species Program 2011). Aquatic insects and American Coots 

are also widespread in the area (Cole 2001).

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

8

 The Faucet Snail serves as an intermediate host for this trematode and is already established in the Great 

Lakes.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0
1243

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 Before 1996, L. polyoon, a parasitic flatworm infecting coots and moorhens, was reported only from Eastern 

Europe. However, in 1997, large scale mortality of American coots was reported at Shawano Lake, Wisconsin 

and Lake Winnibigoshish, Minnesota. The parasite has also been found in Lake Butte des Morts and Lake 

Winneconne, Wisconsin (Cole 2001, Invasive Species Program 2011).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0
1244

Unknown U

6

 Bird mortality events initially observed in Shawano Lake, WI spread to four additional water bodies in 

Wisconsin and Minnesota in the decade following first detection of this parasite (Cole 2001, Cole and 

Jankowski 2007, Dierauf 2007). It has become a concern that L. polyoon could spread to other locations as 

coots migrate from Shawano Lake and other infected places. 

 Therefore, it has been considered to control spread of L. polyoon by controlling spread of the snail host (Cole 

2001). Infected Faucet Snails attached to boats or other equipment could also transport this parasite (Cole and 

Jankowski 2007).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 75

>100 High Adjustments

B. Critical species A*(1- 0%) 75

51-99 Moderate C. Natural enemy B*(1- 0%) 75

Control measures C*(1- 0%) 75

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 6

2-5 Moderate 
1245

6-9 Low

Confidence Level Low

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

Current research on the potential for environmental impacts to result from Leyogonimus polyoon if 

introduced to the Great Lakes is inadequate to support proper assessment.

Birds infested with L. polyoon develop severe enteritis (intestinal trematodiasis), characterized by gross 

lesions, thickening of intestinal wall, a firm and distended duodenum and jejunum, and fibrinous to 

caseous cores of necrotic debris in the intestines that occlude the lumen (Cole and Franson 2006). 

Symptoms are similar to those of avian cholera (Seely 1999), including body weight loss, weakness, 

lethargy, and death as a result of hemorrhaging, anemia, blood loss, and shock (Cole and Franson 2006, 

Cole and Jankowski 2007). Heavily infected birds may experience difficulty diving and flying (Cole and 

Jankowski 2007).

Previous gallinule infestation in the parasite’s native range was limited to Eurasian Coot and Common 

Moorhen, but through its introduction to North America, L. polyoon was able to infect the native 

American coot and likely infects other gallinules (Cole pers. comm., Cole and Franson 2006). Initial 

dieoffs of over 1,000 American coot in Shewano Lake, located at the headwaters of the Wolf River, WI in 

1996 went undiagnosed until a mass mortality event was observed the following fall (Seely 1999). In 

1997, infestation of L. polyoon killed over 11,000 coot (Cole and Franson 2006, Cole and Friend 1999). 

By 2002, this parasite had caused the death of more than 24,000 birds in northwestern Wisconsin (Cole 

2001). From late October through mid-November 2007, 200 coot on Lake Winnibigoshish in north 

central Minnesota were killed by fluke infestation, including that by L. polyoon (Cole and Jankowski 

2007). Population level effects of these mortality events are unknown.

Current research on the potential for socio-economic impacts to result from Leyogonimus polyoon if 

introduced to the Great Lakes is inadequate to support proper assessment.

Mass bird mortality at infested sites may temporarily impact recreational use and diminish the aesthetic 

value of those areas.

There is little or no evidence to support that Leyogonimus polyoon has the potential for significant 

beneficial effects if introduced to the Great Lakes.

It has not been indicated that Leyogonimus polyoon can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.
1246

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Birds infested with L. polyoon develop severe enteritis (intestinal trematodiasis), characterized by gross 

lesions, thickening of intestinal wall, a firm and distended duodenum and jejunum, and fibrinous to caseous 

cores of necrotic debris in the intestines that occlude the lumen (Cole and Franson 2006). Symptoms are similar 

to those of avian cholera (Seely 2009), including body weight loss, weakness, lethargy, and death as a result of 

hemorrhaging, anemia, blood loss, and shock (Cole and Franson 2006, Cole and Jankowski 2007). Heavily 

infected birds may experience difficulty diving and flying (Cole and Jankowski 2007).

 Initial dieoffs of over 1,000 American Coot in Shewano Lake, located at the headwaters of the Wolf River, WI in 

1996 went undiagnosed until a mass mortality event was observed the following fall (Seely 1999). In 1997, 

infestation of L. polyoon killed over 11,000 coot (Cole and Franson 2006, Cole and Friend 1999). By 2002, this 

parasite had caused the death of more than 24,000 birds in northwestern Wisconsin (Cole 2001). From late 

October through mid-November 2007, 200 coot on Lake Winnibigoshish in north central Minnesota were killed 

by fluke infestation, including that by L. polyoon (Cole and Jankowski 2007).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0 √

Unknown U

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1
1247

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 1
1248

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U
1249

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0

Unknown U √

 Mass bird mortality at infested sites may temporarily impact recreational use of those areas.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0

Unknown U √

 Mass bird mortality at infested sites may temporarily diminish the aesthetic value of those of those areas.

Socio-Economic Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1250

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?
1251

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1252

A.11 Polychaetes

Scientific Name: Hypania invalida

Grube, 1860

Common Name: Freshwater Bristleworm

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Moderate 

Hypania invalida has a moderate probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping (NOBOB vessels)

This species is present throughout the North Sea basin (lower Rhine) and Baltic Sea basin (Grigorovich et 

al. 2003), both origins for high volumes of Great Lakes shipping traffic. Ricciardi and Rasmussen (1998) 

list H. invalida as the only Ponto-Caspian polychaete likely to be transported to the Great Lakes via 

ballast water. Submerged ship pumps have taken in larval specimens without being harmed; these worms 

then rapidly colonized every flume and bowl attached to the inward flow (Norf et al. 2010). With respect 

to the Great Lakes, however, Grigorovich et al. (2003) propose this species has a reduced probability of 

invasion due to the effects of ballast water exchange or flushing. The natural salinity range tolerated by H. 

invalida is 0-12 PSU (Mordukhaĭ-Boltovskoĭ 1964). Therefore, current ballast water regulations (30 ppt 

flushing) are likely to be effective in reducing the probability of introduction to the Great Lakes. 

Additionally, Norf et al. (2010) hypothesize that the potential expansion of this species to the Great Lakes 

is likely to be hindered by ballast water exchange (cf. Gray et al. 2007, Locke et al. 1993).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)
1253

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Hypania invalida is a Ponto-Caspian species that has spread across Europe (Gherardi et al. 2009).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100
1254

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √
1255

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Ricciardi and Rasmussen (1998) list H. invalida as the only Ponto-Caspian polychaete likely to be transported 

to the Great Lakes via ballast water.

 Submerged ship pumps have taken in larval specimens without being harmed; these worms then rapidly 

colonized every flume and bowl attached to the inward flow (Norf et al. 2010).

 Grigorovich et al. (2003) propose H. invalida has a reduced probability of invasion due to the effects of ballast 

water exchange or flushing.

 The natural salinity range tolerated by H. invalida is 0-12 ppt (Mordukhaĭ-Boltovskoĭ 1964). Therefore, current 

ballast water regulations (30 ppt flushing) are likely to be effective in reducing the probability of introduction 

to the Great Lakes.

 Grigorovich et al. (2003) hypothesized that the potential expansion of this species to the Great Lakes is likely to 

be hindered by ballast water exchange (cf. Gray et al. 2007, Locke et al. 1993).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?
1256

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5 

√

Yes, but this species has neither been observed in ballast/fouling ships entering the Great

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 This species is present throughout the North Sea basin (lower Rhine) and Baltic Sea basin (Grigorovich et al. 

2003), both origins for high volumes of Great Lakes shipping traffic.

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 0.5 40 Moderate

Total Unknowns (U) 0 Confidence Level High
1257

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Hypania invalida has a high probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

This species originates in the Ponto-Caspian, a region where climatic conditions are similar to those of the 

Great Lakes. Hypania invalida is able to survive in a wide range of temperature (2-25°C) and salinity (0-

12 PSU) (Mordukhaĭ-Boltovskoĭ 1964), both of which are well within the ranges that occur in the Great 

Lakes. Shorter ice cover duration and warmer water temperatures may also benefit this species by 

lengthening its suitable yearly spawning period; however, if water becomes too warm, this effect may be 

detrimental to survival. For instance, in the summer of 2003, when the lower Rhine experienced the 

highest water temperatures on record (27.8°C max) (Sprokkereef et al. 2008), the population density of 

H. invalida was greatly reduced (Norf et al. 2010). Tolerance to other physiological factors is unknown or 

unreported, as is information on the mechanisms facilitating overwintering within this species’ native 

range (e.g., lower oxygen tolerance limit).

Hypania invalida prefers areas with soft substrate (e.g., silt, clay, fine sand) and current velocities less 

than 0.1 m/s (Norf et al. 2010, Zorić et al. 2011). These preferences make most of the Great Lakes basin 

suitable potential habitat with respect to water motion and bottom composition. Sandy bottoms covered 

with zebra mussel beds also serve as potential habitat, though settlement densities here are typically lower 

than those in soft-bottom communities (Norf et al. 2010, Yakovlev and Yakovleva 2010). This species is 

also able to live at a wide range of water depths (shoreline to 960 m) (Zenkevich 1963).

Hypania invalida is an active filter and deposit feeder, feeding primarily upon diatoms (Gruia and 

Manoleli 1974). Hence, potential food items will likely not limit the distribution of this species within the 

Great Lakes.

Hypania invalida has an extensive invasion history throughout Europe (Gherardi et al. 2009), with a 

spreading pattern that seems to suggest dispersal through a corridor connecting the Danube and Rhine 

rivers. Its dispersal pattern closely follows that of the European invasive isopod Jaera istri (bij de Vaate 

et al. 2002). Panov et al. (2009) described this species as being at high risk for dispersal and establishment 

when introduced to a new area. Rapid expansion throughout European inland waterways has been 

facilitated by both human mediated (ballast water) upstream spread and natural (passive drift) 

downstream spread (Norf et al. 2010, bij de Vaate et al. 2002). Within a few years of introduction to the 

Rhine River, it had dispersed along the entire navigable river stretch (Bernauer and Jansen 2006) and into 

many adjacent waterways, including the Moselle (Devin et al. 2006) and Elbe Rivers (Eggers and Anlauf 

2008).
1258

Females have a high net fecundity due to frequent reproductive events (every 2 weeks) throughout 

maturity; it is estimated that a single female could produce at least 1200 larvae during her lifespan (Norf 

et al. 2010). Many of the sexual and reproductive traits of H. invalida (short generation time, external 

spermcast fertilization, existence of a dispersive larval phase, etc.) reflect attributes that are postulated to 

enhance the invasion success of aquatic invertebrates (bij de Vaate et al. 2002, Bossche et al. 2001, Devin 

and Beisel 2007, Norf et al. 2010, Ricciardi and Rasmussen 1998). The maternal care of offspring 

(brooding) by this species can additionally increase reproductive success by reducing larval mortality 

during early planktonic life stages (McHugh 1993, Schroeder and Hermans 1975). Increased knowledge 

of this species’ reproductive characteristics, has led Norf et al. (2010) to highlight the potential of H. 

invalida to invade the Great Lakes (contrary to earlier suggestions that it is unlikely to disperse 

internationally; cf. Ricciardi and Rasmussen 1998).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Hypania invalida is able to survive in a wide range of temperature (2-25°C) and salinity (0-12 PSU) 

(Mordukhaĭ-Boltovskoĭ 1964), both of which are well within the ranges that occur in the Great Lakes.

 Tolerance to other physiological factors for this species is unknown or unreported.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Due to the climatic similarities between the Great Lakes and Ponto-Caspian regions (Reid and Orlova 2002) 

this species most likely endures similar overwintering conditions in its native range. 
1259

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

9

 Hypania invalida is an active filter and deposit feeder (Gruia and Manoleli 1974), with a non-specific food 

preference (bij de Vaate et al. 2002).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

 There are currently no reported cases of H. invalida outcompeting another species within its invaded range in 

Europe and no predictions available regarding its potential competitive abilities within the Great Lakes.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 Females have a high net fecundity due to frequent reproductive events (every 2 weeks) throughout maturity; it is 

estimated that a single female could produce at least 1200 larvae during her lifespan (Norf et al. 2010).
1260

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

9

 Many of the sexual and reproductive traits of H. invalida (short generation time, external spermcast 

fertilization, etc.) reflect attributes that are postulated to enhance the invasion success of aquatic invertebrates 

as given by Devin and Beisel (2007) and Ricciardi and Rasmussen (1998) (Norf et al. 2010).

 The maternal care of offspring (brooding) by this species can increase reproductive success by reducing larval 

mortality during early planktonic life stages (McHugh 1993, Schroeder and Hermans 1975).

 Increased knowledge of this species’ reproductive characteristics, has led Norf et al. (2010) to highlight the 

potential of H. invalida to invade the Great Lakes (contrary to earlier suggestions that it is unlikely to disperse 

internationally; cf. Ricciardi and Rasmussen 1998).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 The Great Lakes and Ponto-Caspian region are climatically compatible, which is one of the attributing 

factors to the success of Ponto-Caspian species in the Great Lakes (Reid and Orlova 2002).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?
1261

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Hypania invalida is able to survive in a wide range of temperature (2-25°C) and salinity (0-12 PSU)

(Mordukhaĭ-Boltovskoĭ 1964), both of which are well within the ranges that occur in the Great Lakes.

 Hypania invalida prefers current velocities less than 0.1 m/s (Norf et al. 2010), making most of the Great Lakes

basin suitable habitat with respect to water motion.

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible for H. invalida (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 This species is restricted to soft-bottom communities (e.g., silt, clay, fine sand) (Zorić et al. 2011).

 Sandy bottoms covered with zebra mussel beds also serve as potential habitat, though settlement densities here 

are typically lower than those in soft-bottom communities (Norf et al. 2010, Yakovlev and Yakovleva 2010).

 Hypania invalida is able to live at a wide range of water depths (shoreline to 960 m) (Zenkevich 1963).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 0
1262

spread of this species or would make the environment of the Great Lakes unsuitable)

Unknown U

8

 Increased salinization as a predicted effect of climate change may give this species a competitive advantage 

over Great Lakes native polychaetes.

 Shorter ice cover duration and warmer water temperatures may also benefit this species by lengthening its 

suitable yearly spawning period; however, if water becomes too warm, this effect may be detrimental to 

survival. For instance, in the summer of 2003, the lower Rhine experienced the highest water temperatures on 

record, greatly reducing the population density of H. invalida (Norf et al. 2010).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Hypania invalida is an active filter and deposit feeder, feeding primarily upon diatoms (Gruia and Manoleli 

1974). Hence, potential food items will likely not limit the distribution of this species within the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in -80% total 
1263

the Great Lakes and is not likely to be introduced points (at 

end)

Unknown U

9

 There is no critical species required by H. invalida.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0
1264

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 Hypania invalida has an extensive invasion history throughout Europe (Gherardi et al. 2009), with a spreading 

pattern that seems to suggest dispersal through a corridor connecting the Danube and Rhine rivers.

 Its dispersal pattern closely follows that of the European invasive isopod Jaera istri (bij de Vaate et al. 2002).

 Panov et al. (2009) described this species as being at high risk for dispersal and establishment when introduced 

to a new area.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0
1265

Unknown U

6

 Rapid expansion throughout European inland waterways has been facilitated by both human mediated (ballast 

water) upstream spread and natural (passive drift) downstream spread (bij de Vaate et al. 2002, Norf et al. 

2010).

 Within a few years of introduction to the Rhine River, it had dispersed along the entire navigable river stretch 

(Bernauer and Jansen 2006) and into many adjacent waterways, including the Moselle (Devin et al. 2006) and 

Elbe rivers (Eggers and Anlauf 2008).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 102

>100 High Adjustments

B. Critical species A*(1- 0%) 102

51-99 Moderate C. Natural enemy B*(1- 0%) 102

Control measures C*(1- 0%) 102

0-50 Low Potential for Establishment High

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 
1266

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Low

Socio-Economic: Low

Beneficial: Low

There is little or no evidence to support that Hypania invalida has the potential for significant 

environmental impacts if introduced to the Great Lakes.

Panov et al. (2009) list H. invalida as a white-list species, meaning there is a low risk of it causing 

significant ecological impacts to introduced areas. There are currently no reports of significant 

environmental impacts attributed to the presence of this species. Zorić et al. (2011) conclude that this 

species has limited influence on the overall benthic community.

There is little or no evidence to support that Hypania invalida has the potential for significant socioeconomic impacts if introduced to the Great Lakes.

Panov et al. (2009) list H. invalida as a white-list species, meaning there is a low risk of it causing 

significant socio-economic impacts within introduced areas. There are currently no reports of significant 

socio-economic attributed to the presence of this species.

There is little or no evidence to support that Hypania invalida has the potential for significant 

beneficial effects if introduced to the Great Lakes.

Hypania invalida was intentionally introduced to areas of the Volga River in the 1950s-1960s to enhance 

the nutrition base for tank-raised fish (Dzyuban and Slobodchikov 1980, Nechvalenko 1977).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6
1267

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0 √

Unknown U

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0 √

Unknown U

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

6
1268

Yes, and it has resulted in significant negative consequences for at least one native species

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?
1269

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 6
1270

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U
1271

 Hypania invalida was intentionally introduced to areas of the Volga River in the 1950s-1960s to enhance the 

nutrition base for tank-raised fish (Dzyuban and Slobodchikov 1980, Nechvalenko 1977).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 1

Total Unknowns (U) 0
1272

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1273

A.12 Rotifers

Scientific Name: Brachionus leydigii

Cohn, 1862

Common Name: Wheel Animal

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: High 

Brachionus leydigii has a high probability of introduction to the Great Lakes (Confidence level: 

High).

Potential pathway(s) of introduction: Transoceanic Shipping

Brachionus ledygii has been identified as having high probability of introduction to the Great Lakes via 

residual ballast sediment, where its resting stage is able to survive high salinities during ballast water 

exchange (Bailey et al. 2004, Bailey et al. 2005a, Bailey et al. 2005b; Johengen et al. 2005). In a survey 

of the ballast water of 35 different vessels entering the Great Lakes, this species was found hatched from 

diapausing eggs in residual ballast sediment in four of the ships. Additionally, it was isolated from the

sediment of those ships with a mean density of 3 individuals/40 g sediment (Bailey et al. 2005a, Johengen 

et al. 2005). It is likely that these resting stages are deposited by reproducing females taken in with ballast 

water rather than being brought in with disturbed sediments. Diapausing eggs present in sediment can 

pose an invasion risk if they are discharged during ballast operations or if they hatch during a voyage and 

the young rotifers are subsequently introduced during vessel deballasting (Gray and MacIsaac 2010). Of 

the 76 distinct taxa with a resting stage identified in this survey, Brachionus spp. were the most common 

and abundant of the Great Lakes non-natives (Bailey et al. 2005). Brachionus spp. are a predominant 

component of the planktonic community in the lower Rhine River, a region where ballast is commonly 

taken for ships entering the Great Lakes (van Dijk and van Zanten 2005). However, this primarily 

freshwater species is less abundant in other ballast loading regions such as the Baltic Sea and coastal 

areas with high salinity (Viitasalo et al. 1995).
1274

In more recent studies conducted since the 2006 (Canadian bound vessels) and 2008 (United States bound 

vessels) expansion of mandatory ballast flushing regulations to vessels with unpumpable ballast tank 

residuals, however, B. leydigii has been identified as having a significantly lower probability of 

introduction (Briski et al. 2010, Government of Canada 2006, Gray and MacIsaac 2010). Brachionus 

leydigii was not observed in ballast sediment collected in 2007 and 2008 from 19 ballast tanks of 17 

randomly selected Great Lakes bound ships originating from European, South American, and Atlantic 

ports (i.e. after the new regulations were in place) (Briski et al. 2010). Furthermore, in situ hatching 

studies suggest that fewer than 1% of diapausing invertebrate eggs will hatch and become available for 

introduction. The likelihood of this species entering the Great Lakes is therefore reduced as compared to 

species that may become resuspended in ballast water (Johengen et al. 2005). Additionally, Santagata et 

al. (2008) report a 100% mortality rate for rotifers exposed to full strength seawater for one hour in both 

empty-refill and flow-through treatments.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √
1275

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1
1276

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 40
1277

chain locker) while in its active or resting stage.

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 In a survey of the ballast water of 35 different vessels entering the Great Lakes, this species was found hatched 

from diapausing eggs in residual ballast sediment in four of the ships. Additionally, it was isolated from the 

sediment of those ships, with a mean density of 3 individuals/40 g sediment. It is likely that these resting stages 

are deposited by reproducing females taken in with ballast water rather than being brought in with disturbed 

sediments. Of the 76 distinct taxa with a resting stage identified in this particular survey, Brachionus spp. were 

the most common and abundant of the Great Lakes non-natives (Bailey et al. 2005a, Johengen et al. 2005).

 In more recent studies conducted since the 2006 (Canadian bound vessels) and 2008 (United States bound 

vessels) expansion of mandatory ballast flushing regulations to vessels with unpumpable ballast tank residuals, 

however, B. leydigii has been identified as having a significantly lower probability of introduction (Briski et al. 

2010, Government of Canada 2006, Gray and MacIsaac 2010). Brachionus leydigii was not observed in ballast 

sediment collected in 2007 and 2008 from 19 ballast tanks of 17 randomly selected Great Lakes bound ships 

originating from European, South American, and Atlantic ports (i.e. after the new regulations were in place) 

(Briski et al. 2010).

 Santagata et al. (2008) report a 100% mortality rate for rotifers exposed to full strength seawater for one hour 

in both empty-refill and flow-through treatments.

 In situ hatching studies suggest that fewer than 1% of diapausing invertebrate eggs will hatch and be available 

for introduction. The likelihood of this species entering the Great Lakes is therefore reduced as compared to 

species that are able to suspend in ballast water (Johengen et al. 2005).

 Johengen et al. (2005) report observing one B. leydigii individual in an upper-wing ballast tank of a surveyed 

vessel, leading the authors to suggest that this may have been the result of a previous transoceanic ballast 

introduction to Hamilton Harbor, as residual sediments generally do not accumulate in upper-wing tanks. 

Because only a single individual was recorded, the status of establishment cannot be determined, but this 

finding may be an indication that B. leydigii has been introduced previously to this location (Johengen et al. 

2005).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 √

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Brachionus spp. are a predominant component of the planktonic community in the lower Rhine River, a region 

where ballast is commonly taken for ships entering the Great Lakes (van Dijk and van Zanten 2005). However, 

this primarily freshwater species is less abundant in other ballast loading regions such as the Baltic Sea and 

coastal areas with high salinity (Viitasalo et al. 1995).

 In a survey of the ballast water of 35 different vessels entering the Great Lakes, this species was found hatched 

from diapausing eggs in residual ballast sediment in four of the ships. Additionally, it was isolated from the 

sediment of those ships, with a mean density of 3 individuals/40 g sediment. It is likely that these resting stages 

are deposited by reproducing females taken in with ballast water rather than being brought in with disturbed 

sediments. Of the 76 distinct taxa with a resting stage identified in this particular survey, Brachionus spp. were 

the most common and abundant of the Great Lakes non-natives (Bailey et al. 2005a, Johengen et al. 2005).
1278

 Johengen et al. (2005) report observing one B. leydigii individual in an upper-wing ballast tank of a surveyed 

vessel, leading the authors to suggest that this may have been the result of a previous transoceanic ballast 

introduction to Hamilton Harbor, as residual sediments generally do not accumulate in upper-wing tanks. 

Because only a single individual was recorded, the status of establishment cannot be determined, but this 

finding may be an indication that B. leydigii has been introduced previously to this location (Johengen et al. 

2005).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 1 80 High

Total Unknowns (U) 0 Confidence Level High
1279

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Brachionus leydigii has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: Moderate).

This species produces a resting stage consisting of a three-layered diapausing egg that is protected from 

external stressors, such as desiccation and temperature extremes, until conditions become favorable and a 

viable individual hatches (Clement and Wurdak 1991, Sladecek 1983, Wurdak et al. 1978). This 

reproductive strategy leads B. ledygii to having high Great Lakes invasion potential, as diapausing eggs 

can be resistant to short term salinity exposure, are not easily flushed from ballast tanks, and have the 

potential for in situ hatching during a transoceanic voyage (Bailey et al. 2003, Bailey et al. 2004, Bailey et 

al. 2005a, Bailey et al. 2005b, Bailey et al. 2006, Gray et al. 2005, Gray and MacIsaac 2010). However, 

viability of similarly resistant diapausing copepods and cladoceran eggs is low under conditions of low 

oxygen or anoxia (Carvalho and Wolf 1989, Uye 1980, Uye et al. 1984).

Branchionus leydigii is distributed globally and present in a variety of physical and environmental 

conditions. Bailey et al. (2005a) and Johengen et al. (2005) reported this species as a having a habitat 

match to the Great Lakes, able to hatch in a 0 ppt salinity medium. Additionally, because B. leydigii

thrives in primarily eutrophic conditions, the central and western basins of Lake Erie may provide 

potential suitable habitat due to their high eutrophication potential (Summers 2001). Johengen et al. 

(2005) report observing one B. leydigii individual in an upper-wing ballast tank of a surveyed vessel, 

leading the authors to suggest that this may have been the result of a previous transoceanic ballast 

introduction to Hamilton Harbor, as residual sediments generally do not accumulate in upper-wing tanks. 

Because only a single individual was recorded, the status of establishment cannot be determined, but this 

finding may indicate that B. leydigii has been introduced previously to this location (Johengen et al. 

2005).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6
1280

 Brachionus ledygii is distributed globally and present in a variety of physical and environmental conditions. 

Bailey et al. (2005) and Johengen et al. (2005) reported this species as a having habitat match to the Great 

Lakes, able to hatch in a 0 ppt salinity medium.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 This species produces a resting stage consisting of a three-layered diapausing egg that is protected from 

external stressors, such as desiccation and temperature extremes (Clement and Wurdak 1991, Sladecek 1983, 

Wurdak et al. 1978). However, viability of similarly resistant diapausing copepods and cladoceran eggs is low 

under conditions of low oxygen or anoxia (Carvalho and Wolf 1989, Uye 1980, Uye et al. 1984).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 Brachionus ledygii filter feeds on small material such as bacteria and detritus and is able to selectively filter 

particles by size with a corona of cilia surrounding its mouth (Wallace 2002).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3
1281

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

3

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 3
1282

region)

Not similar 0

Unknown U

8

 This species exists in a worldwide distribution, with many localities having climatic conditions similar to those 

of the Great Lakes (i.e. Ponto-Caspian region including the Rhine River) (van Dijk and van Zanten 2005).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 Bailey et al. (2005a) classifies this species as having a habitat match to the Great Lakes based upon its ability 

to hatch in a 0 ppt medium.

 Abiotic factors and climatic conditions in the Ponto-Caspian region are quite similar to the Great Lakes, 

making the region compatible for this species (Grigorovich et al. 2003, Reid and Orlova 2002).

 Great Lakes underwent similar anthropogenic eutrophication as the Ponto-Caspian region (Reid and Orlova 

2002). Surface water temperature is similar between the Great Lakes and Ponto-Caspian seas (Grigorovich et 

al. 2003, Reid and Orlova 2002, USEPA 2008).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Brachionus leydigii thrives primarily in eutrophic environments (Maemets 1983, Sladecek 1983), likely making 

the central and western basins of Lake Erie the most suitable potential habitat due to their high eutrophication 

potential (Summers 2001).
1283

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

U

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 This species is a filter feeder, feeding primarily on bacteria, small algae, and detritus (Wallace 2002), all of 

which are non-limiting resources in the Great Lakes.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6
1284

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required for the survival of B. leydigii.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

U

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)
1285

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

3

 Of 23 Great Lakes nonindigenous species observed in ballast sediment, this species occurred in the greatest 

number of sampled ships (4/35) and had a relatively large abundance (3 individuals/40 g sediment) (Bailey et 

al. 2005a).

 In situ hatching studies suggest that less than 1% of diapausing invertebrate eggs will hatch and be available 

for introduction, thus reducing propagule pressure (Johengen et al. 2005).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

0

 This species has a broad global distribution with no specific records of nonindigenous occurrences.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?
1286

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 67

>100 High Adjustments

B. Critical species A*(1- 0%) 67

51-99 Moderate C. Natural enemy B*(1- 0%) 67

Control measures C*(1- 0%) 67

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 5

2-5 Moderate 
1287

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

POTENTIAL IMPACT RESULTS

Environmental: Low

Socio-Economic: Low

Beneficial: Low

There is little or no evidence to support that Brachionus leydigii has the potential for significant 

environmental impacts if introduced to the Great Lakes.

While rotifers tend to be significant contributors to food web structure due to high abundances and rapid 

turnover rates, there is no species specific information currently available on the trophic effect of 

introduced populations of B. ledygii. In addition, approximately 275 species of rotifers have already been 

reported in the Great Lakes, and it is unlikely that the addition of a single species will lead to any new 

significant environmental impacts.

There is little or no evidence to support that Brachionus leydigii has the potential for significant 

socio-economic impacts if introduced to the Great Lakes.

As a group, introduced rotifers are not known to generate significant socio-economic impacts (O'Connor 

et al. 2008), and there are currently no reports of this species leading to negative impact in introduced 

areas.

There is little or no evidence to support that Brachionus leydigii has the potential for significant 

beneficial effects if introduced to the Great Lakes.

Rotifers have been widely used as a bioindicator species in pollution monitoring, and due to their 

sensitivity to pollutants and ease of culture, they have become important tools in ecotoxicological testing 

(Wallace 2002). However, there is no evidence supporting that B. leydigii will offer any advantage as an 

ecological indicator as compared to rotifers already present in the Great Lakes.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?
1288

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1

Not significantly 0 √

Unknown U

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1

Not significantly 0 √

Unknown U

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0 √

Unknown U

 While rotifers tend to be significant contributors to food web structure due to high abundances and rapid 

turnover rates, there is no species specific information currently available on the trophic effect of 

introduced populations of B. ledygii. In addition, approximately 275 species of rotifers have already been 

reported in the Great Lakes, and it is unlikely that the addition of a single species will lead to any new 

significant environmental impacts.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1

Not significantly 0 √
1289

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1

Not significantly 0 √

Unknown U

Environmental Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1290

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6
1291

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1

Not significantly 0 √

Unknown U
1292

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 Rotifers have been widely used as a bioindicator species in pollution monitoring, and due to their 

sensitivity to pollutants and ease of culture, they have become important tools in ecotoxicological testing 

(Wallace 2002). However, there is no evidence supporting that B. leydigii will offer any advantage as an 

ecological indicator as compared to rotifers already present in the Great Lakes.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?
1293

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1294

Scientific Name: Filinia cornuta

Weisse, 1847

Common Name:

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: High

Filinia cornuta has a high probability of introduction to the Great Lakes (Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Rotifer identified as having high probability of invasion if introduced to the Great Lakes. Potential 

pathway of introduction: ballast sediment. Resting stage may survive transport under harsh conditions 

such as in ballast tanks and ballast sediment (Bailey et al. 2005, Johengen et al. 2005). NOTE: This 

species is identified as having lower probability of invasion due to the effects of ballast water exchange or 

flushing (Briski et al. 2010).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 Filinia cornuta is widely distributed around the world, but it is not known from North America. 

1b) What is the proximity of this species to the Great Lakes basin?
1295

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

 Filinia cornuta is widely distributed around the world (including Hungary, Austria, Turkey, Mexico, China, 

Israel, Russia, and Brazil), but it is not known from North America. 

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

 Filinia cornuta is never sold or used in market. It has been relatively well documented since 1983 and there is 

no record of its importance as a biological supply or educational tool.

 However, in Israel, this species has been used as food for fish larvae (e.g., carp larvae) (Valdenberg et al. 

2006).
1296

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?
1297

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Filinia cornuta was one of 76 taxa documented following analysis of residual sediments from 36 ships entering 

the Great Lakes (Briski et al. 2010). The occurrence of these resting eggs was reduced from a mean of 3 resting 

eggs per 40 g sediment to zero after flushing ballast tanks with salt water, per current regulations (Briski et al. 

2010).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 √

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
1298

 Filinia cornuta was one of 76 taxa documented following analysis of residual sediments from 36 ships entering 

the Great Lakes (Briski et al. 2010). The occurrence of these resting eggs was reduced from a mean of 3 resting 

eggs per 40 g sediment to zero after flushing ballast tanks with salt water, per current regulations (Briski et al. 

2010).

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 1 80 High

Total Unknowns (U) 0 Confidence Level High
1299

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Filinia cornuta has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: moderate).

This species is identified as having high probability of invasion if introduced to the Great Lakes. Potential 

pathway of introduction is ballast sediment. Resting stage of this species may survive transport under 

harsh conditions such as in ballast tanks and ballast sediment (Bailey et al. 2005, Johengen et al. 2005). 

NOTE: This species is identified as having lower probability of invasion due to the effects of ballast 

water exchange or flushing (Briski et al. 2010).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide ranges of temperature (0°C-30°C), 

salinity (0-16 parts per thousand), oxygen (0-saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Filinia cornuta has been found in the saline-alkaline Lake Dalu in China with temperatures at 23-24°C (Zhao et 

al. 2002).

 In experiments conducted on eutrophic Huetzalin Lake in Mexico, F. cornuta was found in samples where 

temperatures ranged from 14-24°C, DO ranged from 1.36-13.6 mg/L (García et al. 2009).

 This species is also found in Asartepe Dam Lake, Turkey, which froze over the winter (Buyurgan et al. 2010). 

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 mg/L) 9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

5
1300

 In experiments conducted on eutrophic Huetzalin Lake in Mexico, F. cornuta was found in samples where DO 

ranged from 1.36-13.6 mg/L (García et al. 2009).

 This species is also found in Asartepe Dam Lake, Turkey, which froze over the winter (Buyurgan et al. 2010). 

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

6

 Filinia cornuta is a heterotrophic species that feeds on small algae (Sladecek 1983).

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U
1301

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

 The reproductive strategy for this species has not been recorded. 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 Filinia cornuta is widely distributed and has been found in Ankara, Turkey in Asartepe Dam Lake (Buyurgan, et 

al. 2010). This lake freezes in the winter, but has summer temperatures of 23.5°C.

 This species has also been found in a Hungarian lake (Schöll and Kiss et al. 2009). The climate in Hungary is 

similar to the Great Lakes (average air temperature summer high of 73-82°F and winter low of 19-27°F).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3
1302

Not similar 0

Unknown U

7

 Filinia cornuta has been found in the saline-alkaline Lake Dalu in China with temperatures at 23-24°C (Zhao et 

al. 2002).

 In experiments conducted on eutrophic Huetzalin Lake in Mexico, F. cornuta was found in samples where 

temperatures ranged from 14-24°C, DO ranged from 1.36-13.6 mg/L (García et al. 2009).

 Filinia cornuta is widely distributed and has been found in Ankara, Turkey in Asartepe Dam Lake (Buyurgan, et 

al. 2010). This lake freezes in the winter, but has summer temperatures of 23.5°C.

 This species has also been found in a Hungarian lake (Schöll and Kiss 2009). The climate in Hungary is similar 

to the Great Lakes (average air temperature summer high of 73-82°F and winter low of 19-27°F). 

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Filinia cornuta has been found in a floodplain with dense macrovegetation in Hungary (Schöll and Kiss 2009).

 In Mexico, this species was found in a shallow lake with average depth less than 3m (García et al. 2009).

 Given the range of DO and temperatures tolerated by this species, it should be able to find suitable habitat in 

the Great Lakes basin.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

5

 Filinia cornuta has been found in the saline-alkaline Lake Dalu in China with temperatures at 23-24°C (Zhao et 

al. 2002).
1303

 In experiments conducted on eutrophic Huetzalin Lake in Mexico, F. cornuta was found in samples where 

temperatures ranged from 14-24°C, DO ranged from 1.36-13.6 mg/L (García et al. 2009).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6 

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

5

 A number of algal species are present in the Great Lakes, making it likely that Filinia cornuta could feed on 

species available in these waters.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?
1304

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3
1305

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

7

 This species has been reported from lakes in Europe, China, and Mexico (García et al. 2009, Schöll and Kiss

2009, Zhao et al. 2002)

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

U

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

-50% total 

points (at 
1306

to control its establishment and spread) end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 65

>100 High Adjustments

B. Critical species A*(1- 0%) 65

51-99 Moderate C. Natural enemy B*(1- 0%) 65

Control measures C*(1- 0%) 65

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 5

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential for socioeconomic impacts to result from Filinia cornuta if 

introduced to the Great Lakes is inadequate to support proper assessment.
1307

Filinia cornuta is not known to harm any economic sectors and there is no record of this species posing a 

threat to human health, and the species is not known to negatively affect water quality. Rotifers in 

general are indicators for organic pollution (Sladecek 1983).

There is little or no evidence to support that Filinia cornuta has the potential for significant 

environmental impacts if introduced to the Great Lakes.

Filinia cornuta is a widely distributed animal across the world. There is no report of this species posing 

threat to native species in over more than 25 years of records (Sledecek 1983).

Filinia cornuta has the potential for moderate beneficial effects if introduced to the Great Lakes.

This species is important as a food source for fishes (Geng et al. 2005), including for fish larvae (e.g., 

carp larvae) (Swift 1992, Valdenberg et al 2006). Colloids (suspended solids) and wastewater provide 

common food sources for this species and it may enhance water quality (Sladecek 1983).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 Filinia cornuta is a widely distributed animal across the world. It has been found in Turkey, Russia, Brazil, 

Mexico, Austria, Hungary, New Zealand, and China. There is no report of it posing threat to native species 

over more than 25 years of records (Sledecek 1983).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0 √

Unknown U

 Filinia cornuta is a heterotrophic species that feeds mainly on algae.
1308

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

 Filinia cornuta feeds mainly on algae smaller than 10 m. The Great Lakes contain at least 24 kinds of algae 

(Mills et al. 1993).

 This species is important as a food sources for fishes (Geng et al. 2005), including for fish larvae (e.g., carp 

larvae) (Valdenberg et al. 2006). 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 No information on the potential for genetic effects by this species was found.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

 This species is not known to negatively affect water quality; however, it feeds on the colloids that are suspended 

in the water. Therefore, it might enhance the water quality instead (Sladecek 1983). 

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?
1309

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 0

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

 There is no record of this species posing a threat to human health, but rotifers in general are good indicators 

for saprobity (Sladecek 1983).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?
1310

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 This species is not known to negatively affect water quality; however, it feeds on the colloids that are suspended 

in the water. Therefore, it might enhance the water quality instead (Sladecek 1983). 

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

 This species is not known to harm any economic sectors.

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U
1311

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6
1312

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

 There is no documented recreational value for this species.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 This species has no significant value in medicine or research.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 

Not significantly 0 √

Unknown U 

 Colloids (suspended solids) and wastewater provide common food sources for this species (Sledecek 1983).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 This species is important as a food source for fishes (Geng et al. 2005), including for fish larvae (e.g., carp 

larvae) (Valdenberg et al. 2006).

 Larval instar of Glassworm Chaoborus crystallinus feed on Filinia cornuta (Swift 1992).

Beneficial Effect Total 0

Total Unknowns (U) 0
1313

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1314

Scientific Name: Filinia passa

O.F. Muller, 1786

Common Name:

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unlikely

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: High

Filinia passa has a high probability of introduction to the Great Lakes (Confidence level: High).

Potential pathway(s) of introduction: Transoceanic Shipping

Rotifer identified as having high probability of invasion if introduced to the Great Lakes. Potential 

pathway of introduction is ballast sediment. The resting stage of this species may survive transport under 

harsh conditions such as in ballast tanks and ballast sediment (Bailey et al. 2005, Johengen et al. 2005). 

NOTE: This species is identified as having lower probability of invasion due to the effects of ballast 

water exchange or flushing (Briski et al. 2010).

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g.,

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

1b) What is the proximity of this species to the Great Lakes basin?
1315

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100

No, this species this species is rarely/never sold. 0 √

Unknown U

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5
1316

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity Score x 0.5
1317

involves transport of live organisms on/across the Great Lakes.

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 √

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0

Unknown U

 Filinia passa was found to be a habitat match to the Great Lakes because it hatched in a 0% medium during lab 

experiments that was considered a match to the habitat of the Great Lakes (Bailey et al. 2005). 

 Filinia passa is capable of living in the abiotic conditions of the Great Lakes and also has a broad global 

distribution and rotifers in general should present the predominant invasion risk to the Great Lakes (Bailey et 

al. 2005).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1 √

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

 Bailey et al. (2005) studied the resting stages of invertebrates in residual ballast sediments of transoceanic 

ships as possible vectors to the Great Lakes in which Filinia passa occurred on 4 ships out of the possible 35 

and had an abundance of 3.5 that emerged from a 40 g sediment samples from the ships it was found.
1318

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Not established in North America, including the Great Lakes

Filinia passa has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: moderate.)

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

0 x 0 Unlikely

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

80 x 1 80 High

Total Unknowns (U) 0 Confidence Level High
1319

Filinia passa has a broad global distribution (Bailey et al 2005) and has been found to be able to grow in 

laboratory conditions matching Great Lakes abiotic conditions. Filinia passa has been found in winter 

(mean temperature, 3.8°C) in Oder River, Germany (Wolska and Piasecki 2006), indicating that it will 

likely be able to overwinter in the Great Lakes as well. It is a bacterivore so primary food is readily 

available in the Great Lakes.

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 This species is found in the Oder River (near the Baltic Sea), including the estuarine portion. Therefore, it can 

survive in higher salinity waters (0.5-2 psu; Radziejewska and Schernewski 2008) and in polluted/eutrophic 

conditions (Radziejewska and Schernewski 2008). In addition, this area of the river can have a mean winter 

temperature of 2.3°C and mean summer temperature of 24.1°C (Wolska and Piasecki 2006).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

7

 Filinia passa has been found in winter (mean temperature, 2.3 ̊C) in Oder River, Germany (Wolska and 

Piasecki 2006).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9
1320

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

4

 Filinia passa likely has similar diet to F. longiseta, which consumes bacteria (Ooms-Wilms et al. 1993)

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

U

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 6
1321

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

U

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes

region)

3

Not similar 0

Unknown U

8

 This species is found in the Oder River (near the Baltic Sea), including the estuarine portion. Therefore, it can 

survive in higher salinity waters (0.5-2 psu; Radziejewska and Schernewski 2008) and in polluted/eutrophic 

conditions (Radziejewska and Schernewski 2008). In addition, this area of the river can have a mean winter 

temperature of 2.3°C and mean summer temperature of 24.1°C (Wolska and Piasecki 2006).

 Filinia passa was found to be a habitat match to the Great Lakes because it hatched in a 0% medium during lab 

experiments which was considered a match to the habitat of the Great Lakes (Bailey et al. 2005). F. passa are 

capable of living in the abiotic conditions of the Great Lakes and also has a broad global distribution and 

rotifers in general should present the predominant invasion risk to the Great Lakes (Bailey et al. 2005).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8
1322

 Filinia passa are capable of living in the abiotic conditions of the Great Lakes and also has a broad global 

distribution and rotifers in general should present the predominant invasion risk to the Great Lakes and found 

as a habitat match (Bailey et al. 2005).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 Filinia passa are capable of living in the abiotic conditions of the Great Lakes and also has a broad global 

distribution (Bailey et al. 2005)

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

3

 This species is found in the Oder River (near the Baltic Sea), including the estuarine portion. Therefore, it can 

survive in higher salinity waters (0.5-2 psu; Radziejewska and Schernewski 2008)

 Rotifers such as F. passa and F. longestia prevailed during warm months specifically June and July and their 

season dynamics were governed by temperature and presence of large Daphnia individuals. Average minimum 

and maximum values of abundance(Ind. L^-1) is 53.33 and 253.33 (Michaloudi and Kostecka 2004).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9
1323

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

5

 Bacteria are abundant in most F. passa habitats.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6
1324

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-10%

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

3

 Of all species hatched from residual ballast sediment, Bailey et al. (2005) found F. passa to be the second most 

abundance species.

HISTORY OF INVASION AND SPREAD
1325

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

4

 Filinia passa is native to Australia, but is also found in Ukraine, Polish, German and Greek waters 

(Galkovskaya and Molotkov 2001, Goździejewska and Tucholski 2011, Holst et al. 1998, Michaloudi and 

Kostecka 2004, Millar 2008)

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

4

 Dates of introductiosns were not found, but based on distribution it appears to spread quite easily.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0
1326

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 69

>100 High Adjustments

B. Critical species A*(1- 0%) 69

51-99 Moderate C. Natural enemy B*(1- 10%) 62.1

Control measures C*(1- 0%) 62.1

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 3

2-5 Moderate 

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Current research on the potential environmental impacts to result from Filinia passa if 

introduced to the Great Lakes is inadequate to support proper assessment.

There is insufficient information available to determine whether Filinia passa poses a threat to other 

species or water quality. There are no reports on how it affects or interacts with other species. It is 

unknown whether this speies alters the physical components of the ecosystem.

There is little or no evidence to support that Filinia passa has the potential for significant socioeconomic impacts of introduced to the Great Lakes.
1327

It has not been reported that Filinia passa poses a threat to human helath or water quality. There is no 

evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and 

associated tourism, or the aesthetic appeal of the areas it inhabits.

There is little or no evidence to support that Filinia passa has the potential for significant beneficial 

impacts of introduced to the Great Lakes.

It has been indicated that Filinia passa can be used for the control of other organisms or improving water 

quality. There is no evidence to suggest that this species is commercially, recreationally, or medically 

valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U √

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 1 √
1328

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U 

 Mesocyclops and Tropcyclops induces de novo spine formation or spine lengthening in several planktonic 

rotifers. Rotifers that have observed this included Filinia passa. The spined phonotypes is a significant reduction 

in capture and ingestion by invertebrate predators (Thorpe 1977). This is similar to the spiny water flea in 

regards to the spiny water flea having a sharp spine which is difficult for small fish to eat.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U √

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √
1329

Environmental Impact Total 1

Total Unknowns (U) 5

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1
1330

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
1331

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √
1332

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1333

A.13 Plants

Scientific Name: Crassula helmsii

Cockayne

Common Name: Swamp Stone-crop, New Zealand Pygmy Weed

Synonyms: Tillaea recurva, Crassula recurva, Tillaea helmsii

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Unlikely

Unauthorized intentional release: Unknown

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Crassula helmsii has an unknown probability of introduction to the Great Lakes (Confidence level: 

Moderate).

Potential pathway(s) of introduction: Unauthorized Intentional Release

This species has been found for sale at large outdoor stores (e.g., Lowe's Hardware mistakenly sold it 

under another name in Florida), as well as recommended for hobbyists online. It is unknown, however, if 

it is being bought and sold in the Great Lakes region.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U
1334

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 √

Unknown U

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 This species has been found for sale at large outdoor stores (e.g., Lowe's Hardware mistakenly sold it under 

another name in Florida), as well as recommended for hobbyists online. It is unknown, however, if it is being 

bought and sold in Michigan or the Great Lakes region.
1335

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U √

 This species has been found for sale at large outdoor stores (Lowe's Hardware), as well as recommended for 

hobbyists online. It is unknown, however, if it is being bought and sold in Michigan or the Great Lakes region.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U
1336

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
1337

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

0 x 0 Unlikely

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x U U Unknown

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
1338

Crassula helmsii has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Crassula helmsii has a broad physiological tolerance and this range suggest it would fair just fine in the 

Great Lakes. C. helmsii can overwinter in temperatures of 0°C. In the United Kingdom, it is highly 

invasive and outcompetes many native plant species by forming dense smothering mats of vegetation; this 

same occurrence would happen in the Great Lakes region if introduced. C. helmsii reproduces very easily 

and would spread once introduced. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8

 This species can tolerate drying for extended periods (Kirby 1965)

 C. helmsii survives in poor phosphorus conditions (3.4 μg/L), to rich phosphorus conditions (529 μg/L), though 

more limited spread in poor phosphorus (Brunet 2002).

 C. helmsii survives in poor potassium conditions (0.16 μg/L), to rich potassium conditions (8.56 μg/L), though 

more limited spread in poor potassium (Brunet 2002).

 This species inhabits shallow acidic seasonal pools, to more alkaline, nutrient-rich lakes (Dawson and Warman 

1987). 

 This species appears to do better in high light, but has also been found despite shading (Dawson and Warman 

1987).

 C. helmsii has temperature range of 0-25°C, including extended periods under snow (EPPO 2007, Kirby 1965).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0
1339

Unknown U

8

 C. helmsii has a temperature range of 0-25°C, including extended periods under snow (Kirby 1965, EPPO 

2007).

 This species can withstand temperatures up to -6°C (Leach and Dawson 1999).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 In some areas of the United Kingdom this species is highly invasive and it out-competes many native plant 

species by forming dense smothering mats of vegetation (Bridge 2005).

 C. helmsii shows extreme competitiveness, dominates many sites, and can cover the entire water surface 

(Brunet 2002).

 C. helmsii is very tolerant of herbicides (Dawson 1996).

 C. helmsii has aggressive competition with other aquatic species to their near exclusion, originally observed in 

1920s with Nympizaea (Swale and Belcher 1982) but more recently with Elodea spp. (Cockerill 1979), with 

natural flora in three areas including the New Forest (A. Byfield; 1984 and pers. comm.), and with the rarer 

Potomogeton spp. (M. Briggs, pers. comm.) (Dawson and Warman 1987).

 The invasiveness of this species may result, in part, from Crassulacean acid metabolism, which confers a 

competitive advantage in relation to growth through carbon conservation (Klavsen and Maberly 2009).

 C. helmsii suppresses germination of other species up to 83%, yet there was no effect on seed back and no loss 

of plant species on four ponds in England. However, the experiment was over a limited time scale (Langdon et 

al. 2004).
1340

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

8

 C. helmsii propagates via vegetative fragmentation of fragments as small as 1cm (Brunet 2002).

 The natural change in branching pattern of this species in the autumn (or shortening days) produces many 

short laterals with many leaves ('turions') which separate readily from the parent and are dispersed by wind 

and water current. However, they seem not to sink but collect around the shores of the water body (Dawson and 

Warman 1987).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 C. helmsii propagates via vegetative fragmentation of fragments as small as 1cm (Brunet 2002).

 The natural change in branching pattern of this species in the autumn (or shortening days) produces many 

short laterals with many leaves ('turions') which separate readily from the parent and are dispersed by wind 

and water current. However, they seem not to sink but collect around the shores of the water body (Dawson and 

Warman 1987).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?
1341

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 In its native range (Australia), air temperatures range from -6-30°C . The invaded range (Belgium, Denmark, 

France, Germany, Netherlands, United Kingdom) includes areas with very a similar climate. 

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 This species inhabits freshwater areas, with a range of nutrient levels. It is found in waters with pH from 4.29-

7.83, and alkalinity from 0-0.92 m.eq/L. These ranges include conditions found in the Great Lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

6

 C. helmsii propagates inhabits the margins and shallow waters of freshwater lakes and ponds (Bridge 2005).

 This species inhabit ponds, lakes, gravel pits and other static water bodies; also, streams with low flow (Brunet 

2002).

 This species substrates include gravel, mud/silt, clay, and sand (Brunet 2002).

 C. helmsii can inhabit a range of depths: from drying soils to submerged depths of 3 m (Dawson 1996).
1342

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

4

 This species can withstand warm water temperatures, so climate change may benefit. However, climate change 

may also hinder this species, as it is adapted to take advantage of low CO2 conditions.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 C. helmsii is an autotroph.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6
1343

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)
1344

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

 This depends on introductions from aquarium or pond hobbyists, which is unknown.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

5

 C. helmsii is native to New Zealand and Australia (Brunet 2002).

 This species was introduced to the United Kingdom (Bridge 2005).

 It was also introduced to Belgium, Denmark, France, Germany, Netherlands (EPPO 2007).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6
1345

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

5

 C. helmsii was introduced to the United Kingdom in 1956, and has since spread throughout the British Isles 

(Brunet 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 91

>100 High Adjustments

B. Critical species A*(1- 0%) 91

51-99 Moderate C. Natural enemy B*(1- 0%) 91

Control measures C*(1- 0%) 91

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 1

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low
1346

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Moderate

Beneficial: Low

Crassula helmsii has the potential for high environmental impact if introduced to the Great Lakes.

Crassula helmsii suppresses surrounding epiphytic and planktonic algae more than the effect of shade 

(Brunet 2002). This species has negatively affected the breeding success of the protected great crested 

newt Triturus cristatus (Watson 1999). In some areas of the United Kingdom, C. helmsii is highly 

invasive and outcompetes native plant species by forming dense smothering mats of vegetation (Bridge 

2005). Crassula helmsii shows extreme competitiveness, dominates many sites, and can cover the entire 

water surface (Brunet 2002) and is very tolerant of herbicides (Dawson 1996).

Crassula helmsii has the potential for moderate socio-economic impact if introduced to the Great 

Lakes.

Crassula helmsii can clog drainage ditches (EPPO 2007) and can impact recreational use (EPPO 2007).

There is little or no evidence to support that Crassula helmsii has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Crassula helmsii can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U
1347

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 C. helmsii suppresses surrounding epiphytic and planktonic algae more than the effect of shade (Brunet 2002).

 Has negatively affected the breeding success of the protected great crested newt Triturus cristatus (Watson 

1999).

 In some areas of the United Kingdom this species is highly invasive and it out-competes many native plant 

species by forming dense smothering mats of vegetation (Bridge 2005).

 C. helmsii shows extreme competitiveness, dominates many sites, and can cover the entire water surface 

(Brunet 2002).

 This species is very tolerant of herbicides (Dawson 1996).

 C. helmsii has aggressive competition with other aquatic species to their near exclusion, originally observed in 

1920s with Nympizaea (Swale and Belcher 1982) but more recently with Elodea spp. (Cockerill 1979), with 

natural flora in three areas including the New Forest (A. Byfield pers. comm., Byfield 1984), and with the rarer 

Potomogeton spp. (M. Briggs, pers. comm.) (Dawson and Warman 1987).

 This species invasiveness may result, in part, from Crassulacean acid metabolism, which confers a competitive 

advantage in relation to growth through carbon conservation (Klavsen and Maberly 2009).

 C. helmsii suppresses germination of other species up to 83%, yet there was no effect on seed back and no loss 

of plant species on four ponds in England. However, the experiment was over a limited time scale (Langdon et 

al. 2004).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6
1348

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 √

Unknown U

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U √

 This species shows extreme competitiveness, dominates many sites, and can cover the entire water surface 

(Brunet 2002) - it may shade benthic habitats.

Environmental Impact Total 6

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0
1349

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 √

Unknown U

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1 √

Not significantly 0

Unknown U

 C. helmsii can clog drainage ditches (EPPO 2007).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U
1350

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation 

and tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 C. helmsii can impact recreational use (EPPO 2007).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
1351

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 
1352

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 0

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1353

Scientific Name: Egeria densa

Planchon

Common Name: Brazilian Waterweed

Synonyms: Anacharis densa (Planch.) Victorin, Elodea densa (Planch.) Caspary, Philotria densa

(Planch.) Small & St. John

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unknown

Hitchhiking/fouling: Moderate

Unauthorized intentional release: High

Stocking/planting/escape from recreational culture: Low

Escape from commercial culture: Unknown

Transoceanic shipping: Unlikely

Egeria densa has a high probability of introduction to the Great Lakes (Confidence level: Low). 

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentional

Release, Escape from Recreational and Commercial Culture

Egeria densa is one of the most common species sold in the Montreal aquarium trade (Cohen et al. 2007). 

The sale and transport of E. densa is prohibited in Illinois, Indiana, Michigan, Minnesota, and Wisconsin 

(GLPANS 2012); but there are no regulations on the sale or transport of E. densa in New York, Ohio, 

Ontario, Pennsylvania, or Quebec. A survey performed from 2002 to 2003 on aquarium and pet stores 

near Lakes Erie and Ontario found that 35% of stores surveyed sold E. densa (Rixon et al. 2005). Due to 

the availability of E. densa in stores near the Great Lakes, and the ability of the species to overwinter, 

Rixon et al. (2005) predicted that it has the potential to be introduced to the Great Lakes. Based on the 

number of aquarium stores in Montreal, Quebec that sold E. densa, the number of E. densa sold by each 

store, and the disposal pathways for aquatic plants, Cohen et al. (2007) estimates that 188 E. densa

individuals are released into the St. Lawrence Seaway each year.

This species may be transported by hitchhiking on recreational gear; E. densa grows in thick mats that can 

become entangled on boat propellers and trailer wheels, or can be captured in bilge water (Washington 

State Department of Ecology 2013). Attached fragments can be transported between water bodies. Egeria 

densa is not known to be taken up in ballast water.

As a popular ornamental plant, E. densa is planted in water gardens (INDNR 2013) and can be purchased 

(e.g. Green Vista Water Gardens) in Ohio; however, there is not enough information available to 

determine the frequency of E. densa plantings. Egeria densa is cultured in Florida for the ornamental 
1354

aquatic plant industry (Fenner); however, there is no indication that E. densa is commercially cultured in 

the Great Lakes region. 

Egeria densa was first reported outside of its native range in 1893 in Long Island, New York (Yarrow et 

al. 2009). Egeria densa is a known nuisance species in California, Oregon, and Washington (California 

State Parks 2014, Washington State Department of Ecology 2013). Egeria densa has been reported in 

Powderhorn Lake, Minnesota (City of Minneapolis 2013) and Griffy Lake, Indiana, but has been 

controlled and eradicated. Egeria densa occurs private ponds in Lake County, Illinois (Illinois Database 

of Aquatic Non-native Species 2014, Lake County Health Department and Community Health Center 

2009, New Invaders Watch Program 2014), which is near Lake Michigan; however, dispersal from these 

ponds is limited because it does not occur in waters connected to the Great Lakes. 

Nonindigenous E. densa populations in Río Cruces, Chile have similar genotypes as populations in 

Western Oregon, suggesting that the two populations experienced similar bottlenecking events at 

introduction, or there is a lack of genetic diversity in the native population (Carter and Sytsema 2001). 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U 

 A study of the Montreal, Quebec aquarium trade estimates that up to 188 E. densa plants enter the St. Lawrence 

Seaway each year (Cohen et al. 2007). While this estimate does not represent actual sightings, it represents a 

risk of introduction into the St. Lawrence Seaway, which then connects with the Great Lakes.

 The plant is capable of vegetative reproduction from stem fragments containing double nodes (Washington 

State Department of Ecology 2013). As such, new plants may form from fragments carried by water currents.

 Egeria densa has been reported in Powderhorn Lake, Minnesota (City of Minneapolis 2013), and Griffy Lake, 

Indiana, but has been controlled and eradicated.

 Egeria densa occurs private ponds in Lake County, Illinois (Illinois Database of Aquatic Non-native Species

2014, Lake County Health Department and Community Health Center 2009, New Invaders Watch Program 

2014), which is near Lake Michigan.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25
1355

Unknown U √

 The location of the current closest population of E. densa is not known, but previous records have been 

documented in Great Lakes states, including Minnesota and Indiana: 

o This species was found in 2007 in Powderhorn Lake, Minneapolis, MN but has been eradicated 

and not found since (City of Minneapolis 2013).

o In Indiana, a 2004 infestation of Griffy Lake was subsequently treated and has not been detected

since 2008 (S. Cotter, City of Bloomington Parks and Recreation Department, Natural Resources 

Manager, pers. comm. 2012, Long 2008).

 More distant but persistent populations of this species can be found in California and Washington state:

o In Long Lake, Washington, E. densa comprised approximately 90% of the aquatic vegetation and 

persisted despite of 19 years of management that included a drawdown and harvesting (Jacoby et 

al. 2001).

o Subject to an intensive chemical control program, E. densa was documented in 2000 as covering 

3,900 acres of California’s Sacramento-San Joaquin Delta and spreading at a rate of 100 

acres/year (California Department of Boating and Waterways 2006).

 Egeria densa occurs in Lake County, Illinois (Illinois Database of Aquatic Non-native Species 2014, Lake 

County Health Department and Community Health Center 2009, New Invaders Watch Program 2014), which is 

near Lake Michigan; however, it is unlikely this occurrence of this species is in a water body connected to the 

Great Lakes. Thus, it occurs within 100 km of the Great Lakes basin, but dispersal to the basin is blocked. 

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 This plant often grows in dense mats, becoming entangled on boat propellers and trailer wheels or captured in 

bilge water. Attached fragments can then be transported between water bodies (Washington State Department 

of Ecology 2013).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5√

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U 

 The location of the current closest population of E. densa is not known, but previous records have been 

documented in Great Lakes states, including Minnesota and Indiana: 

o This species was found in 2007 in Powderhorn Lake, Minneapolis, MN but has been eradicated 

and not found since (City of Minneapolis 2013).

o In Indiana, a 2004 infestation of Griffy Lake was subsequently treated and has not been detected 

since 2008 (S. Cotter, City of Bloomington Parks and Recreation Department, Natural Resources 

Manager, pers. comm. 2012; Long 2008).

 More distant but persistent populations of this species can be found in California and Washington state:
1356

o In Long Lake, Washington, E. densa comprised approximately 90% of the aquatic vegetation and 

persisted despite of 19 years of management that included a drawdown and harvesting (Jacoby et 

al. 2001).

o Subject to an intensive chemical control program, E. densa was documented in 2000 as covering 

3,900 acres of California’s Sacramento-San Joaquin Delta and spreading at a rate of 100 

acres/year (California Department of Boating and Waterways 2006).

 Egeria densa occurs in Lake County, Illinois (Illinois Database of Aquatic Non-native Species 2014, Lake 

County Health Department and Community Health Center 2009, New Invaders Watch Program 2014), which is 

near Lake Michigan; however, it is unlikely this occurrence of this species is in a water body connected to the 

Great Lakes. Thus, it occurs within 100 km of the Great Lakes basin, but dispersal to the basin is blocked. 

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Egeria densa is sold in aquarium stores (Cohen et al. 2007), online retailers (e.g. Petco), and biological supply 

companies (e.g., Carolina.com).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1 √

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Egeria densa is one of the most common species sold in the aquarium trade (Cohen et al. 2007).

 However, sale of this species is banned in Minnesota (USDA Plant Industry Division 2005), Indiana (IN NRC 

2012), Illinois (USDA Plant Industry Division 2005), Michigan (USDA Plant Industry Division 2005), and 

Wisconsin (WIDNR 2012).

 This plant’s sale is not regulated in New York, Ohio, or Pennsylvania (USDA Plant Industry Division 2005).

 The sale of E. densa does not appear to be regulated in Ontario or Quebec, despite attempts to find resources 

on this subject.

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

100 √
1357

Great Lakes region.

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Egeria densa is a popular submerged oxygenating pond plant (Haramoto and Ikusima 1988) and is likely 

planted in the Great Lakes region.

 This plant is also frequently mislabeled at pet stores and sold under unregulated plant names (June-Wells 

2012).

 As an ornamental plant, E. densa is planted in water gardens (INDNR 2013).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

√

Unknown U 

 This plant can be purchased via the Internet (e.g., greenvista.com) from states in the Great Lakes basin where 

its sale is unregulated (e.g., Ohio) and planted in states that have regulations. Many websites that sell this plant 

leave it up to the buyer to check state regulations (e.g., plantedaquariumcentral.com) and may not post current 

state regulations.

 As an ornamental plant, E. densa is planted in water gardens (INDNR 2013).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0

Unknown U √

 This species has been maintained in in-ground tanks in the state of Michigan as part of an overwintering study 

(MI DEQ 2013).

 Egeria densa is also capable of being sold from companies culturing it (e.g., greenvista.com) and transporting it 

to and from states in the Great Lakes basin. For example, Ohio has no regulations on this plant and therefore 

its transportation from that part of the basin is unlikely to be monitored.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes Score x 0.75
1358

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U √

 The use of this plant in experiments in Michigan is highly regulated (Michigan.gov 2007).

 Live transport of this plant within the Great Lakes basin or within 20 km of its connecting waters is capable of 

occurring due to levels of state regulations varying throughout the Great Lakes basin.

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 This plant is not likely to be taken up in the ballast of transoceanic ships.

 This species is capable of adapting to many of the possible changes in its environment. It endures well in low 

light conditions (Lara et al. 2002). It also has the ability to overwinter (Rixon et al. 2005).

 This plant can tolerate a wide range of nutrient levels (Yarrow et al. 2009).

 The ability of this plant to tolerate many different environmental conditions makes it capable of living on or in 

boats and boating gear for long periods of time (Yarrow et al. 2009).

 This plant cannot survive in saltwater, but it can tolerate water with a salinity concentration of 8 ppt 

(Hauenstein and Ramirez 1986).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1
1359

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x U U Unknown

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.5 50 Moderate

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 0.25 25 Low

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

U x U U Unknown

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 3 Confidence Level Low
1360

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Egeria densa has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Egeria densa has broad physiological tolerances. It can tolerate low light conditions (Lara et al. 2002). 

Although a tropical plant, it is able to adapt to seasonal changes and overwinter (INDNR 2013, Parsons 

and Cuthbertson 2001, Rixon et al. 2005, Yarrow et al. 2009). It can tolerate low levels of CO2 (Casati et 

al. 2000), nitrogen, phosphorus, and nutrients (Yarrow et al. 2009). This species can survive in waters 

with salinities up to 8 ppt (Hauenstein and Ramirez 1986).This species is known to have a relatively fast 

growth rate (Yarrow et al. 2009). 

Moreover, the introduced ranges of Egeria densa have similar climate and abiotic conditions as the Great 

Lakes. Egeria densa has established near the Great Lakes previously (e.g. Griffy Lake, Indiana), in areas 

that have similar water temperature and dissolved oxygen levels (Long 2008, NOAA CoastWatch 2014). 

This species can survive in freshwater habitats of varying temperatures, light levels, and CO2 levels; thus 

suitable habitats are readily available in the Great Lakes region. Turbidity and nutrient levels of the Great 

Lakes is likely suitable for E. densa to obtain sufficient light, phosphorus, and nitrogen. It is likely that 

Egeria densa will benefit from the effects of climate change, including warmer temperatures and shorter 

duration of ice cover. Increased salinization due to climate change may negatively impact this species’ 

establishment if salinities exceed 8 ppt (Hauenstein and Ramirez 1986). Grass Carp preys on E. densa and 

occurs in the Great Lakes region (Anderson et al. 2008, Hoshovsky and Anderson 2001, Parsons and 

Cuthbertson 2001), but it is not likely that it will prevent the establishment of E. densa in the Great Lakes. 

Each year, it is estimated that 188 E. densa individuals enter the St. Lawrence Seaway through disposal of 

aquarium plants (Cohen et al. 2007).

Egeria densa reproduces asexually via vegetative fragmentation (Hoshovsky and Anderson 2001), which 

may aid its establishment in the Great Lakes region. This species spreads rapidly by vegetative 

fragmentation and recreational activities, resulting in dense mats (INDNR 2013). 

E. densa has established extensively in 27 countries beyond its native range (Curt et al. 2009). In 

Australia, E. densa spread quickly; over a period of two years, it doubled its biomass and doubled the area 

it occupied in the Hawkesbury-Nepean River (Roberts et al. 1999). It is difficult to control once 

established (Yarrow et al. 2009) and it is recommended to correctly identify the plant due to its 

similarities with native plants (INDNR 2013). Grass Carp is used as a biological control in California 

(Hoshovsky and Anderson 2001). In Griffy Lake, Indiana, fluridone successfully removed E. densa, but 

also caused the mortality of all aquatic plants (Jones 2006). Physical removal is not recommended as it 

can result in vegetative fragmentation and encourages dispersal of E. densa (Parsons and Cuthbertson 

2001). 

The model developed by Rixon et al. (2005) predicts that E. densa poses a threat to the Great Lakes. 

Egeria densa may have the potential to compete with native species. In the Hawkesbury-Negean River, 

increased spread of E. densa resulted in the displacement and reduced abundance of the native vallisneria 

Vallisneria americana (Roberts et al. 1999). It is suspected that competition for light was responsible for 

the decline in vallisneria, and that floods were responsible for the rapid spread of E. densa. 
1361

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

7

 This species can survive in salinity levels of up to 8 ppt (Hauenstein and Ramirez 1986).

 This species does well in low light conditions. Its apical shoots actually grow more rapidly when there is a lack 

of light (Lara et al. 2002).

 This plant has the ability to adapt to seasonal changes in temperature of 3-35 ̊C (Yarrow et al. 2009).

 This species has considerable adaptations to low CO2 levels (Yarrow et al. 2009).

 This species is capable of obtaining nitrogen or phosphorous nutrients from the sediment or water column and 

can grow in low levels of these nutrients (Yarrow et al. 2009).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 This plant has the ability to adapt to seasonal changes in temperature of 3-35 ̊C (Yarrow et al. 2009).

 This species does well in low light conditions. Its apical shoots actually grow more rapidly when there is a lack 

of light (Lara et al. 2002).

 This species has considerable adaptations to low CO2 levels (Yarrow et al. 2009).

 This species has an overwintering population in Connecticut that has been documented growing rapidly since 

2009 (Connecticut Agricultural Experiment Station 2013). This region is closely related to the Great Lakes 

region.

 It has been found overwintering in Indiana (INDNR 2013). 

3) If this species is a heterotroph, how would the flexibility of its diet be described?
1362

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

 This species is an autotroph.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Egeria densa outcompeted at least three different native plant species between the years 1996-1999 in the Duck 

Lake Waterways of Washington state (Washington State Department of Ecology 2013).

 Brazilian Elodea forms dense monospecific stands that restrict water movement, trap sediment, and cause 

fluctuations in water quality (Washington State Department of Ecology 2013).

 Egeria densa may have the potential to compete with native species. In the Hawkesbury-Negean River, 

increased spread of E. densa resulted in the displacement and reduced abundance of the native vallisneria 

Vallisneria americana (Roberts et al. 1999). It is suspected that competition for light is responsible for the 

decline in vallisneria, and that floods are responsible for the rapid spread of E. densa.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 This aquatic plant species has a high fecundity (WIDNR 2013).
1363

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 This plant produces via vegetative reproduction in the United States even though it is a dioecious plant. Only 

male plants have been recorded in North America (Robinson 2007); therefore, there is no seed reproduction 

outside of its native range. 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

7

 This species has been known to establish in the temperate and subtropical regions of 27 different countries 

(Curt et al. 2009).

 This plant is established in 40 out of 50 United States states, including Illinois, Indiana, Ohio and New York

(USDA NRCS 2013).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9
1364

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

7

 Brazilian elodea is native to the central Minas Geraes region of Brazil and to the coastal areas of Argentina 

and Uruguay (Washington State Department of Ecology 2013).

 Brazilian elodea has also spread to New Zealand, Australia, Hawaii, Denmark, Germany, France, Japan, and 

Chile. In the United States, this plant has spread to fresh inland waters from Washington to Massachusetts, 

California, and Florida (Washington State Department of Ecology 2013).

 This plant is highly plastic depending on environmental conditions (Washington State Department of Ecology

2013).

 This species has been known to establish in the temperate and subtropical regions of 27 different countries 

(Curt et al. 2009).

 This plant has established itself in 40 out of 50 of the states in the United States (USDA NRCS 2013).

 Many of the abiotic factors in the introduced as well as native area are similar to the Great Lakes.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 This plant can grow in depths of up to 20 ft and drifting (Washington State Department of Ecology 2013).

 This plant has the ability to adapt to seasonal changes in temperature of 3-35 ̊C (Yarrow et al. 2009).

 This species does well in low light conditions. Its apical shoots actually grow more rapidly when there is a lack 

of light (Lara et al. 2002).

 This species has considerable adaptations to low CO2 levels (Yarrow et al. 2009).

 Egeria densa is likely to establish in Great Lakes marshes (MIDNR 2013).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 3
1365

better environment for establishment and spread of this species)

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 This species can survive in salinity levels only up to 8 ppt (Hauenstein and Ramirez 1986). Therefore, increased 

salinization would negatively impact the establishment of Egeria densa.

 Changed water flow and waves increase fragmentation (California Invasive Plant Council 2015). Therefore, 

altered streamflow patterns might aid in establishment of this plant.

 This plant initiates growth at 10 ̊C (Washington State Department of Ecology 2013). Therefore, higher 

temperatures and less ice cover in the Great Lakes region would aid this plant in reproduction.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

8

 This species is capable of obtaining nitrogen or phosphorous nutrients from the sediment or water column and 

can grow in low levels of these nutrients (Yarrow et al. 2009).

 This species does well in low light conditions. Its apical shoots actually grow more rapidly when there is a lack 

of light (Lara et al. 2002).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3
1366

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by the species being assessed.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There are no known species in the Great Lakes that can aid in the establishment of this species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0
1367

Unknown U

-10%

 The Grass Carp has been known to consume Egeria densa (GISD 2005a).

 Triploid (sterile) Grass Carp are in four out of five of the Great Lakes already, but in relatively low abundance

(Congress Research Service 2012).

 Grass Carp is used as a biological control in California (Hoshovsky and Anderson 2001).

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

7

 A study of the Montreal, Quebec aquarium trade estimates that up to 188 E. densa plants enter the St. Lawrence 

Seaway each year (Cohen et al. 2007).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This plant is known to have established in 27 countries outside its natural habitat range (Curt et al. 2009).

 This plant has established itself in 40 out of 50 United States states (USDA NRCS 2013).

 It occurs in Alabama, Arkansas, Colorado, Delaware, Florida, Georgia, New Jersey, New Mexico, North 

Carolina, Oklahoma, Oregon, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, West Virginia, 

Mexico, West Indies, Central America (Flora of North America Editorial Committee 2000).

 Egeria densa is declared a weed in Tasmania, Australia (Parsons and Cuthbertson 2001) and Argentina 

(Cabrera Walsh et al. 2013). 
1368

 Egeria densa has been reported in Bogakain Lake, Bangladesh in 2010 (Alumujaddade Alfasane et al. 2010).

 This species is historically introduced outside its native range through the aquarium trade and is considered 

naturalized in parts of Chile, England, Mexico, New Zealand, and the United States (Cabrera Walsh et al. 

2013). 

 This species occurs in Siera Nevada, Central Valley, central coast of San Francisco Bay, and Jan Jacinto 

Mountains, California (Hoshovsky and Anderson 2001).

 This species occurs in southern Vermont, eastern Massachussetts, and Long Island, New York (Magee and 

Ahles 2007)

 This species has spread in Australia, and it is suspected that large floods caused its rapid spread (Roberts et al. 

1999).

 Egeria densa has been reported in 2014 in Lake County, Illinois (New Invaders Watch Program 2014, Illinois 

Database of Aquatic Non-native Species 2014).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9

 This species establishes very rapidly once it is introduced (California Invasive Plant Council 2015).

 In Australia, E. densa spread quickly; over a period of two years, it doubled its biomass and doubled the area it 

occupied in the Hawkesbury-Nepean River (Roberts et al. 1999). It is suspected that significant flood events 

during that period were responsible for its rapid spread. 

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-30%
1369

 Surveillance and management efforts are currently underway to detect, control and/or eradicate this plant in 

Michigan (MI DEQ 2013). However, a basin-wide monitoring program is lacking (Dupre 2011).

 This species is very hard to eradicate once established (Yarrow et al. 2009).

 It is difficult to control E. densa and it is recommended to correctly identify the plant due to its similarities with 

native plants (INDNR 2013). 

 Grass Carp is used as a biological control in California (Hoshovsky and Anderson 2001).

 In Griffy Lake, Indiana, fluridone successfully removed E. densa, but also caused the mortality of all aquatic 

plants (Jones 2006). 

 Physical removal is not recommended as it can results in vegetative fragmentation and encourages dispersal of 

E. densa (Parsons and Cuthbertson 2001).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 107

>100 High Adjustments

B. Critical species A*(1-0%) 107

51-99 Moderate C. Natural enemy B*(1-10%) 96.3

Control measures C*(1-30%) 67.41

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Egeria densa has the potential for high environmental impact if introduced to the Great Lakes.

Egeria densa acts as an ecosystem engineer by preventing the resuspension of sediments and controlling 

light and nutrient availability (Yarrow et al. 2009). The dense growth of E. densa can retard water flow 

and reduce turbidity (Parsons and Cuthbertson 2001). This species can reduce the abundance and 
1370

diversity of native plant seeds in lake bottoms due to increased sediment accumulation under its weed 

beds (Hoshovsky and Anderson 2001). Egeria densa removes nutrients from the water column, thereby 

decreasing the standing stock of phytoplankton (Yarrow et al. 2009). Furthermore, Egeria densa forms 

mats that can shade out phytoplankton.

Egeria densa can outcompete native species. In Duck Lake, Washington, E. densa displaced native 

stonewart, elodea, and pondweed in a period of 3 years (Washington State Department of Ecology 2013). 

In Hawkesbury-Negean River, Australia, evidence suggests that E. densa outcompeted native vallisneria 

(Vallisneria americana) for light (Roberts et al. 1999).

Egeria densa is not known to pose a threat to the health of native species. This species is not known to 

alter predator-prey relationships or genetically affect native populations. 

Egeria densa has the potential for high socio-economic impact if introduced to the Great Lakes. 

The dense growth of E. densa can interfere with irrigation projects, hydroelectric dams, and urban water 

supply (Hoshovsky and Anderson 2001, Parsons and Cuthbertson 2001). In New Zealand, there was an 

infestation of E. densa in the Wikato River that clogged the water intake pipes resulting in the shut-down 

of an electrical plant (Washington State Department of Ecology 2013). 

