NOAA Technical Memorandum GLERL-161

AN IMPACT ASSESSMENT OF GREAT LAKES AQUATIC 

NONINDIGENOUS SPECIES

Rochelle Sturtevant1, Julie Larson2, Lauren Berent2, Mary McCarthy2, 

Alex Bogdanoff2, Abigail Fusaro3, and Edward Rutherford4

UNITED STATES

DEPARTMENT OF COMMERCE

Penny Pritzker

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Kathy Sullivan

Under Secretary for Oceans & Atmosphere

NOAA Administrator

NAT OI NAL OCEANIC AND ATMOSPHERIC ADMINISTRAT OI N

U.S.DEPARTMENT OF COMMERCE

1

NOAA, Sea Grant, Ann Arbor, MI 48108

2

Cooperative Institute for Limnology and Ecosystems Research, Ann Arbor, MI 48108

3

Wayne State University, Detroit, MI 48202

4

NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI 48108

July 2014
NOTICE

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

1722.

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.

NOAA’s Mission – To understand and predict changes in Earth’s environment and conserve and 

manage coastal and marine resources to meet our nation’s economic, social, and environmental 

needs 

NOAA’s Mission Goals:

• Protect, restore and manage the use of coastal and ocean resources through an ecosystem 

approach to management

• Understand climate variability and change to enhance society’s ability to plan and respond

• Serve society’s needs for weather and water information

• Support the Nation’s commerce with information for safe, efficient, and environmentally 

sound transportation

• Provide critical support for NOAA’s Mission 
i

TABLE OF CONTENTS

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

1.1 Project Background ............................................................................................................................1

1.2 Review of Impact Assessments..........................................................................................................2

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

2.1 Overview of Organism Impact Assessment Structure ........................................................................3

2.2 Criteria Assessed ................................................................................................................................3

2.2.1 Environmental Impact .................................................................................................................4

2.2.2 Socio-economic Impact ...............................................................................................................4

2.2.3 Beneficial Effect ..........................................................................................................................4

2.3 Scoring ...............................................................................................................................................4

3. RESULTS ............................................................................................................................................5

3.1 Fishes..................................................................................................................................................6

3.2 Annelids .............................................................................................................................................7

3.3 Arthropods (Non-crustacean) .............................................................................................................8

3.4 Bryozoans...........................................................................................................................................8

3.5 Coelenterates......................................................................................................................................8

3.6 Crustaceans.........................................................................................................................................9

3.7 Mollusks...........................................................................................................................................10

3.8 Plants................................................................................................................................................11

3.9 Algae ................................................................................................................................................13

3.10 Amoebae.....................................................................................................................................15

3.11 Parasites & Diseases.......................................................................................................................15

4. DISCUSSION ....................................................................................................................................16

5. ACKNOWLEDGEMENTS ...............................................................................................................19

6. REFERENCES...................................................................................................................................20

APPENDIX A. ORGANISM IMPACT ASSESSMENTS.........................................................................23

A.1 Fishes...............................................................................................................................................23

Scientific Name: Alosa aestivalis...................................................................................................23

Scientific Name: Alosa pseudoharengus........................................................................................28

Scientific Name: Apeltes quadracus...............................................................................................34

Scientific Name: Carassius auratus...............................................................................................39

Scientific Name: Cyprinus carpio ..................................................................................................44

Scientific Name: Enneacanthus gloriosus......................................................................................50

Scientific Name: Esox niger...........................................................................................................55

Scientific Name: Gambusia affinis.................................................................................................60

Scientific Name: Gymnocephalus cernua ......................................................................................65

Scientific Name: Lepisosteus platostomus .....................................................................................70

Scientific Name: Lepomis humilis..................................................................................................75

Scientific Name: Lepomis microlophus..........................................................................................80
ii

Scientific Name: Misgurnus anguillicaudatus ...............................................................................85

Scientific Name: Morone americana..............................................................................................90

Scientific Name: Neogobius melanostomus ...................................................................................96

Scientific Name: Notropis buchanani ..........................................................................................102

Scientific Name: Noturus insignis................................................................................................107

Scientific Name: Oncorhynchus gorbuscha .................................................................................112

Scientific Name: Oncorhynchus kisutch.......................................................................................117

Scientific Name: Oncorhynchus mykiss .......................................................................................123

Scientific Name: Oncorhynchus nerka.........................................................................................129

Scientific Name: Oncorhynchus tshawytscha...............................................................................134

Scientific Name: Osmerus mordax...............................................................................................140

Scientific Name: Petromyzon marinus.........................................................................................146

Scientific Name: Phenacobius mirabilis......................................................................................152

Scientific Name: Proterorhinus semilunaris................................................................................157

Scientific Name: Salmo trutta ......................................................................................................162

Scientific Name: Scardinius erythrophthalmus............................................................................168

A.2 Annelids ........................................................................................................................................173

Scientific Name: Branchiura sowerbyi ........................................................................................173

Scientific Name: Gianius aquaedulcis .........................................................................................178

Scientific Name: Potamothrix bedoti ...........................................................................................183

Scientific Name: Potamothrix moldaviensis ................................................................................188

Scientific Name: Potamothrix vejdovskyi.....................................................................................193

Scientific Name: Ripistes parasita ...............................................................................................198

A.3 Arthropods (Non-crustacean) ........................................................................................................203

Scientific Name: Acentria ephemerella........................................................................................203

Scientific Name: Tanysphyrus lemnae .........................................................................................208

A.4 Bryozoans......................................................................................................................................213

Scientific Name: Lophopodella carteri ........................................................................................213

A.5 Coelenterates .................................................................................................................................218

Scientific Name: Cordylophora caspia ........................................................................................218

Scientific Name: Craspedacusta sowerbyi...................................................................................223

A.6 Crustaceans....................................................................................................................................228

Scientific Name: Argulus japonicus.............................................................................................228

Scientific Name: Bythotrephes longimanus..................................................................................233

Scientific Name: Cercopagis pengoi............................................................................................239

Scientific Name: Cyclops strenuus...............................................................................................245

Scientific Name: Daphnia galeata galeata ..................................................................................250

Scientific Name: Daphnia lumholtzi ............................................................................................255

Scientific Name: Echinogammarus ischnus.................................................................................261

Scientific Name: Eubosmina coregoni .........................................................................................267

Scientific Name: Eubosmina maritima.........................................................................................272

Scientific Name: Eurytemora affinis............................................................................................277

Scientific Name: Gammarus tigrinus...........................................................................................282

Scientific Name: Hemimysis anomala..........................................................................................287

Scientific Name: Heteropsyllus nr. nunni.....................................................................................293

Scientific Name: Megacyclops viridis..........................................................................................298

Scientific Name: Neoergasilus japonicus.....................................................................................303
iii

Scientific Name: Nitokra hibernica..............................................................................................308

Scientific Name: Nitokra incerta..................................................................................................313

Scientific Name: Salmincola lotae ...............................................................................................318

Scientific Name: Schizopera borutzkyi.........................................................................................323

Scientific Name: Skistodiaptomus pallidus ..................................................................................328

A.7 Mollusks........................................................................................................................................333

Scientific Name: Bithynia tentaculata..........................................................................................333

Scientific Name: Cipangopaludina chinensis malleata................................................................339

Scientific Name: Cipangopaludina japonica ...............................................................................345

Scientific Name: Corbicula fluminea ...........................................................................................350

Scientific Name: Dreissena bugensis...........................................................................................356

Scientific Name: Dreissena polymorpha......................................................................................363

Scientific Name: Elimia virginica ................................................................................................370

Scientific Name: Gillia altilis.......................................................................................................375

Scientific Name: Lasmigona subviridis........................................................................................380

Scientific Name: Pisidium amnicum ............................................................................................385

Scientific Name: Pisidium henslowanum .....................................................................................390

Scientific Name: Pisidium moitessierianum.................................................................................395

Scientific Name: Pisidium supinum .............................................................................................400

Scientific Name: Potamopyrgus antipodarum .............................................................................405

Scientific Name: Radix auricularia..............................................................................................411

Scientific Name: Sphaerium corneum..........................................................................................416

Scientific Name: Valvata piscinalis .............................................................................................421

Scientific Name: Viviparus georgianus........................................................................................426

A.8 Plants.............................................................................................................................................431

Scientific Name: Agrostis gigantea..............................................................................................431

Scientific Name: Alnus glutinosa ................................................................................................434

Scientific Name: Alopecurus geniculatus L.................................................................................440

Scientific Name: Butomus umbellatus..........................................................................................445

Scientific Name: Cabomba caroliniana Gray ..............................................................................451

Scientific Name: Carex acutiformis ............................................................................................457

Scientific Name: Carex disticha Huds. .......................................................................................462

Scientific Name: Chenopodium glaucum ....................................................................................467

Scientific Name: Cirsium palustre (L.) Coss. ex Scop................................................................472

Scientific Name: Conium maculatum L. ......................................................................................477

Scientific Name: Echinochloa crus-galli......................................................................................483

Scientific Name: Epilobium hirsutum L. .....................................................................................489

Scientific Name: Rhamnus frangula (Frangula alnus) ...............................................................495

Scientific Name: Glyceria maxima..............................................................................................501

Scientific Name: Hydrocharis morsus-ranae L............................................................................507

Scientific Name: Impatiens glandulifera Royle ...........................................................................512

Scientific Name: Iris pseudacorus ...............................................................................................518

Scientific Name: Juncus compressus Jacq. ..................................................................................524

Scientific Name: Juncus gerardii Loisel. .....................................................................................529

Scientific Name: Juncus inflexius L. ............................................................................................535

Scientific Name: Lupinus polyphyllus..........................................................................................540

Scientific Name: Lycopus asper..................................................................................................545
iv

Scientific Name: Lycopus europaeus ..........................................................................................550

Scientific Name: Lysimachia nummularia L................................................................................555

Scientific Name: Lysimachia vulgaris L. .....................................................................................560

Scientific Name: Lythrum salicaria ............................................................................................565

Scientific Name: Marsilea quadrifolia L. ....................................................................................570

Scientific Name: Mentha aquatica L............................................................................................575

Scientific Name: Mentha gracilis.................................................................................................580

Scientific Name: Mentha spicata .................................................................................................585

Scientific Name: Myosotis scorpiodes..........................................................................................591

Scientific Name: Myosoton aquaticum.........................................................................................596

Scientific Name: Myriophyllum spicatum L. ................................................................................601

Scientific Name: Najas marina L.................................................................................................607

Scientific Name: Najas minor All. ...............................................................................................612

Scientific Name: Nasturtium officinale W.T. Aiton .....................................................................617

Scientific Name: Nymphoides peltata (S.G. Gmel.) Kuntze.........................................................623

Scientific Name: Pluchea odorata var. odorata (L.) Cass. ..........................................................628

Scientific Name: Pluchea odorata var. succulent (Fernald) Cronquist ........................................633

Scientific Name: Poa trivialis ......................................................................................................638

Scientific Name: Polygonum persicaria.......................................................................................643

Scientific Name: Potamogeton crispus L. ....................................................................................648

Scientific Name: Puccinellia distans............................................................................................654

Scientific Name: Rorippa sylvestris .............................................................................................659

Scientific Name: Rumex longifolius .............................................................................................664

Scientific Name: Salix alba ..........................................................................................................674

Scientific Name: Salix fragilis......................................................................................................679

Scientific Name: Salix purpurea ..................................................................................................684

Scientific Name: Solanum dulcamara L......................................................................................689

Scientific Name: Solidago sempervirens......................................................................................695

Scientific Name: Sparganium glomeratum ..................................................................................700

Scientific Name: Trapa natans L. ................................................................................................705

Scientific Name: Typha angustifolia L.........................................................................................711

Scientific Name: Veronica beccabunga .......................................................................................718

A.9 Algae .............................................................................................................................................723

Scientific Name: Actinocyclus normanii fo. subsalsa...................................................................723

Scientific Name: Bangia atropurpurea ........................................................................................728

Scientific Name: Chaetoceros muelleri var. subsalsum...............................................................733

Scientific Name: Chroodactylon ornatum (ramosum) .................................................................738

Scientific Name: Conticribra (Thalassiosira) guillardii ..............................................................743

Scientific Name: Cyclotella atomus .............................................................................................748

Scientific Name: Cyclotella cryptica............................................................................................753

Scientific Name: Cylindrospermopsis raciborskii........................................................................758

Scientific Name: Diatoma ehrenbergii.........................................................................................764

Scientific Name: Discostella pseudostelligera .............................................................................769

Scientific Name: Discotella woltereckii .......................................................................................774

Scientific Name: Hymenomonas roseola......................................................................................779

Scientific Name: Nitellopsis obtusa .............................................................................................784

Scientific Name: Pleurosira laevis...............................................................................................790
v

Scientific Name: Skeletonema potamos.......................................................................................795

Scientific Name: Skeletonema subsalsum ....................................................................................800

Scientific Name: Sphacelaria fluviatilis......................................................................................805

Scientific Name: Sphacelaria lacustris........................................................................................810

Scientific Name: Stephanodiscus binderanus...............................................................................815

Scientific Name: Stephanodiscus subtilis.....................................................................................820

Scientific Name: Thalassiosira baltica ........................................................................................825

Scientific Name: Thalassiosira lacustris......................................................................................830

Scientific Name: Thalassiosira pseudonana ................................................................................835

Scientific Name: Thalassiosira weissflogii ..................................................................................840

Scientific Name: Ulva flexuosa subsp. flexuosa and flexuosa subsp. paradoxa...........................845

Scientific Name: Ulva intestinalis................................................................................................850

Scientific Name: Ulva prolifera ...................................................................................................855

A.10 Amoebae......................................................................................................................................860

Scientific Name: Psammonobiotus communis..............................................................................860

Scientific Name: Psammonobiotus dziwnowi...............................................................................865

Scientific Name: Psammonobiotus linearis..................................................................................870

A.11 Parasites & Diseases....................................................................................................................875

Scientific Name: Acineta nitocrae................................................................................................875

Scientific Name: Aeromonas salmonicida....................................................................................880

Scientific Name: Bothriocephalus acheilognathi.........................................................................886

Scientific Name: Dactylogyrus amphibothrium ...........................................................................891

Scientific Name: Dactylogyrus hemiamphibothrium....................................................................896

Scientific Name: Dugesia polychroa............................................................................................901

Scientific Name: Glugea hertwigi ................................................................................................906

Scientific Name: Heterosporis sp.................................................................................................912

Scientific Name: Ichthyocotylurus pileatus..................................................................................917

Scientific Name: Myxobolus cerebralis........................................................................................922

Scientific Name: Neascus brevicaudatus .....................................................................................928

Scientific Name: Viral hemorrhagic septocemia Virus (Family Novirhabdoviridae, Order 

Mononegavirales) Genotype IV sublineage b ..............................................................................933

Scientific Name: Piscirickettsia cf. salmonis ...............................................................................939

Scientific Name: Ranavirus sp. ....................................................................................................944

Scientific Name: Renibacterium salmoninarum...........................................................................950

Scientific Name: Rhabdovirus carpio ..........................................................................................956

Scientific Name: Scolex pleuronectis...........................................................................................961

Scientific Name: Sphaeromyxa sevastopoli..................................................................................966

Scientific Name: Timoniella sp. ...................................................................................................971

Scientific Name: Trypanosoma acerinae .....................................................................................976

APPENDIX B: OIA REFERENCES.........................................................................................................981
1

AN IMPACT ASSESSMENT OF GREAT LAKES AQUATIC NONINDIGENOUS SPECIES

Rochelle Sturtevant, Julie Larson, Lauren Berent, Mary McCarthy, Alex Bogdanoff, 

Abigail Fusaro, and Ed Rutherford

1. INTRODUCTION

1.1 Project Background

The Great Lakes are host to thousands of native fishes, invertebrates, plants, and other species 

that not only provide recreational and economic value to the region, but also hold an important 

ecological value. However, with over 180 documented aquatic nonindigenous species1 and an 

invasion rate estimated at 1.3-1.8 species·year-1, the Great Lakes basin is considered one of the 

most heavily invaded aquatic systems in the world (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). Much of the 

recently funded research on aquatic nonindigenous species (ANS) has focused on fish and 

dreissenid mussels, but for most ANS in the Great Lakes, research has been limited and the 

extent of impact has not yet been assessed or estimated (Steinberg et al. 2007). While the 

consequences stemming from the introduction of nonindigenous species can be complex, 

understanding these impacts will foster more efficient conservation, management, and restoration 

efforts in the Great Lakes (Byers et al. 2002).

This purpose of this study is to provide a baseline assessment of realized, potential, and unknown 

impacts for established nonindigenous species in the Great Lakes. An organism impact 

assessment (OIA) tool was developed in order to analyze the extent of each species’ impact in a 

standardized manner. Following a thorough literature review, the OIA was used to rank the 

environmental impact, socio-economic impact, and beneficial effect of each species as high, 

moderate, low, or unknown. Importantly, this ranking system provides a method of identifying 

and comparing impacts across taxa and type of impact.

This effort is part of a larger project funded by the Great Lakes Restoration Initiative that will 

eventually also assess the potential impact of species predicted as likely to invade the Great 

Lakes as well as management options for established and potential invasives. The final products 

																																																												 1 These	nonindigenous	aquatic	species	have	populations	established	in	the	Great	Lakes	basin	below	the	ordinary	

high	water	mark,	including	connecting	channels,	wetlands,	and	waters	ordinarily	attached	to	the	Lakes	(see	

definitions	and	criteria	for	listing	in	the	Great	Lakes	Aquatic	Nonindigenous	Species	Information	System	at	

http://www.glerl.noaa.gov/res/Programs/glansis/glansis.html).
2

of the project will include both qualitative (high, moderate, low) rankings of impact for each 

species as well as an updated review of the available impact-related research. This information is 

being made available to scientists, managers, and the public through the Great Lakes Aquatic 

Nonindigenous Species Information System (GLANSIS), an online database containing 

information on the identification, distribution, ecology, and impact of all established ANS in the 

Great Lakes.

1.2 Review of Impact Assessments

With respect to nonindigenous species, risk assessments of potential invaders have been more 

commonly conducted than have impact assessments; however, similar methodology can be 

applied to both forms of assessment. Parker (1999) suggests that the development of both risk 

and impact assessments is based on three primary steps: (1) identify the metrics by which 

impacts or risks will be measured, (2) develop a system to sum or quantify these metrics into a 

final measure or score, and (3) use public values to determine the weight that various risks or 

impacts should hold during assessment. Most assessment tools developed for nonindigenous 

species rely upon these principles; some depend on primarily quantitative systems, while others 

are primarily qualitative in nature (Dahlstrom et al. 2011, Leung and Dudgeon 2008).

A common component of quantitative assessments is the use of numerical values and 

calculations to produce a final quantitative sum of risk or impact. Certain additive probabilities 

or currencies are often designated as proxies of risk or impact in mathematical models or other 

forms of analysis (e.g., Kolar and Lodge 2001, Leung et al. 2002). Benefit-cost analyses 

typically measure impact according to an estimate of financial cost (e.g., Pimentel 2005), while 

other assessments may depend on quantities such as invader abundance or range size as addends 

or factors of an impact score (Parker 1999). Additionally, some of these quantities, including 

change in species richness values or change in densities of native biomass, incorporate specific 

impacts into assessments (Thiele et al. 2010). While the use of numerical proxies of impact—

which are inherently measureable or calculable—suggests higher levels of objectivity and 

consistency in the assessment process, quantitative assessments may fail to account for all types 

of impacts. Moreover, they may depend on models, calculation methods, or proxies that do not 

accurately reflect impact and are often difficult to complete when available data is limited 

(Leung and Dudgeon 2008, Thiele et al. 2010). The latter is a particular issue for many of the 

over 180 ANS in the Great Lakes basin.

In contrast, managers often prioritize funding and management efforts for nonindigenous species 

by collecting information, evaluating socio-economic and environmental concerns, and 

determining relative levels of impact with the assistance of expert opinion (e.g., Mills et al. 

1993). Many impact and risk assessment systems are similarly qualitative in nature, using a 

combination of the available literature and expert judgment to estimate the extent of impact. 

While quantitative values (e.g., monetary cost or species abundance) are often taken into 

account, they act as a guide in impact assessment rather than being used to calculate an impact 

score directly. For instance, many risk and impact assessments apply information to an 

independently-derived scoring system, which may provide either numerical or categorical scores 

for each type of impact depending on its extent, and can be designed to calculate an overall rank 
3

(e.g., Copp et al. 2005, EPPO 1997, Nentwig et al. 2010, Pheloung et al. 1999, Risk Assessment 

and Management Committee 1996). While such systems may be more capable of including a 

wider variety of impacts and can function in the absence of the data on which quantitative 

systems rely, qualitative assessment systems have received criticism for being too subjective, 

implementing inaccurate scoring systems, and lacking transparency, consistency, and 

repeatability (Holt 2006, Leung and Dudgeon 2008, Parker 1999).

This project seeks to identify and compare the realized impacts of all ANS in the Great Lakes 

basin. Given the large scale of this effort, the wide variability in taxa and available information, 

and the desire to account for as many impacts as possible, a primarily qualitative approach was 

chosen. Like many risk and impact assessments, it depends on a customized scoring system that 

can account for qualitative information across taxa.

2. METHODS

2.1 Overview of Organism Impact Assessment Structure

A species-specific impact assessment tool was developed for Great Lakes nonindigenous species

as a questionnaire with three main categories of impact: environmental, socio-economic, and 

beneficial. The impact categories and criteria to be considered in each (see section 2.2) were

based on a literature review of the potential impacts of aquatic nonindigenous species as well as 

on previously implemented impact assessment systems. Three categories were chosen in order to 

incorporate both impacts perceived as adverse (i.e. environmental and socio-economic) and 

serviceable (i.e. beneficial), as both types of impacts often have important influence in an area 

(Gonzlan et al. 2010, Park 2004). Analysis of socio-economic impacts independent of 

environmental impacts allowed those consequences with direct implications for human values to 

be evaluated and ranked separately from general environmental impacts. The impact assessment 

was largely designed to reflect realized impact in the Great Lakes region; however, the 

assessment did take significant impacts of invasion outside of the Great Lakes into account (see 

section 2.3).

For each impact category, established species were assessed according to six criteria. Each 

criterion was expressed as a question followed by four possible responses. Each response 

described a different extent of the impact and was associated with a corresponding score (see 

section 2.3). Descriptions and benchmarks of impact extent were intended to be as objective as 

possible, avoiding the use of value-laden ranking terms (i.e. high, moderate, low). Scores for 

each criterion were summed, and a scoring table was established for conversion of the final score 

into an overall impact rank.

A panel of experts on aquatic nonindigenous species in the Great Lakes basin (See 5 

Acknowledgements) provided external review of the impact assessment tool and the assessment 

results throughout the development and implementation process.

2.2 Criteria Assessed
4

The criteria included in each impact category were developed with several considerations in 

mind. A significant goal was to incorporate criteria in each impact category that covered the full 

range of potential impacts in aquatic systems. However, another strong consideration was the 

need to implement criteria applicable to all nonindigenous taxa. By standardizing the assessment 

process across taxa, the resulting ranks for all 180+ Great Lakes invaders can be directly 

compared. 

2.2.1 Environmental Impact

Criteria in this category include those impacts that affect biotic and/or abiotic components of the 

ecosystem relative to pre-invasion conditions. ANS can affect native species on multiple scales, 

including the individual, the population, and the community level. Some of these impacts are due 

to direct interactions between native and nonindigenous species, such as predation or parasitism. 

However, indirect effects through alterations of the physical environment or the trophic web can 

also be numerous. Environmental impacts were consolidated into six main criteria: facilitation of 

parasitism, viral/bacterial infections, or toxicity; competition; food-web effects; genetic effects; 

degradation of water quality; and degradation of physical habitat.

2.2.2 Socio-economic Impact

Criteria in this category include those impacts that directly affect societal or individual values

relative to pre-invasion conditions. The natural resources of the Great Lakes are used by citizens 

in many ways, so the potential for socio-economic impacts following an invasion is significant. 