Egeria densa can inhibit recreational activities as a nuisance for navigation, fishing, swimming, and water 

skiing (Washington State Department of Ecology 2013). The removal of E. densa is costly; Washington 

local and state governments spend thousands of dollars each year to control the species. Egeria densa

may pose a risk to human safety. In 2006, police reports indicate that E. densa may have contributed to 

the death of a physician in San Joaquin County, who drowned after becoming entangled in the “tentaclelike Delta weeds trap” in attempts to save his nephew (Breitler 2006, Victorian Department of Industries

2013). 

Egeria densa has gained widespread recognition by parks departments and local and state governments as 

a nuisance species (GLPANS 2012, Lake County Health Department and Community Health Center 

2009, Mcglynn 2013). Resources have been devoted in various cities and states to remove infestations of 

E. densa due to its costly impacts on water supply, infrastructure, and recreation (California State Parks 

2014, INDNR 2013).

Egeria densa has the potential for moderate beneficial impact if introduced to the Great Lakes.

It is an ornamental plant for aquariums and small ponds. Egeria densa has been recommended as a 

submerged oxygenator plant for water gardens (Creative Homeowner 2010). Egeria densa is also utilized 

in plant biology classes for students to study photosynthesis (Berkeley 2014).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?
1371

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0 √

Unknown U

 Egeria densa is not known to be hazardous to native species’ health.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 In the Duck Lake waterways of Washington state, within a matter of three years, stonewart, native elodea, and 

pondweed were displaced completely by thick dense mats of Egeria densa (Washington State Department of 

Ecology 2013).

 Egeria densa may have the potential to compete with native species. In the Hawkesbury-Negean River, 

increased spread of E. densa resulted in the displacement and reduced abundance of the native vallisneria 

Vallisneria americana (Roberts et al. 1999). It is suspected that competition for light is responsible for the 

decline in vallisneria, and that floods are responsible for the rapid spread of E. densa.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1

Not significantly 0 √

Unknown U 

 Egeria densa is not known to alter predator-prey relationships.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6
1372

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0

Unknown U √

 There are no known native populations that have been affected genetically by this plant at the time of this 

assessment.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 The dense mats of this plant deplete water oxygen levels and restrict water movement while trapping sediment, 

leading to fluctuations in water quality (Queensland Department of Agriculture 2011).

 The dense growth of E. densa can retard water flow (Parsons and Cuthbertson 2001).

 This species can reduce the abundance and diversity of native plant seeds in lake bottoms due to increased 

sediment accumulation under its weed beds (Hoshovsky and Anderson 2001).

 This species may remove nutrients from the water column (Yarrow et al. 2009).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U

 Egeria densa populations in its native range negatively affect many phytoplankton and macrophyte communities 

(Mazzeo et al. 2003).

 Egeria densa grows in dense mats that block light penetration and often displace native plants (Queensland 

Department of Agriculture 2011).

 Egeria densa populations change the available habitat for fish and waterfowl (Queensland Department of 

Agriculture 2011).

 Egeria densa acts as an ecosystem engineer, by preventing the resuspension of sediments, controlling nutrient 

availability (and phytoplankton growth) by removing nutrients from the water column (Yarrow et al. 2009).
1373

Environmental Impact Total 18

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6 √

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U

 The extreme dense mats of this plant can cause drowning by entanglement (Victorian Department of Industries

2013). The risk would be greatest during highest biomass levels (Victorian Department of Industries 2013).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 In New Zealand, electric generating plants were shut down when fragments of Brazilian Elodea clogged intake 

structures on the Waikato River (Washington State Department of Ecology 2013).

 In Washington State, local and state government and lake residents spend thousands of dollars every year to 

manage Brazilian Elodea infestations. The cost of the control project in Silver Lake, Cowlitz County is over one 

million dollars (Washington State Department of Ecology 2013).
1374

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 Egeria densa does not appear to have direct effects on water quality in terms of human use.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 √

Not significantly 0 

Unknown U

 Dense underwater growth of E. densa significantly retards water flow, interfering with irrigation projects, 

hydroelectric utilities, and urban water supplies (California Invasive Plant Council 2015).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U

 Dense beds of this species can interfere with recreational uses of a waterbody by interfering with navigation, 

fishing, swimming, and water skiing (Washington State Department of Ecology 2013).

 In Washington State, local and state government and lake residents spend thousands of dollars every year to 

manage Brazilian Elodea infestations. The cost of the control project in Silver Lake, Cowlitz County is over one 

million dollars (Washington State Department of Ecology 2013).

 Dense E. densa populations have caused significant negative effects in the fishing industry (NSW DPI 2013b).

 These weeds spread downstream and become entangled in nets in large quantities. This affects the viability of 

the fishery, requiring fishers to move downstream from local and peak trawl grounds. Labor is increased, and 

travelling and trawl hours are affected (NSW DPI 2013b).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6 √

Yes, but negative consequences have been small 1 

Not significantly 0 

Unknown U
1375

 An estimated 1500 acre feet of water storage capacity were lost annually in Lake Marion, South Carolina due 

to sedimentation caused by Brazilian Elodea growth (Washington State Department of Ecology 2013).

 Egeria densa has gained widespread recognition by parks departments and local and state governments as a 

nuisance species (City of Minneapolis 2013, GLPANS 2012). Resources have been devoted in various cities and 

states to remove infestations of E. densa due to itscostly impacts on water supply, infrastructure, and recreation 

(California State Parks 2014, INDNR 2013).

Socio-Economic Impact Total 25

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 Egeria densa is not known to act as a biological control.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U
1376

 This plant is sold for aquaculture use in home aquariums and is hardy, making it good for beginners (City of 

Bloomington (Indiana) 2013).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This plant is sold for aquaculture use in home aquariums and is hardy, making it good for beginners (City of 

Bloomington (Indiana) 2013).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 It is also a good plant to use in slides to study plant biology (WIDNR 2013).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

 Egeria densa is not known to improve water quality.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 Egeria densa is not known to have any positive ecological effects.
1377

Beneficial Effect Total 3

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1378

Scientific Name: Eichhornia crassipes

(Mart.) Solms

Common Name: Water Hyacinth

Synonyms: Common Water-Hyacinth, Floating Water-Hyacinth, Eichhornia speciosa Kunth, Piaropus 

crassipes (Mart.) Raf.

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High

Hitchhiking/fouling: High

Unauthorized intentional release: High

Stocking/planting/escape from recreational culture: Moderate

Escape from commercial culture: Moderate

Transoceanic shipping: Unlikely

Eichhornia crassipes has a high probability of introduction to the Great Lakes (Confidence level: 

High). 

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentional 

Release, Escape from Recreational and Commercial Culture

Eichhornia crassipes occurs near waters connected to the Great Lakes basin. This species has been 

reported to occur in Lake St. Clair and the Detroit River in 2010 (Adebayo et al. 2011). In Michigan, it 

has been found in Oakland, Livingston, Wayne, and St. Clair counties (Ankney 2012). Clonal individuals 

of Eichhornia crassipes can disperse to new areas when fragments are transported by water (Masterson 

2007). Eichhornia crassipes forms thick mats that can become entangled on to boat propellers and trailers 

to be spread to other water bodies. For instance, boats coming from water bodies such as Lake St. Clair or 

the Detroit River may unintentionally transport E. crassipes to Lake Erie. 

Eichhornia crassipes is sold at aquarium stores and is sold in the Great Lakes. This species is a popular 

aquarium plant and is available for purchase in the Great Lakes region. Eichhornia crassipes may be 

frequently introduced into waterways after disposal of the plant from water gardens (Adebayo et al. 

2011). In a survey of aquarium stores near Lakes Erie and Ontario, E. crassipes was available for 

purchase in 30% of the stores (Rixon et al. 2005). Title 18 U.S. Code 46 states that it is a violation of the 

law to knowingly transport E. crassipes in interstate commerce, and to sell or purchase the plant (18 

U.S.C. § 46). The sale of this species is prohibited in Chicago and Illinois State, but not in Indiana, 

Michigan, Minnesota, New York, Ohio, Ontario, Pennsylvania, Quebec, or Wisconsin (GLPANS 2012).
1379

Greenhouses within the Great Lakes basin commercially culture and sell E. crassipes (e.g. Countryside 

Greenhouse Allendale, MI) for use in water gardens, thus, it may escape and spread into larger water 

bodies. Retailers advertise the E. crassipes as a good oxygenator plant for ponds. 

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Eichhornia crassipes has been found in Oakland, Livingston, Wayne, and St. Clair counties in the state of 

Michigan. These occurrences are located near tributaries that connect to the Great Lakes (Ankney 2012). 

Eradication at these sites was scheduled to begin in 2013 (Ankney 2012).

 Clonal individuals can form through vegetative reproduction of fragmented rosettes, which can then disperse by 

wind and water movement (Masterson 2007).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Water Hyacinth was found in Lake St. Clair and the Detroit River in 2010 (Adebayo et al. 2011).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 This species reproduces chiefly by vegetative means and can quickly form dense floating mats of vegetation.
1380

 Dense mats of this species can become entangled in boat propellers and trailers (North American Invasive 

Species Network 2013).

 Seeds are the main source of new infestations and are carried in water and mud (e.g., on machinery or boots), 

as well as by birds (NSW DPI 2012b)

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1 √

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 Water Hyacinth was found in Lake St. Clair and the Detroit River in 2010 (Adebayo et al. 2011).

 Eichhornia crassipes has been found in Oakland, Livingston, Wayne, and St. Clair counties in the state of 

Michigan. These occurrences are located near tributaries that connect to the Great Lakes (Ankney 2012).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 This species can be purchased from many online retailers (e.g., pondplantsforsale.com).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1 √

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 This plant is both widely popular and frequently sold in the Great Lakes region (WIDNR 2013).

 There are no restrictions in the Great Lakes basin banning the sale of this species (USDA NRCS 2013), except 

for a federal statute banning interstate commerce of this species (18 USC § 46).

 The sale of this species is prohibited in Chicago and Illinois State, but not in Indiana, Michigan, Minnesota, 

New York, Ohio, Ontario, Pennsylvania, Quebec, or Wisconsin (GLPANS 2012).

 In a survey of aquarium stores near Lakes Erie and Ontario, E. crassipes was available for purchase in 30% of 

the stores (Rixon et al. 2005).
1381

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Greenhouses within the Great Lakes basin (e.g., Countryside Greenhouse in Allendale, MI), sell this plant and 

mention its use in their outdoor water gardens.

 Retail advertisements also recommend this species as a good oxygenator plants for outdoor ponds.

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75 

√

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 Greenhouses within the Great Lakes basin (e.g., Countryside Greenhouse in Allendale, MI), sell this plant and 

mention its use in their outdoor water gardens.

 There are no restrictions in the Great Lakes basin banning its sale (USDA NRCS 2013).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100 √

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U

 Greenhouses within the Great Lakes basin (e.g., Countryside Greenhouse in Allendale, MI), sell this plant and 

mention its use in their outdoor water gardens.

5b) What is the nature and proximity of this activity to the Great Lakes basin?
1382

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75 

√

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

 Greenhouses within the Great Lakes basin (e.g., Countryside Greenhouse in Allendale, MI), sell this plant and 

mention its use in their outdoor water gardens.

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 Water Hyacinth is tolerant of a wide range of conditions, including frost, but not brackish or sea strength 

salinity (NSW DPI 2012b).

 This species optimum temperature range for growth is 28-30 ̊C, and it requires ample nitrogen, phosphorus, 

and potassium (NSW DPI 2012b).

 If air temperature remains at 5 ̊C for 2-3 weeks, Water Hyacinth regrowth will significantly decrease (Owens 

and Madsen 1995).

 This species seeds can remain viable for up to 5-20 years (FAO 2013).

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great Score x 0.1
1383

Lakes nor in ports in direct trade with the Great Lakes.

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 0.75 75 Moderate

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x 0.75 75 Moderate

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
1384

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Eichhornia crassipes has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Eichhornia crassipes has been reported to tolerate salinities of 0-8.8 ppt, with growth rate decreasing with 

increasing salinity (Rotella and Luken 2012). This species tolerates water temperatures of 5°C for short 

periods of time (Owens and Madsen 1995) and survives in water temperatures up to 30°C (NSW DPI 

2012b). Eichhornia crassipes requires abundant nitrogen, phosphorus, and potassium for growth. The

abiotic and climatic conditions of the introduced ranges of E. crassipes (e.g. Lake St. Clair, Detroit River, 

New York) are similar to the Great Lakes. Nutrient inputs to the Great Lakes from runoff may provide the 

necessary nitrogen and phosphorus levels for E. crassipes growth. Slow flowing fresh water bodies 

located in the Great Lakes basin may provide suitable habitats for this species.

Eichhornia crassipes is somewhat likely to be able to overwinter in the Great Lakes basin as rooted 

plants, which are more resistant to freezing temperatures than free floating mats (Owens and Madsen 

1995). There is anecdotal evidence that E. crassipes has overwintered in private ponds in Michigan 

(Ankney 2012). Eichhornia crassipes may experience increased mortality and reduced regrowth after 

long periods of near-freezing temperatures (Adebayo et al. 2011, Owens and Madsen 1995, Rixon et al. 

2005). Climate change may make the Great Lakes more suitable for this species’ establishment. Shorter 

ice duration and warmer temperatures may improve this species’ ability to survive the winter in the Great 

Lakes (Adebayo et al. 2011). 

It produces seeds that can remain viable for 5-20 years (FAO 2013). Although it is capable of producing 

dormant seeds, evidence suggests that E. crassipes will not establish a population in the Great Lakes 

region via sexual reproduction due to the lack of genetic diversity of the introduced populations and the 

lack of seeds found in the sediment where it has been introduced (Adebayo et al. 2011). Its primary 

method of spread is through vegetative fragmentation (NSW DPI 2012b). This species rapidly grows and 

can double its biomass every 2 to 34 days (Gutiérrez et al. 2001).

Eichhornia crassipes forms dense stands, which may impact species in the Great Lakes. In San Joaquin 

Delta, California, insect densities where lower in patches of E. crassipes and there was a difference in 

insect composition between E. crassipes and the native pennywort (Hydrocotyle umbellata) (Toft 2000). 

Non-native introduced amphipods such as Crangonyx floridanus were more abundant in E. crassipes

stands than in the native pennywort stands, and are not frequently consumed by fish. Fish preyed heavily 

on native amphipod Hyalella azteca that was more abundant in the native pennywort. It is suggested that 

the presence of E. crassipes may influence native invertebrate community assemblages. In Lake 

Okeechobee, E. crassipes displaced native bulrush and shaded out native submerged plants that provide 

important habitats for fish, waterfowl, and other animals (UF IFAS 2013). In Caohai and Dianchi lakes in 

Yunnan province, southwestern China, E. crassipes had competed with native plants for water, nutrients, 

and space, and contributed to the reduction in native plant diversity (Jianqing et al. 2001). 

Control methods include mechanical pulling, biological control, and herbicide. The most effective control 

method is 2,4-D herbicide, which kills E. crassipes and reduces the populations of native species to some 

extent (Ivanov et al. 2007). Surveillance and management efforts are currently underway to detect, 

control, and/or eradicate this plant in Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). 
1385

However, a basin-wide monitoring program is lacking (Dupre 2011). Michigan has a state management 

plan to prevent aquatic invasive species introductions, limit their dispersal, and control their populations 

(MI DEQ 2013). The Michigan Department of Natural Resources and the United States Environmental 

Protection Agency (USEPA) have an early detection and rapid response plant regarding the establishment 

of E. crassipes (Ankney 2012). 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

5

 Estimates for the lethal level of salinity for Water Hyacinth range from roughly 2-8 ppt (Rotella and Luken 

2012).

 If air temperature remains at 5 ̊C for 2-3 weeks, Water Hyacinth has a significant decrease in regrowth (Owens 

and Madsen 1995).

 Optimum growth of this species occurs at temperatures between 28°C and 30°C, and requires abundant 

nitrogen, phosphorus, and potassium (NSW DPI 2012b).

 Although this plant will tolerate a wide range of growth conditions and climatic extremes including frost, it is 

rapidly killed by sea strength salinity and will not grow in brackish water (NSW DPI 2012b).

 Water Hyacinth seeds can remain viable for up to 5-20 years (FAO 2013).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 Water Hyacinth seeds can remain viable for up to 5-20 years (FAO 2013).
1386

 Although it is capable of producing dormant seeds, evidence suggests that E. crassipes will not establish a 

population in the Great Lakes region via seeds due to the lack of genetic diversity of the introduced populations 

and the lack of seeds found in the sediment where it has been introduced (Adebayo et al. 2011).

 However, there is anecdotal evidence that E. crassipes has overwintered in private ponds in Michigan (Ankney 

2012).

 Water Hyacinth does not tolerate long exposure to temperatures lower than 0°C. Short-term exposure to 

temperatures at or below freezing can be tolerated (IPAMS 2013).

 It is not known as an overwintering species in Rixon et al. (2005).

 Eichhornia crassipes may experience increased mortality and reduced regrowth potential after long periods of 

near-freezing temperatures (Adebayo et al. 2011, Owens and Madsen 1995, Rixon et al. 2005).

 In Dallas, Texas, water hyacinth populations were completely killed during one winter (Owens and Madsen 

1995). The winter of 1990-1991 there was a period of 11 days with the minimum air temperature below 

freezing.

 Rooted plants are more resistant to overwintering than floating mats (Owens and Madsen 1995).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

 This species is an autotroph.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 Eichhornia crassipes may form dense, single species stands that often do not provide ideal habitat or food for 

native wildlife and may limit access to the water for some species. These native wildlife populations may be 

forced to relocate or perish, ultimately resulting in a loss of biodiversity and a disruption in the balance of the 

ecosystem (Robinson 2007).
1387

 In Lake Okeechobee, water hyacinth displaced native bulrush and shaded out native submerged plants that are 

important habitat for fish, waterfowl, and other animals. Water hyacinth infestations also interfere with the 

nesting and feeding habits of the endangered Everglades snail kite, and in extreme cases can push over or 

uproot emergent vegetation in which kites build their nests (UF IFAS 2013).

 Eichhornia crassipes forms dense stands, which may impact species in the Great Lakes. In San Joaquin Delta, 

California, insect densities where lower in patches of E. crassipes and there was a difference in insect 

composition between E. crassipes and the native Pennywort (Hydrocotyle umbellata)(Toft 2000). Non-native 

introduced amphipods such as Crangonyx floridanus were more abundant in E. crassipes than in the native 

pennywort, and are not frequently consumed by fish. Fish preyed heavily on native amphipod Hyalella azteca

that was more abundant in the native Pennywort. It is suggested that the presence of E. crassipes may influence 

native invertebrate community assemblages.

 In Caohai and Dianchi lakes in Yunnan province, southwestern China, E. crassipes had competed with native 

plants for water, nutrients, and space, and contributed to the reduction in native plant diversity (Jianqing et al. 

2001).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 This species has a high fecundity (WIDNR 2013).

 This species exhibited a biomass doubling time of 2.03-34.66 days (Gutiérrez et al. 2001).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

8

 Water Hyacinth reproduces largely via clonal growth, though sexual reproduction also may occur with 

production of seeds but at reduced frequency in introduced, temperate populations (Adebayo et al. 2011).
1388

 Although it is capable of producing dormant seeds, evidence suggests that E. crassipes is not very likely to 

establish a population in the Great Lakes region via seeds due to the lack of genetic diversity of the introduced 

populations and the lack of seeds found in the sediment where it has been introduced in Lake St. Clair and the 

Detroit River (Adebayo et al. 2011).

 This same paper predicts this plant could be introduced into the Great Lakes after disposal of the plant into the 

St. Clair and the Detroit River and subsequent dispersal (Adebayo et al. 2011).

 Since Water Hyacinth reproduces sexually by seeds, the chances are higher of developing a cold-tolerant 

ecotype than if it reproduced only vegetatively (Washington State Department of Ecology 2013).

 This species reproduces by vegetative fragmentation (NSW DPI 2012b), which may aid its establishment, but 

there is no literature regarding its establishment in the Great Lakes. 

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 Water Hyacinth grows in still or slow-flowing fresh water in tropical and temperate climates (NSW DPI 

2012b).

 Water Hyacinth is an aquatic plant native to the warm climate of the Amazon basin in South America (Ankney 

2012).

 The United States states that have the most similar climatic conditions to where this species is native are New 

York and Washington; furthermore, it is established in the southern part of New York and the southwestern part 

of Washington (USDA NRCS 2013).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 Water Hyacinth grows in still or slow-flowing fresh water in tropical and temperate climates (NSW DPI 

2012b).
1389

 Optimum growth of this species occurs at temperatures between 28°C and 30°C, and requires abundant 

nitrogen, phosphorus, and potassium (NSW DPI 2012b).

 Although this plant will tolerate a wide range of growth conditions and climatic extremes including frost, it is 

rapidly killed by sea strength salinity and will not grow in brackish water (NSW DPI 2012b).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 Water Hyacinth grows in still or slow-flowing fresh water (NSW DPI 2012b).

 Water Hyacinth is a free-floating perennial water plant that forms large, dense mats on the water surface (NSW 

DPI 2012b).

 Eichhornia crassipes is mainly found in inshore and shallow areas to which it is swept by currents and less often 

in patchy offshore areas (Osumo 2001).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 Water Hyacinth grows in still or slow-flowing fresh water in tropical and temperate climates (NSW DPI 

2012b).

 Optimum growth of this species occurs at temperatures between 28°C and 30°C (NSW DPI 2012b).

 Although this plant will tolerate a wide range of growth conditions and climatic extremes including frost, it is 

rapidly killed by sea strength salinity and will not grow in brackish water (NSW DPI 2012b).

 According to recent climate change models, this species’ distribution may expand into higher latitudes as 

temperatures rise, posing problems to formerly hyacinth-free areas (UNEP GEAS 2013).
1390

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

7

 Water hyacinth is a free-floating perennial water plant that forms large, dense mats on the water surface (NSW 

DPI 2012b).

 This plant requires abundant nitrogen, phosphorus, and potassium (NSW DPI 2012b).

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There is no critical species required by the species being assessed.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 9
1391

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There was no record of another species aiding the establishment of this species at the time of this assessment.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 There are no known predators of this plant in the Great Lakes.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3
1392

Infrequent, small or moderate inocula 0

Unknown U

6

 Recolonization ofWater Hyacinth via seeds seems unlikely given the absence of genetic diversity in introduced 

populations and low seed production in temperate areas (Adebayo et al. 2011).

 Fragments of this species are not easily accidentally introduced, but it is often sold and planted (WIDNR 2013).

 Vegetative fragmentation is a primary method for this species spreading (WIDNR 2013).

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species has established in 24 states within the United States (USDA NRCS 2013).

 Water Hyacinth has emerged as a major weed in more than 50 countries (UNEP GEAS 2013).

 In the United States, it is found in California (Toft 2000), Michigan (Ankney 2012, Adebayo et al. 2011), Texas 

(Owens and Madsen 1995), Florida (Ivanov et al. 2007).

 This species occurs in southwestern China (Jianqing et al. 2001)

 Water Hyacinth occurs in the Guadina River basin in Spain (Téllez et al. 2008).

 This species occurs in Australia (NSW DPI 2012b).

 Eichhornia crassipes is found in 50 countries on 5 continents (Lowe et al. 2000)

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

9
1393

 Water Hyacinth has been identified by the International Union for Conservation of Nature (IUCN) as one of the 

100 most aggressive invasive species and recognized as one of the top 10 worst weeds in the world. It is 

characterized by rapid growth rates, extensive dispersal capabilities, large and rapid reproductive output, and 

broad environmental tolerance (UNEP GEAS 2013).

 This species rapidly grows and can double its biomass every 2 to 34 days (Gutiérrez et al. 2001).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-30%

 Surveillance and management efforts are currently underway to detect, control and/or eradicate this plant in 

Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). However, a basin-wide monitoring program is 

lacking (Dupre 2011).

 Michigan has a state management plan to prevent AIS introductions (e.g. water hyacinth), limit their dispersal, 

and to manage and control them (MI DEQ 2013). However, this program may have limited long-term impact, 

as four of the five sites where Water Hyacinth was detected in 2011 were revisited in 2012 and all 4 sites were 

again positive for water hyacinth, each estimated at the same population levels in 2011 

(http://www.michigan.gov/documents/dnr/Water_Hyacinth_in_Michigan_Final_12-6-12_405850_7.pdf). 

 The USEPA and Michigan Department of Natural Resources has an early detection and rapid response plan in 

place to protect the state from establishment of Water Hyacinth (MIDNR 2013).

 Control methods include mechanical pulling, biological control, and herbicide. The most effective control 

method is 2,4-D herbicide, which kills E. crassipes but reduces the populations of native species to some extent 

(Ivanov et al. 2007).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 102

>100 High Adjustments

B. Critical species A*(1 - 0%) 102

51-99 Moderate C. Natural enemy B*(1 - 0%) 102

Control measures C*(1 - 30%) 71.4

0-50 Low Potential for Establishment Moderate
1394

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Eichhornia crassipes has the potential for high environmental impact if introduced to the Great 

Lakes.

Eichhornia crassipes grows in thick mats that reduce the light and oxygen availability in the water 

(Ivanov et al. 2007). After removing E. crassipes from Lake Victoria by cutting, there was a significant 

increase in dissolved oxygen (Osumo 2001). In Africa, Eichhornia crassipes can be detrimental to water 

availability due to its high rate of evapotranspiration and its ability to take advantage of scarce water 

reserves, resulting in an annual loss of 7 billion m3of water from the Nile River (DeGroot 1993, Padilla 

and Williams 2004). In China, E. crassipes has exacerbated water pollution by absorbing heavy metals 

and releasing them at death (Jianqing et al. 2001).

In Lake Okeechobee, E. crassipes displaced native bulrush and shaded out native submerged plants that 

provide important habitats for fish, waterfowl, and other animals (UF IFAS 2013). In Caohai and Dianchi 

lakes in Yunnan province, southwestern China, E. crassipes competed with native plants for water, 

nutrients, and space, and contributed to the reduction in native plant diversity (Jianqing et al. 2001). 

Eichhornia crassipes can potentially alter predator-prey relationships. In San Joaquin Delta, California, 

insect densities where lower in patches of E. crassipes and there was a difference in insect composition 

between E. crassipes and the native pennywort (Hydrocotyle umbellata) (Toft 2000). Non-native 

introduced amphipods such as Crangonyx floridanus were more abundant in E. crassipes than in the 

native pennywort, and are not frequently consumed by fish. Fish preyed heavily on native amphipod 

Hyalella azteca that was more abundant in the native pennywort. It is suggested that the presence of E. 

crassipes may influence native invertebrate community assemblages.

Eichhornia crassipes has the potential for high socio-economic impact if introduced to the Great 

Lakes. 
1395

Eichhornia crassipes can pose a risk to human health by providing a habitat for mosquitos, and may 

increase the risk of mosquito-borne diseases (Jianqing et al. 2001, Mailu 2001). This species has reduced 

water availability in Lake Victoria basin, which led to social conflicts over the lack of clean water (Mailu 

2001). In addition, the infestation of E. crassipes resulted in increased transportation costs, blockage of 

irrigation canals, and difficulties in electricity and water extraction. Due to E. crassipes infestation, the 

Kenyan port of Kisumu reported a 70% decline in economic activities. This species can impact 

recreational fishing by making it difficult to access fishing grounds and preventing boating (Mailu 2001, 

Richardson and van Wilgen 2004).

In Benin, the infestation of E. crassipes was estimated to significantly reduce the annual income of the 

villagers, who relied on fishing and trade for an income (De Groote et al. 2003). Biological control of the 

infested waters in Benin was estimated to be United States $2.09 million. 

Eichhornia crassipes has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

Eichhornia crassipes is an ornamental plant used in water gardens. Eichhornia crassipes has the potential 

to be used for bioethanol and biogas production, electricity generation, industrial uses, animal feed, or 

agriculture (Jafari 2010, Malik 2007). It may be utilized for wastewater treatment or heavy metal 

remediation (Pinto et al. 1987). 

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6 

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Phytoplankton productivity was reduced when Water Hyacinth water present in Lake Naivasha (Kenya), 

which suggests it may alter species composition and biodiversity (Mironga 2006).

 In China, E. crassipes has exacerbated water pollution by absorbing heavy metals and releasing them at 

death (Jianqing et al. 2001).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 1 
1396

fecundity) or decline of at least one native population

Not significantly 0

Unknown U

 Eichhornia crassipes may form dense single species stands that often do not provide ideal habitat or food for

native wildlife and may limit access to the water for some species. These native wildlife populations may be 

forced to relocate or perish, ultimately resulting in a loss of biodiversity and a disruption in the balance of the 

ecosystem (Robinson 2007).

 Dense floating rafts of Eichhornia crassipes can form on the water’s surface, restricting light to the complete 

exclusion of other native plants, and decreasing the air exchange between the water’s surface and the 

atmosphere (Robinson 2007).

 Dense mats of Eichhornia crassipes can lower dissolved oxygen levels in water bodies, leading to reduction of 

aquatic fish production (Shanab et al. 2010).

 Water Hyacinth is very efficient in taking up calcium, magnesium, sulfur, ferric iron, manganese, aluminum, 

boron, copper, molybdenum, zinc, nitrogen, phosphorus, and potassium, favoring its growth over other aquatic 

species (Shanab et al. 2010).

 Eichhornia crassipes is an invasive weed known to out-compete native plants and negatively affect microbes, 

including phytoplankton (Shanab et al. 2010).

 In 1994, about 10 km2of Dianchi Lake in the Yunnan Province of China was completely covered by dense mats 

of Eichhornia crassipes. The rapid spread of this weed has resulted in declines in native aquatic plants and 

threats to local biodiversity (Yan et al. 2001).

 In Lake Okeechobee, water hyacinth displaced native bulrush and shaded out native submersed plants that are 

important habitat for fish, waterfowl, and other animals. Water hyacinth infestations also interfere with the 

nesting and feeding habits of the endangered Everglades snail kite, and in extreme cases can push over or 

uproot emergent vegetation in which kites build their nests (UF IFAS 2013).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6 

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 √

Not significantly 0

Unknown U 

 Eichhornia crassipes forms dense monocultures that can threaten local native species diversity and change the 

physical and chemical aquatic environment, thus altering ecosystem structure and function by disrupting food 

chains and nutrient cycling (Shanab et al. 2010).

 Algae, a major component of the base of the food chain, can be shaded out by dense mats of Eichhornia 

crassipes. The resulting decline in algae can disrupt the entire food web in a water body (Robinson 2007).

 Eichhornia crassipes can potentially alter predator-prey relationships. In San Joaquin Delta, California, insect 

densities where lower in patches of E. crassipes and there was a difference in insect composition between E. 

crassipes and the native pennywort (Hydrocotyle umbellata)(Toft 2000). Non-native introduced amphipods such 

as Crangonyx floridanus were more abundant in E. crassipes than in the native Pennywort, and are not 

frequently consumed by fish. Fish preyed heavily on native amphipod Hyalella azteca that was more abundant 

in the native pennywort. It is suggested that the presence of E. crassipes may influence native invertebrate 

community assemblages.
1397

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

 There were no recorded incidences of genetic effects found at the time of this assessment.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 Eichhornia crassipes forms dense monocultures that can threaten local native species diversity and change the 

physical and chemical aquatic environment, thus altering ecosystem structure and function by disrupting food 

chains and nutrient cycling (Shanab et al. 2010).

 Dense mats of Eichhornia crassipes can lower dissolved oxygen levels in water bodies leading to reduction of 

aquatic fish production (Shanab et al. 2010).

 Dense floating rafts of Water Hyacinth can form on the water’s surface, restricting light to the complete 

exclusion of other native plants, and decreasing the air exchange between the water’s surface and the 

atmosphere (Robinson 2007).

 Water Hyacinth is very efficient in taking up calcium, magnesium, sulfur, ferric iron, manganese, aluminum, 

boron, copper, molybdenum, zinc, nitrogen, phosphorus, and potassium (Shanab et al. 2010).

 Eutrophic conditions arise when this plant dies and decomposes due to the large release of nutrients the plant 

takes in (Shanab et al. 2010).

 After removing E. crassipes by cutting, there was a significant increase in dissolved oxygen (Osumo 2001).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 

Unknown U
1398

 Eichhornia crassipes is known to out-compete native plants and negatively affect microbes, including 

phytoplankton (Shanab et al. 2010).

 Sediment levels increase with increasing E. crassipes abundance (Robinson 2007).

 Eichhornia crassipes may displace or shade out native macrophytes, thus altering macrophyte communities.

Environmental Impact Total 15

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6 √

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U

 Its vigorous growth and invasive characteristics have created nuisance problems for water quality, mosquito 

control, and water-borne transportation (Owens and Madsen1995).

 Floating mats of Eichhornia crassipes support organisms that are detrimental to human health. The ability of its 

mass of fibrous, free-floating roots and semi-submerged leaves and stems to decrease water currents increases 

breeding habitat for the malaria causing anopheles mosquito as evidenced in Lake Victoria (UNEP GEAS 

2013). 

 Mansonioides mosquitoes, the vectors of human lymphatic filariasis causing nematode Brugia, breed on this 

weed (UNEP GEAS 2013).

 Snails serving as vector for the parasite of schistosomiasis (Bilharzia) reside in the tangled weed mat (UNEP 

GEAS 2013).

 Eichhornia crassipes has also been implicated in harboring the causative agent for cholera (UNEP GEAS 

2013).
1399

 At the local level, increased incidences of crocodile attacks have been attributed to the heavy infestation of the

weed, which provides cover to these reptiles, as well as to poisonous snakes (UNEP GEAS 2013).

 Eichhornia crassipes can pose a risk to human health by providing a habitat for mosquitos, and may increase 

the risk of mosquito-borne diseases (Jianqing et al. 2001, Mailu 2001).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1 √

Not significantly 0

Unknown U

 The large, dense monoculture formed by this species covers lakes and rivers, blocking waterways and 

interfering with the water transport of agriculture products, tourism activities, water power, and irrigation of 

agricultural fields (Shanab et al. 2010).

 The overall economic impacts of the weed in seven African countries have been estimated at between US$20-50 

million every year. Across Africa costs may be as much as $100 million annually (UNEP GEAS 2013).

 The infestation of E. crassipes resulted in increased transportation costs, blockage of irrigation canals, and 

difficulties in electricity and water extraction (Mailu 2001).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1 √

Not significantly 0 

Unknown U

 Its vigorous growth and invasive characteristics have created nuisance problems for water quality, mosquito 

control, and water-borne transportation (Owens and Madsen 1995).

 The overall economic impacts of the weed in seven African countries have been estimated at between US$20-50 

million every year. Across Africa costs may be as much as $100 million annually (UNEP GEAS 2013).

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U

 The large, dense monoculture formed by this species covers lakes and rivers, blocking waterways and 

interfering with the water transport of agriculture products, water power, and irrigation of agricultural fields 

(Shanab et al. 2010).

 The overall economic impacts of the weed in seven African countries have been estimated at between US$20-50 

million every year. Across Africa costs may be as much as $100 million annually (UNEP GEAS 2013).

 In Benin, the infestation of E. crassipes was estimated to reduce the annual income of the villagers by US$84 

million, who relied on fishing and trade for an income (De Groote et al. 2003). Biological control for the 

infested waters in Benin were estimated to be United States $2.09 million.
1400

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U

 The large, dense monoculture formed by this species covers lakes and rivers, blocking waterways, and 

interfering with tourism activities (Shanab et al. 2010).

 The overall economic impacts of the weed in seven African countries have been estimated at between US$20-50 

million every year. Across Africa costs may be as much as $100 million annually (UNEP GEAS 2013).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6 √

Yes, but negative consequences have been small 1 

Not significantly 0 

Unknown U

 The large, dense monoculture formed by this species covers lakes and rivers (Shanab et al. 2010).

 Eichhornia crassipes can displace native species, reduce biodiversity, limit recreation, diminish aesthetic value, 

and decrease water quality and flow (Robinson 2007).

Socio-Economic Impact Total 26

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1401

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

 There was no literature declaring E. crassipes was used as a biological control agent for other organisms at 

the time of this assessment.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 This species can be bought from many online retailers (e.g., pondplantsforsale.com).

 Retail advertisements also recommend this species as a good oxygenator plants for outdoor ponds (e.g., 

pondplantsforsale.com).

 It is speculated that the biomass can be used in wastewater as substrate for bioethanol and biogas production, 

electricity generation, industrial uses, animal feed, or agriculture (Jafari 2010, UNEP GEAS 2013).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This species can be used as an attractive pond plant or aquarium decoration.

 Retail advertisements also recommend this species as a good oxygenator plants for outdoor ponds (e.g., 

pondplantsforsale.com).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6
1402

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 It is speculated that the biomass can be used in medicines (UNEP GEAS 2013).

 Water Hyacinth has been found to produce an alkaloid that can affect certain bacteria, fungi, and green algae 

strains; plant compounds exhibited antibacterial activities against both the Gram positive bacteria; Bacillus 

subtilis and Streptococcus faecalis; and the Gram negative bacteria; Escherichia coli and Staphylococcus 

aureus (Shanab et al. 2010).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 

 It is speculated that the biomass can be used in wastewater treatment or heavy metal and dye remediation 

(Pinto et al. 1987, UNEP GEAS 2013).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1

Not significantly 0 √

Unknown U 

Beneficial Effect Total 4

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1403

Scientific Name: Hydrilla verticillata

Royle

Common Name: Hydrilla

Synonyms: Water Thyme

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High

Hitchhiking/fouling: High

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: Unknown

Escape from commercial culture: Unknown

Transoceanic shipping: Unlikely

Hydrilla verticillata has a high probability of introduction to the Great Lakes (Confidence level: 

Moderate). 

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentional 

Release, Escape from Recreational and Commercial Culture

This species occurs near the Great Lakes basin. It occurs in Lake Manitou, Indiana (D. Keller, Indiana 

DNR, pers. comm. 2006), has been reported in private ponds in 2007 in Marinette County, Wisconsin 

(WIDNR 2009), and has been reported in Tonawanda Creek of the New York State Erie Canal System in 

2012 (NY DEC 2012). Hydrilla verticillata was first introduced to the United States as an aquarium plant 

in the 1960s and since has spread through recreational activities (Langeland 1996). Hydrilla verticillata

spreads through vegetative fragmentation (GISD 2006a). Hydrilla verticillata can potentially enter the 

Great Lakes region through fragmentation and subsequent dispersal from its current range. Hydrilla 

verticillata can be dispersed by plant fragments attached to boats or trailers, or tubers that are consumed 

and excreted by waterfowl (GISD 2006a). 

This species is prohibited in the Great Lakes including Chicago, Illinois, Indiana, Michigan, and 

Wisconsin. It is not prohibited in New York, Ohio, Ontario, Pennsylvania, or Quebec (GLPANS 2012). 

Hydrilla verticillata is listed on the Federal Noxious Weed List.

This species can be purchased and introduced to the Great Lakes via unauthorized intentional release. 

Although, H. verticillata is listed on the United States Federal Noxious Weed, it is still sold over the 

internet as an aquarium plant and can be obtained from Ontario’s aquarium trade (Marson et al. 2009). 

Moreover, this species has been found as a contaminant in aquarium orders of other plant species (Maki 

and Galatowitsch 2004).
1404

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, 

including connecting channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 This species primarily reproduces vegetatively; as such, small fragments that float downstream can grow into a 

new plant (PA Sea Grant 2013).

 Hydrilla verticillata can spread to new locations through floating debris or on water currents (GISD 2006a). It 

therefore has the potential to enter the Great Lakes region through fragmentation and dispersal from rivers 

leading to the basin.

 Hydrilla was found in Indiana's Lake Manitou in 2006, prompting closure to public boating access and 

chemical treatment (D. Keller, Indiana DNR, pers. comm. 2006). As of June of 2008, treatment has significantly 

reduced hydrilla growth and tuber production, prompting a limited re-opening of one boat ramp (INDNR 

2009).

 This species was also found in a privately-owned artificial pond in Marinette County, Wisconsin in 2005 

(confirmed in 2007; WIDNR 2009).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Hydrilla verticillata is absent in Michigan but has isolated populations in Indiana, Wisconsin, and Ohio (MI 

DEQ 2013).

 The Lake Manitou population in Rochester, IN was found in 2006 and 2008 (USGS NAS 2015). After the first 

year’s treatment, the tuber bank decreased by 86%, and in 2008, the DNR boat ramp access was reopened to 

the public (http://www.eddmaps.org/distribution/point.cfm?id=2479555).

 Hydrilla was detected at the base of a boat ramp on Tonawanda Creek, part of the New York State/Erie Canal 

System in Tonawanda, NY in September 2012 (http://www.dec.ny.gov/press/85078.html , http://ne-ecologicalservices.blogspot.com/2012/10/hydrilla-closes-in-on-great-lakes.html). This confirms hydrilla as being within 

one mile of the Niagara River (and thus the Great Lakes).

 Hydrilla was detected in an artificial pond in Marinette County, WI in 2005 and 2007 (USGS NAS 2015). The 

aquatic herbicide, Aquathol ® K, was applied in August 2007, followed by a fall water drawdown 

(http://www.eddmaps.org/distribution/point.cfm?id=2480259).

 An Ohio population was found in shallow man-made wetlands, West Creek Reservation, Parma, Cuyahoga 

County in 2011 (http://www.eddmaps.org/distribution/point.cfm?id=2277127)
1405

 Furthermore, monoecious hydrilla occurs in thin patches along much of the Ohio region of the Ohio River to 

depths of four feet and has been proposed to be a significant source population to the surrounding area 

(Hydrilla Workshop 2012).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Hydrilla verticillata can be dispersed by plant fragments attached to boats or trailers, or tubers that are 

consumed and excreted by waterfowl (GISD 2006a).

 It is tolerant of periods of desiccation, with twigs and tubers surviving 16 hours to several days out of water, 

respectively (Basiouny et al. 1978, Kar and Choudhuri 1982).

 Imported to the United States as an aquarium plant, it has since been spread through recreational activities (PA 

Sea Grant 2013). It has the potential to enter the Great Lakes region through fragmentation and dispersal from 

rivers leading to the basin, or by unintentional human introductions.

 Hydrilla is mainly introduced to new waters as castaway fragments on recreational boats, their motors and 

trailers, and in live wells. Stem pieces root in the substrate and develop into new colonies, commonly beginning 

near boat ramps. Once established, boat traffic continues to fragment and spread hydrilla throughout the 

waterbody. While it propagatse primarily by stem fragmentation, axillary buds (turions) and subterranean 

tubers are also important. Its tubers are resistant to most control techniques (Schardt 1994) and may be viable 

as a source of reinfestation for years (Van and Steward 1990).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1 √

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 Hydrilla was detected at the base of a boat ramp on Tonawanda Creek, part of the New York State/Erie Canal 

System in Tonawanda, NY in September 2012 (http://www.dec.ny.gov/press/85078.html , http://ne-ecologicalservices.blogspot.com/2012/10/hydrilla-closes-in-on-great-lakes.html). This confirms hydrilla as being within 

one mile of the Niagara River (and thus the Great Lakes). Previously, hydrilla was found in the Cayuga Inlet in 

New York (http://www.seagrant.sunysb.edu/articles/t/nysg-partners-for-treatment-of-invasive-hydrilla-plant-incayuga-inlet-aquatic-invasive-species-news), where it was subsequently treated.

 Monoecious hydrilla occurs in thin patches along much of the Ohio region of the Ohio River to depths of four 

feet and has been proposed to be a significant source population to the surrounding area through bass 

tournament fishing (Hydrilla Workshop 2012).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE
1406

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Although Hydrilla verticillata is on the United States Federal Noxious Weed List, it is still sold over the internet 

as an aquarium plant, leading to a potential means of introduction (GISD 2006a).

 Hydrilla verticillata can spread to new locations as an unknown contaminant among other water garden plants 

(e.g., found in water lily shipments) and through the pet/aquarium trade (GISD 2006a).

 Hydrilla has the potential to enter the Great Lakes region by unintentional human introductions. It has been 

received as a contaminant in orders of other aquarium plants in Minnesota (Maki and Galatowitsch 2004).

 Hydrilla is present in Ontario’s aquarium trade (Marson et al. 2009).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 Hydrilla verticillata is on the United States Federal Noxious Weed List, which makes it illegal in the United 

States to import or transport between states without a permit, but it is still sold as an aquarium plant over the 

internet (GISD 2006a).

 This species is prohibited in Michigan, meaning it cannot be sold or grown without a permit 

(http://www.legislature.mi.gov/(S(4y3p5eyuypll2z55banpqd55))/mileg.aspx?page=getObject&objectName=mcl

-324-41301).

 In Indiana, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute hydrilla 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF).

 It is also prohibited in Minnesota (https://www.revisor.mn.gov/rules/?id=6216.0250) and Wisconsin 

(http://docs.legis.wisconsin.gov/code/admin_code/nr/001/40.pdf).

 An internet search at the time of assessment revealed that “hydrilla” does not appear to be sold by Carolina 

Biological Supply, online pet stores, or online aquarium stores (at least under that name).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 
1407

Unknown U √

 Hydrilla may be unknowingly transplanted into private ponds as a contaminant on water garden plants (e.g., 

water lily shipments). It is often found spreading after extensive 2,4-D herbicide use in public waters once 

heavily populated with Eurasian water-milfoil (Myriophyllum spicatum) (Bates and Smith 1994).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U √

 Hydrilla verticillata is on the United States Federal Noxious Weed List, which makes it illegal in the United 

States to import or transport between states without a permit, but it is still sold as an aquarium plant over the 

internet (GISD 2006a).

 This species is prohibited in Michigan, meaning it cannot be sold or grown without a permit 

(http://www.legislature.mi.gov/(S(4y3p5eyuypll2z55banpqd55))/mileg.aspx?page=getObject&objectName=mcl

-324-41301).

 In Indiana and Illinois, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute hydrilla 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF, http://www.dnr.illinois.gov/adrules/documents/17-

805.pdf).

 It is also prohibited in Minnesota (https://www.revisor.mn.gov/rules/?id=6216.0250) and Wisconsin 

(http://docs.legis.wisconsin.gov/code/admin_code/nr/001/40.pdf).

 An internet search at the time of assessment revealed that “hydrilla” does not appear to be sold by Carolina 

Biological Supply, online pet stores, or online aquarium stores (at least under that name).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U √

 Commercial culture or transport of hydrilla in the Great Lakes region is prohibited in Michigan, Illinois, 

Indiana, Minnesota, and Wisconsin but may be occurring in other states of provinces.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes Score x 0.75
1408

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U √

 Hydrilla verticillata is on the United States Federal Noxious Weed List, which makes it illegal in the United 

States to import or transport between states without a permit, but it is still sold as an aquarium plant over the 

internet (GISD 2006a).

 This species is prohibited in Michigan, meaning it cannot be sold or grown without a permit 

(http://www.legislature.mi.gov/(S(4y3p5eyuypll2z55banpqd55))/mileg.aspx?page=getObject&objectName=mcl

-324-41301).

 In Indiana and Illinois, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute hydrilla 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF, http://www.dnr.illinois.gov/adrules/documents/17-

805.pdf).

 It is also prohibited in Minnesota (https://www.revisor.mn.gov/rules/?id=6216.0250) and Wisconsin 

(http://docs.legis.wisconsin.gov/code/admin_code/nr/001/40.pdf).

 An internet search at the time of assessment revealed that “hydrilla” does not appear to be sold by Carolina

Biological Supply, online pet stores, or online aquarium stores (at least under that name).

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great Score x 0.1
1409

Lakes nor in ports in direct trade with the Great Lakes.

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.1 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

U x U U Unknown

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

U x U U Unknown

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
1410

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Hydrilla verticillata has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Hydrilla verticillata has physiological tolerances and adaptive attributes that make it the “perfect aquatic 

weed” (Langeland 1996). Hydrilla verticillata can survive fresh and brackish waters (0-7 ppt salinity) 

(Langeland 1996). This species can grow in ogliotrophic to eutrophic conditions and in low-light levels 

(Ramey 2001). It is likely that the Great Lakes has appropriate light and nutrient levels for H. verticillata. 

It is possible that Hydrilla verticillata can overwinter in the Great Lakes. It is somewhat winter-hardy 

(Ramey 2001), and produces turions, which are overwintering vegetative propagules (Maki and 

Galatowitsch 2004). This species occurs on every continent except Antarctica. It occurs in inland waters 

near the Great Lakes region such the Erie Canal in New York (NY DEC 2012), which has similar climatic 

and abiotic conditions as the Great Lakes region. This species inhabits fresh waters at depths up to 15 m 

(Langeland 1996); such habitats are available in the Great Lakes. The predicted effects of climate change 

in the Great Lakes may benefit H. verticillata. Increased carbon dioxide levels and elevated water 

temperatures may increase the growth rate of H. verticillata (Chen et al. 1994). Climate change may 

enhance its northward spread (Cooke et al. 2005). 

Hydrilla verticillata has a high rate of productivity. It can produce an average of 6,046 tubers per season 

(Sutton et al. 1992). Experiments show that H. verticillata can produce up to 46 axillary tubers per g dry 

weight (Thullen 1990). Small amounts of Hydrilla verticillata can be moved and develop into new 

populations. About 50% of the fragments with a single whorl can sprout to form a new plant, while those 

with a greater number of whorls have a higher chance of sprouting (Langeland and Sutton 1980). Its 

ability for vegetative fragmentation may aid its establishment in new environments. It spreads especially 

quickly in fast flowing waters, as it efficiently disperses fragments (Ramey 2001). 

This species may negatively impact other species. It has high allelopathy potential and has inhibited the 

growth of lettuce seedlings and duckweed in experiments (Elakovich and Wooten 1989). This species 

forms dense mats on the surface water, limiting light penetration and light availability for other aquatic 

plant species (Carlson et al. 2008). Hydrilla verticillata is known to be highly adaptive and competitive 

for light and nutrients (Langeland 1996). It can compete with native plants such as pondweeds 

(Potamogeton sp.) and eelgrass (Vallisneria americana).

Surveillance and management efforts are currently underway to detect, control, and/or eradicate this 

species in Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). However, a basin-wide program 

is lacking (Dupre 2011). Control of Hydrilla verticillata has been attempted with the introduction of 

Grass Carp, herbicide application, and biocontrol using weevils Bagous affinis and B. hydrillae (Cooke et 

al. 2005). Two biocontrol agents, Bagous affinis and B. hydrillae, were released in Florida in 1987 and 

1991, respectively, but both species were unsuccessful in controlling Hydrilla infestation. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?
1411

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 Hydrilla verticillata can grow in almost any freshwater including marshes, springs, lakes, ditches, rivers and 

tidal zones, and can also tolerate up to 7% salinity.

 It can grow in oligotrophic to eutrophic conditions.

 It is somewhat winter-hardy, with an optimum growth temperature of 20-27°C (68-81°F) and a maximum 

temperature of 30°C (86°F) (Kasselmann 1995). In the south it is a perennial, in the north a re-sprouting 

annual.

 It grows at down to 1% full sunlight, and has a low light compensation and saturation point, which can help it 

grow in low light before other plants do (Van et al. 1976, Bowes et al. 1977).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

6

 It is somewhat winter-hardy, with an optimum growth temperature of 20-27°C (68-81°F) and a maximum 

temperature of 30°C (86°F) (Kasselmann 1995). In the south it is a perennial, in the north a re-sprouting 

annual.

 Hydrilla verticillata produced turions (overwintering vegetative propagule) (Maki and Galatowitsch 2004).

 Draining is not sufficient control unless frozen several inches into the mud to kill the turions (tubers).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U
1412

0

 This speceis is an autotroph

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

9

 In experiments by Elakovich and Wooten (1989) extracts of hydrilla exhibit high allelopathy potential and 

inhibited the growth of lettuce seedling and duckweed.

 Hydrilla forms a dense mat of vegetation at the water surface and limits light penetration degrading or 

eliminating all layers below (Bossard et al. 2000).

 Hydrilla is highly adaptive to the environment and competitive with most other aquatic plants (Haller and 

Sutton 1975). It is able to outcompete native submerged plants for light and nutrients. The growth habit of 

hydrilla enables it to compete effectively for sunlight. It can elongate up to 1 inch per day, and produces the 

majority of the stems in the upper 2–3 feet of water (Haller and Sutton 1975). This mat of vegetation intercepts 

sunlight and leads to exclusion of other aquatic plants. Hydrilla is also adapted to use low light levels for 

photosynthesis (Barko and Smart 1981, Van et al. 1976). Hydrilla efficiently uses a limited supply of nutrients 

such as carbon, nitrogen, and phosphorus.

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 One plant can produce an average of 6,046 tubers per season (Sutton et al. 1992). An experiment by Thullen 

(1990) showed that hydrilla can produced up to 46 axillary turions per 1.0 g dry weight (estimated of 2803 

turions per m3). About 50% of the fragments with a single whorl can sprout and form new plant, and more than 

50% of the fragments with three whorls can sprout (Langeland and Sutton 1980).
1413

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

8

 Hydrilla verticillata reproduces asexually—mostly by vegetative fragmentation, but also from tubers—and 

sexually (when plants are either monoecious or dioecious with both plants present). It spreads especially fast in 

flowing water, since it efficiently disperses fragments (GISD 2006a, Ramey 2001).

 It also can reproduce through fragmentation, turions (buds that form in leaf axils), and subterranean turions 

(commonly called “tubers” (IISG n.d.).

 Only female plants exist in the United States, while only male plants exist in New Zealand (GISD 2006a).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

8

 This species is native to Asia, Northern Australia; it is a dioecious plant native to India, monoecious in South 

Korea

 This species is found on every continent except Antarctica. It grows up to 50° North latitude in Russia. 

 It was introduced in Florida in the 1950s, and fully established in the 1970s.

 The known United States range for this species is: Alabama, Arizona, California, Connecticut, District of 

Columbia, Delaware, Florida, Georgia, Indiana, Louisiana, Maryland, Maine, Mississippi, New York, North 

Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, Washington, Wisconsin.
1414

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

8

 This species ccurs in slow-moving water of lakes, ponds, streams and rivers; tolerates a wide range of water 

quality (MI DEQ 2012).

 Hydrilla tolerates a wide range of nutrient and pH levels, and persists in low sunlight (IISG n.d.).

 Hydrilla verticillata can grow in almost any freshwater including marshes, springs, lakes, ditches, rivers and 

tidal zones, and can also tolerate up to 7% salinity.

 It can grow in oligotrophic to eutrophic conditions.

 It is somewhat winter-hardy, with an optimum growth temperature of 20-27°C (68-81°F) and a maximum 

temperature of 30°C (86°F) (Kasselmann 1995). In the south it is a perennial, in the north a re-sprouting 

annual.

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

8

 It grows at down to 1% full sunlight, and has a low light compensation and saturation point, which can help it 

grow in low light before other plants do (Van et al. 1976, Bowes et al. 1977).

 This species grows at depths of up to 6 m (20 ft) (MI DEQ 2012).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6
1415

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

9

 Chen et al. (1994) found that increased carbon dioxide may cause the invasive aquatic plant dioecious hydrilla 

(Hydrilla verticillata) to increase its growth rate at elevated temperatures (e.g., maximum effects of temperature 

on growth were recorded at 25°C). Thus, as temperatures and carbon dioxide levels rise, hydrilla has the 

potential to spread more rapidly within and outside of its current range (USEPA 2008).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is modersate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Hydrilla is highly adaptive to the environment and competitive with most other aquatic plants (Haller and 

Sutton 1975). It is able to outcompete native submerged plants for light and nutrients. The growth habit of 

hydrilla enables it to compete effectively for sunlight. It can elongate up to 1 inch per day, and produces the 

majority of the stems in the upper 2–3 feet of water (Haller and Sutton 1975). This mat of vegetation intercepts 

sunlight and leads to exclusion of other aquatic plants. Hydrilla is also adapted to use low light levels for 

photosynthesis (Barko and Smart 1981, Van et al. 1976). Hydrilla efficiently uses a limited supply of nutrients 

such as carbon, nitrogen, and phosphorus.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

3
1416

the species being assessed

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 There are no critical speciesfor Hydrilla.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 There is no facilitation needed by this species.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)
1417

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

3

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0
1418

Unknown U

9

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-30%

 Surveillance and management efforts are currently underway to detect, control and/or eradicate this plant in 

Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). However, a basin-wide monitoring program is 

lacking (Dupre 2011).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 107

>100 High Adjustments

B. Critical species A*(1- 0%) 107

51-99 Moderate C. Natural enemy B*(1- 0%) 107

Control measures C*(1- 30%) 74.9

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low
1419

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Hydrilla verticillata has the potential for high environmental impact if introduced to the Great 

Lakes.

Hydrilla verticillata can potentially be detrimental to native species and the ecosystem. This species 

grows aggressively and competitively as dense mats that can displace or shade out native submersed 

plants. In the southeast United States, H. verticillata effectively displaces beneficial native vegetation, 

such ponweeds (Potamogeton sp.) (Langeland 1996), eelgrass (Vallisneria americana), and coontail 

(Ceratophyllum demersum) (Rizzo et al. 1996, Van Dijk 1985). The frequency of occurrence of southern 

naiad in Florida was reduced from 56% to 4% after the establishment of H. verticillata (Estes et al. 1990). 

Infestations may reduce seed production of native aquatic plants, which may reduce the number of native 

species in the community (De Winton and Clayton 1996). Infestations of this species may shift 

phytoplankton compositions and alter chlorophyll content (Schmitz et al. 1993). Experimental evidence 

suggests that H. verticillata has high allelopathy potential and can inhibit the growth of lettuce seedling 

and duckweed (Elakovich and Wooten 1989).

Infestations of H. verticillata may alter water chemistry, decrease oxygen levels, increase pH, and 

increase water temperature (Woodward and Quinn 2011). Non-normal stratification of the water column 

(Rizzo et al. 1996, Schmitz et al. 1993), decreased oxygen levels (Pesacreta 1988), and fish kills (Rizzo et 

al. 1996) have been documented in H. verticillata infestations. 

Sportfish exhibited lower weight and size when H. verticillata occupied the majority of the water column, 

which suggests that foraging efficiency was reduced as open water space and natural vegetation gradients 

were lost (Colle and Shireman 1980).

Hydrilla verticilla has the potential for high socio-economic impact if introduced to the Great Lakes. 

Hydrilla verticillata is among the worst aquatic plants in the southeastern United States, causing costly 

damage to irrigation and hydroelectric power projects, and recreation (Cooke et al. 2005). This species 

causes major impacts on infrastructure. Hydrilla verticillata can reduce the flow in drainage canals, which 

can result in flooding and damage to canal banks and structures (Langeland 1996). This species can clog 

intake pumps used for irrigation. In 1994-1995, Florida spent $14.5 million controlling Hydrilla 

(Woodward and Quinn 2011). During September 1989 in South Carolina, heavy rainfall and consequent 

flood discharge caused large mats of H. verticillata to break loose and clog intake screens, shutting down 

two hydroelectric turbines at Guntersville Dam (North Carolina Agricultural Extension Service 1992). 

This species is a nuisance for navigation of recreational and commercial waters and interferes with 

swimming (Langeland 1996). The economic value of Orange Lake, Florida ($11 million) was lost during 

the infestation of Hydrilla verticillata (Milon et al. 1986). The dense mats of H. verticillata create 

stagnant waters that can be used as mosquito breeding habitat (Hartis 2013), making this species a risk for 

human health.
1420

Hydrilla verticilla has the potential for moderate beneficial impact if introduced to the Great Lakes.

Hydrilla verticillata may increase water clarity by reducing sediment re-suspension and reducing 

phytoplankton populations (Langeland 1996). It is valuable for water gardens and aquariums. Hydrilla 

verticillata may benefit some species as a food source, but only when its coverage is below 30% (Cole 

and Shireman 1980, Estes et al. 1990).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 In experiments by Elakovich and Wooten (1989) extracts of hydrilla exhibit high allelopathy potential and 

inhibited the growth of lettuce seedling and duckweed (Carlson et al. 2008).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 Hydrilla verticillata is not easy to detect until it fills the lake it infests and tops out at the surface; it grows in 

thick mats, and shades out or outcompetes ecologically important native submersed plants including 

Potamogeton pondweeds, tapegrass (Vallisneria americana), and coontail (Ceratophyllum demersum) (Van 

Dijk 1985).

 Hydrilla grows aggressively and competitively, spreading through shallower areas and forming thick mats in 

surface waters that block sunlight penetration to native plants below (van Dijk 1985).

 In the southeast, hydrilla effectively displaces beneficial native vegetation (Bates and Smith 1994) such as wildcelery (Vallisneria americana) and coontail (Ceratophyllum demersum) (Rizzo et al. 1996, van Dijk 1985)

 Colle and Shireman (1980) found sportfish reduced in weight and size when hydrilla occupied the majority of 

the water column, suggesting that foraging efficiency was reduced as open water space and natural vegetation 

gradients were lost.

 Hydrilla infestations can cause a reduction or the extirpation of populations of native aquatic species (Bossard 

et al. 2000). Hydrilla may also shift the phytoplankton composition (Canfield et al. 1984). Infestations also 
1421

adversely affect fish populations. Hydrilla may reduce seed production of native species, resulting eventually in 

a reducing of a number of native species in the community (de Winton and Clayton 1996). A study in Florida 

found that the frequency of occurrence for the most abundant native submersed plants, coontail and southern 

naiad decreased from 11% to 4% and 56% to 4%, respectively, from 1987 to 1990 (Ester et al. 1990).

 Hydrilla forms a dense mat of vegetation at the water surface and limits light penetration degrading or 

eliminating all layers below (Bossard et al. 2000).

 Hydrilla is highly adaptive to the environment and competitive with most other aquatic plants (Haller and 

Sutton 1975). It is able to outcompete native submerged plants for light and nutrients. The growth habit of 

hydrilla enables it to compete effectively for sunlight. It can elongate up to 1 inch per day, and produces the 

majority of the stems in the upper 2–3 feet of water (Haller and Sutton 1975). This mat of vegetation intercepts 

sunlight and leads to exclusion of other aquatic plants. Hydrilla is also adapted to use low light levels for 

photosynthesis (Barko and Smart 1981, Van et al. 1976). Hydrilla efficiently uses a limited supply of nutrients 

such as carbon, nitrogen, and phosphorus.

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 

Unknown U √

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 
1422

Not significantly 0 

Unknown U

 Dense infestations of this species can alter water chemistry, decrease oxygen levels (Pesacreta 1988, GISD 

2006a) and increase pH and water temperature (GISD 2006a).

 It has been shown to alter the physical and chemical characteristics of lakes. Stratification of the water column 

(Schmitz et al. 1993, Rizzo et al. 1996), decreased oxygen levels (Pesacreta 1988), and fish kills (Rizzo et al. 

1996) have been documented. Changes in water chemistry may also be implicated in zooplankton and 

phytoplankton declines (Schmitz and Osborne 1984, Schmitz et al. 1993).

 Slow waterflow can also increase the sedimentation rates, water temperature, and pH level (Estes et al. 1990, 

Joyce et al. 1992) and decrease dissolved oxygen (Bossard et al. 2000). It also affects water nutrient turnover 

(Bole and Allan 1978, Sinha et al. 2000).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U

 Hydrilla seriously affects water flow and water use. Infestations in the Mobile Delta are reducing flow in small 

tidal streams and creating a backwater habitat (J. Zolcynski pers. comm. 1998 in Carlson et al. 2008).

 Hydrilla infestations slow the movement of water, causing flooding (Carlson et al. 2008).

 Hydrilla forms a dense mat of vegetation at the water surface and limits light penetration degrading or 

eliminating all layers below (Bossard et al. 2000).

 Hydrilla causes severe alterations of plant community composition, community structure, and ecosystem 

processes in water bodies in California (Bossard et al. 2000). This aquatic weed displaces native plants and 

adversely impacts freshwater habitats in Florida (Langeland 1996).

Environmental Impact Total 19

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2 Unknown
1423

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6 √

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0

Unknown U

 Some amounts of hydrilla can lead to problems with swimming and wading and have even been linked to 

drowning deaths in a few cases. As mentioned in previous discussions, hydrilla also creates the perfect stagnant 

habitat for mosquito breeding. Those itchy bites aren't the worst that can come of this problem, as mosquitoes 

often carry diseases which can harm us, our pets and our livestock Hartis 2013).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 Hydrilla verticillata slows water flow and clogs irrigation and flood control canals. Florida alone spends 

millions of dollars for hydrilla “maintenance control” with herbicides and mechanical harvesters; mats of it 

wash up on shore there, collect at culverts and clog important water control pumping stations (Ramey 2001).

 In the TVA system in September 1989, heavy late-season rainfall and consequent flood discharges caused large 

mats of hydrilla to break loose. These mats clogged intake screens and forced the shutdown of two hydroelectric 

turbines at Guntersville Dam. Hydrilla mats floated over the spillway and blocked water intakes downstream at 

Wheeler Dam. The result was $170,000 in lost power plant revenues. Similarly, in June 1991 the St. Stephens 

hydroelectric plant on Lake Marion in South Carolina was shut down because of a hydrilla accumulation on the 

water intake screens (http://www.weedscience.ncsu.edu/aquaticweeds/hydrilla.PDF).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U


1424

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1

Not significantly 0 

Unknown U

 Florida spends roughly $20 million annually to control just one species, Hydrilla verticillata (Gordon et al. 

2012).

 Worldwide economic impacts of Hydrilla verticillata include impacts relating to infestation of rice fields, 

irrigation canals, fishponds and public waterways (Cook and Lüönd 1982) 

(http://www.sms.si.edu/irlspec/Hydrilla_verticillata.htm).

 Hydrilla interferes with a wide variety of commercial operations. Thick mats hinder irrigation operations by 

reducing flow rates by as much as 90% (CDFA 2000) and impede the operation of irrigation structures 

(Godfrey et al. 1996). Hydroelectric power generation also is hindered by fragmented plant material that builds 

up on trash racks and clogs intakes. During 1991, hydrilla at Lake Moultrie, South Carolina shut down the St. 

Stephen powerhouse operations for seven weeks resulting in $2,650,000 of expenses due to repairs, dredging, 

and fish loss. In addition, during this repair period, there was an estimated $2,000,000 loss in power generation

for the plant (Balciunas et al. 2002).

 Boat marinas have been reported closed for extended periods on the Potomac River, Virginia; Lake 

Okeechobee, Florida; Santee Cooper Reservoirs, South Carolina; and Clear Lake, California 

(http://dnr.state.il.us/stewardship/cd/biocontrol/7Hydrilla.html).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U

 Hydrilla seriously affects water flow and water use. Its heavy growth commonly obstructs boating, swimming 

and fishing in lakes and rivers and blocks the withdrawal of water used for power generation and agricultural 

irrigation. 

 Hydrilla seriously impedes recreational and commercial boating and prevents swimming and fishing, and 

major infestations limit weight and size of sport fishes (Colle and Shireman 1980).

 Large hydrilla mats prevent access to many of the prime locations used for waterfowl hunting and most warmwater sport fishing. Low oxygen levels in these mats make them unsuitable for the growth and survival of sport 

fishes and most other aquatic animals. Heavy hydrilla infestations (those that cover more than 25 to 30 percent 

of the surface in large lakes and impoundments) eliminate fish habitat, cause stunting, and reduce the number 

of harvestable fish. Thus, hydrilla usually is detrimental to sport fishing over the long term (North Carolina 

Agricultural Extension Service 1992).

 In the late 1980s, hydrilla populations at Lake Guntersville, Alabama increased rapidly. Henderson (1995) 

examined the economic impact of aquatic plant control programs on recreational use of this lake between 1990 

and 1994. He found that the greatest economic value for recreation ($122 million annually) occurred when 

vegetation levels were 20% of the total lake area, and that revenue declined as hydrilla acreage increased. 

(Balciunas et al. 2002).
1425

 For instance, Florida spends about $14.5 million each year on hydrilla control (Center et al. 1997). Despite 

this large expenditure, hydrilla infestations in just 2 Florida lakes have prevented their recreational use, 

causing $10 million annually in losses (Center et al. 1997) (Pimental et al. 2005)

 South Carolina's aquatic weed control expenditures grew from less than $50,000 in 1981 to $800,000 in 1989. 

The Tennessee Valley Authority (TVA) currently spends about $300,000 annually to control hydrilla and has 

spent more than $1 million since it was discovered in Guntersville Reservoir in 1982. Public agencies in 

California have spent a total of more than $15 million on hydrilla control since 1976. In Texas, more than $2 

million has been expended since 1984 by state and federal agencies for hydrilla control (North Carolina 

Agricultural Extension Service 1992).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6 √

Yes, but negative consequences have been small 1 

Not significantly 0 

Unknown U

 The stagnant water left after the slowing and clogging of rivers, ditches and canals provides prime breeding 

habitat for mosquitoes (GISD 2006a).

 Reducing value of shorefront property (http://www.seagrant.sunysb.edu/ais/pdfs/Hydrilla-brochure030912.pdf).

Socio-Economic Impact Total 30

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?
1426

Yes, it has succeeded significantly as a control agent 6

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0

Unknown U

 It is commercially sold for aquaria and water gardens, but limited due to prohibitions in some states.

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 It is recreationally used for aquaria and water gardens, but limited due to prohibitions in some states.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 Sold as a health product (http://www.swansonvitamins.com/swanson-greenfoods-formulas-wild-craftedhydrilla-verticillata-500-mg-120-

caps?SourceCode=INTL405&CAWELAID=129499578&catargetid=530002460000000567&cagpspn=pla&gc

lid=CICup7Gew7cCFcU7Mgodtz4ALg)

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6
1427

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 

 Hydrilla was listed as potentially valuable for use in rhizofiltration (absorbing, concentrating or precipitating 

compounds from aqueous solutions) (presentation for Bob Grese’s Fall 2010 Ecological Restoration class on 

Phytoremediation)

 Highly transparent water is often considered desirable by the public and large populations of submersed 

aquatic macrophytes, such as hydrilla, will tend to increase water clarity (Canfield et al. 1984). The exact 

reasons for this increase in water clarity are not completely understood but it probably results from a 

combination of factors which include lowering sediment re-suspension and reduction of phytoplankton 

populations by compartmentalizing nutrients. Regardless, large amounts of aquatic macrophytes are necessary 

to cause substantial increases in water clarity (Canfield et al. 1984, Canfield and Hoyer 1992).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 √

Not significantly 0

Unknown U 

 Hydrilla provides food supplies for waterfowl in areas with degraded wetlands, such as Florida. Areas with up 

to 30% cover benefits most fisheries, because it can help grow prey fish populations for game fish to eat (GISD 

2006a).

 Hydrilla is eaten by waterfowl and fish. Some studies support the view that hydrilla is beneficial as a fishfood 

and cover (Estes et al. 1990); other researches suggest that fish populations are adversely affected when 

hydrilla coverage exceeds 30% (Colle and Shireman 1980). Hydrilla appears to be an important habitat for a 

number of mosquito species (Hearnden and Kay 1997).

 Some sport fishermen consider hydrilla to benefit largemouth bass habitat (Tucker 1987). While the opinion 

that hydrilla is beneficial for sportfish production is supported by certain research (Estes et al. 1990, Porak et 

al. 1990), other research suggests that largemouth bass are adversely affected when hydrilla coverage exceeds 

30% (Colle and Shireman 1980).

 Hydrilla is eaten by waterfowl, and maintaining hydrilla populations is sometimes advocated by waterfowl 

scientists because it increases the feeding habitat for ducks (Johnson and Montalbano 1984, Esler 1989).

Beneficial Effect Total 5

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
1428

1 0

0 ≥2

Unknown

1 ≥1
1429

Scientific Name: Hygrophila polysperma

Robyxb. T. Anders.

Common Name: Indian Hydrographila

Synonyms: East Indian Hygrophila, Indian Swampweed, Miramar Weed, Hemidelphis polysperma 

(Roxb.) Nees, Justicia polysperma (Roxb.).

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: Unlikely

Hitchhiking/fouling: Low

Unauthorized intentional release: Moderate

Stocking/planting/escape from recreational culture: Unlikely

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Hygrophila polysperma has a moderate probability of introduction to the Great Lakes (Confidence 

level: High). 

Potential pathway(s) of introduction: Hitchhiking/Fouling, Unauthorized Intentional Release 

Hygrophila polysperma was first introduced into Florida via the aquarium industry in the 1950s (Cuda 

and Sutton 2000). It was cultivated in Ohio at the end of WWII by an aquarium dealer (Reams 1953), but 

there is no indication that this species is still cultivated there. This species was introduced to Richmond, 

Virginia in the 1950s, and established there for 15-20 years until a cold winter caused its population to 

decline (Nault and Mikulyuk 2009). Hygrophila polysperma was first collected in Texas in 1969 in the 

San Marcos River (Nault and Mikulyuk 2009). This species also occurs in South Carolina (SC DNR 

2010). Hygrophila polysperma does not currently occur near waters connected to the Great Lakes basin. 

Hygrophila polysperma is listed as a Federal Noxious Weed and is prohibited in Illinois and Minnesota 

(GLPANS 2012), but can be ordered on the internet (Kay and Hoyle 2001). Surveys conducted by Rixon 

et al. (2005) found that H. polysperma was available for purchase in 25% of the pet and aquarium stores 

surveyed near Lakes Erie and Ontario. Maki and Galatowitsch (2004) had evidence that H. polysperma is 

available for purchase from vendors across the United States with delivery service to Minnesota. In 

addition, it is sometimes sold under the incorrect name of Alternanthera sessilis. The availability of and 

accessibility to H. polysperma in the aquarium industry may increase its potential to be introduced to the 

Great Lakes; after purchase and usage for aquariums, owners may dispose of the plant into waters 

connected to the Great Lakes basin.
1430

Hygrophila polysperma spreads via vegetative fragmentation. Hygrophila polysperma has a high 

regrowth potential from stem fragments (Spencer and Bowes 1985). It can get entangled and be 

transported to the Great Lakes on boats and recreational gear. Hygrophila polysperma fragments can also 

be dispersed by water; however, because this species does not currently occur near waters connected to 

the Great Lakes basin, it is unlikely that fragments will be transported by water to the Great Lakes.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 √

Unknown U

 North American nonindigenous occurrences are limited to Texas, Florida, South Carolina, and Virginia 

(EDDmapS 2015, USEPA 2008, USGS NAS 2015).

 Hygrophila polysperma has brittle stems that fragment, float, and spread on water currents (GISD 2005b, GISD 

2005). Rooted nodes of even small fragments are able to grow into new plants (GISD 2005b).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Hygrophila polysperma spreads naturally by fragmentation (Les 2005) and can get entangled and transported 

on boats or trailers, or in live wells.
1431

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1 

√

Unknown U

 North American nonindigenous occurrences are limited to Texas, Florida, and North Carolina (EDDmapS

2015, USGS NAS 2015).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Sale or trade of H. polysperma is possible online (e.g., Greater Toronto Area aquarium message board).

 According to Rixon et al. (2005), 25% of 20 aquarium stores surveyed between 2002 and 2003 in the Lake Erie 

region in Michigan and Ontario carried H. polysperma in stock.

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5 

√

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Hygrophila polysperma is prohibited in Minnesota, making it illegal to possess, import, purchase, propagate, or 

transport without a permit (https://www.revisor.mn.gov/rules/?id=6216.0250 MN Administrative Rules 

6216.0230).

 In Indiana and Illinois, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute this plant 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF, http://www.dnr.illinois.gov/adrules/documents/17-

805.pdf).

 It is listed as a Federal Noxious Weed under the Plant Protection Act, which makes it illegal in the United 

States to import or transport between States without a permit.

 In a study by Maki and Galatowitsch (2004), H. polysperma was one of two federal noxious weeds purchased 

despite its federal status of being illegal to move across state lines.

 Moreover, Maki and Galatowitsch (2004) found that this plant may not be labeled with its scientific name or 

otherwise may be misidentified, as in a case where a vendor was selling Alternanthera sessilis as H. 

polysperma.
1432

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 √

Unknown U

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 Hygrophila polysperma is prohibited in Minnesota, making it illegal to possess, import, purchase, propagate, or 

transport without a permit (https://www.revisor.mn.gov/rules/?id=6216.0250).

 In Indiana and Illinois, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute this plant 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF, http://www.dnr.illinois.gov/adrules/documents/17-

805.pdf).

 It is listed as a Federal Noxious Weed under the Plant Protection Act, which makes it illegal in the United 

States to import or transport between States without a permit.

 Sale or trade of H. polysperma is possible online (e.g., Greater Toronto Area aquarium message board, 

February 2013 http://gtaaquaria.com/forum/showthread.php?t=42253).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great Score x 1
1433

Lakes.

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

 Hygrophila polysperma is prohibited in Minnesota, making it illegal to possess, import, purchase, propagate, or 

transport without a permit (https://www.revisor.mn.gov/rules/?id=6216.0250).

 In Indiana and Illinois, it is illegal to possess, sell, offer for sale, gift, barter, exchange, or distribute this plant 

(http://www.in.gov/legislative/iac/T03120/A00180.PDF, http://www.dnr.illinois.gov/adrules/documents/17-

805.pdf).

 It is listed as a Federal Noxious Weed under the Plant Protection Act, which makes it illegal in the United 

States to import or transport between States without a permit.

 In a study by Maki and Galatowitsch (2004), H. polysperma was one of two federal noxious weeds purchased 

despite its federal status of being illegal to move across state lines.

 Moreover, Maki and Galatowitsch (2004) found that this plant may not be labeled with its scientific name or 

otherwise may be misidentified, as in a case where a vendor was selling Alternanthera sessilis as H. 

polysperma.

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5
1434

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 0 x 0 Unlikely

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 0.1 10 Low

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.5 50 Moderate

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

0 x 0 Unlikely

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
1435

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Hygrophila polysperma has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: High). 

This perennial aquatic plant inhabits freshwater lakes and streams. The literature predicts that H. 

polysperma has the potential to overwinter in the Great Lakes (Rixon et al. 2005). This species can 

tolerate temperatures of 4°C (Kasselmann 1995) to 30°C (GISD 2005b). It inhabits waters at depths of 

1.5-2.0 m and can photosynthesize in lower light levels than most native aquatic plant species (Spencer 

and Bowes 1984). Hygrophila polysperma is able to draw carbon dioxide from both water and 

atmosphere (Doyle et al. 2003). This species grows best at pH 5-7 (Spencer and Bowes 1985). Its 

nonindigenous occurrences in the United States have somewhat similar climates and abiotic conditions as 

the Great Lakes. Suitable habitats for H. polysperma are likely somewhat available in the Great Lakes. 

The effects of climate change on the Great Lakes, such as warmer water temperatures and shorter 

duration of ice cover, may improve habitat suitability for this species.

Although it can produce seeds, Hygrophila polysperma primarily propagates vegetatively, and forms 

many adventitious roots at nodes along the stems, which aids the rooting of dispersed fragments (Spencer 

and Bowes 1985). Hygrophila polysperma has a high regrowth potential from stem fragments (Spencer 

and Bowes 1985). Growth rate of H. polysperma is enhanced by higher flow rates (Van Dijk et al. 1986). 

It can spread rapidly to form dense monoculture stands; it expanded from 0.04 ha to over 0.41 ha in one 

year (Vandiver 1980). Hygrophila polysperma has spread extensively in the southeastern United States

and parts of Mexico.

Hygrophila polysperma may have compete with native species. When H. polysperma was experimentally 

grown with Ludwigia repens, L. repens experienced slower growth rate, produced fewer and shorter 

stems, and produced fewer branches per stem than when grown without the presence of H. polysperma

(Doyle et al. 2003). In addition, H. polysperma exhibits competitive ability when grown with L. repens; 

H. polysperma produces fewer but longer highly branched stems. This species forms dense monocultures 

that exclude native plants and is a superior competitor because of its low requirements for light and rapid 

growth (GISD 2005b, Nault and Mikulyuk 2009, Spencer and Bowes 1985, Robinson 2003).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3
1436

Unknown U

6

 It favors warm climates, although it can tolerate cooler temperatures down to 4 ̊C (Rixon et al. 2005, USEPA 

2008).

 It is also a perennial plant with low seasonality, which can maintain shoot biomass year round (Spencer and 

Bowes 1985, in Doyle et al. 2003).

 It can exist in a pH range of 6.5-7.8, a temperature range of 18-30°C (optimum 22-28 ̊C), and a water hardness 

level of 30-140 ppm (FNZAS 1988).

 Bowes (1987) sets the pH from 5-7, and states its leaves can draw CO2 from the water and from the atmosphere 

(Les 2005).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

8

 Rixon et al. 2005 predicted H. polysperma could overwinter in the Great Lakes.

 It favors warm climates, although it can tolerate cooler temperatures down to 4 ̊C (Rixon et al. 2005, USEPA 

2008).

 Due to low light saturation and compensation points, H. polysperma can photosynthesize at low light levels.

 Bowes (1987) states its leaves can draw CO2 from the water and from the atmosphere (Les 2005).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

 This species is an autotroph

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

9
1437

native species in the Great Lakes)

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

8

 In general, H. polysperma grows and spreads fast, can shade out other submersed plants, and is capable of 

occupying the whole water column.

 According to Doyle et al. (2003), H. polysperma has spread rapidly where it exists in Texas, historically 

occupying up to 20% of the Comal River’s area, where it is thought to out-compete native macrophytes.

Hygrophila polysperma was found to be a superior competitor to Ludwigia repens, a morphologically-similar 

macrophyte which coexists at with H. polysperma at a lower abundance in this area (Doyle et al. 2003).

 It has outcompeted Hydrilla verticillata, another nonindigenous nuisance macrophyte, in the flowing waters of 

Florida canals; however, it appears to be a poorer competitor in static waters (Van Dijk et al. 1986, Ramey 

2001).

 In contrast to the competitive ability of H. polysperma observed in the southeastern United States., scientists in 

New Zealand found H. polysperma to be a poor competitor when grown with New Zealand native macrophytes, 

Egeria densa, or Lagarosiphon major (the latter two macrophytes are native to South America and southern 

Africa, respectively) (Champion et al. 2007).

 During sampling on the San Marcos River, TX, Owens et al. (2001) found that H. polysperma was one of the 

most-abundant species in terms of biomass, accounting for up to a quarter of total plant biomass sampled 

(second only to the nonindigenous macrophyte H. verticillata). The authors observed the formation of large 

floating mats of H. polysperma, which are considered to be detrimental to native vegetation, decreasing 

sunlight availability, and creating anoxic conditions once decomposition occurs (Owens et al. 2001, Robinson 

2003).

 “H. polysperma may form dense single species stands that often do not provide ideal habitat or food for native 

wildlife. These native wildlife populations may be forced to relocate or perish, ultimately resulting in a loss of 

biodiversity and a disruption in the balance of the ecosystem.” (Robinson 2003)

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 H. polysperma stems are brittle, and easily fragment. These fragments easily develop new stands from rooted 

nodes of even small fragments (GISD 2005b).
1438

 Hygrophila polysperma reproduces asexually by fragmentation—adventitious roots grow at stem nodes—and 

sexually, though it is unknown how much of a role seeds play in its spread (Sutton 1996).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

8

 Hygrophila polysperma reproduces asexually by fragmentation—adventitious roots grow at stem nodes—and 

sexually, though it is unknown how much of a role seeds play in its spread (Sutton 1996).

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

 Native to temperate Asia (China - Guangdong, Guangxi, Yunnan) and tropical Asia (Bangladesh, Bhutan, 

India, Nepal, Pakistan, Cambodia, Laos, Myanmar, Thailand, Vietnam) (Hawaii Pacific Weed Risk Assessment

2012)

 North American nonindigenous occurrences are limited to Texas, Florida, South Carolina, and Virginia (USGS 

NAS 2015, EDDmapS 2015, USEPA 2008).

 It favors warm climates, although it can tolerate cooler temperatures down to 4 ̊C (Rixon et al. 2005, USEPA 

2008).

 It is also a perennial plant with low seasonality, which can maintain shoot biomass year round (Spencer and 

Bowes 1985).
1439

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

4

 It can exist in a pH range of 6.5-7.8, a temperature range of 18-30°C (optimum 22-28 ̊C), and a water hardness 

level of 30-140 ppm (FNZAS 1988).

 It favors warm climates, although it can tolerate cooler temperatures down to 4 ̊C (Rixon et al. 2005, USEPA 

2008).

 Bowes (1987) sets the pH from 5-7, and states its leaves can draw CO2 from the water and from the atmosphere 

(Les 2005).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

3

 This species occurs in lakes, streams and rivers, still and moving water, up to 3 m (10 ft) in depth. Grows from 

bottom to water surface (MI DEQ 2012).

 It grows from substrate to surface in water up to 10 feet deep, and also around edges, and forms dense stands 

which can later break off into floating mats—it prefers rivers and streams, but it may be found in slow streams 

and lakes (Ramey 2001).

 There is also a rare terrestrial form that grows in moist soil (McCann et al. 1996).

 Due to low light saturation and compensation points, H. polysperma can photosynthesize at low light levels.

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6
1440

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 Warmer temperatures are likely to improve habitat suitability

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 Due to low light saturation and compensation points, H. polysperma can photosynthesize at low light levels.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)
1441

Unknown U

9

 No other species are critical.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

 No facilitating species have been identified.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

-5%

 Grass Carp have low preference for it due to low palatability (Cuda and Sutton 2000) (although according to 

Ferriter et al. 1997, triploid Grass Carp have been successful at controlling it in canals).
1442

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

2

 This species is not commonly sold, there are no known nearby populations

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

6

 This species has been spread to Florida and Texas from southeast Asia.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6
1443

 It can spread rapidly to form dense monoculture stands; it expanded from 0.04 ha to over 0.41 ha in one year 

(Vandiver 1980).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 89

>100 High Adjustments

B. Critical species A*(1- 0%) 89

51-99 Moderate C. Natural enemy B*(1- 5%) 84.55

Control measures C*(1- 0%) 84.55

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low
1444

Section C: Potential for Impact

IMPACT RESULTS

Environmental: Moderate

Socio-Economic: High

Beneficial: Moderate

Hygrophila polysperma has the potential for moderate environmental impact if introduced to the 

Great Lakes.

Hygrophila polysperma can have negative impacts on native species and the ecosystem. This species 

grows quickly into dense mats that can reduce light availability and dissolved oxygen levels. It shades out 

native submerged plants (Ramey 2001) and can displace native plants when it occupies the entire water 

column. Surveys conducted shown that H. polysperma can spread rapidly to become one of the most 

abundant species where it has been introduced, displacing native species (Owens et al. 2001, Vandiver 

1980). In Texas, it rapidly spread to occupy 20% of the Comal River’s area, where it is thought to 

displace native macrophytes (Doyle et al. 2003). When H. polysperma was grown with Ludwigia repens, 

L. repens exhibited slower growth rates compared to when grown alone, suggesting that H. polysperma 

has superior competitive abilities (Doyle et al. 2003). Hygrophila polysperma can create anoxic 

conditions once decomposition occurs (Owens et al. 2001, Robinson 2003). The dense mats of H. 

polysperma can trap sediments and reduce water flows (Robinson 2003).

Hygrophila polysperma has the potential for high socio-economic impact if introduced to the Great 

Lakes. 

Dense mats of Hygrophila polysperma can provide breeding grounds for mosquito populations. The 

mosquito, Coquillettidia perturbans, reportedly attaches to submerged roots of H. polysperma to 

complete development and is a vector of eastern and western equine encephalomyelitis (Cuda and Sutton 

2000). This species is problematic, as it clogs irrigation and flood control canals and interferes with water 

control pumping stations (Cuda and Sutton 2000). It is costly to control H. polysperma infestations; in 

2006, Florida spent $14,000 to control H. polysperma covering 206 acres (FDEP 2007). Infestations of H. 

polysperma make navigation difficult and inhibit recreational use (Cuda and Sutton 2000, Robinson 

2003). The present of widespread, dense mats of H. polysperma can hinder fishing, boating, and 

swimming activities, causing a reduction lake property value (Robinson 2003). 

Hygrophila polysperma has the potential for moderate beneficial impact if introduced to the Great 

Lakes.

In India, H. polysperma seeds are used as a medicine (Spencer and Bowes 1985). Hygrophila polysperma

is commercially valuable as an ornamental plant and aquarium species (Cuda and Sutton 2000). 

Hygrophila polysperma is advertised for beginner aquarists because it is hardy and easy to grow. This 

species may increase water clarity when abundant (Osceola County 2012).

POTENTIAL ENVIRONMENTAL IMPACT

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels, is poisonous, a virus, bacteria, parasite, or a vector of one)? 
1445

Yes, and it has resulted in the reduction or extinction of one or more native species 

populations, affects multiple species, or is a reportable disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems, 

etc.)

1 

Not significantly 0 √

Unknown U

 No evidence of allelopathy or parasitism of this species (Hawaii Pacific Weed Assessment 2012)

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light, etc.)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, 

behavioral changes, etc.) on one or more native species populations

6 

Yes, and it has caused some noticeable stress to or decline of at least one native species 

population

1 √

Not significantly 0

Unknown U

 In general, H. polysperma grows and spreads fast, can shade out other submersed plants, and is capable of 

occupying the whole water column.

 According to Doyle et al. (2003), H. polysperma has spread rapidly where it exists in Texas, historically 

occupying up to 20% of the Comal River’s area, where it is thought to out-compete native macrophytes. H. 

polysperma was found to be a superior competitor to Ludwigia repens, a morphologically-similar 

macrophyte which coexists at with H. polysperma at a lower abundance in this area (Doyle et al. 2003).

 It has outcompeted Hydrilla verticillataI, another nonindigenous nuisance macrophyte, in the flowing 

waters of Florida canals; however, it appears to be a poorer competitor in static waters (Van Dijk et al. 

1986, Ramey 2001).

 In contrast to the competitive ability of H. polypsperma observed in the southeastern United States, 

scientists in New Zealand found H. polysperma to be a poor competitor when grown with New Zealand 

native macrophytes, Egeria densa, or Lagarosiphon major (the latter two macrophytes are native to South 

America and southern Africa, respectively) (Champion et al. 2007).

 During sampling on the San Marcos River, TX, Owens et al. (2001) found that H. polysperma was one of 

the most-abundant species in terms of biomass, accounting for up to a quarter of total plant biomass 

sampled (second only to the nonindigenous macrophyte H. verticillata). The authors observed the formation 

of large floating mats of H. polysperma, which are considered to be detrimental to native vegetation, 

decreasing sunlight availability, and creating anoxic conditions once decomposition occurs (Owens et al. 

2001, Robinson 2003).

 H. polysperma may form dense single species stands that often do not provide ideal habitat or food for 

native wildlife. These native wildlife populations may be forced to relocate or perish, ultimately resulting in 

a loss of biodiversity and a disruption in the balance of the ecosystem (Robinson 2003).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., added pressure to threatened/endangered species, significant reduction or extinction 

of any native species populations, creation of a dead end or any other significant alteration 

in the food web, etc.)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 1 
1446

population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

Not significantly 0

Unknown U √

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression, etc.)?

Yes, and it has caused a loss or alteration of genes which may be irreversible or has led to 

the decline or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles, etc.)?

Yes, and it has had a widespread, long term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been mild

1 √

Not significantly 0 

Unknown U

 In general, H. polysperma grows and spreads fast, can shade out other submersed plants, and is capable of 

occupying the whole water column.

 During sampling on the San Marcos River, TX, Owens et al. (2001) found that H. polysperma was one of 

the most-abundant species in terms of biomass, accounting for up to a quarter of total plant biomass 

sampled (second only to the nonindigenous macrophyte H. verticillata). The authors observed the formation 

of large floating mats of H. polysperma, which are considered to be detrimental to native vegetation, 

decreasing sunlight availability, and creating anoxic conditions once decomposition occurs (Owens et al. 

2001, Robinson 2003).

E6) Does it alter the physical ecosystem in some way (e.g., facilitated erosion/siltation, altered hydrology, 

altered macrophyte/phytoplankton communities, changes to substrate (physical or chemical), etc.)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 
1447

Unknown U

 In general, H. polysperma grows and spreads fast, can shade out other submersed plants, and is capable of 

occupying the whole water column.

 According to Doyle et al. (2003), H. polysperma has spread rapidly where it exists in Texas, historically 

occupying up to 20% of the Comal River’s area, where it is thought to replace native macrophytes.

 Dense stands of H. polysperma trap sediments, slow water flow in irrigation channels and waterways.” 

“Sediment levels increase with increasing H. polysperma abundance (Robinson 2003).

Environmental Impact Total 3

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 Establishment of H. polysperma could facilitate growth in pest mosquito (Coquillettidia perturbans) 

populations; C. perturbans reportedly attaches to submerged roots of H. polysperma to complete 

development and is a vector of eastern and western equine encephalomyelitis (Cuda and Sutton 2000).

S2) Does it cause damage to infrastructure (such as water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 Hygrophila polysperma can clog irrigation and flood control canals, and mats of it can block culverts and 

interfere with water control pumping stations (Cuda and Sutton 2000).
1448

 In 2006, there was an estimated 206 acres of H. polysperma establishment in Florida, although just 

$14,000 was allocated by the state for control costs (compared to nearly $12 million spent on another 

indigenous macrophyte, Hydrilla verticillata) (FDEP 2007). When nuisance-levels of establishment do 

occur, H. polysperma is difficult and expensive to control (FDEP 2007).

S3) Does it negatively affect water quality?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture, 

etc.)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g. through frequent water closures, 

equipment damage, decline of recreational species, etc.)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 Hygrophila polysperma is capable of occupying the whole water column; this reportedly interferes with 

navigation and can inhibit recreational use for swimming and boating (Cuda and Sutton 2000, Robinson 

2003).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U 

 The loss of recreational and aesthetic value can cause a decline in surrounding lake property value

(Robinson 2003).
1449

Socio-Economic Impact Total 8

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g. for fisheries, aquaculture, agriculture, bait, ornamental trade, etc.)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Hygrophila polysperma is a popular aquarium species and was an important plant grown in the Florida 

aquarium crop before its prohibition (Cuda and Sutton 2000). It is reportedly sold as an aquarium plant in 

the Great Lakes region, although the magnitude of its economic importance to this industry is not known 

(Rixon et al. 2005).

B3) Is it recreationally valuable (e.g. for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 1 √
1450

tourism 

Not significantly 0

Unknown U

 Hygrophila polysperma is a popular aquarium species and was an important plant grown in the Florida 

aquarium crop before its prohibition (Cuda and Sutton 2000).

 This species is recommended as hardy for beginners and easy to grow.

B4) Does the species have some medicinal or research value (outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1

Not significantly 0 √

Unknown U

 In India, the seeds if this species are used medicinally.

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0

Unknown U 

 Large amounts hydrilla, hygrophila or other aquatic plants (excluding algae) can result in increased water 

clarity, which is often considered desirable.

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species which is threatened, endangered species, or commercially valuable, etc.)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

Beneficial Effect Total 3

Total Unknowns (U) 0
1451

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1452

Scientific Name: Myriophyllum aquaticum

(Vell.) Verdc.

Common Name: Parrot Feather

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High 

Hitchhiking/fouling: High 

Unauthorized intentional release: High 

Stocking/planting/escape from recreational culture: Moderate 

Escape from commercial culture: Unknown

Transoceanic shipping: Unlikely

Myriophyllum aquaticum has a high probability of introduction to the Great Lakes (Confidence 

level: Moderate).

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentinal Release,

Escape from Recreational and Commercial Culture

With established nonindigenous populations in states adjacent to the Great Lakes, parrot feather has 

potential to be introduced to the Great Lakes from nearby water bodies. The closest parrot feather 

population to the Great Lakes has been recorded from Meserve Lake, Indiana, which drains though the 

Pigeon River into the St. Joseph River, a tributary of Lake Michigan (Wersal and Madsen 2011). 

Fragments of this plant are capable of transport by river currents and could also become attached to or 

entangled with recreational boats (e.g., propellers, trailer tires) or fishing gear. Its rhizomes are very tough 

and can be transported long distances on boat trailers, surviving for up to a year when kept moist and cool 

(Washington State Department of Ecology 2011).

Parrot feather has been an ornamental favorite in hanging baskets, fountains, and aquaria for more than a 

century due to its blue-green color, feather-like leaves, oxygenating properties, and cascading pattern of 

growth (Les and Mehrhoff 1999). Often sold under incorrect names, introductions of this species are 

usually attributed to the water garden and aquarium trades (Davis 1996, UF IFAS 2010, Les and Mehroff 

1999). It has escaped cultivation through mechanical fragmentation and unintentional plantings, readily 

taking root. In a Great Lakes regional study, this aquatic plant was found in 25% of the stores surveyed in 

Michigan and Ontario, near Lake Erie, between 2002 and 2003 (Rixon et al. 2005). Moreover, water 

garden plants are often left outside to overwinter, which can lead to unintentional escape during spring 

flooding. The locations of Ontario water gardens indentified by 2006 survey respondents suggests that 

many of these gardens are within the coastal regions of four of the five Great Lakes, though if these were 

also flood-prone areas was not determined (Marson et al. 2009).
1453

Parrot feather is of growing interest for environmental remediation of soil and water contaminated with 

chlorinated solvents, trinitrotoluene (TNT), and other nitrogenated explosive/aromatic compounds, but 

this is currently a technology in limited, experimental use (Medina et al. 2000, Nwoko 2010).

Among the Great Lakes states and provinces, M. aquaticum is prohibited in Illinois, Michigan, and 

Wisconsin and regulated in Minnesota. Furthermore, it is listed as a noxious weed by nine non-Great 

Lakes states (Alabama, Connecticut, Idaho, Maine, Massachusetts, Maryland, New Hampshire, Vermont, 

and Washington) (IISG 2011, GLPANS 2008, WIDNR 2011). Without more stringent laws regulating 

sale and disposal throughout the entire region, introduction could occur through disposal of aquarium 

fragments, unintentional escape from culture, or intentional unauthorized planting to support live trade.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Myriophyllum aquaticum has been recorded in Meserve Lake, Indiana (Wersal and Madsen 2011).

 Reproduction occurs by fragmentation of emergent and/or submersed shoots, roots, rhizomes, or attached plant 

fragments (UF IFAS 2010, Mabulu 2005). Fragments are capable of transport along river currents.

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 The closest M. aquaticum population to the Great Lakes has been recorded from Meserve Lake, Indiana, 

which drains though the Pigeon River into the St. Joseph River, a tributary of Lake Michigan (Wersal and 

Madsen 2011).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?
1454

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Fragments of parrot feather could become attached to or entangled with recreational boats (e.g., propellers, 

trailer tires) or fishing gear.

 Its rhizomes are very tough and can be transported long distances on boat trailers, surviving for up to a year 

when kept moist and cool (Washington State Department of Ecology 2011).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1 √

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 The closest M. aquaticum population to the Great Lakes has been recorded from Meserve Lake, Indiana, 

which drains though the Pigeon River into the St. Joseph River, a tributary of Lake Michigan (Wersal and 

Madsen 2011).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Often sold under incorrect names, introductions of this species are usually attributed to the water garden and 

aquarium trades (Davis 1996, Les and Mehroff 1999, UF IFAS 2010).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1 √

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 Parrot Feather has been an ornamental favorite in hanging baskets, fountains, and aquaria for more than a 

century due to its blue-green color, feather-like leaves, oxygenating properties, and cascading pattern of 

growth (Les and Mehrhoff 1999). 

 In a Great Lakes regional study, this aquatic plant was found in 25% of the Michigan and Ontario (near Lake 

Erie) stores surveyed between 2002 and 2003 (Rixon et al. 2005).
1455

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Often sold under incorrect names, introductions of this species are usually attributed to the water garden and 

aquarium trades (Davis 1996, UF IFAS 2010, Les and Mehroff 1999). Parrot feather has escaped cultivation 

through mechanical fragmentation and unintentional plantings, readily taking root.

 Water garden plants are often left outside to overwinter, which can lead to unintentional escape during spring 

flooding (Marson et al. 2009).

 Parrot Feather is of growing interest for environmental remediation of soil and water contaminated with 

chlorinated solvents, trinitrotoluene (TNT), and other nitrogenated explosive/aromatic compounds (Medina et 

al. 2000, Nwoko 2010).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75 

√

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 Among the Great Lakes states and provinces, M. aquaticum is prohibited in Illinois, Michigan, and Wisconsin 

and regulated in Minnesota. Furthermore, it is listed as a noxious weed by nine non-Great Lakes states 

(Alabama, Connecticut, Idaho, Maine, Massachusetts, Maryland, New Hampshire, Vermont, and Washington) 

(IISG 2011, GLPANS 2008, WIDNR 2011).

 The locations of Ontario water gardens identified by 2006 survey respondents suggest that many of these 

gardens are within the coastal regions of four of the five Great Lakes (Marson et al. 2009).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100 √

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 
1456

Unknown U

 Parrot Feather is commercially supplied to aquarium and water garden stores for resale.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U √

 At the time of this assessment, the nature of commercial activity involving parrot feather in the Great Lakes 

basin was not known.

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80 

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1
1457

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Vector Potential Scorecard

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 0.75 75 Moderate

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

100 x U U Unknown

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 1 Confidence Level Moderate
1458

Status: Established in North America, but not the Great Lakes

Myriophyllum aquaticum has a moderate probability of establishment if introduced to the Great 

Lakes (Confidence level: Moderate).

Myriophyllum aquaticum is a hardy species with broad environmental tolerances. It occurs as a floating 

plant in the deep water of nutrient-enriched lakes like the Great Lakes (Washington State Department of 

Ecology 2011). It is known to tolerate freezing temperatures in California’s Bay area winters (Aiken 

1981). However, this plant can be killed by extended periods of frost (WIDNR 2011) and so may benefit 

from warmer winters predicted to result from climate change.

Parrot feather grows vigorously and quickly following invasion in new habitats, forming dense canopies 

that occupy large amounts of space and block sunlight and oxygen exchange. As a result, this species 

outcompetes and replaces native flora that might be of more value to fish and wildlife (Stiers et al. 2011, 

WIDNR 2011).

Reproduction and dispersal of M. aquaticum in North America occurs by vegetative fragmentation, which 

is an effective method for short-range, but not long-range, dispersal (Les and Mehrhoff 1999). Although 

parrot feather’s natural dispersal potential is limited, this species is widespread outside its native range 

(Moody and Les 2010). Myriophyllum aquaticum has expanded its range mainly in the southern United 

States and may be relatively innocuous in the northeast due to a smaller number of occurrences (Hoyer et 

al. 1996). Nonetheless, this species has survived in southern New England and caused serious local 

infestations (WIDNR 2011). The rapid spread of M. aquaticum is correlated with its widespread 

cultivation and the transport of fragments by waterfowl or vehicles. When transport agents are not 

present, the threat of its escape and establishment depends more on the number of localities where it is 

grown. Unfortunately, M. aquaticum remains widely available from sources of cultivated water plants and 

dealers occasionally plant it intentionally to propagate a local supply (Aiken 1981, Les and Mehrhoff 

1999).

Nonindigenous M. aquaticum specimens collected from geographically diverse locations in North 

America have been found to have identical ITS genotypes and are all female. Seed production has not 

been recorded (Moody and Les 2010).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

8
1459

 Myriophyllum aquaticum is a hardy species with broad environmental tolerances. This species displays 

photosynthetic activity at pH levels of 6 to 8.5, depths of 0 to 10 meters, and temperatures from 10°C to 30°C, 

though it can survive even broader ranges (Robinson 2003, WIDNR 2011).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

4

 Myriophyllum aquaticum is known to tolerate freezing temperatures in California’s Bay area winters (Aiken 

1981). However, this plant can be killed by extended periods of frost (WIDNR 2011).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0
1460

Unknown U

7

 Myriophyllum aquaticum grows vigorously and quickly following invasion in new habitats, forming dense 

canopies that occupy large amounts of space and block sunlight and oxygen exchange. As a result, this species 

outcompetes and replaces native flora that might be of more value to fish and wildlife (Stiers et al. 2011, 

WIDNR 2011).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

U

 Parrot feather is a dioecious species, however only pistillate (female) plants are found outside of South 

America. Staminate (male) plants are rare even in native populations of South America (Orchard 1981). For 

this reason, seed production is not known to occur (Aiken 1981) and reproduction is exclusively vegetative in 

North America (Orchard 1981).

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

6

 Reproduction and dispersal of M. aquaticum in North America occurs by vegetative fragmentation, which is an 

effective method for short-range but not long-range dispersal (Les and Mehrhoff 1999).
1461

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

6

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

9

 Myriophyllum aquaticum occurs as a floating plant in the deep water of nutrient-enriched lakes like the Great 

Lakes (Washington State Department of Ecology 2011).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

9

 Myriophyllum aquaticum is a hardy species that can be established in a wide range of aquatic habitats. The 

species prefers nutrient rich and quiet or slow moving shallow waters but it has also been known to occur as a 

floating plant in the deep water of nutrient-enriched lakes. The species can also tolerate the salinity of coastal 

or brackish waters and is able to withstand routine water level fluctuations (Aiken 1981, Robinson 2003).
1462

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

6

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

3
1463

the species being assessed

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

0

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0
1464

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

U

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 Although parrot’s feather’s natural distribution is limited, it is widespread outside its native range. (Moody and 

Les 2010). Myriophyllum aquaticum has expanded its range mainly in the southern United States and may be 

relatively innocuous in the northeast due to a smaller number of occurrences (Hoyer et al. 1996). Nonetheless, 

this species has survived in southern New England and caused serious local infestations (WIDNR 2011).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6
1465

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

5

 The rapid spread of M. aquaticum is correlated with its widespread cultivation and the transport of fragments 

by waterfowl or vehicles. When transport agents are not present, the threat of its escape and establishment 

depends more on the number of localities where it is grown. Unfortunately, M. aquaticum remains widely 

available from sources of cultivated water plants and dealers occasionally plant it intentionally to propagate a 

local supply (Aiken 1981, Les and Mehrhoff 1999).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 78

>100 High Adjustments

B. Critical species A*(1- 0%) 78

51-99 Moderate C. Natural enemy B*(1- 0%) 78

Control measures C*(1- 0%) 78

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High 2
1466

2-5 Moderate Total # of questions unknown

6-9 Low

Confidence Level Moderate

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: Moderate

Beneficial: Moderate

Myriophyllum aquaticum has the potential for high environmental impact if introduced to the Great 

Lakes.

The United States Environmental Protection Agency (USEPA) (2008) predicted that M. aquaticum could 

have a high impact and spread rate in the Great Lakes, as it is adaptive to a variety of environments.

According to Les and Mehrhoff (1999), rapid spread has been relatively common in this macrophyte’s 

North American invasion history (Les and Mehrhoff 1999). Outside the United States, a risk assessment 

prepared for Australia in 1995 by Pacific Island Ecosystems at Risk recommended rejection of the plant 

for import on mainland due to its likelihood of becoming a pest (Mabulu 2005). By 2002, parrot feather 

was assessed as one of the top 200 invasive naturalized plants in Southeast Queensland, Australia (ranked 

#69 of 200) (Queensland Herbarium 2002).

Dense infestations of parrot feather can rapidly overtake small ponds and sloughs, changing their physical 

and chemical properties, including impeding water flow, which can result in increased flood duration and 

intensity. The spread of aquatic nonindigenous plants into a waterbody can also lead to increased rates of 

evapotranspiration and water loss. One mesocosm experiment found that colonization by M. aquaticum 

was correlated to an increase in water loss of about 1.5 to 2 times that experienced by an open water 

surface (Rosa et al. 2009).

Myriophyllum aquaticum can dramatically alter ecosystems by shading out algae, pondweeds, and 

coontail on which waterfowl feed (Ferreira and Moreira 1994, Washington State Department of Ecology 

2011). Floating mats of M. aquaticum have been measured at up to 26 kg of fresh weight in Europe and 

are capable of reducing the oxygen content of the water below to <1 mg O2L

-1

, which can be detrimental 

to fish (Hussner and Meyer 2009). In Germany, the infestation of these mats created anoxic, shaded 

conditions in shallow waters, and appeared to be correlated with a decline in native macrophyte diversity 

(Hussner et al. 2010).

In Chinese laboratory experiments, parrot feather outcompeted native species with respect to relative 

growth rate, with the most significant results on high-nutrient sediment (Xie et al. 2010). A separate 

mesocosm study by Wersal and Madsen (2011) found that the yield (biomass) of M. aquaticum was 

positively related to tissue nitrogen content, suggesting that high levels of nitrogen contribute to nuisance 

levels of growth. However, an inverse relationship existed between M. aquaticum yield and tissue 

phosphorus content. Wersal and Madsen (2011) proposed that high levels of phosphorus favored the 
1467

growth of algae (superior competitors in phosphorus uptake) causing shading in the water column and 

suppressing the growth of M. aquaticum (Wersal and Madsen 2011).

Stiers et al. (2011) compared Belgian lake sites that were heavily invaded (90-100% cover), semi-invaded 

(~25% cover), and uninvaded by M. aquaticum and found that native species richness was 57% lower in 

heavily invaded sites relative to uninvaded sites. Parrot feather cover was also negatively correlated with 

invertebrate species richness and abundance. The authors observed lowered levels of dissolved oxygen at 

some sites, as well as a dense mat of decomposed plant litter and sediments at the bottom of heavilyinvaded sites; they hypothesized that this condition created unsuitable habitat for invertebrate colonization 

(Stiers et al. 2011). Plant species that are rare (Utricularia vulgaris) and vulnerable (Hydrocharis morsusranae) IUCN Red List species in Belgium were absent in heavily invaded sites but present in semiinvaded sites (Steirs et al. 2011, Lansdown 2014). Furthermore, mayflies (Caenis spp.) were present in 

uninvaded sites, but were not reported in invaded sites (Steirs et al. 2011).

Myriophyllum aquaticum can also alter the cycling of heavy metals in aquatic systems. Cardwell et al. 

(2002) found that M. aquaticum accumulated the highest overall levels of metals (zinc, cadmium, copper, 

and lead) in its tissues of all 15 aquatic plants that underwent testing. While this suggests that M. 

aquaticum could be used as an important indicator species (see below), the consumption of M. aquaticum 

by grazers could increase the bioaccumulation of heavy metals in the food web. 

Myriophyllum aquaticum has the potential for moderate socio-economic impact if introduced to the 

Great Lakes.

Parrot feather infestations have been reported in both natural and man-made water bodies, including 

lakes, ponds, canals, drainage and irrigation ditches, and lagoons. Plants and floating mats of vegetation 

are sometimes uprooted, choking waterways, inhibiting navigation, and potentially blocking pumps or 

drainage (Engineer Research and Development Center 2007, Sheppard et al. 2006). Dense growth can 

also diminish the recreational value and seriously affect the perceived aesthetic qualities of infested 

waterways (Banfield 2008, Washington State Department of Ecology 2011).

Myriophylum aquaticum monocultures provide prime mosquito habitat; higher parrot feather density has 

been correlated with higher mosquito egg and larval abundance (Orr and Resh 1992), which may lead to 

increased prevalence of mosquito-born diseases. 

Myriophyllum spp. have invaded rice paddies could adversely affect wild rice (Zizania palustris) found in 

the upper Great Lakes (Quayyum et al. 1999). One account by South African farmers also reported that 

tobacco crops gained a red tint (reducing the sale value of the crop) when irrigated with water from an 

area colonized by M. aquaticum roots (Cilliers 1999). 

Myriophyllum aquaticum has the potential for moderate potential benefits if introduced to the Great 

Lakes.

Assessment protocols have been developed using M. aquaticum as a primary indicator species of

sediment toxicity in potentially polluted areas (Feiler et al. 2004, Knauer et al. 2008). It is an important 

species in the aquarium trade and can be found in shops in both the American and Canadian Great Lakes 

regions (Marson et al. 2009, Rixon et al. 2005). It is reportedly sold as an “oxygenating plant” in Europe 

(Sheppard et al. 2006).

Parrot feather may provide cover for some aquatic organisms (Washington State Department of Ecology 

2011). Parker et al. (2007) found that beavers (Castor canadensis) in Georgia fed on M. aquaticum to the 
1468

extent that invasive populations were reduced, although no strong preference for this plant species over 

others was documented. Myriophyllum aquaticum could be used for nitrogen and phosphorus remediation 

(e.g., in a constructed wetland remediating nutrient runoff), but Polomski et al. (2009) found that other 

invasive macrophytes (Eichhornia crassipes and Pistia stratiotes) had equal or greater uptake efficiency 

levels relative to M. aquaticum. Parrot feather can also aid in environmental remediation of soil and water 

contaminated with chlorinated solvents, trinitrotoluene (TNT), and other nitrogenated explosive/aromatic 

compounds (Medina et al. 2000, Nwoko 2010).

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 

Not significantly 0

Unknown U √

 Cardwell et al. (2002) found that M. aquaticum accumulated the highest overall levels of metals (zinc, 

cadmium, copper, and lead) in its tissues of all 15 aquatic plants that underwent testing. The consumption of M. 

aquaticum by grazers could increase the bioaccumulation of heavy metals in the food web.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 Stiers et al. (2011) compared Belgian lake sites that were heavily invaded (90-100% cover), semi-invaded 

(~25% cover) and uninvaded by M. aquaticum, and found that native species richness was 57% lower in 

heavily invaded sites relative to uninvaded sites. Myriophyllum aquaticum cover was also negatively correlated 

with invertebrate species richness and abundance.

 Plant species that are rare (Utricularia vulgaris) and vulnerable (Hydrocharis morsus-ranae) IUCN Red List 

species in Belgium were absent in heavily invaded M. aquaticum sites but present in semi-invaded sites (Steirs 

et al. 2011, Lansdown 2014).

 In China, M. aquaticum outcompeted native species in the laboratory with respect to relative growth rate, with 

the most significant results on high-nutrient sediment (Xie et al. 2010).

 In a mesocosm study, Wersal and Madsen (2011) found that the yield (biomass) of M. aquaticum was positively 

related to tissue nitrogen content, suggesting that high levels of nitrogen contribute to nuisance levels of 
1469

growth. However, an inverse relationship existed between M. aquaticum yield and tissue phosphorus content. 

Wersal and Madsen (2011) proposed that high levels of phosphorus favored the growth of algae (superior 

competitors in phosphorus uptake) causing shading in the water column and suppressing the growth of M. 

aquaticum (Wersal and Madsen 2011).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0

Unknown U √

 Myriophyllum aquaticum can dramatically alter ecosystems by shading out algae, pondweeds, and coontail on 

which waterfowl feed (Ferreira and Moreira 1994, Washington State Department of Ecology 2011).

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 Floating mats of M. aquaticum have been measured at up to 26 kg of fresh weight in Europe and are capable of 

reducing the oxygen content of the water below to <1 mg O2L

-1

(Hussner and Meyer 2009).

 In Germany, the infestation of M. aquaticum mats created anoxic, shaded conditions in shallow waters, and 

appeared to be correlated with a decline in native macrophyte diversity (Hussner et al. 2010).
1470

 Myriophyllum aquaticum can alter the cycling of heavy metals in aquatic systems. Cardwell et al. (2002) found 

that M. aquaticum accumulated the highest overall levels of metals (zinc, cadmium, copper, and lead) in its 

tissues of all 15 aquatic plants that underwent testing.

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 

Unknown U

 Myriophyllum aquaticum can dramatically alter ecosystems by shading out algae in the water column 

(Washington State Department of Ecology 2011).

 In Germany, the infestation of M. aquaticum mats created shaded conditions in shallow waters, and 

appeared to be correlated with a decline in native macrophyte diversity (Hussner et al. 2010).

 Dense infestations can rapidly overtake small ponds and sloughs, changing their physical and chemical 

properties, including impeding water flow, which can result in increased flood duration and intensity. 

 The spread of aquatic nonindigenous plants into a waterbody can also lead to increased rates of 

evapotranspiration and water loss. One mesocosm experiment found that colonization by M. aquaticum

was correlated to an increase in water loss of about 1.5 to 2 times that experienced by an open water 

surface (Rosa et al. 2009).

 Senescence of parrot feather can leave a dense mat of decomposed plant litter and sediments at the bottom 

of heavily-invaded sites that may create unsuitable habitat for invertebrate colonization (Stiers et al. 2011).

Environmental Impact Total 18

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1471

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1

Not significantly 0 

Unknown U √

 Myriophyllum aquaticum monocultures provide prime mosquito habitat; increasing density has been correlated 

with increasing egg and larval abundance in invaded waterbodies (Orr and Resh 1992), which may lead to 

increased prevalence of mosquito-borne diseases.

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1 √

Not significantly 0

Unknown U

 Plants and floating mats of vegetation are sometimes uprooted, choking waterways, inhibiting navigation, and 

potentially blocking pumps or drainage (Engineer Research and Development Center 2007, Sheppard et al. 

2006).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U √

 One account by South African farmers reported that tobacco crops gained a red tint (reducing the sale value of 

the crop) when irrigated with water from an area colonized by the roots of M. aquaticum (Cilliers 1999). 
1472

 Myriophyllum spp. have invaded rice paddies could adversely affect wild rice Zizania palustris found in the 

upper Great Lakes (Quayyum et al. 1999).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 Plants and floating mats of M. aquaticum are sometimes uprooted, choking waterways and inhibiting 

navigation (Engineer Research and Development Center 2007, Sheppard et al. 2006). Dense growth can 

diminish the recreational value of water bodies (Washington State Department of Ecology 2011).

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 √

Not significantly 0 

Unknown U

 Like other plants that form dense growths, M. aquaticum can seriously affect the perceived

aesthetic qualities of infested waterways (Banfield 2008).

Socio-Economic Impact Total 3

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1473

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Parrot feather is an important species in the aquarium trade, and can be found in shops in both the American 

and Canadian Great Lakes regions (Marson et al. 2009, Rixon et al. 2005). It is reportedly sold as an 

“oxygenating plant” in Europe (Sheppard et al. 2006).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 Parrot feather is an important species in the aquarium trade, and can be found in shops in both the American 

and Canadian Great Lakes regions (Marson et al. 2009, Rixon et al. 2005). It is reportedly sold as an 

“oxygenating plant” in Europe (Sheppard et al. 2006).

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √
1474

Not significantly 0 

Unknown U

 Assessment protocols have been developed using M. aquaticum as a primary indicator species of sediment 

toxicity in potentially polluted areas (Feiler et al. 2004, Knauer et al. 2008).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 

 Myriophyllum aquaticum could be used for nitrogen and phosphorus remediation (e.g., in a constructed 

wetland remediating nutrient runoff), but Polomski et al. (2009) found that other invasive macrophytes 

(Eichhornia crassipes and Pistia stratiotes) had equal or greater uptake efficiency levels relative to M. 

aquaticum.

 Parrot feather could also be used for environmental remediation of soil and water contaminated with 

chlorinated solvents, trinitrotoluene (TNT), and other nitrogenated explosive/aromatic compounds (Medina et 

al. 2000, Nwoko 2010).

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0

Unknown U √

 It may provide cover for some aquatic organisms (Washington State Department of Ecology 2011).

 Parker et al. (2007) found that beavers (Castor canadensis) in Georgia fed on M. aquaticum to the extent that 

invasive populations were reduced, although no strong preference for this plant species over others was 

documented.

Beneficial Effect Total 4

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1475

Scientific Name: Pistia stratiotes

Linnaeus

Common Name: Water Lettuce

Synonyms: laitue d'eau, pistie (French), Lechuguilla de agua, lechuguita de agua, repollo de agua 

(Spanish)

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High

Hitchhiking/fouling: High

Unauthorized intentional release: High

Stocking/planting/escape from recreational culture: High

Escape from commercial culture: Unknown

Transoceanic shipping: Unlikely

Pistia stratiotes has a high probability of introduction to the Great Lakes (Confidence level: 

Moderate). 

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Unauthorized Intentional 

Release, Escape from Recreational and Commecial Culture

Pistia stratiotes occurs in close proximity to the Great Lakes basin. It is found during spring through the 

fall in Lake St. Clair (Adebayo et al. 2011), Detroit River, and inland waters in Ontario, Ohio, New York, 

and Minnesota (Cochran et al. 2006).

Pistia stratiotes spreads via vegetative fragmentation and water dispersal. Fragments or seeds of P. 

stratiotes may potentially be introduced to the Great Lakes by dispersal. Pistia stratiotes can be 

unintentionally transported to the Great Lakes by hitchhiking on boats and recreational equipment. 

This species is part of the aquarium trade (Parsons and Cuthbertson 2001). According to a study on 

aquarium and pet stores near Lakes Erie and Ontario, 20% of stores surveyed carried Pistia stratiotes

(Rixon et al. 2005). Pistia stratiotes may be released into the Great Lakes when aquarists dispose this 

plant into waterways. This species is planted in water gardens and may be unintentionally introduced to 

the Great Lakes. It is unknown whether this species is commercially cultured in the Great Lakes region. 

Pistia stratiotes is not known to be taken up or transported by ballast water.
1476

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 Water lettuce can spread between water bodies via plant material, such as rosettes or seeds (OMNR 2010).

 Water lettuce is found during the spring, summer, and fall seasons at various locations (Lake St. Clair, Detroit 

River, and inland areas of Ontario, Ohio, New York, Minnesota) in the Great Lakes basin (Cochran et al. 2006, 

OMNR 2010, Adebayo et al. 2011, MISIN 2013, USDA NRCS 2013).

 Water lettuce likely has not yet established reproducing populations within the Great Lakes basin (Eyraud and 

MacIsaac 2013).

1b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 Water lettuce is found during the spring, summer, and fall seasons at various locations (Lake St. Clair, Detroit 

River, and inland areas of Ontario, Ohio, New York, Minnesota) in the Great Lakes basin (Cochran et al. 2006, 

OMNR 2010, Adebayo et al. 2011, MISIN 2013, USDA NRCS 2013).

 Water lettuce likely has not yet established reproducing populations within the Great Lakes basin (Eyraud and 

MacIsaac 2013).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 This species can be transported with boats, boat trailers, and other equipment (e.g., fishing or scuba gear) 

(OMNR 2010). 
1477

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1 √

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 Water lettuce is found during the spring, summer, and fall seasons at various locations (Lake St. Clair, Detroit 

River, and inland areas of Ontario, Ohio, New York, Minnesota) in the Great Lakes basin (Cochran et al. 2006, 

OMNR 2010, Adebayo et al. 2011, MISIN 2013, USDA NRCS 2013).

 Water lettuce likely has not yet established reproducing populations within the Great Lakes basin (Eyraud and 

MacIsaac 2013).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 Water lettuce is also used as an ornamental plant in aquaria, ponds, and outdoor water gardens; it may be 

planted near or along shorelines and escape into new areas as plant material is discarded into a waterway or 

carried off by flooding during rain events (OMNR 2010).

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1 √

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1

Unknown U

 An internet search of “water lettuce for sale” yielded many online stores that would ship this species, as well as 

availability for direct sale at local garden supply stores.

 Sale was also verified in the Great Lakes region by (Adebayo et al. 2011).

 According to a survey of aquarium and pet stores near Lakes Erie and Ontario, 20% of stores surveyed carried 

Pistia stratiotes (Rixon et al. 2005).

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?
1478

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 Water lettuce is also used as an ornamental plant in aquaria, ponds, and outdoor water gardens; it may be 

planted near or along shorelines and escape into new areas as plant material is discarded into a waterway or 

carried off by flooding during rain events (OMNR 2010).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1 √

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 This species is not on the United States Federal Noxious Weed List, nor on any Great Lakes state noxious weed 

list (only listed in Alabama, California, Connecticut, Florida, Mississippi, South Carolina, and Texas; import 

prohibited in Louisiana) (USDA NRCS 2013).

 Sale was also verified in the Great Lakes region by (Adebayo et al. 2011).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 

Unknown U √

 It is not known if this species is commercially cultured in the Great Lakes.

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5
1479

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U √

 This species is not on the United States Federal Noxious Weed List, nor on any Great Lakes state noxious weed 

list (only listed in Alabama, California, Connecticut, Florida, Mississippi, South Carolina, and Texas; import 

prohibited in Louisiana) (USDA NRCS 2013).

 It is not known if this species is commercially cultured in the Great Lakes.

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

 This species requires sufficient light, warm temperatures, and fresh water and is thus unlikely to survive ballast 

water regulations.

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U
1480

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not including the Great Lakes.

Pistia stratiotes has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High). 

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 1 100 High

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 1 100 High

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

U x U U Unknown

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 2 Confidence Level Moderate
1481

Pistia stratiotes inhabits tropical and subtropical lakes, reservoirs, and slow-flowing streams (Parsons and 

Cuthbertson 2001). Pistia stratiotes does best in warm waters, as it is killed by frost. Pistia stratiotes

exhibits optimal growth at water temperatures of 22-30°C (Kasselmann 1995). It can tolerate 

temperatures as low as 15°C and as high as 35°C. This species has been observed to overwinter in the Erft 

River, Germany; the water temperature in that river is abnormally warm (>11°C) and only leaves that 

remained submerged survived (Hussner et al. 2010). Its seeds can survive for at least 2 months in water at 

4°C and for a few weeks in ice at -5°C (Parsons and Cuthbertson 2001); its seeds have the potential to 

overwinter in the Great Lakes. Pistia stratiotes reproduces rapidly though seed production and vegetative 

fragmentation. Its short, brittle stolons that are involved in vegetative fragmentation may aid its 

establishment in the Great Lakes.

Pistia stratiotes has a widespread distribution encompassing 40 countries (Holm 1991), and occurs on 

every continent except Antarctica. This species is capable of expanding its distribution quickly. After 1 

year, this species had rapidly spread and covered an entire lake (Sridhar and Sharma 1980, Venema 

2001).

The native and introduced ranges of P. stratiotes have somewhat similar climatic and abiotic conditions 

as the Great Lakes; the Great Lakes may have lower air temperatures and lower water temperatures. The 

effects of climate change may make the Great Lakes a more suitable environment for the establishment of 

P. stratiotes. Warmer water temperatures and shorter duration of ice cover may aid the establishment of 

P. stratiotes. Freshwater lakes and slow-flowing streams in the Great Lakes may provide suitable habitats 

for P. stratiotes.

Pistia stratiotes has outcompeted other species where it has been introduced. Three years after P. 

stratiotes was first observed in Slovenia, it had covered the whole water surface and populations of native 

freshwater plants, Ceratophyllum demersum, Myriophyllum spicatum, Najas marina, and Trapa natans, 

had declined (Šajna et al. 2007). 

Surveillance and management efforts are currently underway to detect, control, and/or eradicate this plant 

in Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). However, a basin-wide monitoring 

program is lacking (Dupre 2011).

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

4
1482

 Rivers (2002) noted that for P. stratiotes to survive, it requires a wet, temperate habitat. It is usually found in 

lakes and rivers; however, it can also survive in mud.

 Pistia stratiotes can endure temperature extremes of 15°C (59°F) and 35°C (95°F). The optimal growth 

temperature range for the plant is 22-30°C (72-86°F) (Kasselmann 1995).

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0

Unknown U

1

 Pistia stratiotes can endure temperature extremes of 15°C (59°F) and 35°C (95°F). The optimal growth 

temperature range for the plant is 22-30°C (72-86°F) (Kasselmann 1995).

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

 This species is an autotroph.

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

0
1483

species in the Great Lakes)

Unknown U

9

 Mats reduce or eliminate light for submerged hydrophytes, epiphytic, and planktonic algae (Attionu 1976).

 In Slovenia, as early as three years after the first observation of P. stratiotes, native freshwater plants 

(Ceratophyllum demersum L., Myriophyllum spicatum L., Najas marina L. and Trapa natans L.) in this speciesrich wetland habitat were on decline, because the whole water surface was covered with a dense mat that 

remained closed even during the winter (Šajna et al. 2007).

 Oxygen and light limitations by this species kill native plants, fish, and wildlife (Chokder 1968, FDEP 2007).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3

Low 0

Unknown U

6

 This species has prolific seed production (>2000/m2) (Randall 2003).

 Many species in the Araceae Family are rhizomatous.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

7

 Water lettuce has short, brittle stolons that make it susceptible to vegetative reproduction (Rivers 2002).
1484

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

3

 The main requirement of this species is sufficient temperature, in which the Great Lakes is very dissimilar from 

native and introduced ranges of this species. The optimal growth temperature range for the plant is 22-30°C 

(72-86°F) (Kasselmann 1995).

 Rivers (2002) noted that for P. stratiotes to survive, it requires a wet, temperate habitat. It is usually found in 

lakes and rivers; however, it can also survive in mud.

 Pistia stratiotes can endure temperature extremes of 15°C (59°F) and 35°C (95F°). The optimal growth 

temperature range for the plant is 22-30°C (72-86°F) (Kasselmann 1995).

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

3

 Pollution in the Great Lakes is similar to that where water lettuce is currently found; it thrives in ecologically 

disturbed habitats with high nutrient concentrations (Sharma 1984, Neuenschwander et al. 2009).

 Pistia statiotes is freshwater species that prefers still or slowly-moving waters, with no other major 

requirements asides from temperature (can endure temperature extremes of 15° C (59° F) and 35° C (95°) 

(Kasselmann 1995).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3
1485

Scarce (Suitable habitats are rarely found) 0

Unknown U

1

 It is unlikely to find habitat with suitable temperature for survival through winter (can only tolerate 

temperatures to 59°F). The optimal growth temperature range for the plant is 22-30° C (72-86° F) 

(Kasselmann 1995).

 However, this species has successfully over-wintered in a temperate climate zone in Slovenia (mean winter 

temperatures 0 to -3°C). There, it covered nearly the entire water body where thermal springs caused elevated 

temperatures. Thus, this species may persist in small populations where water temperature remains elevated 

(despite cold air temperatures), such as a discharges from power stations (Šajna et al. 2007).

 It is also unlikely to find habitat with suitable temperatures to provide sufficient time for seeds that have 

overwintered to germinate in time to permit the production of seeds during the second growing season 

(Cochran et al. 2006). Pieterse et al. (1981) indicated that seeds do not germinate until temperature exceeds 

20°C. However, seeds can survive temperatures of -5°C (Pieterse et al. 1981).

 Otherwise, it inhabits slow moving waters in streams, rivers, lakes, ponds, and wet ditches and could find 

suitable habitat (Thompson 2000).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0

Unknown U

8

 Warmer air/water temperatures and/or less severe winters may allow for either over-wintering of adult plants 

or successive years of seed production (NCEA 2008, Hussner et al. 2010).

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3
1486

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 This species is an autotroph, with no specific nutrient requirements.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9

 No other species are critical.

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0
1487

Unknown U

0

 No facilitating species have been identified.

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

 This species has not been controlled by any natural enemy in its introduced range, and no species exists in the 

Great Lakes that would be expected to control it.

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

7

 Given the widespread availability of this plant for purchase, lack of regulations, and the repeated introduction 

events (e.g., in the Detroit River and Lake St Clair, Eyraud and MacIsaac 2013) this plant has had frequent 

inoculations. Also, given the vegetative reproduction, even a small population of this plant could be considered 

moderate.

HISTORY OF INVASION AND SPREAD
1488

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

9

 This species has spread to every continent except Antarctica (alleged native of South America) (Cordo et al.

1981).

 This species has invaded over 40 countries (Holm 1991).

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

7

 This species shows explosive growth in suitable habitats (e.g., can cover a lake 700 m x 135 m in single year) 

(Sridhar and Sharma 1980, Venema 2001).

 Rapid vegetative reproduction allows water lettuce to cover an entire lake, from shore to shore, with a dense 

mat of connected rosettes in a short period of time. In Florida, water lettuce has been known to have densities 

of up to 1,000 rosettes per m2(Rivers 2002).

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

-20% total 

points (at 
1489

its establishment and spread) end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

-30%

 This species is not regulated in any way and is still sold throughout the Great Lakes.

 Surveillance and management efforts are currently underway to detect, control and/or eradicate this plant in 

Michigan (MI DEQ 2013) and Wisconsin (Falck et al. 2010). However, a basin-wide monitoring program is 

lacking (Dupre 2011).

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 83

>100 High Adjustments

B. Critical species A*(1- 0%) 83

51-99 Moderate C. Natural enemy B*(1- 0%) 83

Control measures C*(1- 30%) 58.1

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: High

Socio-Economic: High

Beneficial: Moderate

Pistia stratiotes has the potential for high environmental impact if introduced to the Great Lakes.

Pistia stratiotes may have detrimental impacts on other species and the environment. Pistia stratiotes

produces α-asarone, a phenylpropanoid with antialgal activity (Aliotta et al. 1991), so it may interfere 
1490

with the growth processes in algae. Pistia stratiotes causes high evapotranspiration rates where it occurs 

(Sharma 1984). By growing in dense mats, P. stratiotes can shade out and reduce the amount of light 

available to submerged macrophytes and planktonic algae (Attionu 1976). In addition, its dense cover 

may reduce water temperature, reduce pH, promote stratification, and inhibit mixing of the water by wind 

(Attionu 1976). As a result of its inhibition of hydrophyte and algal growth, the respiratory activity of its 

roots, decomposition when it dies, and the restriction of wind-generated mixing, P. stratiotes can reduce 

the amount of dissolved oxygen where it occurs (Attionu 1976, Šajna et al. 2007, Sridhar and Sharma 

1985). It is suspected that the oxygen and light limitations caused by P. stratiotes may have killed native

plants, fish, and wildlife (FDEP 2007). Three years after P. stratiotes was first observed in Slovenia, there 

was a decline in native freshwater plants (Ceratophyllum demersum, Myriophyllum spicatum, Najas 

marina, and Trapa natans) (Šajna et al. 2007). 

Pistia stratiotes has the potential for high socio-economic impact if introduced to the Great Lakes. 

Pistia stratiotes is among the world’s worst weeds (Holm 1991) and has received significant media 

attention (de la Cruz 2014, Spear 2014).

Pistia stratiotes mats provide habitat for disease carrying mosquitos, such as malaria vectors Anopheles

and Mansonia (FDEP 2007, Lounibos and Dewald 1989, Parsons and Cuthbertson 2001, Rejmankova et 

al. 1991). Mansonia larvae perforate leaves and roots of P. stratiotes to reach air chambers (Lounibos and 

Dewald 1989). Taeniorhynchus (Mansonioides) africanus and Anopheles gambiae breed in ponds and 

streams that are clogged with P. stratiotes (Philip 1930). 

Pistia stratiotes causes damages to infrastructure. Infestations of this species can block waterways, 

reducing the efficiency of irrigation and hydroelectric power (Howard and Harley 1997). Dense mats of 

P. straiotes reduce water flow, damages flood control structures, and can create dams against bridges 

(FDEP 2007). Pistia stratiotes may impact recreation, as it interferes with navigation and fishing 

(Labrada and Fornasari 2002). Florida spent about $1.4 million dollars in 2005-2006 to treat P. stratiotes

(FDEP 2007). 

Pistia stratiotes has the potential for moderate beneficial impact if introduced to the Great Lakes.

This plant has the fiber content, carbohydrate, and crude protein levels that are comparable with quality 

forages (Parsons and Cuthbertson 2001). This plant can be fed to pigs, but cows find it unpalatable. Pistia 

stratiotes is valued as an ornamental plant in water gardens. Research has been conducted to utilize this 

species for biofuels and water remediation (Lu et al. 2010, Mishima et al. 2008). Pistia stratiotes is used 

in Ayurvedic medicine for its diuretic, antidiabetic, and antidermatophytic, antifungal and antimicrobial 

properties.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)?

Yes, and it has impacted threatened/endangered species, resulted in the reduction or extinction 

of one or more native populations, affects multiple species, or is a reportable disease

6
1491

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and ecosystems)

1 √

Not significantly 0

Unknown U

 Pistia stratiotes produces α-asarone, a phenylpropanoid with antialgal activity that interferes with growth 

processes in plants (Aliotta et al. 1991).

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 √

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 

Not significantly 0

Unknown U

 Mats of P. stratiotes reduce or eliminate light for submerged hydrophytes, epiphytic, and planktonic algae 

(Attionu 1976).

 In Slovenia, as early as three years after the first observation of P. stratiotes, native freshwater plants 

(Ceratophyllum demersum L., Myriophyllum spicatum L., Najas marina L., and Trapa natans L.) declined in a 

species-rich wetland habitat because the whole water surface was covered with a dense mat that remained 

closed even during the winter (Šajna et al. 2007).

 Oxygen and light limitations caused by P. stratiotes killed native plants, fish and wildlife (Chokder 1968, FDEP

2007).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

 This species has not been documented to be involved in predator-prey relationships.

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 1 
1492

individual level

Not significantly 0 √

Unknown U

 No genetic effects have been observed.

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6 √

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 

Not significantly 0 

Unknown U

 As a result of poor hydrophytic and algal growth, the respiratory activity of its roots, the decay of dead plants 

and restriction of wind-generated mixing, dissolved oxygen became markedly depleted and the water more 

acidic at sites with dense mats of Pistia stratiotes (Attionu 1976, Sridhar and Sharma 1985). Two sites with 

dense mats were included in the Attionu (1976) study:

o Dissolved oxygen levels of water immediately under mats were about half the DO levels of water 

in open water areas, in both October and January at both dense sites (Attionu 1976).

o Oxygen profiles showed dissolved oxygen around 5% saturation at 10 m and 0% saturation at 20 

m under Pistia stratiotes mats on River Dayi (Figure 2) (Attionu 1976).

o Oxygen profiles showed dissolved oxygen around 15% saturation at 1 m and 0% saturation at 9 m 

under Pistia stratiotes mats on River Pawnpawm (Figure 3) (Attionu 1976).

o Mean pH of water was measured at two times of the year at River Dayi: mean pH under mats was 

6.1, and mean pH in open water areas was 7 in October; mean pH of water under mats was 6.4, 

and mean pH in open water areas was 8.2 in January (Attionu 1976).

o Mean pH of water under mats was measured at one time of the year at River Pawnpawm: mean 

pH under mats was 6.9, and mean pH in open water areas was 7.4 in November (Attionu 1976).

 Dissolved oxygen values declined by more than 50% when measured under the P. stratiotes cover, reaching 

only 2.5 mg/L, a critical value for fish survival (Šajna et al. 2007).

 Chemical control measures (diquat and carfentrazone) used for Pistia stratiotes also impact water quality 

(FDEP 2007).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 √

Not significantly 0 

Unknown U

 Pistia stratiotes alters the physio-chemical condition of substrate (Attionu 1976).
1493

 Evapotranspiration rates with Pistia stratiotes are 8-17x greater than evaporation rates (without Pistia) 

(Sharma 1984).

 Pistia stratiotes increased sedimentation by shredding roots and shoots (FDEP 2007).

Environmental Impact Total 14

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6 √

Yes, but negative consequences have not been widespread, long lasting, or severe 1 

Not significantly 0

Unknown U

 Pistia stratiotes can also harbor disease-carrying mosquitoes such as species of the malaria vectors Anopheles

and Mansonia (Lounibos and Dewald 1989, Rejmankova et al. 1991). The larvae of Mansonia perforate leaves 

and roots of P. stratiotes to reach air chambers (Lounibos and Dewald 1989).

 Taeniorhynchus (Mansonioides) africanus, Théo., and Anopheles gambiae, Giles (costalis, Theo.) mosquitoes 

breed in ponds and even in streams that become clogged during low water with abundant growths of water 

lettuce (Pistia stratiotes), to which the immature stages attach themselves for purposes of respiration (Philip 

1930).

 Pistia stratiotes is responsible for “forming dense aggregations of free floating vegetation, known as suds, 

which in swampy areas have claimed many lives in the Sudan” (Sridhar and Sharma 1980).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?
1494

Yes, it is known to cause significant damage 6 √

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0

Unknown U

 Pistia stratiotes restricts water flow in irrigation and flood control canals (OMNR 2010).

 Pistia stratiotes creates dams against bridges and reduces water flow at flood control structures (FDEP 2007).

 Reports mention impacts of this type that occur (but are not quantified) throughout water bodies in Africa 

(Sridhar and Sharma 1980, Holm 1991).

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

 There are no reports of this.

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 

Not significantly 0 

Unknown U

 Waterways can be blocked, and the efficiency of irrigation (agriculture) and hydro generation (energy) 

impaired (Howard and Harley 1997).

 Pistia stratiotes clogs rivers and canals, interferes with the activity of hydroelectric power stations, hampers 

fishing, hampers navigation, and negatively affects water control and use for agricultural purposes (Labrada 

and Fornasari 2002).

 From 2005-2006, treatment of P. stratiotes in Florida water cost about $1.4 million dollars (40% of 3.5 million 

dollars) (FDEP 2007).

 Pistia stratiotes can invade rice fields, severely limiting the growth of this crop (Sculthorpe 1985).

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6 √

Yes, but negative consequences have been small 1 

Not significantly 0

Unknown U

 People are affected by reduction of the fish catch, inability to travel by boat, and consequent isolation from 

gardens, markets, and health services caused by P. stratiotes (Howard and Harley 1997).
1495

 Pistia stratiotes clogs waterways, making boating, fishing, and almost all other water activities difficult if not 

impossible.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6 √

Yes, but negative consequences have been small 1 

Not significantly 0 

Unknown U

 Pistia stratiotes is one of the world’s worst weeds (Holm 1991), with significant media attention. While there 

has been no formal study of this indirect value (aesthetic/natural), the dense and unavoidable mats would 

certainly impact these values. Evidence of the undesirable nature of this plant is seen in the money spent to 

control it.

Socio-Economic Impact Total 30

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √
1496

Unknown U

 No indication of this was found.

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1 √

Not significantly 0 

Unknown U

 Pistia stratiotes is sold in the ornamental trade.

 The ethanol yield per unit biomass from water lettuce was comparable to those from other agricultural wastes. 

It was concluded that aquatic plants are a promising biomass for ethanol production when the fermentation 

process is fully optimized (Mishima et al. 2008).

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 √

Not significantly 0

Unknown U

 This species is planted in water gardens.

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 Pistia stratiotes is commonly used in Ayurvedic medicine (diuretic, antidiabetic, antidermatophytic, antifungal, 

and antimicrobial properties).

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1 √

Not significantly 0 

Unknown U 
1497

 Pistia stratiotes is a potential candidate for the removal of Zn, Cr, Cu, Cd, Pb, Ag, and Hg. The plant could be 

used to treat water containing low concentrations of these elements (Odjegba and Fasidi 2004).

 Pistia stratiotes could be used to remediate runoff (which often contains soluble nitrates and phosphates and 

heavy metal trace elements) from nursery and greenhouse operations (Sridhar and Sharma 1980, Polomski et 

al. 2009).

B6) Does the species have a positive ecological effect outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 No additional positive effects were found.

Beneficial Effect Total 4

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1498

Scientific Name: Stratiotes aloides

Linnaeus

Common Name: Water Soldier, Water Pineapple

Synonyms:

Section A: Potential for Introduction

INTRODUCTION POTENTIAL RESULTS

Dispersal: High

Hitchhiking/fouling: High

Unauthorized intentional release: Low

Stocking/planting/escape from recreational culture: High

Escape from commercial culture: Unlikely

Transoceanic shipping: Unlikely

Stratiotes aloides has a high probability of introduction to the Great Lakes (Confidence level: High).

Potential pathway(s) of introduction: Dispersal, Hitchhiking/Fouling, Stocking/Planting/Escape from 

Recreational Culture

Stratiotes aloides was listed by the Great Lakes Governors and the Premiers of Ontario and Québec as a 

“least wanted” aquatic invasive species in the Great Lakes. Water soldier crowds out native vegetation 

resulting in decreased plant biodiversity. Dense floating mats hinder boating, angling and swimming, and 

sharp serrated leaf edges can cut swimmers.

POTENTIAL INTRODUCTION VIA DISPERSAL

1a) Does this species occur near waters (natural or artificial) connected to the Great Lakes basin* (e.g., 

streams, ponds, canals, or wetlands)? (*Great Lakes basin = below the ordinary high water mark, including connecting 

channels, wetlands, and waters ordinarily attached to the Lakes)

Yes, this species occurs near waters connected to the Great Lakes basin and is mobile or 

able to be transported by wind or water.

100 √

No, this species does not occur near waters connected to the Great Lakes basin and/or is 

not mobile or able to be transported by wind or water.

0 

Unknown U

 This species occurs in the Trent River, Ontario, with a population of over 22,000 plants (Campbell 2009).

1b) What is the proximity of this species to the Great Lakes basin?
1499

This species occurs in waters within 20 kilometers of the Great Lakes basin, and no barrier 

(e.g., electric barrier, dam) to dispersal is present.

Score x 1 √

This species occurs in waters within 20 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked; or, this species occurs in waters within 100 kilometers of the Great 

Lakes basin, and no barrier to dispersal is present.

Score x 0.75

This species occurs in waters within 100 kilometers of the Great Lakes basin, but dispersal 

to the basin is blocked.

Score x 0.5

This species occurs in waters >100 kilometers from the Great Lakes basin. Score x 0.25

Unknown U

 This species occurs at 44.382919 N, 77.840845 W, in the Trent River near Nappan Island, Ontario (OMNR 

2013).

POTENTIAL INTRODUCTION VIA HITCHHIKING/FOULING

2a) Is this species likely to attach to or be otherwise transported by, or along with, recreational gear, 

boats, trailers, fauna (e.g., waterfowl, fish, insects), flora (e.g., aquatic plants), or other objects (e.g., 

packing materials), including as parasites or pathogens, entering the Great Lakes basin?

Yes, this species is known to be able to adhere to certain surfaces or to be transported by 

other organisms entering the Great Lakes basin.

100 √

No, this species is not known to be able to adhere to certain surfaces or to be transported 

by other organisms entering the Great Lakes basin.

0 

Unknown U

 Aquatic macrophytes are commonly found on trailered boats, and the Trent-Severn waterway is a popular 

destination for boaters (thewaterway.ca).

2b) What is the proximity of this species to the Great Lakes basin?

This species occurs in waters within 20 km of the Great Lakes basin. Score x 1 √

This species occurs in waters within 100 km of the Great Lakes basin. Score x 0.5

This species occurs in waters >100 km from the Great Lakes basin. Score x 0.1

Unknown U

 This species occurs at 44.382919 N, 77.840845 W, in the Trent River near Nappan Island, Ontario (OMNR 

2013).

POTENTIAL INTRODUCTION VIA UNAUTHORIZED INTENTIONAL RELEASE

3a) Is this species sold at aquarium/pet/garden stores (“brick & mortar” or online), catalogs, biological 

supply companies, or live markets (e.g., purchased for human consumption, bait, ornamental, ethical, 

educational, or cultural reasons) and as a result may be released into the Great Lakes basin?

Yes, this species is available for purchase. 100 √

No, this species this species is rarely/never sold. 0 

Unknown U

 As of June 2012, this species is only prohibited in Illinois and Minnesota.
1500

 It is commonly used in water ponds/gardens (OMNR 2009)

3b) How easily is this species obtained within the Great Lakes region (states/provinces)?

This species is widely popular, frequently sold, and/or easily obtained within the Great 

Lakes region.

Score x 1

This species is widely popular, and although trade, sale, and/or possession of this species 

is prohibited, it is frequently sold on the black market within the Great Lakes region.

Score x 0.5

This species is not very popular or is not easily obtained within the Great Lakes region. Score x 0.1 

√

Unknown U

 This species was hard to find using online searches, but literature has described it as occurring in 10% of 

Ontario stores (Funnell et al. 2009)

POTENTIAL INTRODUCTION VIA STOCKING/PLANTING OR ESCAPE FROM 

RECREATIONAL CULTURE

4a) Is this species being stocked/planted to natural waters or outdoor water gardens around the Great 

Lakes region?

Yes, this species is being stocked/planted and/or has ornamental, cultural, medicinal, 

environmental (e.g., biocontrol, erosion control), scientific, or recreational value in the 

Great Lakes region.

100 √

No, this species cannot be stocked/planted or there is not enough interest to do so in the 

Great Lakes region.

0 

Unknown U

 The infestation in the Trent River began as an accidental escape (OMNR 2009).

4b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is authorized and/or is occurring directly in the Great Lakes. Score x 1 √

This activity is occurring in Great Lakes tributaries or connecting waters, or within 20 km 

of the Great Lakes basin.

Score x 0.75

This activity is likely to occur within 20 km of the Great Lakes basin because of its 

popularity/value and there are no widespread regulations against stocking/planting.

Score x 0.5

This activity is occurring in waters >20 km from the Great Lakes basin, or despite federal 

or state regulations in more than half the basin (> 5 states/provinces), this activity may 

occur within 20 km of the basin because of the species’ popularity/value.

Score x 0.25

Unknown U

 This species occurs at 44.382919 N, 77.840845 W, in the Trent River near Nappan Island, Ontario (OMNR 

2013).

POTENTIAL INTRODUCTION VIA ESCAPE FROM COMMERCIAL CULTURE

5a) Is this species known to be commercially cultured in or transported through the Great Lakes region?
1501

Yes, this species is being commercially cultured in or transported through the Great Lakes 

region.

100

No, this species is not commercially cultured in or transported through the Great Lakes 

region.

0 √

Unknown U

5b) What is the nature and proximity of this activity to the Great Lakes basin?

This activity is unregulated or minimally regulated and is occurring directly in the Great 

Lakes.

Score x 1

This activity is unregulated or minimally regulated and is occurring in Great Lakes 

tributaries or connecting waters, or within 20 km of the Great Lakes basin.

Score x 0.75

This activity is strictly regulated but occurs directly in the Great Lakes, and/or this activity 

involves transport of live organisms on/across the Great Lakes.

Score x 0.5

This activity is strictly regulated but occurs in Great Lakes tributaries, connecting waters, 

or within 20 km of the Great Lakes basin, and/or this activity involves transport of live 

organisms within 20 km of the Great Lakes basin.

Score x 0.25

This activity occurs >20 km from the Great Lakes basin and typically does not involve 

transport of live organisms closer to the basin.

Score x 0.1

Unknown U

POTENTIAL INTRODUCTION VIA SHIPPING

6a) Is this species likely to be taken up in ballast, and capable of surviving adverse environments (i.e. 

extreme temperatures, absence of light, low oxygen levels) and partial-to-complete ballast water 

exchange/flushing (e.g., is euryhaline, buries in sediment, produces resistant resting stages, has other 

attributes or behaviors facilitating survival under these conditions)?

Yes, this species is able to survive in ballast tank environments for weeks at a time and is 

not substantially impacted by current regulatory requirements (e.g., exchange, flushing).

100

Yes, this species is able to survive in ballast tank environments for weeks at a time, but 

survival is substantially impacted by current regulatory requirements.

80

No, but this species is capable of fouling transoceanic ship structures (e.g., hull, chains, 

chain locker) while in its active or resting stage.

40

No, this species is unlikely to be taken up in ballast, not able to survive adverse 

environments, does not foul transoceanic ship structures, or is unable to survive current 

ballast water regulations.

0 √

Unknown U

6b) Does this species occur in waters from which shipping traffic to the Great Lakes originates?

Yes, and this species has been observed in ballast of or fouling ships entering the Great 

Lakes.

Score x 1

Yes, and this species has been observed in ports that have direct trade connections with 

the Great Lakes (e.g., Baltic Sea).

Score x 0.5
1502

Yes, but this species has neither been observed in ballast/fouling ships entering the Great 

Lakes nor in ports in direct trade with the Great Lakes.

Score x 0.1

No, this species does not occur in waters from which shipping traffic to the Great Lakes 

originates.

Score x 0

Unknown U

Scoring

Points (per vector) Probability for Introduction

80-100 High

40-79 Moderate

1-39 Low

0 Unlikely

# of Unknowns (overall) Confidence Level

0 High

1-2 Moderate

3-5 Low

>5 Very low

Vector Potential Scorecard

 

Vector

Raw 

Points 

Scored

Proximity 

Multiplier

Total 

Points 

Scored

Probability of

Introduction

Dispersal: Natural dispersal through waterbody 

connections or wind 100 x 1 100 High

Hitchhiking/fouling: Transport via 

recreational gear, boats, trailers, mobile fauna, 

stocked/planted organisms, packing materials, 

host organisms, etc. 

100 x 1 100 High

Release: Unauthorized intentional release of 

organisms in trade (e.g., aquaria, water gardens, 

live food)

100 x 0.1 10 Low

Stocking/planting/escape from recreational 

culture: Intentional authorized or unauthorized 

introduction to natural waters in the Great 

Lakes OR Accidental introduction to Great 

Lakes by escape from recreational culture (e.g., 

water gardens)

100 x 1 100 High

Escape from commercial culture: Accidental 

introduction to Great Lakes by escape from 

commercial culture (e.g., aquaculture)

0 x 0 Unlikely

Transoceanic shipping: Ballast (BOB) or noballast-on-board (NOBOB) water 

exchange/discharge, sediment discharge, hull 

fouling

0 x 0 Unlikely

Total Unknowns (U) 0 Confidence Level High
1503

Section B: Potential for Establishment

ESTABLISHMENT POTENTIAL RESULTS

Status: Established in North America, but not the Great Lakes

Stratiotes aloides has a moderate probability of establishment if introduced to the Great Lakes 

(Confidence level: High).

Stratiotes aloides has been described by government agencies as likely to crowd out native vegetation 

(OMNR 2009), though no primary literature exists to support this in introduced habitats. It does form 

"dense, almost monospecific stands" in native habitat (Strzałek and Koperski 2009). Most species in the 

genus produce vegetative fragments and reproduce easily. Stratiotes aloides can overwinter in the Great 

Lakes; the population in Finland overwinters fine in temperatures similar to those experienced in the 

Great Lakes. 

INVASIVE BIOLOGICAL/ECOLOGICAL ATTRIBUTES

1) How would the physiological tolerance of this species (survival in varying temperature, salinity, 

oxygen, and nutrient levels) be described?

This species has broad physiological tolerance. It has been reported to survive in wide 

ranges of temperature (0°C-30°C), salinity (0-16 parts per thousand), oxygen (0-

saturated), AND nutrient (oligotrophic-eutrophic) levels.

9

This species has somewhat broad physiological tolerance. It has been reported to survive 

in a wide range of temperature, salinity, oxygen, OR nutrient levels. Tolerance to other 

factors is narrower, unknown, or unreported.

6

This species has narrow physiological tolerance. It has been reported to survive in limited 

ranges of temperature, salinity, oxygen, and nutrient levels.

3

Unknown U

6

 This species is native from the United Kingdom through to Asia. Specifically, the United Kingdom, Spain, Italy, 

Bulgaria and Siberia (Natural History Museum of London 2013). It ranges as far north as Kittila, Finland 

(Kittila is located at 67°N) (Natural History Museum of London 2013).

 This species is limited to freshwater.

2) How likely is it that any life stage of this species can overwinter in the Great Lakes (survive extremely 

low levels of oxygen, light, and temperature)?

Likely (This species is able to tolerate temperatures under 5°C and oxygen levels ≤0.5 

mg/L)

9

Somewhat likely (This species is able to tolerate some of these conditions OR has adapted 

behaviorally to avoid them)

6

Somewhat unlikely (This species is able to tolerate conditions close to those specified, but 

it is not known as an overwintering species)

3

Unlikely 0
1504

Unknown U

9

 As this species ranges as far north as Kittila, Finland (Kittila is located at 67°N), where the coldest 

temperatures in Finland occur, it will likely overwinter in the Great Lakes as well.

3) If this species is a heterotroph, how would the flexibility of its diet be described?