Thus, while some of the included potential impacts apply to invasions universally, many have a 

unique influence in the Great Lakes. The socio-economic impacts were consolidated into six 

main criteria: human health effects, infrastructural damage, degradation of water quality (related 

to human use), harm to economic sectors, harm to recreational potential, and diminishment of 

aesthetic quality.

2.2.3 Beneficial Effect

In order for this OIA tool to be accurate in its assessment and most useful for managers, both the 

adverse and beneficial effects must be accounted for (Risk Assessment and Management 

Committee 1996). Criteria in this category include those impacts perceived as advantageous or 

serviceable to either the ecosystem or human values. While some ANS in the Great Lakes are 

actively controlled because of their adverse impacts (e.g., sea lamprey, Petromyzon marinus) 

(Jones 2007), other ANS have resulted in, or been purposefully introduced for, some benefit to 

humans. Beneficial effects were consolidated into six main criteria: use as a biocontrol agent, 

commercial value, recreational value, medicinal/scientific value, improvement to water quality, 

and other ecological services.

2.3 Scoring

Six criteria for each impact category were presented in question format with four possible 

responses. Three of these responses were scored as ‘0’, ‘1’, or ‘6’ depending on the extent of 
5

impact; in general, these reflected little to no significance, moderate significance, and high 

significance, respectively. The fourth possible selection allowed an impact to be assessed as 

‘unknown’ if available information was insufficient for proper assessment. Only realized impacts 

in the Great Lakes warranted a high impact ranking for any given criterion. However, in many 

cases, a record of invasion describing significant impacts elsewhere (i.e. high potential impact) 

was considered sufficient evidence to warrant a moderate impact ranking for a given criterion. 

These particular cases were noted in the assessment.

Detailed guidelines were established to ensure consistency, transparency, and reproducibility

across all investigators involved in the assessments for cases requiring the use of best judgement. 

Of particular note, if the potential for particular direct human impact was neither noted in the 

literature, in popular media, nor could be inferred from a significant environmental impact, 

socio-economic and beneficial criteria were assessed as insignificant rather than unknown. This 

reflects a perception that impacts significant to society are unlikely to go without mention in the 

literature. In contrast, the environmental impact assessment was completed with a much heavier 

use of the precautionary principle, recognizing that any established nonindigenous organism will 

interact with the existing ecosystem in some manner. Thus, a lack of research was not assumed 

to infer a lack of impact. 

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 highimpact species overall in that category. In contrast, moderately significant impacts in all six 

criteria were required to assess a species as high-impact. A species could only be ranked as a 

low-impact species for a given category if it lacked impacts of high significance and 

demonstrated a limited number of moderately significant and unknown impacts for the six 

criteria. The full interpretation of these scores is given in Table 1. The range of scores for each 

category was 0-36, while ‘unknown’ scores in each sub-assessment ranged from 0-6.

Table 1 Interpretive scoring table for a given category of impact. Each category contained six questions that could 

receive a score of '0', '1', '6' or 'U' (unknown) corresponding to the extent of that particular impact. The qualitative 

statements describe the intended interpretation of each rank.

Scoring Qualitative Statement Score # Unknowns Species Impact

>5 Any High Species X has a high impact in the Great Lakes.

2-5 Any Moderate Species X has a moderate impact in the Great Lakes.

0 0-1

Low There is little or no evidence to support that Species X

1 0 has significant impacts in the Great Lakes.

0 ≥2

Unknown Current research on the impact of Species X in the Great 

1 ≥1 Lakes is inadequate to support proper assessment.

3. RESULTS

Organism impact assessment scores for established aquatic nonindigenous species in the Great 
6

Lakes basin are given in Tables 2-11, organized by taxonomic group. Taxonomic groups 

included fishes (n=28), annelids (n=6), arthropods (non-crustacean) (n=2), bryozoans (n=1), 

coelenterates (n=2), crustaceans (n=20), mollusks (n=18), plants (n=55), algae (n=27), testate 

amoebae (n=3), and parasites/diseases (n=20). For each species, the numeric score, number of 

unknowns, and overall rank of impact for each impact category are given.

3.1 Fishes

Table 2 Organism impact assessment scores for established fishes in the Great Lakes basin.

Scientific	Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Alosa aestivalis Blueback herring Clupeidae Unknown Low Low

0 3 0 0 0 1

Alosa pseudoharengus Alewife Clupeidae High High High

18 2 14 0 7 1

Apeltes quadracus Fourspine 

stickleback Gasterosteidae Unknown Low Low

0 4 0 0 0 1

Carassius auratus Goldfish Cyprinidae Unknown Low Unknown

1 3 0 1 0 2

Cyprinus carpio Common carp Cyprinidae High Unknown High

12 2 1 2 8 0

Enneacanthus gloriosus Bluespotted 

sunfish Centrarchidae Unknown Low Unknown

0 6 0 1 0 2

Esox niger Chain pickerel Esocidae Unknown Low Low

1 4 0 1 1 0

Gambusia affinis Western 

mosquitofish Poeciliidae Unknown Low Unknown

0 4 0 1 1 2

Gymnocephalus cernua Ruffe Percidae

Moderate Unknown Low

2 2 0 3 0 0

Lepisosteus platostomus Shortnose gar Lepisosteidae Unknown Low Low

0 4 0 1 0 0

Lepomis humilis Orangespotted 

sunfish Centrarchidae Unknown Low Unknown

0 5 0 1 0 2

Lepomis microlophus Redear sunfish Centrarchidae Moderate Low Moderate

2 2 0 0 2 0

Misgurnus anguillicaudatus Oriental 

weatherfish Cobitidae Unknown Low Low

0 5 0 1 0 1

Morone americana White perch Moronidae High Moderate High

18 0 2 1 7 0

Neogobius melanostomus Round goby Gobiidae High High Low

13 2 13 0 1 0

Notropis buchanani Ghost shiner Cyprinidae Unknown Low Low

0 5 0 0 0 1

Noturus insignis Margined madtom Ictaluridae Unknown Low Low

1 4 0 0 0 1

Oncorhynchus gorbuscha Pink salmon Salmonidae Unknown Low Moderate

1 3 1 0 2 1

Oncorhynchus kisutch Coho salmon Salmonidae Moderate Low High

3 2 0 0 12 0

Oncorhynchus mykiss Rainbow trout Salmonidae High Low High

9 2 0 1 12 2

Oncorhynchus nerka Kokanee salmon Salmonidae Unknown Low Low

0 4 0 0 1 0

Oncorhynchus tshawytscha Chinook salmon Salmonidae Moderate Low High

2 3 0 0 13 1
7

Osmerus mordax Rainbow smelt Osmeridae High Unknown High

12 2 0 3 14 0

Petromyzon marinus Sea lamprey Petromyzontid

ae

High High Low

12 0 18 1 0 0

Phenacobius mirabilis Suckermouth 

minnow Cyprinidae Low Low Low

0 0 0 0 0 1

Proterorhinus semilunaris Tubenose goby Gobiidae Unknown Low Low

0 3 0 1 0 0

Salmo trutta Brown trout Salmonidae High Low High

9 2 0 1 6 0

Scardinius erythrophthalmus Rudd Cyprinidae Moderate Unknown Unknown

3 2 0 2 1 2

Available information was insufficient to judge the environmental impacts for 14 species, the 

socio-economic impact for 4 species, and beneficial impacts for 4 species. Particularly lacking 

was information on the impacts of fishes on the physical environment and water quality. 

Only one species – Oncorhynchus kisutch - scored as highly beneficial with only moderate 

environmental and low socio-economic impact. All other highly beneficial species also had 

offsetting high negative impacts. One fish species - Alosa pseudoharengus - scored high on all 

three assessments (high environmental, socio-economic, AND beneficial impacts). Five fish 

species - Cyprinus carpio, Morone americana, Oncorhynchus mykiss, Osmerus mordax, and 

Salmo trutta - scored as highly beneficial, but with offsetting high negative environmental 

impacts.

Two fish species - Neogobius melanostomus and Petromyzon marinus - were assessed as having 

high environmental and socio-economic impacts, but low benefits. 

Three additional species – Gymnocephalus cernuus, Lepomis microlophus, and Scardinius 

erythrophthalmus - were determined to have moderate environmental impacts (with low or 

unknown socioeconomic impacts and benefits).

Only Phenacobious mirabilis scored as low impact on all three assessments. 

3.2 Annelids

Table 3 Organism impact assessment scores for established nonindigenous annelids in the Great Lakes basin.

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Branchiura sowerbyi Tubificid worm Tubificidae Unknown Low Unknown

1 5 0 1 1 1

Gianius aquaedulcis Tubificid worm Tubificidae Unknown Low Low

0 6 0 1 0 0

Potamothrix bedoti Tubificid worm Tubificidae Unknown Low Low

0 6 0 1 0 1

Potamothrix moldaviensis Tubificid worm Tubificidae Unknown Low Low

0 6 0 1 0 1

Potamothrix vejdovskyi Tubificid worm Tubificidae Unknown Low Low

0 6 0 1 0 1

Ripistes parasita Oligochaete Naididae Unknown Low Low

0 6 0 1 0 1
8

Available information was insufficient to determine the environmental impact of any of the 

nonindigenous annelids. Direct socio-economic impact of these species is low. Beneficial impact 

is also low for most annelids, though information for Brachiura sowerbyi was insufficient to 

determine benefits. 

3.3 Arthropods (Non-crustacean)

Table 4 Organism impact assessment scores for established nonindigenous arthropods in the Great Lakes basin.

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Acentria ephemerella Water moth Crambidae Unknown Low Moderate

1 3 0 1 2 2

Tanysphyrus lemnae Duckweed weevil Erirhinidae Unknown Low Low

0 4 0 0 0 1

Acentria epemerella has some capacity for bio-control of the nonindigenous Myriophyllum 

spicatum which was assessed here as a moderate beneficial impact. These two insect species 

otherwise have no socio-economic or beneficial impact. More information is needed as to the 

way these species interact with native species (competition, predator-prey) and environment 

(physical and water quality) in order to determine their environmental impacts. 

3.4 Bryozoans

Table 5 Organism impact assessment scores for established nonindigenous bryozoans in the Great Lakes basin.

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score # Unknown Score #

Unknown Score #Unknown

Lophopodella carteri Freshwater 

bryozoan Olindiidae Unknown Unknown Low

0 4 0 4 0 1

The one nonindigenous bryozoan was assessed to have little to no benefit in the Great Lakes 

region. Available information is insufficient to determine whether or not it has significant 

environmental or socioeconomic impacts.

3.5 Coelenterates

Table 6 Organism impact assessment scores for established nonindigenous coelenterates in the Great Lakes basin. 

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Cordylophora caspia Freshwater 

hydroid Clavidae Unknown Unknown Low

0 4 1 2 0 1

Craspedacusta sowerbyi Freshwater

jellyfish Olindiidae Unknown Low Low

0 4 0 1 0 1

The two nonindigenous coelenterates were assessed to have little to no benefit in the Great Lakes 

region. Craspedacusta sowerbyi was determined to have little to no socioeconomic impact. 

More information is needed on the realized impact of Cordylophora caspia on recreation and 

aesthetics in order to determine whether it has significant socio-economic impact. Current 
9

information is insufficient to determine the environmental impact of these two species. 

3.6 Crustaceans

Table 7 Organism impact assessment scores for established nonindigenous crustaceans in the Great Lakes basin.

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Argulus japonicus Parasitic oarsman Argulidae Unknown Unknown Low

1 2 0 3 0 0

Bythotrephes longimanus Spiny waterflea Cercopagidae High Low Low

7 2 1 0 0 0

Cercopagis pengoi Fishhook waterflea Cercopagidae High Low Low

7 2 1 0 0 1

Cyclops strenuus Oarsman Cyclopidae Unknown Low Low

1 2 1 0 0 0

Daphnia galeata galeata Waterflea Daphniidae Unknown Low Low

1 2 0 0 0 0

Daphnia lumholtzi Waterflea Daphniidae Unknown Low Unknown

0 4 0 1 1 1

Echinogammarus ischnus Scud Gammaridae Moderate Low Low

2 1 0 0 0 0

Eubosmina coregoni Waterflea Bosminidae Unknown Low Low

0 4 0 0 1 0

Eubosmina maritima Cladoceran Bosminidae Unknown Low Low

0 2 0 0 0 0

Eurytemora affinis Oarsman Temoridae Unknown Unknown Low

0 5 0 3 0 1

Gammarus tigrinus Amphipod Gammaridae Unknown Low Low

0 4 0 0 0 1

Hemimysis anomala Bloody red shrimp Mysidae Unknown Low Low

0 5 0 1 0 1

Heteropsyllus nr. nunni Oarsman Canthocamptid

a

Unknown Low Low

0 2 0 0 0 0

Megacyclops viridis Oarsman Cyclopidae Unknown Low Low

0 2 0 0 0 1

Neoergasilus japonicus Parasitic oarsman Ergasilidae Unknown Low Low

1 2 0 1 0 0

Nitokra hibernica Oarsman Ameiridae Unknown Low Low

1 2 0 0 0 0

Nitokra incerta Oarsman Ameiridae Unknown Low Low

1 2 0 0 0 0

Salmincola lotae Parasitic oarsman Lernaeopodidae Unknown Low Low

1 2 0 0 0 0

Schizopera borutzkyi Oarsman Diosaccidae Unknown Low Low

0 2 0 0 0 1

Skistodiaptomus pallidus Oarsman Diaptomidae Unknown Low Low

0 5 0 0 0 0

The two nonindigenous raptorial waterfleas – Bythotrephes longimanus and Cercopagis pengoi –

were determined to have high environmental impact. Echinogammarus ischnus was determined 

to have a moderate environmental impact. Information on the other 17 crustacean species –

especially with regard to their interactions with native species - was insufficient to determine 

their environmental impact. For all but two of the species, information was sufficient to 

determine that socio-economic impact was low (the remaining two were unknown). For all but 

one species, information was sufficient to determine that the species brought little to no benefit 
10

to the Great Lakes (Daphnia lumholtzi assessed as unknown benefits). 

3.7 Mollusks

Table 8 Organism impact assessment scores for established nonindigenous mollusks in the Great Lakes basin.

Scientific Name Common Name Family

Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Bithynia tentaculata Faucet snail Bithyniidae High Moderate Low

7 4 2 2 1 0

Cipangopaludina chinensis 

malleata Chinese mystery snail Viviparidae Unknown Unknown Low

0 5 0 2 0 1

Cipangopaludina japonica Japanese mystery

snail Viviparidae Unknown Unknown Unknown

0 5 0 3 0 2

Corbicula fluminea Asian clam Corbiculidae Moderate Moderate Unknown

2 2 2 0 1 1

Dreissena bugensis Quagga mussel Dreissenidae High High Low

25 0 20 0 1 0

Dreissena polymorpha Zebra mussel Dreissenidae High High Low

30 0 25 0 1 0

Elimia virginica Piedmont elimia Pleuroceridae Unknown Low Low

1 5 0 0 0 0

Gillia altilis Buffalo pebblesnail Hydrobiidae Unknown Low Low

0 4 0 0 0 0

Lasmigona subviridis Green floater Unionidae Low Low Low

0 0 0 0 0 0

Pisidium amnicum Greater European 

peaclam Sphaeriidae Unknown Low Low

0 5 0 0 0 0

Pisidium henslowanum Henslow peaclam Sphaeriidae Unknown Low Low

0 5 0 0 0 0

Pisidium moitessierianum Pygmy peaclam Sphaeriidae Unknown Low Low

0 5 0 0 0 0

Pisidium supinum Humpbacked 

peaclam Sphaeriidae Unknown Low Low

0 5 0 0 0 0

Potamopyrgus antipodarum New Zealand 

mudsnail Hydrobiidae Moderate Unknown Low

2 3 1 1 1 0

Radix auricularia European earsnail Lymnaeidae Unknown Low Low

1 4 1 0 0 0

Sphaerium corneum European fingernail 

clam Pisidiidae Unknown Low Low

0 5 0 1 1 0

Valvata piscinalis European stream 

valvata Valvatidae Unknown Low Low

0 5 0 0 0 0

Viviparus georgianus Banded mystery snail Viviparidae Unknown Low Low

0 4 0 0 0 0

No mollusk species were assessed as having significant benefits to the Great Lakes region, 

though information on the two mystery snails of the genus Cipangopaludina was insufficient to 

determine whether they were beneficial or not. 

The two nonindigenous dreissenid mussels were assessed as having high environmental and 

socioeconomic impacts. Bithynia tentaculata was also assessed as having high environmental 

impact, with only moderate socio-economic impact and little-to-no offsetting benefit. Corbicula 

fluminea was assessed as having moderate environmental and socioeconomic impact, and 

Potamopyrgus antipodarum was assessed as having moderate environmental impact with
11

unknown socioeconomic impact. Only Lasmigona subviridis, which is native to adjacent 

drainages of the Atlantic slope, was assessed as having little to no impact. For the remaining 

dozen mollusk species, which includes fingernail clams and a number of snails, available 

information is severely limited and insufficient to determine environmental impact. 

3.8 Plants

Table 9 Organism impact assessment scores for established nonindigenous plants in the Great Lakes basin.

Scientific Name Common 

Name Family Environmental Socio-Economic Beneficial

Score #

Unknown Score # Unknown Score #Unknown

Agrostis gigantea

Redtop, black 

bent, water 

bentgrass

Poaceae

Unknown Low Unknown

0 4 0 0 1 2

Alnus glutinosa Black alder Betulaceae Moderate Low Unknown

2 1 0 0 1 2

Alopecurus 

geniculatus

water foxtail, 

marsh 

meadow-foxtail

Poaceae

Unknown Low Low

1 3 0 0 0 0

Butomus 

umbellatus flowering rush Butomaceae Moderate Unknown Unknown

3 1 1 2 1 1

Cabomba 

caroliniana

Carolina 

fanwort Cabombaceae Moderate Moderate Unknown

4 0 4 0 1 1

Carex acutiformis Swamp sedge Cyperaceae Moderate Low Low

2 2 0 0 0 0

Carex disticha Sedge Cyperaceae Low Low Low

1 0 0 0 0 0

Chenopodium 

glaucum

Oak-leaved 

goosefoot Chenopodiaceae Unknown Low Low

0 2 0 0 0 1

Cirsium palustre marsh thistle Asteraceae Moderate Low Low

2 1 0 0 1 0

Conium 

maculatum

Poison 

hemlock Apiaceae Moderate Moderate Low

2 0 2 0 1 0

Echinochloa 

crus-galli Barnyard grass Poaceae Moderate High Moderate

2 2 6 0 3 0

Epilobium 

hirsutum

Great hairy 

willow herb Onagraceae Moderate Low Low

2 1 0 0 1 0

Frangula alnus Glossy 

buckthorn Rhamnaceae High Low Moderate

13 2 0 0 2 0

Glyceria maxima Reed 

mannagrass

Poaceae Moderate Low Low

3 2 0 0 1 0

Hydrocharis 

morsus-ranae

European 

frogbit Hydrocharitaceae Moderate Moderate Low

3 2 3 0 1 0

Impatiens 

glandulifera

Ornamental 

jewelweed Balsaminaceae Unknown Low Low

1 2 0 0 1 0

Iris pseudacorus Yellow iris Iridaceae High Moderate Moderate

8 3 3 0 2 1

Juncus 

compressus

Flattened rush Juncaceae Moderate Low Low

2 2 1 0 1 0

Juncus gerardii Black-grass 

rush Juncaceae Moderate Low Low

2 2 1 0 1 0

Juncus inflexus European 

meadow rush Juncaceae Moderate Low Low

2 1 1 0 1 0

Lupinus 

polyphyllus Lupine Fabaceae Unknown Low Moderate

1 2 1 0 2 0

Lycopus asper Western water 

horehound Lamiaceae Unknown Low Low

0 2 0 0 0 0

Lycopus 

europaeus

European water 

horehound Lamiaceae Unknown Low Low

1 3 0 0 1 0

Lysimachia 

nummularia Moneywort Primulaceae Unknown Low Low

1 3 0 0 1 0
12

Lysimachia 

vulgaris

Yellow 

loosestrife Primulaceae Moderate Low Low 2 3 0 0 1

0

Lythrum salicaria purple 

loosestrife Lythraceae High Low Unknown 9 0 0 0 1 1

Marsilea 

quadrifolia

European water 

clover Marsileaceae Unknown Low Low 0 4 0 0 1

0

Mentha aquatica Watermint Lamiaceae Unknown Low Low 1 5 0 0 1

0

Mentha gracilis Gingermint Lamiaceae Unknown Low High 0 5 0 1 13

1

Mentha spicata Spearmint Lamiaceae Unknown Low High 0 6 0 0 20

0

Myosotis 

scorpioides

True forget-

me-not Boraginaceae Unknown Low Low 0 2 0 0 1

0

Myosoton 

aquaticum

Water 

chickweed Caryophyllaceae Unknown Low Low 0 2 0 0 0

0

Myriophyllum 

spicatum

Eurasian 

watermilfoil Haloragaceae High High Moderate 6 0 10 0 2

0

Najas marina Spiny naiad Najadaceae

Unknown Low Low 0 3 1 0 1

0

Najas minor Brittle 

waternymph Najadaceae Moderate Moderate Low 3 1 2 0 1

1

Nasturtium 

officinale watercress Brassicaceae Unknown Low Moderate 1 3 1 0 4

0

Nymphoides 

peltata

Yellow 

floating-heart Menyanthaceae Moderate Low Moderate 4 1 1 0 2

0

Pluchea odorata 

odorata sweetscent Asteraceae Unknown Low Low 1 5 0 0 1

0

Pluchea odorata 

succulenta Marsh fleabane Asteraceae Unknown Low Low 1 4 0 0 1

0

Poa trivalis rough

-stalked 

meadow grass Poaceae Low Low Low 0 1 0 0 1

0

Polygonum 

persicaria

Spotted 

knapweed Polygonaceae

Unknown High Moderate 1 2 6 0 2

0

Potamogeton 

crispus

Curlyleaf 

pondweed Potamogetonaceae Moderate Moderate Moderate 5 0 4 1 3

0

Puccinellia 

distans

reflexed salt 

grass

Poaceae Low Low Moderate 0 1 0 0 2

0

Rorippa sylvestris creeping 

yellow cress Brassicaceae Unknown Low Low 1 3 1 0 0

0

Rumex longifolius Yard dock Polygonaceae Unknown Unknown Low 1 2 1 1 0

0

Rumex 

obtusifolius Bitter dock Polygonaceae Unknown Unknown Low 1 2 1 1 0

0

Salix alba White willow Salicaceae Unknown Low High 0 6 1 0 9

0

Salix fragilis Crack willow Salicaceae Unknown Moderate Moderate 1 5 2 0 2

0

Salix purpurea Purple willow Salicaceae Unknown Low Moderate 0 5 0 0 2

0

Solanum 

dulcamara

Bittersweet 

nightshade Solanaceae Moderate Moderate Low 2 2 2 0 1

0

Solidago 

semperviren

Seaside 

goldenrod Asteraceae Unknown Low Low 1 4 0 0 0

0

Sparganium 

glomeratum Bur reed Sparganiaceae Unknown Low Low 0 6 0 0 0

1

Trapa natans Water chestnut Trapaceae Moderate High Moderate 5 0 8 0 3

1

Typha 

angustifolia

Narrow-leaved 

cattail Typhaceae High Low High 8 0 0 0 7

0

Veronica 

beccabunga

European 

brooklime Scrophulariaceae Unknown Low Low 3 3 0 0 0

0
13

Available information on 28 of the 55 nonindigenous plant species (~ 50%) was insufficient to 

determine the environmental impact. Especially lacking is information on interactions between 

nonindigenous plants and native consumers as well as potential to hybridize with native species.

Of the species for which all three assessments were completed, only two (7%) – Carex disticha

and Poa trivialis – were assessed as having low environmental, socioeconomic, AND beneficial 

impact. 