This species is a dietary generalist with a broad, assorted, AND flexible diet. 9

This species is moderately a dietary generalist with a broad, assorted, OR flexible diet. 6

This species is a dietary specialist with a limited and inflexible diet. 3

This species is an autotroph. 0

Unknown U

0

 This species is an autotroph

4) How likely is this species to outcompete species in the Great Lakes for available resources?

Likely (This species is known to have superior competitive abilities and has a history of 

outcompeting other species, AND/OR available literature predicts it might outcompete 

native species in the Great Lakes)

9

Somewhat likely (This species is known to have superior competitive abilities, but there 

are few reported cases of this species outcompeting another and no predictions regarding 

species in the Great Lakes)

6

Somewhat unlikely (This species has average competitive abilities, and there are no 

reported cases of this species outcompeting another and no predictions regarding species 

in the Great Lakes)

3

Unlikely (This species is known as a poor competitor that thrives only in environments 

with low biodiversity, AND/OR available literature predicts it might be outcompeted by a 

species in the Great Lakes)

0

Unknown U

7

 This species has been described by government agencies as likely to crowd out native vegetation (OMNR 2009), 

though no primary literature exists to support this in introduced habitats. It does form "dense, almost 

monospecific stands" in native habitat (Strzałek and Koperski 2009).

5) How would the fecundity of this species be described relative to other species in the same taxonomic 

Class?

Very high 9

High 6

Moderate 3
1505

Low 0

Unknown U

3

 Most species in the genus produce vegetative fragments.

6) How likely are this species’ reproductive strategy and habits to aid establishment in new environments, 

particularly the Great Lakes (e.g., parthenogenesis/self-crossing, self fertility, vegetative fragmentation)?

Likely (The reproductive strategy or habits of this species are known to aid establishment 

in new environments, AND available literature predicts establishment in the Great Lakes 

based on these attributes)

9

Somewhat likely (The reproductive strategy or habits of this species are known to aid 

establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

6

Somewhat unlikely (The reproductive strategy or habits of this species could potentially 

aid establishment in new environments, but there is no literature available regarding 

establishment in the Great Lakes based on these attributes)

3

Unlikely (The reproductive strategy or habits of this species are not known to aid 

establishment in new environments)

0

Unknown U

9

 This species has vegetative reproduction. Vegetative propagules are formed as axillary buds. When the bottom 

leaves of the rosette decay, these buds are released. On average 4.7 (±0.28 SE) buds are formed per mature 

rosette (n = 83) (Sarneel 2013). Buds have high capacity to disperse over long distances via water (84% of 

propagules re-sprouted, and 92% were still floating after 187 days) (Sarneel 2013). 

 This species has survived and spread in the Great Lakes area (Trent River) for several years.

ENVIRONMENTAL COMPATIBILITY

7) How similar are the climatic conditions (e.g., air temperature, precipitation, seasonality) in the native 

and introduced ranges of this species to those in the Great Lakes region?

Very similar (The climatic conditions are practically identical to those of the Great Lakes 

region)

9

Similar (Many of the climatic conditions are similar to those of the Great Lakes region) 6

Somewhat similar (Few of the climatic conditions are similar to those of the Great Lakes 

region)

3

Not similar 0

Unknown U

9

 This species is native from the United Kingdom through to Asia. Specifically, the United Kingdom, Spain, Italy, 

Bulgaria and Siberia (Natural History Museum of London 2013). It ranges as far north as Kittila, Finland 

(Kittila is located at 67°N) (Natural History Museum of London 2013). Given this broad range, the climatic 

conditions are likely favorable in the Great Lakes.
1506

8) How similar are other abiotic factors that are relevant to the establishment success of this species (e.g., 

pollution, water temperature, salinity, pH, nutrient levels, currents) in the native and introduced ranges to 

those in the Great Lakes?

Very similar (These factors are practically identical to those of the Great Lakes region) 9

Similar (Many of these factors are similar to those of the Great Lakes region) 6

Somewhat similar (Few of these factors are similar to those of the Great Lakes region) 3

Not similar 0

Unknown U

6

 This species usually inhabits shallow stagnant waters, mainly eutrophic and mesotrophic, with substratum of 

mud and organic deposits (Strzałek and Koperski 2009).

9) How abundant are habitats suitable for the survival, development, and reproduction of this species in 

the Great Lakes area (e.g., those with adequate depth, substrate, light, temperature, oxygen)?

Abundant (Suitable habitats can be easily found and readily available) 9

Somewhat abundant (Suitable habitats can be easily found but are in high demand by 

species already present)

6

Somewhat scarce (Suitable habitats can be found occasionally) 3

Scarce (Suitable habitats are rarely found) 0

Unknown U

7

 This species can grow in depths of up to 6.5m (Tarkowska-Kukuryk 2006).

 Stratiotes aloides is found mainly in sheltered bays of larger lakes, backwater ponds, ditches and canals 

(Natural History Museum of London 2013).

 This species usually inhabits shallow stagnant waters, mainly eutrophic and mesotrophic, with substratum of 

mud and organic deposits (Strzałek and Koperski 2009).

10) How likely is this species to adapt to or to benefit from the predicted effects of climate change on the 

Great Lakes freshwater ecosystems (e.g., warmer water temperatures, shorter duration of ice cover, 

altered streamflow patterns, increased salinization)?

Likely (Most of the effects described above make the Great Lakes a better environment 

for establishment and spread of this species OR this species could easily adapt to these 

changes due to its wide environmental tolerances)

9

Somewhat likely (Several of the effects described above could make the Great Lakes a 

better environment for establishment and spread of this species)

6

Somewhat unlikely (Few of the effects described above would make the Great Lakes a 

better environment for establishment and spread of this species)

3

Unlikely (Most of the effects described above would have no effect on establishment and 

spread of this species or would make the environment of the Great Lakes unsuitable)

0
1507

Unknown U

3

 This species overwinters well in very cold climates, so climate change should confer so real advantage.

11) How likely is this species to find an appropriate food source (prey or vegetation in the case of 

predators and herbivores, or sufficient light or nutrients in the case of autotrophs)?

Likely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are highly abundant and/or easily found)

9

Somewhat likely (Some nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is low to 

moderate)

6

Somewhat unlikely (Few nutritive food items—including species in the Great Lakes that 

may be considered potential food items—are abundant and/or search time is moderate to 

high)

3

Unlikely (All possible nutritive food items—including species in the Great Lakes that may 

be considered potential food items—are relatively scarce and/or search time is high)

0

Unknown U

9

 This species survives in temperature climate, so sunlight in Great Lakes should be sufficient.

12) Does this species require another species for critical stages in its life cycle such as growth (e.g., root 

symbionts), reproduction (e.g., pollinators, egg incubators), spread (e.g., seed dispersers), or transmission 

(e.g., vectors)?

Yes, and the critical species (or one that may provide a similar function) is common in the 

Great Lakes and can be easily found in environments suitable for the species being 

assessed;

OR,

No, there is no critical species required by the species being assessed

9

Yes, and the critical species (or one that may provide a similar function) is moderately 

abundant and relatively easily found in particular parts of the Great Lakes

6

Yes, and the critical species (or one that may provide a similar function) is relatively rare 

in the Great Lakes AND/OR can only be found occasionally in environments suitable for 

the species being assessed

3

Yes, and the critical species (or one that may provide a similar function) is not present in 

the Great Lakes but is likely to be introduced

0

Yes, but the critical species (or one that may provide a similar function) is not present in 

the Great Lakes and is not likely to be introduced

-80% total 

points (at 

end)

Unknown U

9
1508

13) How likely is the establishment of this species to be aided by the establishment and spread of another 

species already in the Great Lakes?

Likely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species—a major host, food item, pollinator—has already established and spread in 

the Great Lakes, AND available literature predicts this previous invader might promote 

the establishment of this species, AND/OR there have been cases reported of this species 

aiding the establishment of this species in other areas)

9

Somewhat likely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

and spread in the Great Lakes)

6

Somewhat unlikely (A non-indigenous species to the Great Lakes that facilitates the 

development of this species—a major host, food item, pollinator—has already established 

in the Great Lakes BUT it is still confined to a small area of the Lakes and the likelihood 

of encounter with this species assessed is hard to predict)

3

Unlikely (A non-indigenous species to the Great Lakes that facilitates the development of 

this species has not been established in the Great Lakes)

0

Unknown U

0

14) How likely is establishment of this species to be prevented by the herbivory, predation, or parasitism 

of a natural enemy this is already present in the Great Lakes and may preferentially target this species?

Likely (The ability of the natural enemy to prevent the establishment of this species in 

introduced ranges or limiting populations of this species in native ranges is well 

documented in the literature AND this natural enemy is abundant and widespread in the 

Great Lakes)

-80% total 

points (at 

end)

Somewhat likely (The ability of the natural enemy to prevent the establishment of this 

species in introduced ranges or limiting populations of this species in native ranges is 

suggested in the literature OR this natural enemy has limited distribution in the Great 

Lakes)

-60% total 

points (at 

end)

Somewhat unlikely (There are few cases reported of such a natural enemy preventing the 

establishment of this species in introduced ranges or limiting populations of this species in 

native ranges OR this natural enemy has low abundance in the Great Lakes)

-10% total 

points (at 

end)

Unlikely (Such a natural enemy is particularly rare or is not present in the Great Lakes) 0

Unknown U

0

PROPAGULE PRESSURE

15) On average, how large and frequent are inoculations (introduction events) from the potential vectors 

identified in Section A for this species? (What is the total number of individuals introduced?)

Frequent, large inocula 9
1509

Frequent, moderate inocula 6

Frequent, small inocula OR infrequent, large inocula 3

Infrequent, small or moderate inocula 0

Unknown U

0

 Release or escape from recreational culture is generally infrequent, and would likely be limited to a few plants.

HISTORY OF INVASION AND SPREAD

16) How extensively has this species established reproducing populations in areas outside its native range 

as a direct or indirect result of human activities?

Very extensively (many invasive populations of this species have been reported in areas 

widely distributed from the native range)

9

Extensively (some invasive populations of this species have been reported in areas widely 

distributed from the native range)

6

Somewhat extensively (few invasive populations of this species have been reported in 

areas widely distributed from the native range OR all invasive populations are in close 

proximity to each other)

3

Not extensively (no invasive populations of this species have been reported) 0

Unknown U

1

 The only invasive population reported has been in Ontario.

17) How rapidly has this species spread by natural means or by human activities once introduced to other 

locations?

Rapidly (This species has a history of rapid spread in introduced ranges) 9

Somewhat rapidly (This species has a history of moderately rapid spread in introduced 

ranges)

6

Somewhat slowly (This species has a history of moderately slow spread in its introduced 

ranges)

3

Slowly (This species has a history of slow to no spread in its introduced ranges) 0

Unknown U

6

 What would have likely started from a few plants has grown to 22,000 plants in seven populations.

18) Are there any existing control measures in the Great Lakes set to prevent the establishment and/or 

spread of this species?

Yes, and they are likely to prevent establishment or spread of the species. (There are no 

reported cases of this species adapting or avoiding current measures. These measures are 

highly effective in preventing the establishment and spread of this species)

-90% total 

points (at 

end)
1510

Yes, and they are moderately likely to prevent establishment or spread of the species. 

(There are few reported cases of this species adapting or avoiding current measures used 

to control its establishment and spread)

-50% total 

points (at 

end)

Yes, but they are unlikely to prevent establishment or spread of the species. (There are 

many reported cases of this species adapting or avoiding current measures used to control 

its establishment and spread)

-20% total 

points (at 

end)

No control methods have been set to prevent the establishment and/or spread of this 

species

0

Unknown U

0

Establishment Potential Scorecard

Points Probability 

for 

Establishment

A. Total Points (pre-adjustment) 84

>100 High Adjustments

B. Critical species A*(1- 0%) 84

51-99 Moderate C. Natural enemy B*(1- 0%) 84

Control measures C*(1- 0%) 84

0-50 Low Potential for Establishment Moderate

# of questions 

answered as 

“unable to 

determine”

Confidence 

Level

0-1 High

Total # of questions unknown 0

2-5 Moderate 

6-9 Low

Confidence Level High

>9 Very low

Section C: Potential for Impact

IMPACT POTENTIAL RESULTS

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Low

Stratiotes aloides has the potential for moderate environmental impact if introduced to the Great 

Lakes.
1511

Stratiotes aloides forms "dense, almost monospecific stands" in native habitat (Strzałek and Koperski 

2009) and has the potential to crowd out native vegetation (OMNR 2009).

Stratiotes aloides has the potential to alter surrounding water chemistry, which may harm phytoplankton 

and other aquatic organisms (OMNR 2009). The exact mechanism has not been elucidated, but the likely 

cause is allelopathy (Mulderij et al. 2006). 

Stratiotes aloides has the potential for moderate socio-economic impact if introduced to the Great 

Lakes.

Stratiotes aloides’s sharp leaves can cut skin (Campbell 2009). Dense floating mats of water soldier can 

hinder recreational activities, such as boating, angling, and swimming. This would likely result from a 

massive infestation, but has not been quantified.

There is little or no evidence to support that Stratiotes aloides has the potential for significant 

beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Stratiotes aloides can be used for the control of other organisms or 

improving water quality. There is no evidence to suggest that this species is commercially, recreationally, 

or medically valuable. It does not have significant positive ecological impacts.

POTENTIAL ENVIRONMENTAL IMPACT

NOTE: In this section, a “Not significantly” response should be selected if the species has been studied 

but there have been no reports of a particular impact. An “Unknown” response is appropriate if the 

species is poorly studied.

E1) Does the species pose some hazard or threat to the health of native species (e.g., it magnifies toxin 

levels; is poisonous; is a pathogen, parasite, or a vector of either)? 

Yes, and it has impacted threatened/endangered species, resulted in the reduction or 

extinction of one or more native populations, affects multiple species, or is a reportable 

disease

6

Yes, but negative consequences have been small (e.g., limited number of infected 

individuals, limited pathogen transmissibility, mild effects on populations and 

ecosystems)

1 √

Not significantly 0

Unknown U

 Density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between rosettes, 

both in surveys, in situ field experiments and laboratory microcosm experiments (Mulderij et al. 2006). Surveys 

showed cell density between rosettes at about 25% compared to outside rosettes. In site experiments showed 

chlorophyll concentrate at about 60% between rosettes at about 25% compared to outside rosettes. This study 

concluded that allelopathic substances are excreted by S. aloides. The negative effect may be amplified in 

natural environments due to other stresses such as shading and grazing.

 Mulderij et al. (2005) showed the effect on several phytoplankton species: two cyanobacterial strains (toxic and 

non-toxic (Microcystis aeruginosa), one green alga (Scenedesmus obliquus) and one eustigmatophyte 

(Nannochloropsis limnetica). The overall effect (8-51%) was measured by the extendsion in doubling time of 

initial biovolume.

E2) Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?
1512

Yes, and it has resulted in significant adverse effects (e.g., impacted threatened/endangered 

species or caused critical reduction, extinction, behavioral changes including modified 

spawning behavior) on one or more native populations

6 

Yes, and it has caused some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

1 √

Not significantly 0

Unknown U

 This species has formed dense colonies of large number (22,000 plants in seven colonies) in Trent River, 

Ontario (Campbell 2009).

 This species has been described by government agencies as likely to crowd out native vegetation (OMNR 2009), 

though no primary literature exists to support this in introduced habitats. It does form "dense, almost 

monospecific stands" in native habitat (Strzałek and Koperski 2009).

E3) Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 

(e.g., impacted threatened/endangered species, caused significant reduction or extinction of 

one or more native populations, creation of a dead end or any other significant alteration in 

the food web)

6

Yes, and it has resulted in some noticeable stress to (e.g., decrease in growth, survival, 

fecundity) or decline of at least one native population

AND/OR

Yes, and it has resulted in some alteration of the food web structure or processes, the 

effects of which have not been widespread or severe

1 

Not significantly 0 √

Unknown U 

E4) Has it affected any native populations genetically (e.g., through hybridization, selective pressure, 

introgression)?

Yes, and it has caused a loss or alteration of genes that may be irreversible or has led to the 

decline of one or more native species (or added pressure to threatened/endangered species)

6

Yes, some genetic effects have been observed, but consequences have been limited to the 

individual level

1 

Not significantly 0 √

Unknown U

E5) Does it negatively affect water quality (e.g., increased turbidity or clarity, altered nutrient, oxygen, or 

other chemical levels/cycles)?

Yes, and it has had a widespread, long-term, or severe negative effect on water quality

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected water quality to some extent, but the alterations and resulting adverse 

effects have been limited or inconsistent (as compared with above statement)

1 √
1513

Not significantly 0 

Unknown U

 Has the potential to alter surrounding water chemistry, which may harm phytoplankton and other aquatic 

organisms (OMNR 2009). The exact mechanism has not been elucidated, but the likely cause is allelopathy 

(Mulderij et al. 2006). Other potential explanations follow.

 Density of phytoplankton (except cyanobacteria) was always higher outside S. aloides than between rosettes, 

both in surveys, in situ field experiments and laboratory microcosm experiments (Mulderij et al. 2006). Surveys 

showed cell density between rosettes at about 25% compared to outside rosettes. In site experiments showed 

chlorophyll concentrate at about 60% between rosettes at about 25% compared to outside rosettes. This study 

concluded that allelopathic substances are excreted by S. aloides. The negative effect may be amplified in 

natural environments due to other stresses such as shading and grazing.

 Mulderij et al. (2005) showed the effect on several phytoplankton species: two cyanobacterial strains (toxic and 

non-toxic (Microcystis aeruginosa), one green alga (Scenedesmus obliquus) and one eustigmatophyte 

(Nannochloropsis limnetica). The overall effect (8-51%) was measured by the extendsion in doubling time of 

initial biovolume.

 S. aloides exerted a negative influence upon contiguous populations of phytoplankton in Sweden and in Poland. 

A considerable decline in planktonic chlorophyll was accompanied by decreases in electrolytic conductivity, 

carbonate alkalinity and contents of calcium, potassium and sodium. Low concentrations of molybdate-reactive 

phosphorus in the water of the Stratiotes community was credited to co-precipitation with calcium carbonate on 

the leaf surfaces of the submerged plants. Thus, rather than allelopathy, competition for essential nutrients 

together with changes in the ionic composition of the water seemed to be a more likely explanation for the 

decline in phytoplankton (Brammer 1979).

 Inhibition may also occur through inhibition of the enzyme alkaline phosphatase, which is associated with the 

growth of phytoplankton (Addisie and Medellin 2012).

E6) Does it alter physical components of the ecosystem in some way (e.g., facilitated erosion/siltation, 

altered hydrology, altered macrophyte/phytoplankton communities, physical or chemical changes to 

substrate)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical 

ecosystem

AND/OR

Yes, and it has resulted in significant negative consequences for at least one native species

6

Yes, it has affected the physical ecosystem to some extent, but the alterations and resulting 

adverse effects have been mild

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 3

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
1514

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1

POTENTIAL SOCIO-ECONOMIC IMPACT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular impact. An “Unknown” response is appropriate if the potential for a particular impact might 

be inferred from a significant environmental impact but has not been explicitly reported or if there is an 

unresolved debate about a particular impact.

S1) Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is 

poisonous, a virus, bacteria, parasite, or a vector of one)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1 √

Not significantly 0 

Unknown U

 Sharp leaves of this species can cut skin (Campbell 2009).

S2) Does it cause damage to infrastructure (e.g., water intakes, pipes, or any other industrial or 

recreational infrastructure)?

Yes, it is known to cause significant damage 6

Yes, but the costs have been small and are largely reparable or preventable 1

Not significantly 0 √

Unknown U

S3) Does it negatively affect water quality (i.e. in terms of being less suitable for human use)?

Yes, it has significantly affected water quality, and is costly or difficult to reverse 6

Yes, but the effects are negligible and/or easily reversed 1

Not significantly 0 √

Unknown U

S4) Does it negatively affect any markets or economic sectors (e.g., commercial fisheries, aquaculture, 

agriculture)?

Yes, it has caused significant damage to one or more markets or economic sectors 6

Some damage to markets or sectors has been observed, but negative consequences have 

been small

1 
1515

Not significantly 0 √

Unknown U

S5) Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, 

equipment damage, decline of recreational species)?

Yes, it has caused widespread, frequent, or otherwise expensive inhibition of recreation and 

tourism 

6

Yes, but negative consequences have been small 1 √

Not significantly 0

Unknown U

 Dense floating mats of water soldier can hinder recreational activities, such as boating, angling and swimming.

S6) Does it diminish the perceived aesthetic or natural value of the areas it inhabits?

Yes, the species has received significant attention from the media/public, significantly 

diminished the natural or cultural character of the area, or significantly reduced the area’s 

value for future generations

6

Yes, but negative consequences have been small 1 

Not significantly 0 

Unknown U √

 This would likely result from a massive infestation, but has not been quantified.

Socio-Economic Impact Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1516

POTENTIAL BENEFICIAL EFFECT

NOTE: In this section, a “Not significantly” response should be selected if there have been no reports of 

a particular effect. An “Unknown” response is appropriate if the potential for a particular effect might be 

inferred but has not been explicitly reported or if there is an unresolved debate about a particular effect.

B1) Does it act as a biological control agent for aquatic weeds or other harmful nonindigenous 

organisms?

Yes, it has succeeded significantly as a control agent 6 

Yes, it has had some success as a control agent, but may be inconsistent or lack a desired 

level of effectiveness

1 

Not significantly 0 √

Unknown U

B2) Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade)? 

Yes, it is economically important to at least one of these industries 6

Yes, but its economic contribution is small 1

Not significantly 0 √

Unknown U

B3) Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal 

activity)?

Yes, it is commonly employed recreationally and has some perceived value for local 

communities and/or tourism

6

It is sometimes employed recreationally, but adds little value to local communities or 

tourism 

1 

Not significantly 0 √

Unknown U

B4) Does the species have some medicinal or research value (i.e. outside of research geared towards its 

control)?

Yes, it has significant medicinal or research value 6

It has some medicinal or research value, but is not of high priority

OR

It is potentially important to medicine or research and is currently being or scheduled to be 

studied

1 √

Not significantly 0 

Unknown U

 The herb has had a high reputation for treating wounds, especially when these are made by an iron implement. 

It is applied externally. The plant is also said to be of use in the treatment of St. Anthony's Fire and also of 

bruised kidneys (Grieve 1984).
1517

B5) Does the species remove toxins or pollutants from the water or otherwise increase water quality?

Yes, it reduces water treatment costs or has a significant positive impact for the health of 

humans and/or native species

6

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

B6) Does the species have a positive ecological impact outside of biological control (e.g., increases the 

growth or reproduction rates of other species, fills an important gap in the food web, supports the survival 

of a species that is threatened, endangered species, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

 It protects larvae of an endangered dragonfly in native habitat (Rantala et al. 2004), but this is not a concern in 

the Great Lakes.

Beneficial Effect Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low

1 0

0 ≥2

Unknown

1 ≥1
1518

APPENDIX B: Literature Cited in Assessments

Aadland, L.P., and A. Kuitunen. Habitat suitability criteria for stream fishes and mussels of Minnesota. 

Minnesota Ecological Services Division, Minnesota Department of Natural Resources 11: 16-25 (2004).

Abdel-Fattah, S. Aquatic invasive species early detection and rapid response–assessment of chemical 

response tools. Prepared for the IJC Work Group on Aquatic Invasive Species Rapid Response 104 pp. 

(2011).

Abdoli, A., S. Allahyari, R. Patimar, and B.H. Kiabi. Feeding strategies of three Neogobius species in the 

Gomishan Wetland of Iran, South-east Caspian Sea. Zoology in the Middle East 56: 49-54 (2012).

Abdolmalaki, S., and I. Psuty. The effects of stock enhancement of Pikeperch (Sander lucioperca) in 

Iranian coastal waters of the Caspian Sea. ICES Journal of Marine Science, Journal du Conseil 64: 973-

980 (2007).

Abdullayev, M.A., B. Khakberdiyev, and D. Urchinov. Biology of the European Catfish (Silurus glanis) 

from lakes in the lower reaches of the Zarafshan River and Khorezm Province. Journal of Ichthyology 17: 

487-491 (1978).

Able, K.W., and S.M. Hagan. Effects of Common Reed (Phragmites australis) invasion on marsh surface 

macrofauna: response of fishes and decapod crustaceans. Estuaries 23: 633-646 (2000).

Adamek, Z., and I. Sukop. Vliv strevlicky vychodni (Pseudorasbora parva) na parametry rybnicniho 

prosteredi. Biodiverzita Ichtiofauncy CR 3: 37-43 (2000).

Addisie, Y., and A.C. Medellin. Allelopathy in aquatic macrophytes: effects on growth and physiology of 

phytoplanktons. African Journal of Plant Science 6(10): 270-276 (2012).

Ahne, W., and I. Thomsen. Isolation of Pike fry rhabdovirus from Pseudorasbora parva (Temminck and 

Schlegel). Journal of Fish Diseases 9 (6): 555-556 (1986).

Ahnelt, H., P. Bănărescu, R. Spolwind, A. Harka, and H. Waidbacher. Occurrence and distribution of 

three gobiid species (Pisces: Gobiidae) in the middle and upper Danube region – example of different 

dispersal patterns? Biológia (Bratislava) 53: 661-674 (1998).

Ahnelt, H., M. Duchkowitsch, G. Scattolin, I. Zweimüller, and A. Weissenbacher. Neogobius 

gymnotrachelus (Kessler, 1857) (Teleostei: Gobiidae) die Nackthals-Grundel in Österreichs. Österreichs 

Fischerei 54: 262-266 (2001).

Aiken, S.G. A conspectus of Myriophyllum (Haloragaceae) in North America. Brittonia 33: 57-69 

(1981).

Aker, W.G., X. Hu, P. Wang, and H.M. Hwang. Comparing the relative toxicity of malathion and 

malaoxon in Blue Catfish Ictalurus furcatus. Environmental Toxicology 23(4): 548-554 (2008).

Aladin, N.V. The conservation ecology of the Podonidae from the Caspian and Aral seas. Hydrobiologia 

307: 85-97 (1995).
1519

Aladin, N.V., and W.T.W. Potts. Changes in the Aral Sea ecosystems during the period 1960–1990. 

Hydrobiologia 237: 67-79 (1992).

Aladin, N.V., and W.T.W. Potts. The osmoregulatory capacity of the Cladocera. Journal of Comparative 

Physiological B-Biochemical Systemic and Environmental Physiology 164: 671-683 (1995).

Aladin, N.V., Plotnikov, I.S., and R. Letolle. Hydrobiology of the Aral Sea. Dying and Dead Seas 

Climatic Versus Anthropic Causes. Springer Netherlands 125-157 pp. (2004).

Aladin, N, I. Plotnikov, T. Ballatore, and P. Micklin. Biodiversity loss in a saline lake ecosystem. Effects 

of introduced species and salinization in the Aral Sea. Japanese International Cooperation Agency 4-

12pp. (2008a).

Aladin, N., P. Micklin, and I. Plotnikov. Biodiversity of the Aral Sea and its importance to the possible 

ways of rehabilitating and conserving its remnant water bodies. Qi, J., and K.T. Evered (eds.). 

Environmental problems of Central Asia and their economic, social and security impacts. Springer 

Science 73-98 pp. (2008b). 

Alaska Department of Fish and Game. Chum Salmon (Oncorhynchus keta) (2015). 

http://www.adfg.alaska.gov/index.cfm?adfg=ChumSalmon.main

Albaina, A., F. Villate, and I. Uriarte. Zooplankton communities in two contrasting Basque estuaries 

(1999-2001): Reporting changes associated with ecosystem health. Journal of Plankton Research 31:739-

752 (2009).

Alexandrov, B., A. Boltachev, T. Kharchenko, A. Lyashenko, M. Son, P. Tsarenko, and V. Zhukinsky. 

Trends of aquatic alien species invasions in Ukraine. Aquatic Invasions 2 (3): 215-242 (2007).

Ali, M.A., R.A. Ryder, and M. Anctil. Photoreceptors and visual pigments as related to behavioralresponses and preferred habitats of perches (Perca spp.) and pikeperches (Stizostedion spp.). Journal of 

Fisheries Research Board of Canada 34: 1475-1480 (1977).

Aliotta, G., P. Monaco, G. Pinto, A. Pollio, and L. Previtera. Potential allelochemicals fromPistia 

stratiotes L. Journal of Chemical Ecology 17: 2223-2234 (1991).

Allen, K.R. The food and migrations of the perch in Windermere. Journal of Animal Ecology 4: 264-273 

(1935).

Allen, U.S., and F. Gherardi. Cherax destructor. Centre for Agricultural Bioscience International (CABI) 

(2011). http://www.cabi.org/isc/datasheet/89134

Almeida, D., P.V. Stefanoudis, D.H. Fletcher, C. Rangel, and E. da Silva. Population traits of invasive 

bleak Alburnus alburnus between different habitats in Iberian fresh waters. Limnologica 46: 70-76 

(2014).

Almujaddade Alfasane, M.D., M. Khondker, M.D. Shafiqul Islam, and M. Azmal Hossain Bhuiyan. 

Egeria densa planchon (Hydrocharitaceae): a new angiospermic record for Bangladesh. Bangladesh 

Journal of Plant Taxonomy 17 (2): 209-213 (2010).
1520

Alp, A., C. Kara, F. Üçkardeş, J. Carol, and E. García-Berthou. 2011. Age and growth of the European 

Catfish (Silurus glanis) in a Turkish Reservoir and comparison with introduced populations. Reviews in 

Fish Biology and Fisheries 21 (2): 283-294 (2011).

Altun, Ö. Morphological variations observed on the Sand Smelt (Atherina boyeri Risso, 1810) 

populations. Turk J Zool 23 (3): 911–918 (1999).

Amundsen, P., A. Siwertsson, R. Primmicerio, and B. Thomas. Long-term responses of zooplankton to 

invasion by planktivorous fish in a subarctic watercourse. Freshwater Biology 54: 24-34 (2009).

Anders, K., and H. Möller. Food-induced granulomatosis in European Smelt, Osmerus eperlanus. 

Canadian Journal of Fisheries and Aquatic Sciences 44:1848-1854 (1987).

Anderson, R.O. A case for Zander: fish for the future? Brainerd, M.N. (ed.). The In-Fisherman Walleye 

Guide 1992. 22-32 pp. (1992).

Andersson, G., H. Berggren, G. Cronberg, and C. Gelin. Effects of planktivorous and benthivorous fish 

on organisms and water chemistry in eutrophic lakes. Hydrobiologia 59: 9-15 (1978).

Anderson, C.L., E.U. Canning, and B. Okamura. Molecular data implicate bryozoans as hosts for PKX 

(Phylum Myxozoa) and identify a clade of bryozoan parasites within the Myxozoa. Parasitology 119: 

555-561 (1999).

Anderson, J., D. Jensen, J. Gunderson, and M. Zhulkov. A field guide to fish invaders of the Great Lakes 

region. University of Minnesota Sea Grant Program, Duluth, MN. USA (2008). 

http://files.dnr.state.mn.us/eco/invasives/fish_guide_final.pdf

Angonesi, L.G., N.G. da Rosa, and C.E. Berrivenuti. Tolerance to salinities shocks of the invasive mussel 

Limnoperma fortunei under experimental conditions. Iheringia Série Zoologia 98: 66-69 (2008).

Ankney, M. Occurrence and persistence of Water Hyacinth (Eichhornia crassipes) in Michigan 2011-

2012. Michigan Department of Natural Resources (2012). 

http://www.michigan.gov/documents/dnr/Water_Hyacinth_in_Michigan_Final_12-6-12_405850_7.pdf

Accessed 7 June 2013

Aohagi, Y., T. Shibahara, N. Machida, Y. Yamaga, and K. Kagota. Clinostomum complanatum

(Trematoda, Clinostomatidae) in 5 new fish hosts in Japan. Journal of Wildlife Diseases 28: 467-469 

(1992).

Applegate, R.L. The use of a bryozoan, Fredericella sultana, as food by sunfish in Bull Shoals Reservoir. 

Limnology and Oceanography 11: 129-130 (1966).

Araújo, F.G., R.G. Bailey, and W.P. Williams. 1999. Spatial and temporal variations in fish populations 

in the upper Thames estuary. Journal of Fish Biology 55: 836-853 (1999).

Aquatic Control. Griffy Lake aquatic vegetation management plan update-draft: Monroe County, Indiana. 

Prepared for Indiana Department of Natural Resources (2008). 

https://bloomington.in.gov/media/media/application/pdf/4395.pdf

Arbačiauskas, K. Ponto-Caspian amphipods and mysids in the inland waters of Lithuania: history of 

introduction, current distribution and relations with native malacostracans. Leppäkoski, E., S. Gollasch, 
1521

and S. Olenin (eds). Invasive aquatic species of Europe-distribution, impacts and management. Kluwer 

Academic Publishers, Dordrecht, Boston, London 104-115 pp. (2002). 

Arbačiauskas, K. The distribution and local dispersal of Ponto-Caspian Peracarida in Lithuanian fresh 

waters with nots on Pontogammarus robustoides population establishment, abundance and impact. 

Oceanological and Hydrobiological Studies 34 (Supplement 1): 93-111 (2005).

Arbačiauskas, K., and S. Gumuliauskaité. Chapter twenty-five: Invasion of the Baltic Sea basin by the 

Ponto-Caspian amphipod Pontogammarus robustoides and its ecological impact. Gherardi, F. (ed.). 

Biological invaders in inland waters: Profiles, distribution, and threats. Springer 463-477 pp. (2007).

Arbačiauskas, K., V. Rakauskas, and T. Virbickas. Initial and long-term consequences of attempts to 

improve fish-food resources in Lithuanian waters by introducing alien peracaridan species: A 

retrospective overview. Journal of Applied Ichthyology 26 (Suppl.2): 28-37 (2010). 

Arend, K.K., D. Beletsky, J.V. DePinto, S.A. Ludsin, J.J. Roberts, D.K. Rucinski, D. Scavia, D.J. 

Schwab, and T.O. Höök. Seasonal and interannual effects of hypoxia on fish habitat quality in central 

Lake Erie. Freshwater Biology 56: 366-382 (2011). 

Argillier, C., M. Barral, and P. Irz. Growth and diet of the Pikeperch Sander lucioperca (L.) in two 

French reservoirs. Archives of Polish Fisheries (2012).

Armsby, M., and N. Tisch. Intraguild predation and cannibalism in a size-structured community of marine 

amphipods. Journal of Experimental Marine Biology and Ecology 333: 286-295 (2006).

Arntzen, E.V. Temperature and water depth monitoring within Chum Salmon spawning habitat below 

Bonneville Dam. Report PNNL-18561. Pacific Northwest National Laboratory, Richland, Washington. 19 

pp. (2009).

Arroyo, N.L., K. Aarnio, and E. Bonsdorff. Drifting algae as a means of re-colonizing defaunated 

sediments in the Baltic Sea: A short-term microcosm study. Hydrobiologia 554: 83-95 (2006).

Arthington, A.H., and F. McKenzie. Review of impacts of displaced/introduced fauna associated with 

inland waters. Australia: State of the Environment Technical Paper Series (Inland waters), Department of 

the Environment, Canberra (Australia), 69 pp. (1997).

Aseinova, A.A. Clupeonella cultriventris caspia. Caspian Sea Biodiversity Database, Caspian 

Environment Programme, Baku, Azerbaijan (2003). 

Attionu, R. H. Some effects of Water Lettuce (Pistia stratiotes, L.) on its habitat. Hydrobiologia 50: 245-

254 (1976).

Audicana, M.T., and M.W. Kennedy. Anisakis simplex: from obscure infectious worm to inducer of 

immune hypersensitivity. Clinical Microbiology Reviews 21: 360-379 (2008).

Audzijonytė, A., and R. Väinölä. Diversity and distributions of circumpolar fresh-and brackish-water 

Mysis (Crustacea: Mysida): descriptions of M. relicta Lovén, 1862, M. salemaai n. sp., M. segerstralei n. 

sp. and M. diluviana n. sp., based on molecular and morphological characters. Hydrobiologia 544 (1): 89-

141 (2005).
1522

Audzijonytė, A., M. Daneliya, R. Väinölä. Comparative phylogeography of Ponto-Caspian mysid 

crustaceans: isolation and exchange among dynamic inland sea basins. Molecular Ecology 15: 2969-2984 

(2006).

Audzijonytė, A., K.J. Wittmann, I. Ovcarenko, and R. Väinölä. Invasion phylogeography of the Ponto‐

Caspian crustacean Limnomysis benedeni dispersing across Europe. Diversity and Distributions 15 (2): 

346-355 (2009).

Austin, B., and D.J. Alderman. Bacterial shell disease of crustaceans. Identification leaflets for diseases 

and parasites of fish and shellfish 1-4 (1987).

Azizova, N.A. The possibility of a goby fishery in the Caspian. Rybnoye Khozaystvo 3(14) (1962).

Azumaya, Y., and Y. Ishida. Mechanism of body cavity temperature regulation of Chum Salmon 

(Oncorhynchus keta) during homing migration in the North Pacific Ocean. Fisheries Oceanography 14 

(2): 81-96 (2005).

Bacela, K., and A. Konopacka. The life history of Pontogammarus robustoides, an alien amphipoid 

species in Polish waters. Journal of Crustacean Biology 25 (2): 190-195 (2005).

Bacela, K., A. Konopacka, and M. Grabowski. Reproductive biology of Dikerogammarus haemobaphes: 

an invasive gammarid (Crustacea: Amphipoda) colonizing running waters in Central Europe. Biological 

Invasions 11 (9): 2055-2066 (2009).

Bacela-Spychalska, K., R.A. Wattier, C. Genton, and T. Rigaud. Microsporidian disease of the invasive 

amphipod Dikerogammarus villosus and the potential for its transfer to local invertebrate fauna. 

Biological Invasions 14:1831-1842 (2012).

Bacescu, M. Les Mysidacés des eaux Roumaines: Étude taxonomique, morphologique, biogéographique 

et biologique. Annales scientifiques de l'Université de Jassy 26: 453-804 (1940).

Bacescu, M. Mysidacea. Crustacea. Fauna Republicii Populare Romîne 4 (3): 1-126 (1954).

Bacevičius, E., and Z.R. Gasiūnaitė. Two crab species- Chinese Mitten Crab (Eriocheir sinensis Edw.) 

and Mud Crab (Rhithropanopeus harrisii (Gould) ssp. tridentatus (Maitland) in the Lithuanian coastal 

waters, Baltic Sea. Transitional Waters Bulletin 2: 63-68 (2008).

Baensch, H.A. and R. Riehl. Aquarien atlas. Bd. 3. Melle: Mergus, Velag für Natur- und Heimtierkunde, 

Germany. 1104 pp. (1991).

Baerwaldt, K, A. Benson, and K. Irons. State of the carp: Asian carp distribution in North America. 

United States Army Corps of Engineers. Rock Island, IL. 8 pp. (2013).

Bailey, S.A., I.C. Duggan, C.D.A. van Overdijk, P.T. Jenkins, and H.J. MacIsaac. Viability of 

invertebrate diapausing eggs collected from residual ballast sediment. Limnology and Oceanography 48: 

1701-1710 (2003).

Bailey, S.A., I.C. Duggan, C.D.A. Overdijk, T.H. Johengen, D.F. Reid, and H.J. MacIsaac. Salinity 

tolerance of diapausing eggs of freshwater zooplankton. Freshwater Biology 49: 286-295 (2004).
1523

Bailey, S.A., I.C. Duggan, P.T. Jenkins, and H.J. MacIsaac. Invertebrate resting stages in residual ballast 

sediment of transoceanic ships. Canadian Journal of Fisheries and Aquatic Sciences 62 (5): 1090-1103 

(2005a).

Bailey, S.A., K. Nandakumar, I.C. Duggan, C.D.A. van Overdijk, T.H. Johengen, D.F. Reid, and H.J. 

MacIsaac. In situ hatching of invertebrate diapausing eggs from ships’ ballast sediment. Diversity and 

Distributions 11 (5): 453-460 (2005b).

Bailey, S.A., K. Nandakumar, and H.J. MacIsaac. Does saltwater flushing reduce viability of diapausing 

eggs in ship ballast sediment? Diversity and Distributions 12 (3): 328-335 (2006).

Baimov, U. Data on the biology of the Bubyr Goby Bubyr caucasicus (Berg) in the Aral Sea. Vest. Kav. 

Fil. Akad. Nauk UZ. S.S.R. 3: 51-59 (1963).

Bain, M. Assessing impacts of introduced aquatic species: Grass Carp in large systems. Environmental 

Management 17: 211-224 (1993).

Baker, E., and J. Li. Benthophilus stellatus. USGS Nonindigenous Aquatic Species Database, Gainsville 

FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI

(2015a). 

Baker, E., and J. Li. Phoxinus phoxinus. USGS Nonindigenous Aquatic Species Database, Gainsville FL, 

and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI (2015b). 

Bakkala, R.G. Synopsis of biological data on the Chum Salmon, Oncorhynchus keta (Walbaum) 1792. 

FAO Species Synopsis No. 41. Circular 315. United States Department of the Interior, Washington D.C. 

(1970).

Balciunas, J.K., M.J. Grodowitz, A.F. Cofrancesco, and J.F. Shearer. Hydrilla. In Van Driesche, R., B. 

Blossey, M. Hoddle, S. Lyon, and R. Reardon (eds.). Biological Control of Invasive Plants in the Eastern 

United States Report FHTET-2002-04. United States Department of Agriculture, Forest Service, Forest

Health Technology Enterprise Team, Morgantown, West Virginia (2002).

Balik, S. Bati Anadolu tatlisu baliklari üzerine arastirmalar. Ege. Üniv. Fen. Fak. Ilmi raporlar No: 236-

1979, Ege Üniv. Matbaasi, Izmir, 61 pp. (1979).

Balon, E.K., W.T. Momot, and H.A. Regier. Reproductive guilds of percids: results of the 

paleogeographical history and ecological succession. Journal of the Fisheries Research Board of Canada

34: 1910-1921 (1977). 

Bănărescu, P. Zoogeography of Fresh Waters Vol. 2. Distribution and Dispersal of Freshwater Animals 

in North America and Eurasia. AULA-Verl. Wiesbaden. 1091 pp. (1964).

Bănărescu, P.M. Zoogeography and history of the freshwater fish fauna of Europe. Holcik, J. (ed.) The 

freshwater fishes of Europe. 88-107 pp. (1989).

Bănărescu, P. Zoogeography of Fresh Waters, Vol. 2. Distribution and dispersal of freshwater animals in 

North American and Eurasia. Aula Verlag, Wiesbaden (1991).
1524

Bănărescu, P., and B.W. Coad. Cyprinids of Eurasia. Cyprinid Fishes: Systematics, Biology, and 

Exploitation. Chapman & Hall, London 127-155 pp. (1991).

Bao, M. Prevalence of Clonorchis sinensis infection in market-sold freshwater fishes in Jinzhou city, 

Northeastern China. African Journal of Microbiology Research 6 (3): 629 (2012).

Barbiero, R.P., Little, R.E., and Tuchman, M.L. Results from the U.S. EPA’s biological open water 

surveillance program of the Laurentian Great Lakes: III. Crustacean zooplankton. Journal of Great Lakes 

Research 27 (2): 167-184 (2001). 

Barko, J.W., and R.M. Smart. Comparative influences of light and temperature on growth and metabolism 

of selected submersed freshwater macrophytes. Ecological Monographs 51 (2): 219-235 (1981).

Bartley, D.M. Introduced species in fisheries and aquaculture: information for responsible use and control 

(CD-ROM). Rome, FAO (2006).

Bartuloviç, V., D. Lucic, A. Conides, B. Glamuzina, J. Ducic, D. Hafner, and M. Batistic. Food of sand 

smelt, Atherina boyeri Risso, 1810 (Pisces: Atherinidae) in the estuary of the Mala Neretva River 

(middle-eastern, Adriatic, Croatia). Sci. Mar. 64(4): 597-603 (2004).

Basiouny, F.M., W.T. Haller, and L.A. Garrard. Survival of Hydrilla (Hydrilla verticillata) plants and 

propagules after removal from the aquatic habitat. Weed Science 26: 502-504 (1978).

Bates, A.L., and C.S. Smith. Submersed plant invasions and declines in the southeastern United States. 

Lake and Reservoir Management 10 (1): 53-55 (1994).

Bauer, O.N., N.O. Pugachev, and V.N. Voronin. Study of parasites and diseases of sturgeons in Russia: a 

review. Journal of Applied Ichthyology 18: 420-429 (2002).

Baychorov, V.M. Reproduction of the mysid Paramysis lacustris (Crustacea) in the Northern and 

Southern Zones of its introduction. Hydrobiological Journal 15 (6): 29-34 (1980).

Bayliss, D., and R. Harris. Chloride ion regulation in the freshwater amphipod Corophium curvispinum

and acclimatory effects of external Cl-. Journal of Comparative Physiology B: Biochemical, Systemic, and 

Environmental Physiology 158 (1): 81-90 (1988).

Beatty, S., D. Morgan, and H. Gill. Role of life history strategy in colonization of Western Australian 

aquatic systems by the introduced crayfish Cherax destructor Clark, 1936. Hydrobiologia 549: 219-237 

(2005).

Becker, G.C. Fishes of Wisconsin. University of Madison Press Madison, WI (1983).

Beeton, A.M. Eutrophication of the St. Lawrence Great Lakes. Limnology and Oceanography 10: 240-

254 (1965).

Behning, A.L. Materialy po gidrobiologii reki Urala. Trudy Kazakhskogo filiala Akademii Nauk S.S.S.R 

2 (11): 73-257 (1938).

Behnke, R. Trout and salmon of North America. Simon and Shuster, 384 pp. (2010).
1525

Benson, A.J., Raikow, D., Larson, J., and Fusaro, A. Dreissena polymorpha. USGS Nonindigenous 

Aquatic Species Database, Gainesville, FL (2014). 

http://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=5

Benzie, J.A.H. Guides to the identification of the microinvertebrates of the continental waters of the 

world. Backhyus Publishers, Leiden, The Netherlands (2005). 

Berezina, N.A. Invasion of alien amphipods (Amphipoda: Gammaridea) in aquatic ecosystems of NorthWestern Russia: pathways and consequnces. Hydrobiologia 590: 15-29 (2007).

Berezina, N.A., and V.E. Panov. Establishment of new gammarid species in the eastern Gulf of Finland 

(Baltic Sea) and their effect on littoral communities. Proceedings of the Estonian Academy of Sciences, 

Biology, and Ecology 52 (3): 284-304 (2003).

Berezina, N., S. Golubkov, and J. Gubelit. Grazing effects of alien amphipods on macroalgae in the 

littoral zone of the Neva Estuary (Eastern Gulf of Finland, Baltic Sea). Oceanological and 

Hydrobiological Studies 34 (Supplement 1): 63-82 (2005).

Berezina, N.A., V.V. Petryashev, A. Razinkovas, and J. Lesutiene.Alien malacostracan crustaceans in the 

Eastern Baltic Sea: pathways and consequences. The Wrong Place- Alien Marine Crustaceans: 

Distribution, Biology and Impacts 301-322 pp. (2011).

Berg, L.S. Freshwater Fishes in the U.S.S.R. and Neighbouring Countries. Vol. 2., Fourth edition. 

Translated from Russian by Israel Program for Scientific Translations, Jerusalem, IPST Catalog No. 742. 

496 pp. (1949).

Berg, D.J., D.W. Garton, H.J. MacIsaac, V.E. Panov, and I.V. Telesh. Changes in genetic structure of 

North American Bythotrephes populations following invasion from Lake Ladoga, Russia. Freshwater 

Biology 47: 275-282 (2002). 

Berkeley, Candace. Using aquatic plants to demonstrate photosynthesis. Carolina Biological Supply 

Company, Burlington, NC (2014). http://www.carolina.com/teacher-resources/Interactive/using-aquaticplants-to-demonstrate-photosynthesis/tr28607.tr

Bernauer, D., and W. Jansen. Recent invasions of alien macroinvertebrates and loss of native species in 

the upper Rhine River, Germany. Aquatic Invasions 1 (2): 55-71 (2006).

Bertilsson, J., B. Bērzinš, and B. Pejler. Occurrence of limnic micro-crustaceans in relation to temperature 

and oxygen. Hydrobiologia 299: 163-167 (1995).

Best, R.J., and J.J. Stachowicz. Phylogeny as a proxy for ecology in seagrass amphipods: which traits are 

most conserved? PLoS ONE 8 (3): e57550 (2013).

bij de Vaate, A., K. Jażdżewski, H. A. M. Ketelaars, S. Gollasch, and G. van der Velde. Geographical 

patterns in range extension of Ponto-Caspian macroinvertebrate species in Europe. Canadian Journal of 

Fisheries and Aquatic Sciences 59: 1159-1174 (2002).

Bilko, V.P. Freshwater fishes of the U.S.S.R. and adjacent countries. USSR Academy of Sciences. 

Moscow, Russia (1968).
1526

Billard, R. Les poissons d’eau douce des rivieres de France. Identification, inventaire et repartition des 83 

especes. Lausanne, Delachaux & Niestle. 192 pp. (1997).

Biró, P. Neogobius fluviatilis in Lake Balaton—a Ponto-Caspian goby new to the fauna of central Europe. 

Journal of Fish Biology 4:249-255(1972).

Biró, P. Observations on the food of eel (Anguilla anguilla L.) in Lake Balaton. Annales Instituti 

Biologicia (Tihany) 41: 133-151 (1974).

Biró, P. Temporal variation in Lake Balaton and its fish populations. Ecology of Freshwater Fish 6: 196-

216 (1997).

Biro, P., I.B. Musko. Popukation dynamics and food of bleak (Alburnus alburnus L.) in the littoral zone 

of Lake Balaton, Hungary. Hydrobiologia 310 (2): 139-149 (1995).

Birshteina, Y.A., Vinogradova, L.G., Kondakova, N.N., Kun, M.S., Astahoboj, T.V., and Romanovoj, 

N.N. Atlas of invertebrates of the Caspian Sea. Moscow (1968). 

Blachuta, J. and A. Wikowski. Natural hybrids Alburnus alburnus (L.) X Rutlius rutilus (L.), Alburnus 

alburnus (L.) X Blicca bjoerkna (L.) and Alburnus alburnus (L.) X Abramis brama (L.) from the Oder 

river. Hydrobiologica 25/26:189-203 (1984).

Bodareu, N.N. Dynamics of fishes and populations of several species in reconstructed reservoirs of the 

Dniester River basin. Doctoral Thesis. Moscow (1993).

Bogutskaya, N.G., and A.M. Naseka. An overview of nonindigenous fishes in inland waters of Russia. 

Proceedings of the Zoological Institute of the Russian Academy of Science 296: 21-30 (2002a).

Bogutskaya, N.G., and A.M. Naseka. 2002b. Regional check-lists: Volga river drainage area. Zoological 

Institute. “Freshwater Fishes of Russia” (2002b). 

http://www.zin.ru/Animalia/Pisces/eng/taxbase_e/fauna_e/volga.html

Bole, J.B., and J.R. Allan. Uptake of phosphorous from sediment by aquatic plants, Myriophyllum 

spicatum and Hydrilla verticillata. Water Research 12: 353-358 (1978).

Boltovskoy, D., N. Correa, D. Cataldo, and F. Sylvester. Dispersion and ecological impact of the invasive 

freshwater bivalve Limnoperna fortunei in the Rio de la Plata watershed and beyond. Biological Invasions

8: 947-963 (2006).

Boltovskoy, D., A. Karatayev, L. Burlakova, D. Cataldo, and V. Karatayev. Significant ecosystem-wide 

effects of the swiftly spreading invasive freshwater bivalve Limnoperna fortunei. Hydrobiologia 636 (1): 

271-284 (2009).

Bonar, S.A., B. Bolding, and M. Divens. Effects of triploid Grass Carp on aquatic plants, water quality, 

and public satisfaction in Washington State. North American Journal of Fisheries Management 22: 96-

105 (2002).

Bondarenko, M.V., and E.A. Yablonskaya. The rate of oxygen consumption by the mysid Paramysis 

lacustris (Czern.) from the northern Caspian Sea. Effect of water management on the biological 

productivity of the Azov and Caspian seas. VNIRO, Moscow 65-69 pp. (1979). 
1527

Bonisławska, M., K. Formicki, I. Smaruj, and J. Szulc. Total suspended solids in surface waters versus 

embryonic development of Pike (Esox lucius L.). Electronic Journal of Polish Agricultural Universities 

14: 1-13 (2011).

Bonsdorff, E., and T.H. Pearson. Variation in the sublittoral macrozoobenthos of the Baltic Sea along 

environmental gradients: a functional-group approach. Australian Journal of Ecology 24: 312-326 (1999).

Bonvechio, T.F., B.R. Bowen, J.S. Mitchell, and J. Bythwood. Non-Indigenous Range Expansion of the 

Blue Catfish (Ictalurus furcatus) in the Satilla River, Georgia. Southeastern Naturalist 11: 355-358 

(2012).

Borcea, I. Revision systematique et distribution geographique des gobiides de la mer Noire et 

particulierement des eaux Roumaines. Annales Science University Jassy 19: 1-36 (1934).

Borcherding, J., S. Gertzen, and S. Staas. First record of Pontion racer goby, Babka

gymnotrachelus (Gobiidae: Teleostei), in the River Rhine, Germany. J. Appl. Ichthyol. 27: 1399-1400 

(2011).

Borcherding, J., M. Dolina, L. Heermann, P. Knutzen, S. Krüger, S. Matern, R. van Treeck, and S. 

Gertzen. Feeding and niche differentiation in three invasive gobies in the Lower Rhine, Germany. 

Limnologica - Ecology and Management of Inland Waters 43:49-58 (2013).

Borgstrøm, R., J. Museth, and J.E. Brittain. The Brown Trout (Salmo trutta) in the lake, Ovre 

Heimdalsvatn: long-term changes in population dynamics due to exploitation and the invasive species, 

European Minnow (Phoxinus phoxinus). Hydrobiologia 642: 81-91 (2010).

Borodich, N.D. and Havlena, F.K. The biology of mysids acclimatized in the reservoirs of the Volga 

River. Hydrobiologia 42 (4): 527-539 (1973).

Borsuk, M.E., P. Reichert, A. Peter, E. Schager, and P. Burckhardt-Holm. Assessing the decline of Brown 

Trout (Salmo trutta) in Swiss rivers using a Bayesian probability network. Ecological Modeling 192: 224-

244 (2006).

Bortkevitch, L.V. Ecology and production of Corophium curvispinum in the estuarine sections of rivers of 

the northwest Black Sea coast. Hydrobiological Journal 23 (6): 91-97 (1988).

Borza, P., T. Erős, and N. Oertel. Food Resource Partitioning between Two Invasive Gobiid Species 

(Pisces, Gobiidae) in the Littoral Zone of the River Danube, Hungary. International Review of 

Hydrobiology 94:609-621 (2009).

Boschung, H.T., Jr., and R.L. Mayden. Fishes of Alabama. Smithsonian Books, Washington D.C. 335 pp. 

(2004).

Bossard, C.C., J.M. Randall, and M.C. Hoshovsky. Invasive plants of California’s wildlands. University 

of California Press. 360 pp. (2000)

Bossche, J.P.V., F. Chérot, E. Delooz, F. Grisez, and G. Josens. First record of the Pontocaspian invader 

Hypania invalida (Grube, 1860) (Polychaeta: Ampharetidae) in the river Meuse (Belgium). Belgian 

Journal of Zoology 131 (2): 183-185 (2001).
1528

Bosworth, B. G. Effects of Winter Feeding on Growth, Body Composition, and Processing Traits of CoCultured Blue Catfish, Channel Catfish, and Channel Catfish×Blue Catfish Hybrids. North American 

Journal of Aquaculture 74:553-559 (2012).

Botts, P.S., B.A. Patterson, and W.S. Don. Zebra Mussel Effects on Benthic Invertebrates: Physical or 

Biotic? Journal of the North American Benthological Society 15 (2): 179-184 (1996).

Bourgeois, M. La Vandoise. La Pêche et les Poissons 219: 39 (1963). 

Bourquin, A. Man and mollusc database of edible molluscs (2002). 

http://www.manandmollusc.net/molluscan_food_files/molluscan_food_1.html. Accessed 10 August 2012

Bousfield, E.L. Shallow-water Gammaridean Amphipoda of New England. Cornell University Press, 

Ithaca and London (1973).

Bowes, G. Aquatic plant photosynthesis: strategies that enhance carbon gain. Crawford, R.M.M. (ed.). 

Plant life in aquatic and amphibious habitats. Special Publication No. 5, British Ecological Society. 

Blackwell Scientific Publications, Palo Alto, California 49-98 pp. (1987).

Bowes, G.A.S., T. Holaday, K. Van, and W.T. Haller. Photosynthetic and photorespiratory carbon 

metabolism in aquatic plants. Proceedings 4th International Congress of Photosynthesis. Reading, United 

Kingdom 289-298 pp. (1997).

Boxshall, G. and Defaye, D. World checklist of freshwater Copepoda species (2009). 

http://fada.biodiversity.be/group/show/19

Boyd, C.E. The limnological role of aquatic macrophytes and their relationship to reservoir management. 

Hall, G.E. (ed.). Reservoir fisheries and limnology. American Fisheries Society Special Publication No. 8. 

Bethesda, Maryland 153-166 pp. (1971).

Boyle, J.T., D. Keith, and R. Pfau. Occurrence, reproduction, and population genetics of the estuarine 

Mud Crab, Rhithropanopeus harrisii (Gould) (Decapoda, Panopidae) in Texas Freshwater Reservoirs. 

Crustaceana 83:493-505 (2010).

Brabrand, A., and B. Faafeng. Habitat shift in Roach (Rutilus rutilus) induced by Pikeperch (Stizostedion 

lucioperca) introduction- predation risc versus pelagic behavior. Oecologia 95: 38-46 (1993).

Brabrand, A., T.A. Bakke, and B. Faafeng. The ectoparasite Ichthyophthirius multifiliis and the 

abundance of Roach (Rutilus rutilus)- larval fish epidemics in relation to host behavior. Fisheries 

Research 20: 49-61 (1994).

Bradford, M.J., C.P. Tovey, and L.M. Herborg. Biological risk assessment for Yellow Perch (Perca 

flavescens) in British Columbia. DFO Canadian Science Advisory Secretariat Report 2008/073: vi + 21 

pp. (2008).

Brammer, E.S. Exclusion of phytoplankton in the proximity of dominant Water-Soldier (Stratiotes 

aloides). Freshwater Biology 9: 233-249 (1979).

Brandner, J., A.F. Cerwenka, U.K. Schliewen, and J. Geist. Bigger is Better: characteristics of round 

gobies forming an invasion front in the Danube River. PLoS ONE 8(9): e 73036 (2013).
1529

Braunbeck, T., K. Gorgas, V. Storch, and A. Völkl. Ultrastructure of hepatocytes in Golden Ide 

(Leuciscus idus melanotus L.; Cyprinidae: Teleostei) during thermal adaptation. Anatomy and 

Embryology 175: 303-313 (1987).

Braunbeck, T., and H. Segner. Preexposure temperature acclimation and diet as modifying factors for the 

tolerance of Golden Ide (Leuciscus idus melanotus) to short-term exposure to 4-chloroaniline. 

Ecotoxicology and Environmental Safety 24: 72-94 (1992).

Breitler, A. Death from the deep, September 2, 2006. Recordnet.com News (2006). 

http://www.recordnet.com/apps/pbcs.dll/article?AID=/20060902/NEWS01/609020335/-1/RSS01

Brett, J.R., and D.F. Alderdice. The resistance of cultured young Chum and Sockeye Salmon to 

temperatures below 0°C. Journal of Fisheries Research Board Canada 15: 805-813 (1958).

Bridge, T. Controlling New Zealand Pygmyweed Crassula helmsii using hot foam, herbicide and by 

burying at Old Moor RSPB Reserve, South Yorkshire, England. Conservation Evidence 2: 33 (2005).

Briski, E., S.A. Bailey, M.E. Cristescu, H.J. MacIsaac. Efficacy of ‘saltwater flushing’ in protecting the 

Great Lakes from biological invasions by invertebrate eggs in ships’ ballast sediment. Freshwater 

Biology 55: 2414-2424 (2010).

Britton, J.R. Testing strength of biotic resistance against an introduced fish: Inter-specific competition or 

predation through facultative piscivory? PLoS ONE 7 (2): e31707 (2012).

Britton, J.R., J. Pegg, R. Sedgwick, and R. Page. Investigating the catch returns and growth rate of Wels 

catfish, Silurus glanis, using mark–recapture. Fisheries Management and Ecology 14 (4): 263-268 

(2007).

Britton, J.R., M. Brazier, G.D. Davies and S.I. Chare. Case studies on eradicating the Asiatic cyprinid 

Pseudorasbora parva from fishing lakes in England to prevent their riverine dispersal. Aquatic 

Conservation: Marine and Freshwater Ecosystems 18 (6): 867-876 (2008).

Britton, J.R., G.D. Davies, and C. Harrod. Trophic interactions and consequent impacts of the invasive 

fish Pseudorasbora parva in a native aquatic foodweb: a field investigation in the UK. Biological 

Invasions 12: 1533- 1542 (2010).

Britton, J.R., J. Cucherousset, J. Grey, and R.E. Gozland. Determining the strength of exploitative 

competition from an introduced fish: roles of density, biomass and body size. Ecology of Freshwater Fish

20: 74-79 (2011).

Brown, J.A., W.M. Moore, and E.S. Quabius. Physiological effects of saline waters on Zander. Journal of 

Fish Biology 59: 1544-1555 (2001).

Brown, J.E., and C.A. Stepien. Invasion genetics of the Eurasian Round Goby in North America: tracing 

sources and spread patterns. Molecular Ecology 18: 64-79 (2009).

Brown, T.G., B. Runciman, M.J. Bradford, and S. Pollard. A biological synopsis of Yellow Perch (Perca 

flavescens). Canadian Manuscript Report of Fisheries and Aquatic Sciences 2883 (2009). 
1530

Brucet, S., J. Compte, D. Boix, R. Lopez-Flores, and X.D. Quintana. Feeding of nauplii, copepodites and 

adults of Calanipeda aquaedulcis (Calanoida) in Mediterranean salt marshes. Marine Ecology Progress 

Series 355:183-191 (2008).

Brugnano, C., R. D'Adamo, A. Fabbrocini, A. Granata, and G. Zagami. Zooplankton responses to 

hydrological and trophic variability in a Mediterranean coastal ecosystem (Lesina Lagoon, South Adriatic 

Sea). Chemistry and Ecology 27:461-480 (2011).

Bruijs, M.C.M., B. Kelleher, G. van der Velde, and A. Bij de Vaate. Oxygen consumption, temperature 

and salinity tolerance of the invasive amphipod Dikerogammarus villosus: indicators of further dispersal 

via ballast water transport. Archiv für Hydrobiologie 152: 633-646 (2001).

Brunet, J. Effect of chemical and physical environment on Crassula helmsii spread. NERC/Centre for 

Ecology & Hydrology: 63 (2002).

Bubinas, A. Feeding of fish in the Kaunas hydroelectric plant water reservoir by acclimatized in it 

Mysidae of Mesomysis kowalewskyi Czern. (Paramysis lacustris) of the Caspian complex. Trudy 

Akademii Nauk Litovskoi SSR, Series C 88 (4): 89-96 (1979).

Burlakova, L.E., A.Y. Karatayev, and V.A. Karatayev. Invasive mussels induce community changes by 

increasing habitat complexity. Hydrobiologia 685 (1): 121-134 (2012).

Burr, B.M., and M.L. Warren, Jr. A distributional atlas of Kentucky fishes. Kentucky Nature Preserves 

Commission Scientific and Technical Series 4: 398 pp. (1986).

Bushnell, J., and K. Rao. Dormant or quiescent stages and structures among the Ectoprocta: physical and 

chemical factors affecting viability and germination of statoblasts. Transactions of the American 

Microscopical Society 524-543 pp. (1974).

Bushnoe, T.M., D.M. Warner, L.G. Rudstam, and E.L. Mills. Cercopagis pengoi as a new prey item for 

Alewife (Alosa pseudoharengus) and Rainbow Smelt (Osmerus mordax) in Lake Ontario. Journal of 

Great lakes Research 29: 205-212 (2003).

Buyurgan, Ö., A. Altindăg, and M. Kaya. Zooplankton community structure of Asartepe Dam Lake 

(Ankara, Turkey). Turkish Journal of Fisheries and Aquatic Sciences 10: 135-139 (2010).

Byfield, A.J. Crassula helmsii: Again. Botanical Society of the British Isles News 37: 28 (1984).

Bykhovskaya-Pavlovskaya, I.E., A.V. Gusev, M.N. Dubinina, N.A. Izyumova, T.S. Smirnova, I.L. 

Sokolovskaya, G.G. Shtein, S.S. Shil’man, and V.M. Epshtein. Key to parasites of freshwater fish of the 

USSR. Opredelitel’ parazitov presnovodnykh ryb SSR. 919 pp. (1964). (Translated to English by Israel 

program for Scientific Translation, Jerusalem) 

Cabana, G., A. Tremblay, J. Kalff, and J.B. Rasmussen. Pelagic food chain structure in Ontario lakes: a 

determinant of mercury levels in lake trout (Salvelinus namaycush). Canadian Journal of Fisheries 

Aquatic Sciences 51: 381-389 (1994).

Cabrera Walsh, G., Y. Magalí Dalto, F.M. Mattioli, R.I. Carruthers, and L.W. Anderson. Biology and 

ecology of Brazilian Elodea (Egeria densa) and its specific herbivore, Hydrellia sp., in Argentina. 

BioControl 58 (1): 133-147 (2013).
1531

Caffrey, J.M., B. Hayden, and T. Walsh. Dace (Leuciscus leuciscus L.): an invasive fish species in 

Ireland. Irish Freshwater Fisheries, Ecology and Management. Central Fisheries Board, Dublin, Ireland

(2007). 

Cairns, A., and N. Yan. A review of the influence of low ambient calcium concentrations on freshwater 

daphniids, gammarids, and crayfish. Environmental Reviews 17: 67-79 (2009).

Cakić, P., M. Lenhardt, D. Mickovic, N. Sekulic, and L.J. Budakov. Biometric analysis of Syngnathus 

abaster populations. Journal of Fish Biology 60: 1562-1569 (2002).

Ćaleta, M., D. Jelić, I. Buj, D. Zanella, Z. Marčić, P. Mustafić, and M. Mrakovčić. First record of the 

alien invasive species rotan (Perccottus glenii Dybowski, 1877) in Croatia. Journal of Applied 

Ichthyology. 1-2 (2010). 

California Department of Boating and Waterways, Aquatic Weed Program. Egeria densa Control 

Program (EDCP) (2006). 

California Department of Food and Agriculture (CDFA). Hydrilla program 20.20.01. Program Statement 

2000 Season, Fiscal year 2000/2001. Plant Health and Pest Prevention Services, Integrated Pest Control 

Branch, California Department of Food and Agriculture, Sacramento, California (2000).

California Invasive Plant Council. Egeria densa. Invasive Plants of California’s Wildland (2015). 

California State Parks. Public Notice: DBW begins 2014 Egeria densa control program in Delta. 

California State Parks, Division of Boating and Waterways (2014). 

http://www.dbw.parks.ca.gov/PressRoom/2014/140604EDCP.aspx

Camp, D.K., W.G. Lyons, and T.H. Perkins. Checklists for selected shallow-water marine invertebrates of 

Florida. Florida Marine Research Institute Technical Report TR-3. Florida Department of Environmental 

Protection (1998).

Campbell, J. 2009. Water Soldier the newest recruit in army of invasive species. CommunityPress.ca. 

(2009). http://www.communitypress.ca/2009/08/17/water-soldier-the-newest-recruit-in-army-ofinvasive-species.

Campbell, J.S., and H.R. MacCrimmon. Biology of the emerald shiner, Notropis atherinoides Rafinesque, 

in Lake Simcoe, Canada. Journal of Fish Biology 2: 259-273 (1970).

Canfield, D.E., Jr., and M.V. Hoyer. Aquatic macrophytes and their relationships to Florida Lakes. Final 

Report submitted to Bureau of Aquatic Plants, Florida Department of Natural Resources, Tallahassee, 

Florida. 599 pp. (1992)

Canfield, D.E. Jr. J.V. Shireman, D.E. Colle, W.T. Haller, E.E. Watkins, and M.J. Maceina. Prediction of 

chlorophyll a concentration in Florida Lakes: importance of aquatic macrophytes. Canadian Journal of 

Fisheries and Aquatic Research 41: 497-501 (1984).

Cardwell, A.J., D.W. Hawker, and M. Greenway. Metal accumulation in aquatic macrophytes from 

southeast Queensland, Australia. Chemosphere 48: 653-663 (2002).
1532

Carlson, M.l., I.V. Lapina, M. Shephard, J.S. Conn, R. Densmore, P. Spencer, J. Heys, J. Riley, and J. 

Nielson. Invasiveness ranking system for non-native plants of Alaska. USDA and Forest Service of 

Alaska (2008). http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev2_037575.pdf

Carol, J. Growth and diet of European Catfish (Silurus glanis) in early and late invasion stages. 

Fundamental and Applied Limnology 174 (4): 317-328 (2009).

Carol, J., L. Zamora, and E. García-Berthou. Preliminary telemetry data on the movement patterns and 

habitat use of European Catfish (Silurus glanis) in a reservoir of the River Ebro, Spain. Ecology of 

Freshwater Fish 16 (3): 450-456 (2007).

Carter, M.C., and M.D. Sytsma. Comparison of the genetic structure of North and South American 

populations of a clonal aquatic plant. Biological Invasions 3: 113-118 (2001).

Carter, V., R. Pierce, S. Dufour, C. Arme, and D. Hoole. The tapeworm Ligula 

intestinalis (Cestoda: Pseudophyllidea) inhibits LH expression and puberty in its teleost host, Rutilus 

rutilus. Reproduction 130 (6): 939-945 (2005).

Carvalho, G.R., and H.G. Wolf. Resting eggs of lake - Daphnia: I. Distribution, abundance and hatching 

of diapausing eggs collected from various depths in lake sediments. Freshwater Biology 22: 459-470 

(1989).

Caspian Environment Programme (CEP). Caspian Sea Background (2004). 

http://caspian.iwlearn.org/caspian-1/background-1

Castaldelli, G., A. Pluchinotta, M. Milardi, M. Lanzoni, L. Giari, R. Rossi, and E.A. Fano. Introduction of 

exotic fish species and decline of native species in the lower Po basin, north-eastern Italy. Aquatic 

Conservation: Marine and Freshwater Ecosystems 23 (3): 405-417 (2013).

Castellato, S., G. La Piana, L Latella, and S. Ruffo. Dikerogammarus villosus (Sowinsky 1894), a new 

invasive species in Garda Lake (Northern Italy). Abstracts for Biological Invasions in Inland Waters 

(INWAT) workshop, Firenze, Italy, May -7, 2005 26-27 pp. (2005). 

Cataldo, D., D. Boltovskoy, and M. Pose. Toxicity of chlorine and three non-oxidizing molluscicides to 

the invasive pest mussel Limnoperna fortunei. Journal of the American Waterworks Association 95: 66-

78 (2003).

Cataldo, D., A. Vinocur, I. O'Farrell, E. Paolucci, and V. Leites. The introduced bivalve Limnoperna 

fortunei boosts Microcystis growth in Salto Grande reservoir (Argentina): evidence from mesocosm 

experiments. Hydrobiologia 680 (1): 25-38 (2012a).

Cataldo, D., I.O' Farrell, E. Paolucci, F. Sylvester, and D. Boltovskoy. Impact of the invasive Golden 

Mussel (Limnoperna fortunei) on phytoplankton and nutrient cycling. Aquatic Invasions 7 (1): 91-100 

(2012b).

Çelik, M., A. Diler, and A. Küçükgülmez. A comparison of the proximate compositions and fatty acid 

profiles of Zander (Sander lucioperca) from two different regions and climatic conditions. Food 

Chemistry 92:637-641 (2005).

Center for Disease Control. Parasites- Diphyllobothrium Infection (2013). 

http://www.cdc.gov/parasites/diphyllobothrium/biology.html
1533

Chadwick, M. Water, science, and the public: The Miramichi Ecosystem. Canadian Special Publication 

of Fisheries and Aquatic Sciences 123: 1-300 (1995).

Champion, P.D., D.E. Hofstra, and J.S. Clayton. Border control for potential aquatic weeds. Science & 

Technical Publishing, Department of Conservation, Wellington, New Zealand (2007).

Chappaz, R. G. Brun, and G. Olivari. Evidence for differences in feeding within a population of bleak 

Alburnus alburnus (L.) in the lake of ST. Croix. The consequences of fecundity. Annales de Limnologie

23 (3): 245-252 (1987).

Charlebois, P.M., J.E. Marsden, R.G. Goettel, R.K. Wolfe, D.J. Jude, and S. Rudnika. The round 

goby Neogobius melanostomus (Pallas): a review of European and North American literature. Ill. Nat. 

Hist. Surv. Spec. Publ. 20 (1997).Chen, D.X., M.B. Coughenour, D. Eberts, and J.S. Thullen. Interactive 

effects of CO2 enrichment and temperature on growth of dioecious Hydrilla verticillata. Environmental 

and Experimental Botany 34 (4): 345-353 (1994).

Chen, J.P., D. Xie, D. Zhang, Z. Ke, and H. Yang. In situ studies on the bioaccumulation of microcystins 

in the phytoplanktivorous silver carp (Hypophthalmichthys molitrix) stocked in Lake Taihu with dense 

toxic Microcystis blooms. Aquaculture 26193: 1026-1038 (2006).

Chen, P. E.O. Wiley and M. Mcnyset. 2007. Ecological niche modeling as a predictive tool: silver and bighead 

carps in North America. Biol Invasions 9:43-51.

Chen, W.Q., M.J. Cao, A. Yoshida, G.M. Liu, W.Y. Weng, L.C. Sun, and W.J. Su. Study on pepsinogens 

and pepsins from Snakehead (Channa argus). Journal of Agricultural and Food Chemistry 57 (22): 

10972-10978 (2009).

Chiba, K., T. Yasuhiko, K. sakai, and Y. Oozeki. Present status of aquatic organisms introduced into 

Japan. De Silva, S.S. (ed.) Exotic aquatic organisms in Asia- Proceedings of the Workshop on 

Introduction of Exotic Exotic Aquatic Organisms in Asia: Manila, Philippines. Asian Fisheries Society 

Special Publication 363-70 pp. (1989).

Chick, J.H., and M.A. Pegg. Invasive carp in the Mississippi River Basin. Science 292 (5525): 2250-2251 

(2001).

Chigbu, P., and T.H. Sibley. Relationship between abundance, growth, egg size and fecundity in a 

landlocked population of longfin smelt, Spirinchus thaleichthys. Journal of Fish Biology 45: 1-5 (1994).

Chilton, III, E.W., and M.I. Muoneke. Biology and management of Grass Carp (Ctenopharyngodon 

idella, Cyprinidae) for vegetation control: A North American perspective. Reviews of Fish Biology and 

Fisheries 2: 283-320 (1992)

Chokder, A. Further investigation on control of aquatic vegetation in fisheries. Agriculture Pakistan

(1968).

Chotkowski, M.A., and J.E. Marsden. Round Goby and Mottle Sculpin predation on Lake Trout eggs and 

fry: field predictions from laboratory experiments. Journal of Great Lakes Research 25: 26-35 (1999).

Choudhury, A. and Dick, T.A. Sturgeons (Chondrostei: Acipenseridae) and their metazoan parasites: 

patterns and processes in historical biogeography. Journal of Biogeography Special Issue: Papau New 

Guineae: A Nested Pair of Colonization Sequences 28 (11/12): 1411-1439 (2001). 
1534

Christie, W.J. Changes in the fish species composition of the Great Lakes. Journal of the Fisheries 

Research Board of Canada 31: 827-854 (1974).

Christmas, J.W., and R.S. Waller. Section 5: Estuarine vertebrates, Mississippi. Christmas, J.Y. (ed.). 

Cooperative Gulf of Mexico estuarine inventory and study, Mississippi. Gulf Coast Research laboratory, 

Ocean Springs, MS, 320-406 pp. (1973).

Chucholl, C. Invaders for sale: trade and determinants of introduction of ornamental freshwater crayfish. 

Biological Invasions 15: 125-141 (2013).

Cilliers, C.J. Lysathia n.sp. (Coleoptera: Chrysomelidae), a host-specific beetle for the control of the 

aquatic weed Myriophyllum aquaticum (Haloragaceae) in South Africa. Hydrobiologia 415: 271-276 

(1999).

City of Bloomington (Indiana). Invasive Species. Bloomington Environmental Water Quality Indicators 

(2013). http://bloomington.in.gov/documents/viewDocument.php?document_id=3016

City of Minneapolis (Minnesota). 2013. Aquatic Invasive Species (2013). 

http://www.ci.minneapolis.mn.us/sustainability/indicators/WCMS1P-088402

Clarke, M. Fish imports restricted. Published on Practical Fishkeeping News (2006). 

http://www.practicalfishkeeping.co.uk/content.php?sid=934 Accessed 05 June 2014.

Clarke, W.C., and T. Hirano. Osmoregulation. Physical Ecology of Pacific Salmon. C. Groot, L. 

Margolius, and W.C. Clarke (eds.). UBC Press, University of British Columbia, Vancouver, BC 320-322 

pp. (2010).

Clavero, M., and E. Garcia-Berthou. Homogenization dynamics and introduction routes of invasive 

freshwater fish in the Iberian Peninsula. Ecological Modeling 16: 2313-2324 (2006).

Clement, P., and E. Wurdak. Rotifera. Harrison, F.W., and E.E. Ruppert (eds.). Microscopic anatomy of 

invertebrates. Volume 4. Aschelminthes. Wiley-Liss, New York, NY 219-297 pp. (1991)

Closs, G.P., B. Ludgate, and R.J. Goldsmith. Controlling European Perch (Perca fluviatilis): Lessons 

from an experimental removal. Managing invasive freshwater fish in New Zealand. Proceedings of a 

workshop hosted by Department of Conservation, 10-12 May 2001, Hamilton. 37-48pp. (2003). 

Clowes, W. London International Fisheries Exhibition, 1883. London (1884). 

Cnudde, C. Trophic ecology of intertidal harpacticoid copepods, with emphasis on their interactions with

bacteria. PhD Dissertation, Ghent University (2013).

Cochran, P. A., S. Pociask, H. Warthesen, and N. Proulx. Noteworthy collection: Minnesota. Pistia 

stratiodes L. (Araceae). Water Lettuce. The Michigan Botanist 45: 210-213 (2006).

Cockerill, D. Crassula helmsii. Botanical Society of the British Isles 21:18 (1979).

Cocking, A.W. The effects of high temperatures on Roach (Rutilus rutilus). I. The effects of constant high 

temperatures. Journal of Experimental Biology 36: 203-216 (1958).
1535

Codreanu-Balcescu, D. Sur quelques nouvelles espèces du genre Cephaloidophora, gregarines (Protozoa, 

Apicomplexa) parasites des amphipodes ponto-caspiens de Romanie. Revue Roumaine de Biologie, Série 

de Biologie Animale 4 (1): 3-10 (1995).

Cohen, A.N., and J.T. Carlton. Non-indigenous aquatic species in a United States estuary: A case study of 

the biological invasion of the San Francisco Bay and Delta. A report for the United States Fish and 

Wildlife Service, Washington D.C. and the National Sea Grant College Program Connecticut Sea Grant 

(NOAA Grant Number NA36RG0467) (1995).

Cohen, J.N. Mirotchnick, and B. Leung. Thousands introduced annually: the aquarium pathway for nonindigenous plants to the St. Lawrence Seaway. Frontiers in Ecology 5 (10): 528-532 (2007).

Cole, L.J. The German Carp in the United States. Report of the Bureau of Fisheries for 1904. U.S. 

Department of Commerce and Labor. Government Printing Office, Washington, D.C. 523-641 pp. (1905)

Cole, R.A. Exotic parasite causes large scale mortality in American coots. USGS-NWHC Information 

Sheet (2001).

Cole, R.A., and J.C. Franson. Recurring waterbird mortalities of unusual etiologies. Boere, G.C., C.A. 

Galbraith, and D.A. Stroud (eds.). Waterbirds around the world. The Stationery Office, Edinburgh, UK 

439-440 pp. (2006). 

Cole, R., and M. Friend. Miscellaneous Parasitic Diseases. Field Manual of Wildlife Diseases: Birds. 

United States Geological Survey 249-258 pp. (1999). 

Cole, R.A., and M. Jankowski. Exotic parasites affect American Coots in upper Midwest. USGS (ed.). 

Wildlife Health Bulletin 07-01. Wildlife Health Bulletin 4 pp. (2007).

Colle, D.E., and J.V. Shireman. Coefficients of condition for Largemouth Bass, Bluegill, and Redear 

Sunfish in Hydrilla-infested lakes. Transactions of American Fisheries Society 109: 521-531 (1980). 

Collette, B.B., M.A. Ali, K.E.F. Hokanson, M. Nagiec, and S.A. Smirnov. Biology of Percids. Journal of 

the Fisheries Research Board of Canada 34:1890-1899 (1977).

Combes, C. Parasitism: the ecology and evolution of intimate interactions. University of Chicago Press 

(2001).

Connecticut Agricultural Experiment Station. 2012 Aquatic Plant Survey of Fence Rock Lake (2013). 

Conover, G., R. Simmonds, and M. Whalen. Management and control plan for Bighead, Black, Grass, 

and Silver Carps in the United States. Asian Carp Working Group, Aquatic Nuisance Species Task Force, 

Washington D.C. 223 pp. (2007).

Cook, C.D.K., and R. Lüönd. A revision of the genus Hydrilla (Hydrocharitacea). Aquatic Botany 13: 

485-504 (1982).

Cooke, G.D., E.B. Welch, S. Peterson, and S.A. Nichols. Restoration and Management of Lakes and 

Reservoirs, Third Edition. CRC Press, Taylor and Francis Group. Boca Raton, FL (2005). 
1536

Copp, G. Is European catfish Silurus glansis really becoming more abundant in the River Thames? 

Aquatic Invasions 2 (2): 113-116 (2007).

Copp, G.H., P.G. Bianco, N.G. Bogutskaya, T. Erős, I. Falka, M.T. Ferreira, M.G. Fox, J. Freyhof, R.E. 

Gozlan, J. Grabowska, V. Kováč, R. Moreno-Amich, A.M. Naseka, M. Peňáz, M. Povž, M. Przybylski, 

M. Robillard, I.C. Russell, S. Stakėnas, S. Šumer, A. Vila-Gispert, and C. Wiesner. To be, or not to be, a 

non-native freshwater fish? Journal of Applied Ichthyology 21: 242-262 (2005).

Copp, G.H., J. England, R. Tyner, M.G. Carter, S. Stakenas, M. Przybylski, and K. J. Wesley. Growth 

and condition of Dace Leuciscus leuciscus (L. 1758) in the River Lee (Hertfordshire) relative to selected 

populations elsewhere in Europe. The London Naturalist 86: 71-83 (2007).

Copp, G.H., V. Kovác, I. Zweimüller, A. Dias, M. Nascimento, and M. Balážová. Preliminary study of 

dietary interactions between invading Ponto-Caspian gobies and some native fish species in the River 

Danube near Bratislava (Slovakia). Aquatic Invasions 3 (2): 193-200 (2008).

Copp, G.H., J. Robert Britton, J. Cucherousset, E. García-Berthou, R. Kirk, E. Peeler, and S. Stakėnas. 

Voracious invader or benign feline? A review of the environmental biology of European Catfish Silurus 

glanis in its native and introduced ranges. Fish and Fisheries 10 (3): 252-282 (2009).

Copp, G.H., L. Vilizzi, and R.E. Gozlan. Fish movements: the introduction pathway for Topmouth 

Gudgeon and other non-native fishes in the UK. Aquatic conservation 20 (3): 269-273 (2010).

Cordo, H.A., C.J. DeLoach, and R. Ferrer. Biological studies of two weevils, Ochetina bruchi and 

Onychylis cretatus, collected from Pistia and other aquatic plants in Argentina. Annals of the 

Entomological Society of America 74: 363-369 (1981).

Corkum, L.D., M.R. Sapota, and K.E. Skora. The round goby, Neogobius melanostomus, a fish invader 

on both sides of the Atlantic Ocean. Biological Invasions 6: 173-181 (2004).

Costedoat, C., R. Chappaz, B. Barascud, O. Guillard, and A. Gilles. Heterogeneous colonization pattern 

of European Cyprinids, as highlighted by the Dace complex (Teleostei: Cyprinidae). Molecular 

Phylogenetics and Evolution 41: 127-148 (2006).

Costlow, J. D., C. G. Bookhout, and R. J. Monroe. Studies on larval development of crab 

Rhithropanopeus harrisii (Gould). I. Effect of salinity and temperature on larval development. 

Physiological Zoology 39: 81-100 (1966).

Courtenay, W.R. United States Fish and Wildlife Service, Lacey Act Evaluation Criteria, Rotan, 

Perccotus glenii (Pisces, odontobutidae). Technical Assistance Document to the United States Fish and 

Wildlife Service. 13 pp. (2006).

Courtenay, W.R., Jr., D.A. Hensley, J.N. Taylor, and J.A. McCann. Distribution of exotic fishes in the 

continental United States. Courtenay, W.R., Jr., and J.R. Stauffer, Jr, (eds.). Distribution, biology, and 

management of exotic fishes. John Hopkins University Press. Baltimore, MD 41-77 pp. (1984).

Courtenay, W.R., Jr., and J.D. Williams. Snakehead (Pisces: Channidae): A biological synopsis and risk 

assessment. United States Geological Survey Circular 1251, 143 pp. (2004). 
1537

Cowx, I.G. Distribution and variation in the growth of Roach, Rutilus rutilus (L.), and Dace, Leuciscus 

leuciscus (L.), in a river catchment in south-west England. Journal of Fish Biology 33 (1): 59-72 (1988).

Cowx, I. Introduction of fish species into European fresh waters: economic successes or ecological 

disasters? Bulletin Français de la Pêche et de la Pisciculture 70 (1997).

Cowx, I.G. Factors affecting coarse fish populations in rivers. R&D Publication 18, Environment Agency, 

Rio House, Waterside Drive, Aztec West, Almodsbury, Bristol BS34 4 UD (2001).

Cragg-Hine, D. Coarse fish and fishery management in Northern Ireland. Proceedings of the 6th British 

Freshwater Fisheries Conference, University of Liverpool (1973).

Craig, J.F. Percid fishes. Systematics, Ecology and Exploitation. Blackwell Science, London. 352 pp. 

(2000).

Crawford, G. Corophium curvispinum, GO Sars, var devium, Wundsch, in England. Nature 136: 685-685 

(1935).

Crawford, S.S. Salmonine introductions to the Laurentian Great Lakes: an historical review and 

evaluation of ecological effects. Canadian Special Publication of Fisheries and Aquatic Sciences 132: 1-

193 (2001).

Creative Homeowner. SmartGuide to ponds, fountains, and waterfalls 2nd Edition, Federal Marketing 

Corp, Upper Saddle River, NJ. 98 p. (2010).

Cristescu, M.E.A., and P.D.N. Hebert. The “Crustacean Seas”- an evolutionary perspective on the PontoCaspian peracarids. Canadian Journal of Fisheries and Aquatic Sciences 62: 505-517 (2005).

Crivelli, A.J. Are fish introductions a threat to endemic freshwater fishes in the Northern Mediterranean 

region? Biological Conservation 72: 311-319 (1995).

Crivelli, A.J. and F. Dupont. Biometrical and biological features of Alburnus alburnus x Rutilus 

rubilio natural hybrids from Lake Mikri Prespa, northern Greece. Journal of Fish Biology 31(6): 721-733 

(1987).

Crosier, D.M., and D.P. Molloy. Golden Mussel. United States Army Corps of Engineers (2004). 

http://el.erdc.usace.army.mil/ansrp/limnoperna_fortunei.pdf

Crosier, D.M., D.P. Molloy, and J.E. Marsen. Gymnocephalus cernuus- Ruffe. United States Army Corps 

of Engineers (USACE) (2007). 

http://el.erdc.usace.army.mil/ansrp/ANSIS/html/gymnocephalus_cernuus_ruffe.htm

Crosier, D.M., D.P. Molloy, A. Bij de Vaate, and S. Devin. Killer Shrimp-Dikerogammarus villosus

(2011). http://el.erdc.usace.army.mil/ansrp/dikerogammarus_villosus.pdf

Crossman, E.J., and B.C. Cudmore. Summary of North American fish introductions through 

aquarium/horticulture trade. Claudi, R., and J.H. Leach (eds.). Nonindigenous freshwater organisms. 

Lewis Publishers, Boca Raton, Florida 129-133 pp. (1999a).
1538

Crossman, E.J., and B.C. Cudmore. Summary of North American introductions of fish through the 

aquaculture vector and related human activities. Claudi, R., and J.H. Leach (eds.). Nonindigenous 

Freshwater Organisms. Lewis Publishers, Boca Raton, Florida 297-304 pp. (1999b).

Crossman, E.J., and B.C. Cudmore. Overview of the spread of fishes introduced by various vectors. Royal 

Ontario Museum, Pembroke, ON, Canada (2000).

Cucherousset, J. and J.D. Olden. Ecological impacts of Nonnative freshwater fishes. Fisheries 36: 215-

230 (2011).

Cucherousset, J., S. Boulêtreau, F. Azémar, A. Compin, M. Guillaume, and F. Santoul. Freshwater Killer 

Whales: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLoS ONE 7 (12): e50840 (2012).

Cuda, J.P., and D.L. Sutton. Is the aquatic weed Hygrophila, Hygrophila polysperma (Polemoniales: 

Acanthaceae), a suitable target for classical biological control? Spencer, N.R. (ed.). Proceedings of the X 

International Symposium on Biological Control of Weeds. July 4-14, 1999, Bozeman, Montana 337-348 

pp. (2000).

Cudmore, B., and N.E. Mandrak. Biological synopsis of Grass Carp (Ctenopharyngodon idella). 

Canadian Manuscript Report of Fisheries and Aquatic Sciences 2705. Fisheries and Oceans Canada, 

Burlington, Ontario (2004).

Cudmore, B., N.E. Mandrak, J. Dettmers, D.C. Chapman, and C.S. Kolar. Binational ecological risk 

assessment of Bigheaded Carps (Hypophthalmichthys spp.) for the Great Lakes basin. DFO Canadian 

Science Advisory Secretariat Report 2011/114 (2012).

Cunha, M.R., J.C. Sorbe, and M.H. Moreira. The amphipod Corophium multisetosum (Corophiidae) in 

Ria de Aveiro (NW Portugal). I. Life history and aspects of reproductive biology. Marine Biology 137: 

637-650 (2000).

Curt, M.D., G. Curt, P.L. Aguado, and J. Fernandez. Proposal for the biological control of Egeria densa

in small reservoirs: A Spanish case study. Journal of Aquatic Plant Management 48: 124-127 (2009).

Czarnecka, M., J. Kobak, and R. Wiśniewski. Preferences of juveniles and adults of the invasive PontoCaspian amphipod Pontogammarus robustoides for various species of macrophytes and artificial 

substrata. Hydrobiologia 655 (1): 79-88 (2010).

Czarnecki, M., W. Andrzejewski., and J. Mastynski. The feeding selectivity of Wels (Silurus glanis L.) in 

Goreckie Lake (Poland). Archives of Polish Fisheries 11: 141-147 (2003).

Czeczuga, B., M. Kozlowska, and A. Godlewska. Zoosporic aquatic fungi growing on dead specimens of 

29 freshwater crustacean species. Limnologica- Ecology and Management of Inland Waters 32 (2): 180-

193 (2002). 

Czerniejewski, P., and A. Rybczyk. Body weight, morphometry, and diet of the mud crab, 

Rhithropanopeus harrisii tridentatus (Maitland, 1874) in the Odra estuary, Poland. Crustaceana 81:

1289-1299 (2008).

DAISIE European Invasive Alien Species Gateway. Cyclops kolensis (2008a). http://www.europealiens.org/speciesFactsheet.do?speciesId=100274#
1539

DAISIE European Invasive Alien Species Gateway. Obesogammarus obesus (2008b) http://www.europealiens.org/speciesFactsheet.do?speciesId=53402

Daneliya, M.E. Paramysis sowinskii sp. n. - a new species of Mysidacea (Crustacea) from the PontoCaspian basin. Vestnik Zoologie 36 (2): 69-72 (2002).

Daneliya, M.E. Mysids (Crustacea: Mysidacea) of the Sea of Azov Basin. PhD Thesis, St. Petersburg 

(2003). 

Danilkiewicz, Z. Babka szczupla, Neogobius fluviatilis (Pallas, 1811), Perciformes, Gobiidae – nowy, 

pontyjski element w ichtiofaunie zlewiska Morza Baltyckiego. Fragmenta Faunistica 41(21): 269-277 

(1998).

Daoulas, C., Economou, A.N., Psarras, T., and Barbieri-Tseliki, R. Reproductive strategies and early 

development of three freshwater gobies. Journal of Fish Biology 42: 749-776 (1993). 

Darrigran, G., S. Martin, B. Gullo, and L. Armendariz. Macroinvertebrates associated with Limnoperna 

fortunei (Dunker, 1857) (Bivalvia, Mytilidae) in Río de la Plata, Argentina. Hydrobiologia 367 (1-3): 

223-230 (1998).

Darrigran, G., and C. Damborenea. Ecosystem engineering impact of Limnoperna fortunei in South 

America. Zoological Science 28 (1): 1-7 (2011).

Daulwater, D.C., D.K. Splinter, W.L. Fisher, and R.A. Marston. Biogeography, ecoregions, and 

geomorphology affect fish species composition in streams of eastern Oklahoma, USA. Environmental

Biology of Fishes 82: 237-249 (2008).

Dauvin, J.C. Paradox of estuarine quality: benthic indicators and indices, consensus or debte for the 

future. Marine Pollution Bulletin 55: 271-281 (2007).

David, J.A. Water quality and accelerated winter growth of European Catfish using an enclosed 

recirculating system. Water and Environment Journal 20 (4): 233-239 (2006).

Davis, J.T. Exotic aquatic plants- some good; some bad. 8th Triennial National Wildlife & Fisheries 

Extension Specialists Conference (1996). 

Dawes, B. The Trematoda. Cambridge University Press (1968).

Dawson, F.H. Crassula helmsii: attempts at elimination using herbicides. Hydrobiologia 340 (1-3): 241-

245 (1996).

Dawson, C. E. Syngnathidae. Whitehead, P.J.P., M.L. Bauchot, J.C. Hureau, J. Nielsen, and E. Tortonose 

(eds.) Fishes of the North-eastern Atlantic and Mediterranean. UNESCO, Paris. 628-639 pp. (1986).

Dawson, F.H., and E.A. Warman. Crassula helmsii (T. Kirk) cockayne: Is it an aggressive alien aquatic 

plant in Britain? Biological Conservation 42 (4): 247-272 (1987).

De Groote, H., O. Ajuonu, S. Attignon, R. Djessou, and P. Neuenschwander. Economic impact of 

biological control of Water Hyacinth in Southern Benin. Ecological Economics 45 (1): 105-117 (2003).
1540

de Kluijver, M.J., and S.S. Ingalsuo. Macrobenthos of the North Sea- Crustacea. Corophium curvispinum 

(1999). http://speciesidentification.org/species.php?species_group=crustacea&menuentry=soorten&id=298&tab=beschrijving

de la Cruz, A. Va CNA contra la plaga del ‘repollito’. Conexion Total August 12, 2014 (2014). 

http://conexiontotal.mx/2014/08/12/va-cna-contra-la-plaga-del-repollito/

De Winton, M.D., and J.S. Clayton. The impact of invasive submerged weed species on seed banks in 

lake sediments. Aquatic Botany 53: 31-45 (1996).

Deaton, L.E., J.G.S. Derby, N. Subhedar, and M.J. Greenberg. Osmoregulation and salinity tolerance in 

two species of bivalve mollusc: Limnoperna fortunei and Mytilopsis leucophaeta. Journal of 

Experimental Marine Biology and Ecology 133 (1-2): 67-79 (1989).

Dediu, I.I. Répartition et caractéristique écologique des Mysides des bassins des rivières Dniestr et Pruth. 

Revue Roumaine de Biologie-Zoologie 11 (3): 233-239 (1966).

Dedyu, I. Amphipods of fresh and salt waters of the South-West part of the USSR. Shtiintsa Publishers, 

Kishivev, Moldova (1980).

DeGraaf, R.N., and J.M. Wentworth. Avian guild structure and habitat associations in suburban bird 

communities. Urban Ecology 9: 399-412 (1986).

DeGroot, P.J. Introduction and summary. Greathead, A., and P. DeGroot (eds.). Control of Africa’s 

floating water weeds. Berks, UK: CAB International 1-4 pp. (1993). 

Demeter, L., and F. Marrone. Updated check-list and distribution of inland-water calanoid copepods 

(Copepoda: Calanoida) of Romania. North-Western Journal of Zoology 5 (2): 370-378 (2009).

den Hartog, C., and G. Van der Velde. Invasions by plants and animals into coastal, brackish, and fresh 

water of the Netherlands. Proc K Acad Wet 90(1): 31-37 (1987).

den Hartog, C., F. van den Brink, and G. van der Velde. Why was the invasion of the river Rhine by 

Corophium curvispinum and Corbicula species so successful? Journal of Natural History 26 (6): 1121-

1129 (1992).

Dennison, W.C., R.J. Orth, K.A. Moore, J.C. Stevenson, V. Carter, S. Kollar, P.W. Bergstrom, and R.A. 

Batiuk. Assessing water quality with submersed aquatic vegetation. Bioscience 43: 86-94 (1993).

Denton, E.J. and J.A.C. Nicol. Studies on reflexion of light from silvery surfaces of fishes, with special 

reference to the bleak, Alburnus alburnus. Journal of Marine Biological Association of the United

Kingdom 45(3): 683-703 (1965).

Dermott, R., Witt, J., Um, Y.M., and Gonzalez, M. Distribution of the Ponto-Caspian Amphipod 

Echinogammarus ischnus in the Great Lakes and replacement of native Gammarus fasciatus. Journal of 

Great Lakes Research 24: 442-452 (1998).

DeVaney, S.C., K.M. McNyset, J.B. Williams, A.T. Peterson, and E.O. Wiley. A tale of four “carp”: 

invasion potential and ecological niche modeling. PLoS ONE 4(5): 35451 (2009).
1541

Devin, S., J.N. Beisel, V. Bachmann, and J.C. Moreteau. Dikerogammarus villosus (Amphipoda: 

Gammaridae): another invasive species newly established in the Moselle River and French hydrosystems.

Annals of Limnology 37: 21-27 (2001).

Devin S., C. Piscart, J.N. Beisel, and J.C. Moreteau. Ecological traits of the amphipod invader 

Dikerogammarus villosus on a mesohabitat scale. Archiv für Hydrobiologie 158 (1): 43-56 (2003).

Devin, S., C. Piscart, J.N. Beisel, and J.C. Moreteau. Life history of the invader Dikerogammarus villosus

(Crustacea: Amphipoda) in the Moselle River, France. Internationale Revue der gesamten Hydrobiologie

89: 21-34 (2004).

Devin, S., and J.N. Beisel. Dikerogammarus villosus. Delivering Invasive Alien Species Inventories for 

Europe (DAISIE) (2006). http://www.europealiens.org/pdf/Dikerogammarus_villosus.pdf

Devin, S., M. Akopian, J.F. Fruget, A. Di Michelle, and J.N. Beisel. First ecological observations in 

French hydro systems of freshwater Polychaeta Hypania invalida introduced in Western Europe. Vie et 

Milieu 56: 247-254 (2006).

Devin, S., and J.N. Beisel. Biological and ecological characteristics of invasive species: A gammarid 

study. Biological Invasions 9 (1): 13-24 (2007).

Dezfuli, B.S., G. Grandi, P. Franzoi, and R. Rossi. Digestive tract histopathology in Acipenser naccarii

(Bonaparte) from the Po River resulting from infection with Leptorhynchoides plagicephalus

(Acanthocephala). Rivista di Hidrobiologia 29: 177-183 (1990). 

Dezfuli, B.S., L. Giari, R. Konecny, P. Jaeger, and M. Manera. Immunohistochemistry, ultrastructure and 

pathology of gills of Abramis brama from Lake Mondsee, Austria, infected with Ergasilus sieboldin

(Copepoda). Diseases of Aquatic Organisms 53: 257-262 (2003).

Di Fiori, E., H. Pizarro, M. dos Santos Afonso, and D. Cataldo. Impact of the invasive mussel 

Limnoperna fortunei on glyphosate concentration in water. Ecotoxicology and Environmental Safety 81: 

106-113 (2012).

Dick, J.T.A., and D. Platvoet. Invading predatory crustacean Dikerogammarus villosus eliminates both 

native and exotic species. Proceedings of the Royal Society of London 267: 977-983 (2000).

Dick, J.T.A., and D. Platvoet. Predicting future aquatic invaders; the case of Dikerogammarus villosus.

Aquatic Nuisance Species 4: 25-27 (2001).

Dick, J.T.A., D. Platvoet, and D.W. Kelly. Predatory impact of the freshwater invader Dikerogammarus 

villosus (Crustacea: Amphipoda). Canadian Journal of Fisheries and Aquatic Sciences 59: 1078-1084 

(2002).

Dierauf, L. Exotic parasite of American coot discovered in exotic snail in Lake Onalaska. United States 

Geological Survey Wildlife Health Bulletin 07-01 (2007).

Dikov, T., and M. Zivkov. Abundance and biomass of fishes in the Veleka River, Bulgaria. Folia 

Zoologica 53 (1): 81-86 (2004).
1542

Dillon, A.K., and C.A. Stepien. Genetic and biogeographic relationships of the invasive Round 

(Neogobius melanostomus) and Tubenose (Proterorhinus marmoratus) Gobies in the Great Lakes versus 

Eurasian populations. Journal of Great Lakes Research 27(3): 267-280 (2001).

Dobrzycka-Krahel, A., and J. Surowiec. Osmoregulation in Pontogammarus robustoides (GO Sars, 1894) 

(Amphipoda) and its distribution in the brackish waters of northern Poland. Crustaceana 84 (14): 1755-

1767 (2011).

Doll, J. C. Changes in fish assemblages of Killbuck Creek and Pipe Creek, Delaware County, Indiana. 

Proceedings of the Indiana Academy of Science 119: 52-63 (2010).

Domaizon, I., and J. Devaux. Experimental study of the impacts of Silver Carp on plankton communities 

of utrophic Villerest reservoir (France). Aquatic Ecology 33:193-204 (1999).

Dorts, J., G. Grenouillet, J. Douxfils, S.N. Mandiki, S. Milla, F. Silvestre, and P. Kestemont. Evidence 

that elevated water temperature affects the reproductive physiology of the European Bullhead Cottus 

gobio. Fish Physiolology & Biochemistry 38: 389-399 (2012).

Doulka, E., G. Kehayias, E. Chalkia, and I.D. Leonardos. Feeding strategies of Atherina boyeri (Risso 

1810) in a freshwater ecosystem. J. Applied. Ichthyology 29: 200-207 (2013).

Doyle, R.D., M.D. Francis, and R.M. Smart. Interference competition between Ludwigia repens and 

Hygrophila polysperma: two morphologically similar aquatic plant species. Aquatic Botany 77 (3): 223-

234 (2003).

Drake, D.A.R. Quantifying the likelihood of human-mediated movements of species and pathogens: the 

baitfish pathway in Ontario as a model system. PhD Thesis, Department of Ecology and Evolutionary 

Biology, University of Toronto. 295pp. (2011).

Dubinina, M.N. Development of Amphilina foliacea (Rud.) on all stages of life cycle and situation of 

Amphilinea in the system of Platodes. Parsitology Sbornik 26: 9-38 (1974).

Dubs, D.O.L., and L.D. Corkum. Behavioral interactions between Round Gobies (Neogobius 

melanostomus) and Mottled Sculpins (Cottus bairdi). Journal of Great Lakes Research 22 (40): 838-844 

(1996).

Duggan, I. C., C.D.A. Van Overdijk, and S.A. Bailey. Invertebrates associated with residual ballast water 

and sediments of cargo-carrying ships entering the Great Lakes. Canadian Journal of Fishery and 

Aquatic Sciences 62 (11): 2463-2474 (2005).

Dukravets, G.M., and A.I. Machulin. The morphology and ecology of the Amur snakehead, 

Ophiocephalus argus warpachowskii, acclimatized in the Syr Dar’ya basin. Journal of Ichthyology 18(2): 

203-208 (1978).

Dumont, H.J. The Caspian Lake: history, biota, structure, and function. Limnology and Oceanography 43 

(1): 44-52 (1998).

Dumont, S. A new invasive species in the north-east of France, Hemimysis anomala GO Sars, 1907 

(Mysidacea). Crustaceana 79 (10): 1269-1274 (2006).
1543

Dupre, S. An assessment of early detection monitoring and risk assessments for aquatic invasive species 

in the Great Lakes- St. Lawrence Basin. Prepared for the IJC Work group on Aqutic Invasive Species 

Rapid Response (2011).

Dzyuban, N.A., and N.B. Slobodchikov. Hypania invalida (Grube 1860) in the Volga reservoirs and 

hydrobiological monitoring. Hydrobiological Journal 16: 56-59 (1980).

Ebert, D. Ecology, Epidemiology, and Evolution of Parasitism in Daphnia. Zoologisches Institut der 

universitat Basel, Evolutionsbiologie, Vesalgasse (2005).

Eckmann, R. Overwinter changes in mass and lipid content of Perca fluviatilis and Gymnocephalus 

cernuus. Journal of Fish Biology 65: 1498-1511 (2004).

Economidis, P.S., and P.J. Miller. Systematics of freshwater gobies from Greece (Teleostei: Gobiidae). 

Journal of Zoology 221: 125-170 (1990).

Economidis, P.S., E. Dimitriou, R. Pagoni, E. MIchaloudi, and L. Natsis. Fish. Man. Ecol. 7: 239-250 

(2000).

Economou, A.N., C. Daoulas, T. Psarras, and R. Barbieritseliki. Further data on the reproduction and 

larval development of Knipowitschia-caucasica (Gobiidae). Journal of Fish Biology 45: 360-362 (1994).

Edgar, P., and D.R. Bird. Action plan for the conservation of the Italian Agile Frog (Rana latastei) in 

Europe. Convention on the conservation of European wildlife and natural habitats 25th meeting, 3-18 pp. 

(2005).

Eggers, T.O., and A. Anlauf. Hypania invalida (Grube, 1860) (Polychaeta: Ampharetidae) in der 

Mittleren Elbe. Lauterbornia 62: 11-13 (2008).

Eggleton, M.A., and H.L. Schramm Jr. Feeding ecology and energetic relationships with habitat of Blue 

catfish, Ictalurus furcatus, and Flathead Catfish, Pylodictis olivaris, in the lower Mississippi River, USA. 

Environmental Biology of Fishes 70: 107-121 (2004).

Egloff, D.A., P.W. Fofonoff, and T. Onbe. Reproduction of marine Cladocera and related taxa. Advances 

in Marine Biology 31 pp. (1996)

Elakovich, S.D., and J.W. Wooten. Allelopathic potential of sixteen aquatic and wetland plants. Journal 

of Aquatic Plant Management 27: 78-84 (1989).

Elexová, E., and D. Némethová. The effect of abiotic environmental variables on the Danube 

macrozoobenthic communities. Limnologica- Ecology and Mangement of Inland Waters 33: 340-354 

(2003).

Eljarrat, E., A. de la Cal, D. Raldua, C. Duran, and D. Barcelo. Brominated flame retardants in Alburnus 

alburnus from Cinca River Basin (Spain). Environmental Pollution 133(3): 501-508 (2005).

Ellis, S. and H.J. MacIsaac. Salinity tolerance of Great Lakes invaders. Freshwater Biology 54: 77-89 

(2009).
1544

El-Sahn, M.A., A.M. Youssef, and Y.G. Moharram. Edible products from pelagic bissaria (Atherina 

mochon) fish. Food/Nahrung 34(1): 47-52 (1990).

Elvira, B. Native and exotic freshwater fishes in Spanish river basins. Freshwater Biology 33 (1): 103-

108 (1995).

Emery, L. Review of fish introduced into the Great Lakes, 1819-1974. Technical Report No. 45. Great 

Lakes Fishery Commission, Ann Arbor, MI (1985).

Encyclopedia Brittanica. Black Sea, Eurasia (2015). http://www.britannica.com/place/Black-Sea

Engineer Research and Development Center. Myriophyllum aquaticum (Vell.) Verdc. (Parrotfeather). in

PMIS, Noxious and Nuisance Plant Management Information Systems. United States Army Engineer 

Research and Development Center, Environmental Laboratory, Vicksburg, MS (2007).

Engle, C.R., and D.W. Brown. Growth, yield, dressout, and net returns of bighead 

carp Hypophthalmichthys nobilis stocked at three densities in catfish Ictalurus punctatus ponds. Journal 

of the World Aquaculture Society 29(4):414-421 (1998).

Engman, J. Phylogeny and biogeography of the genus Heterocope Sars 1863 (Copepoda: Calanoida): A 

molecular genetic, morphological, and distributional analysis. PhD Thesis, University of Cincinnati 

(1994).

Eno, N.C., R.A. Clark, and W.G. Sanderson. Non-native marine species in British waters: a review and 

directory. Joint Nature Conservation Committee, Peterborough, 152 pp. (1997).

Environmental and Resource Technology (ERT) Caspian. SDX1 Post Well Survey, ERT 0610 –Revision 

2. Report produced for BP (2000). 

http://www.kaspinfo.com/kic/desktop/azerbaijan/sections/monitoring/Section_04_Water_column_SDX1_

post_well_survey.__Revision_2.pdf

Ermolin, V.P. Composition of ichthyofauna of the Saratov Reservoir. Journal of Ichthyology 50(2): 211-

215 (2010).

Erös, T., A. Sevscik, B. Toth. Abundance and night-time habitat use patterns of Ponto-Caspian gobiid 

species (Pisces, Gobiidae) in the littoral zone of the River Danube, Hungary. Journal Applied Icthyology

21 (4): 350-357 (2005).

Esler, D. An assessment of American Coot herbivory of Hydrilla. Journal of Wildlife Management 53: 

1147-1149 (1989).

Estes, J.R., W.A. Sheaffer, and E.P. Hall. Study I. Fisheries studies of the Orange Lake chain of Lakes. 

Florida Game and Fresh Water Fish Commission, Completion Report as Required by Federal Aid in 

Sport Fish Restoration Wallop-Breaux Project F-55-R Lower Ocklawaha Basin Fisheries Investigations, 

Tallahassee, Florida. 86 pp. (1990).

European and Mediterranean Plant Protection Organization (EPPO). Crassula helmsii. Bulletin 

OEPP/EPPO 37: 225-229 (2007).
1545

Evans, D.L., D.G. Strom, J. Higman, E. Hughes, E.A. Hoover, and L.M. Line. An evaluation of benthic 

macroinvertebrate data from 20 surface water sites within the lower St. Johns river basin, 2002-2003. St. 

Johns River Water Management District Special Publication SJ2004-SP41, 110 pp. (2004).

Everitt, B. Freshwater Ectoprocta: distribution and ecology of five species in southeastern Louisiana. 

Transactions of the American Microscopical Society 94: 130-134 (1975).

Eyraud, A., and H. MacIsaac. Range and survival of two alien macrophyties (Eichhornia crassipes and 

Pistia stratiotes) in the Great Lakes International Conference on Aquatic Invasive Species, Niagara Falls, 

Ontario, Canada (2013).

Ezhova, E., L. Zmudzinski, and K. Maciejewska. Long-term trends in the macrozoobenthos of the Vistula 

Lagoon, southeastern Baltic Sea. Species composition and biomass distribution. Bulletin of the Sea 

Fisheries Institute 1:55-73 (2005).

Faasse, M., and G. van Moorsel. The North-American amphipods, Melita nitida Smith, 1873 and 

Incisocalliope aestuarius (Watling and Maurer, 1973) (Crustacea: Amphipoda: Gammaridea), introduced 

to the Western Scheldt estuary (The Netherlands). Aquatic Ecology 37: 13-22 (2003).

Faisal, M., M. Shavalier, R.K. Kim, E.V. Milard, M.R. Gunn, A.D. Winters, C.A. Schultz, A. Eissa, M.V. 

Thomas, M. Wolgamood, G.E. Whelan, and J. Winton. Spread of the emerging Viral Hemorrhagic 

Septicemia Virus Strain, Genotype IVb, in Michigan, USA. Viruses 4: 734-760 (2012).

Falck, M., S. Garske, and D. Olson. Invasive species program 2009. Administrative report 10-11. Great 

Lakes Indian Fish & Wildlife Commission, Biological Services Division (2010). 

Fan, P.C. Viability of metacercariae of Clonorchis sinesis in frozen or salted freshwater fish. Integrated 

Journal of Parasitology 28(4): 603-605 (1998).

Fazli, H., and K. Besharat. Kilka stock assessment using hydro-acoustic method and commercial catch 

monitoring. Mazandaran Fisheries Research Center Final Report 1976-1977. 105pp. (1998).

Fazli, H., C.I. Zhang, D.E. Hay, C.W. Lee, A.A. Janbaz, and M.S. Bourani. Population dynamics and 

stock assessment of Common Kilka (Clupeonella cultriventris caspia) in Iranian waters of the Caspian 

Sea. Iranian Journal of Fisheries Science 7(1): 47-70 (2007).

Federation of New Zealand Aquatic Societies (FNZAS). Hygrophila polysperma (1988). 

http://www.fnzas.org.nz/?p=1456

Fedorenko, A.Y., and F.J. Fraser. Review of Grass Carp biology. Fisheries and Environment Canada, 

Fisheries and Marine Service Technical Report No. 786. 16 pp. (1978).

Feiler, U., I. Kirchesch, and P. Heininger. A new plant-based bioassay for aquatic sediments. Journal of 

Soils and Sediments 4 (4): 261-266 (2004).

Feist, S.W., M. Longshaw, E.U. Canning, and B. Okamura. Induction of proliferative kidney disease 

(PKD) in Rainbow Trout Oncorhynchus mykiss via the bryozoan Fredericella sultana infected with 

Tetracapsula bryosalmonae. Diseases of Aquatic Organisms 45: 61-68 (2001).
1546

Feist, S.W., E.J. Peeler, R. Gardiner, E. Smith, and M. Longshaw. Proliferative kidney disease and renal 

myxosporidiosis in juvenile salmonids from rivers in England and Wales. Journal of Fish Disease 25: 

451-458 (2002).

Feldheim, K.A., P. Willink, J.E. Brown, D.J. Murphy, M.E. Neilson, and C.A. Stepien. Microsatellite loci 

for Ponto-Caspian gobies: markers for assessing exotic invasions. Molecular Ecology Resources 9 (2): 

639-644 (2009).

Felley, J.D., and L.G. Hill. Multivariate assessment of environmental preferences of Cyprinid fishes of 

the Illinois River, Oklahoma. American Midland Naturalist 109(2): 209-221 (1983).

Ferguson. Reproduction areas of Roach (Rutilus rutilus) in the northern Baltic Sea: potential effects of 

climate change. Canadian Journal of Fisheries and Aquatic Sciences 65: 2678-2688 (2008).

Fernández-Delgado, C., J.A. Hernando, M. Herrera, and M. Bellido. Life-history patterns of the 

sandsmelt Atherina boyeri Risso, 1810 in the estuary of the Guadalquivir River, Spain. Estuarine, 

Coastal, and Shelf Science 27: 697-706 (1988).

Ferreira, M.T., and I. Moreira. The seasonal evolution of river plants. European Weed Research Society 

9

th Symposium on Aquatic Weeds. Abstracts (1994).

Ferriter, A., D. Thayer, B. Nelson, T. Richards, and D. Girardin. Simberloff, D., D.C. Schmitz, and T.C. 

Brown (eds.). Strangers in paradise. Impact and management of nonindigenous species in Florida. Island 

Press, Washington D.C. 317-325 pp. (1997).

Fisher, B.E., S.P. Wente, T.P. Simon, and A. Spacie. The fishes of Tippecanoe County, Indiana. 

Proceedings of the Indiana Academy of Science 107: 151-166 (1998). 

Flora of North America Editorial Committee. Flora of North America North of Mexico, Vol. 22. Oxford 

University Press, New York, New York (2000). 

Florida Department of Environmental Protection (FDEP), Bureau of Invasive Plant Management. Status 

of the Aquatic Plant Maintenance Program in Florida Public Waters, Annual Report for Fiscal Year 2006-

2007. 67 pp. (2007)

Food and Agriculture Organization of the United Nations (FAO). Aquaculture production statistics: 1988-

1997. FAO Fisheries Circular 815, Revision 11. 203 (1999).

Food and Agriculture Organization of the United Nations (FAO). Sander lucioperca. Cultured Aquatic 

Species Information Programme (2012). http://www.fao.org/fishery/culturedspecies/Sander_lucioperca/en

Food and Agriculture Organization of the United Nations (FAO), Fisheries and Aquaculture Department. 

Carassius carassius (Linnaeus, 1758). Cultured Aquatic Species Information Programme (2013a). 

http://www.fao.org/fishery/culturedspecies/Carassius_carassius/en

Food and Agriculture Organization of the United Nations (FAO). Management of problematic aquatic 

weeds in Africa. Corporate Document Repository (2013b). 

http://www.fao.org/docrep/006/y4270e/y4270e03.htm
1547

Food and Agriculture Organization of the United Nations (FAO), Fisheries and Aquaculture Department. 

Sander lucioperca. Online Species Fact Sheets (2013c). http://www.fao.org/fishery/species/3098/en

Forester, T.S., and J.M. Lawrence. Effects of Grass Carp and Carp on Populations of Bluegill and 

Largemouth Bass in Ponds. Transactions of the American Fisheries Society 107(1): 172-175 (1978). 

Forward, R.B. Larval biology of the crab Rhithropanopeus harrisii (Gould): a synthesis. The Biological 

Bulletin (Lancaster) 216: 243-256 (2009).

Fowler, M.C., and T.O. Robson. The effects of the food preferences and stocking rates of Grass Carp 

(Ctenopharyngodon idella Val.) on mixed plant communities. Aquatic Botany 5(3): 261-276 (1978).

Fowler, A., T. Forsstrom, M. von Numers, and O. Vesakoski. The North American Mud Crab 

Rhithropanopeus harrisii (Gould, 1841) in newly colonized Northern Baltic Sea: distribution and 

ecology. Aquatic Invasions 8:89-96 (2013).

Frank, S. Acclimatization experiments with Amur Snakehead, Ophiocephalus argus warparchowskii

(Berg, 1909). Czechoslovakia: Vstník eskoslovenské Spolenosti Zoologické 34: 277-283 (1970).

Franzoi, P., R. Maccagnani, R. Rossi, and V.U. Ceccherelli. Life cycles and feeding habits of Syngnathus 

taenionotus and S. abaster (Pisces, Syngnathidae) in a brackish bay of the Po River Delta (Adriatic Sea). 

Marine Ecology Progress Series 87: 71-81 (1993).

Fraser, D., and C.E. Adams. A Crucian Carp Carassius carassius (L.) in Loch Rannoch, Scotland: further 

evidence of the threat posed to unique fish communities by introduction of alien fish species. Aquatic 

Conservation: Marsh and Freshwater Ecosystem 7: 323-326 (1997).

Frau, D., F. Rojas Molina, M. Devercelli, and S. Jose de Paggi. The effect of an invading filter-feeding 

bivalve on a phytoplankton assemblage from the Paraná system: a mesocosm experiment. Marine and 

Freshwater Behaviour and Physiology 45 (5): 303-316 (2013).

Freitas-Júnior, F., M.L. Christoffersen, J.P. De Araújo, and J.O. Branco. Spatio-temporal distribution and 

population structure of Monokalliapseudes schubarti (Tanaidacea: Kalliapseudidae) in an estuary in 

southern Brazil. The Scientific World Journal 2013: 363187 (2013).

Freyhof, J. Immigration and potential impacts of invasive freshwater fishes in Germany. Bergichte des 

IGB 17: 51-58 (2003).

Freyhof, J. and M. Kottelat. Atherina boyeri. In: IUCN 2013. IUCN Red List of Threatened Species. 

Version 2013.2 (2008a). http://www.iucnredlist.org/details/2352/0

Freyhof, J., and M. Kottelat. Blicca bjoerkna. The IUCN Red List of Threatened Species (2008b). 

http://www.iucnredlist.org/details/39270/0

Freyhof, J., and M. Kottelat. Knipowitschia caucasica. The IUCN Red List of Threatened Species

(2008c). www.iucnredlist.org

Freyhof, J. 2013. Leuciscus leuciscus. The IUCN Red List of Threatened Species (2013). 

http://www.iucnredlist.org/details/11887/0
1548

Frisch, D. Dormancy, dispersal and the survival of cyclopoid copepods (Cyclopoida: Copepoda) in a 

lowland floodplain. Freshwater Biology 47: 1269-1281 (2002).

Frisch, D., H. Rodriguez-Perez, and A.J. Green. Invasion of artificial ponds in Donana Natural Park, 

southwest Spain, by an exotic estuarine copepod. Aquatic Conservation-Marine and Freshwater 

Ecosystems 16: 483-492 (2006).

Fritz, B., A. Nisch, C. Wittkugel, and M. Mörtl. Erstfund von Limnomysis benedeni Czerniavsky im 

Bodensee (Crustacea: Mysidacea). Lauterbornia 58: 157-160 (2006).

Froese, R. Leuciscus idus (Linnaeus, 1758). FishBase (2013). 

http://www.fishbase.org/Summary/SpeciesSummary.php?ID=2801&genusname=Leuciscus&speciesname

=idus&AT=Leuciscus+idus&lang=English

Froese, R., and D. Pauly. FishBase. World wide web electronic publication (2015). www.fishbase.org. 

Frost, W.E. The natural history of the minnow, Phoxinus phoxinus. Journal of Animal Ecology 12 (2): 

139-162 (1943).

Fuller, P. Oncorhynchus keta. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. (2006).

Fuller, P. Esox lucius. USGS Nonindigenous Aquatic Species Database, Gainsville, FL (2013).

Fuller, P.L., L.G. Nico, and J.D. Williams. Nonindigenous Fishes Introduced into Inland Waters of the 

United States. Special Publication 27, American Fisheries Society. Bethesda, Maryland. 613 pp. (1999).

Fuller, P., M. Neilson, and D.H. Huge. The NAS alert system: A look at the first eight years. Fisheries 38 

(3): 128-138 (2013). 

Fuller, P., J. Larson, A. Fusaro, and M. Neilson. Salmo trutta. USGS Nonindigenous Aquatic Species 

Database, Gainesville, FL (2014). 

Fuller, P., and L. Nico. Cyprinella whipplei. USGS Nonindigenous Aquatic Species Database, Gainsville, 

FL (2015a).

Fuller, P., and M. Neilson. Ictalurus furcatus. USGS Nonindigenous Aquatic Species Database, 

Gainesville, FL. (2015b).

Funnell, E., M. Heaton, F. MacDonald, and B. Brownson. The aquarium and horticultural industry as a 

pathway for the introductino of aquatic invasive species- outreach initiatives within the Great Lakes 

basin. Biodiversity 10: 104-112 (2009).

Fusaro, A., A. Davidson, K. Alame, M. Gappy, and W. Conard. Osmerus eperlanus. USGS 

Nonindigenous Aquatic Species Database, Gainsville FL, and NOAA Great Lakes Aquatic 

Nonindigenous Species Information System, Ann Arbor, MI (2015). 

Gale, W.F. Fecundity and spawning frequency of caged Bluntnose Minnows- fractional spawners. 

Transactions of the American Fisheries Society 112 (3): 398-402 (1983).

Gale, W.F. Indeterminate fecundity and spawning behavior of captive Red Shiners- fractional, crevice 

spawners. Transactions of the American Fisheries Society 115 (3): 429-437 (1986).
1549

Gale, W.F., and G.L. Buynak. Fecundity and spawning frequency of the fathead minnow- a fractional 

spawner. Transactions of the American Fisheries Society 11: 35-40 (1982).

Galkovskaya, G.A., and D.V. Molotkov. Species diversity and dominance in the planktonic rotifer 

community of the Pripyat River in the Chernobly region (1988-1996). Hydrobiologia 446/447:179-185 

(2001).

García, C., S. Nandini, and S.S.S. Sarma. Seasonal dynamics of zooplankton in Lake Huetzalin, 

Xochimilco (Mexico City, Mexico). Limnologica- Ecology and Management of Inland Water 39 (4): 283-

291 (2009).

Garcia-Berthou, E. The characteristics of invasive fishes: what has been learned so far? Journal of Fish 

Biology 71(Supplement D): 33-55 (2007).

Gardiner, L.F. A Fresh- and Brackish-Water Tanaidacean, Tanais stanfordi Richardson, 1901, from a 

Hypersaline Lake in the Galapagos Archipelago, with a Report on West Indian Specimens. Crustaceana 

29: 127-140 (1975).

Gasiunaite, Z.R., D. Daunys, S. Olenin, and A. Razinkovas. The curonian lagoon. Schiewer, U. (ed.). 

Ecology of Baltic Coastal Waters. Springer-Verlag Berlin Heidelberg 197-215 pp. (2008).

Gasiunas, I. Acclimatisation of forage crustaceans into the Kaunas Waterpower Plant reservoir and 

possibility of their migration into other waters of Lithuania. Trudy Akademii Nauk Litovskoi SSR. Serija 

1 (30): 79-85 (1964).

Gauer, A., and C. Imesch. Invasive Arten. Management aquatischer Systeme. 16 pp. (2008).

Gay, M., B. Okamura, and P. de Kinkelin. Evidence that infectious stages of Tetracapsula bryosalmonae 

for rainbow trout Oncorhynchus mykiss are present throughout the year. Diseases of Aquatic Organisms 

46: 31-40 (2001).

Gaygusuz, Ö., C.G. Gaygusuz, A.S. Tarkan, H. Acipinar, and Z. Türer. Preference of Zebra 

Mussel, Dreissena polymorpha in the diet and effect on growth of gobiids: a comparative study between 

two different ecosystems. Ekoloji 17(65): 1-6 (2007).

Gazulha, V., M.C.D. Mansur, L.F. Cybis, and S.M.F.O. Azevedo. Grazing impacts of the invasive bivalve 

Limnoperna fortunei (Dunker, 1857) on single-celled, colonial and filamentous cyanobacteria. Brazilian 

Journal of Biology 72 (1): 33-39 (2012).

Geddes, M.C., and M. Smallridge. Survival, growth and yield of the Australian freshwater crayfish 

Cherax destructor in extensive aquaculture ponds. Aquaculture 114 (1-2):51-70 (1993).

Geldiay, R. and S. Balik. Türkiye Tatlisu Baliklari. Ege Ünv. Fen Fak. Kitaplar Serisi No: 97, Ege Ünv. 

Basimevi, Izmir, 519 pp. (1996).

Gendron, A.D., D.J. Marcogliese, and M. Thomas. Invasive species are less parasitized than native 

competitors, but for how long? The case of the Round Goby in the Great Lakes-St. Lawrence Basin. 

Biological Invasions 14: 367-384 (2012).
1550

Geng, H., P. Xie, D. Deng, and Q. Zhou. The Rotifer Assemblage in a Shallow, Eutrophic Chinese Lake 

and Its Relationships with Cyanobacterial Blooms and Crustacean Zooplankton. Journal of Freshwater 

Ecology 20: 93-103 (2005).

Georghiev, J.M. Composition d’espece et caracteristique des Gobiides (Pisces) en Bulgaria. Izvestija Na 

Naucoizsledovatel Skija Institut Za Ribno Stopanstvoo I Okeanografija Varna 7: 159-228 (1966).

Geraudie, P., M. Gerbron, E. Hill, and C. Minier. Roach (Rutilus rutilus) reproductive cycle: a study of 

biochemical and histological parameters in a low contaminated site. Fish Physiology Biochemistry 36: 

767-777 (2010).

Gergs, R., A.J. Hanselmann, I. Eisele, and K.O. Rothhaupt. Autecology of Limnomysis benedeni 

Czerniavsky, 1882 (Crustacea: Mysida) in Lake Constance, Southwestern Germany. LimnologicaEcology and Management of Inland Waters 38 (2): 139-146 (2008).

Ghabooli, S., A. Zhan, P. Sardina, E. Paolucci, F. Sylvester, P.V. Perepelizin, E. Briski, M.E. Cristescu, 

and H.J. MacIsaac. Genetic diversity in introduced Golden Mussel populations corresponds to vector 

activity. PLoS ONE 8 (3): e59328 (2013).

Gheorghiev, J.M. Some new and little known Bullheads (Gobiidae, Pisces) to Bulgarian ichthyofauna. 

Bulletin of the Institute of Piscatoria 4: 189-206 (1964). 

Gherardi, F. Biological invaders in inland waters: profiles, distribution, and threats. Springer, Dordrecht, 

Netherlands (2007). 

Gherardi, F., S. Gollasch, D. Minchin, S. Olenin, and V.E. Panov. Alien invertebrates and fish in 

European inland waters. Drake, J.A. (ed.). DAISIE Handbook of Alien Species in Europe. Springer, 

Dordrrecht 81-92 pp. (2009).

Gibbs, R.H.J. Cyprinid fishes of the subgenus Cyprinella of Notropis I. Life Sciences: 185-195 (1957).

Gibbs, R.H.J. Cyprinid fishes of the subgenus Cyprinella of Notropis. Copeia: 511-528 (1963).

Glasby, G.P., and P. Szefer. Marine pollution in Gdansk Bay, Puck Bay and the Vistula Lagoon, Poland: 

An overview. Science of The Total Environment 212: 49-57 (1998).

Global Biodiversity Information Facility (GBIF). (2010). http://www.gbif.org/

Global Invasive Species Database (GISD). Ctenopharyngon idella (2005a). 

http://www.issg.org/database/species/ecology.asp?si=369&fr=1&sts=sss&lang=EN

Global Invasive Species Database (GISD). Hygrophila polysperma (2005b). 

http://www.issg.org/database/species/ecology.asp?si=759&fr=1&sts=sss&lang=EN

Global Invasive Species Database (GISD). Hypophthalmichthys nobilis (2005c). 

http://www.issg.org/database/species/ecology.asp?si=773&fr=1&sts=sss&lang=EN

Global Invasive Species Database (GISD). Hydrilla verticillata (2006a). 

http://www.issg.org/database/species/ecology.asp?si=272
1551

Global Invasive Species Database (GISD). Hypophthalmichthys molitrix (2006b). 

http://www.issg.org/database/species/ecology.asp?si=774&fr=1&sts=sss&lang=EN

Global Invasive Species Database (GISD). Rhithropanopeus harrisii (2008).

http://www.issg.org/database/species/ecology.asp?si=1217&fr

Global Invasive Species Database (GISD). Leuciscus idus (2010). 

http://www.issg.org/database/species/ecology.asp?si=613

Global Invasive Species Database (GISD). Perca fluviatilis (2012). 

http://www.issg.org/database/species/ecology.asp?si=548&fr=1&sts=sss&lang=EN

Godfrey, R.K., and J.W. Wooten. Aquatic and wetland plants of southeastern United States, 

Monocotyledons. University of Georgia, Athens, GA (1979). 

Gollasch, S. The importance of ship hull fouling as a vector of species introduction in the North Sea. 

Biofouling 18: 105-121 (2002).

Gollasch, S., and S. Nehring. National checklist for aquatic alien species in Germany. Aquatic Invasions 1 

(4): 245-269 (2006).

Golovanov, V.K., and A.B. Ruchin. Critical thermal maximum of Amur Sleeper Perccottus glenii in 

different seasons of the year. Journal of Ichthyology 51 (9): 788-793 (2011).

Golovanov, V.K., D.S. Kapshai, Y.V. Gerasimov, I.L. Golovanova, D.P. Karabanov, A.K. Smirnov, and 

I.V. Shlyapkin. Thermopreference and thermostability of the Amur Sleeper juveniles Perccottus glenii in 

Autumn. Journal of Ichthyology 53 (3): 240-244 (2013).

Gonҫalves, F., R. Ribeiro, and A.V.M. Soares. Rhithropanopeus harrisii, an American crab in the estuary 

of the Modego River, Portugal. Journal of Crustacean Biology 15(4): 756-762 (1995).

Gonzalez, M., and G.A. Burkart. Effects of food type, habitat, and fish predation on the relative 

abundance of two amphipod species Gammarus fasciatus and Echinogammarus ischnus. Journal of Great 

Lakes Research 30: 100-113 (2004).

Goodchild, C.D. Grass Carp. Non-indigenous freshwater fish utilized in the live food fish industry in 

Ontario. Ontario Ministry of Natural Resources (1999).

Goodwin, A.E. Massive Lernaea cyprinacea infestations damaging the gills of Channel Catfish 

polycultured with Bighead Carp. Journal of Aquatic Animal Health 11: 406-408 (1999).

Gordon, D.R., C.A. Gantz, C.L. Jerde, W.L. Chadderton, R.P. Keller, and P.D. Champion. Weed Risk 

Assessment for Aquatic Plants: Modification of a New Zealand System for the United States. PLoS One 7 

(7): e40031 (2012).

Gosner, K.L. A field guide to the Atlantic seashore. Houghton Mifflin. Boston, Massachusetts (1979).

Goto, Y. Behavior of nuisance mussel, Limnoperna fortunei, in water supply facilities. Water Science and 

Technology 46 (11-12): 45-50 (2002).
1552

Goulletquer, P., G. Bachelet, P.G. Sauriau, and P. Noel. Open Atlantic coast of Europe- A century of 

introduced species into French waters. Leppäkoski, E., S. Gollasch, and S. Olenin (eds.). Invasive aquatic 

species of Europe. Distribution, impacts, and management. Springer 276-290 pp. (2002).

Government of Canada. Ballast water control and management regulations. Canada Gazette 140 (13) 

(2006).

Goździejewska, A., and S. Tucholski. Zooplankton of fish culture ponds periodically fed with treated 

wastewater. Polish Journal of Environment Studies 20 (1)67-79 (2011).

Gozlan, R.E., A.C. Pinder, and J. Shelley. Occurrence of the Asiatic cyprinid Pseudorasbora parva in 

England. Journal of Fish Biology 61: 298-300 (2002).

Gozlan, R.E., S. St-Hilaire, S.W. Feist, P. Martin, and M.L. Kent. Biodiversity: disease threat to European 

fish. Nature 435 (7045): 1046 (2005).

Gozlan, R.E., C.M. Whipps, D. Andreou, and K.D. Arkush. Identification of a rosette-like agent as 

Sphaerothecum destruens, a multi-host fish pathogen. International Journal for Parasitology 39 (10): 

1055-1058 (2009).

Gozlan, R.E., D. Andreou, T. Asaeda, K. Beyer, and R. Bouhadad. Pan-continental invasion of 

Pseudorasbora parva: towards a better understanding of freshwater fish invasions Pan-continental 

invasion of Topmouth Gudgeon. Fish and fisheries (Oxford, England) 11 (4): 315-340 (2010a).

Gozlan, R.E., J.R. Britton, I. Cowx, and G.H. Copp. Current knowledge on non-native freshwater fish 

introductions. Journal of Fish Biology 76: 751-786 (2010b).

Grabowska, J. Reproductive biology of racer goby Neogobius gymnotrachelus in the Wloclawski 

Reservoir (Vistula River, Poland). J. Appl. Ichthyol. 21: 296-299 (2005).

Grabowska, J. Perccottus glenni (Amur sleeper). Centre for Agricultural Bioscience International (CABI) 

(2011). http://www.cabi.org/isc/datasheet/110577

Grabowska, J. and M. Grabowski. Indications on the diel feeding activity in early summer of racer 

goby Neogobius gymnotrachelus (Gobiidae) – a new invader in the Baltic Basin. J. Appl. Ichthyol. 21: 

282-286 (2005).

Grabowska, J., M. Grabowski, and A. Kostecka. Diet and feeding habits of Monkey Goby (Neogobius 

fluviatilis) in a newly invaded area. Biological Invasions 11(9): 2161-2170 (2009).

Grabowska, J., J. Kotusz, and A. Witkowski. Alien invasive fish species in Polish waters: an overview. 

Folia Zoologica 59: 73-85 (2010).

Grabowska, J., P. Dariusz, P. Miroslaw, T.A. Serhan, M. Lidia, and L.K. Magdalena. Life-history traits of 

Amur Sleeper, Perccottus glenii, in the invaded Vistula River: early investment in reproduction but 

reduced growth rate. Hydrobiologia 661: 197-210 (2011).

Grabowski, M. Invasive Alien Species Fact Sheet - Pontogammarus robustoides. Online Database of the 

European Network on Invasive Alien Species (NOBANIS) (2011). 

http://www.nobanis.org/speciesInfo.asp?taxaID=965
1553

Grabowski, M., and K. Bącela. First finding of the Ponto-Caspian gammarid species Pontogammarus 

robustoides and Dikerogammarus haemobaphes (Crustacea, Amphipoda) in the post-glacial lake of the 

Vistula valley. Lauterbornia 55: 107-111 (2005).

Grabowski, M., K. Jażdżewski, and A. Konopacka. Alien crustacea in Polish waters-- introduction and 

decapoda. Oceanological and Hydrobiological Studies 34: 43-61 (2005).

Grabowski, M., A. Konopacka, K. Jażdżewski, and E. Janowska. Invasions of alien gammarid species and 

retreat of natives in the Vistula Lagoon (Baltic Sea, Poland). Helgoland Marine Research 60 (2): 90-97 

(2006).

Grabowski, M., K. Bacela, and A. Konopacka. How to be an invasive gammarid (Amphipoda: 

Gammaroidea)–comparison of life history traits. Hydrobiologia 590 (1): 75-84 (2007a).

Grabowski, M., K. Jażdżewski, and A. Konopacka. Alien Crustacea in Polish waters – Amphipoda. 

Aquatic Invasions 1 (2): 25-38 (2007b).

Graham, K., E. Irwin, W. Hubert, and C. Rabeni. A review of the biology and management of Blue 

Catfish. Catfish 2000: Proceedings of the International Ictalurid Symposium. American Fisheries Society 

37-49 pp. (1999).

Granqvist, M., and J. Mattila. The effects of turbidity and light intensity on the consumption of mysids by 

juvenile perch. Hydrobiologia 514: 93-101 (2004).

Grant, J.C., and H.R. Robinette. Commercially important traits of Blue and Channel Catfish as related to 

second summer, winter, and third summer growth. Aquaculture 105: 37-45 (1992).

Gray, D.K., and H.J. MacIsaac. Diapausing zooplankton eggs remain viable despite exposure to openocean ballast water exchange: evidence from in-situ exposure experiments. Canadian Journal of 

Fisheries and Aquatic Sciences 67: 1-11 (2010).

Gray, D.K., S.A. Bailey, I.C. Duggan, and H.J. MacIsaac. Viability of invertebrate diapausing eggs 

exposed to saltwater: implications for Great Lakes’ ship ballast management. Biological Invasions 7 (3):

531-539 (2005).

Gray, D.K., T.H. Johengen, D.F. Reid, and H.J. MacIsaac. Efficacy of open-ocean ballast water exchange 

as a means of preventing invertebrate invasions between freshwater ports. Limnology and Oceanography

52: 2386-2397 (2007).

Great Lakes Panel on Aquatic Nuisance Species (GLPANS). Prohibited species in the Great Lakes region. 

Research Coordination Committee, GLPANS (2012). https://www.michigan.gov/documents/deq/wrd-aisregulated-species_390473_7.pdf.

Greenhalgh, M. Freshwater Fish. Mitchell Beazley, London (1999).

Grieve, M.M. A modern herbal. Penguin (1984).

Griffiths, D. The status of the Irish freshwater fish fauna: A review. Journal of Applied Ichthyology 13:9-

13 (1997).
1554

Grift, R.E., A.D. Buijse, W.L.T. Van Densen, and J.G.P. Klein Breteler. Restoration of the riverfloodplain interaction: benefits for the fish community in the River Rhine. Archiv fur Hydrobiologie 

Supplement 135(2-4): 173-185 (2001).

Grigorovich, I.A., and H.J. Macisaac. First record of Corophium mucronatum Sars (Crustacea: 

Amphipoda) in the Great lakes. Journal of Great Lakes Research 25 (2): 401-405 (1999).

Grigorovich, I.A., R.I Colautti, E.L. Mills, K. Holeck, A.G. Ballert, and H.J. MacIsaac. Ballast-mediated 

animal introductions in the Laurentian Great Lakes: retrospective and prospective analyses. Can. J. Fish. 

Aquat. Sci. 69: 740-756 (2003).

Grigorovich, I.A., T.R. Angradi, E.B. Emery, and M.S. Wooten. Invasion of the Upper Mississippi River 

system by saltwater amphipods. Fundamental and Applied Limnology/Archiv für Hydrobiologie 173: 67-

77 (2008).

Gröger, J.P., H. Winkler, and R.A. Rountree. Population dynamics of Pikeperch (Sander lucioperca) and 

its linkage to fishery driven and climatic influences in a southern Baltic lagoon of the Darss-Zingst 

Bodden Chain. Fisheries Research 84:189-201 (2007).

Gruia, L., and D. Manoleli. Considerations sur le role des algues dans la nourritue des Polychetes reliques 

ponto-caspiens du Danube. Travaux du Musée d’Histoire Naturelle Grigore Antipa 15: 23-30 (1974).

Guan, R., and P.R. Wiles. Ecological impact of introduced crayfish on benthic fishes in a British lowland 

river. Conservation Biology 11(3): 641-647 (1997).

Guier, C.R., L.E. Nichols, and R.T. Rachels. Biological investigations of Flathead Catfish in the Cape 

Fear River. Proceedings of the Southeastern Association of Fish and Wildlife Agencies 35:607-621 

(1984).

Gülle, I., M. Yildirim, and F. Küçük. Limnological history of Lake Eğirdir (Turkey) from 1950s to the 

present. Natura Montenegrina, Podgorica 7 (2): 115-128 (2008). 

Guti, G. Gobies in the lower section of the River Tisa. Halászat 87 (3): 133 (1999).

Guti, G. Dispersion of Ponto-Caspian gobiid fish (Gobiidae) in the middle Danubian basin. Hidrológiai 

Kŏzlemények 80 (5): 303-305 (2000).

Guti, G. First record of Racer Goby Neogobius gymnotrachelus (Pallas, 1811) in the Hungarian section of 

the Danube. Opuscula Zoologica Budapest 35: 83-84 (2006).

Gutiérrez, E.L., E.F. Ruiz, E.G. Uribe, and J.M. Martinez. Biomass and productivity of Water Hyacinth 

and their application in control programs. Julien, M.H., M.P. Hill, T.D. Center, and D. Jianqing (eds.). 

Biological and integrated control of water hyacinth, Eichhornia crassipes. Australian Centetre for 

International Agriculture Research (ACIAR) Proceedings 102 109-119 pp. (2001).

Haenen, O.L.M., P. van Banning, and W. Dekker. Infection of eel Anguilla anguilla (L.) and Smelt 

Osmerus eperlanus (L.) with Anguillicola crassus (Nematoda, Dracunculoidea) in the Netherlands from 

1986 to 1992. Aquaculture 126: 219-229 (1994).
1555

Haertl, M., A. Cerwenka, J. Brandner, J. Borcherding, J. Geist, and U.K. Schliewen. First record of Babka 

gymnotrachelus (Kessler, 1857) from Germany. Spixiana 35(1): 155-159 (2012).

Halasi-Kovács, B., L. Antal, and S.A. Nagy. First record of a Ponto-caspian Knipowitschia species 

(Gobiidae) in the Carpathian basin, Hungary. Cybium 35:257-258 (2011).

Hale, S.S., T.E. McMahon, and P.C. Nelson. Habitat suitability index models and instream flow 

suitability curves: Chum Salmon. United States Fish and Wildlife Service Biological Report 82 (10.108). 

48 pp. (1985).

Haller, W.T., and D.L. Sutton. Community structure and competition between Hydrilla and Vallisneria. 

Hyacinth Control Journal 13: 48-50 (1975).

Hamburger, B., H. Haberling, and H.R. Hitz. Comparative tests on toxicity to fish using minnow, trout, 

and golden orfe. Archiv fur Fischereiwissenschaft 28: 45-55 (1977).

Hamrin, S. Biomass of tench, perch, crucian carp and pike in a small eutrophic lake in southern Sweden. 

Jyvăskylăn yliopiston biologian laitoksen tiedonantoja 19: 57-65 (1979).

Hänfling, B., P. Bolton, M. Harley, and G.R. Carvalho. A molecular approach to detect hybridization 

between Crucian Carp (Carassius carassius) and non-indigenous carp species (Carassius spp. and 

Cyprinus carpio). Freshwater Biology 50(3): 403-417 (2005).

Hänfling, B. and D. Weetman. Concordant genetic estimators of migration reveal anthropogenically 

enhanced source-sink populations structure in the river sculpin, Cottus gobio. Genetics 173: 1487-1501

(2006).

Hänfling, B., F. Edwards, and F. Gherardi. Invasive alien Crustacea: dispersal, establishment, impact, and 

control. Biocontrol 56: 573-595 (2011).

Hanselmann, A.J., R. Gergs, and K.O. Rothhaupt. Seasonal shifts in the life cycle of the ponto-caspian 

invader Limnomysis benedeni (Crustacea: Mysida): a physiological adaptation? Hydrobiologia 673: 193-

204 (2011). 

Hansson, S., F. Arrhenius, and S. Nellbring. Benefits from fish stocking—experiences from stocking 

young-of-the-year Pikeperch, Stizostedion lucioperca L., to a bay in the Baltic Sea. Fisheries Research

32:123-132 (1997).

Haramoto, T., and I. Ikusima. Life cycle of Egeria densa Planch., an aquatic plant naturalized in Japan. 

Aquatic Botany 30: 389-403 (1988).

Harka, Á. and P. Bíró, P. New patterns in Danubian distribution of Ponto-Caspian gobies – a result of 

global climatic change and/or canalization? Electronic Journal of Ichthyology 1: 1-14 (2007).

Harlioglu, M.M., and A.G. Harlioglu. Threat of non-native crayfish introductions in to Turkey: global 

lessons. Reviews in Fish Biology and Fisheries 16: 171-181 (2006).

Härmä, M., A. Lappalainen, and L. Urho. Reproduction areas of Roach (Rutilus rutilus) in the northern 

Baltic Sea: potential effects of climate change. Canadian Journal of Fisheries and Aquatic Sciences 65: 

2678-2688 (2008).
1556

Harmer, S.F. The Polyzoa of waterworks. Proceedings of the Zoological Society of London 31: 246-257 

(1913).

Harmeson, R.H., and V.M. Schnepper. Temperatures of surface waters in Illinois. Illinois State Water 

Survey (1965). 

Harris, R. Amphipod also invades Britain. Nature 354: 194 (1991).

Harris, M.T. and A.W. Wheeler. Ligula infestation of bleak Alburnus alburnus (L.) in the tidal Thames. 

Journal of Fish Biology 6 (2): 181-188 (1974).

Harris, R., and D. Bayliss. Osmoregulation in Corophium curvispinum (Crustacea: Amphipoda), a recent 

coloniser of freshwater. Journal of Comparative Physiology B: Biochemical, Systemic, and 

Environmental Physiology 160 (1): 85-92 (1990).

Harris, R., and N. Aladin. The ecophysiology of osmoregulation in Crustacea. Ionic regulation in animals. 

Springer, Berlin. 25 pp. (1997).

Harris, R., and I. Muskó. Oxygen consumption, hypoxia, and tube-dwelling in the invasive amphipod 

Corophium curvispinum. Journal of Crustacean Biology 19 (2): 224-234 (1999).

Hartikainen, H., P. Johnes, C. Moncrieff, and B. Okamura. Bryozoan populations reflect nutrient 

enrichment and productivity gradients in rivers. Freshwater Biology 54: 2320-2334 (2009).

Hartis, B.M. Lake Environment Hydrilla, Part 2- Impacts. Kerr Lake Guide: Everything about the Lake 

(2013). http://www.kerrlakeguide.com/node/429

Hartley, P. H. T. The Natural History of some British Freshwater Fishes. Proceedings of the Zoological 

Society of London 117:129-206 (1947).

Harvey, C.J., P.E. Moriarty, and E.P. Salathé. Modeling climate change impacts on overwintering Bald 

Eagles. Ecology and Evolution 2(3): 501-514 (2012).

Hauenstein, E., and C. Ramirez. The influence of salinity on the distribution of Egeria densa in the 

Valdivia river basin, Chile. Archiv für Hydrobiologie 107 (4): 511-519 (1986).

Havel, J.E., K.A. Medley, K.D. Dickerson, T.R. Angradi, D.W. Bolgrien, P.A. Bukaveckas, and T.M. 

Jicha. Effect of main-stem dams on zooplankton communities of the Missouri River (USA). 

Hydrobiologia 628: 121-135 (2009).

Havey, K.A. Effects of a Smelt introduction on growth of landlocked salmon at Schoodic Lake, Maine. 

Transactions of the American Fisheries Society 102 (2):392-397 (1973).

Hawaii Pacific Weed Risk Assessment. Hygrophila polysperma (2012). www.hpwra.org.

Hayden, T.A. and J.G Miner. Rapid dispersal and establishment of benthic Ponto-Caspian goby in Lake 

Erie: diel vertical migration of early juvenile round goby. Biological Invasions 11: 1767-1776 (2009).

Hayes, D.B., and D.C. Caroffino (eds.). Michigan’s Lake Sturgeon rehabilitation strategy. Michigan 

Department of Natural Resources, Fisheries Special Report 62, Lansing, MI (2012).
1557

Hearnden, M.N., and B.H. Kay. Importance of Hydrilla verticillata (Hydrocharitaceae) as habitat for 

immature mosquitoes at the Ross River Reservoir, Australia. Journal of the American Mosquito Control 

Association 13: 164-170 (1997).

Hecky, R.E., R.E.H. Smith, D.R. Barton, S.J. Guilford, W.D. Taylor, M.N. Charlton, and T. Howell. The 

nearshore phosphorous shunt: a consequence of ecosystem engineering by dreissenids in the Laurentian 

Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 61: 1285-1293 (2004).

Hedrick, R.P., E. MacConnell, and P. de Kinkelin. Proliferative Kidney Disease of salmonid fish. Annual 

Review of Fish Disease 3: 277-290 (1993).

Hegele-Drywa, J., and M. Normant. Feeding ecology of the American crab Rhithropanopeus harrisii

(Crustacea, Decapoda) in the coastal waters of the Baltic Sea. Oceanologia 51: 361-375 (2009).

Heikinheimo, O., P. Valkeajarvi, and H. Helminen. Interactions between Brown Trout, vendace and the 

fishery in Lake Paijanne. Archiv fur Hydrobiologie, Special Issues Advanced Limnology 57: 601-613 

(2002).

Helawell, J.M. The ecology of populations of Dace, Leudscus leuciscus (L.), from two tributaries of the 

River Wye, Herefordshire, England. Freshwater Biology 4 (6): 577-604 (1974).

Henderson, S. An evaluation of the filter feeding fishes, Silver and Bighead Carp, for water quality 

improvement. Smitherman, R.O., W.L. Shelton, and J.H. Grover (eds.). Culture of exotic fishes 

symposium proceedings. Fish Culture Section, American Fisheries Society, Auburn, Alabama 121-136 

pp. (1978).

Henderson, S. An evaluation of filter feeding fishes for removing excessive nutrients and algae from 

wastewater. United States Environmental Protection Agency, EPA-600/2-83-019. 5 (1983).

Henderson, J.E. Use of economic information in the evaluation of aquatic plant control programs: The 

Lake Guntersville recreation study. Miscellaneous Paper A-95-3. United States Army Engineer 

Waterways Experiment Station, Vicksburg, Mississippi. USA 8-18 pp. (1995).

Henderson, P.A. and R.N. Bamber. On the reproductive biology of the sand smelt Atherina boyeri Risso 

(Pisces: Atherinidae) and its evolutionary potential. Biological Journal of the Linnean Society 32: 395-

415 (1987).

Hendrickx, M., and S. Ibarra. Presence of Sinelobus stanfordi (Richardson, 1901) (Crustacea: Tanaidacea: 

Tanaidae) in coastal lagoons of western Mexico. Nauplius 16:79-82 (2008).

Hensler, S.R. and D.J. Jude. Diel vertical migration of round goby larvae in the Great Lakes. J. Great 

Lakes Res. 33: 295-302 (2007).

Herborg, L., N.E. Mandrak, B.C. Cudmore, and H.J. MacIsaac. Comparative distribution and invasion 

risk of snakehead (Channidae) and Asian carp (Cyprinidae) species. North America. Canadian Journal of 

Fisheries and Aquatic Sciences 64: 1723-1735 (2007).

Herkül, K., J. Kotta, T. Püss, and I. Kotta. Crustacean invasions in the Estonian coastal sea. Estonian 

Journal of Ecology 58 (4): 313-323 (2009).
1558

Herodek, S., I. Tátrai, J. Oláh, and L. Vörös. Feeding experiments with Silver Carp (Hypophthalmichthys 

molitrix Val.) fry. Aquaculture 83: 331-344 (1989).

Hessen, D.O., T. Andersen, and B. Faafeng. Replacement of herbivore zooplankton species along 

gradients of ecosystem productivity and fish predation pressure. Canadian Journal of Fisheries and 

Aquatic Sciences 52 (4): 733-742 (1995).

Hesthagen, T., and O.T. Sandlund. NOBANIS- Invasive Alien Species Fact Sheet Phoxinus phoxinus. 

Online database of the European Network on Invasive Alien Species- NOBANIS (2010). 

www.nobanis.org

Hickley, P., and S. Chare. Fisheries for non-native species in England and Wales: angling or the 

environment? Fisheries Management and Ecology 11 (3-4): 203-212 (2004).

Hliwa, P.A., K.D. Martyniak, and A. Sebestyen. Food preferences of juvenile stages of Pseudorasbora 

parva (Schlegel, 1842) in the Kis-Balaton Reservoir. Archives of Polish Fisheries 10: 121-127 (2002).

Hobaek, A., J.E. Løvik, T. Rohrlack, S.J. Moe, M. Grung, H. Bennion, G. Clarke, and G.T. Piliposyan. 

Eutrophication, recovery, and temperature in Lake Mjøsa: detecting trends with monitoring data and 

sediment records. Freshwater Biology 57: 1998-2014 (2012).

Hocutt, C.H., and E.O. Wiley. The Zoogeography of North American freshwater fishes. Wileyinterscience. 866 pp. (1986)

Hoff, M. Asian carp: huge fish with huge impacts. Aquatic Nuisance Species Digest 5(3): 25-28 (2004).