Myriophyllum spicatum leads the list of worst invasive plants having both significant 

environmental and socioeconomic impacts. Other species with high environmental OR 

socioeconomic impacts (without equivalent or higher offsetting benefits) include Echinochloa 

crus-galli, Frangula alnus, Iris pseudacorus, Lythrum salicaria, Polygonum persicaria, and 

Trapa natans. Typha angustifolia stands out as the only nonindigenous plant species to have both 

high beneficial and high environmental impact. 

Three species – Mentha gracilis, Mentha spicata, and Salix alba – have high benefits and low 

negative socioeconomic impact. Unfortunately, the available information was insufficient to 

assess the environmental impact of any of these three. Other nonindigenous plants species with 

moderate benefits and no known offsetting negative impacts include Lupinus polyphyllus, 

Nasturtium officinale, Puccinellia distans, and Salix purpurea. More information on 

environmental impacts is needed for most of these species.

A large set of species have moderate environmental and/or socioeconomic impacts along with 

low benefits – these include: Carex acutiformis, Cirsium palustre, Conium maculatum, 

Epilobium hirsutum, Glyceria maxima, Hydrocharis morsus-ranae, Juncus compressus, Juncus 

gerardii, Juncus inflexus, Lysimachia vulgaris, Nymphoides peltata, and Solanum dulcamara. 

One species – Puccinellia distans – scored as having moderate environmental, socioeconomic,

AND beneficial impacts.

3.9 Algae

Table 10 Organism impact assessment scores for established nonindigenous algae in the Great Lakes basin.

Scientific Name Common Name Family Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Actinocyclus normanii 

fo. subsalsa Diatom Hemidiscaceae

Moderate Low Low

2 0 1 0 1 0

Bangia atropurpurea Red alga Bangiaceae Unknown Low Low

1 2 0 1 0 0

Chaetoceros muelleri Diatom Chaetocerotaceae Low Low Low

0 0 0 0 0 0

Chroodactylon 

ramosum Red alga Stylonemataceae Low Low Low

0 0 0 0 0 0

Cyclotella atomus Diatom Stephanodiscaceae Low Low Low

0 1 0 0 1 0

Cyclotella cryptica Diatom Stephanodiscaceae Low Low Low

0 0 0 0 1 0

Cyclotella 

pseudostelligera Diatom Stephanodiscaceae Low Low Low

0 0 0 0 1 0

Cylindrospermopsis 

raciborskii Cylindro Nostacaceae Low Moderate Low

1 0 2 0 0 0

Diatoma ehrenbergii Diatom Fragilariaceae Low Low Low

0 0 0 0 0 0
14

Discostella woltereckii Diatom Stephanodiscaceae Low Low Low

0 0 0 1 0 0

Enteromorpha 

flexuosa subsp. 

flexuosa

Grass kelp Ulvaceae

Moderate Moderate Moderate

2 0 3 0 2 0

Enteromorpha 

intestinalis

Grass kelp Ulvaceae Moderate Low Low

2 0 1 0 0 0

Enteromorpha 

prolifera

Grass kelp Ulvaceae Low Low Low

1 0 1 0 0 0

Hymenomonas roseola Coccolithophorid Hymenomonadaceae Unknown Low Low

0 3 0 0 0 0

Nitellopsis obtusa Starry stonewort Characeae Moderate High Low

4 0 7 1 1 0

Pleurosira laevis Diatom Biddulphiaceae

Unknown Low Low

0 2 0 0 0 1

Skeletonema potamos Diatom Skeletonemataceae Low Low Low

0 1 0 0 1 0

Skeletonema 

subsalsum Diatom Skeletonemataceae Low Low Low

0 0 0 0 0 0

Sphacelaria fluviatilis Brown alga Sphacelariaceae Low Low Low

0 0 0 0 0 0

Sphacelaria lacustris Brown alga Sphacelariaceae Low Low Low

0 0 0 0 0 0

Stephanodiscus 

binderanus Diatom Stephanodiscaceae Low Moderate Low

1 0 4 0 1 0

Stephanodiscus 

subtilis Diatom Stephanodiscaceae Low Low Low

0 1 0 0 0 1

Thalassiosira baltica Diatom Thalassiosiraceae Low Low Low

0 1 0 0 0 0

Thalassiosira 

guillardii Diatom Thalassiosiraceae Low Low Low

0 0 0 0 0 0

Thalassiosira lacustris Diatom Thalassiosiraceae Low Low Low

0 0 0 0 0 0

Thalassiosira 

pseudonana Diatom Thalassiosiraceae Low Low Low

0 0 0 0 1 0

Thalassiosira 

weissflogii Diatom Thalassiosiraceae Low Low Low

0 0 0 0 1 0

Information on algae impacts was surprisingly readily available. Information insufficient to 

determine environmental impact for only three of the algae species, and all species were able to 

be assessed for socio-economic and beneficial impacts. More information is needed on 

competition to assess these remaining species.

No algae species were assessed as having high environmental impacts. Four species of algae –

Actinocyclus normanii, Nitellopsis obtusa, Enteromorpha flexuosa, and Enteromorpha

intestinalis were assessed as having moderate environmental impacts. All of these species have 

significantly impacted water quality outside the Great Lakes and have had measureable localized 

effects on water quality in the Great Lakes. 

Nitellopsis obtusa has high socio-economic impact in the Great Lakes (widespread inhibition of 

recreational activities). Three additional species were assessed to have moderate socio-economic 

impact – Stephanodiscus binderanus, Enteromorpha flexuosa, and Cylindrospermopsis 

raciborskii. Only Enteromorpha flexuosa was assessed as having a (moderate) offsetting 

beneficial impact.
15

3.10 Amoebae

Table 11 Organism impact assessment scores for established nonindigenous testate amoebae in the Great Lakes 

basin.

Scientific Name Common 

Name Family Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Psammonobiotus 

communis

Unknown Low Low

0 3 0 0 0 0

Psammonobiotus 

dziwnowi

Unknown Low Low

0 3 0 0 0 0

Psammonobiotus 

linearis

Unknown Low Low

0 0 0 0 0 0

Three species of testate amoebae have recently been identified that are believed to be 

nonindigenous to the Great Lakes. These species are expected to have low socio-economic 

impact and no beneficial impact, but information is insufficient to assess their environmental 

impact.

3.11 Parasites & Diseases

Table 12 Organism impact assessment scores for established nonindigenous parasites and diseases in the Great 

Lakes basin.

Scientific Name Common 

Name Family Environmental Socio-Economic Beneficial

Score #

Unknown Score #Unknown Score #Unknown

Aeromonas salmonicida furunculosis Pseudomonadaceae Low Low Low

1 0 1 0 0 0

Piscirickettsia cf. 

salmonis Muskie pox Moderate Low Low

2 0 1 0 0 0

Renibacterium 

(Corynebacterium) 

salmoninarum

BKD Corynebacteriaceae

High High Low

6 0 12 0 0 0

Bothriocephalus 

acheilognathi Asian tapeworm Low Low Low

1 0 1 0 0 0

Dactylogyrus 

amphibothrium fluke Dactylogyridae Low Low Low

0 0 0 0 0 0

Dactylogyrus 

hemiamphibothrium fluke Dactylogyridae Low Low Low

0 0 0 0 0 0

Dugesia polychroa flatworm Planariidae Low Low Low

0 0 0 0 1 0

Ichthyocotylurus 

pileatus fluke High Low Low

6 0 0 0 0 0

Neascus brevicaudatus fluke Diplostomatidae Low Low Low

0 0 0 0 0 0

Scolex pleuronectis cestode Low Low Low

0 0 0 0 0 0

Timoniella sp. fluke Acanthostomatidae Low Low Low

0 0 0 0 0 0

Acineta nitocrae Suctorian ciliate Acinetidae Low Low Low

0 0 0 0 0 0

Glugea hertwigi microsporidean Glugeidae Low Low Low

0 0 0 0 0 0

Heterosporis sp. Microsporidean High Low Low

7 0 0 0 0 0

Myxobolus cerebralis Whirling disease Myxosomatidae High Low Low

7 0 1 0 0 0
16

Sphaeromyxa 

sevastopoli Myxosporean Low Low Low

0 0 0 0 0 0

Trypanosoma acerinae flagellate Low Low Low

0 0 0 0 0 0

Novirhabdovirus sp.

Viral 

Hemorrhagic 

Septicemia 

(VHS)

Novirhabdoviridae

High High Low

7 0 7 0 0 0

Ranavirus sp. LMBV Iridoviridae High Low Low

6 0 0 0 0 0

Rhabdovirus carpio SVC High Low Low

6 0 1 0 0 0

All AIS assessed in this category are parasites/disease of fish. Information on parasites and 

diseases is relatively good – for no species was the information insufficient to complete an 

assessment. As might be anticipated, all of these species are assessed as having low benefit. 

Surprisingly, only two (10%) of the species– viral hemorrhagic septicemia (VHS) and bacterial

kidney disease (BKD) - were assessed as having significant (high) socio-economic impact. 

Many additional species in this category (40%) were assessed as having significant 

environmental impacts. High impact parasites/diseases include VHS and BKD as well as 

whirling disease, large mouth bass virus, spring viremia of carp, Heterosporis, and the fluke 

Icthyocotylurus pileatus. Muskie pox was assessed as having moderate environmental impact.

4. DISCUSSION

The impact assessment was applied to 182 established nonindigenous species. The state of 

scientific knowledge for nearly half (49%) of these species is insufficient to assess the overall 

environmental impact. Of those 93 species where knowledge was sufficient to support 

environmental impact assessment, 25 species (27%) have had a high impact, 32 species (34%) 

have had a moderate impact, and 37 species (40%) were considered low impact. Species that had 

high environmental impact included eight fishes (alewife, common carp, white perch, round 

goby, rainbow trout, rainbow smelt, sea lamprey, and brown trout), two crustaceans (spiny 

waterflea and fishhook waterflea), three mollusks (zebra mussel, quagga mussel, and faucet 

snail), five plants (glossy buckthorn, yellow flag iris, purple loosestrife, Eurasian watermilfoil, 

and narrow-leaved cattail), and seven parasites/diseases (VHS, LMBV, SVC, BKD, whirling 

disease, Heterosporis and Ichthyocotylurus pileatus). Our findings suggest that often quoted 

figures such as ‘only 10% of nonindigenous species become invasive’ significantly 

underestimate environmental impact. Even taking a conservative approach and assuming all the 

unassessed species will prove to have negligible impact, at LEAST 13% of established 

nonindigenous species in the Great Lakes have significant environmental impact. 

Relative to environmental impact, many fewer species were assessed as having unknown socioeconomic impacts and/or beneficial effects. In the latter two sub-assessments, many species 

lacked any evidence to suggest that the species could have a known or unknown significant 

impact. Thirteen species (7%) lacked sufficient knowledge to fully assess the socio-economic 

impacts, with necessary knowledge most often limited with regard to recreational threats and 

decreased water quality. More than three quarters of the assessed species (85%) were assessed as 

having little or no socio-economic impact, while 14 species (8%) and 12 species (7%) had a 

moderate or high socio-economic impact, respectively. Species that had high socio-economic 
17

impact included three fishes (alewife, round goby, and sea lamprey), two mollusks (zebra and 

quagga mussels), four plants (barnyard grass, Eurasian watermilfoil, spotted knapweed, and 

water chestnut), one alga (starry stonewort), and two diseases (BKD and VHS).

The distribution of beneficial effects was similar to the pattern seen in socio-economic impacts. 

We were unable to assess beneficial effect for 15 species (8%) due to insufficient scientific 

knowledge. Of the remaining species, 12 species (7%) have had a high beneficial effect, 17

species (10%) have had a moderate beneficial effect, and 139 species (83%) have had little or no

beneficial effect. Fishes and plants were the only taxonomic groups to contain species with high 

beneficial effects, which largely resulted from their direct recreational and commercial value. Of 

the eight highly beneficial fish species, six (alewife, common carp, white perch, rainbow trout, 

rainbow smelt, and brown trout) were also characterized as having high environmental impacts. 

The two remaining highly beneficial fish species (coho salmon and Chinook salmon) were 

assessed as having moderate environmental impacts. Narrow leaved cattail was also assessed as 

having high (negative) environmental impacts in addition to its high benefits. The environmental 

impact of the remaining three highly beneficial plants (gingermint, spearmint, and white willow) 

could not be assessed. 

To our knowledge, no formal environmental and socio-economic impact assessment of all 

established non-indigenous species in the Great Lakes has been completed prior to this effort, 

although certain species have been qualitatively identified as high-impact invaders (see Great 

Lakes ANS risk assessments summarized by Dupre 2011). For instance, Mills et al. (1993) 

identified nine nonindigenous fauna that have had “substantial impacts” on the ecology or 

economy of the Great Lakes region, including six species identified with a high environmental 

impact in our assessment (sea lamprey, alewife, common carp, brown trout, white perch, and 

zebra mussel) and three species identified with a moderate environmental impact (chinook 

salmon, coho salmon, and ruffe). The Great Lakes Panel on Aquatic Nuisance Species (GLPANS 

2005) also relied on expert judgement to generate a list of harmful, high-priority nonnative 

species, including several recent invaders unmentioned by Mills et al. (1993). Even some of the 

more comprehensive recent risk assessments of Great Lakes ANS have been either limited to 

those species for which sufficient data were available to run ecological niche models (USEPA 

2008) or to those with the potential to disperse beyond the Great Lakes basin (USACE 2011). In 

each case, either a lack of methodological transparency or systematic implementation has

restricted our ability to compare our findings directly to these previous studies. On a qualitative 

basis, our assessment is consistent in identifying as high-to-moderate risk those species called 

out by the previous studies. 

Table 13 Summary of impact assessment results by taxonomic group. For each impact category (i.e. environmental, 

socio-economic, beneficial), the number of species whose impact was assessed as high (H), moderate (M), low (L), 

or unknown (U) is given. Note: “Arthropods” refers to non-crustacean arthropods. 

Environmental Socio-Economic Beneficial

Taxon H M L U H M L U H M L U

Fishes (n=28) 8 5 1 14 3 1 20 4 8 2 13 5

Annelids (n=6) 0 0 0 6 0 0 6 0 0 0 5 1

Arthropods (n=2) 0 0 0 2 0 0 2 0 0 1 1 0

Bryozoans (n=1) 0 0 0 1 0 0 0 1 0 0 1 0

Coelenterates (n=2) 0 0 0 2 0 0 1 1 0 0 2 0
18

Crustaceans (n=20) 2 1 0 17 0 0 18 2 0 0 19 1

Mollusks (n=18) 3 2 1 12 2 2 11 3 0 0 16 2

Plants (n=55) 5 19 3 28 4 8 40 3 4 13 33 5

Algae (n=27) 0 4 20 3 1 3 23 0 0 1 26 0

Amoebae (n=3) 0 0 0 3 0 0 3 0 0 0 3 0

Parasites and Diseases (n=20) 7 1 12 0 2 0 18 0 0 0 20 0

Total 25 32 37 88 12 14 142 14 12 17 139 14

Our results reflect a need for additional research on the environmental impacts of many Great 

Lakes nonindigenous species – especially benthic species other than mollusks (impacts of 

annelids, non-crustacean arthropods, bryozoa, coelenterates, and amoeba are all unknown). Each 

of these taxonomic groups is represented by only a few species, which may reflect a lack of 

study of the group rather than a true lack of invasion. High impact species are taxonomically 

diverse – with all taxonomic groups represented except for the above, under-studied groups 

(which might reasonably be expected to be included if more information was available). 

At least 31% of the nonindigenous species found in the Great Lakes have significant (moderate 

to high) environmental impact. While substantially higher than the oft-cited estimate of ‘10% of 

established nonindigenous species have significant impacts’ this estimate is likely also an underestimate of the true environmental impact. If the 88 currently unassessed species follow the 

trends of the assessed species this number will be closer to 60%. While less substantial, socioeconomic impacts are also likely higher than the 10% figure – we estimate between 14 and 16% 

of the nonindigenous species found in the Great Lakes have moderate to high socioeconomic 

impact. 

Of the 29 species assessed as having significant (moderate to high) benefits, only one –

Puccinellia distans – was assessed as having low environmental and socio-economic impacts. 

Eight of the beneficial species (28%) could not be adequately assessed, but the remaining 20 

species (70%) had significant negative environmental and/or socioeconomic impacts. 

Nonindigenous aquatic fauna have had significant, documented impacts in the Great Lakes, but 

our results suggest that known impacts are far fewer than those that remain to be investigated. 

Prior to this study, available information about these impacts had not been organized and 

compared across all nonindigenous fauna in the Great Lakes. Our research has resulted in the 

collection, synthesis, and analysis of the available scientific knowledge on the impacts of ANS in 

the Great Lakes. The impact assessment results and corresponding literature reviews will not 

only inform scientists, managers, and policymakers about the impacts currently occurring in the 

Great Lakes, but will facilitate the prioritization of future goals and efforts. Furthermore, the 

publication of these products complements all other Great Lakes ANS information currently 

contained in GLANSIS and strengthens the role of GLANSIS as the primary reporting site for 

ANS in the Great Lakes.
19

5. ACKNOWLEDGEMENTS

Many thanks are given to the GLANSIS expert review panel for valuable input and feedback, 

including Anthony Ricciardi, Patricia Chow-Fraser, Hugh MacIsaac, Eugene Stoermer, Sarah 

Bailey, Hunter Carrick, Susan Galatowitsch, Jeff Gunderson, Rex Lowe, Nicholas Mandrak, and 

Robin Scribailo. We also appreciate the feedback received on individual species assessments

from several external reviewers, including Ken Phillips, Leah Elwell, Bernd Blossey, Norman 

Yan, Mark Burrows, Andy Dzialowski, Richard Barbiero, David Barton, Melania Cristescu, 

Jaimie Dick, Pat Hudson, Gerald Mackie, Calum MacNeil, Marten Koops, Tim Campbell, 

Robert Wakeman, John Gannon, Titus Selheimer, Steve Hensler, Thomas Nalepa, and Henry 

Vanderploeg. We thank the staff of the Cooperative Institute for Limnology and Ecosystem 

Research (CILER) and the Great Lakes Environmental Research Laboratory (GLERL) for 

providing many forms of support throughout this project. We also recognize past GLANSIS 

team members, including Gabriela Núñez, Kyle Dettloff, Emily Baker, Katie Thompson, and 

Tom Makled, for their contributions and dedication to the improvement of GLANSIS. This 

research was funded through Great Lakes Restoration Initiative interagency agreement #DW-13-

92312201-0.
20

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23

APPENDIX A. ORGANISM IMPACT ASSESSMENTS

Individual impact assessments for all established nonindigenous fauna are presented by 

taxonomic group. For each species, all six criteria in each impact category were answered as 

accurately as possible using available information on current and historical impacts. For all 

criteria assessed as highly or moderately significant (score of ‘6’ or ‘1’, respectively), evidence 

used to make the assessment is referenced below the response.

A.1 Fishes

Scientific Name: Alosa aestivalis

Common Name: Blueback herring

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• If blueback herring became established throughout Lake Ontario and/or spread to other Great Lakes it

could impede recovery of depressed populations of native fishes such as cisco and lake trout (Owens et al. 

1998). There is also speculation that blueback herring could displace rainbow smelt and/or native forage 

fishes (Marsden and Hauser 2009).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

1 
24

AND/OR

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 √

• If blueback herring became established throughout Lake Ontario and/or spread to other Great Lakes it

could impede recovery of depressed populations of native fishes such as cisco and lake trout (Owens et al. 

1998). There is also speculation that blueback herring could displace rainbow smelt and/or native forage 

fishes (Marsden and Hauser 2009).

• The introduction of blueback herring into Theo Reservoir in Briscoe County, Texas resulted in the 

elimination of large-bodied zooplankton; the community shifted from cladoceran to copepod dominance 

(Guest and Drenner 1991).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Environmental Impact Total 0

Total Unknowns (U) 3
25

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown 

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
26

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

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

BENEFICIAL EFFECT

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

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 

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 6
27

tourism

It is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

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, 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 √

• One study in headwater lakes of Massachusetts indicates that this is a beneficial prey item for largemouth 

bass (Micropterus salmoides) introduced near the blueback’s native range (Yako and Mather 2000).

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
28

Scientific Name: Alosa pseudoharengus

Common Name: Alewife

Environmental: High

Socio-Economic: High

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• Alewife has been shown to cause thiamine deficiency and, consequently, early mortality syndrome (EMS) in 

populations of alewife predators. EMS and its adverse effects on recruitment and fish populations is welldocumented for coho salmon (Oncorhynchus kisutch) (Fitzsimons et al. 1999), lake trout (Fitzsimons et al. 

1999), and Atlantic salmon (Ketola et al. 2000, Madenjian et al. 2008a) (in which it is also referred to as 

Cayuga syndrome (Fitzsimons et al. 1999)), among other fishes.

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Disappearance of native planktivorous salmonids, such as lake whitefish (Coregonus clupeaformis), in the 

Great Lakes has been attributed in part to the introduction of alewife because of reduced zooplankton 

populations (Crowder and Binkowski 1983, Page and Laird 1993, Todd 1986).

• Crowder (1984) speculated that a cisco native to Lake Michigan, the bloater (C. hoyi) evolved fewer and 

shorter gill rakers, and shifted to benthic habitat and diet as a result of competition with alewife.

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 
29

Unknown U

• Alewife likely has an even larger effect on native fish populations through predation of larvae than 

competition for food resources (Eck and Wells 1987, Madenjian et al. 2008a). Using time-series data for 

various fish populations along with change point regression analysis, scientists concluded that predation of 

larvae by alewife likely contributed to the decline of yellow perch (Perca flavescens), deepwater sculpin 

(Myoxocephalus thompsonii), burbot (Lota lota), Atlantic salmon (Salmo salar), lake trout (Salvelinus 

namaycush), and emerald shiner (Notropis atherinoides) (Madenjian et al. 2008a).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 18

Total Unknowns (U) 2

Scoring

Score # U Impact
30

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

• During the 1950s and 60s, dead alewives contributed to oxygen depletion and hypoxia.

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

• Through	predation	and	EMS	effects	on	lake	trout,	it	has	affected	commercial	fisheries	in	lower	4	lakes

Does it inhibit recreational activities and/or associated tourism (e.g., through frequent water closures, equipment
31

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

• Periodic large-scale die-offs littered the beaches of the Great Lakes with rotting fish in the 1960s. Such 

die-offs caused large-scale beach closures (Becker 1983, Brown 1968).

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

• Alewife mortality events that littered the beaches of the Great Lakes with rotting fish happened with such 

frequency that they became known as “the annual spring and summer die-off” (Brown 1968).

Socio-Economic 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

BENEFICIAL EFFECT

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

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

• Alewife	is	extremely	important	as	prey	for	the	salmon	and	trout	fisheries	in	the	Great	Lakes.	
32

These	fisheries	are	both	recreational	and	commercial.

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

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 √

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 

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, 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

• Non-native salmonids in the Great Lakes support a multimillion dollar sport fishing economy and have 

caused alewife populations to decline to the extent that salmonid stocking has been reduced to bolster 

alewife abundance and sustain the sport fisheries (Horns 2010, McCrimmon 2002, Murry et al. 2010).

Beneficial Effect 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
33

1 ≥1
34

Scientific Name: Apeltes quadracus

Common Name: Fourspine stickleback

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Rapid increases of A. quadracus in Thunder Bay suggest that this species is quickly displacing native 

sticklebacks (Stephenson and Momot 2000).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Rapid increases of A. quadracus in Thunder Bay suggest that this species is quickly displacing native 

sticklebacks (Stephenson and Momot 2000).

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 

or extinction of one or more native species

6
35

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?
36

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
37

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

BENEFICIAL EFFECT

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

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

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 √

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 

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
38

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

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, 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
39

Scientific Name: Carassius auratus

Common Name: Goldfish

Negative Environmental: Unknown

Negative Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• According to Moyle (1976), goldfish probably compete with native fishes for food and space.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1
40

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U 

• Richardson et al. (1995) found that goldfish are benthic herbivores whose behavior often results in visible 

increases in turbidity and decreases in aquatic vegetation.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6
41

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

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
42

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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 a common ornamental and pet species (Scott and Crossman 1973). In the United States, large numbers 

are cultured as bait, as forage for sport fishes, and as young fish that are then sold in the aquarium trade, 

mostly as live food (i.e. feeder fish) for carnivorous ornamental fishes (Litvak and Mandrak 1993).