Hogan, L.S., E. Marschall, C. Folt, and R.A. Stein. How non-native species in Lake Erie influence

trophic transfer of mercury and lead to top predators. Journal of Great Lakes Research 33(1):46-61 

(2007).

Hokanson, K.E.F. Temperature requirements of some percids and adaptations to seasonal temperature 

cycle. Journal of the Fisheries Research Board of Canada 34: 1524-1550 (1977).

Holčík, J. Fish introductions in Europe with particular references to its central and eastern part. Canadian 

Journal of Fisheries and Aquatic Sciences 48: 13-23 (1991).

Holčík, J. Changes in the fish fauna and fisheries in the Slovak section of the Danube River: A review. 

Annales de Limnologie- International Journal of Limnology 39 (3): 177- 195 (2003).

Holdich, D.M., and M. Pöckl. Invasive crustaceans in European inland waters. Biological invaders in 

inland waters: profiles, distribution and threats. Springer Netherlands 29-77 pp. (2007). 

Holeck, K.T, E.L. Mills, H.J. MacIsaac, M.R. Dochoda, R.I. Colautti, and A. Ricciardi. Bridging troubled 

waters: biological invasions, transoceanic shipping, and the Laurentian Great Lakes. BioScience 54 (10): 

919-929 (2004).

Holley, M.P., M.D. Marshall, and M.J. Maceina. Fishery and population characteristics of Blue Catfish 

and Channel Catfish and potential impacts of minimum length limits on the fishery in Lake Wilson, 

Alabama. North American Journal of Fisheries Management 29: 1183-1194 (2009). 

Holm, L.G. The world's worst weeds: distribution and biology. Krieger Pub Co. (1991). 
1559

Holopainen, I.J., and H. Hyvärinen.mEcology and physiology of Crucian Carp (Carassius carassius L.) 

in small Finnish ponds with anoxic conditions in winter. Verhandlungen. Internationale Vereiningung fur 

theoretische und angewandte Limnology 22 (4): 2566-2570 (1984).

Holopainen, I.J., and A. Ikari. Ecophysiological effects of temporary acidification on Crucian Carp, 

Carassius carassius (L.): a case history of a forest pond in eastern Finland. Annales Zoologici Fennici 29: 

29-38 (1992).

Holopainen, I.J., W.M. Tonn, and C.A. Paszkowski. Tales of two fish: the dichotomous biology of 

Crucian Carp (Carassius carassius (L.)) in northern Europe. Annales Botanici Fennici 34: 1-22 (1997).

Holst, H, H. Zimmermann, H. Kausch, and W. Koste. Temporal and Spatial Dynamics of Planktonic 

Rotifers in the Elbe Estuary during Spring. Estuarine, Coastal and Shelf Science 47: 261-273 (1998).

Holt, L., and J. Farwick. Northern Snakehead Channa argus eradication in Piney and Little Piney creeks, 

Arkansas. Arkansas Game and Fish Commission (2009).

Holtan, H. Temperature distribution and water circulation in Lake Mjøsa. International Association of 

Hydrological Sciences, Proceedings of Helinski Symposium 109: 42-48 (1973). 

Homer, M.D., and C.A. Jennings. Historical catch, age and size structure, and relative growth for an 

introduced population of Blue Catfish (Ictalurus furcatus) in Lake Oconee, Georgia. Michaletz, P.H., and 

V.H. Travnichek (eds.). Conservation, Ecology, and Management of Catfish: The Second International 

Symposium. American Fisheries Society, Symposium 77, Betheseda, MD. 383-394 pp. (2011).

Hoole, D., D. Bucke, P. Burgess, and I. Wellby. Diseases of carp and other cyprinid fishes. Blackwell 

Science, Ames, Iowa (2001).

Horan, R.D., and F. Lupi. Tradable risk permits to prevent future introductions of alien invasive species 

into the Great Lakes. American Agricultural Economics Association Annual Meeting, Montreal, Canada, 

July 27-30, 2003 (2003).

Horoszewics, L. Lethal and ‘disturbing’ temperatures in some species from lakes with normal and 

artificially elevated temperature. Journal of Fish Biology 5(2): 165-181 (1973).

Horppila, J., and T. Kairesalo. A fading recovery: the role of Roach (Rutilus rutilus L.) in maintaining 

high phytoplankton productivity and biomass in Lake Vesijärvi, southern Finland. Hydrobiologia 200-

201: 153-165 (1990).

Horppila, J., and T. Kairesalo. Impacts of Bleak (Alburnus alburnus) and Roach (Rutilus rutilus) on water 

quality, sedimentation, and internal nutrient loading. Hydrobiologia 243-255(1): 323-331 (1992).

Horppila, J., J. Ruuhijärvi, M. Rask, C. Karppinen, K. Nyberg, and M. Olin. Seasonal changes in the diets 

and relative abundances of Perch and Roach in the littoral and pelagic zones of a large lake. Journal of 

Fish Biology 56: 51-72 (2000)

Hoshovsky, M.C., and L. Anderson. Egeria densa Planchon. in Bossard, C.C., J.M. Randall, and M.C. 

Hoshovky (eds.), 1st edition. Invasive Plants of California’s Wildlands. Pickleweek Press, Santa Rosa, CA 

(2001).
1560

Howard, G.W., and K.L.S. Harley. How do floating aquatic weeds affect wetland conservation and 

development? How can these effects be minimised? Wetlands Ecology and Management 5: 215-225

(1997).

Howells, R.G. Guide to identification of harmful and potentially harmful fishes, shellfishes and aquatic 

plants prohibited in Texas. Texas Parks and Wildlife Department Special Publication, Austin, TX. 182 

pp. (+ appendices) (1992).

Howells, R.G. Introduced non-native fishes and shellfishes in Texas waters: An updated list and 

discussion. Texas Parks and Wildlife Department, Inland Fisheries Division (2001).

Hoyer, M.V., D.E. Canfield, Jr., C.A. Horsburgh, and K. Brown. Florida freshwater plants: A handbook 

of common aquatic plants in Florida Lakes. University of Florida, Institute of Food and Agricultural 

Science, Gainesville, Florida. 264 pp. (1996)

Hrabik, T.R., J.J. Magnson, and A.S. McLain. Predicting the effects of Rainbow Smelt on native fishes is 

small lakes: evidence from long-term research on two lakes. Canadian Journal of Fisheries and Aquatic 

Sciences 55: 1364-1371 (1998). 

Hubbs, C.L., and J. C. Salyer. Examination of nursery lakes, pike hatcheries, rearing ponds, and minnow 

lakes in present operation in Iowa. Institute for Fisheries Research, Division of Fisheries, Michigan 

Department of Conservation. Lansing, Michigan. 47 pp. (1933)

Hubbs, C.L., and G.P. Cooper. Minnows of Michigan. Cranbrook Institute of Science, Bloomfield Hills, 

Michigan. 95 pp. (1936).

Hudson, P.L., J.W. Reid, L.T. Lesko, and J.H. Selgeby. Cyclopoid and harpacticoid copepods of the 

Laurentian Great Lakes. Ohio Biological Survey Bulletin New Series 12: 1-50 (1998).

Humpback Chub Ad Hoc Advisory Committee. Status and management strategy for Humpback Chub in 

Grand Canyon. Prepared at the request of the Adaptive Management Work Group of the Grand Canyon 

Adaptive Management Program, United States Geological Survey, Flagstaff, Arizona. 12pp. (2003).

Hussner, A., C. Meyer, and J. Busch. The influence of water level and nutrient availability on growth and 

root system development of Myriophyllum aquaticum. Weed Research 49: 73-80 (2009).

Hussner, A., K. Van De Weyer, E.M. Gross, and S. Hilt. Comments on increasing number and abundance 

of non-indigenous aquatic macrophyte species in Germany. Weed Research 50: 519-526 (2010).

Hussner, A., P. Heidbuechel, and S. Heiligtag. Vegetative overwintering and viable seed production 

explain the establishment of invasive Pistia stratiotes in the thermally abnormal Erft River (North RhineWestphalia, Germany). Aquatic Botany 119: 28-32 (2014).

Hutchinson, P. A note recording the occurrence of hermaphroditic Smelt, Osmerus eperlanus (L.) from 

the River Thames, England. Journal of Fish Biology 23:241-243 (1983).

Hutchinson, P., and D.H. Mills. Characteristics of spawning-run Smelt, Osmerus eperlanus (L.), from a 

Scottish river, with recommendations for their conservation and management. Aquaculture Research. 18 

(3): 29-258 (1987).
1561

Hutchinson, M.J., and P.H. Armstrong. The invasion of a south-western Australian river system by Perca 

fluviatilis: history and probable causes. Global Ecology Biogeography Letters 3: 77-89 (1993).

Hydrilla Workshop. Hydrilla verticillata, United States Army Corps of Engineers, Research and 

Development Center, Aquatic Plant Control Research Program. Hydrilla Sympsoium (2012).

Ieshko, E.P., N.V. Evseeva, and O.P. Sterligova. The role of fish parasites in fresh-water ecosystems 

exemplified by a parasite of the Smelt (Osmerus eperlanus). Parazitologiia 34(2): 118-124 (2000).

Iftime, A., and V. Tatole. Limnomysis benedeni (Czerniavski, 1882) (Crustacea: Peracarida: Mysidacea) 

in the Taita dam lake (Dobrogea, Romania). Travaux du Muséum national d'Histoire naturelle 49: 29-33 

(2006).

Illinois Database of Aquatic Non-native Species. 2014. Loyola University, Chicago, IL (2014). 

http://www.niiss.org/cwis438/websites/GISINDirectory/Occurrence_Info.php?GISIN_OccurrenceID=462

5244&CallingPage=%2Fcwis438%2Fwebsites%2FGISINDirectory%2FOccurrence_Result.php%3FTake

Action%3DReturned%26ProjectID%3D391%26GISIN_InsertLogID%3D0%26ScientificName%3Degeri

a+densa%26Kingdom%3D0%26Country_AreaID%3D0%26CurrentRow%3D20%26TotalRows%3D22&

CallingLabel=To%20Occurrence%20Search%20Results&WebSiteID=4

Illinois-Indiana Sea Grant (IISG). N.d. Aquatic Invasive Species. http://www.iisgcp.org/topic_ais.php

Illinois-Indiana Sea Grant (IISG). Sea Grant Database of Aquatic Species Regulations (2011). 

http://www.iiseagrant.org/il-ans/index2.html

Indiana Department of Natural Resources (INDNR). Hydrilla. Aquatic Invasive Species (2009). 

http://www.in.gov/dnr/files/hydrilla.pdf.

Indiana Department of Natural Resources (INDNR), Fish and Wildlife Division. Fish Hauler’s and 

Supplier’s Permit Holders Public List (2013). http://www.in.gov/dnr/fishwild/files/fwCommercial_Fish_Suppliers.pdf

Innal, D. and F. Erk’akan. Effects of exotic and translocaated fish species in the inland waters of Turkey. 

Rev. Fish. Biol. Fisheries 16: 39-50 (2006).

Invasive Plant Atlas of the MidSouth (IPAMS). Eichhornia crassipes (Mart.) Solms, Common Water 

Hyacinth (2013). https://www.gri.msstate.edu/ipams/species.php?CName=Common%20Waterhyacinth

Invasive Species Program. Invasive species of aquatic plants and wild animals in Minneosta: Annual 

Report for 2011. Minnesota Department of Natural Resources, St. Paul, MN. 118 pp. (2011).

Irons, K.S., G.G. Sass, M.A. McClelland, and J.D. Stafford. Reduced condition factor of two native fish 

species coincident with invasion of non-native Asian carps in the Illinois River, U.S.A. Is this evidence 

for competition and reduced fitness? Journal of Fish Biology 71: 258-273 (2007).

Ivancheva, E.Y., and V.P. Ivanchev. Dynamics of species composition of fish and some results of 

ichthyomonitoring in the middle course of the Oka (Ryazan oblast). Journal of Ichthyology 48(8): 596-

604 (2008).
1562

Ivanov, B., L. Zhang, and Z. Wang. Invasive alien species. Basic Studies in Natural Sciences, Roskild 

Universitetscenter Nib 14.2 (2007).

Izci, Y., S. Pusat, and O. Onguru. Fatty filum with different histological features. Case report. 

Neurocirugia 22 (5): 457-460 (2011).

Jacoby, J.M., E.B. Welch, and I. Wertz. Alternate stable states in a shallow lake dominated by Egeria 

densa. Verhandlungen des Internationalen Verein Limnologie 27: 3805-3810 (2001).

Jafari, N. Ecological and socio-economic utilization of water hyacinth (Eichhornia crassipes Mart 

Solms). Journal of Applied Sciences and Environmental Management 14 (2): 43-49 (2010).

Jakob, N.J., R. Kehm, and H.R. Gelderblom. A novel fish herpesvirus of Osmerus eperlanus. Virus Genes

41:81-85 (2010).

Jamet, J.L., and F. Desmolles. Growth, reproduction, and condition of Roach (Rutilus rutilus (L.)), Perch 

(Perca fluviatilis, L.) and Ruffe (Gymnocephalus cernuus (L.)) in eutrophic Lake Aydat (France). 

International Revue der gesmten Hydrobiologie 70 (2): 305-322 (1994).

Jamieson., C.D., and B. Santer. Materna aging in the univoltine freshwater copepod Cyclops kolensis: 

variation in egg sizes, egg development times, and naupliar development times. Hydrobiologia 510: 75-

81 (2003).

Janbaz, A.A., H. Fazli, R. Pourgholam, M.A. Afraei Bandpyi, H. Nasr Elahzadeh, and S. H. Almaleki. 

Reproduction, sexual maturity, and fecundity of Anchovy Kilka (Clupeonella engrauliformis Svetovidov, 

(1941) in Iranian waters of the Caspian Sea. Iranian Scientific Fisheries Journal 20 (4): 21-32 (2012).

Jankauskiene, R. Selective feeding of Ponto-Caspian higher crustaceans and fish larvae in the littoral zone 

of the Curonian Lagoon. Ekologija 2: 19-27 (2003).

Janssen, J., and D.J. Jude. Recruitment failure of Mottled Sculpin Cottus bairdi in the Calumet Harbor, 

southern Lake Michigan, induced by the newly introduced Round Goby Neogobius melanostomus. 

Journal of Great Lakes Research 27 (3): 319-328 (2001).

Jaroszewska, M., K. Dabrowski, B. Wilczynska, and T. Kakareko. Structure of the gut of the Racer Goby 

Neogobius gymnotrachelus (Kessler, 1857). Journal of Fish Biology 72(7): 1773-1786 (2008).

Jażdżewski, K. Range extensions of some Gammaridean species in European inland waters caused by 

human activity. Proceedings of the 4th International Colloquium on Gammarus and Niphargus, 

Blacksburg, Virginia, USA, 10-16 September 1978: Studies on Gammaridea II. Crustaceana: Supplement 

6: 84-107 (1980).

Jażdżewski, K. An invasive Ponto-Caspian amphipod Dikerogammarus haemobaphes (Eichwald, 1841) 

conquers Great Masurian Lakes, north-eastern Poland. Fragmenta Faunistica 46 (1): 19-25 (2003).

Jażdżewski, K., and A. Konopacka. Immigration history and present distribution of alien crustaceans in 

Polish waters. The Biodiversity Crisis and Crustacea 55-64 pp. (2000).
1563

Jażdżewski, K., and A. Konopacka. Invasive Ponto-Caspian species in waters of the Vistula and Oder 

basins and the southern Baltic Sea. Leppäkoski E., S. Gollasch, and S. Olenin (eds.). Invasive aquatic 

species of Europe. Kluwer, Dordrecht 384-394 pp. (2002). 

Jażdżewski, K., A. Konopacka, and M. Grabowski. Four Ponto-Caspian and one American gammarid 

species (Crustacea, Amphipoda) recently invading Polish waters. Contributions to Zoology 71 (4): 115-

122 (2002).

Jażdżewski, K., A. Konopacka, and M. Grabowski. Recent drastic changes in the gammarid fauna 

(Crustacea, Amphipoda) of the Vistula River deltaic system in Poland caused by alien invaders. Diversity 

and Distributions 10 (2): 81-87 (2004).

Jażdżewski, K., A. Konopacka, and M. Grabowski. Native and alien malacostracan Crustacea along the 

Polish Baltic Sea coast in the twentieth century. Oceanological and Hydrobiological Studies 34 (1): 175-

193 (2005).

Jenkins, R.E., and N.M. Burkhead. Freshwater fishes of Virginia. American Fisheries Society, Bethesda, 

MD (1994).

Jennings, D.P. Bighead Carp (Hypophthalmichthys nobilis): a biological synopsis. United States Fish and 

Wildlife Service Biological Report 88(2): 1-35 (1988).

Jensen, K.R. NOBANIS – Invasive Alien Species Fact Sheet, Rhithropanopeus harrisii. Identification 

key to marine invasive species in Nordic waters (2010). www.nobanis.org

Jeppesen, E., J.P. Jensen, M. Sondergaard, T.L. Lauridsen, and F. Landkildehus. Trophic structure, 

species richness and biodiversity in Danish lake: changes along a phosphorus gradient. Freshwater 

Biology 45: 201-218 (2000).

Jeppesen, E., J.P. Jensen, H. Skovgaard, and C.B. Hvidt. Changes in the abundance of planktivorous fish 

in Lake Skanderborg during the past two centuries- a palaeoecological approach. Palaeography, 

Palaeoclimatology, Palaeoecology 172: 143-152 (2001).

Jerde, C.L., M.L. Bundy, M.A. Barnes, A.R. Mahon, M.P. Galaska, J.M. Deines, W.L. Chadderton, and 

D.M. Lodge. Environmental DNA surveillance of the Chicago area bait trade for juvenile Bighead and 

Silver Carp contamination. Final report to the Illinois Department of Natural Resources. Great Lakes 

Protection Fund. 36 pp. (2012).

Jester, D.B., A.A. Echelle, W.J. Matthews, J. Pigg, C.M. Scott, and K.D. Collins. The Fishes of 

Oklahoma, their gross habitats, and their tolerance of degradation in water quality and habitat. 

Proceedings of the Oklahoma Academy of Science 72: 7-19 (1992).

Jezewski, W., and A. Kamara. First reported occurrence of Thelohanellus oculileucisci (Trojan, 1909) 

(Myxosporidia) and Leuciscus leuciscus (L.) and L-idus (L.) in Poland. Acta parasitologica 44:145-146 

(1999).

Jianqing, D., W. Ren, F. Weidong, and Z. Guoliang. Water Hyacinth in China: its distribution, problems 

and control status. Julien, M.H., M.P. Hill, T.D. Center, and D. Jianqing (eds.). Biological and integrated 

control of Water Hyacinth, Eichhornia crassipes. Australian Centetre for International Agriculture 

Research (ACIAR) Proceedings 102 29-32 pp. (2001).
1564

Johengen, T.H., T.F. Nalepa, G.L. Fahnenstiel, and G. Goudy. Nutrient changes in Saginaw Bay, Lake 

Huron, after establishment of the Zebra Mussel (Dreissena polymorpha). Journal of Great Lakes 

Research 21(4): M9-64 (1995).

Johengen, T., T.F. Nalepa, G.A. Lang, D.L. Fanslow, H.A. Vanderploeg, and M.A. Agy. Physical and 

chemical variables of Saginaw Bay, Lake Huron in 1994-1996. Technical Memorandum 115, GLERL, 

Ann Arbor, MI. 39 pp. (2000).

Johengen, T., D. Reid, G. Fahnenstiel, H. MacIsaac, F. Dobbs, M. Doblin, G. Ruiz, and P. Jenkings, P.T. 

Jenkins, and Associated Ltd. Assessment of transoceanic NOBOB Vessels and low-salinity ballast water 

as vectors for non-indigenous species introductions to the Great Lakes. Cooperative Institute for 

Limnology and Ecosystems Research (CILER) and NOAA Great Lakes Environmental Research 

Laboratory, Ann Arbor, MI (2005). 

Johnson, F.A., and F. Montalbano III. Selection of plant communities by wintering waterfowl on Lake 

Okeechobee. Florida Journal of Wildlife Management 48: 174-178 (1984).

Johnston, C. E. The relationship of spawning mode to conservation of North American minnows 

(Cyprinidae). Environmental Biology of Fishes 55:21-30 (1999).

Jones, J.R.E. The reactions of fish to water of low oxygen concentration. The Journal of Experimental 

Biology 29: 403-415 (1952).

Jones, W. Invasive plants close ramps on two Indiana Lakes. Water Column 18 (3): 1-4 (2006).

Joyce, J.C. K.A. Langeland, T.K. Van, and V.V. Vandiver, Jr. Organic sedimentation associated with 

hydrilla management. Journal of Aquatic Plant Management 30: 20-23 (1992).

Joyce, J. Controlling the ballastwater: limiting the invasion. Power point presentation (2005).

Jude, D.J. Round gobies: Cyberfish of the third millennium. Great Lakes Research Review 3(1): 27-34 

(1997).

Jude, D.J. Round and Tubenose Gobies: 10 years with the latest Great Lakes phantom menace. 

Dreissena! 11: 1-14 (2001).

Jude, D.J., J. Janssen, and G. Crawford. Ecology, distribution, and impact of the newly introduced Round 

and Tubenose Gobies on the biota of the St. Clair and Detroit Rivers. Munaware, M., T. Edsall, and J. 

Leach (eds.). The Lake Huron Ecosystem: Ecology, Fisheries and Management. Ecovision World 

Monograph Series, S.P.B. Academic Publishing, The Netherlands 447-460 pp. (1995).

June-Wells, M., C.R. Vassbrinck, J. Gibbons, and G. Bugbee. The aquarium trade: a potential risk for 

nonnative plant introductions in Connecticut, USA. Lake and Reservoir Management 28 (3): 200-205 

(2012).

Jurajda, P., J. Čerńy, M. Polačik, Z. Valová, M. Janáč, R. Blažek, and M. Ondračková. The recent 

distribution and abundance of non-native Neogobius fishes in the Slovak section of the River Danube. 

Journal of Applied Ichthyology 21: 319-323 (2005).

Jurajada, P., M. Vassilev, M. Polačik, and T. Trichkova. A first record of Perccottus glenii (Perciformes: 

Odontobutidae) in the Danube River in Bulgaria. Acta Zoologica Bulgarica 58 (2): 279-282 (2006)
1565

Jurvelius, J., H. Auvinen, I. Kolari, and T.J. Marjomäki. Density and biomass of Smelt (Osmerus 

eperlanus) in five Finnish lakes. Fisheries Research 73:353-361 (2005).

Kabata, Z. Parasitic Copepod of British Fishes. The Ray Society, London (1979).

Kaeriyama, M., M. Nakamura, R. Edpalina, J.R. Bower, H. Yamaguchi, R.V. Walker, and K.W. Myers. 

Change in feeding ecology and trophic dynamics of Pacific Salmon (Oncorhynchus spp.) in the central 

Gulf of Alaska in relation to climate events. Fisheries Oceanography 13(3): 197-207 (2004).

Kakalova, E., and L. Shonia. The results of ecological-parasitological study of Pseudorasbora parva

populated in kumisi reservoir and Basaleti lake. Proceedings of the Institute of Zoology 23: 41-42 (2008).

Kakareko, T., J. Zbikowski, and M. Kowalska. Wstepne wyniki badan ́ nad relacjami troficznymi 

pomiedzy inwazyjnymi rybami babkowatymi z rodzaju Neogobius a malymi okoniowatymi w 

przybrze_znej strefie Zbiornika Wloclawskiego [Trophic relationships between the invasive gobiid of 

genus Neogobius, and small percids in the littoral zone of the Wloclawski Reservoir]. Acta Hydrobiol. 

(Suppl.) 6: 29–38 [in Polish] (2003). 

Kakareko, T., D. Pllachocki, and J. Kobak. Relative abundance of Ponto-Caspian gobiids in the 

lower Vistula River (Poland) 3 to 4 years after first appearance. Journal of Applied Ichthyology

25 (6): 647-51 (2009).

Kakareko, T., J. Zbikowski, and J. Zytkowicz. Diet partitioning in summer of two syntopic neogoobiids 

from two different habitats of the lower Vistula River, Poland. J. Appl. Ichthyol. 21: 292-295 (2005).

Kakareko, T., J. Kobak, J. Grabowska, L. Jermacz, M. Przybylski, M. Poznanska, D. Pietraszewski, and 

G. H. Copp. Competitive interactions for food resources between invasive racer goby Babka 

gymnotrachelus and native European bullhead Cottus gobio. Bioogical. Invasions 15(11): 2519-2530 

(2013).

Kalchhauser, I., P. Mutzner, P.E. Hirsch, and P. Burkhardt-Holm, P. Arrival of round goby Neogobius 

melanostomus (Pallus, 1814) and bighead goby Ponticola kessleri (Günther, 1861) in the High Rhine 

(Switzerland). BioInvasions Records 2(1): 79-83 (2013).

Kalogirou, S., F. Mittermayer, L. Pihl, and H. Wennhage. Feeding ecology of indigenous and nonindigenous fish species within the family Sphyaenidae. Journal of Fish Biology 80: 2528-2548 (2012).

Kangur, P., A. Kangur, and K. Kangur. Dietary importance of various prey fishes for Pikeperch Sander 

lucioperca (L.) in large shallow lake Võrtsjärv (Estonia). Proceedings of the Estonian Academy of 

Sciences: Biology, Ecology 154-167 pp. (2007a).

Kangur, A., P. Kangur, K. Kangur, and T. Möls. The role of temperature in the population dynamics of 

Smelt Osmerus eperlanus m. spirinchus Pallas in Lake Peipsi (Estonia/Russia). Gulati, R., E. Lammens, 

N. Pauw, and E. Donk (eds.). Shallow Lakes in a Changing World. Springer Netherlands 433-441 pp. 

(2007b).

Kapusta, A., E. Bogacka-Kapusta, and B. Czarnecki. The Significance of Stone Moroko, Pseudorasbora 

Parva (Temminck and Schlegel), in the Small-Sized Fish Assemblages in the Littoral Zone of the Heated 

Lake Licheńskie. Archives of Polish Fisheries 16: 49 (2008).
1566

Kar, R.K., and M.A. Choudhuri. Effect of desiccation on internal change with respect of survival of 

Hydrilla verticillata. Hydrobiological Bulletin 16 (2):213-221 (1982).

Karås, P., and A. Sandström. Effects of eutrophication on Y-O-Y freshwater fish communities in coastal 

areas of the Baltic. Environmental Biology Fisheries 63: 89-101 (2002).

Karatayev, A.Y., L.E. Burlakova, and D.K. Padilla. The effects of Dreissena polymorpha (Pallas) 

invasion on aquatic communities in eastern Europe. Journal of Shellfish Research 16: 187-203 (1997).

Karatayev, A.Y., L.E. Burlakova, and D.K. Padilla. Impacts of Zebra Mussels on aquatic communities 

and their role as ecosystem engineers. Leppäkoski, E., S. Gollasch, and S. Olenin (eds.). Invasive aquatic 

species of Europe: Distribution, impacts and management. Kluwer Academic Publishers. Dodrecht, The 

Netherlands 433-446 pp. (2002).

Karatayev, A.Y., D. Boltovskoy, D.K. Padilla, and L.E. Burlakova. The invasive bivalves Dreissena 

polymopha and Limnoperna fortunei: parallels, contrasts, potential spread and invasion impacts. Journal 

of Shellfish Research 26 (1): 205-213 (2007).

Karatayev, A.Y., L.E. Burlakova, V.A. Karatayev, and D. Boltovskoy. Limnoperna fortunei versus 

Dreissena polymorpha: Population Densities and Benthic Community Impacts of Two Invasive 

Freshwater Bivalves. Journal of Shellfish Research 29 (4): 975-984 (2010).

Karimzadeh, G. Study of natural and fishing mortality and exploitation rate of Common Kilka 

Clupeonella cultriventris in southeast part of the Caspian Sea (Babolsar). Annual Review and Research in 

Biology 1 (3): 57-67 (2011).

Karimzadeh, G., B. Gabrielyan, H. and Fazli. Population dynamics and biological characteristics of kilka 

species (Pisces: Clupeidae) in the southeastern coast of the Caspian Sea. Iranian Journal of Fisheries 

Sciences 9 (3): 422-433 (2010).

Karl, H. Composition and nematodes in Smelt (Osmerus eperlanus L.). Inf Fischereiforsch 53: 65-70 

(2006).

Karlson, A.M.L., G. Almqvist, K.E. Skora, and M. Appelberg. Indications of competition between non 

indigenous Round Goby and native Flounder in the Baltic Sea. ICES Journal of Marine Science 64: 479-

486 (2007).

Karpevich, A.F. Bioecological characteristics of mollusc Monodacna colorata (Eichwald) in 

Taganrogsky Gulf. Trudy VNIRO 43: 244-256 (1960).

Karpevich, A. Teorija i praktika akklimatizacii vodnykh vodoemov. Pishchevaya Promyshlennost, 

Moskva (1975).

Karttunen, V. Professional fishing at the sea. Finish Fisheries in the European Perspective. Statistics and 

other data on fisheries in European Union member countries and in Finland, Sweden and Norway. Finnish 

Game and Fisheries Research Institute. Official Statistics of Finland. Environment 10: 13-32 (1994).

Kas’yanov, A.N. Study of some meristic features in the Black Sea Caspian Kilka (Clueponella 

cultriventris, Clupeidae) introduced in Volga River Reservoirs. Journal of Ichthyology 49 (8): 642-649

(2009).
1567

Kasselmann, C. Aquarienpflanzen. Egen Ulmer GMBH & Co., Stuttgart (1995).

Kautman, J. The first occurrence of Neogobius gymnotrachelus in the Slovak Danube. Folia Zoologica 

50: 79-80 (2001).

Keckeis, H. and F. Schiemer. Consumption, growth, and respiration of bleak, Alburnus alburnus (L.), and 

roach Rutilus rutilus (L.), during ontogeny. Journal of Fish Biology 36 (6): 841-851 (1990).

Kelleher, B., G. van der Velde, P. Giller, and A. bij de Vaate. Dominant role of exotic mass invaders in 

the diet of important fish species of the River Lower Rhine, The Netherlands. pp 20-24. (1998)

Kelleher, B., G. Van Der Velde, K. Wittmann, M. Faasse, and A. Bij De Vaate. Current status of the 

freshwater Mysidae in the Netherlands, with records of Limnomysis benedeni Czerniavsky, 1882, a 

Pontocaspian species in Dutch Rhine branches. Bulletin Zoölogisch Museum, Universiteit van 

Amsterdam 16 (13) (1999).

Kelleher, B., G. van der Velde, P. Giller, and A. bij de Vaate. Dominant role of exotic mass invaders in 

the diet of important fish species of the River Lower Rhine, The Netherlands. 4th International 

Crustacean Congress, Amsterdam. Crustacean Issues 12: 35-46 (2000).

Kennedy, M. Spawning and early development of the Dace Leuciscus leuciscus (L.). Journal of Fish 

Biology 1(3): 249-259 (1969).

Kennedy, M., and D. McCarthy. The biology of Irish course fish. Inland Fisheries Trust, Internal Report

(1965). 

Keresztessy, K. Threatened freshwater fish of Hungary. In Conservation of Endangered Freshwater Fish. 

Europe. A. Kirchhofer and D. Hefti (eds.). Birkhäuser Verlag, Basel, Switzerland 73-78 pp. (1996).

Kershner, M.W., D.M. Schael, R.L. Knight, R.A. Stein, and E.A. Marschall. Modeling sources of 

variation for growth and predatory demand of Lake Erie Walleye (Stizostedion vitreum), 1986-1995. 

Canadian Journal of Aquatic Sciences 56: 527-538 (1998).

Keskin, Ҫ. Distribution of demersal fish species in the Black Sea, Sea of Marmara and North Aegean Sea. 

Rapports Commission International Mer Mediterranee 39: 558-560 (2010).

Keskinen, T., and T.J. Marjomäki. Diet and prey size spectrum of Pikeperch in lakes in central Finland. 

Journal of Fish Biology 65: 1147-1153 (2004).

Ketelaars, H.A., F.E. Lambregts-van de Clundert, C.J. Carpentier, A.J. Wagenvoort, and W. 

Hoogenboezem. Ecological effects of the mass occurrence of the Ponto-Caspian invader, Hemimysis 

annomala G.O. Sars, 1907 (Crustaceae: Mysidacea), in a freshwater storage reservoir in the Netherlands, 

with notes on its autecology and new records. Hydrobiologia 394: 233-248 (1999).

Ketelaars, H.A.M. Chapter 13: Range extension of Ponto-Caspian aquatic invertebrates in continental 

Europe. Dumont, H.J. (ed.). Aquatic Invasions in the Black, Caspian, and Mediterranean Seas: The 

Ctenophores Mnemiopsis leidyi and Beroe in the Pont-Caspian and other aquatic invasions. Klower 

Academic Publishers. 209-236 pp. (2004).
1568

Kevrekidis, T., A.K. Kokkinakis, and A. Koukouras. Some aspects of the biology and ecology of 

Knipowitschia caucasica (Teleostei: Gobiidae) in the Evros Delta (North Aegean Sea). Helgoländer 

Meeresuntersuchungen 44 (2): 173-187 (1990).

Khalko, V.V. On the physiological-biochemical state of Kilka Clupeonella cultriventris (Clupeidae, 

Clupeiformes) in the Rybinsk Reservoir (Russia). Journal of Ichthyology 47(4): 320-330 (2007).

Kiener, A. and C. J. Spillman. Contributions a l’etude systematique et ecologique d’Atherina boyeri Risso 

(Poissons, Cyprinidae) dan sa zone de dispersion actuelle. Bulletin du Museum National d’Histoire 

Naturelle, 3rd Series, No. 55. Zoology 41: 563-580. (1969)

Kikuchi, S., and M. Matsumasa. Two ultrastructurally distinct types of transporting tissues, the 

branchiostegal and the gill epithelia, in an estuarine tanaid, Sinelobux stanfordi (Crustacea, Peracarida). 

Zoomorphology 113: 253- 260 (1993).

Kim, B.H., M.S. Han, and N. Takamura. Effects of fish introduction on the length of the tail of 

cryptomonads in mesocosms experiments. Oecologia 136:73-79 (2003).

King, J.L., F. Marnell, N. Kingston, R. Rosell, P. Boylan, J.M. Caffrey, U. FitzPatrick, P.G. Gargan, F.L. 

Kelly, M.F. O’Grady, R. Poole, W.K. Roche, and D. Cassidy. Ireland Red List No. 5: Amphibians, 

Reptiles, and Freshwater Fish. National Parks and Wildlife Service, Department of Arts, Heritage, and the 

Gaeltacht, Dublin, Ireland (2011). 

Kinzelbach, R. Aquatische Neozoen in Europa. Newsletter der Arbeitsgruppe Neozoen, Allgemeine und 

Spezielle Zoologie, Universität Rostock. Neozoen (Rostock) 1: 7-8 (1997).

Kinzler, W., A. Kley, G. Mayer, D. Waloszek, and G. Maier. Mutual predation between and cannibalism 

within several freshwater gammarids: Dikerogammarus villosus versus one native and three invasives. 

Aquatic Ecology 43 (2): 457-464 (2009).

Kipp, R.M. Gammarus fasciatus. USGS Nonindigenous Aquatic Species Databse, Gainesville, FL 

(2014).

Kipp, R., S.A. Bailey, H.J. MacIsaac, and A. Ricciardi. Transoceanic ships as vectors for nonindigenous 

freshwater bryozoans. Diversity and Distributions 16: 77-83 (2010).

Kipp, R., B. Cudmore, and N.E. Mandrak. Updated (2006-early 2011) biological synopsis of Bighead 

Carp (Hypophthalmichthys nobilis) and Silver Carp (H. molitrix). Canadian Manuscript Reports of 

Fisheries and Aquatic Science 2962: vi+ 50 p. (2011).

Kipp, R., I. Hébert, M. Lacharité, and A. Ricciardi. Impacts of predation by the Eurasian Round Goby 

(Neogobius melanostomus) on mollusks’ in the upper St. Lawrence River. Journal of Great Lakes 

Research 38:78-89 (2012).

Kipp, R.M., A.K. Bogdanoff, and A. Fusaro. Timoniella sp. USGS Nonindigenous Aquatic Species 

Database, Gainesville, FL (2014).

Kirby, J.R. Notes on Crassula helmsii. The Cactus and Succulent Journal of Great Britian 26: 9-10 

(1965). 
1569

Kiticyna, L.A. Ekologo-fiziologicheskie osobennosti bokoplava Dikerogammarus haemobaphes (Eich.) v 

ra€ione srosa podogretykh vod Tripolsko€i GRES. Gidrobiologicheskiı ̈ Zhurnal 16: 77-85 (1980).

Kiyashko, V.I., V.V. Osipov, and Y.V. Slyn’ko. Size-age characteristics and population structure of 

Clupeonella cultriventris at its naturalization in the Rybinsk Reservoir. Journal of Ichthyology 46 (1): 64-

73 (2006).

Kiyashko, V.I., N.A. Khalko, and V.I. Lazareva. On the diurnal rhythm and feeding electivity in Kilka 

(Clupeonella cultriventris) in Rybinsk River. Journal of Ichthyology 47 (4): 310-319 (2007). 

Kiyashko, V.I., D.P. Karabanov, V.N. Yakovlev, and V. Slyn’ko. Formation and development of the 

Black Sea-Caspian Kilka Clupeonella cultriventris (Clupeidae) in the Rybinsk Reservoir. Journal of 

Ichthyology 52 (8): 537-546 (2012).

Klavsen, S.K., and S.C. Maberly. Crassulacean acid metabolism contributes significantly to the in situ 

carbon budget in a population of the invasive aquatic macrophyte Crassula helmsii. Freshwater Biology

54 (1): 105-118 (2009).

Klein, G., K. MacIntosh, I. Kaczmarska, and J.M. Ehrman. Diatom survivorship in ballast water during 

trans-Pacific crossings. Biological Invasions 12: 1031-1044 (2010).

Kley, A., and G. Maier. Life history characteristics of the invasive freshwater gammarids 

Dikerogammarus villosus and Echinogammarus ischnus in the river Main and the Main-Donau canal.

Archiv für Hydrobiologie 156: 457-469 (2003).

Kley, A., and G. Maier. Reproductive characteristics of invasive gammarids in the Rhine-Main-Danube 

catchment, South Germany. Limnologica 36: 79-90 (2006).

Kling, G.W., B. Fry, and W.J. O’Brien. Stable isotopes and planktonic trophic structure in arctic lakes. 

Ecology 73 (2): 561-566 (1992).

Klussman, W.G., R.L. Noble, R.D. Martyn, W.J. Clark, R.K. Betsill, P.W. Bettoli, M.F. Cichra, and J.M.

Campbell. Control of aquatic macrophytes by Grass Carp in Lake Conroe, Texas, and the effect on the 

reservoir ecosystem. Texas Agriculture Experiment Station MP-1664. College Station, Texas (1988).

Knauer, K., S. Mohr, and U. Feiler. Comparing growth development of Myriophyllum spp. in laboratory 

and field experiments for ecotoxicological testing. Environmental Science and Pollution Research 15: 

322-331 (2008).

Knight, D.L. The Finish Connection: A Great Lakes maritime research tour to the Baltic Sea finds many 

shared interests. Great Lakes Maritime Research Institute (GLMRI) (2008). 

http://www.glmri.org/downloads/finnish_GL_Seaway_Review.pdf

Knouft, J.H., and L.M. Page. Assessment of the relationships of geographic variation in species richness 

to climate and landscape variables within and among lineages of North American freshwater fishes. 

Journal of Biogeography 38: 2259–2269 (2011).

Kobak, J., T. Kakareko, M. Poznańska, and J. Żbikowski. Preferences of the Ponto-Caspian amphipod 

Dikerogammarus haemobaphes for living zebra mussels. Journal of Zoology 279 (3): 229-235 (2009).
1570

Kocovsky, P.M., D.C. Chapman, and J.E. McKenna. Thermal and hydrologic suitability of Lake Erie and 

its major tributaries for spawning of Asian carps. Journal of Great Lakes Research 38(1):159-166 (2012).

Koed, A., N. Jepsen, K. Aarestrup, and C. Nielsen. Initial mortality of radio-tagged Atlantic Salmon 

(Salmo salar L.) smolts following release downstream of a hydropower station. Hydrobiologia 483: 31-37 

(2002).

Kohlmann, K. R. Gross, A. Murakaeva, and P. Kersten. Genetic variability and structure of Common 

Carp (Cyprinus carpio) populations throughout the distribution range inferred from allozyme, 

microsatellite and mitochondrial DNA markers. Aquatic Living Resources 16: 421-431 (2003).

Kolar, C.S., and D.M. Lodge. 2002. Ecological predictions and risk assessment for alien fishes in North 

America. Science 298: 1233-1236 (2002).

Kolar, C.S., D.C. Chapman, W.R. Courtenay Jr., C.M. Housel, and J.D. Williams. Asian carps of the 

genus Hypophthalmichthys (Pisces, Cyprinidae)? A Biological Synopsis and Environmental Risk 

Assessment. United States Fish and Wildlife Service (2005).

Kolar, C.S., D.C. Chapman, W.R. Courtenay, C.M. Housel, J.D. Williams, and D.P. Jennings. Bigheaded 

Carps: a biological synopsis and environmental risk assessment. American Fisheries Society, Special 

Publication 33, Bethesda, Maryland (2007).

Komarova, T.I. Mizidy (Mysidacea). Fauna Ukrainy 26 (7) (1991).

Konishi, M., and K. Takata. Impact of asymmetrical hybridization followed by steril F1 hybrids on 

species replacement in Pseudorasbora. Conservation Genetics 5: 463-474 (2004).

Konishi, M., K. Hosoya, and K. Takata. Natural hybridization between endangered and introduced 

species of Pseudorasbora, with their genetic relationships and characteristics inferred from allozyme 

analyses. Journal of Fish Biology 63: 213-231 (2003).

Konopacka, A. Nowy dla Polski gatunek kielza, Dikerogammarus haemobaphes (Eichwald, 1841) 

(Crustacea, Amphipoda) oraz dwa inne rzadkie gatunki skorupiaków obunogich w Wisle. Przeglad 

Zoologiczny 42: 211-218 (1998).

Kontula, T. and Väinölä, R. Postglacial colonization of Northern Europe by distinct phylogeographic 

lineages of the Bullhead, Cottus gobio. Molecular Ecology 10: 1983-2002 (2001). 

Kopp, D., J. Cucherousset, J. Syvaranta, A. Martino, R. Cereghino, and F. Santoul. Trophic ecology of 

the Pikeperch (Sander lucioperca) in its introduced areas: a stable isotope approach in southwestern 

France. Compte Rendus Biologies 332: 741-746 (2009).

Kornis, M.S., and M.L. Vander Zanden. Forecasting the distribution of the invasive Round Goby 

(Neogobius melanostomus) in Wisconsin tributaries to Lake Michigan. Canadian Journal of Fisheries 

and Aquatic Sciences 67: 553-562 (2010).

Kornis, M.S., N. Mercado-Silva, and M.J. Vander Zanden. Twenty years of invasion: a review of round 

goby Neogobius melanostomus biology, spread, and ecological implications. Journal of Fish Biology 80: 

235-285 (2012).
1571

Kornis, M.S., S. Sharma, and M.J. Vander Zanden. Invasion success and impact of an invasive fish, 

Round Goby, in Great Lakes tributaries. Diversity and Distributions 19(2): 184-198 (2013). 

Koščo, J., S. Lusk, K. Halačka, and V. Lusková. The expansion and occurrence of the Amur sleeper 

(Perccottus glenii) in eastern Slovakia. Folia Zoologica 52 (3): 329-336 (2003).

Koščo, J., P. Manko, D. Miklisová, and L. Košuthová. Feeding ecology of invasive Perccottus glenii

(Perciformes, Odontobutidae) in Slovakia. Czech Journal of Animal Science 53 (11): 479-486 (2008).

Košco, J., L. Košuthová, P. Košuth, and L. Pekárik. Non-native fish species in Slovak waters: origins and 

present status. Biologia 65(6): 1057-1063 (2010).

Kosova, A.A. Bivalve Monodacna colorata Eichw. in the lower Volga. Proceedings of the All-Union 

Hydrobiological Society 13: 84-89 (1963).

Kostrzewa J., and M. Grabowski. Monkey goby, Neogobius fluviatilis (Pallas, 1811), in the Vistula River 

– a phenomenon of Ponto-Caspian Gobiidae invasion. Przegl Zoologica (in Polish with English 

summary) 46: 235-242 (2002). 

Kostrzewa, J., and M. Grabowski. Opportunistic feeding strategy as a factor promoting the expansion of 

Racer Goby (Neogobius gymnotrachelus Kessler, 1857) in the Vistula basin. Lauterbornia 48: 91-100 

(2003).

Kotta, J., and T. Möller. Important scales of distribution patterns of benthic species in the Gretagrund 

area, the central Gulf of Riga. Estonian Journal of Ecology 58: 259-269 (2009).

Kottelat, M. European freshwater fishes: An heuristic checklist of the freshwater fishes of Europe 

(exclusive of former USSR), with an introduction for non-systematists and comments on nomenclature 

and conservation (Vol. 5). Slovak Academy of Sciences (1997).

Kottelat, M. Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: 

Cobitoidei). The Raffles Bulletin of Zoology 26: 1-199 (2012).

Kottelat, M., and J. Freyhof. Handbook of European Freshwater Fishes. Publications Kottelat 646 pp. 

(2007).

Kotusz, J., and A. Witkowski. Morphometrics of Pseudorasbora parva (Schlegel, 1842) (Cyprinidae: 

Gobioninae), a species introduced into the Polish waters. Acta Ichthyology Piscatoria 28: 3-14 (1998).

Kováč, V., G.H. Copp, and R.P. Sousa. Life-history traits of invasive Bighead Goby Neogobius kessleri

(Gunther, 1861) from the middle Danube River, with a reflection on which goby species may win the 

competition. Journal of Applied Ichthyology 25: 33-37 (2009).

Kovačić, M., and A. Pallaoro. Is Knipowitschia caucasica- like form from the Adriatic Sea a new goby 

species? Evidence from a morphological approach in the Eastern Adriatic Sea. Cybium 27 (2): 131-136

(2003).

Kozminski, Z. Morphometrische und ökologische Untersuchungen an Cyclopiden der strenuus-Gruppe. 

Intenationale Revue er gesamten Hydrobiologie 33: 161-240 (1936).
1572

Krasnoyd, V., Y. Kvach, and O. Drobiniak. The parasite fauna of the gobiid fish (Actinopterygii, 

Gobiidae), in the Sukhyi Lyman, Black Sea. Vestnki Zoologii 46 (6): e1-e8 (2012).

Krieg, F., A. Triantafyllidis, and R. Guyomard. Mitochondrial DNA variation in European populations of 

Silurus glanis. Journal of Fish Biology 56: 713-724 (2000).

Kruglova, V.M. The prospects for the acclimatization of some species of the Caspian fauna. Trudy 

Vsesoyuznogo Gidrobiologicheskogo Obschestvava 11: 345-353 (1961).

Krylov, P.I., D.E. Bychenkov, V.E. Panov, N.V. Rodionova, and T.V. Telesh. Distribution and seasonal 

dynamics of the Ponto-Caspian invader Cercopagis pengoi (Crustacea, Cladocera) in the Neva Estuary 

(Gulf of Finland). Hydrobiologia 393: 227-232 (1999). 

Kucklentz, V. Restoration of a small lake by combined mechanical and biological methods. 

Verhandlungen Internationale Vereinigung für Theoretische und Angewandte Limnologie 22: 2314-2317 

(1985).

Küçük, F., I. Gülle, S.S. Güçlü, E. Gümüs, and O. Demir. Egirdir Gölü’ne sonradan giren gümüsbaligi 

(Atherina boyeri Risso, 1810)’nin göl ekosistemine ve balikçiliga etkisi. I. Ulusal Baliklandirma ve 

Rezervuar Yönetimi Sempozyumu Bildirileri, 7-9 Subat 2006 Antalya: 119-128 (2007).

Küçük, F., S.S. Güçlü, İ. Gülle, Z. Güçlü, N.L. Çiçek, G. Diken. Reproductive features of Big Scale-Sand 

Smelt, Atherina boyeri (Risso, 1810), and exotic fish in Lake Eğirdir (Isparta, Turkey). Turkish Journal of 

Fisheries and Aquatic Sciences 12: 729-733 (2012).

Kuhn, T., T. Benninghoff, H. Karl, T. Landry, and S. Klimpel. Sealworm Pseudoterranova decipiens s.s. 

infection of European Smelt Osmerus eperlanus in German coastal waters: ecological implications. 

Diseases of Aquatic Organisms 102: 217-224 (2013).

Kujawa, S. Biology and cultivation of the crab R. harrisii tridentatus from the Vistula Lagoon. 

Wszechswiat 2: 57-59 (1957).

Kulhanek, S. A., A. Ricciardi, and B. Leung. Is invasion history a useful tool for predicting the impacts of 

the world’s worst aquatic invasive species? Ecological Applications 21: 189-202 (2011).

Kuliskova, P., P. Horky, O. Slavik, and J.I. Jones. Factors influencing movement behavior and home 

range size in Ide Leuciscus idus. Journal of Fish Biology 74: 1269-1279 (2009).

Kulp, R.E., V. Politano, H.A. Lane, S.A. Lombardi, and K.T. Paynter. Predation of juvenile Crassostrea 

virginica by two species of mud crabs found in the Chesapeake Bay. Journal of Shellfish Research 30: 

261-266 (2011).

Kupren, K., D. Zarski, S. Krejszeff, D. Kucharczyk, and K. Targonska. Effect of stocking density on 

growth, survival and development of Asp Aspius aspius (L.), Ide Leuciscus idus (L.) and Chub Leuciscus 

cephalus (L.) larvae during initial rearing under laboratory conditions. Italian Journal of Animal Science

10: 178-184 (2011).

Kutsokon, Y., A. Tsyba, and Y. Kvach. The occurrence of the Chinese Sleeper Perccottus glenii

Dybowski, 1877 in the Southern Bug River Basin, Ukraine. BioInvasions Records 3 (1): 45-48 (2014).
1573

Kvach, Y. First record of Chinese Sleeper Perccottus glenii Dybowski, 1877 in the Ukrainian part of the 

Danube delta. BioInvasions Records 1 (1): 25-28 (2012).

Kvach, Y., and C.A. Stepien. Metazoan parasites of introduced Round and Tubenose Gobies in the Great 

Lakes: support for the “enemy release hypothesis”. Journal of Great Lakes Research 34: 23-35 (2008).

Kvach, Y. and K. Mierzejewska. Non-indigenous benthic fishes as new hosts for Bucephalus 

polymorphus Baer, 1827 (Digenea: Bucephalidae) in the Vistula River basin, Poland. Knowledge and 

Management of Aquatic Ecosystems 400: 02 (2011).

L’avrinčíková, M., and V. Kováč. Invasive Round Goby Neogobius melanostomus from the Danube 

mature at small size. Journal of Applied Ichthyology 23 (3): 276-278 (2007).

L’avrinčíková, M., V. Kováč, and S. Katina. Ontogenetic variability in external morphology of Round 

Goby Neogobius melanostomus from Middle Danube, Slovakia. Journal of Applied Ichthyology 21 (4): 

328-334 (2005).

L’vova, A., A. Palij, and N. Sokolova. Ponto-kaspijskie vselency v reke Moskve v cherte g. Moskvy. 

Zoologicheskij Zhurnal 75: 1273-1274 (1996).

Labrada, R., and L. Fornasari. Management of problematic aquatic weeds in Africa. Food and Agriculture 

Organization of The United Nations, Rome (2002).

Laird, C.A., and L.M. Page. Non-native fishes inhabiting the streams and lakes of Illinois. Illinois Natural 

History Survey Bulletin 35 (1): 1-51 (1996).

Lake County Health Department and Community Health Center. Invasive plant is big problem for lakes 

and ponds. Cattail Chronicles Issues Affecting the Surface Waters of Lake County (2009). 

http://health.lakecountyil.gov/Documents/CattailChronicles%20Spring09.pdf

Lammens, E.H., H.W.D. Nie, J. Vijverberg, and W.L.T.V. Densen. Resource partitioning and niche shifts 

of Bream (Abramis brama) and Eel (Anguilla anguilla) mediated by predation of Smelt (Osmerus 

eperlanus) on Daphnia hyalina. Canadian Journal of Fisheries and Aquatic Sciences 42: 1342-1351 

(1985).

Landis, A.M.G., and N.W.R. Lapointe. First record of a Northern Snakehead (Channa argus Cantor) nest 

in North America. Northeastern Naturalist 17(2): 325-332 (2010).

Landis, A.M., N.W.R. Lapointe, and P.L. Angermeier. Individual growth and reproductive behavior in a 

newly established population of Northern Snakehead (Channa argus), Potomac River, USA. 

Hydrobiologia 661: 123-131 (2011). 

Langdon, J.S., and J.D. Humphrey. Epizootic haematopoietic necrosis, a new viral disease in Redfin 

Perch, Perca fluviatilis L., in Australia. Journal of Fish Diseases 10: 289-297 (1987).

Langdon, S.J., R.H. Marrs, C.A. Hosie, H.A. McAllister, K.M. Norris, and J.A. Potter. Crassula helmsii

in U.K. Ponds: Effects on Plant Biodiversity and Implications for Newt Conservation. Weed Technology

18: 1349-1352 (2004).
1574

Langeland, K.A. Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), the perfect aquatic weed. Castanea

61 (3): 293-304 (1996).

Langeland, K.A., and D.L. Sutton. Regrowth of Hydrilla from axillary buds. Journal of Aquatic Plant 

Management 18: 27-29 (1980). 

Langeland, A., and H. Reinertsen. Interactions between phytoplankton and zooplankton in a fertilized 

lake. Holarctic Ecology 5: 253-272 (1982).

Lansdown, R.V. Hydrocharis morsus-ranae. The IUCN Red List of Threatened Species (2014). 

http://www.iucnredlist.org/details/summary/164128/0

Lappalainen, A., M. Rask, H. Koponen, and S. Vesala. Relative abundance, diet and growth of Perch

(Perca fluviatilis) and Roach (Rutilus rutilus) at Tvaerminne, Northern Baltic Sea, in 1975 and 1997: 

responses to eutrophication? Boreal Environment Research 6: 107-118 (2001).

Lappalainen, J., H. Dörner, and K. Wysujack. Reproduction biology of Pikeperch (Sander lucioperca

(L.)) – A review. Ecology of Freshwater Fish 12: 95-106 (2003).

Lappalainen, A., M. Westerbom, and O. Heikinheimo. Roach (Rutilus rutilus) as an important predator on 

Blue Mussel (Mytilus edulis) populations in a brackish water environment, the Northern Baltic Sea. 

Marine Biology 147: 323-330 (2005).

Lara, M.V., P. Casati, and C.S. Andreo. CO2 concentrating mechanism in Egeria densa, as submersed 

aquatic plant. Physiologia Plantarum 115 (4): 487-495 (2002).

Larsen, L.K., and S. Berg. NOBANIS – Invasive Alien Species Fact Sheet – Sander lucioperca. European 

Network on Invasive Alien Species (2011). www.nobanis.org

Laurent, M., C. Garaicoechea., and J.M. Coudin. La fraye du Sander (Lucioperca lucioperca L.) dans 

l’etang de Sanguinet. Bulletin Francais de la Peche et de la Pisciculture 271: 77-78 (1973).

Lawyer, L. Hydrilla treatment starts in Cayuga Inlet- more eradication work coming in spring in larger 

area. New York Sea Grant (2011). http://www.seagrant.sunysb.edu/articles/t/nysg-partners-for-treatmentof-invasive-hydrilla-plant-in-cayuga-inlet-aquatic-invasive-species-news

Leach, J.H. Impacts of the Zebra Mussel (Dreissena polymorpha) on water quality and fish spawning 

reefs in western Lake Erie. Nalepa, T.F., and D.W. Schloesser (eds). Zebra Mussels: biology, impacts, 

and control. Lewis Publishers. Boca Raton, Florida 381-397 pp. (1993).

Leach, J., and H. Dawson. Crassula helmsii in the British Isles- an unwelcome invader. British Wildlife

234-239 (1999).

Lee, C.E. Evolutionary genetics of invasive species. Trends in Ecology and Evolution 17: 386-391 

(2002).

Legendre, M., O. Linhart, and R. Billard. Spawning and management of gametes fertilized eggs and 

embryos in Siluroidei. Aquatic Living Resources 9: 59-80 (1996).
1575

Lehtonen, H. Potential effects of global warming on northern European freshwater fish and fisheries. 

Fisheries Management and Ecology 3: 59-71 (1996).

Leinonen, K. Recreational Fisheries. Finnish Fisheries in the European Perspective. Statistics and other 

data on fisheries in European Union member countries and Finland, Sweden and Norway. Finnish Game 

and Fisheries Research Institute. Official statistics of Finland. Environment 10: 55-71 (1993).

Lejk, A.M., M. Żdanowicz, M.R. Sapota, and I. Psuty. The settlement of Neogobius fluviatilis (Pallas, 

1814) in Vistula River estuaries (southern Baltic Sea, Poland). Journal of Applied Ichthyology 29 (5): 

1154-1157 (2013).

Lelek, A. The Freshwater Fishes of Europe. Threatened fishes of Europe, AULA-Verlag Wiesbaden 

(1987).

Lelek, A., J. Libosvarsky, M. Penaz, R. Bezdek, and Z. Machacek. Observation on fish under ice in 

winter. Ekologia Polska (Seria A) 12: 305-312 (1964).

Lembi, C.A., B.G. Ritenour, E.M. Iverson, and E.C. Forss. The effects of vegetation removal by Grass 

Carp on water chemistry and phytoplankton in Indian ponds. Transactions of the American Fisheries 

Society 107: 161-171 (1978).

Lenhardt, M., G. Markovic, A. Hegedis, S. Maletin, M. Cirkovic, and Z. Markovic. Non-native and 

translocated fish species in Serbia and their impact on the native ichthyofauna. Reviews in Fish Biology 

and Fisheries 21: 407-421 (2011).

Leonardos, I. and A. Sinis. Age, growth, mortality of Atherina boyeri Risso, 1810 (Pisces: Atherinidae) in 

the Mesolongi and Etolikon lagoons (W. Greece). Fisheries Research 45: 81-91 (2000).

Leonardos, I.D., I. Kagalou, M. Tsoumani, and P.S. Economidis. Fish fauna in a Protected Greek lake: 

biodiversity, introduced fish species over a 80-year period and their impacts on the ecosystem. Ecology of 

Freshwater Fish 17:165-173 (2008).

Leppäkoski, E., and S. Olenin. Non-native species and rates of spread: lessons from the brackish Baltic 

Sea. Biological Invasions 2: 151-163 (2000).

Leppӓkoski, E., S. Gollasch, and S. Olenin. Invasive Aquatic Species of Europe and Distribution, Impacts 

and Management (2002).

Les, D.H., and L.J. Mehrhoff. Introduction of nonindigenous aquatic vascular plants in southern New 

England: a historical perspective. Biological Invasions 1 (2): 281-300 (1999).

Lesutiene, J., E. Gorokhova, Z.R. Gasiunaite, and A. Razinkovas. Isotopic evidence for zooplankton as an 

important food source for the mysid Paramysis lacustris in the Curonian Lagoon, the south-eastern Baltic 

Sea. Estuarine, Coastal, and Shelf Science 73: 73-80 (2007).

Leuven, R., G. Van der Velde, I. Baijens, J. Snijders, C. Van der Zwart, H.J. Lenders, and A. Bij de 

Vaate. The river Rhine: a global highway for dispersal of aquatic invasive species. Biological Invasions

11: 1989-2008 (2009).
1576

Leuven, R.S.E.W., A.J. Hendriks, M.A.J. Huijbregts, H.J.R. Lenders, J. Matthews, and G. Van Der 

Velde. Differences in sensitivity of native and exotic fish species to changes in river temperature. Current 

Zoology 57 (6): 852-862 (2011).

Levengood, J., and D.J. Schaeffer. Polycyclic aromatic hydrocarbons in fish and crayfish from the 

Calumet region of southwestern Lake Michigan. Ecotoxicology 20: 1411-1421 (2011). 

Levings, C., and F. Rafi. Tanais stanfordi Richardson 1901 (Crustacea, Tanaidacea) from the Fraser 

River Estuary, British Columbia. Syesis 11 (1978).

Li, Z.Y., and Y. Xie. Invasive Alien Species in China. China Forestry Publishing House. 211 pp. (2002).

Lieberman, D.M. Use of Silver Carp (Hypophthalmichthys molitrix) and Bighead Carp (Aristichthys 

nobilis) for algae control in a small pond: changes in water quality. Journal of Freshwater Ecology 11: 

391-397 (1996).

Linden, E., B.E. Bengtsson, O. Svanberg, and G. Sundström. The acute toxicity of 78 chemicals and 

pesticide formulations against two brackish water organisms, the bleak (Alburnus alburnus) and the 

harpacticoid (Nitocra spinipes). Chemosphere 8 (11-12): 843-851 (1979).

Linfield, R.S.J., and R.B. Rickards. The Zander in perspective. Fish Management 10 (1): 1-16 (1979).

Linhart, O., L. Štěch, J. Švarc, M. Rodina, J.P. Audebert, J. Grecu, and R. Billard. The culture of the 

European Catfish, Silurus glanis, in the Czech Republic and in France. Aquatic Living Resources 15 (2): 

139-144 (2002).

Linlokken, A.N., E. Bergman, and L. Greenberg. Effect of temperature and Roach Rutilus rutilus group 

size on swimming speed and prey capture rate of Perch Perca fluviatilis and R. rutilus. Journal of Fish 

Biology 76: 900-912 (2010).

Lintermans, M. The decline of native fish in the Canberra region: the impacts of introduced species. 

Bogong 12 (4): 18-22 (1991).

Lintermans, M., T. Rutzou, and K. Kukolic. Introduced fish on the Canberra region. Pollard, D.A. (ed.). 

Introduced and translocated fishes and their ecological effects. Bureau of Rural Resources Proceedings 

no. 8, Australian Government Publishing Services, Canberra 50-60pp. (1990).

Llansó, R.J., and K. Sillett. Hull biofouling of Beaumont reserve fleet vessels pioneer contractor, Mount 

Vernon, and Cape Florida. Versar, Inc. (2009).

Locke, A., D.M. Reid, H.C. Van Leeuwen, W.G. Sprules, and J.T. Carlton. Ballast water exchange as a 

means of controlling dispersal of freshwater organisms by ships. Canadian Journal of Fisheries and 

Aquatic Sciences 50 (10): 2086-2093 (1993). 

Lom, J., and I. Dykova. Protozoan Parasites of Fishes. Developments in Aquaculture and Fisheries 

Science 26 (1992).

Long, N.W. Griffy Lake aquatic vegetation management plan 2008 update-draft, Monroe County, 

Indiana. Aquatic Control (2008). 
1577

Lounibos, L.P., and L.B. Dewald. Oviposition site selection by Mansonia mosquitoes on Water Lettuce. 

Ecological Entomology 14: 413-422 (1989).

Lowe, S., M. Browne, S. Boudjelas, and M. De Poorter. 100 of the world’s worst invasive alien species: a 

selection from the Global Invasive Species Database. The Invasive Species Specialist Group (ISSG), a 

specialist group of the Species Survival Commission (SSC) of the Wor ld Conservation Union (IUCN), 

12 pp. (2000). www.issg.org/booklet.pdf

Ložys, L. The growth of Pikeperch (Sander lucioperca L.) and Perch (Perca fluviatilis L.) under different 

water temperature and salinity conditions in the Curonian Lagoon and Lithuanian coastal waters of the 

Baltic Sea. Hydrobiologia 514: 105-113 (2004).

Lu, Q., Z.L. He, D.A. Graetz, P.J. Stoffela, and X. Yang. Phytoremediation to remove nutrients and 

improve eutrophic stormwaters using Water Lettuce (Pistia stratiotes L.). Environmental Science and 

Pollution Research International 17 (1): 84-96 (2010).

Lusk, S., V. Lusková, K. Halačka, and B. Lojkásek. Changes in the species composition of the 

ichthyofauna in the territory of Czech Republic after 1990. Biodiverzitá ichtiofauny České Republiky 3: 

21-28 (2000). 

Lusk, S., J. Kosco, K. Halacka, L. Vetesnik, and P. Kosuth. Perccottus glenii, an invasive species in the 

Tisza river drainage area, eastern Slovakia. Abstracts of the XI European Congress of Ichthyology (ECI 

XI). Estonia Marine Institute Report Series No. 12, 181 (2004). 

Lusk, S. V. Lusková, and L. Hanel. Alien fish species in the Czech Republic and their impact on the 

native fish fauna. Folia Zoologica 59:57-72 (2010).

Lutz, P.L. Ionic and body compartment responses to increasing salinity in the perch, Perca fluviatilis. 

Comparative Biochemistry and Physiology 42A: 711-717 (1972).

Luzhnyak, V.A. and A.A. Korneev. Modern ichthyofauna of the Lower Don basin in conditions of the 

anthropogenic transformation of its runoff. Journal of Ichthyology 46(7): 525-533 (2006).

Lyakhov, S.M. Floating benthos in Volga River near Kuibyshev before its regulation. Proceedings of AllUnion Hydrobiological Society (Trudy Vsesoyuznogo Gidrobiologicheskogo obshchestva) 11: 150-161 

(1961). 

Lyle, A.A., and P.S. Maitland. The spawning migration and conservation of Smelt Osmerus eperlanus in 

the River Cree, southwest Scotland. Biological Conservation 80: 303-311 (1997).

Maazouzi, C., C. Piscart, F. Legier, and F. Hervant. Ecophysiological responses to temperature of the 

“killer shrimp” Dikerogammarus villosus: Is the invader really stronger than the native Gammarus pulex? 

Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology 159: 268-274 

(2011).

Mabulu, L.Y. Myriophyllum aquaticum (aquatic plant). Global Invasive Species Database (2005). 

http://www.issg.org/database/species/ecology.asp?si=401&fr=1&sts=sss&lang=EN

MacCrimmon, H.R. Animal, man, and change: alien and exotic wildlife of Ontario. McClelland and 

Stewart, Toronto, ON, 160 pp. (1977)
1578

Maceida-Veiga, A., A. de Sostoa, E. Solorio-Ornelas, M. Monroy, D. Vinyoles, N. Caiola, F. Casals, E. 

Garcia-Berthou, and A. Munné. Distribution of alien bleak Alburnus alburnus (Linnaeus, 1758) in the 

Northeastern Iberian Mediterranean Watersheds: past and present (2010).

Maceina, M.J., M.F. Cichra, R.K. Betsill, and P.W. Bettoli. Limnological changes in a large reservoir 

following vegetation removal by Grass Carp. Journal of Freshwater Ecology 7(1):81-95 (1992).

MacInnis, A.J., and L.D. Corkum. Age and growth of Round Goby Neogobius melanostomus in the upper 

Detroit River. Transactions of the American Fisheries Society 129(3): 852-858 (2000).

MacIsaac, H.J. Biological invasions in Lake Erie: past, present and future. Munawar, M., T. Edsall and 

I.F. Munawar (eds.). The State of Lake Erie (SOLE) - Past, Present and Future - A tribute to Drs. Joe 

Leach and Henry Regier. Backhuys Publishers, Netherlands. 305-322 pp. (1999).

MacIsaac, H.J., I.A. Grigorovich, and A. Ricciardi. Reassessment of species invasions concepts: The 

Great Lakes basin as a model. Biological Invasions 3: 405-416 (2001).

MacIsaac, H.J., T.C. Robbins, and M.A. Lewis. Modeling ships’ ballast water as invasion threats to the 

Great Lakes. Canadian Journal of Fisheries Aquatic Science 59: 1245-1256 (2002).

MacNeill, D., P. Bowser, and J. Casey. VHS (Viral Hemorrhagic Septicemia): A Threat to Sustainable 

Fisheries and NY Sea Grant’s Research/Extension Responses. Cornell University, New York Sea Grant

(2009).

Maemets, A. Rotifers as indicators of lake types in Estonia. Hydrobiologia 104: 357-361 (1983).

Magara, Y., Y. Matsui, Y. Goto, and A. Yuasa. Invasion of the non-indigenous nuisance mussel, 

Limnoperna fortunei, into water supply facilities in Japan. Journal of Water Supply: research and 

Technology- AQUA 50 (3): 113- 124 (2001).

Magee, D., and H.E. Ahles. Flora or the Northeast: a manual of vascular flora of New England and 

adjacent New York, p. 131-132. University of Massachusetts Press, Massachusetts (2007). 

Maher, R. 2003 Commercial Catch Report. Illinois Department of Natural Resources, Commercial 

Fishing Program. Brighton, Illinois (2005).

Mailu, A.M. Preliminary assessment of the social, economic, and environmental impacts of water 

hyacinth in the Lake Victoria basin and the status of control. Julien, M.H., M.P. Hill, T.D. Center, and D. 

Jianqing. Biological and integrated control of water hyacinth, Eichhornia crassipes, Australian Centetre 

for International Agriculture Research (ACIAR) Proceedings 102 103-139 pp. (2001). 

Maitland, P., and A. Lyle. The smelt Osmerus eperlanus in Scotland. Freshwater Forum 6: 57-68 (2010).

Maki, K.C., and S.M. Galatowitsch. Cold tolerance of the axillary turions of two biotypes of Hydrilla and 

Northern Watermilfoil. Journal of Aquatic Plant Management 46: 42-50 (2004).

Malik, A. Environmental challenge vis a vis opportunity: the case of Water Hyacinth. Environmental 

International 33 (1): 122-138 (2007).
1579

Malinovskaya, A.S. 1961. On the biology of shrimps acclimatized in the Aral Sea. Sbornik pabot po 

ihtiologii i gidrobiologii (Alma-Ata) 3:113–124 (in Russian)

Mandrak, N.E. Potential invasion of the Great-Lakes by fish species associated with climate warming. 

Journal of Great Lakes Research 15: 306-316 (1989).

Mandrak, N.E., and B. Cudmore. Risk assessment for Asian carps in Canada. Research Document 

2004/103. Fisheries and Oceans Canada (2005).

Mandrak, N.E., and B.C. Cudmore. The fall of native fishes and the rise of non-native fishes in the Great 

Lakes Basin. Aquatic Ecosystem Health and Management 13: 255-268 (2010).

Mandrak, N.E., S. Grafe, A. Lewin, and P. Hunter. Preliminary assessment of the suitability of Canadian 

Great Lakes tributaries for Asian carp spawning. Canadian Manuscript Reports of Fisheries and Aquatic 

Science 2965: vi + 44 pp. (2011).

Mann, R. H. K. Observations on the age, growth, reproduction and food of the Dace, Leuciscus leuciscus

(L.), in two rivers in southern England. Journal of Fish Biology 6 (3): 237-253 (1974).

Mann, R.H.K., Mills, C.A., and D.T. Crisp. 1984. Geographical variation in the life-history tactics of 

some species of fresh-water fish. Potts, G.W. and R.J. Wootton (eds). Fish Reproduction: Strategies and 

Tactics. Academic Press, London. 171-186 pp. (1984).

Mann, R.H.K. and C.A. Mills. Biological and climatic influences on the Dace Leuciscus leuciscus in a 

southern chalk-stream. Fifty-Fourth Annual Report: 83-96 (1986).

Margaritov, N.M., and S.G. Kiritsis. Parasites of Topmouth Gudgeon Pseudorasbora parva (Schlegel) in 

fish farms in Bulgaria. Acta Zoologica Bulgarica 63 (2): 187-193 (2011).

Margolis, L. Public health aspects of ‘codworm’ infections: A review. Journal of the Fisheries Research 

Board of Canada 34: 887-898 (1977).

Marguillier, S., F. Dehairs, G. Van der Velde, B. Kelleher, and S. Rajagopal. Initial results on the trophic 

relationships based on Corophium curvispinum in the Rhine traced by stable isotopes. In: P.H. (1998). 

Marini, F., and Moe, M. The breeder’s net: culture of mysid shrimp and bivalve trochphores (Veligers). 

Advanced Aquarius II (2003). http://www.advancedaquarist.com/2003/9/breeder

Markova, E.L. Results of acclimizations into the Aral Sea during period from 1963 until 1971. 

Akklimatizatsiya ryb I besposvonochnykh v vodoemah SSR: Tezisy dokladov, Sept. 1972. Ilim, Frunze (in 

Russian) 56-58 pp. (1972).

Marques, S.C., U.M. Azeiteiro, S.M. Leandro, H. Queiroga, A.L. Primo, F. Martinho, I. Viegas, and M.A. 

Pardal. Predicting zooplankton response to environmental changes in a temperate estuarine ecosystem. 

Marine Biology 155: 531-541 (2008).

Marsh, C.D. Synopsis of the calanoid crustaceans, exclusive of the Diaptomidae, found in fresh and 

brackish waters, chiefly of North America. Proceedings U.S. National Museum 42 (18) (1933).

Marson, D., B. Cudmore, D.A.R. Drake, and N.E. Mandrak. 2009. Summary of a survey of aquarium 

owners in Canada. Canadian Manuscript Report of Fisheries and Aquatic Sciences 2905: 1-18 (2009). 
1580

Martin, R.G., and J.V. Shireman. A quantitative sampling method for hydrilla inhabiting 

macroinvertebrates. Journal of Aquatic Plant Management 14: 16-19 (1976).

Martino, A. J. Syvaranta, A. Crivelli, R. Cereghino, and F. Santoul. Is European Catfish a threat to eels in 

southern France? Aquatic Conservation: Marine and Freshwater Ecosystems 21: 276-281 (2011).

Massabuau, J.C., and J. Forgue. Les capacites d’adaptation du Silure glane en hypoxie: Un cas exemplair 

d’homostasie du milieu interier. Aquatic Living Resources 8: 423-430 (1995).

Massard, J.A., and G. Geimer. Global diversity of bryozoans (Bryozoa or Ectoprocta) in freshwater: an 

update. Bulletin de la Socie ́te ́ des Naturalistes Luxembourgeois 109: 139-148 (2008).

Masterson, J. Eichhornia crassipes. Smithsonian Marine Station at Fort Pierce (2007). 

http://www.sms.si.edu/IRLSpec/Eichhornia_crassipes.htm Accessed 7 June 2013

Mastitsky, S.E., A.Y. Karatayev, L.E. Burlakova, and B.V. Adamovich. Non-native fishes of Belarus: 

diversity, distribution, and risk classification using the Fish Invasiveness Screening Kit (FISK). Aquatic 

Invasions 5 (1): 103-114 (2010).

Matishov, G.G., D.G. Matishov, S.V. Berdnikov, V.V. Sorokina, S. Levitus, and I.V. Smolyar. Secular 

climate fluctuations in the Sea of Azov region (based on thermohaline data over 120 years). Doklady 

Earth Sciences 422:1101-1104 (2008).

Mauchline, J. The biology of mysids and euphausiids. Advances in Marine Biology 18: 1-681 (1980).

Mayden, R.L. Phylogenetic studies of North American minnows: with emphasis on the genus Cyprinella 

(Teleostei, Cypriniformes). University of Kansas, Lawrence (1989).

Mayden, R.L., and A.M. Simons. Crevice spawning behavior in Dionda dichroma,with comments on the 

evolution of spawning modes in North American shiners (Teleostei: Cyprinidae). Reviews in Fish Biology 

and Fisheries 12: 327-337 (2003).

Mayer, G., G. Maier, A. Maas, and D. Waloszek. Mouthparts of the Ponto-Caspian invader 

Dikerogammarus villosus (Amphipoda: Pontogammaridae). Journal of Crustacean Biology 28: 1-15 

(2008).

Mazepova, G.F. The role of copepods in the Baikal ecosystem. Journal of Marine Systems 15: 113-120 

(1998).

Mazzeo, N., L. Rodriguez-Gallego, C. Kruk, M. Meerhoff, J. Gorga, G. Lacerot, F. Quintas, M. Loureiro, 

D. Larrea, and F. Garcia-Rodriguez. Effect of Egeria densa Planch beds on a shallow lake without 

piscivorous fish. Hydrobiologia 506-509: 591-602 (2003).

McAllister, C.T., W. Starnes, C., M.E. Raley, and H.W. Robison. Geographic distribution records for 

fishes of central and northern Arkansas. Texas Journal of Science 62: 271-280 (2010).

McCann, J., L.N. Arkin, and J.D. Williams. Nonindigenous aquatic and selected terrestrial species of 

Florida-Status, pathway, and time of introduction present distribution, and significant ecological and 

economic effects. Southeastern Biological Science Center, Gainesville. 256 pp. (1996)
1581

McClelland, G. The trouble with sealworms (Pseudoterranova decipiens species complex, Nematoda): a 

review. Parasitology 124: 183-203 (2002).

Mcglynn, Cathy. Illinois ban on invasive aquatic plants includes Hydrilla-aquatic superweeds. Chicago 

Tribune: TribLocal/Winnetka, Northfield & Glencoe Community (2013). 

McGurk, C., D.J. Morris, J.E. Bron, and A. Adams. The morphology of Tetracapsula bryosalmonae

(Myxozoa: Malacosporea) spores released from Fredericella sultana (Bryozoa: Phylactolaemata). 

Journal of Fish Disease 28: 307-312 (2005).

McGurk, C., D.J. Morris, N.A. Auchinoghie, and A. Adams. Development of Tetracapsula bryosalmonae

(Myxozoa: Malacosporea) in bryozoan hosts (as examined by light microscopy) and quantitation of 

infective dose to Rainbow Trout (Oncorhynchus mykiss). Veterinary Parasitology 135: 249-257 (2006).

McHugh, D. A comparative-study of reproduction and development in the polychate family Terebellidae. 