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 a common ornamental and pet species (Scott and Crossman 1973). In the United States, large numbers 

are cultured as bait, as forage for sport fishes, and as young fish that are then sold in the aquarium trade, 

mostly as live food (i.e. feeder fish) for carnivorous ornamental fishes (Litvak and Mandrak 1993).

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 
43

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 

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

reproduction rates of other, fills an important gap in the food web, supports the survival of a species that is 

threatened, endangered, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
44

Scientific Name: Cyprinus carpio

Common Name: Common carp

Environmental Impact: High

Socio-Economic Impact: Unknown

Beneficial Effect: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Laird and Page (1996) stated that common carp may compete with ecologically similar species such as 

carpsuckers and buffalos.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 evidence that common carp prey on the eggs of other fish species (Miller and Beckman 1996, 

Moyle 1976, Taylor et al. 1984). It may thus be responsible for the decline of the razorback sucker 

(Xyrauchen texanus) in the Colorado River basin (Taylor et al. 1984).

• Miller and Beckman (1996) documented white sturgeon (Acipenser transmontanus) eggs in the stomachs of

common carp in the Columbia River.
45

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• Cyprinus carpio has hybridized with goldfish (Carassius auratus) and, in Europe, with the locally native 

crucian carp (C. carassius). However, crucian x common carp hybrids were found in just 3 of 10 

populations in which the two species geographically overlapped (Hänfling et al. 2005, Taylor and Mahon 

1977).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U

• It dislodges plants and roots around in the substrate, which causes a deterioration of habitat for species 

requiring clean water (Bellrichard 1996, Cahoon 1953, Cole 1905, Laird and Page 1996).

• Common carp may destroy aquatic macrophytes directly by uprooting or consuming the plants (Lee et al. 

1980 et seq.), or indirectly by increasing turbidity, thereby reducing light for photosynthesis.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U

• Common carp may destroy aquatic macrophytes directly by uprooting or consuming the plants (Lee et al. 

1980 et seq.) It dislodges plants and roots around in the substrate, which causes a deterioration of habitat 

for species requiring vegetation ((Bellrichard 1996, Cahoon 1953, Cole 1905, Laird and Page 1996).

• One study analyzed the relationship between common carp biomass, vegetative cover, and waterfowl 

abundance over time in a shallow inland lake in Illinois and found that an increase in carp biomass from 

<30 kg/ha to over 250 kg/ha was strongly correlated with a decrease in vegetative cover from its original 

value of 94% to just 17% (Bajer et al. 2009). Waterfowl activity also dropped to ~10% of its original value

(Bajer et al. 2009).

• Destruction and depletion of crayfish (Cambarellus montezumae) habitat by common carp, particularly of 
46

algal species and macrophytes, were deemed to be the major mechanism of crayfish decline (HinojosaGarro and Zambrano 2004).

Environmental Impact Total 12

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Common carp has high lipid content, and has been used to test contamination levels in the Great Lakes for 

comparison to human consumption guidelines. Gewurtz et al. (2010) found that high PCB levels are of 

concern for both sensitive and general populations, especially in mid-large fish.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
47

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 a study of 129 lakes in Iowa, a negative relationship was discovered between C. carpio abundance and 

sportsfish abundance (bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and 

crappie (Pomoxis spp.)) (Jackson et al. 2010). This relationship could be due to the poor water quality 

(e.g., high nutrient levels and low water clarity), which was also associated with high C. carpio abundance; 

however, C. carpio’s role in the decline of the sportsfish populations was not conclusively determined 

(Jackson et al. 2010).

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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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 
48

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

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

• Cyprinus carpio is fished commercially in the Great Lakes by both Canada and U.S. (Brown et al. 1999, 

Dann and Schroeder 2003).

• Cyprinus carpio is commonly used in aquaculture in Mexico and Central America, South America, and 

Eurasia (FAO 2005a). Global aquaculture production of common carp increased 10.4% per year between 

1993 and 2002. At over 33 million tons in 2002, it made up nearly 14% of the global freshwater 

aquaculture production (FAO 2005a).

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

• According to Scott and Crossman (1973), the recreational pursuit of C. carpio was not considered common 

in Canadian waters historically, although it has been gaining popularity among anglers and in the tourism 

fisheries and fish markets in the Great Lakes region. Becker (1983) also described the growing presence of 

C. carpio in many branches of Wisconsin’s recreational and commercial fisheries.

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

• Common carp has high lipid content and has been used to test contamination levels in the Great Lakes for 

comparison to human consumption guidelines (Gewurtz et al. 2010, Pérez-Fuentetaja et al. 2010).

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 

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, or commercially valuable)?
49

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

0 ≥2 Unknown

1 ≥1
50

Scientific Name: Enneacanthus gloriosus

Common Name: Bluespotted sunfish

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

Comments: Only one relevant source was found; statement regarding impact was brief (Hoyer, M.V., and D.E. 

Canfield, Jr. 1994. Handbook of Common Freshwater Fish in Florida Lakes. University of Florida, Institute of Food 

and Agricultural Sciences. Publication SP 160.)

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6
51

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
52

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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 √

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
53

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

BENEFICIAL EFFECT

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 

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

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 √

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
54

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 

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, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
55

Scientific Name: Esox niger

Common Name: Chain pickerel

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 
56

Unknown U

• Chain pickerel is capable of hybridizing and forming viable offspring with related species, including the 

redfin pickerel (Esox americanus) and northern pike (E. lucieus), both present in the Great Lakes basin

(Herke et al. 1990, Scott and Crossman 1973). The consequences of this are unknown.

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6
57

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

• Speculation exists that the predation by chain pickerel could have a negative impact on some sport fishes, 

particularly native trout and other stocked salmonids (Brokaw 2008). Chain pickerel has been actively 

controlled in parts of Maine due to its reputation as a voracious feeder (Brokaw 2008).

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 
58

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

BENEFICIAL EFFECT

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

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

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

• Chain pickerel a popular sport fish in some parts of the Northeast (especially in the winter). In the Great 

Lakes and Canada, it is of minor importance to recreational fishing overall, although it is often kept if 

caught. It is not of commercial importance (Scott and Crossman 1973).

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
59

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

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, 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
60

Scientific Name: Gambusia affinis

Common Name: Western mosquitofish

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Meffe (1983, 1985) found that mosquitofish are very aggressive, even towards larger fishes; this has led to 

the decline of many fish species elsewhere in the U.S. (see Courtenay and Meffe 1989, Deacon et al. 1964,

Whitmore 1997), although documentation of this sort in the Great Lakes is lacking.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Mosquitofish is known to prey on eggs, larvae, and juveniles of various fishes, including those of 

largemouth bass (Micropterus salmoides) and common carp (Cyprinus carpio); it is also known to prey on 

adults of smaller species (Courtenay and Meffe 1989, Meffe 1985).

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 6
61

or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

SOCIO-ECONOMIC IMPACT

Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is poisonous, a virus, 
62

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 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

• Mosquitofish is known to prey on eggs, larvae, and juveniles of various fishes, including fish of 

recreational importance, such as largemouth bass (Micropterus salmoides) (Courtenay and Meffe 1989, 

Meffe 1985).

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 
63

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

BENEFICIAL EFFECT

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

• Anecdotal observations in the early 20th century spurred the reputation of G. affinis as a successful control 

agent of mosquito populations via consumption of their larvae (Pyke 2008). Since these times, many 

studies on the success of mosquitofish as a mosquito control agent have been completed and have often led 

to different outcomes (Pyke 2008).

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

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 √

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 1
64

OR

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U 

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 

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, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
65

Scientific Name: Gymnocephalus cernua

Common Name: Ruffe

Environmental: Moderate

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Savino and Kolar (1996) conducted a laboratory study with ruffe and yellow perch (Perca flavescens) and 

found that competition could occur between the two species, but that the outcome was not always clear, as 

each species exhibited competitive advantages and disadvantages.

• Fullerton et al. (1998) concluded that similarities in dietary preferences and feeding rates of ruffe and 

yellow perch suggest a strong possibility for interspecific competition.

• Kolar et al. (2002) found that in a laboratory setting, ruffe exhibited higher consumption rates of benthic 

invertebrates in darkness over bare cobble and complex substrates than did yellow perch. 

• The increase in ruffe in western Lake Superior was concurrent with declines in several fish species, 

including yellow perch (Perca flavescens), emerald shiner (Notropis atherinoides), and trout-perch 

(Percopsis omiscomaycus) (Bronte 1998, McLean 1993). However, there was a lack of clear causal 

evidence between the two events (Bronte 1998).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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
66

Unknown U

• In Lake Superior, consumption of cisco (Coregonus artedii) eggs by ruffe has been documented at a level 

that could impact the population over winter months (Selegby 1998). There has been a great deal of 

concern that ruffe may have a detrimental effect on more desirable species in Lake Superior, including 

yellow perch and walleye (Sander vitreus), by feeding on the young of these species (Raloff 1992).

• In Scotland, native perch populations have declined and, in Russia, whitefish numbers have declined 

because of egg predation by ruffe (McLean 1993).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High
67

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

• Under a moderate scenario of spread and impact, it was predicted that ruffe could generate costs in excess 

of $500 million by 2050 (Leigh 1998). However, these concerns have yet to be confirmed as the extent of 

ruffe’s contribution to declines in native fish populations remains undecided (Czypinksi et al. 2007).

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

damage, decline of recreational species)?
68

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 √

• When ruffe first invaded Lake Superior, it was thought that this species could generate a considerable cost 

for recreational fishing, particularly by causing a decline in yellow perch (Perca flavescens) populations 

(Leigh 1998). However, these concerns have yet to be confirmed as the extent of ruffe’s contribution to 

declines in native fish populations remains undecided (Czypinksi et al. 2007).

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) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal activity)?
69

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

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

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 

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, 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
70

Scientific Name: Lepisosteus platostomus

Common Name: Shortnose gar

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Anecdotal evidence has suggested that Lepisosteus platostomus may have a negative effect on other fish 

species, including bluegill (L. macrochirus), green sunfish (L. cyanellus), young bass, and muskellunge 

(Becker 1983, Evermann and Goldsborough 1902).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Anecdotal evidence has suggested that Lepomis platostomus may have a negative effect on other fish 

species, including bluegill (L. macrochirus), green sunfish (L. cyanellus), young bass, and muskellunge 

(Becker 1983, Evermann and Goldsborough 1902).

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 6
71

or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?
72

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

• Due to its high abundance and perceived nuisance, it was actively controlled in Lake Chautauqua, NY in 

the late 1890s (Evermann and Goldsborough 1902). Shortnose gar may adversely affect recreationally 

important fishes (e.g., young bass and muskellunge (Esox masquinongy)) (Evermann and Goldsborough 

1902).

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
73

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

BENEFICIAL EFFECT

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 

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

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 

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
74

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 

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, 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 

• Becker (1983) suggested that L. platostomus could contribute to a balanced fish community.

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
75

Scientific Name: Lepomis humilis

Common Name: Orangespotted sunfish

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• It is possible that the orangespotted sunfish competes for food with native fishes such as young bass 

(Micropterus spp.), bluegill (Lepomis macrochirus), and crappie (Pomoxis spp.) (Cross 1967).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

1
76

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6
77

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

• It is possible that the orangespotted sunfish competes for food with native fishes such as young bass 

(Micropterus spp.), bluegill (Lepomis macrochirus), and crappie (Pomoxis spp.) (Cross 1967).

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
78

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

BENEFICIAL EFFECT

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 

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 

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 √

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 √

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 6
79

native species

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

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, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
80

Scientific Name: Lepomis microlophus

Common Name: Redear sunfish

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 inland lakes of southern Michigan, introduced redear is associated with ecological changes in 

populations of pumpkinseed (L. gibbosus), a native molluscivore. Effects of introduced redear sunfish on 

pumpkinseed include reduced consumption of snails by pumpkinseed and reduced population densities 

(Huckins 1997). When introduced into a waterbody, Huckins et al. (2000) found that competition between 

redear sunfish and pumpkinseed resulted in a 56% reduction in pumpkinseed abundance and a 69% 

reduction in average snail biomass when compared with lakes without redear sunfish.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species

population

AND/OR

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 √

• Direct impacts on invertebrates and indirect impacts on vegetation are associated with L. microlophus in 

Tennessee (Ruiz et al. 1999). Mollusk predation by L. microlophus, particularly on gastropods, can result 

in reduced grazing activity, changes in periphyton abundance and community structure, and a shift 

towards phytoplankton-dominated (rather than macrophyte) communities (Martin et al. 1992, McCollum et 
81

al. 1998).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Mollusk predation, particularly on gastropods, can result in reduced grazing activity, changes in 

periphyton abundance and community structure, and a shift towards phytoplankton-dominated (rather than 

macrophyte) communities (McCollum et al. 1998, Martin et al. 1992).

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
82

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
83

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

BENEFICIAL EFFECT

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

• Although redear sunfish is a molluscivore, it is not suitable as a biocontrol agent for zebra mussels; 

experimentally, it significantly prefers gastropods over zebra mussels (French and Morgan 1995).

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

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

• Redear sunfish was intentionally introduced into inland lakes of Michigan to enhance recreational fisheries 
84

(Huckins et al. 2000).

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

• Redear sunfish has been used as a research organism to measure uptake levels of chemicals and toxins in 

other parts of the U.S. (e.g., Bettoli and Clark 1992, Campbell 1994, Eller 1969, Ghent and Grinstead 

1965, Melwani et al.2009, Pickhardt et al. 2006, Saiki et al. 2005, Sorensen 1988).

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 

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, 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
85

Scientific Name: Misgurnus anguillicaudatus

Common Name: Oriental weatherfish

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 concern that if M. anguillicaudatus becomes more abundant and spreads, it will reduce 

populations of aquatic insects important as food to native fishes (Page and Laird 1993).

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 

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

AND/OR

1
86

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Experimentation in Australia on the environmental impacts of oriental weatherfish suggests that this 

species may significantly increase turbidity and nitrogen levels in standing water (Keller and Lake 2007).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?
87

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

• Experimentation in Australia on the environmental impacts of oriental weatherfish suggests that this 

species may significantly reduce macroinvertebrate abundance and increase turbidity and nitrogen levels 

in standing water (Keller and Lake 2007).

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
88

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

BENEFICIAL EFFECT

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 

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 addition to appearing in the aquarium trade, M. anguillicaudatus has been introduced into several parts 

of the world for aquaculture purposes and as a bait fish; however, the occurrence of such use in the Great 

Lakes is not currently known (Welcomme 1988).

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

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
89

Not significantly 0 √

Unknown U 

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 

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, 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
90

Scientific Name: Morone americana

Common Name: White perch

Environmental: High

Socio-Economic: Moderate

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Parrish and Margraf (1990) hypothesized that white perch competes with native yellow perch (Perca 

flavescens) for zooplankton. They determined that growth rates of yellow perch had declined since the 

invasion of white perch in Lake Erie, especially in the western basin. They also determined that the two 

species had considerable diet overlap and found that white perch consumed 27 percent more food than 

yellow perch in one sample.

• It has been speculated that competition between white perch and forage fishes, such as emerald shiner 

(Notropis atherinoides) and spottail shiner (N. hudsonius), as well as freshwater drum (Aplodinotus 

grunniens), is complex and may be responsible for the declines of the latter species (Parrish and Margraf 

1994, Stapanian et al. 2007).

• Within three years of being introduced into a Nebraska reservoir, white perch had completely replaced the 

previously dominant black bullhead (Ameiurus melas) (Hergenrader and Bliss 1971).

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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
91

Unknown U

• Walleye (Sander vitreus) or white bass (Morone chrysops) eggs can make up 100% of white perch diet 

depending on which fish is spawning. During a three-year study, this diet was found to be unique in that: 1) 

eggs were eaten for a comparatively long time; 2) they were the only significant food item eaten by adults 

during two of the three years; 3) large volumes were eaten per individual; and, 4) most fish were feeding. 

White perch also feeds heavily on minnows (Notropis spp.) (Schaeffer and Margraf 1987).

• Madenjian et al. (2000) hypothesized that egg predation by white perch was the most significant 

contributor to the large decline in white bass recruitment in Lake Erie in the 1980s.

• It has been speculated that a white perch diet of Daphnia in Lake Champlain contributed to the decline of 

the species in this locality since white perch became established (Couture and Watzin 2008).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• White perch is known to hybridize with native white bass (Morone chrysops), in western Lake Erie and in 

Ohio and Michigan waters (Todd 1986). Hybrids have also been reported from the Detroit River and the 

St. Clair River in Michigan (Todd 1986). Because these hybrids are capable of backcrossing with the 

parental species, and possibly producing of F2 hybrids by crossing amongst themselves (Todd 1986), they 

dilute the gene pool of each parent species.

• Hybrids of M. americana and M. mississippiensis were first found in 2000 in the middle Illinois River 

(Irons et al. 2002). Hybridization and competition may represent another threat to the already dwindling 

yellow bass of that region.

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0√
92

Unknown U 

Environmental Impact Total 18

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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√
93

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U 

• The collapse of the walleye fishery in the Bay of Quinte (on the north shore of Lake Ontario) coincided with 

an increase in the white perch population and may have been a result of egg predation and lack of 

recruitment (Schaeffer and Margraf 1987).

• Other recreationally/commercially important species, such as white bass (Morone chrysops), yellow perch 

(Perca flavescens), and species of forage fish are likely negatively affected by white perch through 

competition, egg predation, or hybridization (see above).

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

• Other recreationally/commercially important species, such as white bass (Morone chrysops), yellow perch 

(Perca flavescens), and species of forage fish are likely negatively affected by white perch through 

competition, egg predation, or hybridization (see above).

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) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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
94

Not significantly 0 √

Unknown U

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

• As of 2003, it was estimated that over 500,000 lbs. of white perch are caught commercially in the U.S. and 

Canada each year (188,000+ lbs. in the U.S. alone), particularly in Lakes Erie and Ontario (Brown et al. 

1999, Dann and Schroeder 2003). This provides an estimated value of approximately $107,000 yr-1 in the 

U.S. and $260,000 yr-1 overall (Dann and Schroeder 2003). 

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 white perch is a good food fish and could potentially be pursued recreationally, it is not as 

commonly exploited as a game fish (Scott and Crossman 1973). In some Great Lakes states, catch of white 

perch is allowed but is largely prohibited otherwise (GLPANS 2008).

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 

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 

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, 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 7
95

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
96

Scientific Name: Neogobius melanostomus

Common Name: Round goby

Environmental: High

Socio-Economic: High

Beneficial: Low

Comments: Round gobies are one of the only significant predators of Dreissenid mussels, and thus help to fill a gap 

in the food web; however, it is estimated that they only consume about 1% of the standing population (Johnson et al.

2005)

There is speculation that predation on benthic mussels reduces potential habitat for microorganisms or other species

(Lederer et al. 2006), although the extent of round goby impact on substrate type along the lake bottom is unknown.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Round goby, via predation on zebra mussel, likely has the ability to facilitate the bioaccumulation of 

contaminants up the food chain to benthic-oriented piscivores that feed on round goby, although 

experimental results with various contaminants vary (Hogan et al. 2007, Morrison et al. 2000, Ng et al. 

2008).

• Neogobius melanostomus introductions may also be a vector for the spread of avian botulism. The change 

in behavior of infected N. melanostomus may make them preferred prey items to piscivorous birds (Yule et 

al. 2006). In Lake Erie, botulism infected birds had been feeding more on round goby compared to 

uninfected birds (Corkum et al. 2004).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• It competes with rainbow darter (Etheostoma caeruleum), logperch (Percina caprodes), and the endangered 

northern madtom (Noturus stigmosus) for small macroinvertebrates (French and Jude 2001).

• Shelters inhabited by round goby are similar to those of log perch, and in experiments, round goby was a

more aggressive and successful competitor for this limited space, regardless of which species had prior 

residence of the habitat (Balshine et al. 2005).

• Mottled sculpin (Cottus bairdii) has been particularly affected since the establishment of N. melanostomus 

(Marsden and Jude 1995). This is almost certainly due to competition from large round goby (greater than 

100 mm) for spawning sites, from medium round goby (60-100 mm) for space, and from small round goby 
97

(less than 60 mm) for food (Janssen and Jude 2001).

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 a study of Lake Erie tributaries in New York, caddisflies and mayflies were better represented in terms of 

abundance and taxa number, respectively, in streams without round goby, indicating that the goby’s 

consumptive behavior has had an impact on invertebrate communities in this area (Krakowiak and 

Pennuto 2008).

• The numbers of native fish species have declined in areas where the round goby has become abundant 

(Crossman et al. 1992). In laboratory experiments, this species has been found to prey on darters and other 

small fish, as well as lake trout (Salvelinus namaycush) eggs and fry.

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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 
98

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0

Unknown U √

Environmental Impact Total 13

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Round goby, via predation on zebra mussel, likely has the ability to facilitate the bioaccumulation of 

contaminants up the food chain to benthic-oriented piscivores that feed on round goby, although 

experimental results with various contaminants vary (Hogan et al. 2007, Morrison et al. 2000, Ng et al. 

2008).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1
99

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 State of Ohio has shut down the smallmouth bass (Micropterus dolomieu) fishery in Lake Erie during 

the months of May and June because high predation rates by round goby on nests are affecting smallmouth 

bass recruitment. May and June normally account for 50 percent of the total smallmouth catch in Lake Erie 

(NISC 2004).

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

• Walleye anglers (Sander vitreus) in Detroit report that at times, all they can catch are gobies, which 

eagerly attack bait (Marsden and Jude 1995).

• It was noted in a survey-based study that round goby catches led to a perception of poor fishing quality and 

frustration among anglers (Dunning et al. 2006).

Socio-Economic Impact Total 13

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
100

BENEFICIAL EFFECT

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

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

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

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

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 

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, 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 consume zebra mussels; a significant gap in the food web is thus lessened (Johnson et al. 

2005, Vanderploeg 2002), although predation only affected ~1% of dreissenid populations in Lake Erie

• Round goby appeared to make up approximately 75% of burbot (Lota lota) and smallmouth bass diet in 
101

Lake Erie and 36% of lake trout diet in Lake Ontario, indicating that a new energy source may be 

travelling up the food chain (Dietrich et al. 2006, Johnson et al. 2005).

• Round goby also supplements the diet of yellow perch (Weber et al. 2011).

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
102

Scientific Name: Notropis buchanani

Common Name: Ghost shiner

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

Comments:

Information is available regarding morphology, distribution, and other life characteristics, but no evidence or 

descriptions of impact (or lack thereof) could be found in the literature.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1
103

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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)?
104

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
105

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

BENEFICIAL EFFECT

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

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

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 √

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

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
106

Not significantly 0 √

Unknown U 

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, 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
107

Scientific Name: Noturus insignis

Common Name: Margined madtom

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 
108

Unknown U

• Hybrids between Noturus insignis and stonecat (N. flavus) were discovered in Monongahela River 

drainage in West Virginia. Noturus flavus is native to both the river drainage studied and the Great Lakes, 

while N. insignis is non-native to both regions (Welsh and Cincotta 2004). Two one-day population surveys 

were completed in this West Virginia drainage,	the results of which, though limited, indicated that N. 

insignis appeared more abundant than the native N. flavus, and hybrid abundance appeared to match or 

exceed populations of N. flavus (Welsh and Cincotta 2004).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

SOCIO-ECONOMIC IMPACT

Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is poisonous, a virus, 
109

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 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
110

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

BENEFICIAL EFFECT

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

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

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 √

• Noturus insignis is a popular bait fish in parts of the U.S. where it is more abundant (Mills et al. 1993, 

Phelps and Francis 2002). Its significance is unknown in the American Great Lakes (species distribution is 

limited), and it is unimportant in Canada, where the species makes no significant economic contribution 

(Phelps and Francis 2002). 