Biological Bulletin 185: 153-167 (1993).

McKnight, S.K., and G.R. Hepp. Potential effects of Grass Carp herbivory on waterfowl foods. Journal of 

Wildlife Management 59(4): 720-727 (1995).

Medina, V.F., S.L. Larson, A.E. Bergstedt, and S.C. McCutcheon. Phyto-removal of trinitrotoluene from 

water with batch kinetic studies. Water Resources 34 (10): 2713-2722 (2000).

Médoc, V., L. Bollache, and J.-N. Beisel. Host manipulation of a freshwater crustacean (Gammarus 

roeseli) by an acanthocephalan parasite (Polymorphus minutus) in a biological invasion context. 

International Journal for Parasitology 36: 1351-1358 (2006).

Mees, J. Paramysis (metamysis) ullskyi. in Mees, J., and K. Meland (eds.). World list of Lophogastrida, 

Stygiomysida and Mysida (2015). 

Mehner, T., J. Ihlau, H. Dörner, and F. Hölker. Can feeding of fish on terrestrial insects subsidize the 

nutrient pools of lakes? Limnol. Oceangr. 50(6): 2022-2031 (2005).

Mendoza, R., S. Contreras, P. Koleff, C. Ramirez, C. Escalera, P. Alvarez, B. Cudmore, N. Mandrak, J.P. 

Fisher, R. Orr, W. Courtenay, G. Greene, and D. Lee. Proposed trinational risk assessment guidelines for 

invasive alien species: test cases for the snakeheads (Channidae) and Armored Catfishes (Loricariidae) in 

North American waters. Commission for Environmental Cooperation (2009).

Mettee, M.F., P.E. O'Neil, and J.M. Pierson. Fishes of Alabama and the Mobile Basin. Oxmoor House, 

Inc. Birmingham, AL. 820 pp. (1996).

Michaletz, P.H., and J.G. Dillard. A survey of catfish management in the United States and Canada. 

Fisheries Management 24(8): 6-11 (1999). 

Michaloudi, E., and M. Kostecka. Zooplankton of Lake Koroneia (Macedonia, Greece). Biologia, 

Bratislava 59 (2): 165-172 (2004).

Michigan Department of Environmental Quality (MDEQ). Tittabawassee River System Assessment Area 

Biota Lists. Stratus Consulting Inc. (2008). 
1582

Michigan Department of Environmental Quality (MI DEQ). Common Aquatic Plants of Michigan Field 

Guide (2012). https://www.michigan.gov/documents/deq/wrd-anc-CommonPlant_408518_7.pdf

Michigan Department of Environmental Quality (MI DEQ). Brazilian Elodea Egeria densa: Member of 

the least wanted. Water Resources Division’s Aquatic Invasive Species of the Week (2013a)! 

https://www.michigan.gov/documents/deq/wrd-ais-week-brazilian-elodea_435544_7.pdf

Michigan Department of Environmental Quality (MI DEQ). Michigan’s Aquatic Invasive Species State 

Management Plan 2013 Update. Prevention, Detection, and Management in Michigan Waters. Michigan 

Department of Environmental Quality. 119pp. (2013b).

Michigan Department of Natural Resources (MIDNR). Department of Natural Resources Wildlife 

Division, Endangered and Threatened Species (2009). http://www.michigan.gov/documents/dnr/2007-

007_NR_Threatened_Endangered_Species__nonstrike__9-12._274586_7.pdf

Michigan DNR (MIDNR). Sample results found Asian carp eDNA in Sandusky Bay (08/28/2012). 

http://www.michigan.gov/dnr/0,4570,7-153-10364_52261_54896-285318--,00.html (2012).

Michigan Department of Natural Resources (MIDNR). Bait Fish (Minnows) (2013). 

http://www.michigan.gov/dnr/0,1607,7-153-10364_18958-229189--00.html

Michigan Department of Natural Resources (MIDNR). Fishing: Fish Identification (2014).

http://www.michigan.gov/dnr/0,1607,7-153-10364_18958---,00.html

Michigan Sea Grant (MSG). Birds of Coastal Michigan (2007). 

http://www.miseagrant.umich.edu/explore/native-and-invasive-species/species/birds/

Mida, J.L., D. Scavia, G.L. Fahnenstiel, S.A. Pothoven, H.A. Vanderploeg, and D.M. Dolan. Long-term 

and recent changes in southern Lake Michigan water quality with implications for present trophic status. 

Journal of Great Lakes Research 36: 42-49 (2010).

Midwest Invasive Species Information Network (MISIN). Water Lettuce (Pistia stratiotes) (2013). 

http://www.misin.msu.edu/facts/detail.php?id=65&cname=Water+lettuce

Mierzejewska, K. Zespół pasoźytów na skrzelach babki lysej (Neogobius gymnotrachelus) w 

Włocławskim Zbiomiku Zaporowym. W. poszukiwaniu parozytów kluczowych w procesie ekspansji 

zywiciela. Wiadomości Parazytologiczne 53: 219 (2007).

Mierzejewska, K., A. Martyniak, T. Kakareko, K. Stanczak, and P. Hliwa, P. Gyrodactylus 

proterorhini Ergens, 1967 (Monogenoidea, Gyrodactylidae) in gobiids from the Vistula River – the first 

record of the parasite in Poland. Parasitology Research 108(5): 1147-1151 (2011).

Mierzejewska, K., Y. Kvach, M. Wozniak, A. Kosowska, and J. Dziekonska-Rynko. Parasites of an Asian 

fish, the Chinese Sleeper Perccottus glenii, in the Wloclawek Reservoir on the Lower Vistula River, 

Poland: in search of the key species in the host expansion process. Comp. Parasitol. 79(1): 23-29 (2012).

Mierzejewska, K., Y. Kvach, K. Stanczak, J. Grabowska, M. Wozniak, Dziekonska-Rynko, and M. 

Ovcharenko. Parasites of non-native gobies in the Wloclawek Reservoir on the lower Vistula River, first 

comprehensive study in Poland. Knowledge and Management of Aquatic Ecosystems 414: 01 (2014).
1583

Mihok, T., P. Košuth, A. Kočišová, L. Pekárik, E. Bártová, and P. Major. The intestinal parasite 

Pseudocapillari tomentosa (Dujardin, 1843) of the invasive fish species Topmouth Gudgeon, 

Pseudorasbora parva (Temminck and Schlegel), in Slovakia. Journal of Fish Diseases 34: 711-714 

(2011).

Millar, A. Final Recommendation: Aquatic Ecological Community in the Natural Drainage System of the 

Lowland Catchment of the Darling River. Reference Number FR 22 File No. FSC 01/10 (2008).

Miller, P.J., and M.J. Loates. Collins Pocket Guide Fishes of Britain and Europe. HarperCollins 

Publishers, 288 pp. (1997).

Mills, C.A. The attachment of Dace Leuciscus leuciscus L., eggs to the spawning substratum and the 

influence of changes in water current on their survival. Journal of Fish Biology 19 (2): 129-134 (1981).

Mills, C.A. The effect of extreme northerly climatic conditions on the life-history of the minnow, 

Phoxinus phoxinus (L.). Journal of Fish Biology 33(4): 545-561 (1988).

Mills, C.A. and R.H.K. Mann. The Bullhead Cottus gobio, a versatile and successful fish. Fifty-First 

Annual Report: 76-88 pp. (1983).

Mills, B.J., and M.C. Geddes. Salinity tolerance and osmoregulation of the Australian freshwater crayfish 

Cherax destructor (Decapoda: Parastacidae). Australian Journal of Marine and Freshwater Research 31: 

667-676 (1980).

Mills, E.L., J.H. Leach, J.T. Carlton, and C.L. Secor. Exotic species in the Great Lakes: a history of biotic 

crises and anthropogenic introductions. Journal of Great Lakes Resources 19: 1-54 (1993).

Milon, J.W., J. Yingling, and J.E. Reynolds. An economic analysis of the benefits of aquatic weed control 

in North-Central Florida, Economics Report No. 113, Food and Resource Economics, Agricultural 

Experiment Station, Institute of Food and Agricultural Sciences. University of Florida, Gainesville, 52 pp. 

(1986).

Minchin, D., C. Maguire, and R. Rosell. The Zebra Mussel (Dreissena polymorpha Pallas) invades 

Ireland: human mediated vectors and the potential for rapid intranational dispersal. Biology and 

Environment: Proceedings of the Royal Irish Academy 103B: 23-30 (2003). 

Mirabdullayev, I.M., I.M. Joldasova, Z.A. Mustafaeva, S. Kazakhbaev, S.A. Lyubimova, and B. A. 

Tashmukhamedov. Succession of the ecosystems of the Aral Sea during its transition from oligohaline to 

polyhaline water body. Journal of Marine Systems 47:101-107 (2004).

Mironga, J.M. The effect of Water Hyacinth Eichhornia crassipes, infestation on phytoplankton 

productivity in Lake Naivasha and the status of control. Proceedings of the 11th world lakes conference 2 

(2006).

Mishima, D., M. Kuniki, K. Sei, S. Soda, M. Ike, and M. Fujita. Ethanol production from candidate 

energy crops: Water Hyacinth (Eichhornia crassipes) and Water Lettuce (Pistia stratiotes L.). 

Bioresource Technology 99: 2495-2500 (2008).

Misisterstva Prosveshcheniya RSFSR. Translated from Russian in 1963 by the Israel Program for 

Scientific Translations, Jerusalem. 626 pp. (1961).
1584

Miura, T. The effects of planktivorous fishes on the plankton community in a eutrophic lake. 

Hydrobiologia 200/201: 567-579 (1990).

Moldoveanu, M., and F. Timofte. Signs of marine ecosystem rehabilitation along the Romanian Black 

Sea littoral identified by zooplankton indicator after 1994. Cercetari Marine 35: 87-108 (2004).

Molloy, D.P., A.Y. Karatayev, L.E. Burlakova, d.P. Kurandina, and F. Laruelle. Natural enemies of Zebra 

Mussels: predators, parasites, and ecological competitors. Reviews in Fish Biology and Fisheries 5: 27-97 

(1997).

Molnár, K. Some remarks on parasitic infections of the invasive Neogobius spp.(Pisces) in the Hungarian 

reaches of the Danube River, with a description of Goussia szekelyi sp. n. (Apicomplexa: Eimeriidae). 

Journal of Applied Ichthyology 22: 395-400 (2006).

Moody, M.L., and D.H. Les. Systematics of the aquatic angiosperm genus Myriophyllum (Halogaceae). 

Systematic Botany 35: 121-139 (2010).

Moravec, F., R. Ergens, and R. Repova. First record of the nematode Pseudocapillaria brevispicula

(Linstow, 1873) from aquarium fishes. Folia Parasitologica 31: 241-245 (1984).

Mordukhaĭ-Boltovskoĭ, F.D. Caspian Fauna Beyond the Caspian Sea. Internationale Revue der gesamten 

Hydrobiologie und Hydrographie 49 (1):139-176 (1964).

Mordukhaĭ-Boltovskoĭ, F.D. Composition and distribution of Caspian fauna in the light of modern data. 

Internationale Revue der gesamten Hydrobiologie und Hydrographie 64 (1): 1-38 (1979a).

Mordukhaĭ-Boltovskoĭ, F.D. The River Volga and its life. Edited by Ph. D. Mordukhaĭ-BoltovskoĭBoltovskoi. The Hague; Boston: W. Junk, 1979. 473 pp. (1979b)

Mordukhaĭ-Boltovskoi, F.D., and Chirkova, E.N. About distribution of Baikalian amphipod Gmelinoides 

fasciatus (Stebbing) in Gor’kovsky Reservoir. Biologiya vnutrennikh vod. Informatsionnyi byulleten 9: 

38-42 (1971).

Mordukhai-Boltovskoi, F.D. and B.S. Kuzin. 1960. Kaspiiskaia fauna v Azovo-Chernomorskom 

basseine. Online translation at agris.fao.org

Mordukhaĭ-Boltovskoi, F.D., and I. Rivier. A brief survey of the ecology and biology of the Caspiaan 

Polyphemoidea. Marine Biology 8 (2): 160 (1971).

Moreno, T., J.J. Castro, and J. Socorro. Reproductive biology of the sand smelt Atherina presbyter 

Cuvier, 1829 (Pisces: Atherinidae) in the central-east Atlantic. Fisheries Research 72: 121-131 (2005).

Morgan, S.G., J.W. Goy, and J.D. Costlow, Jr. Multiple ovipositions from single matings in the Mud Crab 

Rhithropanopeus harrisii. Journal of Crustacean Biology 3: 542-547 (1983).

Morris, D.J., and A. Adams. Transmission of Tetracapsula bryosalmonae (Myxozoa: Malacosporea), the 

causative organism of salmonid proliferative kidney disease, to the freshwater bryozoan Fredericella 

sultana. Parasitology 133: 701-709 (2006).
1585

Morrissy, N.M., and G. Cassells. Spread of the introduced Yabby, Cherax albidus Clark, 1936 in Western 

Australia. Fisheries Research Report No. 92. Western Australia, Australia: Department of Fisheries 

(1992).

Mörtl, M., and K.O. Rothhaupt. Effects of adult Dreissena polymorpha on settling juveniles and 

associated macroinvertebrates. International Review of Hydrobiology 88 (6): 561-569 (2003).

Morton, A., R. Routledge, C. Peet, and A. Ladwig. Sea lice (Lepepophtheirus salmonis) infection rates on 

juvenile Pink (Oncorhynchus gorbuscha) and Chum (Oncorhynchus keta) Salmon in the nearshore 

marine environment of British Columbia, Canada. Canadian Journal of Fisheries and Aquatic Sciences

61: 147-157 (2004).

Moskal’kova, K.I. Ecological and morphophysiological prerequisites to range extention in the round 

goby Neogobius melanostomus under conditions of anthropogenic pollution. Journal of Ichthyology 36 

(8): 584-590 (1996).

Movchan, Y.V. Fauna of Ukraine (Fish). Naukova, Dumka, Kiev. 8: 366 pp. (1988).

Movchan, Y.V., and A. Smirnov. Fauna of Ukraine- Fishes. Dumka Publishing House. Kiev (1981).

Mueller, R.J., and M. Pyron. Fish Assemblages and Substrates in the Middle Wabash River, USA. Copeia 

1:47-53 (2010).

Mulderij, G., W.M. Mooij, A.J.P. Smolders, and E. Van Donk. Allelopathic inhibition of phytoplankton 

by exudates from Stratiotes aloides. Aquatic Botany 82: 284-296 (2005).

Mulderij, G., A.J.P. Smolders, and E. Van Donk. Allelopathic effect of the aquatic macrophyte, Stratiotes 

aloides, on natural phytoplankton. Freshwater Biology 51: 554-561 (2006).

Müller, J., S. Schramm, and A. Seitz. Genetic and morphological differentiation of Dikerogammarus

invaders and their invasion history in Central Europe. Freshwater Biology 47: 2039-2048 (2002).

Museth, J., R. Borgstrøm, J.E. Brittain, I. Herberg, and C. Naalsund. Introduction of the European 

minnow into a subalpine lake: habitat use and long-term changes in population dynamics. Journal of Fish 

Biology 60: 1308-1321 (2002).

Museth, J., R. Borgstrøm, T. Hame, and L.A. Holen. Predation by Brown Trout: a major mortality factor 

for sexually mature European Minnows. Journal of Fish Biology 62: 692-705 (2003).

Museth, J., T. Hesthagen, O.T. Sandlund, E.B. Thorstad, and O. Ugedal. The history of the Minnow 

Phoxinus phoxinus (L.) in Norway: from harmless species to pest. Journal of Fish Biology 71(Supp. D): 

184-195 (2007).

Museth, J., R. Borgstrøm, and J.E. Brittain. Diet overlap between introduced European Minnow 

(Phoxinus phoxinus) and young Brown Trout (Salmo trutta) in the lake, Ovre Heimdalsvatn: a result of 

abundant resources or forced niche overlap? Hydrobiologia 642: 93-100 (2010).

Muskó, I.B. Qualitative and quantitative relationships of Amphipoda (Crustacea) living on macrophytes 

in Lake Balaton (Hungary). Hydrobiologia 191 (1): 269-274 (1990).
1586

Muskó, I.B. Amphipoda (Crustacea) in the littoral zone of Lake Balaton (Hungary). Qualitative and 

quantitative studies. Internationale Revue der Gesamten Hydrobiologie und Hydrographie 74 (2): 195-

205 (1998).

Muskó, I.B. The life history of Dikerogammarus haemobaphes (Eichw.) (Crustacea: Amphipoda) living 

on macrophytes in Lake Balaton (Hungary). Archiv für Hydrobiologie 127 (2): 227-238 (1993).

Muskó, I.B. Occurrence of Amphipoda in Hungary since 1853. Crustaceana 66: 144-152 (1994). 

Muus, B.J., and P. Dahlstrom. The freshwater fishes of Britain and Europe. Collins, London, and 

Glasgow (1978). 

Myers, G.S. Salt tolerance of freshwater fish groups in relation to zoogeographical problems. Bijdragen 

Tot de Dierkund 28: 315-322 (1949). http://people.wku.edu/charles.smith/biogeog/MYER1949.htm

Naberezhny, A.I. Calanoida. Yarochenko, M.F., and A.I. Quay (eds.). Bryozoans, mollusks, arthropods. 

Fauna of Moldova 84-92 pp. (1984).

Nabozhenko, M., and E. Kovalenko. Contemporary distribution of macrozoobenthic communities of the 

Yeisk estuary (Taganrog Bay of the Sea of Azov). Oceanology 51 (4): 626-631 (2011).

Naestad, F., and J.E. Brittain. Long-term changes in the littoral benthos of a Norwegian subalpine lake 

following the introduction of the European Minnow (Phoxinus phoxinus). Hydrobiologia 642: 71-79 

(2010).

Nagata, T., J.Y. Ha, and T. Hanazato. The predation impact of larval (Cyprinidae) on zooplankton: a 

mesocosm experiment. Journal of Freshwater Ecology 20(4): 757-763 (2005).

Naich, M., F.M. Bilqees, and N. Khatoon. Proliferative kidney disease at Romsey fish farm on the River 

Test, Hampshire, UK. Pakistan Journal of Biological Science 6: 1907-1909 (2003).

Najdenova, N.N. Parasite fauna of fishes of the goby family from the Black and Azov seas. Naukova 

Dumka, Kiev, 180 pp. (1974).

Nakano, D., T. Kobayashi, N. Endo, and I. Sakaguchi. Growth rate and settlement of Limnoperna fortunei

in a temperate reservoir. Journal of Molluscan Studies 77 (2): 142-148 (2011).

National Ballast Information Clearinghouse. NBIC Online Database. Electronic publication, Smithsonian 

Environmental Research Center & United States Coast Guard (2009). 

http://invasions.si.edu/nbic/search.html

National Center for Environmental Assessment (NCEA). Effects of Climate Change on Aquatic Invasive 

Species and Implications for Management and Research. United States Environmental Protection Agency 

(USEPA) (2008). 

National Oceanic and Atmospheric Administration (NOAA) Fisheries, Office of Protected Resources. 

Chum Salmon (Oncorhynchus keta) (2014). 

http://www.nmfs.noaa.gov/pr/species/fish/chumsalmon.htm#more
1587

Natural History Museum of London. Stratiotes aloides. Endangered species (2013). 

http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/endangered-species/stratoidesaloides/index.html

Nault, M.E., and A. Mikulyuk. East Indian Hygrophila (Hygrophila polysperma): a technical review of 

distribution, ecology, impacts, and management. Wisconsin Department of Natural Resources Bureau of 

Science Services, Publication SS-1049 2009. Madison, Wisconsin, USA (2009). 

Nechvalenko, S. Changes in the benthic fauna of the Volgograd Reservoir. Pages 50-52 in Saratov, T. 

(ed.). The Lower Volga and Reservoirs on it (1977).

Neff, B.P., and J.R. Killian. The Great Lakes Water Balance: Data Availability and Annotated 

Bibliography of Selected References : United States Department of the Interior, United States Geological 

Survey (USGS) Water-Resources Investigation Report 02-4296 (2003).

Nehring, S. Zur Bestandssituation von Rhithropanopeus harrisii (Gould, 1841) in deutschen Gewassern: 

die sukzessive Ausbreitun eines amerikanischen Neozoons (Crustacea: Decapoda: panopeidae). 

Senckenberg Marit 30: 115-122 (2000).

Nehring, S. The Ponto-Caspian amphipod Obesogammarus obesus (Sars, 1894) arrived the Rhine River 

via the Main-Danube Canal. Aquatic Invasions 1 (3): 148-153 (2006).

Neilson, M.E., and C.A. Stepien. Escape from the Ponto-Caspian: Evolution and biogeography of an 

endemic goby species flock (Benthophilinae: Gobiidae: Teleostei). Molecular Phylogenetics and 

Evolution 52: 84-102 (2009a).

Neilson, M.E., and C.A. Stepien. Evolution and phylogeography of the Tubenose Goby genus 

Proterorhinus (Gobiidae: Teleostei): evidence for new cryptic species. Biological Journal of the Linnean 

Society 96: 664-684 (2009b).

Nekrasova, M.Y. Ecological and biological characteristics of the dominant species of znobenthos in the 

Gulf of Taganrog (Sea of Azov). Hydrobiologia 7: 39-44 (1971).

Nellbring, S. The ecology of Smelts (genus Osmerus): a literature review. Nordic Journal of Freshwater 

Research (1989).

Nesemann, H., M. Pöckl, and K.J. Wittmann. Distribution of epigean Malacostraca in the middle and 

upper Danube (Hungary, Austria, Germany). Miscellanea Zoologica Hungarica 10: 49-68 (1995).

Neuenschwander, P., M.H. Julien, T.D. Center, and M.P. Hill. Pistia stratiotes. Muniappan, R., G.V.P. 

Reddy, A. Raman, and V.P. Gandhi (eds.) Weed Biological Control with Arthropods in the Tropics.

Cambridge University Press, Cambridge 332-353 pp. (2009).

New Invaders Watch Program. 2013. Early detection and rapid response network. Center for Invasive 

Species and Ecosystem Health, University of Georgia (2013). 

http://www.eddmaps.org/tools/xlssub.cfm?sub=3019

New South Wales Department of Private Industries (NSW DPI). Redfin Perch (Perca fluviatilis) (2012a). 

http://www.dpi.nsw.gov.au/fisheries/pests-diseases/freshwater-pests/species/redfin-perch
1588

New South Wales Department of Primary Industries (NSW DPI). Water Hyacinth. Invasive Species Unit 

(2012b). http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0013/330322/Water-hyacinth-web.pdf

New South Wales Department of Primary Industries (NSW DPI). Yabby Cherax destructor (2013a). 

http://www.dpi.nsw.gov.au/fisheries/recreational/freshwater/fw-species/yabby

New South Wales Department of Primary Industries (NSW DPI). Leafy elodea (Egeria densa). 

WeedWise (2013b). http://weeds.dpi.nsw.gov.au/Weeds/Details/182#profile

New York Sea Grant (NYSG). Not Wanted! Hydrilla (Hydrilla verticillata) (2012). 

http://www.seagrant.sunysb.edu/ais/pdfs/Hydrilla-brochure030912.pdf

Nicholls, A.G. Copepods from the interstitital fauna of a sandy beach. Journal of the Marine Biological 

Association of the United Kingdom 20: 397-406 (1935).

Nichols, A.C., T.P. Murray, and T.D. Richardson. Mercury accumulation in catfish (Ictalurus furcatus

and I. punctuates) from the southwestern Tennessee river valley. Southeastern Naturalist 1(2): 159-168 

(2002).

Nico, L., P. Fuller, and M. Neilson. Leuciscus idus. USGS Nonindigenous Aquatic Species Database, 

Gainesville, FL (2012).

Nico, L.G., P.L. Fuller, P.J. Schofield, M.E. Neilson, A.J. Benson, and J. Li. Ctenopharyngodon idella. 

USGS Nonindigenous Aquatic Species Database, Gainesville, FL (2015).

Nienhuis, R.S., E.W. Leuven, and A.M.J. Ragas (eds). New concepts for sustainable management of river 

basins. Backhuys Publishers, Leiden, the Netherlands (1998). 

Niimi, A.J. and D.M. Reid. Low salinity residual ballast discharge and exotic species introductions to the 

North American Great Lakes. Marine Pollution Bulletin 46: 1334-1340 (2003).

Nikol'skii, G.V. Fishes of the Amur Basin. USSR Academy of Sciences. 551 pp. (1956).

Nilsson, N.A. Food and habitat of the fish community of the offshore region of Lake Vanem, Sweden. 

Institute of Freshwater Research, Drottningholm, Report 58: 126-138 (1979).

Ninua, N., and B. Japoshvili. Check List of Fishes of Georgia. Proceedings of the Institute of Zoology

2008: 163-176 (2008).

NOAA CoastWatch. Great Lakes Statistics. NOAA/Great Lakes Environmental Research Laboratory. 

4840 S. State Rd. Ann Arbor, MI 48108-9719 (2014). 

http://coastwatch.glerl.noaa.gov/webdata/cwops/html/statistic/statistic.html

NOAA Fisheries, Office of Protected Resources. Chum Salmon (Oncorhynchus keta) (2014). 

http://www.nmfs.noaa.gov/pr/species/fish/chumsalmon.htm#more

Noges, P., and A. Jarvet. Climate driven changes in the spawning of Roach (Rutilus rutilus (L.)) and 

Bream (Abramis brama (L.)) in the Estonian part of the Narva River basin. Boreal Environment Research 

10: 45-55 (2005). 
1589

Nolte, A.W., J. Freyhof, K.C. Stemshorn, and D. Tautz. An invasive lineage of sculpins, Cottus sp. 

(Pisces, Teleostei) in the Rhine with new habitat adaptations has orginated from hybridization between 

old phylogeographic groups. Proceedings of the Royal Society B 272: 2379-2387 (2005).

Noordhuis, R., J. van Schie, and N. Jaarsma. Colonization patterns and impacts of the invasive amphipods 

Chelicorophium curvisipinum and Dikerogammarus villosus in the Ijsselmeer area, The Netherlands. 

Biological Invasions 11: 2067-2084 (2009).

Normant, M., J. Miernik, and A. Szaniawska. Remarks on the morphology and the life cycle of 

Rhithropanopeus harrisii ssp. tridentatus (Maitland) from the Dead Vistual River. Oceanological and 

Hydrobiological Studies 33 (4): 93-102 (2004).

Norsk institutt for naturforskning (NINA). Daphnia cristata Sars 1861 (2007). 

http://www.nina.no/archive/nina/PppBasePdf/NINAInfomateriell/2007/krepsdyrfaktaark/walseng_Daphnia%20cristata.pdf

North American Invasive Species Network. Waterhyacinth (2013). 

http://www.naisn.org/profile.html?sub=3020 Accessed 7 June 2013

North Carolina Agricultural Extension Service. Hydrilla: a rapidly spreading aquatic weed in North 

Carolina, May 1992. Publication Number AG-449 (1992). 

http://www.weedscience.ncsu.edu/aquaticweeds/hydrilla.PDF

Northcote, T.G., and J. Hammar. Feeding ecology of Coregonus albula and Osmerus eperlanus in the 

limnetic waters of Lake Mälaren, Sweden. Boreal Environment Research 11: 229-246 (2006).

Northeast Aquatic Nuisance Species Panel. North Atlantic amphipod invades Illinois River. Resource 

Digest 2 (Issue 3): 2 (2003). 

Northeast Ecological Services (NES), United States Fish and Wildlife Service. Hydrilla closes in on the 

Great Lakes (2012). http://ne-ecological-services.blogspot.com/2012/10/hydrilla-closes-in-on-greatlakes.html.

Northern Snakehead Working Group (NSWG). National control and management plan for members of 

the snakehead family (Channidae). Department of the Interior, Aquatic Nuisance Species Task Force 

(2014). http://www.anstaskforce.gov/Species%20plans/SnakeheadPlanFinal_5-22-14.pdf

Nunn, A.D., I.G. Cowx, P.A. Frear, and J.P. Harvey. Is water temperature an adequate predictor of 

recruitment success in cyprinid fish populations in lowland rivers? Freshwater Biology 48: 579-588

(2003). 

Nwoko, C.O. Trends in phytoremediation of toxic elemental and organic pollutants. African Journal of 

Biotechnology 9 (37): 6010-6016 (2010).

NY DEC (New York Department of Environmental Conservation). Hydrilla discovered in Erie Canal in 

North Tonawanda: highly invasive aquatic plant threatens New York’s waters. Regional Press (2012). 

http://www.dec.ny.gov/press/85078.html

Nyberg, P. Biotic effects in planktonic crustacean communities in acidified Swedish forest lakes after 

liming. Water Air and Soil Pollution 101 (1): 257-288 (1998).
1590

O’Connor, M., C. Hawkins, and D.K. Loomis. A manual of previously recorded non-indigenous invasive 

and native transplanted animal species of the Laurentian Great Lakes and coastal United States. NOAA 

Technical Memorandum NOS NCCOS 77. 82 pp. (2008)

Occhipinti Ambrogi, A., and J.L. d’ Hondt. Distribution of Bryozoans in brackish waters of Italy. 

Larwood, G.P., C. Nielsen (eds.). Recent and fossil Bryozoa. Olsen & Olsen, Fredensborg 191-198 pp. 

(1981). 

Odenkirk, and S. Owens. Northern Snakehead in the tidal Potomac River System. Transactions of the 

American Fisheries Society 134: 1605-1609 (2005).

Odjegba, V.J. and I.O. Fasidi. Accumulation of trace elements by Pistia stratiotes: Implications for 

phytoremediation. Ecotoxicology 13:637-646 (2004).

Odum, E. Ecology. Moscow. 560 pp. (1968).

Ogawa, K., T. Nakatsugawa, and M. Yasuzaki. Heavy metacercarial infections of cyprinid fishes in Uji 

River. Fisheries Science 70: 132-140 (2004).

O'hara, K. An Ecological Study of Fishes, with Particular Reference to Freshwater Species, in the Welsh 

Dee at Chester. PhD Thesis, University of Liverpool (1976).

Ohayon, J.L., and C.A. Stepien. Genetic and biogeographic relationships of the Racer Goby Neogobius 

gymnotrachelus (Gobiidae: Teleostei) from introduced and native Eurasian locations. Journal of Fish 

Biology 71 (Supp. C): 360-370 (2007).

Ojaveer, E. Large-scale processes in the ecosystem of the Gulf of Riga. Ojaveer, E. (ed.). Ecosystem of 

the Gulf of Riga between 1920 and 1990. Estonian Academy Publishers, Tallinn 268-277 pp. (1995). 

Ojaveer, H., E. Leppakoski, S. Olenin, and A. Ricciardi. Ecological impact of Ponto-Caspian invaders in 

the Baltic Sea, European inland waters and the Great lakes: An inter-ecosystem comparison. Invasive 

Aquatic Species of Europe. Distribution, Impacts and Management pp. 412-425 (2002).

Okada, Y. Studies of the freshwater fishes of Japan, II, special part. Journal of the Faculty of Fisheries 

Prefectual University of Mie 4: 31-860 (1960).

Okamura, B., and T.S. Wood. Bryozoans as hosts for Tetracapsula bryosalmonae, the PKX organism. 

Journal of Fish Diseases 25: 469-475 (2002).

Økland J., and K.A. Økland. Freshwater bryozoans (Bryozoa) of Norway V: review and comparative 

discussion of the distribution and ecology of the 10 species recorded. Hydrobiologia 534: 31-55 (2005).

Olenin, S., and E. Leppäkoski. Non-native animals in the Baltic Sea: alteration of benthic habitats in 

coastal inlets and lagoons. Hydrobiologia 393: 233-243 (1999).

Olenin, S., D. Minchin, and D. Daunys. Assessment of biopollution in aquatic ecosystems. Marine 

Pollution Bulletin 55 (7-9): 379-394 (2007).

Olenin, S., D. Minchin, D. Daunys, and A. Zaiko. Biological pollution of aquatic ecosystems in Europe. 

Atlas of Biodiversity Risk. 136-137 pp. (2010).
1591

Olesen, T.M., J.G. Nielsen, and P.R. Möller. Bandgeundling Pseudorasbora parva (Temminck & 

Schlegel, 1864) ny ynglefisk I Danmark. Flora og Fauna 109 (1): 1-5 (2003).

Olesen, A.J., and O.S. Tendal. Amerikansk brakvandskrabbe- ny krabbeart etableret i Danmark. 

Zoologisk Museum 2: 26-28 (2009).

Oliveira, M., S.K. Hamilton, and C.M. Jacobi. Forecasting the expansion of the invasive Golden Mussel 

Limnoperna fortunei in Brazilian and North American rivers based on its occurrence in the Paraguay 

River and Pantanal wetland of Brazil. Aquatic invasions 5 (1): 59-73 (2010).

Oliveira, M.D., D.F. Calheiros, C.M. Jacobi, and S.K. Hamilton. Abiotic factors controlling the 

establishment and abundance of the invasive Golden Mussel Limnoperna fortunei. Biological Invasions

13 (3): 717-729 (2011).

Omarov, O.P., and O.A. Popova. Feeding behavior of Pike, Esox lucius, and catfish, Silurus glanis, in the 

Arakum Reservoirs of Dagestan. Journal of Icthyology 25: 25-36 (1985).

Ondračková, M., M. Dávidová, M. Pečinková, R. Blažek, M. Gelnar, Z. Valová, J. Černy, and P. Jurajda. 

Metazoan parasites of Neogobius fishes in the Slovak section of the River Danube. Journal of Applied 

Ichthyology 21: 345-349 (2005).

Ondracková, M., I. Matéjusová, and J. Grabowska. Introduction of Gyrodactylus perccotti (Monogenea) 

into Europe on its invasive fish host, Amur sleeper (Perccottus glenii, Dybowski 1877). Helminthologia

49 (1): 21-26 (2012a).

Ondračková, M., I. Slováčková, T. Trichkova, M. Polačik, and P. Jurajda. Shoreline distribution and 

parasite infection of Black-striped Pipefish Syngnathus abaster Risso, 1827 in the lower River Danube. 

Journal of Applied Ichthyology 28: 590-596 (2012b)

Onikura, N., and J. Nakajima. Age, growth and habitat use of the Topmouth Gudgeon, Pseudorasbora 

parva in irrigation ditches on northwestern Kyushu Island, Japan. Journal of Applied Ichthyology 29: 

186-192 (2013).

Ontario Ministry of Natural Resources (OMNR). Water Soldier (Stratiotes aloides) (2009). 

http://www.mnr.gov.on.ca/stdprodconsume/groups/lr/@mnr/@biodiversity/documents/document/stdprod

_104417.pdf

Ontario Ministry of Natural Resources (OMNR). Field Guide to Aquatic Invasive Species (2010). 

http://www.web2.mnr.gov.on.ca/mnr/Biodiversity/Invasive_Species/field_guide_aquatic_invasive_specie

s.pdf

Ontario Ministry of Natural Resources (OMNR). Water Soldier (Stratiotes aloides). Ontario’s Invading 

Species Awareness Program (2013).

Ooms-Wilms, A.L., G. Postema, and R.D. Gulati. Clearance rates of bacteria by the rotifer Filinia 

longiseta (Ehrb.) measured using three tracers. Hydrobiologia 255/256: 255-260 (1993).

Opisov, V.V., and V.I. Kiyashko. Specific features of the reproduction of Clupeonella cultrivensis

(Clupeiformes, Clupeoidei) at the introduction into freshwater water bodies. Journal of Ichthyology 40(7): 

574-576 (2006).
1592

Opuszynski, K. The role of fishery management in counteracting eutrophication processes. Developments 

in Hydrobiology 2: 263-269 (1980).

Opuszynski, K. Comparison of the usefulness of the silver carp and bighead carp as additional fish in carp 

ponds. Aquaculture 25 (2-3): 223-233 (1981).

Opuszynski, K., and J.V. Shireman. Herbivorous fishes, culture and use for weed management. CRC 

press. 223 pp. (1995).

Orchard, A.E. A revision of South American Myriophyllum (Haloragaceae), and its repercussions on 

some Australian and North American species. Brunonia 4: 27-65 (1981).

Orlova, M.I., I.V. Telesh, N.A. Berezina, A.E. Antsulevich, A.A. Maximov, L.F. Litvinchuk. Effects of 

nonindigenous species on diversity and community functioning in the eastern Gulf of Finland (Baltic 

Sea). Helgoland Marine Research 60: 98-105 (2006).

Orr, B.K., and V.H. Resh. Influence of Myriophyllum aquaticum cover on Anopheles mosquito 

abundance, oviposition, and larval microhabitat. Oecologia 90: 474-482 (1992).

Orrell, T.M., and L. Weigt. The Northern Snakehead Channa argus (Anabantomorpha: Channidae), a 

non-indigenous fish species in the Potomac River, U.S.A. Proceedings of the Biological Society of 

Washington 118(2): 407-415 (2005).

Osceola County. Hydrilla & Hygrophila Demonstration Project FAQ’s. University of Florida (2012). 

http://plants.ifas.ufl.edu/osceola/faq.html#benefitshydrilla

Oscoz, J., P.M. Leunda, R. Miranda, and M.C. Escala. Summer feeding relationships of the co-occuring 

Phoxinus phoxinus and Gobio lozanoi (Cyprinidae) in an Iberian river. Folia Zoologia 55 (4): 418-432 

(2006).

Osumo, W.M. Effects of Water Hyacinth on water quality of Winum Gulf, Lake Victoria. UNU- Fisheries 

Training Programme (2001). http://www.unuftp.is/static/fellows/document/osumoprf.pdf

Ovcarenko, I., A. Audzijonytė, and Z. Gasiunaite. Tolerance of Paramysis lacustris and Limnomysis 

benedeni (Crustacea, Mysida) to sudden salinity changes: implications for ballast water treatment. 

Oceanologia 48: 231-242 (2006).

Ovcharenko, M.O., K. Bacela, T. Wilkinson, J.E. Ironside, T. Rigaud, and R.A. Wattier. Cucumispora 

dikerogammari n. gen. (Fungi: Microsporidia) infecting the invasive amphipod Dikerogammarus villosus: 

a potential emerging disease in European rivers. Parasitology 137: 191-204 (2010).

Owens, C.S., and J.D. Madsen. Low temperature limits of Waterhyacinth. Journal of Aquatic Plant 

Management 33: 63-68 (1995).

Owens, C.S., J.D. Madsen, R.M. Smart, and R.M. Stewart. Dispersal of native and nonnative aquatic 

plant species in the San Marcos River, Texas. Journals of Aquatic Plant Management 39: 75-79 (2001).

Özeren, C.S. Iznik Gölü baliklarinin taksonomisi ve Cyprinus carpio L., 1758 (Sazan), Rutilus 

frisii Nordmann, 1840 (Akbalik) ve Atherina boyeri Risso,1810 (Gümüs baligi)’nin biyo-ekolojik yönden 

incelenmesi. PhD thesis, Ankara: Hacettepe University, 224 pp. (2004).
1593

Özulug, A.S., M. Tarkan, O. Gaygusuz, and C. Gürsoy. Two new records for the fish fauna of Lake 

Sapanca Basin (Sakarya, Turkey). Journal of Fisheries Science 1: 152-159 (2007).

Paavola, M., Olenin, S., Leppäkoski, E. Are invasive species most successful in habitats of low native 

species richness across European brackish water seas? Estuarine, Coastal, and Shelf Science 64: 738-750 

(2005).

Padhi, A. Climate-driven population dynamics of a North American freshwater fish, Ictalurus furcatus: 

inference from the mitochondrial control region sequence data. Ecology of Freshwater Fish 20: 263-269 

(2011).

Padilla, D.K., and S.L. Williams. Beyond ballast water: aquarium and ornamental trades as sources of 

invasive species in aquatic ecosystems. Frontiers in Ecology and the Environment 2 (3): 131-138 (2004).

Paffen, B., F. van den Brink, G. van der Velde, and A. bij de Vaate. The population explosion of the 

Amphipod Corophium curvispinum in the Dutch Lower Rhine. Water Science and Technology 29 (3): 53-

55 (1994).

Page, L.M., and B.M. Burr. A field guide to freshwater fishes of North America north of Mexico. 

Houghton Mifflin Company, Boston (1991). 

Page, L.M., and B.M. Burr. Field guide to freshwater fishes. Peterson Field Guides. Houghton Mifflin 

Company, New York (2011).

Pak, J.H., J.H. Moon, S.J. Hwang, S.H. Cho, S.B. Seo, and T.S. Kim. Proteomic analysis of differentially 

expressed proteins in human cholangiocarcinoma cells treated with Clonorchis sinesis excretory-secretory 

products. Journal of Cell Biochemistry 108: 1376-1388 (2009).

Pampouli, C., S. Morand, A. Lambert, E. Rosecchi, J.L. Bouchereau, and A.J. Crivelli. Influence of the 

trematode Aphalloides coelomicola Dollfus, Chabaud, and Golvan, 1957 on the fecundity and survival of 

Pomatoschistus microps (Kroyer, 1838) (Teleostei: Gobiidae). Parasitology 119 (1): 61-7 (1999). 

Panov, V. Pseudorasbora parva. Delivering Alien Invasive Species in Europe (DAISIE) (2006).

Panov, V.E., P.I. Krylov, and I.V. Telesh. The St. Petersburg harbor profile. Pages 224-244 in Gollasch, 

S., and E. Leppäkoski (eds.). Initial Risk Assessment of Alien Species in Nordic Coastal Waters. Nord 

1999: 8. Nordic Council of Ministers, Copenhagen (1999).

Panov, V, N. Rodionova, P. Bolshagin, and E. Bychek. Invasion biology of Ponto-Caspian onychopod 

cladocerans (Crustacea: Cladocera: Onychopoda). Hydrobiologia 590 (1): 3-14 (2007).

Panov, V.E., B. Alexandrov, K. Arbačiauskas, R. Binimelis, G.H. Copp, M. Grabowski, F. Lucy, 

R.S.E.W. Leuven, S. Nehring, and M. Paunović. Assessing the risks of aquatic species invasions via 

European inland waterways: from concepts to environmental indicators. Integrated Environmental 

Assessment and Management 5 (1): 110-126 (2009).

Paolucci, E.M., D.H. Cataldo, C.M. Fuentes, and D. Boltovskoy. Larvae of the invasive species 

Limnoperna fortunei (Bivalvia) in the diet of fish larvae in the Parana River, Argentina. Hydrobiologia 

589: 219-233 (2007).
1594

Paolucci, E.M., E.V. Thuesen, D.H. Cataldo, and D. Boltovskoy. Veligers of an introduced bivalve, 

Limnoperna fortunei, are a new food resource that enhances growth of larval fish in the Paraná River 

(South America) Introduced veligers enhance fish growth. Freshwater Biology 55 (9): 1831-1844 (2010).

Papasissi, C. Atherine boyeri Risso, 1810. FishBase (2013). http://www.fishbase.se/summary/Atherinaboyeri.html

Parker J.D., C.C. Caudill, and M.E. Hay. Beaver Herbivory on Aquatic Plants. Oecologia 151 (4): 616-

625 (2007). 

Parsons, W.T., and E.G. Cuthbertson. Noxius weeds of Australia, 2nd Edition, CSIRO Publishing, 

Collingwood VIC, Australia (2001).

Payen, G.G., and J.-R. Bonami. Mise en evidence de particules d'allure virale associees aux noyaux des 

cellules mesodermiques de la zone germinative testiculaire du crabe Rhithropanopeus harrisii (Gould) 

(Brachyoure, Xanthide). Revue des Travaux de l’Institute des Peches Maritimes 43: 361-365 (1979).

Peltonen, H., H. Rita, and J. Ruuhijӓrvi. Diet and prey selection of Pikeperch (Stizostedion lucioperca

(L.)) in Lake Vesijӓrvi analysed with a logit model. Annales Zoologica Fennales 33: 481-487 (1996).

Peltonen, H., T. Malinen, and A. Tuomaala. Hydroacoustic in situ target strength of Smelt (Osmerus 

eperlanus (L.). Fisheries Research 80:190-195 (2006).

Pennsylvania Sea Grant (PA Sea Grant). Pennsylvania's Field Guide to Aquatic Invasive Species. 185 pp. 

(2013).

Pérez-Bote, J.L. First record of the European catfish Silurus glanis Linnaeus, 1758 (Siluriformes, 

Siluridae) in the Alcantara reservoir (Tagus basin, Spain). Anales de Biologia 31: 59 (2009).

Perez-Bote, J., R. Roso, H. Pula, F. Díaz, and M.T. López. Primeras citas de 

lucioperca, Sander (= Stizostedion) lucioperca (Linnaeus, 1758) y del alburno, Alburnus alburnus 

(Linnaeus, 1758) en las cuencas extremeñas de los rios Tajo y Guadiana, SO de la Península Ibérica. 

Anales de Biología 26: 93-100 (2004).

Perry, W.G., Jr. Distribution and relative abundance of Blue Catfish, Ictalurus furcatus, and Channel 

Catfish, Ictalurus punctuates, with relation to salinity. Proceedings of the Southeastern Association of 

Game Fish Commissions 21: 436-444 (1968).

Persson, J., and T. Vrede. 2006. Polyunsaturated fatty acids in zooplankton: variation due to taxonomy 

and trophic position. Freshwater Biology 51: 887-900.

Persson, J., and T. Vrede. Polyunsaturated fatty acids in zooplankton: variation due to taxonomy and 

trophic position. Freshwater Biology 51: 887-900 (2006).

Persson, A., and C. Brönmark. Pikeperch Sander lucioperca trapped between niches: foraging 

performance and prey selection in a piscivore on a planktivore diet. Journal of Fish Biology 73: 793-808 

(2008).

Pesacreta, G. Water chemistry from North Carolina Piedmont impoundments with Hydrilla (Hydrilla 

verticillata L.f. Royle). Ph.D. dissertation, North Carolina State University, Raleigh, NC (1988).
1595

Petkovski, T.K., and T. Karanovic. Two new copepod species (Crustacea: Copepoda) from the Ohrid 

Lake. Annales Limnology 33 (4): 245-253 (1997).

Petr, T, and V.P. Mitrofanov. The impact on fish stocks of river regulation in Central Asia and 

Kazakhstan. Lakes & Reservoirs: Research and Management 3: 143-164 (1998).

Petrusek, A., Bastiansen, F., and Schwenk, K. European Daphnia species (EDS)- Taxonomic and genetic 

keys. [Build 2006-01-12 beta]. CD-ROM, distributed by the authors. Department of Ecology and 

Evolution. J.W. Goethe-University, Frankfurt am Main, Germany & Department of Ecology, Charles 

University, Prague, Czechia (2005). 

Pfleiger, W.L. Reproductive behavior of the minnows, Notropis spilopterus and Notropis whippli. Copeia

1:1-8 (1965).

Pflieger, W.L. The fishes of Missouri. Missouri Department of Conservation, Jefferson City, MO (1997).

Philip, C.B. Studies on Transmission of experimental Yellow Fever by Mosquitoes other than Aëdes. 

American Journal of Tropical Medicine 10: 1-16 (1930).

Phillips, R., and M. Rix. Freshwater Fish of Britain, Ireland and Europe. Pan Books Ltd., London 

(1985).

Phillips, R., and M. Rix. A guide to Freshwater Fish of Britain, Ireland, and Europe. Pan Macmillan 

Books Ltd., London, England (1988).

Phong, T.V., N. Tuno, H. Kawada, and M. Takagi. Comparative evaluation of the fecundity and 

survivorship of six copepod (Copepoda:Cyclopidae) species, in relation to selection of candidate 

biological control agents against Aedes aegyptii. Journal of the American Mosquito Control Association 

24(1)61-69 (2008) 

Pienimäki, M., and E. Leppäkoski. Invasion pressure on the Finnish Lake District: invasion corridors and 

barriers. Biological Invasions 6: 331-346 (2004).

Piepiorka, S., and T. Walter. Schwebgarnelen - mehr als nur Fischfutter. Deutsche Aquarien und 

Terrarien Zeitschrift. August edition, 56-59 pp. (2006).

Pieterse, A.H., L.D. Lange, and L. Verhagen. A study on certain aspects of seed germination and growth 

of Pistia stratiotes L. Acta Botanica Neerlandica 30: 47-57 (1981).

Pijanowska, J. Anti-predator defense in 3 daphnia species. International Review of Hydrobiology 77(1): 

153-163 (1992). 

Pinchuk, V.I. About speciation within the genus Neogobius (Perciformes). Voprosy Ikhtiologii 31: 180-

393 (1991).

Pinchuk, V.I., E.D. Vasil’eva, V.P. Vasil’ev, and P.J. Miller. Neogobius gymnotrachelus (Kessler, 1857). 

Pp. 265-279 in: Miller, P.J. (ed.). The freshwater fishes of Europe vol. 8/I Mugilidae, Atherinopsidae, 

Blenniidae, Odontobutidae, Gobiidae 1. Wiesbaden (Aula-Verlag) (2003).
1596

Pinder, A.C., R.E. Gozlan, and J.R. Britton. Dispersal of the invasive Topmouth Gudgeon, 

Pseudorasbora parva in the UK: a vector for an emergent infectious disease. Fisheries Management and 

Ecology 12 (6): 411-414 (2005).

Pine, R.T., L.W.J. Anderson, and S.S.O. Hung. Control of aquatic plants in static flowing water by 

yearling triploid Grass Carp. Journal of Aquatic Plant Management 28: 36-40 (1990).

Pine, R.T., and L.W. Anderson. Plant preferences of triploid Grass Carp. Journal of Aquatic Plant 

Management 29: 80-82 (1991).

Pinkster, S. A revision of the genus Echinogammarus (Stebbing, 1899) with some notes on related genera 

(Crustacea, Amphipoda). Memorie del Museo di storia natural (II° serie) Scienze della vitta (a Biologia)

10: 170-172 (1993).

Pinnock, W. A catechism of ichthyology: being a familiar introduction to the natural history of fishes, 

scientifically arranged. Mentorian Press, Harvard University. 72 pp. (1820).

Pinto, C.L.R., A. Caçonia, and M.M. Souza. Utilization of Water Hyacinth for removal and recovery of 

silver from industrial wastewater. Water Science and Technology 19 (10): 89-101 (1987).

Pislegina, E., and E. Silow. Long-term dynamics of Baikal zooplankton and climate change. Materials of 

World Lake 13 (2009).

Pjatakova, G.M., and A.G. Tarasov. Caspian Sea amphipods: biodiversity, systematic position and 

ecological pecularities of some species. International Journal of Salt Lake Research 5: 63-79 (1996).

Plachá, M., M. Balážová, V. Kovác, and S. Katina. 2010. Age and growth of non-native Monkey Goby 

Neogobius fluviatilis (Teleostei, Gobiidae) in the River Ipel’, Slovakia. Folia Zoologica 59(4): 332-340

(2010).

Platvoet, D., J.T.A. Dick, C. MacNeil, M. van Reil, and G. van der Velde. Invader-invader interactions in 

relation to environmental heterogeneity leads to zonation of two invasive amphipods, Dikerogammarus 

villosus (Sowinsky) and Gammarus tigrinus Sexton: amphipod pilot species project (AMPIS) report 6. 

Biological Invasions 11: 2085-2093 (2009).

Plotnikov, I.S., N.V. Aladin, D. Keyser, and Z.K. Ermakhanov. Transformation of aquatic animal 

biodiversity in the Aral Sea. It is not dying, but transforming in accordance with water availability and its 

salinity. Towards a Sustainable Society in Central Asia: An Historical Perspective on the Future. 1-26 

pp. (2012).

Pöckl, M. Strategies of a successful new invader in European fresh waters: fecundity and reproductive 

potential of the Ponto-Caspian amphipod Dikerogammarus villosus in the Austrian Danube, compared 

with the indigenous Gammarus fossarum and G. roeseli. Freshwater Biology 52: 50-63 (2007).

Pöckl, M. Success of the invasive Ponto-Caspian amphipod Dikerogammarus villosus by life history traits 

and reproductive capacity. Biological Invasions 11: 2021-2041 (2009).

Pohl, C. Skeletal deformities and trace metal contents of European Smelt, Osmerus eperlanus, in the Elbe 

Estuary. Meeresforsch 33:76-89 (1990).
1597

Polaçik, M., M. Janáç, T. Trichkova, M. Vassilev, and P. Jurajda. The distribution and abundance of 

the Neogobius fishes in their native range (Bulgaria) with notes on the non-native range in the Danube 

River. Large Rivers 18: 193-208 (2008).

Polaçik, M., M. Janác, P. Jurajda, Z. Adámek, M. Ondračková, T. Trichkova, and M. Vassilev. Invasive 

gobies of the Danube: invasion success facilitated by availability and selection of superior food resources. 

Ecology of Freshwater Fish 28 (4): 640-649 (2009).

Polomski, R., M. Taylor, D. Bielenberg, W. Bridges, S. Klaine, and T. Whitwell. Nitrogen and 

phosphorus remediation by three floating aquatic macrophytes in greenhouse-based laboratory-scale 

subsurface constructed wetlands. Water, Air, and Soil Pollution 197: 223-232 (2009).

Pombo, L., M. Elliot, and J.E. Rebelo. Ecology, age and growth of Atherina boyeri and Atherina 

presbyter in the Ria de Aveiro, Portugal. Cybium 29(1): 47-55 (2005).

Pongruktham, O., C. Ochs, and J. Hoover. Observations of Silver Carp (Hypophthalmichthys 

molitrix) planktivory in a floodplain lake of the lower Mississippi River Basin. Journal of Freshwater 

Ecology 25:85-93 (2010).

Ponomareva, Z. Distribution of some amphipods of the Caspian relict complex under different 

temperature conditions. Izvestia Vsesojuznogo Instituta Ozernogo I Rechnogo Khozjajstva, Leningrad 

(USSR Institute of River and Lake Fisheries) 110: 36-40 (1976).

Popa, O.P., E.I. Iorgu, A.M. Krapal, B.S. Kelemen, d. Murariu, and L.O. Popa. Isolation and 

characterization of the first microsatellite markers for the endangered relict mussel Hypanis colorata

(Mollusca: Bivalvia: Cardiidae). International Journal of Molecular Science 12 (1): 456-461 (2011).

Popescu-Marinescu, V., M. Nastasescu, C. Marinescu, F. Cutas, and E. Neagu. Amphipoda (Gammaridae 

and Corophiidae) from Romanian stretch of danube before and after the construction of iron gates i 

damlake. Travaux du Muséum National d’Histoire Naturelle “Grigore Antipa” 43: 347-366 (2001).

Popov, A.I. Alien species of zooplankton in Saratov Reservoir (Russia, Volga River). УДК: 574.583 

(2011). 

Popova, O.A. The role of predacious fish in ecosystems. Gerking, S.D. (ed.). Ecology of Freshwater Fish 

Production. Blackwell, Oxford 215-249 pp. (1978).

Porak, W.F., S. Crawford, D. Renfro, R.L. Cailteux, and J. Chadwick. Study XII. Largemouth Bass 

population responses to aquatic plant management strategies. Florida Game and Fresh Water Fish 

Commission, Completion Report as required by Federal Aid in Sport Fish Restoration Wallop-Breaux 

Project F-24-R, Tallahassee, Florida. 86 pp. (1990)

Porter, M.L., K. Meland, and W. Price. Global diversity of mysids (Crustacea- Mysida) in freshwater. 

Hydrobiologia 595: 213-218 (2008).

Pothoven, S.A., I.A. Grigorovich, G.L. Fahnenstiel, and M.D. Balcer. Introduction of the Ponto-Caspian 

Bloody-Red Mysid Hemimysis anomala into the Lake Michigan basin. Journal of Great Lakes Research

(33): 285-292 (2007).
1598

Power, A., M. Mitchell, R. Walker, M. Posey, T. Alphin, and C. Belcher. Baseline Port Surveys for 

Introduced Marine Molluscan, Crustacean and Polychaete Species in the South Atlantic Bight. Final 

Completion Report: NOAA's National Sea Grant Aquatic Nuisance Species Program, Project Number 

R/HAB-15 Grant Number NA06RG0029 (2006).

Power, M., and M.J. Attrill. Temperature-dependent temporal variation in the size and growth of Thames 

estuary Smelt Osmerus eperlanus. Marine Ecology Progress Series 330: 213-222 (2007).

Pranovi, F., A. Caccin, P. Franzoi, S. Malavasi, M. Zucchetta, and P. Torricelli. Vulnerability of artisanal 

fisheries to climate change in the Venice Lagoon. Journal of Fish Biology 83 (4): 847-864 (2013).

Pritchett, J., and M. Pyron. Fish assemblages respond to habitat and hydrology in the Wabash River, 

Indiana. River Research and Applications 28:1501-1509 (2011).

Privolnev, T.I. Reaction of freshwater, anadromous, and catadromous fish to varying water salinity. 

Privolnev, T.I. (ed.). Fish physiology in acclimatization and breeding. Program for Scientific 

Translations, Jerusalem, Israel 57-84 pp. (1970).

Projecto-Garcia, J., H. Cabral, and C.D. Schubart. High regional differentiation in a North American crab 

species throughout its native range and invaded European waters: a phylogeographic analysis. Biological 

Invasions 12:253-263 (2010).

Pronin, N.M., G.W. Fleischer, D.R. Baldanova, and S.V. Pronin. Parasites of the recently established 

round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus marmoratus) (Cottidae) from 

the St. Clair River and Lake St. Clair, Michigan, USA. Folia Parasitologica 44: 1-6 (1997).

Pronin, N.M., and E.M. Bolonev. On the modern geographical range of the Amur Sleeper Perccottus 

glenii (perciformes: Odontobutidae) in the Baikal Region, and its penetration into the ecosystem of open 

Baikal. Journal of Ichthyology 46: 547-549 (2006).

Protasov, A.A., and A.A. Silaeva. Data on invasion and sympatric habitation of invasive species in the 

Dnieper basin water bodies. Russian Journal of Biological Invasions 1:114-118 (2010).

Qualls, T.M., D.M. Dolan, T. Reed, M.E. Zorn, and J. Kennedy. Analysis of the impacts of the zebra 

mussel, Dreissena polymorpha, on nutrients, water clarity, and the chlorophyll-phosphorus relationship in 

lower Green Bay. Journal of Great Lakes Research 33(3): 617-626 (2007).

Quayyum, H.A., A.U. Mallik, and P.F. Lee. Allelopathic potential of aquatic plants associated with Wild 

Rice (Zizania palustris): I. Bioassay with plant and lake sediment samples. Journal of Chemical Ecology

25 (1): 209-220 (1999).

Queensland Department of Agriculture, Fisheries and Forest. Dense waterweed (2011). 

http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-

0605030c0f01/media/Html/Egeria_densa.htm

Queensland Herbarium. Invasive naturalized plants in Southeast Queensland, ranked list. Queensland 

Environmental Protection Agency, Queensland Herbarium, Queensland, Australia (2002). 

http://www.derm.qld.gov.au/register/p00727aa.pdf
1599

Quignard, J.P. and A. Pras. Atherinidae. In Fishes of the North-eastern Atlantic and the Mediterranean.

Eds. P.J. Whitehead, M.L. Bauchot, J.C. Hureau, J. Nielsen, and E. Tortonese (p. 1207-1210). Paris: 

UNESCO (1986).

Raddum, G.G., and T.M. Johnsen. Growth and feeding of Fredericella sultana (Bryozoa) in the outlet of 

a humic acid lake. Hydrobiologia 101: 115-120 (1983).

Radke, R.J., and U. Kahl. Effects of a filter-feeding fish (Silver Carp, Hypophthalmichthys molitrix

(Val.)) on phyto- and zooplankton in a mesotrophic reservoir: results from an enclosure experiment. 

Freshwater Biology 47: 2337-2344 (2002).

Radziejewska, T., and G. Schernewski. The Szczecin (Oder-) Lagoon. Schiewer, U. (ed.). Ecology of 

Baltic Coastal Waters. Ecological Studies 197 115-129 pp. (2008).

Rae, B.B. The incidence of larvae of Porrocaecum decipiens in the flesh of cod. Journal of Marine

Research 2: 1-28 (1963).

Ragimov, D.B. On the reproduction of small species of Gobiidae from the Caspian Sea. Vopr. Ikht. 26: 

937-944 (1986).

Rahel, F.J., and J.D. Olden. Assessing the effects of climate change on aquatic invasive species. 

Conservation Biology 22 (3): 521-533 (2008).

Rajagopal, S., G. van der Velde, B. Paffen, and A. bij de Vaate. Ecology and impact of the exotic 

amphipod, Corophium curvispinum Sars, 1895 (Crustacea: Amphipoda), in the River Rhine and Meuse. 

Institute for Inland Water Management and Waste Water Treatment (RIZA). 89 pp. (1998a).

Rajagopal, S., G. van der Velde, B. Paffen, and A. bij de Vaate. Growth and production of Corophium 

curvispinum GO Sars, 1895 (Amphipoda), an invader in the lower Rhine. Crustaceans and biodiversity 

crisis: Proceedings of the Fourth International Crustacean Congress, Amsterdam, The Netherlands July 

20-24, 1998, 1: 458-472 (1998b). 

Ramey, V. Hydrilla (Hydrilla verticillata). Center for Aquatic and Invasive Plants, University of Florida, 

IFAS (2001). http://plants.ifas.ufl.edu/node/183

Randall, R. Australia weed risk assessment: Pistia stratiotes (2003). 

http://www.hear.org/pier/wra/australia/pistr-wra.htm

Rantala, M.J., J. Ilmonen, J. Koskimaki, J. Suhonen, and K. Tynkkynen. The macryophyte, Stratiotes 

aloides, protects larve of dragonfly Aeshna viridis against fish predation. Aquatic Ecology 37: 77-82 

(2004).

Rasmussen, E. Immigrants in the southern harbour of Copenhagen. Naturens Verden 1958: 3-8 (1958).

Rasmussen, J.B., D.J. Rowan, D.R.S. Lean, and J.H. Carey. 1990. Food chain structure in Ontario lakes 

determines PCB levels in Lake Trout (Salvelinus namaycush) and other pelagic fish. Canadian Journal of 

Fisheries and Aquatic Sciences 47: 2030-2038. 
1600

Rasmussen, J.L., H.A. Reiger, R.E. Sparks, and W.W. Taylor. Dividing the waters: the case for 

hydrologic separation of the North American Great Lakes and Mississippi River Basins. Journal of Great 

Lakes Research 37(3): 588-592 (2011).

Ray, W.J., and L.D. Corkum. Predation of Zebra Mussels by Round Gobies, Neogobius melanostomus.

Environmental Biology of Fishes 50 (3): 267- 273 (1997).

Reams, W.M. The occurrence and ontogeny of hydrothodes in Hygrophila polysperma T. Anders. New 

Phytologist 52: 8-13 (1953).

Reckel, F., B. Hoffmann, R. Melzer, J. Horppila, and U. Smola. Photoreceptors and cone patterns in the 

retina of the Smelt Osmerus eperlanus (L.) (Osmeridae: Teleostei). Acta Zoologica 84: 161-170 (2003).

Reed, E.B. The occurrence of Cyclops kolensis Lilljeborg (Copepoda, Cyclopoida) in North America. 

Pacific Science 22: 251-266 (1968).

Reid, D.F. and M.I. Orlova. Geological and evolutionary underpinnings for the success of Ponto-Caspian 

species invasions in the Baltic Sea and North American Great Lakes. Can. J. Fish. Aquat. Sci.59: 1144-

1158 (2002).

Reid, D.F., T. Johengen, H.J. MacIsaac, F.C. Dobbs, M. Doblin, L. Drake, G.M. Ruiz, P.T. Jenkins, S. 

Santagata, C.D.A. van Overdijk, D. Gray, S. Ellis, Y. Hong, Y. Tang, F. Thomson, S. Heinemann, and S. 

Rondon. A final report for the project "Identifying, verifying, and establishing options for best 

management practices for NOBOB vessels". National Oceanic and Atmospheric Administration, Great 

Lakes Environmental Research Laboratory, and University of Michigan Cooperative Institute for 

Limnology and Ecosystems Research, Ann Arbor (2007).

Reinhold, M., and T. Tittizer. Zur Rolle von Schiffen als Vektoren beim Faunenaustausch 

Rhein/Main/Main-Donau-Kanal/Donau. Deutsche gewässerkundliche Mitteilungen 5: 199-205 (1997).

Reinhold, M., and T. Tittizer. Verschleppung von Makrozoen durch Kühlwasserfilter eines Schiffes. 

Wasser und Boden 51: 61-66 (1999).

Reisser, C.E., and R.B. Forward. Effect of Salinity on Osmoregulation and Survival of a Rhizocephalan 

parasite, Loxothylacus panopaei, and Its Crab Host, Rhithropanopeus harrisii. Estuaries 14:102-106

(1991).

Rejmankova, E., H.M. Savage, M. Rejmanek, J.I. Arredondo-Jimenez, and D.R. Roberts. Multivariate 

analysis of relationships between habitats, environmental factors and occurrence of Anopheline mosquito 

larvae Anopheles albimanus and A. pseudopunctipennis in southern Chiapas, Mexico. The Journal of 

Applied Ecology 28:827-841 (1991).

Reshetnikova, A.N. Species diversity of aquatic animals (invertebrates, amphibians, and fishes) in ponds 

and the effect of predation by the introduced fish Rotan (Perccottus glenii). Biodiversity and Dynamics of 

Ecosystems in north Eurasia, Novosibirsk 3 (2): 279-281 (2000).

Reshetnikov, A.N. The introduced fish, Rotan (Perccottus glenii), depresses populations of aquatic 

animals (macroinvertebrates, amphibians, and a fish). Hydrobiologia 510: 83-90 (2003).
1601

Reshetnikov, A.N. The fish Perccottus glenii: History of introduction to western regions of Eurasia. 

Hydrobiologia 522: 349-350 (2004).

Reshetnikova, A.N. The current range of Amur sleeper Perccottus glenii Dybowski, 1877 

(Odontobutidae, Pisces) in Eurasia. Russian Journal of Biological Invasions 1: 119-126 (2010).

Reshetnikov, A.N. Decreased Triturus cristatus breeding site number as a consequence of Perccottus 

glenii range expansion. Frog Log 20:18 (2012)

Reshetnikov, A.N., and G.F. Ficetola. Potential range of the invasive fish Rotan (Perccottus glenii) in the 

Holarctic. Biological Invasians 13: 2967-2980 (2011).

Reshetnikov, A.N., and U.K. Schliewen. First record of the invasive alien fish Rotan Perccottus glenii 

Dybowski, 1877 (Odontobutidae) in the Upper Danube drainage (Bavaria, Germany). Journal of Applied 

Ichthyology 29: 1367-1369 (2013).

Retzer, M.E., and B. Batten. Fishes of the Chicago Region: a review of the Dennison and Illinois Natural 

History Survey collections. Transactions of the Illinois State Academy of Science 98(1-2): 63-73 (2005).

Reyjol, Y., J.P. Léna, F. Hervant, and D. Pont. Effects of temperature on biological and biochemical 

indicators of the life-history strategy of Bullhead Cottus gobio. Journal of Fish Biology 75: 1427-1445

(2009).

Rezsu, E., and A. Specziár. Ontogenetic diet profiles and size-dependent diet partitioning of Ruffe 

Gymnocephalus cernuus, Perch Perca fluviatilis and Pumpkinseed Lepomis gibbosus in Lake Balaton. 

Ecology of Freshwater Fish 15 (3): 339-349 (2006).

Ricciardi, A. Global range expansion of the Asian mussel Limnoperna fortunei (Mytilidae): another 

fouling threat to freshwater systems. Biofouling: The Journal of Bioadhesion and Biofilm Research. 13 

(2): 97-106 (1998).

Ricciardi, A. Facilitative interactions among aquatic invaders: Is an "invasional meltdown" occurring in 

the Great Lakes? Canadian Journal of Fisheries and Aquatic Sciences 58 (12): 2513-2525 (2001).

Ricciardi, A., F.G. Whoriskey, and J.B. Rasmussen. The role of the Zebra Mussel (Dreissena 

polymorpha) in structuring macroinvertebrate communities on hard substrata. Canadian Journal of 

Fisheries and Aquatic Sciences 54 (11): 2596-2608 (1997).

Ricciardi, A., and J.B. Rasmussen. Predicting the identity and impact of future biological invaders: a 

priority for aquatic resource management. Canadian Journal of Fisheries and Aquatic Sciences 55: 1759-

1765 (1998).

Ricciardi, A., H.J. MacIsaac. Recent mass invasion of North Maerican Great Lakes by Ponto-Caspian 

species. Trends in Ecology & Evolution 15 (2): 62-65 (2000).

Ricciardi, A., and H.J. MacIsaac. Evaluating the effectiveness of ballast water exchange policy in the 

Great Lakes. Ecological Applications 18: 1321-1323 (2008).

Ricciardi, A., S. Avlijas, and J. Marty. Forecasting the ecological impacts of the Hemimysis anomala

invasion in North America: Lessons from other freshwater mysid introductions. Journal of Great Lakes 

Research 38 (Supplement 2): 7-13 (2011).
1602

Richey, H.M. IV. Reproduction of the exotic estuarine Mud Crab Rhithropanopeus harrisii in Texas 

impoundments. Tarleton State University, Stephenville, Tex (2004).

Riehl, R., and H.A. Baensch. Aquarien Atlas. Vergla fur Naturund Heimteirkunde, Germany. 992 pp. 

(1991).

Rinchard, J., P. Kestement. Comparitive study of reproductive biology in single- and- multiple- spawner 

cyprinid fish. I. Morphological and histological features. Journal of Fish Biology 49 (5): 883-894 (1996).

Risch, M. Chemical and biological quality of surface water at the U.S. Army Attenbury Reserve Forces 

Training Area near Edinburgh, Indiana, September 2000 through July 2001. DIANE Publishing (2004).

Rivers, L. Water Lettuce (Pistia stratiotes). University of Florida and Sea Grant (2002).

Rivier, I. Ecology of diapausing copepodids of Cyclops kolensis Lill. in reservoirs of the Upper Volga. 

Hydrobiologia 320: 235-241 (1996).

Rivier, I.K. The predatory Cladocera (Onychopoda: Podonidae, Cercopagidae) and Leptodorida of the 

world. Backhuys Publishing, Leiden, 212 pp. (1998).

Rivier, I.K. Composition and some ecological features of winter zooplankton in deep stratified lakes. 

Russian Journal of Ecology 36 (2): 179-192 (2005).

Rixon, C.A.M., I.C. Duggan, N.M.N. Bergeron, A. Ricciardi, and H.J. MacIsaac. Invasion risks posed by 

the aquarium trade and live fish markets on the Laurentian Great Lakes. Biodiversity and Conservation 

14: 1365-1381 (2005).

Rizevsky, V., M. Pluta, A. Leschenko, and I. Ermolaeva. First record of the invasive Ponto-Caspian 

Tubenose Goby Proterorhinus marmoratus (Pallas, 1814) from the River Pripyat, Belarus. Aquatic 

Invasions 2: 275-277 (2007).

Rizevsky, V., A. Leschenko, E. Ermolaeva, and M. Pluta. First record of the Ponto-Caspian stellate 

tadpole-goby Benthophilus stellatus (Sauvage, 1874) from the Dnieper River, Belarus. BioInvasions 

Records 2(2): 159-161 (2013).

Rizzo, W.M., R.G. Boustany, and D.R. Meaux. Ecosystem changes in a subtropical Louisiana lake due to 

invasion by Hydrilla. Abstract in From Small Streams to Big Rivers, Society of Wetland Scientists 17th

Annual Meeting, June 9-14, 1996, Kansas City, MO (1996).

Roberts, D.E., A.G. Church, and S.P. Cummins. Invasion of Egeria into the Hawkesbury-Nepean River, 

Australia. Journal of Aquatic Plant Management 37: 31-34 (1999).

Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lacher, R. Lea, and W.B. Scott. World Fishes 

Important to North Americans Exclusive of Species from Continental Waters of the United States. 

American Fisheries Society Special Publication 21: 243pp. (1991).

Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott. Common 

and scientific names of fishes from the United States and Canada. 5th Edition. American Fisheries 

Society Special Publication 20. American Fisheries Society, Bethesda, MD (1991).
1603

Robinson, M. Potential invader, Eastern Indian Hygrophila: an exotic aquatic plant. Massachusetts 

Department of Conservation and Recreation Office of Water Resources, Lakes and Ponds Progra (2003). 

http://www.mass.gov/eea/docs/dcr/watersupply/lakepond/factsheet/hygrophila.pdf

Robinson, M. A guide to selected invasive non-native aquatic species in Massachusetts. Massachusetts 

Department of Conservation and Recreation, Lakes and Ponds Program. 14 pp. (2007).

Robison, H.W., and T.M. Buchanan. Fishes of Arkansas. University of Arkansas Press, Fayetteville, 

Arkansas, 536 pp. (1988).

Roche, D.G., and M.E. Rochin. Established populations of the North American Harris mud crab, 

Rhithropanopeus harrisii (Gould, 1841) (Crustacea: Brachyura: Xanthidae) in the Panama Canal. Aquatic 

Invasions 2 (3): 155-161 (2007).

Roche, D.G., M.E. Torchin, B. Leung, and S.A. Binning. Localized invasion of the North American 

Harris Mud Crab, Rhithropanopeus harrisii, in the Panama Canal: implications for eradication and 

spread. Biological Invasions 11: 983-993 (2009).

Rodgers, P.J., M.L. Reaka, and A.H. Hines. A comparative analysis of sperm storage and mating 

strategies in five species of brachyuran crabs. Marine Biology 158: 1733-1742 (2011).

Rodionova, N. Invasion of the Ponto-Caspian predatory cladoceran Cornigerius maeoticus maeoticus 

(Pengo, 1879) into the Baltic Sea. Oceanology 45 (1): 66 (2005).

Rohlwing, T., H. Palm, and H. Rosenthal. Parasitation with Pseudoterranova decipiens (Nematoda) 

influences the survival rate of the European Smelt Osmerus eperlanus retained by a screen wall of a 

nuclear power plant. Diseases of Aquatic Organisms 32: 233-236 (1998).

Rojas Molina, F. Impacts of the invading Golden Mussel Limnoperna fortunei on zooplankton: a 

mesocosm experiment. Zoological Studies 51 (6): 733 (2012).

Rojas Molina, F., J. Paggi, and M. Devercelli. Zooplanktophagy in the natural diet and selectivity of the 

invasive mollusk Limnoperna fortunei. Biological Invasions 12 (6): 1647-1659 (2010).

Rojas Molina, F., and V. Williner. First record of the non-indigenous mussel Limnoperna fortunei 

(Bivalvia, Mytilidae) as an epibiont of the crab Trichodactylus borellianus (Decapoda, Trichodactylidae). 

Crustaceana 86 (6): 682-692 (2013).

Rojas Molina, F., S. J. de Paggi, and D. Boltovskoy. Vulnerability of microcrustaceans to predation by 

the invasive filter-feeding mussel Limnoperna fortunei (Dunker). Marine and Freshwater Behaviour and 

Physiology 44 (6): 329-338 (2013).

Romanova, N.N. Survival of some Amphipoda under different salinities. Proceedings of All-Union 

Research Institute of Fisheries and Oceanography 38: 277-291 (1959).

Romanova, N. Quantitative distribution and ecology of corophiids (Crustacea, Amphipoda, Corophium). 

Byulleten Moskovsko obshchestva ispytatelei prirody. Otdel Biologicheskii 80 (3): 51-63 (1975).

Rosa, C.S., R.D. Antunes, R.A. Pitelli, and R.L.C.M. Pitelli. Comparative evaluation of water losses by 

evapotranspiration in mesocosms colonized by different aquatic weeds. Planta Daninha 27 (3): 441-445 

(2009).
1604

Rosecchi E., and A. J. Crivelli. Study of a Sand Smelt (Atherina boyeri Risso 1810) popukation 

reproducing in fresh water. Ecology of Fresh Water 1 (2): 77-85 (1992).

Rosecchi, E., A. Crivelli, and G. Catsadorakis. The establishment and impact of Pseudorasbora parva, an 

exotic fish species introduced into Lake Mikri Prespa (north-western Greece). Aquatic Conservation: 

Marine and Freshwater Ecosystems 3: 223-231 (1993).

Ross, S.T. Inland Fishes of Mississippi. University Press of Mississippi, Jackson, MS. 624 pp. (2001).

Ross, S.T., M.T. O'Connell, D.M. Patrick, C.A. Latorre, W.T. Slack, J.G. Knight, and S.D. Wilkins. 

Stream erosion and densities of Etheostoma rubrum (Percidae) and associated riffle-inhabiting fishes: 

Biotic stability in a variable habitat. Copeia 2001(4): 916-927 (2001).

Rotella, A.R., and J.O. Luken. Biomass and growth of Waterhyacinth in a tidal blackwater river, South 

Carolina. Southeastern Naturalist 11 (3): 361-374 (2012).

Ruiz, G.M., P. Fofonoff, J.T. Carlton, M.J. Wonham, and A.H. Hines. Invasion of coastal marine 

communities in North America: Apparent patterns, processes, and biases. Annual Review in Ecology and 

Systematics 2000: 481-531 (2000).

Rumbold, C.E., S.M. Obenat, and E.D. Spivak. Life history of Tanais dulongii (Tanaidacea: Tanaidae) in 

an intertidal flat in the Southwestern Atlantic. Journal of Crustacean Biology 32: 891-898 (2012).

Russell, N.R., and R.J. Wootton. Appetite and growth compensation in the European minnow, Phoxinus 

phoxinus (Cyprinidae), following short periods of food restriction. Environmental Biology of Fishes 34: 

277-285 (1992).