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
111

Not significantly 0 √

Unknown U

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 

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, 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
112

Scientific Name: Oncorhynchus gorbuscha

Common Name: Pink salmon

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Pink salmon may displace native chubs by way of food competition and may also compete with native cisco 

(Coregonus artedi) (Becker 1983). 

• Pink salmon has also been identified as utilizing spawning habitats similar to those used by brook trout 

(Salvelinus fontinalis), potentially providing another mechanism of competition (Kocik and Jones 1999).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
113

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?
114

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

• Genetic analysis of populations in the St. Marys River, MI indicates that pink salmon is capable of 

hybridizing with recreationally important Chinook salmon (Oncorhynchus tshawytscha) (Kirkpatrick et al. 

2007). Hybridization has the potential to create further competition for the parental species, especially 

since the hybrid appears to have growth rates that exceed those of pink and Chinook salmon.

• Individuals over one year old feed heavily on rainbow smelt (Osmerus mordax) and alewife (Alosa 

pseudoharengus), which are important components of the diets of other Great Lakes salmonids (Diana 

1990, Kocik and Taylor 1987, Kocik et al. 1991).

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 6
115

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 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

BENEFICIAL EFFECT

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

• Although pink salmon is not stocked in the Great Lakes like most introduced salmonids, it has spread to all 

of the Great Lakes; individuals over one year old feed heavily on introduced rainbow smelt and alewife 

(Diana 1990, Kocik and Taylor 1987, Kocik et al. 1991).

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

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

• Although pink salmon is not stocked in the Great Lakes like most introduced salmonids, it has spread to all 

of the Great Lakes, and plays a part in the lakes’ recreational fisheries (Kocik and Taylor 1987). However, 

it has reportedly been caught more frequently by anglers in spawning streams (MIDNR 2003). 

Does the species have some medicinal or research value (outside of research geared towards its control)?
116

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

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 

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, 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
117

Scientific Name: Oncorhynchus kisutch

Common Name: Coho salmon

Environmental: Moderate

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• The introduction of Pacific salmonines is deemed responsible for the introduction of Renibacterium 

salmoninarum, which has caused breakouts of bacterial kidney disease in lake trout (Salvelinus 

namaycush) and has also infected brook trout (S. fontinalis), lake whitefish (Coregonus clupeaformis), and 

bloater (C. hoyi). However, the specific role of coho salmon in this introduction is unknown (Crawford 

2001, see GLANSIS fact sheet for R. salmoninarum).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Fausch and White (1986) suggested that juvenile coho salmon has the ability to outcompete both native 

brook trout (Salvelinus fontinalis) and non-native brown trout (Salmo trutta) for food and space in Great 

Lake tributaries based on laboratory stream experiments involving competition for profitable stream 

positions. The authors also observed that coho salmon emerges earlier in tributaries, which may give it a 

competitive advantage in size over brook and brown trout (Fausch and White 1986).

• Coho salmon competes with native lake trout (Salvelinus namaycush) (Page and Laird 1993).

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)

6 

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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
118

Unknown U √

• Although coho salmon is thought to be less voracious than Chinook (Oncorhynchus tshawytscha), 

controversy has existed in the Great Lakes regarding the effects Pacific salmonines have had on the forage 

fish base, on which other recreational/commercial species depend (Brown et al. 1999). 

• The diet of coho salmon is diverse, including invasive species such as alewife (Alosa pseudoharengus) and 

rainbow smelt (Osmerus mordax), and native species such as yellow perch (Perca flavescens), emerald 

shiner (Notropis atherinoides), ninespine stickleback (Pungitius pungitius), cisco (Coregonus artedii), and 

many aquatic invertebrates (see Crawford 2001).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Rand et al. (1992) found that phosphorus released from salmon carcasses was responsible for >50% of the 

total phosphorus discharged in some Lake Ontario streams during parts of the spring.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Hildebrand (1971) found that spawning significantly reduced the number and weight of invertebrates·ft-2

over the short term due to disturbance of bottom material. Total abundance and weight were reduced by 

66% and 78%, respectively, relative to controls in the December following the autumn 1967 spawning 

(Hildebrand 1971).

Environmental Impact Total 3
119

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U
120

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

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

BENEFICIAL EFFECT

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

• Coho salmon was stocked in all of the Great Lakes by 1968 as a control of alewife populations and as a 

sport fish (Eddy and Underhill 1974).

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
121

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

• They contributed substantially to the recreational fishery, although currently, they are only stocked in Lake 

Michigan and in small numbers in Lake Ontario (FWS/GLFC 2010, Kocik and Jones 1999, NYDEC 2011).

• According to the 2005 Survey of Recreational Fishing in Canada, coho salmon is still harvested by anglers 

in much of the Great Lakes system, but is less prominent than Chinook salmon and many native 

recreational species (Fisheries and Oceans Canada 2008).

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

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 

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, 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) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0
122

0 ≥2 Unknown

1 ≥1
123

Scientific Name: Oncorhynchus mykiss

Common Name: Rainbow trout

Environmental: High

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Stocking of hatchery rainbow trout in rivers has led to the introduction of whirling disease into open waters 

of approximately 20 states including, most recently, the Madison River and its tributaries in Montana (B. 

Nehring and R. White, pers. comm.). Both non-native and native salmonids are susceptible to the disease 

(Yoder 1972). In the Madison River, the disease has reduced the rainbow trout population by 90% (White, 

pers. comm.).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Clark and Rose (1997), Fausch (1988), and numerous papers cited in both discussed several factors 

affecting competitive interactions between rainbow and brook trout (Salvelinus fontinalis), although the 

overall impact of this competition on brook trout is not well known (Crawford 2001). Reportedly, rainbow 

trout also drive nongame fishes such as suckers and northern pikeminnow (Ptychocheilus oregonensis) 

from feeding territories (Li, pers. comm. to P. Moyle in Moyle 1976).

• Rainbow trout and brown trout (Salmo trutta) were deemed at least partially responsible for the extirpation 

of Arctic grayling (Thymallus arcticus) in Michigan, its only known location in the Great Lakes basin 

(Crawford 2001).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

It has resulted in some alteration of the food web structure or processes, the effects of which have 

1 √
124

not been widespread or severe

Not significantly 0

Unknown U 

• Feltmate and Williams (1989) found that the introduction of rainbow trout to an enclosure within a Great 

Lakes tributary in Ontario cause a 35% decline in stonefly abundance relative to areas without rainbow 

trout. Stonefly populations were adversely affected by both predation and disturbance, which led to 

emigration (Feltmate and Williams 1989).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Rainbow trout hybridizes with other rarer trout species, thereby affecting their genetic integrity (Page and 

Burr 1991, Rinne and Minckley 1985).

• Abundant examples exist of hybridization with native trout outside the Great Lakes leading to detrimental 

effects (e.g., Lahontan cutthroat trout (O. clarki henshawi), golden trout (O. aguabonita), and redband trout 

(O. mykiss subsp.)) (Behnke 1992, McAffee 1966a, Moyle 1976).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Crawford et al. (2001) pointed out that salmonids have the potential to alter the energy and nutrient cycles 

of the Great Lakes system through increased energy transfer between open water and streams/tributaries. 

This energy transfer includes the addition of nitrogen and phosphorous to tributaries through decaying 

salmonine carcasses, as well as the addition of salmon eggs and dead fish as a food source in streams 

(Ivan et al. 2011, Parmenter and Lamarra 1991, Rand et al. 1992). The presence of live salmonids may 

have an even greater effect on nutrients in streams through the excretion of ammonium and soluble

reactive phosphorus and their mechanical disturbance of the stream bottom (Ivan et al. 2011, Tiegs et al. 

2009).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

1 
125

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

Environmental Impact Total 9

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture)?
126

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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

BENEFICIAL EFFECT

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

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
127

Not significantly 0 

Unknown U

• The global production of aquacultured rainbow trout has grown continuously, annually producing over

700,000 tons as of 2010 (FAO 2005b).

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

• Rainbow trout has been stocked as a recreational species in the Great Lakes since the 1800s and are 

currently stocked in all five lakes and Lake St. Clair (FWS/GLFC 2010, NYDEC 2011).

• The U.S. Fish and Wildlife Service (2006) estimated that nationally, every dollar spent on hatchery 

programs for rainbow trout returns over $36 of net economic value. One survey estimated the rainbow 

trout recreational fishery to be worth up to $12-14 million annually in Lake Erie, compared to a stocking 

cost of $600,000 (Kelch et al. 2006).

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 √

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 

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, 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 √

• Eggs spawned by steelhead have been found to comprise an important part of the native brown trout diet in 

Great Lakes tributaries, but the effects of this consumption have yet to be understood (Ivan et al. 2011).

Beneficial Effect Total 12

Total Unknowns (U) 2
128

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
129

Scientific Name: Oncorhynchus nerka

Common Name: Kokanee salmon

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
130

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?

Yes, significant effects on human health have already been observed 6
131

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
132

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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 

• In the Great Lakes, it was originally stocked in Lakes Ontario and Huron in order to support recreational 

and potentially commercial fisheries. However, stocking in both lakes ceased by the early 1970s (Crawford 

2001, Kocik and Jones 1999).

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
133

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 

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, 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
134

Scientific Name: Oncorhynchus tshawytscha

Common Name: Chinook salmon

Environmental: Moderate

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

• The introduction of Pacific salmonines is deemed responsible for the introduction of Renibacterium 

salmoninarum, which has caused breakouts of bacterial kidney disease in lake trout (Salvelinus 

namaycush) and has also infected brook trout (S. fontinalis), lake whitefish (Coregonus clupeaformis), and 

bloater (C. hoyi). However, the specific role of coho salmon in this introduction is unknown (Crawford 

2001, see GLANSIS fact sheet for R. salmoninarum).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 the Great Lakes, Chinook salmon competes with native lake trout (Salvelinus namaycush) (Page and 

Laird 1993).

• Scott et al. (2003) found that the presence of Chinook salmon causes delayed nesting and reduced survival 

of Atlantic salmon (Salmo salar) during spawning in Lake Ontario.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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

• Chinook salmon is a predatory fish and may impact populations of smaller fish. Jones et al. (1993) 
135

predicted that maintaining high levels of predator demand by stocking Chinook and other top predators at 

the current rate would eventually lead to an alewife collapse, possibly followed by the further collapse of 

other small forage fish populations.

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Crawford et al. (2001) pointed out that salmonids have the potential to alter the energy and nutrient cycles 

of the Great Lakes system through increased energy transfer between open water and streams/tributaries. 

This energy transfer includes the addition of nitrogen and phosphorous to tributaries through decaying 

salmonine carcasses, as well as the addition of salmon eggs and dead fish as a food source in streams 

(Ivan et al. 2011, Parmenter and Lamarra 1991, Rand et al. 1992). The presence of live salmonids may 

have an even greater effect on nutrients in streams through the excretion of ammonium and soluble

reactive phosphorus and their mechanical disturbance of the stream bottom (Ivan et al. 2011, Tiegs et al. 

2009).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Environmental Impact Total 2

Total Unknowns (U) 3
136

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

damage, decline of recreational species)?
137

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

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

BENEFICIAL EFFECT

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

• Chinook salmon was introduced to control alewife populations in the 1960s; since then, some agencies in 

Lakes Michigan and Ontario have drastically reduced their stocking quotas for Chinook salmon and are 

now concerned about their impact on declining populations of alewife (Schreiner 1995).

• Chinook had totally eliminated rainbow smelt Osmerus mordax in two small New Hampshire lakes where 

the salmon was stocked to control the smelt (McAffee 1966b).

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

• Chinook salmon is a significant catch of the Native American commercial harvest, especially in Lake 

Huron (Bence and Smith 1999).
138

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

• Chinook salmon has remained an important component of the Great Lakes fisheries, and is recreationally 

and economically valuable: from 1967 to 1993, over 259 million Chinook salmon were stocked in the Great 

Lakes (Kocik and Jones 1999); in 2005, nearly 9.5 million Chinook salmon were stocked in the Great 

Lakes system (not including Lake Erie) as reported by various agencies (FWS/GLFC 2010).

• A 2005 survey of anglers fishing in Canada reported an annual recreational harvest of 426,890 Chinook 

salmon in the Great Lakes system (Fisheries and Oceans Canada 2008).

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

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 

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, 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 √

• Eggs spawned by Chinook salmon have been found to comprise an important part of the native brown trout 

diet in Great Lakes tributaries, but the effects of this consumption have yet to be understood (Ivan et al. 

2011).

Beneficial Effect Total 13

Total Unknowns (U) 1

Scoring

Score # U Impact
139

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
140

Scientific Name: Osmerus mordax

Common Name: Rainbow smelt

Environmental: High

Socio-Economic: Unknown

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 the Great Lakes, rainbow smelt may compete with cisco (Coregonus artedi) for food (Becker 1983). 

Christie (1974) supplied some evidence to support this, correlating cisco decline with smelt increases in 

most of the lake.

• Both predation by and competition with rainbow smelt have been implicated in the declines of several 

endangered or special concern species in Canada, including blackfin cisco (Coregonus reighardi) and 

shortnose cisco (Coregonus reighardi), as well as deepwater sculpin (Myoxocephalus thompsonii) 

(COSEWIC 2005, 2006, 2007). Todd (1986) also reported that smelt may be partially responsible for the 

decline of whitefishes (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.

• In a review of rainbow smelt introductions in inland Ontario lakes, Evans and Loftus (1987) found that 13 

of 24 lakes with introduced rainbow smelt experienced a decline in lake whitefish (Coregonus 

clupeaformis) recruitment while 5 of 19 reported declines in cisco.

• A study of Wisconsin inland lakes with and without introduced rainbow smelt from 1985-2004 found that 

young-of-the-year walleye (Sander vitreus) density was significantly lower in invaded lakes (Mercado-Silva 

et al. 2007).

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 1 
141

population

AND/OR

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 

• In different ecosystems, rainbow smelt may be an important a prey item, predator, or competitor (Evans 

and Loftus 1987); in many cases, it may participate in multiple roles relative to a native species.

• Declines, local extirpations, and limitations to recovery of cisco populations have also been attributed to 

rainbow smelt predation on larval fish rather than competition (Hrabick et al. 1998, Stockwell et al. 2009).

• In a review of rainbow smelt introductions in inland Ontario lakes, Evans and Loftus (1987) found that 13 

of 24 lakes with introduced rainbow smelt experienced a decline in lake whitefish (Coregonus 

clupeaformis) recruitment; rainbow smelt are known to feed on the young of lake whitefish.

• A study of Wisconsin inland lakes with and without introduced rainbow smelt from 1985-2004 found that 

young-of-the-year walleye (Sander vitreus) density was significantly lower in invaded lakes (Mercado-Silva 

et al. 2007).

• Both predation by and competition with rainbow smelt have been implicated in the declines of several 

endangered or special concern species in Canada, including blackfin cisco (Coregonus reighardi) and 

shortnose cisco (Coregonus reighardi), as well as deepwater sculpin (Myoxocephalus thompsonii) 

(COSEWIC 2005, 2006, 2007). Todd (1986) also reported that smelt may be partially responsible for the 

decline of whitefishes (Coregonus spp.) in the Great Lakes.

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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 
142

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

Environmental Impact Total 12

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
143

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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 √

• Important recreational species such as walleye and lake trout may both benefit and suffer from 

introductions of rainbow smelt depending on the extent to which rainbow smelt acts as a prey item, 

predator, or competitor (Evans and Loftus 1987).

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) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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
144

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 was estimated in 2003 that the commercial smelt harvest in the U.S. Great Lakes alone was worth over 

$750,000 yr-1—more than lake trout, cisco, or Pacific salmons (Dann and Schroeder 2003).

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

• Rainbow smelt provides a food source to many recreationally important piscivores in the Great Lakes, 

including native burbot (Lota lota), yellow perch, and introduced salmonids. Species such as walleye and 

lake trout may both benefit and suffer from introductions of rainbow smelt depending on the extent to which 

rainbow smelt acts as a prey item, predator, or competitor (Evans and Loftus 1987).

• Historically, recreational harvest of rainbow smelt has also been popular (Scott and Crossman 1998); an 

annual harvest of over 150,000 rainbow smelt in the Great Lakes system was recently reported in a 2005 

survey of anglers in Canada (Fisheries and Oceans Canada 2008).

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 

• Rainbow smelt have been used by USGS to monitor contaminant levels in the Great Lakes (Chernyak et al. 

2005).

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 

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, 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 
145

• Because so many species—including recreational and commercial species—depend on rainbow smelt as a 

food source, rainbow smelt is a vital member of the current food web and are considered by some to be an 

important species to manage and conserve (Schmidt et al. 2009).

Beneficial Effect 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
146

Scientific Name: Petromyzon marinus

Common Name: Sea lamprey

Environmental: High

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• Attack and parasitic feeding on other fishes by adult sea lamprey often result in death of the prey, either 

directly from the loss of fluids and tissues or indirectly from secondary infection of the wound (Phillips et 

al. 1982). Of the fish that survived attacks by sea lamprey, 85% of various species had been attacked up to 

five times (Scott and Crossman 1973).

• Although the number of sea lamprey in the Great Lakes has been reduced, this species still wounds or kills 

substantial numbers of lake trout in some areas and, thus, is impeding the rebuilding of established 

populations (Adair and Young 2007, Madenjian et al. 2008b, Schneider et al. 1996 and references therein).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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

• Because the sea lamprey had greatly reduced the population of large predators, alewife populations 

exploded and were followed by tremendous die-offs, resulting in additional changes to fish species 

composition in the lakes (Smith and Tibbles 1980).
147

• The species' introduction to the Great Lakes and its later abundance, combined with water pollution and 

overfishing, resulted in the decline of several large native species, including several ciscoes (Coregonus

spp.), lake trout (Salvelinus namaycush), and walleye (Sander vitreus), among others.

• A recent study in northern Lake Michigan found that sea lamprey wounding rates in this region have 

increased from 1990-1999 to 2000-2008, despite continued management of sea lamprey populations 

(Madenjian and Desorcie 2010).

• In combination with other factors (e.g., overfishing and hybridization with more common cisco species), 

sea lamprey predation led to the extinction of the deepwater cisco (Coregonus johannae) and shortnose 

cisco (C. reighardi), and the dramatic decline of the blackfin cisco (C. nigripinnis), all endemic to the Great 

Lakes (Jelks et al. 2008, World Conservation Monitoring Centre 1996).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• Although indirect impacts may be more difficult to attribute to sea lamprey, changes in fish species 

composition spurred by sea lamprey introduction (especially the proliferation of alewife) have likely had 

far-reaching indirect effects on other biotic and abiotic components of the Great Lakes ecosystems, 

including plankton communities (J. Gunderson, MN Sea Grant, pers. comm. 2010). 

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• Although indirect impacts may be more difficult to attribute to sea lamprey, changes in fish species 

composition spurred by sea lamprey introduction (especially the proliferation of alewife) have likely had 
148

far-reaching indirect effects on other biotic and abiotic components of the Great Lakes ecosystems, 

including plankton communities (J. Gunderson, MN Sea Grant, pers. comm. 2010). 

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √
149

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• The introduction of sea lamprey caused a collapse in the commercial fisheries during the 1940s and 1950s 

in many parts of the Great Lakes, particularly in lakes Huron and Michigan, and in eastern Lake Superior 

(e.g., Becker 1983, Christie 1974, Courtenay 1993, Emery 1985, Lawrie 1970, Scott and Crossman 1973, 

Smith and Tibbles 1980).

• Furthermore, the cascading impact of sea lamprey introduction, beginning with the decline of native 

commercially fished species and resulting in the explosion of introduced forage fishes and Pacific salmonid 

stocking, was the major force resulting in the transition of the Great Lakes fisheries from being primarily 

commercial-based to primarily recreation-based (J. Gunderson, MN Sea Grant, pers. comm. 2010).

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

• Besides causing declines of native lake trout (Salvelinus namaycush), and walleye (Sander vitreus), sea 

lamprey also took a toll on the introduced salmon in the Great Lakes, much to the dismay of anglers and 

state fish agencies (Scott and Crossman 1973).

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

• Following the collapse of fish stocks in the mid 20th century, sea lamprey was reportedly the best-publicized 

cause of the problem (Francis et al. 1979).

Socio-Economic 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
150

BENEFICIAL EFFECT

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

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

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

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

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 

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, 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
151

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
152

Scientific Name: Phenacobius mirabilis

Common Name: Suckermouth minnow

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
153

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
154

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
155

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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 √

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

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 
156

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, 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
157

Scientific Name: Proterorhinus semilunaris

Common Name: Tubenose goby

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Tubenose goby has been shown to have a significant overlap in diet preference with rainbow darter 

(Etheostoma caeruleum) and may compete with this native fish for food (French and Jude 2001).

• It shares a preference for rocky spawning sites with johnny darter (E. nigrum), but the results of this 

potential competition remain to be seen (Kocovsky et al. 2011).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
158

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
159

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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 √
160

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

BENEFICIAL EFFECT

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

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

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

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

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
161

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 

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, 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
162

Scientific Name: Salmo trutta

Common Name: Brown trout

Environmental: High

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Introduction of the bacteria Aeromanas salmonicida was likely a result of brown trout stocking and has led 

to cases of furunculosis in both native and non-native salmonids, including brook trout (Salvelinus 

fontinalis), Arctic grayling (Thymallus arcticus), and lake whitefish (Coregonus clupeaformis) (Crawford et 

al. 2001, see GLANSIS fact sheet on A. salmonicida.)

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Fausch and White (1981) found that adult brown trout displaced adult native brook trout (Salvelinus 

fontinalis) from the best habitats in a Michigan stream and from the northeast in general. 

• Waters (1999) observed a large-scale replacement of brook trout by brown trout following the introduction 

of brown trout in Valley Creek, MN. Brown trout production increased to 95% of trout biomass in the 

stream by the end of the 15-year study (Waters 1999).

• Brown trout and rainbow trout (Oncorhynchus mykiss) were deemed at least partially responsible for the 

extirpation of Arctic grayling (Thymallus arcticus) half a century ago in Michigan, its only known location 

in the Great Lakes basin (Crawford 2001, p. 143).

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)

6 

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

It has resulted in some alteration of the food web structure or processes, the effects of which have 

not been widespread or severe

1 √
163

Not significantly 0

Unknown U 

• Brown trout has been implicated in reducing native fish populations (especially other salmonids) through 

predation, displacement, and food competition (Taylor et al. 1984). 

• A review by Townsend (1996) documented many impacts of brown trout introductions that have been 

studied in New Zealand, including predation of native galaxiids and their exclusion from stream habitat, 

potential reduction in insect and other invertebrate populations that may lead to reduced grazing, 

increased algal biomass and other trophic effects, and facilitation of the evolution of anti-predator

behavior of some invertebrates.

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• A study by Grant (2002) in Valley Creek, MN, confirmed that hybridization between male brown trout and 

female brook trout occurs in the wild, resulting in a hybrid fish known as tiger trout. It also indicated that 

the interference of brown trout in conspecific brook trout reproduction could contribute to declines in 

brook trout populations (Grant 2002).

• Natural hybridization between brown trout and Atlantic salmon (Salmo salar), a Lake Ontario native, has 

been frequently documented in Europe (Álvarez and Garcia-Vasquez 2011, Hartley 1996, Matthews et al. 

2000). Survival is reportedly highest among male trout x female salmon hybrids, which may have similar 

levels of survival to pure salmon while emerging earlier as fry (Álvarez and Garcia-Vasquez 2011).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √
164

Environmental Impact Total 9

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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 
165

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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 √

• Brown trout were reportedly less popular as a sportfish than brook trout upon their stocking in the Great 

Lakes (Bence and Smith 1999)

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

BENEFICIAL EFFECT

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

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
166

Not significantly 0 √

Unknown U

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

• As of 2009, brown trout continues to be stocked as a sport fish to bolster recreational fisheries in all five 

Great Lakes and Lake St. Clair (FWS/GLFC 2010, NYDEC 2011). This species has grown in popularity 

and contributed substantially to the recreational harvest in most of the Lakes (Bence and Smith 1999, 

Fisheries and Oceans Canada 2008).