Russia, H.C.O. Climate monthly mean for temperatures Saint- Petersburg 1961-1990 (2013). 

http://wmc.meteoinfo.ru/climate/climtowns/1408-1282729560

Saenkova, A.K. New information on Caspian Sea fauna. Zoological Journal 35 (5): 678-679 (1956).

Šajna, N., M. Haler, S. Škornik, and M. Kaligarič. Survival and expansion of Pistia stratiotes L. in a 

thermal stream in Slovenia. Aquatic Botany 87: 75-79 (2007).

Sala, O.E., F.S. Chapin III, J.J. Armesto, E. Berlow, J. Bloomfield, R. Dirzo, E. Huber-Sanwald, L.F. 

Huenneke, R.B. Jackson, A. Kinzig, R. Leemans, D.M. Lodge, H.A. Mooney, M. Oesterheld, N. Leroy 

Poff, M.T. Sykes, B.H. Walker, M. Walker, and D.H. Wall. Global biodiversity scenarios for the year 

2100. Science 287: 1770-1774 (2000). 

Salagado, J. Stratiotes aloides. United Kingdom Natural History Museum (2013). 

http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/endangered-species/stratoidesaloides/index.html

Salgado-Maldonado, G., and R.F. Pinea-López. The Asian fish tapeworm Bothriocephalus acheilognathi: 

a potential threat to native freshwater fish species in Mexico. Biological invasions 5: 261-268 (2003).

Salemaa, H., and V. Hietalahti. Hemimysis anomala G.O. Sars (Crustacea: Mysidacea) - immigration of a 

Pontcaspian mysid into the Baltic Sea. Annales Zoologici Fennici 30: 271-276 (1993).
1605

Salo. Life history of Chum Salmon (Oncorhynchus keta). Pacific Salmon Life Histories. Groot and 

Margolis (eds.). UBC Press, 564 pp. (1991).

Samchyshyna, L.V. Ecological characteristic of calanoids (Copepoda, Calanoida) of the inland waters of 

Ukraine. Vestnik Zoologii 42 (2): e32-e37 (2008).

Sampson, S.J., J.H. Chick, and M.A. Pegg. Diet overlap among two Asian carp and three native fishes in 

backwater lakes on the Illinois and Mississippi rivers. Biological Invasions 11: 483-496 (2009).

Sanders, R.E. Day versus night electrofishing catches from near-shore waters of the Ohio and Muskingum 

Rivers. Ohio Journal of Science 92(3): 51-59 (1992).

Sanders, N.J. Population-level traits that affect, and do not affect, invasion success. Molecular Ecology

19: 1079-1081 (2010).

Sandström, A., and P. Karås. Effects of eutrophication on young-of-the-year freshwater fish communities 

in coastal area of the Baltic. Environmental Biology of Fishes 63 (1): 89-101 (2002).

Santagata, S., Z. Gasiunaite, E. Verling, J.R. Cordell, K. Eason, J.S. Cohen, K. Bacela, G. Quilez-Badia, 

T.H. Johengen, and D.F. Reid. Effect of osmotic shock as a management strategy to reduce transfers of 

nonindigenous species among low-salinity ports by ships. Aquatic Invasions 3 (1): 61-76 (2008).

Sardiña, P., E. Chaves, and M. Marchese. Benthic community responses to invasion by the golden 

mussel, Limnoperna fortunei Dunker: biotic homogenization vs environmental driving forces. Journal of 

the North American Benthological Society 30 (4): 1009-1023 (2011).

Sari, H.M., S. Balık, M. Bilecenoğlu, and G. Türe. Recent changes in the fish fauna of Lake Bafa, Aegean 

region of Turkey. Zoology in the Middle East 18: 67-76 (1999).

Sarneel, J.M. The dispersal capacity of vegetative propagules of riparian fen species. Hydrobiologia 710: 

219-225 (2013).

Sasaki, M., S. Hitotsumachi, S. Makino, and T. Terao. A comparative study of the chromosomes in the 

Chum Salmon, the Kokanee Salmon, and their hybrids. Caryologia 21 (4): 389-394 (1968).

Sasi, H., and S. Berber. Some biological characteristics of Monkey Goby in Anatolia. Asian Journal of 

Animal and Veterinary Advances 5 (3): 229-233 (2010). 

Saygi, Y., E. Gunduz, F.Y. Demirkalp, and S.S. Caglar. Seasonal patterns of the zooplankton community 

in the shallow, brackish Liman Lake in Kizilirmak Delta, Turkey. Turkish Journal of Zoology 35:783-792

(2011).

Schardt, J.D. Florida Aquatic Plant Survey Report, Report No. 942-CGA. Florida Department of 

Environmental Protection, Bureau of Aquatic Plant Management, Tallahassee, Florida. 83 pp. (1994)

Schiewer, U. (ed.). Ecology of Baltic Coastal Waters. Springer (2008).

Schleuter, D. Competition for food between Perch (Perca fluviatilis L.) and invasive Ruffe 

(Gymnocephalus cernus L.) in re-ogliotrophic Lake Constance. Cuvilier Verlag, 118 pp. (2007).
1606

Schleuter, M., A. Schleuter, S. Potel, and M. Banning. Dikerogammarus haemobaphes (Eichwald 1841) 

(Gammaridae) aus der Donau erreicht über den Main-Donau-Kanal den Main. Lauterbornia 19: 155-159 

(1994).

Schloesser, R.W., M.C. Fabrizio, R.J. Latour, G.C. Garman, B. Greenlee, M. Groves, and J. Gartland. 

Ecological role of Blue Catfish in Chesapeake Bay communities and implications for management. 

Conservation, ecology, and management of worldwide catfish populations and habitats. American 

Fisheries Society Symposium 369-382 pp. (2011).

Schmitz, D.C., and J.A. Osborne. Zooplankton densities in a Hydrilla infested lake. Hydrobiologia 111: 

127-132 (1984).

Schmitz, D.C., J.D. Schardt, A.J. Leslie, F.A. Dray Jr, J.A. Osborne, B.V. Nelson, and B.N. McKnight. 

The ecological impact and management history of three invasive alien aquatic plant species in Florida. 

Biological pollution: the control and impact of invasive exotic species. Proceedings of a symposium held 

at Indianapolis, Indiana, October 25-26, 1991 (1993). 

Schofield, P.J., J.D. Williams, L.G. Nico, P. Fuller, and M.R. Thomas. Foreign nonindigenous carps and 

minnows (Cyprinidae) in the United States - A guide to their identification, distribution and biology. 

United States Geological Survey (2005).

Schofield, P.J., L.G. Nico, P. Fuller, A. Fusaro, A. Davidson, K. Alame, M. Gappy, and W. Conard. 

Carassius carassius. United States Geological Survey (USGS) Nonindigenous Aquatic Species Database, 

Gainesville, FL, and National Oceanic and Atmospheric Administration (NOAA) Great Lakes Aquatic 

Nonindigenous Species Information System, Ann Arbor, MI (2015). 

Schöll, F., C. Becker, and T. Tittizer. Das Makrozoobenthos des schiffbaren Rheins von Basel bis 

Emmerich 1986-1995. Lauterbornia 21: 115-137 (1995).

Schöll, K., and A. Kiss. Checklist of the planktonic rotifer fauna in the active floodplain area of the 

Danube (1843-1806, 1669 and 1437-1489 rkm). Opuscula Zoologica Budapest 40 (2): 63-73 (2009).

Schönhuth, S,. and R.L. Mayden. Phylogenetic relationships in the genus Cyprinella (Actinopterygii: 

Cyprinidae) based on mitochondrial and nuclear gene sequences. Molecular Phylogenetics and Evolution

55: 77-98 (2010).

Schrank, S.J., and C.S. Guy. Age, growth, and gonadal characteristics of adult Bighead Carp, 

Hypophthalmichthys nobilis, in the lower Missouri River. Environmental Biology of Fishes 64:443-450 

(2000).

Schrank, S.J., C.S. Guy, and J.F. Fairchild. Competitive interactions between age-0 Bighead Carp and 

Paddlefish. Transactions of the American Fisheries Society 132: 1222-1228 (2003).

Schreier, T.A., V.K. Dawson, W. Larson. Effectiveness of Piscicides for controlling round gobies 

(Neogobius melanostomus). Journal of Great Lakes Research 34 (2): 253-264 (2008).

Schroeder, P.C., and C.O. Hermans. Annelida-Polychaeta. Giese, A.C., and J.S. Pearse (eds.). 

Reproductive biology of invertebrates. Academic Press, London 1-213 pp. (1975). 
1607

Schulze, T., U. Baade, H. Dorner, R. Eckmann, S.S. Haertel-Borer, F. Holker, and T. Mehner. Response 

of the residual piscivorous fish community to introduction of a new predator type in a mesotrophic lake.

Canadian Journal of Fisheries and Aquatic Science 63: 2202-2212 (2006).

D. Scipiloti. Fish community in the Stagnone di Marsala: Distribution and resource partitioning as a 

function of different habitat complexity degrees. PhD dissertation, University of Messina, Italy (1998).

Sculthorpe, C. The Biology of Aquatic Vascular Plants. Edward Arnold, London (1985).

Seeb, J.E., G.H. Thogaard, and T. Tynan. Triploid hybrids between Chum Salmon female x Chinook 

Salmon male have early sea-water tolerance. Aquaculture 117 (1-2): 37-45 (1993).

Seeley, C.M. A report on the Orfe, Leuciscus idus (Linne). Department of Fish and Game (1962).

Seely, R. Unraveling the mystery behind dying coots – an eastern European parasite nicknamed Leo is the 

cause, but biologists wonder: how did it get here? How can it be controlled? Wisconsin State Journal. 

Madison, WI. 21 November 1999. InfoTrac Newsstand (1999). 

Semenchenko, V., and V. Vezhnovetz. Two new invasive Ponto-Caspian amphipods reached the Pripyat 

River, Belarus. Aquatic Invasions 3 (4): 445-447 (2008).

Semenchenko, V. Rizevsky, S. Mastitsky, T. Laenko. Checklist of aquatic alien species established in 

large river basins of Belarus. Aquatic Invasions. 4 (2):337-347 (2008).

Semenchenko, V.P., V.K. Rizevsky, S.E. Mastitsky, V.V. Vezhnovets, M.V. Pluta, V.I. Razlutsky, and T. 

Laenko. Checklist of aquatic alien species established in large river basins of Belarus. Aquatic Invasions 4

(2): 337-347 (2009).

Seo, H., S. Kim, K. Seong, and S. Kang. Variability in scale growth rates of Chum Salmon 

(Oncorhynchus keta) in relation to climate changes in the late 1980s. Marine Ecosystem Structure and 

Dynamics 68 (2-4): 205-216 (2006). 

Sepulveda, A. Daily growth increments in the otoliths of European Smelt Osmerus eperlanus larvae. 

Marine Ecology Progress Series 108: 33-42 (1994).

Setälä, J., P. Salmi, P. Muje, and A. Käyhkö. The commercial utilization of small Perch (Perca 

fluviatilis L.) in Finnish inland fisheries. Annales Zoologici Fennici 33: 547-551 (1996).

Severinghause, L.L., and L. Chi. Prayer animal release in Taiwan. Biological Conservation 89: 301-304 

(1999).

Sezen, B. Izmir Homa Lagünü gümüs baligi (Atherina boyeri Risso, 1810) populasyonunun biyolojik 

özelliklerinin incelenmesi. MSc thesis, Izmir: Ege University, 71 pp. (2005).

Shakhmatova, R. A. and P. I. Antonov. Seasonal dynamics of biomass, density and production of 

gammarids of the Volga River. Proceedings of Gorky University. Terrestrial and aquatic ecosystems

11: 102–112 (1988).

Shanab, S.M.M., E.A. Shalaby, D.A. Lightfoot, and H.A. El-Shemy. Allelopathic effects of Water 

Hyacinth (Eichhornia crassipes). PLoS One 5 (10): e13200 (2010).
1608

Sharma, A.K. Ecophysiological studies on Water Lettuce in a polluted lake. Journal of Aquatic Plant 

Management 22: 17-21 (1984).

Sheppard, A.W., R.H. Shaw, and R. Sforza. Top 20 environmental weeds for classical biological control 

in Europe: a review of opportunities, regulations, and other barriers to adoption. Weed Research 46: 93-

117 (2006).

Sheri, A.N., and G. Power. Fecundity of Yellow Perch, Perca flavescens, Mitchell, in the Bay of Quinte, 

Lake Ontario. Canadian Journal of Zoology 47: 55-58 (1969).

Shiganova, T.A., H.J. Dumont, A.F. Sokolsky, A.M. Kamakin, D. Tinenkova and E.K. Kurasheva. 

Population dynamics of Mnemiopsis leidyi in the Caspian Sea, and effects on the Caspian ecosystem. 

Chapeter 3 http://link.springer.com/chapter/10.1007/1-4020-2152-6_3#page-1 (2004)

Shireman, J.V., and C.R. Smith. Synopsis of biological data on the Grass Carp, Ctenopharyngodon 

idella (Cuvier and Valenciennes, 1844). Center for Aquatic Plants, Institute of Food and Agricultural 

Sciences, University of Florida, Gainesville, FL (1983). 

Shiu, H., and L. Stokes. Buddhist animal release practices: historic, environmental, public health and 

economic concerns. Contemporary Buddhism: An Interdisciplinary Journal 9: 181-196 (2008).

Shokhin, I., M. Nabozhenko, S. Sarvilina, and E. Titova. The present-day condition and regularities of the 

distribution of the bottom communities in Taganrog Bay. Oceanology 46 (3): 401-410 (2006).

Simberloff, D., and M. Rejmanek. Encyclopedia of Biological Invasions. University of California Press. 

Berkeley, California. 765 pp. (2011)

Simon, T.P., J.O. Whitaker, Jr., J.S. Castrale, and S.A. Minton. Checklist of the vertebrates of Indiana. 

Proceedings of the Indiana Academy of Science 101: 95-126 (1992).

Simonović, P.D. Phylogenetic relationships of Ponto-Caspian gobies and their relationship to the 

Atlantic-Mediterranean Gobiinae. Journal of Fish Biology 54 (3): 533-555 (1999).

Simonović, P., S. Marić, and V. Nikolić. Occurrence of paddlefish Polyodon spathula (Walbaum, 1792) 

in the Serbian part of the lower River Danube. Aquatic Invasions 1 (3): 183-185 (2006).

Sinha, S., R. Saxena, and S. Singh. Fluoride removal from water by Hydrilla verticillata (l.f.) Royle and 

its toxic effects. Bulletin of Environmental Contamination and Toxicology 65: 683-690 (2000).

Sithithaworn, P., and M. Haswell-Elkins. Epidemiology of Opisthorchis viverrini. Acta Tropica 88: 187-

194 (2003).

Skora, S., and J. Erdmanski. The survival, growth and morphological features of F2 generation Crucian 

Carp hybrids reared in ponds in fish stock mixed with carp. Acta Hydrobiologia 27: 101-111 (1985).

Sladecek, V. Rotifers as indicators of water quality. Hydrobiologia 100: 169-201 (1983).

Slota, P., E. Parker, and C. Haecker. New parasite kills birds on Wisconsin Lake. United States 

Department of the Interior, United States Geological Survey, Office of Communication (1998). 
1609

Slynko, Y.V., L.G. Korneva, I.K. Rivier, V.G. Papchenkov, G.H. Scherbina, M.I. Orlova, M.I., and T.W. 

Therriault. The Caspian-Volga-Baltic invasion corridor. Invasive Aquatic Species of Europe. Springer 

Netherlands399-411 pp. (2002).

Smirnov, A.I. Pisces: Perciformes, Scorpaeniformes, Pleuronectiformes, Gobiesociformes, Lophiiformes. 

Fauna Ukraine 8(5). Naukova Dumka, Kiev, 320 pp. (1986).

Smith, P.W. The fishes of Illinois. University of Illinois Press, Urbana, IL (1979).

Smith, P.W. The Fishes of Illinois. Illinois State Natural History Survey, University of Illinois Press 

Urbana and Chicago (2002).

Smith, R.J.F., and J.D. Smith. Seasonal loss of alarm substance cells in Chrosomus neogaeus, Notropis 

venustus, and N. whipplei. Copeia 1983(3): 822-826 (1983).

Smith, P.A., R.T. Leah, and J.W. Eaton. Removal of Pikeperch (Stizostedion lucioperca) from a British 

Canal as a management technique to reduce impact on prey fish populations. Annales Botanici Fennici

33: 537-545 (1996).

Smith, P.A., R.T. Leah, and J.W. Eaton. A review of the current knowledge on the introduction, ecology 

and management of Zander, Stizostedion lucioperca, in UK. Cowx I.G. (ed.). Stocking and introduction of 

fish. Fishing New Books, Oxford 209-224 pp. (1998).

Smyly, W.J.P. The life history of the Bullhead or Miller’s thumb (Cottus gobio L.). Proceedings of the 

Zoological Society of London 128: 431-453 (1957).

Snigirov, S., O. Goncharov, and S. Sylantyev. The fish community in Zmiinyi Island waters: structure 

and determinants. Marine Biodiversity 42(2): 225-239 (2012).

Snyder, R.J., L.E. Burlakova, A.Y. Karatayev, and D.B. MacNeill. Updated Invasion Risk Assessment for 

Ponto-Caspian Fishes to the Great Lakes. Journal of Great Lakes Research 40 (2): 360-369 (2014).

Sokolov, S.G., A.N. Reshetnikov, and E.N. Protasova. A checklist of parasites in non-native populations 

of Rotan Perccottus glenii Dybowski, 1877 (Odontobutidae). Journal of Applied Ichthyology 30: 574-

596 (2014).

Solarz, W. Alien species in Poland. Institute of Nature Conservation, Polish Academy of Sciences (2005).

Son, M.O. Invasive molluscs in fresh and brackish waters of the northern Black Sea region. Odessa (UA): 

Druk. 132 pp. (2007).

Sopanen, S. The effect of temperature on the development and hatching of resting eggs of non-indigenous 

predatory cladoceran Cercopagis pengoi in the Gulf of Finland, Baltic Sea. Marine Biology 154 (1): 99-

108 (2008). 

Souchon, Y. and L. Tissot. Synthesis of thermal tolerances of the common freshwater fish species in large 

Western Europe rivers. Knowledge and Management of Aquatic Ecosystems 405: 03 (2012).
1610

South Carolina Department of Natural Resources. South Carolina Aquatic Invasive Species Management 

Plan. South Carolina Aquatic Invasive Species Task Force (2008). 

http://www.dnr.sc.gov/invasiveweeds/aisfiles/SCAISplan.pdf

Spaccesi, F.G., and A.R. Capitulo. Benthic communities on hard substrates covered by Limnoperna 

fortunei Dunker (Bivalvia, Mytilidae) at an estuarine beach (Río de la Plata, Argentina). Journal of 

Limnology 71 (1): 144-153 (2012).

Sparks, R.E. Forty years of science and management on the Upper Mississippi River: an analysis of the 

past and a view of the future. Hydrobiologia 640: 3-15 (2010).

Spataru, P., and M. Gophen. Feeding behaviour of Silver Carp Hypophthalmichthys molitrix Val. and its 

impact on the food web in Lake Kinneret, Israel. Hydrobiologia 120(1)53-61 (1985).

Spear, K. Water Lettuce: Florida villain or native? Orlando Sentinel (2014). 

http://articles.orlandosentinel.com/2014-05-24/news/os-water-lettuce-dispute-20140524_1_lettuce-plantflorida-museum

Specziár, A. Size-dependent prey selection in piscivorous Pikeperch Sander lucioperca and Volga 

Pikeperch Sander volgensis shaped by bimodal prey size distribution. Journal of Fish Biology 79: 1895-

1917 (2011).

Spencer, C.N., B.R. McClelland, and J.A. Stanford. Shrimp stocking, salmon collapse, and eagle 

displacement. BioScience 41: 14-21 (1991).

Spencer, W., and G. Bowes. Limnophila and Hygrophila: a review and physiological assessment of their 

weed potential in Florida. Journal of Aquatic Plant Management 23: 7-16 (1985).

Sprokkereef, E., M. Barben, J. Belz, A. Grasso, A. Jakob, C. Mathis, and M. Schürch. Annual Report of 

the CHR 2008. International Commission for the Hydrology of the Rhine Basin (CHR), The Netherlands. 

1-11 pp. (2008).

Sridhar, M.K.C., and B.M. Sharma. Pistia stratiotes L. in Nigerian waters. Experientia 36: 953-955

(1980).

Sridhar, M.K.C., and B.M. Sharma. Some observations on the oxygen changes in a lake covered with 

Pistia stratiotes L. Water Research 19: 935-939 (1985).

Sršen, V. Ichthyofauna of the Neretva River estuary. BSc thesis. Faculty of Science. University of Zagreb. 

50 pp. (1995).

Stakenas, S. Clupeonella cultriventris (Black Sea kilka). Invasie Species Compendium, Centre for 

Agricultural Bioscience International (2011). http://www.cabi.org/isc/datasheet/88779

Stanley, J.G. Reproduction of the Grass Carp (Ctenopharyngodon idella) outside its native range. 

Fisheries 1(3):7-10 (1976).

Starling, F.L.R.M. Control of eutrophication by Silver Carp (Hypophthalmichthys molitrix) in the tropical 

Paranoa Reservoir (Brasilia, Brazil): a mesocosm experiment. Hydrobiologia 257: 143-152 (1993).
1611

Starnes, L.B., and W.C. Starnes. Biology of the Blackside Dace Phoxinus cumberlandensis. American 

Midland Naturalist 106 (2): 360-371 (1981).

Stauffer, J. Fishes of West Virginia. Academy of Natural Sciences. 389 pp. (2007).

Stauffer, J.R., Jr., C.H. Hocutt, and D.S. Lee. The zoogeography of the freshwater fishes of the Potomac 

River basin. Flynn, K.C., and W.T. Mason (eds.). The freshwater Potomac: aquatic communites and 

environmental stresses. Interstate Commission on the Potomac River Basin 44-54 pp. (1978).

Stein, H., and O. Herl. Pseudorasbora parva eine neue Art der mitteleuropaeischen Fischfauna. 

Zeitschrift fuer die Binnenfischerei 36: 12 (1986).

Stepien, C.A., C.D. Taylor, and K.A. Dabrowska. Genetic variability and phylogeographic patterns of a 

nonindigenous species invasion: a comparison of exotic versus native Zebra and Quagga mussel 

populations. Journal of Evolutionary Biology 15: 314-328 (2002).

Stepien, C.A., and M.A. Tumeo. Invasion genetics of Ponto-Caspian gobies in the Great Lakes: a 

‘cryptic’ species, absence of founder effects, and comparative risk analysis. Biological Invasions 8: 61-78 

(2006).

Sterligova, O.D. Smelt Osmerus eperlanus (L.) and its role of Ichtyofauna of Lake Saamajarvi. Voprosy 

ikhtyologi 5: 793-800 (1979).

Sterud, E., and S.L. Poynton. Spironucleus vortens (Diplomonadida) in the Ide, Leuciscus idus (L.) 

(Cyprinidae): A warm water Hexamitid flagellate found in Northern Europe. Journal of Eukaryote 

Microbiology 49(2): 137-145 (2002).

Stern, C.V., H.F. Upton, and C. Brougher. Asian carp and the Great Lakes Region. Congressional 

Research Service (2014). https://www.fas.org/sgp/crs/misc/R41082.pdf

Stetsenko, D.A., A.A. Arzumanov, V.A. Korshun, and M.J. Gait. Peptide Conjugates of Oligonucleotides 

as Enhanced Antisense Agents. Molecular Biology 34: 852 (2000).

Stewart, T.W., J.G. Miner, and R.L. Lowe. Quantifying mechanisms for Zebra Mussel effects on benthic 

macroinvertebrates: organic matter production and shell generated habitats. Journal of North American 

Benthology Society 17: 81-94 (1998).

Stickney, R.R. Aquaculture in the United States: a historical survey. John Wiley and Sons, New York, 

NY (1996).

Stiers, I.N. Crohain, G. Josens, and L. Triest. Impact of three aquatic invasive species on native plants and 

macroinvertebrates in temperate ponds. Biological Invasions 13: 2715-2726 (2011).

Stoilovskyi and Kivganov. Information Sheet on Ramsar Wetlands: Kyliiske Mouth. [Information Sheet]. 

(1998). https://rsis.ramsar.org/RISapp/files/RISrep/UA113RIS.pdf

Stokes, K., K. O’Neill, and R. McDonald. Invasive species of Ireland. Unpublished report to Environment 

& Heritage Service and National Parks & Wildlife Service. Quercus, Queens University Belfast, Belfast 

(2006).
1612

Stone, N., C. Engle, D. Heikes, and D. Freeman. Bighead carp. Southern Regional Aquaculture Center 

(SRAC), Stoneville, Mississippi, September 2000. Southern Regional Aquaculture Center Publication 

438 (2000).

Strzałek, M., and P. Koperski. The Stratiotes aloides L. stand as a habitat in Oxbow Lake Bużysko. 

Aquatic Botany 90: 1-6 (2009).

Sublette, J.E., M.D. Hatch, and M. Sublette. The fishes of New Mexico. University of New Mexico Press, 

Albuquerque, NM (1990).

Sukhodolov, A., W. Bertoldi, C. Wolter, N. Surrian, and M. Tubino. Implications of channel process for 

juvenile fish habitats in Alpine rivers. Aquatic Sciences 71: 388 (2009).

Sukhodolov, A. N., N. A. Arnaut, L. A. Kudersky, N. S. Loboda, V. V. Bekh, B. G. Skakalsky, V. M. 

Katolikov, and M. A. Usatii. Western Steppic Rivers. Rivers of Europe 497-523 pp. (2009).

Sulgostowska, T., and L. Vojtkova. The helminth fauna of Gammarus spp. (Amphipoda) from the southeast Baltic Sea (Poland). Acta Parasitologica 37 (4): 189-193 (1992).

Summers, K. Great Lakes coastal condition. National coastal condition report. United States 

Environmental Protection Agency, Office of Research and Development/Office of Water. 156-169 pp. 

(2001). 

Surowiec, J., and A. Dobrzycka-Krahel. New data on the non-indigenous gammarids in the Vistula Delta 

and the Vistula Lagoon. Oceanologia 50 (3): 443-447 (2008).

Sutton, D.L. Life cycle and phenology of hygrophila in relation to development of management strategies. 

Stocker, R.K. (ed.). Control technologies for use against submerged aquatic weeds hydrilla and 

hygrophila. USDA-ARS No. 58-6629-4-008. Center for Aquatic Plants, University of Florida, 

Gainesville, Florida 51-68 pp. (1996).

Sutton, D.L., T.K. Van, and K.M. Portier. Growth of dioecious and monoecious hydrilla from single 

tubers. Journal of Aquatic Plant Management 30: 15-20 (1992).

Svärdson, G., O. Filipsson, M. Fürst, M. Hanson, and N.A. Nilsson. The significance of glacial relicts for 

the fish fauna of Lake Vӓttern. Information Institute of Freshwater Research Drottningholm 15: 61 pp. 

(1988).

Svetlichny, L., E. Hubareva, and A. Khanaychenko. Calanipeda aquaedulcis and Arctodiaptomus salinus

are exceptionally euryhaline osmoconformers: Evidence from mortality, oxygen consumption, and mass 

density patterns. Marine Ecology Progress Series 470: 15-U313 (2012a).

Svetlichny, L., A. Khanaychenko, E. Hubareva, and L. Aganesova. Partitioning of respiratory energy and 

environmental tolerance in the copepods Calanipeda aquaedulcis and Arctodiaptomus salinus. Estuarine 

Coastal and Shelf Science 114: 199-207 (2012b).

Svetovidov, A.N. Fishes of the Black Sea. Soviet Academy of Sciences, Moscow (1964).

Swale, E., and H. Belcher. Crassula helmsii, the Swamp Stonecrop, near Cambridge. Nature 

Cambridgeshire 25: 59-62 (1982).
1613

Swift, MC. Prey capture by the four larval instars of Chaoborus crystallinus. Limnology and 

Oceanography 37 (1): 14-24 (1992).

Sylvester, F., J. Dorado, D. Boltovskoy, A. Juarez, and D.H. Cataldo. Filtration rates of the invasive pest 

bivalve Limnoperna fortunei as a function of size and temperature. Hydrobiologia 534: 71-80 (2005).

Sylvester, F., D.H. Cataldo, C. Notaro, and D. Boltovskoy. Fluctuating salinity improves survival of the 

invasive freshwater Golden Mussel at high salinity: implications for the introduction of aquatic species 

through estuarine ports. Biological invasions 15 (6): 1355-1366 (2013).

Sytsma, M.D., J.R. Cordell, J.W. Chapman, and R.O. Draheim. Lower Columbia River Aquatic 

Nonindigenous Species Survey. 2000-2004. Final Technical Report. Prepared for the United States Coast 

Guard and United States Fish and Wildlife Service, 69 pp. (2004).

Syväranta, J., J. Cucherousset, D. Kopp, A. Crivelli, R. Cereghino, and F. Santoul. Dietary breadth and 

trophic position of introduced European Catfish Silurus glanis in the River Tarn (Garonne River basin), 

southwest France. Aquatic Biology 8 (2): 137-144 (2010).

Szczerbowski, J.A., and A.J. Szczerbowski. Carassius carassius (Linneaus, 1758). Bãnãrescu, P.M., and 

H.J. Paepke (eds.) The Freshwater Fishes of Europe, Vol. 5/III; Cyprinidae 2/III and Gasterosteidae. 

AULA-Verlag GmbH Wiebelsheim. 43-78 pp. (2001).

Szöcs, E., E. Coring, J. Bäthe, and R.B. Schäfer. Effects of anthropogenic salinization on biological traits 

and community composition of stream macroinvertebrates. Science of the Total Environment 468: 943-

949 (2014).

Tallberg, P., J. Horppila, A. Väisäne, and L. Nurminen. Seasonal succession of phytoplankton and 

zooplankton along a trophic gradient in a eutrophic lake- implications for food web management. 

Hydrobiologia 412: 81-94 (1999). 

Tang, J., S. Ye, W. Li, J. Liu and T. Zhang. Status and historical changes in the fish community in Erhai 

Lake. Chinese Journal of Oceanology and Limnology 31 (4): 712-723 (2013).

Tarasov, A.G. Macrocrustaceans (Malacostraca) in the Ural River. Hydrobiological Journal 32: 18-30 

(1996).

Targónska,, K., K. Kupren, D. Zarski, R. Krol, and D. Kucharczyk. Influence of thermal conditions on 

successful Ide (Leuciscus idus L.) artificial reproduction during the spawning season. Italian Journal of 

Animal Science 10 (2011).

Targónska, K., D. Żarski, S. Krejszeff, and D. Kucharczyk. Influence of age of wild Ide Leuciscus idus

(L.)) female on spawning effectiveness under controlled conditions. Italian Journal of Animal Science 11: 

e63 (2012).

Tarkan, A.S., Ö. Gaygusuz, H. Acipinar, Ҫ. Gürsoy, and M. Özuluğ. Length-weight relationships of 

fishes from the Marmara region (NW-Turkey). Journal of Applied Ichthyology 22(4): 271-273 (2006).

Tarkan, A.S., J. Cucherousset, G. Zieba, M.L. Godard, and G.H. Copp. Growth and reproduction of 

introduced Goldfish Carassius auratus in small ponds of southeast England with and without native 

Crucian Carp Carassius carassius. Journal of Applied Ichthyology 26(Suppl. 2): 102-108 (2010).
1614

Tarkowska-Kukuryk, M. Water soldier Stratiotes aloides L. (Hydrocharitaceae) as a substratum for 

macroinvertebrates in a shallow eutrophic lake. Polish Journal of Ecology 54 (3): 441-451 (2006).

Taylor, C.M. A large-scale comparative analysis of riffle and pool fish communities in an upland stream 

system. Environmental Biology of Fishes 58 (2000).

Taylor P., R. Harris. Osmoregulation in Corophium curvispinum (Crustacea: Amphipoda), a recent 

colonizer of freshwater I. Sodium ion regulation. Journal of Comparative Physiology B: Biochemical, 

Systemic, and Environmental Physiology 156: 323–329 (1986a).

Taylor, P., and R. Harris. Osmoregulation in Corophium curvispinum (Crustacea: Amphipoda), a recent 

coloniser of freshwater. II: Water balance and the functional anatomy of the antennary organ. Journal of 

Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 156 (3): 331-337 

(1986b).

The European Network on Invasive Alien Species (NOBANIS). Obesogammarus obesus. European 

Network on Invasive Species (2014). http://www.nobanis.org/speciesInfo.asp?taxaID=5214

Therriault, T.W., and D.E. Hay. Surf Smelt (Hypomesus pretiosus) in Burrard Inlet, British Columbia: 

evidence of recreational overharvesting. Proceedings of 2003 Georgia Basin/Puget Sound Research 

Conference. Vancouver, B.C., Canada (2003).

Thiel, R., and I.C. Potter. The ichthyofaunal composition of the Elbe estuary: An analysis in space and 

time. Marine Biology 138: 603–616 (2001).

Thompson, S. A. Araceae. Flora of North America Editorial Committee, editor. Flora of North America 

North of Mexico, Volume 22: Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and 

Zingiberidae: Araceae. Oxford University Press, New York 128-142 pp. (2000).

Thorman, S. Seasonal colonisation and effects of salinity and temperature on species richness and 

abundance of fish of some brackish and estuarine shallow waters in Sweden. Holarctic Ecology 9 (2): 

126-132 (1986).

Thorp, J.H., and A.P. Covich. Ecology and classification of North American freshwater invertebrates. 

Academic Press, New York, New York (1991).

Thorp, J.H., and A.P. Covich. Ecology and classification of North American freshwater invertebrates.

Academic Press, London, UK (2001).

Thorpe, J. Synopsis of biological data on the perch Perca fluviatilis Linnaeus, 1758 and Perca flavescens 

Mitchill, 1814. FAO Fisheries Synposis 113: 138 pp. (1977).

Thullen, J.S. Production of axillary turions by the dioecious Hydrilla verticillata. Journal of Aquatic 

Plant Management 28: 11-15 (1990).

Tittizer, T. Vorkommen und Ausbreitung aquatischer Neozoen (Makrozoobenthos) in den 

Bundeswasserstraßen. Gebhardt H., R. Kinzelbach, and S. Schmidt-Fischer (eds.). Gebietsfremde 

Tierarten. Auswirkungen auf einheimischen Arten, Lebensgemeinschaften und Biotope. 

Situationsanalyse. Ecomed Verlagsgesellschaft, Landsberg 49-86 pp. (1996).
1615

Tittizer, T., F. Schöll, and M. Dommermuth. The development of the macrozoobenthos in the river Rhine 

in Germany during the 20th century. Water Science and Technology 29 (3): 21-28 (1994).

Tittizer, T., and Banning, M. Biological assessment in the Danube catchment area: indicators of shifts in 

species composition induced by human activities. European Water Management 3 (2): 35-45 (2000).

Tittizer, T., F. Schöll, M. Banning, A. Haybach and M. Schleuter. Aquatische Neozoen im 

Makrozoobenthos der Binnenwasserstraflen Deutschlands. Lauterbornia 39: 1-72 (2000).

Tockner, K., U. Uehlinger, and C.T. Robinson. Rivers of Europe. Academic press. Amsterdam. 728 pp. 

(2009).

Todd, J.H. A survey of the trematode parasites of fishes from Lake Hertel, Mont St. Hillair, Quebec. 

M.Sc. Thesis. Department of Parasitology, McGill University (1963). 

Todd, T.N. Artificial propagation of coregonines in the management of the Laurentian Great Lakes. 

Archiv für Hydrobiologie–Beiheft Ergebnisse der Limnologie 22:31-50 (1986). 

Toft, J.D. Community effects of the non-indigenous aquatic plant Water Hyacinth (Eichhornia crassipes) 

in the Sacramento/San Joaquin Delta, California. MSc Thesis, University of Washington School of 

Fisheries (2000). 

Tollinger, M. Annunziata. Die geographische Verbreitung der Diaptomiden und anderer Süss-und 

Brackwasser-Gattungen aus der Familie der Centropagiden. Zoologische Jahrbücher, Systematik, 

Ökologie und Geographie der Tiere 30: 1-302 (1911).

Tomlinson, M.L., and M.R. Perrow. Ecology of the Bullhead Cottus gobio. Conserving Natura 2000 

Rivers Ecology Series 4. English Nature, Peterborough (2003). 

Toner, D., and C. Rougeot. Farming of Eurasian Perch. Aquaculture Explained Special Publication 24: 72 

pp. (2008).

Tops S., D.V. Baxa, T.S. McDowell, R.P. Hedrick, and B. Okamura. Evaluation of malacosporean life 

cycles through transmission studies. Diseases of Aquatic Organisms 60: 109-121 (2004).

Tops, S., W. Lockwood, and B. Okamura. Temperature-driven proliferation of Tetracapsula 

bryosalmonae in bryozoan hosts portends salmonid declines. Diseases of Aquatic Organisms 70: 227-236 

(2006).

Tops, S., H.L. Hartikainen, and B. Okamura. The effects of infection by Tetracapsula bryosalmonae

(Myxozoa) and temperature on Fredericella sultana (Bryozoa). International Journal for Parasitology

39: 1003-1010 (2009).

Torrans, L., B. Ott, and B. Bosworth. Impact of Minimum Dissolved Oxygen Concentration on Grow-Out 

Performance of Blue Catfish with Comparison to Channel Catfish. North American Journal of 

Aquaculture 74:273-282 (2012).

Trabelsi H., F. Szönyi, N. Michelangeli, and A. Cambon. Synthèse des 2-F-alkyléthylamines: 

optimisation de l'obtention des azotures de 2-F-alkyléthyle et de leur réduction en amines. Journal of 

Flourine Chemistry 6 (1): 115-117 (1994).
1616

Trautman. Steelcolor Shiner. Willoughby, H. (ed.). The Fishes of Ohio 355-357 pp. (1980).

Tucker, T. How to fish hydrilla. Bassmaster 20 (9): 30-34 (1987).

Tuckey, T. D., and M. C. Fabrizio. Estimating relative juvenile abundance of ecologically important 

finfish in the Virginia portion of Chesapeake Bay. Project# F-104-R-15. Annual report to the Virginia 

Marine Resources Commission. Virginia Institute of Marine Science, Gloucester Point, VA (2011).

Turkowski, K., D. Kucharczyk, K. Kupren, A. Hakuć-Błażowska, K. Targońska, D. Żarski, and M. 

Kwiatkowski. Economic aspects of the experimental rearing of Asp, Aspius aspius (L.), Ide, Leuciscus 

idus (L.), and Dace, Leuciscus leuciscus (L.), under controlled conditions. Archives of Polish Fisheries 67

(4): 397-411 (2008).

Turoboyski, K. Biology and ecology of the crab Rhithropanopeus harrisii ssp. tridentatus. Marine 

Biology 23: 303-313 (1973).

Tutman, P., M. Buríc, and B. Skaramuca. First substantiated record of the Black-striped Pipefish, 

Syngnathus abaster (Actinopterygii: Syngnathiformes: Syngnathidae), in the freshwaters of Bosnia and 

Herzegovina. Acta Ichthyologica et Piscatoria 42 (3): 259-262 (2012).

Tuunainen, A.L. Professional fisheries in fresh waters. Finnish fisheries in the European perspective. 

Statistics and other data on fisheries in European Union member countries and in Finland, Sweden and 

Norway. Finnish Game and Fisheries Research Institute. Official Statistics of Finland. Environment 10: 

34-36 (1994).

Ulman, E.A. Concerning the fecundity of kakhovka gobies- Monkey Goby Neogobius fluviatilis (Pallas) 

and Racer Goby Mesogobius gymnotrachelus (Kessler). Rybn. Khoz. 4: 107-108 (1967). 

United Nations Environment Programme (UNEP), Global Environmental Alert Service (GEAS). Water 

hyacinth- Can its aggressive invasion be controlled (2013)? 

http://www.unep.org/pdf/UNEP_GEAS_APRIL_2013.pdf

United States 109th Congress. 2005. Asian carp prevention and control act. 109–585, House of 

Representatives.

United States Army Corps of Engineers (USACE). Great Lakes and Mississippi River Interbasin Study: 

Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway 

System. United States Army Corps of Engineers (2012).

United States Army Corps of Engineers (USACE). Apocorophium lacustre factsheet (2013). 

http://glmris.anl.gov/documents/docs/ans/Apocorophium_lacustre.pdf

United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS). 

Species Regulated by the Title 9 CFR Parts 83.1 through 83.7.93.900 and 93.910 through 93.916 (the 

viral Hemorrhagic Septicemia (VHS) interim rule). United States Department of Agriculture (2008). 

http://www.aphis.usda.gov/animal_health/animal_dis_spec/aquaculture/downloads/vhs_regulated_spp.pd

f

United States Department of Agriculture (USDA), Animal and Plant Health Inspection Service (APHIS). 

Federal Noxious Weed List, Effective as of December 10, 2010 (2012). 

http://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/weedlist.pdf
1617

United States Department of Agriculture (USDA), National Plant Data Team (NRCS). The PLANTS 

Database. National Plant Data Team. Greensboro, North Carolina (2013). http://plants.usda.gov/java/

United States Department of Agriculture (USDA), Plant Industry Division. Ohio State-listed noxious 

weeds. The PLANTS Database (2005). http://plants.usda.gov/java/noxious?rptType=State&statefips=39

United States Environmental Protection Agency (USEPA). Supplemental report for the Sheepshead 

Minnow and inland Silverside larval survival and growth toxicity tests: Training videotape for Center for 

Environmental Research Information (1990).

United States Environmental Protection Agency (USEPA). Predicting future introductions of 

nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Washington, 

DC (2008). http://www.epa.gov/ncea.

United States Environmental Protection Agency (USEPA). Limnology Program. Great Lakes Monitoring 

(2012). http://www.epa.gov/glnpo/monitoring/limnology/index.html

United States Fish and Wildlife Service (USFWS). Yaqui fishes recovery plan. United States Department 

of the Interior, Fish and Wildlife Service, Albuquerque, NM. 48 pp. (1994).

United States Fish and Wildlife Service (USFWS). Listing Silver Carp (Hypophthalmichthys molitrix) as 

Injurious Wildlife under Lacey Act. United States Fish and Wildlife Service, Division of Environmental 

Quality, Branch of Invasive Species. Arlington, Virginia (2006).

United States Fish and Wildlife Service (USFWS) and Great Lakes Fishery Commission (GLFC). Great 

Lakes Fish Stocking database. United States Fish and Wildlife Service, Region 3 Fisheries Program, and 

Great Lakes Fishery Commission (2010). http://www.glfc.org/fishstocking/

United States Fish and Wildlife Service (USFWS). Roach (Rutilus rutilus) Ecological Risk Screening 

Summary (2012). http://www.fws.gov/injuriouswildlife/pdf_files/Rutilus_rutilus_WEB_9-18-2012.pdf

United States Fish and Wildlife Service (USFWS). Amur Sleeper (Perccottus glenii) Ecological Risk 

Screening Summary (2014a). http://www.fws.gov/injuriouswildlife/pdf_files/Perccottus_glenii_WEB_9-

15-2014.pdf

United States Fish and Wildlife Service (USFWS). Eurasian Minnow (Phoxinus phoxinus) Ecological 

Risk Screening Summary (2014b). 

http://www.fws.gov/injuriouswildlife/pdf_files/Phoxinus_phoxinus_WEB_9-15-14.pdf

United States Fish and Wildlife Service (USFWS). European Perch (Perca fluviatilis) Ecological Risk 

Screening Summary (2014c). http://www.fws.gov/injuriouswildlife/pdf_files/Perca_fluviatilis_WEB_9-

15-14.pdf

United States Fish and Wildlife Service (USFWS). Yabby (Cherax destructor) Ecological Risk Screening 

Summary (2014d). http://www.fws.gov/injuriouswildlife/pdf_files/Cherax_destructor_WEB_9-15-

2014.pdf.

United States Fish and Wildlife Service (USFWS). Zander (Sander lucioperca) Ecological Risk 

Screening Summary (2014e). 

http://www.fws.gov/injuriouswildlife/pdf_files/Sander_lucioperca_WEB_9-15-2014.pdf
1618

United States Geological Survey (USGS). Apocorphium lacustre (2013). 

http://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2315

United States Geological Survey (USGS). Nonindigenous Aquatic Species Database Gainesville, FL 

(2015). http://nas.er.usgs.gov/default.aspx

University of Florida, Institute of Food and Agricultural Sciences (UF IFAS). Parrot Feather 

(Myriophyllum aquaticum). Center for Aquatic and Invasive Plants Database (2010). 

http://plants.ifas.ufl.edu/node/276

University of Florida, Institute of Food and Agricultural Sciences (UF IFAS). Water Hyacinth 

(Eichhornia crassipes). Center for Aquatic and Invasive Plants Database (2013). 

http://plants.ifas.ufl.edu/node/141

Urawa, S., T. Azumaya, P.A. Crane, and L.W. Seeb. Origin and distribution of Chum Salmon in the 

Bering Sea during the Early Fall of 2002: Estimates by Allozyme Analysis. (NPAFC Doc. 794) National 

Salmon Resources Center, Toyohira-ku, Sapporo 062-0922, Japan. (2004).

Uspenskaja, V.D. Feeding of Crucian Carp in lakes of river Kljzma. Trudy Vsesojuzn Gidrobiol. Obshtsch

5: 347-364 (1953).

Utzinger, J., C. Roth, and A. Peter. Effects of environmental parameters on the distributin of Bullhead 

Cottus gobio with particular consideration of the effects of obstructions. Journal of Applied Ecology 35: 

882-892 (1998).

Uusitalo, L., J. Horppila, P. Eloranta, A. Liljendahl-Nurminen, T. Malinen, M. Salonen, and M. Vinni. 

Leptodora kindti and flexible foraging behavior of fish- factors behind the delayed biomass peak of 

cladocerans in Lake Hiidenvesi. International Review of Hydrobiology 88 (1): 34-48 (2003).

Uye, S. Development of neritic copepods Acartia clausi and A. steuri: 1. Some environmental factors 

affecting egg development and the nature of resting eggs. Bulletin of the Plankton Society of Japan 27: 1-

9 (1980).

Uye, S., K. Yoshiya, K. Ueda, and S. Kasahara. The effect of organic sea-bottom pollution on 

survivability of resting eggs of neritic calanoids. Crustaceana Supplement 7: 390-403 (1984).

Valdenberg, Arie, A. Milstein and S. Harpaz. Effects of Timing of Common Carp Larvae Stocking on 

Zooplankton Succession in Earthen Nursery Ponds: A Microcosm Simulation. Journal of the World 

Aquaculture Society 37 (4): 378-387 (2006).

van den Brink F.W.B, G. van der Velde, and A. bij de Vaate. 1991. Amphipod invasion on the Rhine. 

Nature 352: 576.

van den Brink, F.W.B., G. van der Velde, and A. bij de Vaate. Ecological aspects, explosive range 

extension and impact of a mass invader, Corophium curvispinum Sars 1895 (Crustacea: Amphipoda), in 

the lower Rhine (The Netherlands). Oecologia 93 (2): 224-232 (1993).

van Densen, W.L.T. Piscivory and the development of bimodality in the size distribution of 0+ pikeperch 

(Stizstodeion lucioperca L.). Zeitschift fur Angewandte Ichthyologie 3: 119-131 (1985).
1619

Van der Velde, G., B.G.P. Paffen, F.W.B. van den Brink, A. bij de Vaate, and H.A. Jenner. Decline of 

zebra mussel populations in the Rhine. Competition between two mass invaders (Dreissena polymorpha 

and Corophium curvispinum). The Science of Nature 81 (1): 32-34 (1994).

Van der Velde G, S. Rajagopal, F.W.B. Van den Brink, B. Kelleher, B.G.P. Paffen, A.J. Kempers, and A. 

bij de Vaate. Ecological impact of an exotic invasion in the River Rhine. Nienhuis PH, RSEW Leuven, 

Ragas AMJ (eds), New concepts for sustainable management of river basins. Backhuys Publishing, 

Leiden, 159–169 pp. (1998).

van der Velde, G., S. Rajagopal, B. Kelleher, I. Musko, B. Vaate, and F. Schram. Ecological impact of 

crustacean invaders: General considerations and examples from the Rhine River. The Biodiversity Crisis 

and Crustacea: 3-33 (2000).

van der Velde, G., R.S.E.W. Leuven, D. Platvoet, K. Bacela, M.A.J. Huijbregts, H.W.M. Hendriks, and 

D. Kruijt. Environmental and morphological factors influencing predatory behaviour by invasive nonindigenous gammaridean species. Biological Invasions 11 (9): 2043-2054 (2009).

Van Dijk, G. Vallisneria and its interactions with other species. Aquatics 7 (3): 6-10 (1985).

van Dijk, G.M., and B. van Zanten. Seasonal changes in zooplankton abundance in the lower Rhine 

during 1987-1991. Hydrobiologia 304: 29-38 (1995).

Van Dijk, G.M., D.D. Thayer, and W.T. Haller. Growth of Hygrophila and Hydrilla in flowing water. 

Journal of Aquatic Plant Management 24: 85-87 (1986).

van Haaren, T., and J. Soors. Sinelobus stanfordi (Richardson, 1901): A new crustacean invader in 

Europe. Aquatic Invasions 4 (2009).

van Kessel, N., M. Dorenbosch, M.R.M. De Boer, R.S.E.W. Leuven, and G. Van der Velde. Competition 

for shelter between four invasive gobiids and two native benthic fish species. Current Zoology 57 (6): 

844-851 (2011).

van Overdijk, C.D.A., I.A. Grigorovich, T. Mabee, W.J. Ray, J.J.H. Ciborowski, and H.I. MacIsaac. 

Microhabitat selection by the invasive amphipod Echinogammarus ischnus and native Gammarus 

fasciatus in laboratory experiments and in Lake Erie. Freshwater Biology 48: 567-578 (2003).

van Riel, M.C., G. van der Velde, and A. bij de Vaate. To conquer and persist: colonization and 

population development of the Ponto-Caspian amphipods Dikerogammarus villosus and Chelicorophium 

curvispinum on bare stone substrate in the main channel of the River Rhine. Archiv für Hydrobiologie

166: 23-39 (2006).

Van, T.K., and K.K. Steward. Longevity of monoecious hydrilla propagules. Journal of Aquatic Plant 

Management 28: 74-76 (1990).

Van, T.K., W.T. Haller, and G. Bowes. Comparison of the photosynthetic characteristics of three 

submersed aquatic plants. Plant Physiology 58: 761-768 (1976).

Vander Zanden, M.J., and J.B. Rasmussen. A trophic position model of pelagic food webs: impacts on 

contaminant bioaccumulation in Lake Trout. Ecological Monographs 68: 451-477 (1996).
1620

Vander Zanden, M.J., G.J.A. Hansen, S.N. Higgins, and M.S. Kornis. A pound of prevention, plus a 

pound of cure: early detection and eradication of invasive species in the Laurentian Great Lakes. Journal 

of Great Lakes 36: 199-205 (2010).

Vandiver, V.V. Hygrophila. Aquatics 2: 4-11 (1980).

Vassilev, M.V., T.A. Trichkova, D. Ureche, I. Stoica, K. Battes, and M.T. Zivkov. Distribution of gobiid 

species (Gobiidae, Pisces) in the Yantra River (Danube basin, Bulgaria). In Proceedings of the 

Anniversary Scientific Conference of Ecology 1: 163-172 (2008).

Venema, P. Fast spread of Water Lettuce Pistia stratiotes L around Meppel. Gorteria 27: 133-135 (2001).

Verreycken, H. Risk analysis of the Amur Sleeper Perccottus glenii, risk analysis report of non-native 

organisms in Belgium. Rapporten van het Instituut voor Natuur- en Bosonderzoek 2013 

(INBO.R.2013.40). Instituut voor Natuur- en Bosonderzoek, Brussel, 29 pp. (2013).

Victorian Department of Industries. Impact Assessment - Dense waterweed (Egeria densa) in Victoria 

(2013). http://vro.dpi.vic.gov.au/dpi/vro/vrosite.nsf/pages/impact_dense_waterweed

Viitasalo, M., I. Vuorinen, and S. Saesmaa. Mesozoo-plankton dynamics in the northern Baltic Sea: 

Implications of variations in hydrography and climate. Journal of Plankton Research 17: 1857-1878 

(1995).

Vila-Gispert, A., C. Alcaraz, and E. Garcia-Berthou. Life-history traits of invasive fish in small 

Mediterranean streams. Biological Invasions 7: 107-116 (2005). 

Vilizzi, L., and G.H. Copp. Application of FISK, an Invasiveness Screening Tool for non-native 

freshwater fishes, in the Murray-Darling Basin (Southeastern Australia). Risk Analysis 33(8): 1432-1440 

(2012).

Vinogradov, V.K., and Z.K. Zolotova. The influence of the Grass Carp on aquatic ecosystems. 

Hydrobiological Journal 10(2): 72-78 (1974).

Vinyoles, D., J.I Robalo, A. de Sostoa, A. Almodóvar, B. Elvira, G.G. Nicola, C. Fernández-Degado, C.S. 

Santos, I. Doadrio, F. Sardá-Palomera, and V.C. Almada. Spread of the alien bleak Alburnus 

alburnus (Linnaeus, 1758) (Actinopterygii, Cyprinidae) in the Iberian Peninsula: the role of reservoirs. 

Graellsia 63(1): 101-110 (2007).

Voipio, A. The Baltic Sea. Elsevier Oceanography Series, Netherlands (1981).

Vollestad, L.A. Resource partitioning of Roach Rutilus rutilus and Bleak Alburnus alburnus in two 

eutrophic lakes in Southeast Norway. Holarctic Ecology 8: 88-92 (1985).

Volta, P., and N. Jepsen. The recent invasion of Rutilus rutilus (L.) (Pisces: Cyprinidae) in a large southalpine lake: Lake Maggiore. Journal of Limnology 67 (2): 163-170 (2008).

Vorobiev, V.P. The benthos of the Azov Sea. Krimizdat Press, Simpheropol (1949). 

Wærvågen, S.B., N.A. Rukke, and D.O. Hessen. Calcium content of crustacean zooplankton and its 

potential role in species distribution. Freshwater Biology 47: 1866-1878 (2002).
1621

Wager, R. Galaxiella munda. The IUCN Red List of Threatened Species (1996). 

http://www.iucnredlist.org/details/summary/8821/0

Wager, R., and P.D. Jackson. The action plan for Australian freshwater fishes. Australian Nature 

Conservative Agency, Canberra (1993).

Wahli, T., R. Knuesel, D. Bernet, H. Segner, D. Pugovkin, P. Burkhardt- Holm, M. Escher, and H. 

Schmidt-Posthaus. Proliferative kidney disease in Switzerland: current state of knowledge. Journal of 

Fish Diseases 25: 491-500 (2002).

Wallace, R.E. Rotifers: exquisite metazoans. Integrative and Comparative Biology 42: 660-667 (2002).

Walseng, B., D.O. Hessen, G. Halvorsen, and A.K. Schartau. Major contribution from littoral crustaceans 

to zooplankton species richness in lakes. Limnology Oceanography 51 (6): 2600-2606 (2006).

Washington State Department of Ecology. Non-native invasive freshwater plants: Parrotfeather 

(Myriophyllum aquaticum) (2011). http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua003.html

Washington Department of Fish & Wildlife (WDFW). Fishing & Shellfishing (2012). 

http://wdfw.wa.gov/fishing/salmon/chum/pugetsound/fishery.html

Washington State Department of Ecology. Non-Native, Invasive, Freshwater Plants – Egeria densa

(2013). http://www.ecy.wa.gov/programs/wq/plants/weeds/aqua002.html

Water Environmental Services Incorporated. Silver Lake aquatic plant survey. Water Environmental 

Services Incorporated, Third year progress report, Seattle (1994).

Watson, W. Amphibians and Crassula helmsii. Froglog 31: 2 (1999).

Wawrzyniak-Wydrowska, B., and P. Gruszka. Population dynamics of alien gammarid species in the 

River Odra estuary. Hydrobiologia 539 (1): 13-25 (2005). 

Weatherley, N.S. The diet and growth of 0-group Dace, Leuciscus leuciscus (L.), and Roach, Rutilus 

rutilus (L.), in a lowland river. Journal of Fish Biology 30: 237-247 (1987).

Welcomme, R.L. International introductions of inland aquatic species. FAO Fisheries Technical Paper 

294. Food and Agriculture Organization of the United Nations (FAO), Rome, Italy. 318 pp. (1988).

Wersal, R.M., and J.D. Madsen. Influences of water column nutrient loading on growth characteristics of 

the invasive aquatic macrophyte Myriophyllum aquaticum (Vell.) Verdc. Hydrobiologia 665: 93-105 

(2011). 

Wesenberg-Lund, C. Plankton investigations of Danish Lakes. General part. Danish Freshwater Biology 

Laboratory, No. 5. Nordisk Vorlag, Copenhagen, Denmark (1908).

Wheeler, A.C. The fishes of the British Isles and North-West Europe. Macmillan and Co., London, United 

Kingdom, 613 pp. (1969).

Wheeler, A. Hybrids of bleak, Alburnus alburnus, and chub, Leuciscus cephalus in English rivers. 

Journal of Fish Biology 13(4): 467-473 (1978).
1622

Wheeler, A. Status of the Crucian Carp, Carassius carassius (L.), in the UK. Fisheries Management and 

Ecology 7(4): 315-322 (2000).

Whitehead, P.J.P. FAO Fisheries Synopsis 125(7): 303pp. (1985).

Whitehead, P.J.P., M.L. Bauchot, J.C. Hureau, J. Nielsen, and T.E. Fishes of North-eastern Atlantic and 

the Mediterranean. United Nations Educational, Scientific and Cultural Organization, Paris, France

(1986). 

Wickham, S.A. Trophic relations between cyclopoid copepods and ciliated protists: complex interactions 

link the microbial and classic food webs. Limnology and Oceanography 40 (6): 1173-1181 (1995).

Wiesner, C. 2005. New records of non-indigenous gobies (Neogobius spp.) in the Austrian Danube. 

Journal of Applied Ichthyology 21: 324- 327 (2005). 

Wijnhoven, S., M.C. van Riel, and G. van der Velde. Exotic and indigenous freshwater gammarid 

species: physiological tolerance to water temperature in relation to ionic content of the water. Aquatic 

Ecology 37: 151-158 (2003).

Wilkinson, D.R., and J.W. Jones. The fecundity of Dace, Leuciscus leuciscus (L.) in Emral Brook, 

Clwyd, North Wales. Freshwater Biology 7 (2): 135-145 (1977).

Willemsen, J. Fishery-aspects of eutrophication. Hydrobiological Bulletin 14 (1-2): 12-21 (1980).

Williams, A. Shrimps, lobsters, and crabs of the Atlantic coast of the eastern United States, Maine to 

Florida. Smithsonian Institution Press, Washington, DC (1984).

Willink, P. Asian Carp in Chicago FAQs. https://sites.google.com/a/fieldmuseum.org/pwillink/asian-carpin-chicago-faqs (2009).

Willoughby, H. Freshwater fish culture in the United States (1965).

Wilkinson, D.R., and J.W. Jones. The fecundity of Dace, Leuciscus leuciscus (L.) in Emral Brook, 

Clwyd, North Wales. Freshwater Biology 7 (2): 135-145 (1977).

Wilson, J. Preliminary investigation of Chum Salmon spawning in Kluane Lake. The Yukon River Panel 

Restoration & Enhancement Fund CRE-57-02. Kluane First Nation, Burwash Landing, Yukon (2006). 

http://yukonriverpanel.com/salmon/wp-content/uploads/2011/02/cre-57-

02_investigations_chum_kluane_lake_final_report.pdf

Winfield, I.J. The influence of simulated aquatic macrophytes on the zooplankton consumption rate of 

juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis. Journal of 

Fish Biology 29 (Suppl. A): 37-48 (1986).

Winfield, I.J., D.K. Winfield, and C.M. Tobin. Interactions between the Roach, Rutilus rutilus, and 

waterfowl populations of Lough Neagh, Northern Island. Environmental Biology of Fishes 33 (1-2): 201-

214 (1992).
1623

Winfield, I.J., C.E. Adams, and J.M. Fletcher. Recent introductions of the Ruffe (Gymnocephalus 

cernuus) to three United Kingdom lakes containing Coregonus species. Annales zoologici fennici 33: 

459-466 (1996).

Winfield, I.J., J.M. Fletcher, and J. Ben James. The Arctic Charr (Salvelinus alpinus) populations of 

Windermere, UK: population trends associated with eutrophication, climate change, and increased 

abundance of Roach (Rutilus rutilus). Environmental Biology of Fishes 83: 23-35 (2008).

Winfield, I.J., J.M. Fletcher, and J.B. James. Invasive fish species in the largest lakes of Scotland, 

Norhtern Ireland, Wales and England: the collective UK experience. Hydrobiologia 660: 93-103 (2011).

Winton, J., G. Kurath, and W. Batts. Detection of Viral Hemorrhagic Septicemia Virus. United States 

Department of the Interior, United States Geological Survey (USGS) Report 2007-3055. 4 pp. (2007).

Wisconsin Department of Natural Resources. (WIDNR). Have you seen this plant? Hydrilla (Hydrilla 

verticillata). DNR PUB WT-884 (2009). http://dnr.wi.gov/lakes/cbcw/publications/WT-884.pdf

Wisconsin Department of Natural Resources (WIDNR). Aquatic Invasive Species Literature Review 

(2011). http://dnr.wi.gov/invasives/classification/pdfs/Myriophyllum%20aquaticum.pdf

Wisconsin Department of Natural Resources (WIDNR). Brazilian waterweed (Egeria densa) (2012). 

http://dnr.wi.gov/topic/Invasives/fact/BrazilianWaterweed.html

Wisconsin Department of Natural Resources. Water Hyacinth. Aquatic Invasive Species Literature 

Review (2013). http://dnr.wi.gov/topic/Invasives/documents/classification/Eichhornia%20crassipes.pdf

Withnall, F. Biology of Yabbies (Cherax destructor). Aquaculture Notes. State of Victoria, Department 

of Natural Resources and Environment. 4 pp. (2000).

Witkowski, A. NOBANIS – Invasive Alien Species Fact Sheet – Pseudorasbora parva. Online Database 

of the European Network on Invasive Alien Species – NOBANIS (2011). www.nobanis.org

Witkowski, A., and J. Grabowska. The non-indigenous freshwater fishes of Poland: threats to the native 

ichthyofauna and consequences for the fishery: a review. Acta Ichthyologica et Piscatoria 42(2): 77-87 

(2012).

Witt, J.D.S., P.D., Hebert, and W.B. Morton. Echinogammarus ischnus: another crustacean invader in the 

Laurentian Great Lakes basin. Canadian Journal of Fisheries and Aquatic Sciences 54: 264-268 (1997).

Wittmann, K.J. Zur Einwanderung potamophiler Malacostraca in die obere Donau: Limnomysis benedeni

(Mysidacea), Corophium curvispinum (Amphipoda) und Atyaephyra desmaresti (Decapoda). 

Lauterbornia 20: 77-85 (1995).

Wittmann, K.J. Crustacea: Mysidacea: Mysidae, Decapoda: Atyidae. Essl, F., and W. Rabitsch (eds.). 

Neobiota in Osterreich. Federal Environment Agency-Austria, Wien, Austria 269-272 pp. (2002). 

Wittmann, K.J. Continued massive invasion of Mysidae in the Rhine and Danube river systems, with first 

records of the order Mysidacea (Crustacea: Malacostraca: Peracarida) for Switzerland. Revue suisse de 

Zoologie 114 (1): 65-86 (2007).
1624

Wittmann, K.J. Invasive species compendium: Limnomysis benedeni (2009). 

http://www.cabi.org/isc/DatasheetDetailsReports.aspx?&iSectionId=110*0/141*0/23*0/122*0/103*0/135

*0/128*0/24*0/250*0/299*0/12*0/290*0/1*0/259*0/339*0/258*0/25*0/292*0/293*0/8*0/211*0/41*0/2

96*0/308*0/15*0/306*0/9*0/117*0/27*0/321*0&iDatasheetID=108853&sSystem=Product&iPageID=48

1&iCompendiumId=5. 

Wittmann, K.J., and A. Ariani. Limnomysis benedeni: Mysidacé Ponto-Caspien nouveau pour les eaux 

douces de France (Crustacea, Mysidacea). Vie et Milieu 50 (2): 117-122 (2000).

Wittmann, K.J., J. Theiss, and M. Banning. Die Drift von Mysidaceen und Dekapoden und ihre 

Bedeutung für die Ausbreitung von Neozoen im Main-Donau-System. Lauterbornia 35: 53-66 (1999).

Wolf, B., E. Kiel, A. Hagge, H.-J. Krieg, and C.K. Feld. Using the salinity preferences of benthic 

macroinvertebrates to classify running waters in brackish marshes in Germany. Ecological Indicators 9: 

837-847 (2009).

Wolff, W.J. Non-indigenous marine and estuarine species in the Netherlands. Zoologische Mededelingen 

Leiden 79: 1-116 (2005).

Wolnicki, J., and M. Kolejko. Present state of the occurrence of mud minnow in the Polesie Lubelskie and 

the species protection program in this region of the country. Lublin, Poland. Uniwersytet Przyrodniczy w 

Lublinie, Instytut Rybactwa Sródladowego w Olsztynie, 88 pp. (2008).

Wolska, M., and W.G. Piasecki. Seasonality of zooplankton changes phenomena observed in the 

estuarine part of the Oder River. Limnological Review 7 (2): 117-121 (2006).

Wolter, C., and A. Vilcinskas. Fish fauna of the Berlinean waters- their vulnerability and protection. 

Limnologica 26: 207-213 (1996).

Wolter, C., and A. Bischoff. Seasonal changes of fish diversity in the main channel of the large lowland 

River Oder. Regulated Rivers: Research and Management 17: 595-608 (2001).

Wolter, C., and J. Freyhof. Diel distribution patterns of fishes in a temperate large lowland river. Journal 

of Fish Biology 64: 632-642 (2004).

Wonham, M.J., S.A. Bailey, H.J. MacIsaac, and M.A. Lewis. Modeling the invasion risk of diapausing 

organisms transported in ballast sediments. Canadian Journal of Fisheries and Aquatic Sciences 62: 

2386-2398 (2005). 

Wood, T.S. Freshwater bryozoans: a zoogeographical reassessment. Wyse-Jackson, P., C.J. Buttler, and 

M.E. Spencer-Jones (eds.). Bryozoan studies 2001. Swets and Zeitlinger, Lisse 339-345 pp. (2002). 

Wood, T.S. The pipeline menace of freshwater bryozoans. Denesia 16: 203-208 (2005a).

Wood, T.S. Study methods for freshwater bryozoans. Denisia 16: 103-110 (2005b).

Wood, T.S., and B.T. Backus. Differentiation of North American and European forms of Fredericella 

sultana (Blumenbach) (Ectoprocta: Phylactolaemata). Hydrobiologia 237: 185-193 (1992).
1625

Wood, T.S., and B. Okamura. A new key to the freshwater bryozoans of Britain, Ireland and Continental 

Europe, with notes on their ecology. Freshwater Biological Association Scientific Publication Number 63. 

Freshwater Biological Association. Cumbria 113 pp. (2005).

Woodward, S.L., and J.A. Quinn. Encyclopedia of invasive species: from Africanized honey bees to zebra 

mussels, Volume 1. ABC-CLIO, LLC. Santa Barbara, CA (2011).

Wooldridge, T.H. Distribution, population dynamics, and estimates of production for the estuarine mysid, 

Rhopalopthalmus terranatalis. Estuarine, Coastal and Shelf Science 23 (2): 205-223 (1986).

World Health Organization 2013. About guinea-worm disease: Dracunculus medinensis (2013). 

http://www.who.int/dracunculiasis/disease/en/

Wrona, F.J., T.D. Prowse, and J.D. Reist. Chapter 8.5.3: Climate change effects on arctic freshwater fish 

populations. in Saundry, P. (ed.). Arctic Climate Impact Assessment. Arctic Climate Impact Assessment 

and International Arctic Science Committee (2010).

Wurdak, E.S., J.J. Gilbert, and R. Jagels. Fine structure of the resting eggs of the rotifers Brachionus 

calyciflorus and Asplanchna sieboldi. Transactions of the American Microscopical Society 97 (1): 49-72 

(1978).

Wurtz, C.B., and S.S. Roback. The invertebrate fauna of some Gulf Coast rivers. Proceedings of the 

National Academy of Sciences of Philadelphia 107: 167-206 (1955).

Xie, S., Y. Cui, T. Zhang, and Z. Li. Seasonal patterns in feeding ecology of three small fishes in the 

Biandantang Lake, China. Journal of Fish Biology 57: 867-880 (2000).

Xie, P., and Y. Chen. Invasive carp in China’s Plateau lakes. Science 224: 999-1000 (2001).

Xie, L. P. Xie, K. Ozawa, T. Honma, A. Yokoyama, H.D. Park. Dynamics of microcystins-LR and -RR 

in the phytoplanktivorous Silver Carp in a sub-chronic toxicity experiment. Environmental Pollution 127: 

431-439 (2004). 

Xie, D., D. Yu, L. Yu, and C. Liu. Asexual propagations of introduced exotic macrophytes Elodea 

nuttallii, Myriophyllum aquaticum, and M. propinquum are improved by nutrient-rich sediments in China. 

Hydrobiologia 655: 37-47 (2010).

Xu, M.J., Q. Liu, A.J. Nisbet, X.Q. Cai, C. Yan, R.Q. Lin, Z.G. Yuan, H.Q. Song, X.H. He, and X.Q. 

Zhu. Identification and characterization of microRNAs in Chlornorchis sinesis of human health 

significance. BMC Genomics 11: 521 (2010).

Yablonskaya, E.A., T.A. Kortunova, and G.B. Gavrilov. Long-term changes in the Aral Sea benthos. 

Proc. VNIRO 80 (3): 147-158 (in Russian) (1973).

Yakovlev, V., and A. Yakovleva. Polychaete Hypania invalida (Polychaeta: Ampharetidae) in the 

Kuybyshev Reservoir: Distribution and size and weight parameters. Russian Journal of Biological 

Invasions 1 (2): 145-151 (2010).

Yalҫin-Özdilek, S., S.G. Kirankaya, and F.G. Ekmekci. Feeding ecology of the Topmouth Gudgeon 

Pseudorasbora parva (Temminck and Schlegel, 1846) in the Gelingülü Reservoir, Turkey. Turkish 

Journal of Fisheries and Aquatic Sciences 13: 87-94 (2013).
1626

Yan, X., L. Zhenyu, W.P. Gregg, and L. Dianmo. Invasive species in China: an overview. Biodiversity 

and Conservation 10: 1317-1341 (2001).

Yang, J. Invasive alien and native fishes in Yunnan- studies on the influence and degree as well as 

relative questions. Wang, S., B. Xie, and Y. Xie (eds.). Protecting Biodiversity of China II. Scientific 

Press of Environmental of China, Beijing, China. 129-138 pp. (1996).

Yang, P., G. Jin, Y. Liu, J. Li., Z. Hu. Early development of Amur Sleeper (Perccottus glenii, Dybowski, 

1877): a remarkable invasive species in Eurasia. Iranian Journal of Fisheries Sciences 11(3): 590-601 

(2012).

Yarrow, M., V.H. Marin, M. Finlayson, A. Tironi. L.E. Delgado, and F. Fischer. The ecology of Egeria 

densa Planchon (Liliopsida: Alismatales): A wetland ecosystem engineer? Revista Chilena de Historia 

Natural 82: 299-313 (2009).

Yashanin, I.I. Changes in the numbers of Starry Goby based on observations of the feeding of the Volga 

Zander in the Central Stretch of the Kuibyshev Reservoir. Changes in fish biology under conditions of a 

regulated discharge of the Volga River (Ul’yanov. GPI, Ul’yanovsk) 71-74 pp. (1982).

Yashouv, A. Interaction between the Common Carp (Cyprinus carpio) and Silver Carp 

(Hypophthalmichthys molitrix) in fish ponds. Bamidgeh 12: 85-92 (1971).

Yoder, C.T. 1948 minnow propagation experiments. Michigan Fish Division. Institute for Fisheries 

Research, Division of Fisheries, Michigan Dept. of Conservation, Lansing, Michigan. 8 pp. (1954).

Yoder, C.T., and M.F. Division. Minnow propagation experiments for 1947. Institute for Fisheries 

Research, Division of Fisheries, Michigan Dept. of Conservation, Lansing, Michigan. 23pp. (1950)

Yousefian, M., and H. Mosavi. Spawning of South Caspian Kutum (Rutilus frisii kutum) in most 

migratory river of South Caspian Sea. Asian Journal of Animal and Veterinary Advances: 1-6 (2008).

Ysebaert, T., L.D. Neve, and P. Meire. The subtidal macrobenthos in the mesohaline part of the Schelde 

Estuary (Belgium): influenced by man? Journal of the Marine Biological Association of the United 

Kingdom 80: 587-597 (2000).

Yu, J.R., M. Seo, Y.W. Kim, M.H. Oh, and W.M. Sohn. A human case of gastric infection by larva 

Pseudoterrnova decipiens. Korean Journal of Parasitology 39 (2): 193-196 (2001).

Yunzhi, Y.A.N. Variations in reproductive strategies between one invasive population and two native 

populations of Pseudorasbora parva. Current Zoology 55 (1): 56 (2009).

Záhorská, E., and V. Kováč. Reproductive parameters of invasive Topmouth Gudgeon Pseudorasbora 

parva (Temminck and Schlegel, 1846) from Slovakia. Journal of Applied Ichthyology 25 (4): 466-469 

(2009).

Zaiko, A., R. Paskauskas, and A. Krevs. Biogeochemical alteration of benthic environment by Zebra 

Mussel Dreissena polymorpha (Pallas). Oceanologia 52 (4): 649-667 (2010).

Zaiko, A., M. Lehtiniemi, A. Narščius, and S. Olenin. Assessment of bioinvasion impacts on a regional 

scale: a comparative approach. Biological Invasions 13: 1739-1765 (2011).
1627

Zaitsev, Y., and B. Öztürk. Exotic species in the Aegean, Marmara, Black, Azov and Caspian Seas. 

Turkish Marine Research Foundation. Istanbul, Turkey. 265 pp. (2001).

Zelenin, A.M., and M.Z. Vladimirov. New data on the distribution and biology of the goby Knipowitchia 

logicaudata (Kessler) in the Danube basin USSR. Izv. Akad. Nauk. Mod. SSR. (Ser. Biol. Khim. Nauk) 5: 

44-46 (1975).

Zenkevich, L.A. Biology of the Seas of USSR. Academy Science Publishers. Moscow, Russia. 739 pp. 

(1963).

Zettler, M.L. Crustaceologische Neuigkeiten aus Mecklenburg-Vorpommern. Archiv der Freunde der 

Naturgeschichte in Mecklenburg 41: 15-36 (2002).

Žganec, K., S. Gottstein, and S. Hudina. Ponto-Caspian amphipods in Croatian large rivers. Aquatic 

Invasions 4: 327-335 (2009).

Zhadin, V.I., and S.V. Gerd. Fauna and Flora of the Rivers Lakes and Reservoirs of the U.S.S.R. 

Originally published in Moskow, 1961 by Gosudarstvennoe Uchebno-Pedagogicheskoe Izdatel'stvo 

Zhao, W., and D. Shuang-Lin. The contribution of size-fractionated plankton biomass and primary 

production of phytoplankton in saline-alkaline ponds. Hydrobiologia 492: 181-190 (2002).

Zhao, Z.G., S.L. Dong, F. Wang, X.L. Tian, and Q.F. Gao. Respiratory response of Grass Carp 

(Ctenopharyngodon idellus) to temperature changes. Aquaculture 322: 128-133 (2011).

Zhou, P., N. Chen, R.L. Zhang, R.Q. Lin, and X.Q. Zhu. Food-borne parasitic zoonoses in China: 

perspective for control. Trends in Parasitology 24: 190-196 (2008).

Zhukov, P.I. Fish in Belarus. Nauka i tehnika. Minsk, Belarus (1965). 

Zhuravel, P.A. O vselenii v vodohranilishcha i drugie vodoemi Krivorozcskogo bassejna kormovih dlja 

rib rakoobraznih mizid. Zoologiceskij Zhurnal 35 (8): 1131-1138 (1956).

Zhuravel, P.A. On the range extension of some Estuarine-Caspian invertebrates. Gidrobiologicheskii 

Zhurnal 5: 1152-1162 (1969).

Zhuravel, P.A. On the further spread and acclimatization of Monodacna colorata Eichw., and Monodacna 

pontica Eichw. in inland waters. Gidrobiologicheskii Zhurnal 11(3): 78-79 (1975).

Zinevici, V., M. Moldoveanu, and L. Florescu. Podonevadne trigona ovum (Zernov, 1901) (Cladocera), 

an immigrant subspecies with Caspian origin, newly penetrated in Romanian waters. Romanian Journal 

of Biology 56 (1): 3-15 (2011).

Zonn, I.S., M. Glantz, A.N. Kosarev, and A.G. Kostianoy. The Aral Sea Encyclopedia. Springer-Verlag 

Berlin Heidellberg, 298 pp. (2009).

Zorić, K., D. Jakovčev-Todorović, V. Đikanović, B. Vasiljević, J. Tomović, A. Atanacković, V. Simić, 

and M. Paunović. Distribution of the Ponto-Caspian polychaeta Hypania invalida (Grube, 1860) in inland 

waters of Serbia. Aquatic Invasions 6 (1): 33-38 (2011).