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

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 

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, 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
167

0 ≥2 Unknown

1 ≥1
168

Scientific Name: Scardinius erythrophthalmus

Common Name: Rudd

Environmental: Moderate

Socio-Economic: Unknown

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 
169

Unknown U

• In a laboratory setting, Burkhead and Williams (1991) demonstrated that rudd readily hybridizes with 

native golden shiner (Notemigonus crysoleucas), a primary forage species of many native game fishes. 

First generation hybrids offspring should show heterosis (or hybrid vigor), but the "genetic pollution" in 

subsequent generations could prove detrimental due to a variety of factors (e.g., spawning behavior, 

recruitment success, and general loss of fitness) (Burkhead and Williams 1991, Courtenay and Williams 

1992).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Rudd can contribute to ecosystem modification due to their inefficiency of nutrient assimilation, which 

causes much of the nutrients they obtain from macrophytes to be returned to the water column through 

feces deposition (Lake et al. 2002).

• In New Zealand, its main source of food, the macrophyte Egeria, collapsed over time as secchi depth 

decreased. Rudd persisted even after the decline of Egeria, shifting its diet to other plants (Hicks 2003).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Rudd likely contributed to the shift in Hamilton Lake, New Zealand from a macrophyte to phytoplankton 

community; its main source of food, the macrophyte Egeria, collapsed over time as secchi depth decreased 

(Hicks 2003).

Environmental Impact Total 3

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
170

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 √
171

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

BENEFICIAL EFFECT

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 

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 interest in bait culture of rudd dramatically intensified in the early 1980s. The central Arkansas region 

of Lonoke and Prairie counties, an area known for its active fish farming industry, apparently became the 

largest producer of rudd in the United States. Rudd has been widely introduced through a combination of 

bait bucket releases, escapes from aquaculture facilities and farm ponds, and, presumably, by dispersal 

from various points of introduction (e.g., Burkhead and Williams 1991).

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
172

• Rudd has become a popular sportfish in New Zealand (Hicks 2003) and is a popular baitfish in general 

(Litvak and Mandrak 1993, Marsden and Hauser 2009, see GLANSIS fact sheet). Bait bucket release seems 

to be the primary mechanism by which rudd has gained access into open waters. It appears that the 

greatest dispersal of rudd has been through interstate traffic rather than direct European import. In fact, 

much of its recent culture and spread can be attributed to its popularity as bait among striped bass

(Morone saxatilis) anglers.

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

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 

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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
173

A.2 Annelids

Scientific Name: Branchiura sowerbyi

Common Name: Tubificid worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Branchiura sowerbyi, with other oligochaetes, has been documented as a host of myxosporean parasites 

including such fish pathogens as cause swim-bladder disease and haemorrhagic thelohanellosis in Asia 

and Europe; its presence has been correlated to high levels of infection in fish (Liyanage et al. 2003). 

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 6
174

or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Due to its larger size, B. sowerbyi can homogenize layers to a greater depth than some other oligochaetes 

that are abundant in parts of the Great Lakes, including Limnodrilus hoffmeisteri and Tubifex tubifex

(Matisoff et al. 1999).

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
175

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
176

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

BENEFICIAL EFFECT

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

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

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 √

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
177

• Branchiura sowerbyi has been used in the past as a research organism to determine toxic levels of various 

chemicals (e.g., Das and Das 2005, Ghosh and Konar 1983, Saha et al. 2006).

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 

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, 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) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
178

Scientific Name: Gianius aquaedulcis

Common Name: Tubificid worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
179

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
180

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
181

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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
182

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, 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
183

Scientific Name: Potamothrix bedoti

Common Name: Tubificid worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
184

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
185

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
186

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
187

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, 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 √

• Some studies suggest that Potamothrix spp. may have a positive impact on native oligochaetes in Europe. 

The benefit could result from the numerous bacteria found in Potamothrix spp. faeces, which could allow 

for improved feeding by natives (Milbrink and Timm 2001). 

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
188

Scientific Name: Potamothrix moldaviensis

Common Name: Tubificid worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
189

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
190

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
191

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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 

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 
192

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, 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 √

• Some studies suggest that Potamothrix spp. may have a positive impact on native oligochaetes in Europe. 

The benefit could result from the numerous bacteria found in Potamothrix spp. faeces, which could allow 

for improved feeding by natives (Milbrink and Timm 2001). 

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
193

Scientific Name: Potamothrix vejdovskyi

Common Name: Tubificid worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• It is possible, but not confirmed, that P. vejdovskyi competes with Tubifex tubifex (Lang and Lang-Dobler 

1979).

• In a review of the potential invaders of Finnish lakes, Pienimäki and Leppäkoski (2004) listed competition 

with native species and habitat alteration as potential impacts of P. vejdovskyi introduction.

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
194

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

Environmental Impacts 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

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)?
195

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
196

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

BENEFICIAL EFFECT

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

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

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

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 

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
197

Not significantly 0 √

Unknown U 

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, 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 √

• Some studies suggest that Potamothrix spp. may have a positive impact on native oligochaetes in Europe. 

The benefit could result from the numerous bacteria found in Potamothrix spp. faeces, which could allow 

for improved feeding by natives (Milbrink and Timm 2001). 

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
198

Scientific Name: Ripistes parasita

Common Name: Oligochaete worm

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
199

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
200

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

• Ripistes parasita does not burrow into soft substrate or sediment like some annelids; rather, it attaches to 

hard surfaces, including macrophytes or rocks (Smith and Abele 1984). This may have implications for 

man-made infrastructure; however, the potential to attach to and affect infrastructure is unstudied and 

lacks any mention in the literature thus far.

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
201

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

BENEFICIAL EFFECT

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

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

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

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

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
202

Not significantly 0 

Unknown U √

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
203

A.3 Arthropods (Non-crustacean)

Scientific Name: Acentria ephemerella

Common Name: Water moth

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

1 
204

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• A study done at Lake Constance in Europe found A. ephemerella to be an ecosystem engineer through its 

control of macrophyte communities (largely of P. perfoliatus) that many other species, including young-ofthe-year (YOY) and adult fish such as perch, sticklebacks, and pike, used as habitat (Miler 2008).

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

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)?
205

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
206

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

BENEFICIAL EFFECT

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

• Acentria ephemerella has had some success as a biological control agent of Eurasian watermilfoil

(Myriophyllum spicatum) in the Great Lakes region.

• In Lakes Buckhorn and Scugog, part of the Trent Canal system flowing into Lake Ontario, populations of 

introduced Eurasian watermilfoil were decimated in the 1980s, likely due to grazing by A. ephemerella

(Painter and McCabe 1988).

• In Cayuga Lake, the introduction of A. ephemerella was associated with a decline in M. spicatum

populations and the recovery of native macrophytes (particularly Elodea canadensis) during the 1990s 

(Gross et al. 2001, Johnson et al. 1998, Johnson et al. 2000).

• A review on the biocontrol of Eurasian watermilfoil in North America agrees that A. ephemerella, along 

with E. lecontei and Cricotopus myriophylli, has the potential to be an effective control agent; however, 

populations in many study sites were lacking the densities of A. ephemerella needed to be fully effective 

(Newman 2004).

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

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
207

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 √

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 

• A review on biocontrol of Eurasian watermilfoil in North America agrees that A. ephemerella has the 

potential to be an effective control agent (Newman 2004), and has led to declines in this aquatic 

macrophyte in Cayuga Lake and the Kawartha Lakes area (Johnson et al. 1998, Johnson et al. 2000, 

Painter and McCabe 1988). 

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, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
208

Scientific Name: Tanysphyrus lemnae

Common Name: Duckweed weevil

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
209

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
210

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
211

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 √
212

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, 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
213

A.4 Bryozoans

Scientific Name: Lophopodella carteri

Common Name: Freshwater bryozoan

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U√

• The coelomic fluid of L. carteri is known to kill fish and salamanders by damaging gill tissue; however L. 

carteri has been documented in the stomach of at least one live fish in the Great Lakes, yellow perch (Perca 

flavescens) (Ricciardi and Reiswig 1994).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6
214

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?
215

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Encrusting bryozoans, in general, can easily become an economic nuisance by fouling boating and 

recreational equipment, aquaculture infrastructure, and water intake systems (Ricciardi and Reiswig 

1994).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U√

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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 √

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 √
216

Unknown U

Socio-Economic 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

BENEFICIAL EFFECT

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 √

• Lauer et al. (1999) suggested three ways in which L. carteri could prevent recruitment of the zebra mussel 

Dreissena polymorpha: (1) the current produced by bryozoans’ lophophore cilia (used for food selection, 

waste rejection) may physically prevent D. polymorpha larvae from settling; (2) the cover produced by L. 

carteri colonies may cause D. polymorpha larvae to seek alternate substrates; and (3) the coelomic fluid of 

L. carteri fluid may have a detrimental effect on D. polymorpha larvae.

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

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

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

1
217

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U

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 

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
218

A.5 Coelenterates

Scientific Name: Cordylophora caspia

Common Name: Freshwater hydroid

IMPACT RESULTS

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

Comments:

Studies have suggested that Cordylophora caspia may contribute to the restructuring of benthic and pelagic 

freshwater communities (Folino 2000). For example, research found that as compared to uncolonized control 

substrates, the successful inoculation of a substrate with C. caspia resulted in a shift in relative abundance of other 

invertebrates (Ruiz et al. 1999). The specific mechanism is unknown.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √
219

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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
220

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• There are economic costs associated with the biofouling caused by Cordylophora caspia (Folino 2000).

Cordylophora has reportedly caused blockages of intake tunnels and filters and colonize docks, piers, and 

pilings near Chicago harbors of Lake Michigan.

• Cordylophora has had degrading effects on cement and mortar at Brazilian power plants (Berg and FolinoRorem 2009, Folino 2000, Portella and Joukoski 2009). 

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 √
221

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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown 

1 ≥1

BENEFICIAL EFFECT

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

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

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

Does the species have some medicinal or research value (outside of research geared towards its control)?
222

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

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 

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, 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
223

Scientific Name: Craspedacusta sowerbyi

Common Name: Freshwater jellyfish

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
224

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
225

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
226

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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 

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 √

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

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 
227

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, 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
228

A.6 Crustaceans

Scientific Name: Argulus japonicus

Common Name: Parasitic oarsman

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Argulus japonicus parasitizes introduced channel catfish (Ictalurus punctatus) in Tichigan Lake, which 

adjoins the Fox River in Wisconsin as part of the Lake Michigan drainage system. However, it is most 

typically found on Carassius auratus and Cyprinus carpio in drainages in the United States (Amin 1981).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 6
229

or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

SOCIO-ECONOMIC IMPACT

Does the species pose some hazard or threat to human health (e.g., it magnifies toxin levels, is poisonous, a virus, 
230

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 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

• Argulus japonicus parasitizes introduced channel catfish (Ictalurus punctatus). However, it is most 

typically found on Carassius auratus and Cyprinus carpio in drainages in the United States (Amin 1981).

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√

• Argulus japonicus parasitizes introduced channel catfish (Ictalurus punctatus) in Tichigan Lake, which 

adjoins the Fox River in Wisconsin as part of the Lake Michigan drainage system (Amin 1981).

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 
231

Not significantly 0 

Unknown U√

Socio-Economic 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

BENEFICIAL EFFECT

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

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

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

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
232

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 

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, 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
233

Scientific Name: Bythotrephes longimanus

Common Name: Spiny waterflea

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• Significant increases in the trophic position of zooplankton (reduced herbivorous cladoceran biomass and 

increased omnivorous/predatory copepod biomass) and planktivorous fish such as the lake herring 

(Coregonus artedi) with the introduction of Bythotrephes has the potential to lead to substantial 

contaminant biomagnification in consumers (Rennie et al. 2011). However, increased mercury 

concentrations in consumers has not be observe following invasion; this may be attributed to increased 

foraging and growth efficiencies of consumers or to changes in the feeding habits of omnivorous prey 

(Rennie et al. 2011).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Bythotrephes consumes small zooplankton such as small cladocerans, copepods, and rotifers, potentially 

competing directly with planktivorous larval fish for food (Berg and Garton 1988, Evans 1988, 

Vanderploeg et al. 1993).

• Many studies have documented a negative correlation between abundances of Bythotrephes and Leptodora 

(a native waterflea), implying that competition and/or predation from Bythotrephes has played a 

significant role in observed declines of Leptodora (e.g., Branstrator 1995, Fernandez et al. 2009, Foster 

and Sprules 2009, Garton et al. 1990, Lehman and Cáceres 1993, Yan and Pawson 1997).

• Vertical migration has also been observed in Daphnia spp. and copepod (e.g., Diacyclops thomasi, 

Leptomdiaptomus ashlandi, L. minutus) populations following Bythotrephes invasion, indicating that some 

species may alter their spatial distribution (migrate to deeper waters during the day) to avoid Bythotrephes

predation or competition (Bourdeau et al. 2011, Jokela et al. 2011, Lehman and Cáceres 1993). Such 

migration can lead to an indirect negative effect on these native prey species, including reduced individual 

and population growth rates at lower temperatures (Pangle and Peacor 2006, Pangle et al. 2007).

Does it alter predator-prey relationships? 
234

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 decline in native cladocerans following the introduction of Bythotrephes has been observed in Lake 

Huron and Lake Michigan (Barbiero and Tuchman 2004). In Lake Erie, the detection of Bythotrephes in 

1985 was also accompanied by a decline in multiple species of cladocerans (e.g., Eubosmina coregoni, 

Daphnia mendotae, D. retrocurva), including an almost complete absence of Diaphanosoma spp. wherever

Bythotrephes was present in 1986 (Barbiero and Rockwell 2008).

• In Lake Michigan, the decline of D. retrocurva and D. pulicaria populations in contrast to relatively stable 

populations of D. mendotae has been attributed to the latter’s markedly faster escape responses (PichlováPtáčníková and Vanderploeg 2011).

• In some cases, Bythotrephes has been associated with a shift in cladoceran communities towards larger 

taxa over small (likely due to Bythotrephes predation of smaller species) (Barbiero and Rockwell 2008, 

Hovius et al. 2007, Yan and Pawson 1997).

• Many studies have documented a negative correlation between abundances of Bythotrephes and Leptodora 

(a native waterflea), implying that competition and/or predation from Bythotrephes has played a 

significant role in observed declines of Leptodora (e.g., Branstrator 1995, Fernandez et al. 2009, Foster 

and Sprules 2009, Garton et al. 1990, Lehman and Cáceres 1993, Yan and Pawson 1997).

• Vertical migration has also been observed in Daphnia spp. and copepod (e.g., Diacyclops thomasi, 

Leptomdiaptomus ashlandi, L. minutus) populations following Bythotrephes invasion, indicating that some 

species may alter their spatial distribution (migrate to deeper waters during the day) to avoid Bythotrephes

predation or competition (Bourdeau et al. 2011, Jokela et al. 2011, Lehman and Cáceres 1993). Such 

migration can lead to an indirect negative effect on these native prey species, including reduced individual 

and population growth rates at lower temperatures (Pangle and Peacor 2006, Pangle et al. 2007).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 
235

Unknown U √

• Some studies have documented an increase in chlorophyll a abundance with the invasion of Bythotrephes,

potentially due to a release from grazing following increased predation pressure on zooplankton species 

(Barbiero and Rockwell 2008, Hovius et al. 2007). However, an increase in Bythotrephes abundance is not 

always correlated with an increase in chlorophyll a (Foster and Sprules 2009, Strecker and Arnott 2008).

• Notably, Strecker and Arnott (2008) demonstrated that invaded lakes experienced a significant reduction in 

secondary production, and hence a reduction in resources available, in the epilimnion.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Some studies have documented an increase in chlorophyll a abundance with the invasion of Bythotrephes,

potentially due to a release from grazing following increased predation pressure on zooplankton species 

(Barbiero and Rockwell 2008, Hovius et al. 2007). However, an increase in Bythotrephes abundance is not 

always correlated with an increase in chlorophyll a (Foster and Sprules 2009, Strecker and Arnott 2008).

Environmental Impact Total 7

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
236

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 first noticeable impact of Bythotrephes was on fishermen. The tail spines of Bythotrephes hook on 

fishing lines, fouling fishing gear. This problem has largely been eliminated with a switch to line/gear types 

less susceptible to Bythotrephes fouling.

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

Economic Impact Total 1

Total Unknowns (U) 0
237

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
238

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

• Bythotrephes is a food source for fish including yellow perch, white perch, walleye, white bass, alewife, 

bloater chub, Chinook salmon, emerald shiner, spottail shiner, rainbow smelt, lake herring, lake whitefish, 

and deepwater sculpin (Branstrator and Lehman 1996, Bur et al. 1986, Makarewitz and Jones 1990). 

However due to its long tail spine, predation of Bythotrephes is mainly restricted to larger fish and nongape limited species (Pothoven et al. 2007).

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
239

Scientific Name: Cercopagis pengoi

Common Name: Fishhook waterflea

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• In Lake Ontario, it was also thought that the addition of a zooplanktivorous invertebrate could alter the 

food web and increase toxin biomagnification levels in top predators. Conversely, studies indicate that this 

is probably not the case, largely because alewife does not feed heavily on C. pengoi (Thompson et al. 

2005).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Cercopagis pengoi, a relatively small species, is a consumer of other small zooplankton nearly as large as 

itself, including small cladocerans (e.g., Bosmina longirostris, early instars of Daphnia spp.), as well as 

nauplii and early copepodite stages of copepods (Pichlová-Ptáčniková and Vanderploeg 2009). As such, it 

competes with other planktivores of the Great Lakes, including alewife (Alosa pseudoharengus) and 

rainbow smelt (Osmerus mordax) (Bushnoe et al. 2003).

• Yearling alewife directly compete with C. pengoi because they are planktivorous but cannot consume C. 

pengoi due to its caudal appendage.

• The fishhook waterflea is likely to be a competitor of L. kindtii because of similar food preferences, similar 

life histories, and similar habitat preferences; both are found in the epilimnion. (Cavaletto et al. 2010, 

Pichlová and Vijverberg 2001, Pichlová-Ptáčniková and Vanderploeg 2009).

• Because of its large feeding appendages, it is possible that C. pengoi is a more effective predator of 

zooplankton of a broader range in size and escape abilities than is L. kindtii (Pichlová-Ptáčniková and 

Vanderploeg 2009).

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)

6√
240

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 

• Unlike B. longimanus, C. pengoi is too small to impact populations of the native predatory cladoceran, 

Leptodora kindtii, via predation.

• Its long spine makes it less palatable to small planktivorous fish. For these reasons, C. pengoi could have a 

serious effect on the food supply of planktivores.

• The fishhook waterflea is known to make up a portion of the adult alewife diet in Lakes Ontario, Erie, and 

Michigan, but this contribution does not appear significant relative to Bythotrephes longimanus, another 

nonindigenous spined cladoceran, when these species co-occur (Pothoven et al. 2007, Stewart et al. 2009, 

Storch et al. 2007). 

• The fishhook waterflea’s establishment in Lake Ontario in 1998 corresponded with the lowest alewife 

populations in twenty years (Makarewicz et al. 2001). Surveys in the following year indicated that C. 

pengoi was found to account for as much as 73% of crustacean zooplanktonic biomass in the lake (Ojaveer 

et al. 2001).

• Many studies have been conducted on the food web effects of C. pengoi in Lake Ontario. A 2002 study 

showed that the depth at which C. pengoi exists is depleted of small organisms (<0.15 mg) in Lake Ontario 

(Benoit et al. 2002). It was unclear as to whether this is due to predator evasion or C. pengoi consumption, 

but in either case, the smaller organisms are forced into deeper, cooler strata, causing growth rate changes 

(Benoit et al. 2002). 

• Further study in Lake Ontario indicated that in the years following C. pengoi invasion, the density of small 

zooplankton began to drop in the late summer and fall seasons (when C. pengoi is most abundant) (Warner 

et al. 2006). Importantly, Laxson et al. (2003) found that increasing C. pengoi abundance was correlated 

with declines in populations of native zooplankton Daphnia retrocurva, Bosmina longirostris, and 

Diacyclops thomasi in Lake Ontario between 1999 and 2001. Daphnia retrocurva and B. longirostris are 

important prey items of C. pengoi, and appeared to be limited by predation rather than food availability or 

any decrease in fecundity (Laxson et al. 2003). Evidence thus suggests that C. pengoi may have played a 

role in the decline of zooplankton abundance in Lake Ontario. It does not appear, however, that 

zooplankton species richness has been altered as the result of C. pengoi invasion (Stewart et al. 2010).

• Based on findings in the Baltic Sea and Gulf of Finland, it has been predicted that increased predation 

pressure on zooplankton caused by increases in C. pengoi abundance could lead to an increase in 

phytoplankton abundance and an eventual shift in the energy fluxes and eutrophication rates in an 

ecosystem (Litvinchuk and Telesh 2006). In Lake Ontario, Laxson et al. (2003) documented an additional 

correlation between an increase in chlorophyll a concentration and the increase of C. pengoi and decrease 

of herbivorous zooplankton (Laxson et al. 2003). This suggests that C. pengoi likely had a significant topdown (albeit variable) effect on zooplankton communities in Lake Ontario, although these predatory effects 

appear to have declined steadily since the species’ establishment (Laxson et al. 2003).

• Initial research in southwestern Lake Michigan suggested that C. pengoi could have an effect on the food 

web due to predation of rotifers, whose abundance dropped significantly following C. pengoi establishment 

(Witt et al. 2005). However, this implication is taken with caution, as overall zooplankton abundance had 

been in steady decline previous to this study (Witt et al. 2005).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 
241

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

• Based on findings in the Baltic Sea and Gulf of Finland, it has been predicted that increased predation 

pressure on zooplankton caused by increases in C. pengoi abundance could lead to an increase in 

phytoplankton abundance and an eventual shift in the energy fluxes and eutrophication rates in an 

ecosystem (Litvinchuk and Telesh 2006). In Lake Ontario, Laxson et al. (2003) documented an additional 

correlation between an increase in chlorophyll a concentration and the increase of C. pengoi and decrease 

of herbivorous zooplankton (Laxson et al. 2003). This suggests that C. pengoi likely had a significant topdown (albeit variable) effect on zooplankton communities in Lake Ontario, although these predatory effects 

appear to have declined steadily since the species’ establishment (Laxson et al. 2003).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 7

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
242

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

• Cercopagis pengoi fouls fishing lines, which acts both as a nuisance and as a possible mechanism of its 

dispersal and expansion. In a study by Jacobs and MacIsaac (2007), fouling was found to be most intense 

with longer lines and larger trolling distances; accumulation of C. pengoi on a single fishing line towed 1 

km in Lake Ontario was as high as 1,024 individuals and 106 diapausing eggs. Lines specially designed to 

reduce waterflea fouling experienced diminished C. pengoi accumulation (Jacobs and MacIsaac 2007).
243

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

BENEFICIAL EFFECT

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

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

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

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
244

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

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 

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, 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 is possible that C. pengoi could benefit planktivorous fish by preying on smaller zooplankton, which are 

difficult for fish to catch, and storing this energy in a larger body mass, which is easier for fish to prey 

upon. However, this potential benefit is likely insignificant (Vanderploeg et al. 2002).

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
245

Scientific Name: Cyclops strenuus

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• Cyclops strenuus is a host to many different parasites in its native range, including the cestodes 

Diphyllobothrium spp. and Triaenophorus crassus, the latter of which is capable of infecting whitefish 

(Coregonus spp.), pike (Esox lucius) and salmonids (e.g., Salvelinus umbla) (Achleitner et al. 2009). It is 

also a known host of the eel tapeworm Bothriocephalus claviceps; the eel swimbladder nematodes 

Anguillicola spp.; the tapeworms Proteocephalus torulosus and P. neglectus; the acanthocephalid worm 

Pallisentis nagpurensis; and the helminth Traienophorus nodulosus (Dorucu 1999, George and Nadakal 

1983, Moravec et al. 1994a, 1994b, Nagasawa et al. 1994, Pulkkinen et al. 2000, Scholz 1991, 1993, 1997, 

Sysoev 1982).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √
246

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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
247

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

• Cyclops strenuus is an intermediate host of the cestode parasites Diphyllobothrium spp., which also infect 

commercially and recreationally important fish species such as salmonids (e.g., brown trout Salmo trutta

and rainbow trout Oncorhynchus mykiss) (Dorucu et al. 1995). 

• Through the consumption of raw or undercooked fish, Diphyllobothrium spp. can also infect humans, 

causing diphyllobothriasis in the digestive system (USFDA 2009). Although this disease can affect 20 

million people annually, it is considered rare in the United States and is not thought to be present in the 

Great Lakes region currently (Scholz et al. 2009, USFDA 2009).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 √
248

Unknown U

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

BENEFICIAL EFFECT

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

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

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

Does the species have some medicinal or research value (outside of research geared towards its control)?
249

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 

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 

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, 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
250

Scientific Name: Daphnia galeata galeata

Common Name: Waterflea

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• It is possible that hybrid clones of D. g. mendotae x D. g. galeata are more vigorous and fit than parent 

clones, especially in periods of environmental stress. This could have led to rapid expansion of the hybrid 

population, especially in parts of Lake Erie (Taylor and Hebert 1993).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 √
251

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U

• After D. g. galeata was introduced to Lake Erie it rapidly hybridized with native D. g. mendotae. Hybrid 

clones are now common, especially during the summer months in Lake Erie (Taylor and Hebert 1993).

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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)?
252

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
253

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

BENEFICIAL EFFECT

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

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

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

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

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
254

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

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, 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
255

Scientific Name: Daphnia lumholtzi

Common Name: Waterflea

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 competitive experiments between D. lumholtzi and Great Lakes native D. pulex, Dobberfuhl and Elser 

(2002) found that in tanks with mixed populations, D. lumholtzi productivity dropped to 55% of its control 

value, while D. pulex productivity dropped to just 17% of its control value. Combined productivity of the 

daphnids dropped by over 50%, indicating that the presence of D. lumholtzi could facilitate competitive 

exploitation and have adverse impacts on overall productivity of the zooplankton community. 

• Research by Dzialowski (2010) suggests that some Daphnia species are more vulnerable to competition 

with D. lumholtzi (e.g., D. parvula and Ceriodaphnia dubia were more affected than D. magna).

• By occupying a niche that was previously unexploited by Daphnia spp., D. lumholtzi has been hypothesized 

to compete with non-daphnid zooplankton (Dzialowski et al. 2000). One such zooplankter is 

Diaphanasoma, whose population size was significantly lower in Kansas reservoirs following D. lumholtzi

invasion (Dzialowski et al. 2000).

• In situ research comparing native Daphnia spp. to the exotic D. lumholtzi has found that competition 

between these species is lower than expected. Daphnia lumholtzi is a tropical species and is adapted to 

warmer temperatures than native North American Daphnia. Thus, D. lumholtzi population sizes tend to 

increase in late summer when native Daphnia populations have been historically low. As a result, D. 

lumholtzi may be filling a vacant "temporal niche" in the warmer summer months (Dzialowski et al. 2000, 

East et al. 1999, Goulden et al. 1995, Johnson and Havel 2001, Work and Gophen 1999).

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)

6
256

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• If D. lumholtzi outcompetes native zooplankton populations during their normal peak abundance in late 

summer, this may adversely impact planktivorous fish relying on that critical food source but unable to 

tolerate D. lumholtzi’s spines. Larval and juvenile stages of fish are more likely to be unable to consume D. 

lumholtzi due to gape (mouth-size) limitation (Kolar and Wahl 1998).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Soeken-Gittinger et al. (2009) found that the density of D. lumholtzi in some parts of the Illinois River was 

larger than the density of all other native zooplankton combined. High densities appeared to be correlated 

with high temperatures and increased inorganic sediment suspension, suggesting that areas in the Great 

Lakes with these conditions could face the greatest impacts (Soeken-Gittinger et al. 2009).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Environmental Impacts Total 0
257

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
258

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 √

• Potential effects on recreational species remain uncertain.

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

BENEFICIAL EFFECT

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

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
259

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

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

• This species is a common research subject, as scientists have been able to track its spread since 

establishment and to evaluate factors of its invasion success (Havel and Herbert 1993, Havel and Medley 

2006, Havel et al. 2005, Work and Gophen 1999). 

• It has also been studied for its unique ability to proliferate during high cyanobacterial growth, a time when 

few other daphnids are present (Pattinson et al. 2003, Semyalo et al. 2009).

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 

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, 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 √

• Silverside (Menidia beryllina) may be able to utilize this new prey item and survive longer during its late 

summer spawning period (Leinesch and Gophen 2001).

• Leinesch and Gophen (2001) noted that when juvenile fish attain a size capable of consuming D. lumholtzi, 

the fish can grow more rapidly and more easily avoid predation. This is particularly advantageous during 

the summer months, when D. lumholtzi presents itself as a larger prey item than would otherwise occur in 

the zooplankton.

Beneficial Effect Total 1

Total Unknowns (U) 1

Scoring

Score # U Impact
260

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
261

Scientific Name: Echinogammarus ischnus

Common Name: Scud

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• Echinogammarus ischnus has been found to host a parasitic water mold (oomycete) in the St. Lawrence 

River. This oomycete also parasitizes the Great Lakes native amphipod Gammarus fasciatus, but the effects 

are less severe (Kestrup et al. 2011b).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 

• Following its initial establishment, E. ischnus became one of the most abundant non-dreissenid benthic 

invertebrates in the Lake Ontario, Lake Michigan, and Lake Erie watersheds, where it locally displaced the 

native amphipod Gammarus fasciatus from many sites (Dermott et al. 1998, Haynes et al. 2005, Limén et 

al. 2005, Nalepa et al. 2001, Ratti and Barton 2003, Stewart et al. 1998a, 1998b, van Overdijk et al. 2003). 

It has been hypothesized that such displacement is partially due to competition for resources (González and 

Burkhart 2004, Kestrup and Ricciardi 2009b, Limén et al. 2005, Palmer and Ricciardi 2005, Witt et al. 

1997).

• A mechanism for competitive exclusion of G. fasciatus by E. ischnus is less clear and may be influenced by 

total or relative amphipod densities (Kestrup and Ricciardi 2009a, van Overdijk et al. 2003) or by 

differences in the physical environment (Palmer and Ricciardi 2004). 

• For instance, the initial replacement of G. fasciatus by E. ischnus occurred in primarily rocky and 

dreissenid-covered habitats, while G. fasciatus populations continued to persist on algal and macrophytecovered substrates (Dermott et al. 1998, Duggan and Francoeur 2007). These two amphipod species may 

also differ in their responses to abiotic factors such as current velocity or pH, which could affect their 

relative fitness in different environments (Palmer and Ricciardi 2004). Echinogammarus ischnus typically 

numerically dominates high flow sites, and its abundance in the St. Lawrence River has been more 

positively correlated with current velocity than with any other physical attribute (Palmer and Ricciardi 

2004). Kang et al. (2007) also encountered E. ischnus more frequently at high energy coastal sites 

throughout the Great Lakes.

• It has been suggested that E. ischnus has potentially benefited from a co-evolved relationship with 
262

dreissenid mussels (Ricciardi and MacIsaac 2000). Available nutrition from mussel biodeposits, in 

combination with the structural complexity of Dreissena mussel substrate, may have given E. ischnus a 

competitive advantage, stimulating its population expansion in the lower Great Lakes (van Overdijk et al. 

2003). However, at some sites, native amphipods have been found to consume more Dreissena pseudofeces 

than E. ischnus (González and Burkhart 2004). Furthermore, carbon isotopic composition data indicated 

that the diets of E. ischnus and native Great Lakes amphipod G. fasciatus differ, suggesting that 

competition for food is an unlikely mechanism of the species replacement (Limén et al. 2005).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 

• Following its initial establishment, E. ischnus became one of the most abundant non-dreissenid benthic 

invertebrates in the Lake Ontario, Lake Michigan, and Lake Erie watersheds, where it locally displaced the 

native amphipod Gammarus fasciatus from many sites (Dermott et al. 1998, Haynes et al. 2005, Limén et 

al. 2005, Nalepa et al. 2001, Ratti and Barton 2003, Stewart et al. 1998a, 1998b, van Overdijk et al. 2003). 

It has been hypothesized that such displacement is partially due to intraguild predation (González and 

Burkhart 2004, Kestrup and Ricciardi 2009b, Limén et al. 2005, Palmer and Ricciardi 2005, Witt et al. 

1997).

• Studies in the St. Lawrence River have shown that E. ischnus and G. fasciatus are mutual (intraguild) 

predators. Echinogammarus ischnus is generally the superior predator of adult gammarids in waters of 

higher conductivity (Kestrup and Ricciardi 2009b), but this advantage is offset by G. fasciatus preying 

more efficiently on E. ischnus juveniles (Kestrup et al. 2011a). 

• Research in central Europe also reports the invasive E. ischnus to be a stronger predator over native 

gammarids in cases of intraguild predation, suggesting that predation is a probable mechanism of species 

replacement (Kinzler and Maier 2003).

• It is possible that E. ischnus evades predators more easily than G. fasciatus, particularly on dreissenidcovered substrate (González and Burkhart 2004). In laboratory feeding trials, G. fasciatus was more 

heavily consumed by yellow perch (Perca flavescens) and round goby (Neogobius melanostomus) on 

dreissenid-covered substrate than E. ischnus, while E. ischnus was consumed more heavily on macrophyte 

beds (González and Burkhart 2004). In contrast, other studies have found no difference between the two 

species in their vulnerability to predation on dreissenid-covered substrate (Kestrup and Ricciardi 2009a,

Palmer and Ricciardi 2005).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U
263

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
264

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
265

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 

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 
266

threatened, endangered, 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
267

Scientific Name: Eubosmina coregoni

Common Name: Waterflea

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
268

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• In the Great Lakes it can reach densities of around 69,000 individuals m-2 in western Lake Erie and around 

44,500 individuals m-2 in Lake Ontario. It has also been recorded at high densities in the fall in Lake 

Ontario and Lake Michigan (Barbiero et al. 2001, Geller and Müller 1981, Johannsson and O’Gorman 

1991, Roth and Stewart 1973). Such high densities could suggest impacts on the abiotic environment.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

• In the Great Lakes it can reach densities of around 69,000 individuals m-2 in western Lake Erie and around 

44,500 individuals m-2 in Lake Ontario. It has also been recorded at high densities in the fall in Lake 

Ontario and Lake Michigan (Barbiero et al. 2001, Geller and Müller 1981, Johannsson and O’Gorman 

1991, Roth and Stewart 1973). Such high densities could suggest impacts on the abiotic environment.

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
269

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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 
270

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

BENEFICIAL EFFECT

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

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

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 

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
271

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 

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, 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

• When congregated at the surface of Lake Michigan, E. coregoni is an important food item for such fish 

species as bloater (Coregonus hoyi) (Crowder and Crawford 1984).

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
272

Scientific Name: Eubosmina maritima

Common Name: Waterflea

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
273

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
274

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
275

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
276

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, 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
277

Scientific Name: Eurytemora affinis

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Eurytemora affinis has the ability to feed on toxic cyanobacteria and dinoflagellates (Dinophysis spp.) 

(Engström et al. 2000, Setälä et al. 2009). While these do not appear to be their preferred food source, 

consumption of toxic phytoplankton results in the buildup of toxins in zooplankton tissue and feces, which 

consequently can accumulate in benthic organisms, fish, and organisms further up the food chain 

(Engström et al. 2000, Lehtiniemi et al. 2002, Setälä et al. 2009).

• Eurytemora affinis is a probable host and vector for plerocercoids that can infect striped bass in the 

Sacramento-San Joaquin Estuary (Arnold and Yue 1997).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Because E. affinis has become an abundant grazer in parts of the Great Lakes, it is possible that it has had 

important impacts on the food web (Lee et al. 2007).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Because E. affinis has become an abundant grazer in parts of the Great Lakes, it is possible that it has had 
278

important impacts on the food web (Lee et al. 2007).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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
279

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U√

• Outbreaks of cholera are sometimes correlated with copepods, which are common hosts of Vibrio cholerae

(Colwell 2004, Lee et al. 2007, Piasecki et al. 2004). Eurytemora spp. are known to host V. cholerae and 

are the most common of known copepod hosts in the Chesapeake Bay, where this has been studied (Colwell 

2004).

• Eurytemora affinis has the ability to consume cyanobacteria and other toxic algal blooms; studies in the 

Baltic Sea indicate that this is likely an important mechanism of the biomagnification of toxins in 

organisms of economic importance, such as shrimp and fish (Engström et al. 2000, Karjalainen et al. 2008, 

Setälä et al. 2009).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Eurytemora affinis has the ability to consume cyanobacteria and other toxic algal blooms; studies in the 

Baltic Sea indicate that this is likely an important mechanism of the biomagnification of toxins in 

organisms of economic importance, such as shrimp and fish (Engström et al. 2000, Karjalainen et al. 2008, 

Setälä et al. 2009).
280

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

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) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal activity)?
281

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

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

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 

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, 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 √

• Eurytemora affinis could be a significant prey item for fish and other planktivores. Thorp and Casper 

(2003) demonstrated such potential in an enclosure experiment with yellow perch (Perca flavescens) in the 

St. Lawrence River; 99% of E. affinis disappeared from fish enclosures, presumably due to predation.

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
282

Scientific Name: Gammarus tigrinus

Common Name: Amphipod

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

• This species can act as an intermediate host to the acanthocephalan Paratenuisentis ambiguus, whose 

definitive host is Anguilla rostrata (Samuel and Bullock 1981).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• There is a potential for G. tigrinus to exert negative impacts on the native Great Lakes amphipod 

community resulting from predation and competition (Dick 1996, Grigorovich et al. 2005).

• While G. tigrinus can exclude C. pseudogracilis from habitats with good water quality, in poor water 

quality habitats, this may not be the case (MacNeil et al. 2001).

• Increased mortality in the Baltic Sea native amphipod, G. salinus, has been attributed to increased

competition with G. tigrinus over Pilayella littoralis, a mutually-grazed macrophyte species (Orav-Kotta et 

al. 2009). 

• The central European invasion of G. tigrinus has been accompanied by elimination of some native 

amphipod species from parts of the Rhine River, the Baltic Sea, and several waterbodies in the 

Netherlands. It is frequently a superior predator compared to native amphipods and could possibly have a 

reproductive advantage over such indigenous species as G. duebeni, G. zaddachi, and G. pulex

(Grigorovich et al. 2005, Pinkster et al. 1977).

• In Ireland, the native opossum shrimp Mysis relicta has been forced to change its use of microhabitats, 

exposing itself to increased fish predation, as a result of prey overlap with G. tigrinus Bailey et al. 2006). 

• Gammarus tigrinus also preys on relatively small North American amphipod, Crangonyx pseudogracilis, in 

Ireland and could similarly prey on it in the Great Lakes (Dick 1996, Grigorovich et al. 2005).

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 

6
283

native species 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 or decline of at least one native species 

population

AND/OR

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 Baltic Sea, the presence of G. tigrinus appeared to facilitate fish predation on G. salinus in certain 

habitat types (Kotta et al. 2010).

• As a facultative carnivore of other macroinvertebrates, G. tigrinus is thought to influence community 

structure (e.g., trophic relationships) through niche preemption of resources that would normally be 

consumed by its prey (Savage 2000).

• There is a potential for G. tigrinus to exert negative impacts on the native Great Lakes amphipod 

community resulting from predation and competition (Dick 1996, Grigorovich et al. 2005).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √
284

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 
285

Not significantly 0 √

Unknown U

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

• Quickly following its introduction to rivers in Germany and the Netherlands, reports emerged of extreme 

cases in which heavy densities of G. tigrinus had adverse effects on fishing gear and trapped fish (Pinkster 

et al. 1977).

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

BENEFICIAL EFFECT

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

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 √
286

Unknown U

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

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

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 

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, 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 √

• Great Lakes fish likely consume G. tigrinus but this has yet to be studied (H. MacIsaac, pers. comm.; but

see list of Gammarus spp. fish predators in MacNeil et al. 1999).

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
287

Scientific Name: Hemimysis anomala

Common Name: Bloody red shrimp

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• A mysid introduction can increase the biomagnification of contaminants in piscivores through a 

lengthening of the food chain; for example, concentrations of polychlorinated biphenyls and mercury in 

fishes have been shown to be higher in lakes containing mysids than in mysid-free lakes (Cabana et al. 

1994, cf. Rasmussen et al. 1990).

• Through direct transmission and indirect effects on the food web, introduced mysids may cause increased 

parasitism by nematodes, cestodes, and acanthocephalans in fishes (Lasenby et al. 1986, Northcote 1991).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Hemimysis anomala may compete with, or prey upon, other invertebrate predators, such as Bythotrephes 

longimanus and Leptodora kindti. Its omnivory may also reduce local phytoplankton if small-sized juvenile 

mysids are abundant (Ketelaars et al. 1999).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Based on its impacts in some European reservoirs (Ketelaars et al. 1999), H. anomala may reduce 
288

zooplankton biomass and diversity in invaded areas, with cladocerans, rotifers, and ostracods being most 

affected.

• Hemimysis anomala may compete with, or prey upon, other invertebrate predators, such as Bythotrephes 

longimanus and Leptodora kindti. Its omnivory may also reduce local phytoplankton if small-sized juvenile 

mysids are abundant (Ketelaars et al. 1999).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Hemimysis feeds rapidly, even at low prey densities, and its fecal pellets may alter the local physicochemical environment (Ketelaars et al. 1999, Olenin and Leppäkoski 1999, Pienimäki and Leppäkoski 

2004).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• Hemimysis feeds rapidly, even at low prey densities, and its fecal pellets may alter the local physicochemical environment (Ketelaars et al. 1999, Olenin and Leppäkoski 1999, Pienimäki and Leppäkoski 

2004).

Environmental Impact Total 0

Total Unknowns (U) 5
289

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

damage, decline of recreational species)?
290

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 √

• Important fish species could be affected through increased parasitism (Lasenby et al. 1986, Northcote 

1991), toxin biomagnification (Cabana et al. 1994, cf. Rasmussen et al. 1990), or trophic web alterations 

(Ketelaars et al. 1999).

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

BENEFICIAL EFFECT

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

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

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 6
291

tourism

It is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0√

Unknown U 

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

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 

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, 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 √

• Hemimysis anomala is considered a high-energy food source due to its lipid content, which can increase 

growth rates for planktivores (Borcherding et al. 2006). However, the nutritional value of H. anomala can 

vary depending on the food source and trophic position of the individual (Marty et al. 2010). In some lakes, 

mysid (Mysis spp.) introductions have preceded the increased growth of salmonids; in contrast, in other 

lakes they are associated with rapid declines in abundance and productivity of pelagic fishes (Lasenby et 

al. 1986, Langeland et al. 1991, Spencer et al. 1991).

• Stable isotope analysis suggests that H. anomala may be replacing zooplankton in the diet of young yellow 

perch (Yuille et al. in press). It appears that as H. anomala density increases, this species plays a more 

substantial role in supporting higher trophic levels (Yuille et al. in press).

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
292

0 ≥2 Unknown

1 ≥1
293

Scientific Name: Heteropsyllus nr. nunni

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Heteropsyllus nr. nunni has dominated the harpacticoid community in shallow sites (up to 9 m) in Lake 

Michigan. This may either be due to successful competition with native species for similar resources or the 

ability to exploit unused resources (Garza and Whitman 2004, Horvath et al. 2001).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 
294

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
295

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
296

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 √
297

Unknown U 

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, 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
298

Scientific Name: Megacyclops viridis

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• As a large carnivorous copepod, it has been noted to feed on fish larvae and could potentially compete with 

young fish over sources of food such as oligochaetes and other plankton or larval organisms (Fryer 1957).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

1 
299

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
300

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
301

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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 √

• Studies in Eurasia have indicated that M. virdis, like other cyclopoid copepods, could act as a biological 

control agent of certain mosquito larvae, which has implications for dengue fever control in parts of the 

world (Blaustein and Margalit 1994, Dieng et al. 2002, Fryer 1957).

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

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

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

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
302

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U 

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, 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
303

Scientific Name: Neoergasilus japonicus

Common Name: Parasitic oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• In Saginaw Bay, Lake Huron, N. japonicus has most commonly been found infecting pumpkinseed sunfish 

(Lepomis gibbosus), followed in frequency by yellow perch (Perca flavescens), rock bass (Ambloplites 

rupestris), bluegill (Lepomis macrochirus), carp (Cyprinus carpio), channel catfish (Ictalurus punctatus), 

goldfish (Carassius auratus), green sunfish (Lepomis cyanellus), smallmouth bass (Micropterus dolomieu), 

largemouth bass (Micropterus salmoides), and fathead minnow (Pimephales promelas) (Hudson and 

Bowen 2002).

• In 2006, eight new hosts of N. japonicus were discovered in Saginaw Bay, including bluntnose minnow 

(Pimephales notatus), common shiner (Luxilus cornutus), emerald shiner (Notropis atherinoides), golden 

shiner (Notemigonus crysoleucus), quillback (Carpoides cyprinus), sand shiner (Notropis stramineus), 

spotfin shiner (Cyprinella spiloptera), and spottail shiner (Notropis hudsonius) (Hudson and Lesko 2011).

• In 2011, several specimens of N. japonicus were found on green sunfish and bluegill in an Ottawa National 

Wildlife Refuge wetland of Crane Creek, adjacent to Lake Erie and east of Toledo, Ohio (P. Hudson, pers. 

comm.).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

It has resulted in some alteration of the food web structure or processes, the effects of which have 

1 
304

not been widespread or severe

Not significantly 0

Unknown U √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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
305

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

• Neoergasilus japonicus has invaded aquaculture ponds outside of the Great Lakes and has demonstrated 

the ability to infect many types of farm-raised fish (see fact sheet) (Hayden and Rogers 1998). 

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
306

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

BENEFICIAL EFFECT

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

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

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

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
307

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

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 

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
308

Scientific Name: Nitokra hibernica

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• The introductions of N. hibernica and its nonindigenous congener N. incerta are very likely responsible for 

the introduction of the suctorian ciliate Acineta nitocrae to Lake Erie (by N. hibernica) and the Detroit 

River (by N. incerta). Acineta nitocrae is known to be epizooic on these two copepods in the Ukraine 

(Grigorovich et al. 2001).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
309

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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)?
310

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
311

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

BENEFICIAL EFFECT

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

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

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

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

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
312

Not significantly 0 √

Unknown U 

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, 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 

• Nitokra hibernica has been collected from the stomach of one slimy sculpin (Cottus cognatus) in Lake 

Huron, and rainbow smelt (Osmerus mordax) has been known to feed on it in Saginaw Bay, Lake Huron 

(Hudson and Lesko 2011, Hudson et al. 1998).

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
313

Scientific Name: Nitokra incerta

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• The introduction of N. incerta is very likely responsible for the introduction of the suctorian ciliate Acineta 

nitocrae to the Detroit River; A. nitocrae is known to be epizooic on this copepod in the Ukraine 

(Grigorovich et al. 2001).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 
314

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Environmental Impacts 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

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)?

Yes, significant effects on human health have already been observed 6
315

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
316

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 √
317

Unknown U 

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, 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
318

Scientific Name: Salmincola lotae

Common Name: Parasitic oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• In Lake Superior, S. lotae has been known to cause relatively large lesions where the bulla is implanted in 

the mouth of Lota lota. Around 56% of the host species in the Apostle Islands region have been infected at a 

given time, with an average of 3.5 parasites per fish (Hudson and Lesko 2011, Lasee et al. 1988).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 
319

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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)?

Yes, significant effects on human health have already been observed 6
320

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
321

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

BENEFICIAL EFFECT

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

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

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

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

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
322

Not significantly 0 √

Unknown U 

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, 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
323

Scientific Name: Schizopera borutzkyi

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

• Schizopera borutzkyi has altered the species composition of nearshore harpacticoid communities, 

comprising up to 75% of the community at deep sites (15 m) in Lake Michigan. Impact on the food web in 

these communities is unknown, but it is likely that S. borutzkyi is competing with native species for similar 

resources or has the ability to exploit previously unused resources (Horvath et al. 2001).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
324

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
325

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
326

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

BENEFICIAL EFFECT

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

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

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

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

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
327

Not significantly 0 √

Unknown U 

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, 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 √

• Schizopera borutzkyi could have the ability to exploit previously unused resources (Horvath et al. 2001).

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
328

Scientific Name: Skistodiaptomus pallidus

Common Name: Oarsman

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U√

• Based on evidence from an Ohio lake, it has been suggested that S. pallidus is an intermediate host for the 

parasitic worm Tanaorhamphus longirostris, although the study of this occurrence has been limited 

(Hubschman 1983).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

• Skistodiaptomus pallidus became the primary calanoid copepod in a particularly eutrophic portion of Lake 

Tahoe, dominating two previously common species, Leptodiaptomus tyrrelli and Epischura nevadensis

(Byron and Saunders 1981).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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√

• Skistodiaptomus pallidus is an efficient omnivorous predator, with the ability to prey on preferred rotifers 

and microzooplankton from large distances. It also consumes algae and practices cannibalism, which may 

allow populations to persist when resource availability is low (Williamson and Butler 1986, Williamson 

and Vanderploeg 1988).
329

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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
330

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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 6
331

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

BENEFICIAL EFFECT

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

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

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

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 √
332

Unknown U

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 

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, 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
333

A.7 Mollusks

Scientific Name: Bithynia tentaculata

Common Name: Faucet snail

Environmental: High

Socio-Economic: Moderate

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U

• The introduction of B. tentaculata has been linked to extensive mortality of migratory waterbirds in the 

Upper Mississippi River National Wildlife and Fish Refuge in Wisconsin due to its role as a host of the 

trematodes Cyathocotyle bushiensis and Sphaeridiotrema globulus (Herrmann and Sorensen 2009, Sauer 

et al. 2007). Between 2002 and 2006, over 20,000 migratory birds died at this location due to these 

parasites.

• Duck (Anas spp.) mortality in lower Quebec was credited to these two trematodes and their snail host 

(Ménard and Scott 1987), as was the death of 6,000-7,000 scaup (Aythya spp.) over a two month period at 

Lake Winnibigoshish in 2007 (Lawrence et al. 2009).

• A 1997 mass mortality event of over 10,000 birds (particularly American coot, Fulica americana, and lesser 

scaup, Aythya affinis) was reported at Shawano Lake, WI (Cole 2001, Cole and Franson 2006). Bithynia 

tentaculata occurs in this Wisconsin lake, and the deaths were primarily attributed to the presence of 

Leyogonimus polyoon, a third trematode species hosted by B. tentaculata (Cole 2001, Cole and Franson 

2006). 

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Between 1917 and 1968, the species richness of mollusks in Oneida Lake, NY decreased by 15% as the 

faucet snail increased in abundance (Harman 2000). After the introduction of B. tentaculata into the Erie 

Canal, the faucet snail began replacing two pleurocerid species, Elimia virginica and E. livescens (Jokinen 

1992). It is very probable that the faucet snail has particularly impacted pleurocerids due to its higher 

growth rates (Shiro Tashiro and Colman 1982).

• Where the faucet snail has been observed in Lake Champlain, NY, it generally dominates gastropod 

assemblages (VTDEC and NYDEC 2000).
334

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

• Laboratory research on the impact of grazing by B. tentaculata indicated that it can have complex impacts 

on the periphyton community (Burgmer et al. 2010). Through direct and indirect effects, B. tentaculata

grazing contributed to a shift from larger filamentous algae to small prostrate forms, was associated with a 

significant reduction in the biomass of heterotrophic nanoflagellates and ciliates, and was also linked to a 

weak decline in meiofauna biomass (Burgmer et al. 2010).

• Grazing by B. tentaculata, along with another snail species, was correlated with a decline in microalgal 

species richness (but increased evenness) and a significant reduction in the biomass microalgae, 

nanoautrophs, and bacteria (Burgmer et al. 2010).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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 
335

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

Environmental Impact Total 7

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Historically, this species has been known to infest municipal water supplies in abundance (Mills et al. 

1993). The snail also has the potential to be a bio-fouling organism for underwater intakes and in 

swimming areas (VTDEC and NYDEC 2000).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 
336

Unknown U √

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 areas of Wisconsin where the trematode parasites of B. tentaculata are causing large die-offs of 

waterbirds (see Environmental Impact section), these mass mortalities have fueled health concerns among 

waterfowl hunters and increased the difficulty of hunting game (Sauer et al. 2007).

• These mass mortality events have also resulted in restricted recreational access during periods of cleanup

(Cole 2001, Lawrence et al. 2009, Sauer et al. 2007).

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√

• In areas of Wisconsin where the trematode parasites of B. tentaculata are causing large die-offs of 

waterbirds (see Environmental Impact section), these mass mortalities have fueled health concerns among 

waterfowl hunters and increased the difficulty of hunting game (Sauer et al. 2007).

Socio-Economic 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
337

BENEFICIAL EFFECT

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

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

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

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

• The faucet snail has the potential to be a good biomonitor for contaminants such as cadmium, zinc, and 

methylmercury, owing to well-known correlations between environmental concentrations and snail tissue 

concentrations of these toxic compounds (Desy et al. 2000, Flessas et al. 2000).

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 

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, 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 
338

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
339

Scientific Name: Cipangopaludina chinensis malleata

Common Name: Chinese mystery snail

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Like other mollusks, this introduced species may be a vector for the transmission of parasites and diseases.

In the Boston area, C. chinensis is a regular host to the common native parasite Aspidogaster conchicola,

which is a first time record in North America for a gastropod acting as host to this species (Michelson 

1970).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 a mesocosm experiment, the presence of C. chinensis was correlated with substantial decreases in 

abundance and/or biomass of native snails Physa gyrina, Lymnaea stagnalis, and Helisoma trivolvis, which 

the authors primarily attributed to competition for resources (Johnson et al. 2009).

• In a survey of Wisconsin lakes, Solomon et al. (2009) found the abundance of native Lymnaea stagnalis to 

be negatively correlated with the abundance of C. chinensis, suggesting that C. chinensis may be an 

important driver of competition and native snail displacement on the community-scale.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √
340

• Where C. chinensis overlaps with the introduced rusty crayfish, Orconectes rusticus, impacts on native 

populations may be particularly severe. The relatively large and thick shell of C. chinensis reportedly 

enables this species to evade predation by O. rusticus more easily than native snails; thus, the risk of 

predation by O. rusticus remains relatively high while competition with C. chinensis add further pressure 

on native snail survival (Johnson et al. 2009).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• At the community level, C. chinensis presence was correlated with a decline in periphyton levels, 

particularly on the sediment, and an increased nitrogen:phosphorus ratio in the water column. Further 

analysis suggested that higher levels of phosphorous uptake in C. chinensis tissue and reduced 

phosphorous levels in C. chinensis excrement relative to native snails is a plausible explanation for the 

latter observation, which suggests that this species may provide a phosphorous sink in invaded ecosystems 

(Johnson et al. 2009).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

• In a community-scale mesocosm experiment, C. chinensis presence was correlated with a decline in 

periphyton levels, particularly on the sediment (Johnson et al. 2009).

Environmental Impact Total 0

Total Unknowns (U) 5
341

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U√

• Cipangopaludina chinensis is also a known host of parasites in its native range, at least one of which 

(Echinostoma cinetorchis, an intestinal trematode that causes echinostomiasis) is capable of infecting 

humans through ingestion of uncooked snails (Chung and Jung 1999, Graczyk and Fried 1998). However, 

no related cases of infection are currently known from the Great Lakes region. The global significance of 

host activity by C. chinensis in facilitating parasitization of humans is unknown.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

• The Chinese mystery snail has the ability to clog screens of water intake pipes, causing difficulties for 

water treatment plants, but the extent of this occurrence in the Great Lakes is unknown

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture)?
342

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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

BENEFICIAL EFFECT

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

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
343

Not significantly 0 

Unknown U √

• It is known to exist in the aquarium and live food trade (Cordiero 2002, Havel 2010, Karatayev et al. 2009, 

Mackie 2000a, Mills et al. 1993), but the extent of this in the Great Lakes is unknown.

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

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

• While not currently applied in the Great Lakes, Corbicula spp. have the potential to be used as a 

bioindicator for organochlorine pesticides persisting in the environment (Takabe et al. 2011) .

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 

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, 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
344

1 0

0 ≥2 Unknown

1 ≥1
345

Scientific Name: Cipangopaludina japonica

Common Name: Japanese mystery snail

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U√

• In Spot Pond, Massachusetts, the Japanese mystery snail was discovered to be a regular host to the 

common native parasite Aspidogaster conchicola, marking the first record for a gastropod host of this 

species in North America (Michelson 1970).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 
346

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?

Yes, significant effects on human health have already been observed 6
347

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U√

• The Japanese mystery snail is a host to Angiostrongylus cantonensis larvae in Taiwan, a species associated 

with eosinophilic meningitis (Lin and Chen 1980). It is also capable of hosting many other parasites in 

Asia, some of which may infect humans. The extent of this species’ role as a host to parasites in the Great 

Lakes is unknown.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

• Reports of C. chinensis clogging water intakes have emerged, suggesting that closely related C. japonica 

may also be capable of damaging infrastructure, particularly given the high densities which have been 

encountered by fishermen in the past (Wolfert and Hiltunen 1968).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U√

• In the past, this species has been caught in large numbers by commercial fishermen in Sandusky Bay, Lake 

Erie, where two tons catches have sometimes been reported in one seine haul (Wolfert and Hiltunen 1968). 

It could become a similar nuisance in other areas with dense populations (Wolfert and Hiltunen 1968).

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 
348

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) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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√

• Mystery snails (Cipangopaludina spp.) have been popular aquarium species in the U.S., and their role in 

the aquarium/ornamental market is often invoked as the primary explanation of these species’ widespread 

dispersal (Cordiero 2002, Havel 2010, Karatayev et al. 2009, Mackie 2000a, Mills et al. 1993). 

Cipangopaludina spp. have also had presence in live food markets, particularly in Asian markets of the 

Western U.S. (Mackie 2000a). 

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
349

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

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 √

• Research in Japanese rice paddies suggested that the feeding activity of C. japonica, a common rice paddy 

dweller and consumer of bacteria, could be used to assimilate excess sewage from wastewater treatments if 

the sewage were applied as compost (Kurihara and Kadowaki 1988). However, utilizing C. japonicus in 

such a way could pose a danger to consumers of the snail, including humans, due to the potential 

accumulation of heavy metals and other toxic substances (Kurihara and Kadowaki 1988).

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, 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) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
350

Scientific Name: Corbicula fluminea

Common Name: Asian clam

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

• Corbicula fluminea may filter a wider range of food sources at a faster rate than native fresh water 

mussels, which could decrease food availability for other benthic and pelagic species (Atkinson et al. 2010, 

Strayer 1999, Vaughn and Hakencamp 2001).

• Results by Silverman et al. (1997) found that C. fluminea are capable of filter-feeding E. coli and other 

bacteria at a higher rate than some native unionid mussels. A number of experiments analyzing the impact 

of C. fluminea on native bivalves have documented conflicting results, from competitive exclusion to 

coexistence (see Sousa et al. 2005, Strayer 1999).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
351

Yes, and it has caused a loss or alteration of genes that 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Cohen et al. (1984) documented a reduction in phytoplankton abundance by 40-60% in a roughly 7 km 

stretch of the Potomac River, MD, relative to upstream and downstream segments. This was likely due to 

the very high densities of C. fluminea in this stretch (an increase from 1.2 clams/m2 in 1977 to 1,467 

clams/m2 in 1981) and the high filter feeding rates that were observed (Cohen et al. 1984).

• Higher levels of nitrogen, ammonia (NH3), and orthophosphate (PO4) in feces and pseudofeces, as well as 

the chemical releases following C. fluminea summer die-offs, could alter nutrient cycling in freshwater 

systems (Atkinson et al. 2010, Lauritsen and Mozley 1989).

• Microcosm experiments suggest that this clam can increase sediment oxygen uptake, as well as the release 

of soluble reactive phosphorus, ammonium, and nitrate (Zhang et al. 2011).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Cohen et al. (1984) documented a reduction in phytoplankton abundance by 40-60% in a roughly 7 km 

stretch of the Potomac River, MD, relative to upstream and downstream segments. This was likely due to 

the very high densities of C. fluminea in this stretch (an increase from 1.2 clams/m2 in 1977 to 1,467 

clams/m2 in 1981) and the high filter feeding rates that were observed (Cohen et al. 1984).

• Following the introduction of C. fluminea to the Potomac River Estuary, a series of ecosystem-level 

changes appeared to occur, including increased water clarity followed by growth of fish, bird, and 

submerged aquatic plant populations, all of which evidently reversed with the decline of C. fluminea 

populations (Phelps 1994).

• Due to its ability to both filter feed and pedal feed, it can alter the abundance of organic matter in the 

sediment depending on its primary source of food at a given time (Hakencamp and Palmer 1999). 

• Higher levels of nitrogen, ammonia (NH3), and orthophosphate (PO4) in feces and pseudofeces, as well as 
352

the chemical releases following C. fluminea summer die-offs, could alter nutrient cycling in freshwater 

systems (Atkinson et al. 2010, Lauritsen and Mozley 1989)

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

• Large numbers of C. fluminea, either dead or alive, clog water intake pipes, and the cost of removing them 

has been estimated at about a billion dollars each year in the United States (Pimentel et al. 2000).

• Juvenile C. fluminea get carried by water currents into condensers of electricity generating facilities, 

where they attach themselves to the walls via byssus threads, growing and ultimately obstructing the flow 

of water. They can also increase sedimentation rates within pipes and canals (McMahon 2000).

• Several nuclear reactors have had to be closed down temporarily in the United States for the removal of 

Corbicula from the cooling systems (Isom 1986).

• In Ohio and Tennessee where river beds are dredged for sand and gravel for use as aggregation material 

in cement, high densities of C. fluminea have incorporated themselves in the cement, burrowing to the 

surface as the cement starts to set and weakening its structure (Sinclair and Isom 1961). 

Does it negatively affect water quality?
353

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• In Ohio and Tennessee where river beds are dredged for sand and gravel for use as aggregation material 

in cement, the high densities of C. fluminea have incorporated themselves in the cement, burrowing to the 

surface as the cement starts to set and weakening the structure (Sinclair and Isom 1961).

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

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

BENEFICIAL EFFECT
354

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

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

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

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

• While not currently applied in the Great Lakes, Corbicula spp. has the potential to serve as a bioindicator 

for organochloride pesticides in the environment (Takabe et al. 2011).

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 √

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, 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 presence of C. fluminea shells in otherwise soft substrate has been correlated with an increase in 
355

arthropod and mayfly (Caenis spp.) densities (Karatayev et al. 2005, Werner and Rothhaupt 2007, 2008).

• Corbicula fluminea is consumed mainly by fish and crayfish. Outside of the Great Lakes, scientists found 

that several fish species modified their diet to feed on C. fluminea and other molluscan invaders. 

Beneficial Effect 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
356

Scientific Name: Dreissena bugensis

Common Name: Quagga mussel

Environmental: High

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• Quagga mussels accumulate organic pollutants within their tissues to levels more than 300,000 times 

greater than concentrations in the environment, and these pollutants are also found in their pseudofeces 

(Snyder et al. 1997).

• Pollutants can be passed up the food chain, increasing wildlife exposure to organic pollutants, such as 

PCBs and hexachlorobenzine, and potentially mercury (Mueting and Gerstenberger 2010, Richman and 

Somers 2010, Snyder et al. 1997).

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion, potentially due to reductions in phytoplankton abundance (an important food source) or

through the introduction of toxins and pathogens associated with dreissenids and their waste products 

(Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion, potentially due to reductions in phytoplankton abundance (an important food source) or 

through the introduction of toxins and pathogens associated with dreissenids and their waste products 

(Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007).

• Likely correlated to declining late winter phytoplankton blooms and chlorophyll a concentrations in Lake 

Michigan from 2001 to 2008, there was a reported decline in cyclopoid and omnivorous calanoid copepod

populations over this period (Kerfoot et al. 2010).

• Spring phytoplankton biomass and primary production in Lake Michigan decreased 87% and 70%, 

respectively, from 1995-98 to 2007-08 (Fahnenstiel et al. 2010). This could result in increased competition 

among planktivorous species.

Does it alter predator-prey relationships? 
357

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion (Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007). Diporeia is an important prey 

item linking the benthos to higher trophic levels, and it has been suggested that the shift from Diporeia to 

Dreissena has transformed the benthic community into an energy sink which may no longer support the 

upper food web (Nalepa et al. 2009).

• Quagga mussels likely decrease food availability for zooplankton through their rapid filtration of 

phytoplankton, thereby altering the food web.

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U

• In Lake Michigan, the fraction of water column cleared (FC) was measured experimentally for quagga 

mussels in 2007-2008 and determined to exceed the phytoplankton growth rate at depths of 30-50 m, likely 

by a factor of five (Vanderploeg et al. 2010). This excessive filtration is hypothesized to cause a mid-depth 

sink of carbon and phosphorous; this is similar to the nearshore phosphorous shunt caused by zebra 

mussels, except that it occurs at mid-depth levels where quagga mussel densities are high (Vanderploeg et 

al. 2010).

• In Lake Michigan, total phosphorus (TP) and mean chlorophyll a concentrations both markedly fell in 

spring seasons after the expansion of quagga mussels, and TP levels remained low into summer (Mida et 

al. 2010). Dramatic increases in summer silica were initiated in the early 2000s in Lake Huron and in 2004 

in Lake Michigan and seem to be associated with the expansion of quagga mussel populations in the lakes 

at those times (Evans et al. 2011).

• Lake Michigan water transparency, which ranged from 74-85% at deepwater sites in 2001, increased to 

94-96% in 2008 following quagga mussel expansion (Kerfoot et al. 2010).
358

• High water filtration rates and high dreissenid abundances have also lead to the accumulation of 

pseudofeces (Claxton et al. 1998). Through nitrogen and phosphorus remineralization, the production of 

biodeposits may increase and redirect nutrient supply and turnover in colonized areas (Conroy et al. 2005, 

Hecky et al. 2004).

• When high-density dreissenid colonies form, nitrate (NO3

-

) concentrations may significantly increase in the 

interstitial water at the colony base while dissolved oxygen concentrations drop, creating potentially 

detrimental conditions for some benthic organisms (Burks et al. 2002). Concurrently, dreissenid metabolic 

activity may lower the nitrogen:phosphorus ratio in the water column, which (along with selective feeding 

behavior of dreissenids) appears to favor the growth of toxic cyanobacteria (Microcystis spp.) (Bykova et 

al. 2006).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U

• Quagga mussels are filter-feeders and at high abundances remove substantial amounts of phytoplankton 

and suspended particulates from the water. Spring phytoplankton biomass and primary production, which 

can be primarily attributed to diatoms, decreased 87% and 70%, respectively, in Lake Michigan from 

1995-98 to 2007-08 (Fahnenstiel et al. 2010).

• While diatoms previously accounted for >50% of phytoplankton composition at the deep chlorophyll layer, 

they composed less than 5% of it in 2007-08 (Fahnenstiel et al. 2010).

• Conditions in Lake Michigan, especially in the critical late winter to spring season, indicate that the 

southern basin is transforming into a more oligotrophic condition, similar to that of Lake Superior in terms 

of levels of nutrients, chlorophyll, and primary production (Mida et al. 2010).

• Increasing amounts of pseudofeces and biodeposits could also have an impact on multiple trophic levels 

via changes to the physical environment. A current study in Brocton Shoal, Lake Erie, suggests that 

colonization of lakebed areas by dreissenid mussels and the consequent filling of remaining interstitial 

spaces with pseudofeces and fine-grained sediments may significantly eliminate valuable habitat native 

habitat (S. Mackey, pers. comm.). Brocton Shoal, once thought to be an important area for lake trout 

spawning, appears to have diminished suitability as a spawning ground, potentially due to such impacts (S. 

Mackey, pers. comm.).

Environmental Impacts Total 25

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0
359

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• Although D. bugensis lacks the keeled shape that allows D. polymorpha to attach so tenaciously to hard 

substrata, it is able to colonize both hard and soft benthic habitats (Mills et al. 1996). These major 

biofouling organisms can clog water intake structures, such as pipes and screens, thereby reducing 

pumping capabilities for power and water treatment plants and financially impacting industries, 

companies, and communities (Connelly et al. 2007).

• Colonization has occurred at the Hoover, Imperial, Davis, and Parker Dams on the Lower Colorado River, 

causing various degrees of clogging and subsequent expense (Claudi and Prescott 2007a, b).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• The reemergence of nuisance algal species Cladophora in Lake Ontario, Lake Erie, and Lake Michigan has 

been largely attributed to the resulting changes in nutrient cycling and water clarity due to zebra mussels 

(Auer et al. 2010, Hecky et al. 2004). Similar observed effects between zebra and quagga mussel filtration 

suggest that quagga mussels could also contribute to this impact.

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

0 ≥2 Unknown

1 ≥1
360

• The quagga mussel has the potential to cause major costs for dams and the hydropower industry, 

particularly if its westward expansion continues. Colonization has already resulted in clogging and 

subsequent expense at the Hoover, Imperial, Davis, and Parker Dams on the Lower Colorado River 

(Claudi and Prescott 2007a, b).

• Reductions in plankton biomass may cause increased competition, decreased survival and decreased 

biomass of planktivorous fish, including commercially important species.

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

• Recreation-based industries and activities have also been impacted by Dreissena’s biofouling ability; 

docks, breakwalls, buoys, and boats have all been heavily colonized and beaches have been incidentally 

littered with dead shells. The extent of negative impacts on recreation due to quagga mussels’ ability to 

colonize both hard and soft substrates is as of yet unclear.

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 20

Total Unknowns (U) 0

BENEFICIAL EFFECT

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

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
361

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

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

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

• Quagga mussels have been proposed and tested for use as bio-indicators (both in the Great Lakes and 

Western U.S.) due to their ability to accumulate toxins and metals at much higher levels than those found in 

the environment, especially when small environmental levels are difficult, and yet important, to measure 

(Mueting and Gerstenberger 2010, Richman and Somers 2010). For instance, the National Oceanic and 

Atmospheric Administration’s Mussel Watch program has been monitoring contaminants in Great Lakes 

dreissenids since the early 1990s.

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 

• Increased water clarity following dreissenid introduction is perceived as a benefit by some, especially 

business owners and residents on invaded water bodies (Limburg et al. 2010).

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, 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
362

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
363

Scientific Name: Dreissena polymorpha

Common Name: Zebra mussel

Environmental: High

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U

• Biomagnification of polychlorinated biphenyls (PCBs) was observed in Gammarus amphipods associated 

with zebra mussels, indicating concentration of pollutants in zebra mussel feces or pseudofeces can 

transfer to other trophic levels (Bruner et al. 1994).

• Biomagnification of toxic contaminants through the food web is another concern of zebra mussel invasion, 

especially because mussel predation by round goby Neogobius melanostomus has provided a link between 

Dreissena and higher trophic levels (Hanari et al. 2004, Jude et al. 2010).

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion, potentially due to reductions in phytoplankton abundance (an important food source) or

through the introduction of toxins and pathogens associated with dreissenids and their waste products 

(Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007).

• Like other mollusks, D. polymorpha is capable of hosting a variety of parasites, although the parasite load 

varies across its introduced range and appears to be lower in North America (Mastitsky et al. 2010). In 

particular, D. polymorpha acts as an intermediate host of the trematode Bucephalus polymorphus, which 

has caused pathologies and mortalities in cyprinids across parts of Europe (Molloy et al. 1997).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• At a 90% efficiency rate, zebra mussels are much more efficient at filtering small particles than are 

unionids (Noordhuis et al. 1992). Bacteria, which D. polymorpha also tend to filter more quickly than 

native unionids, may represent another important food source (Cotner et al. 1995, Silverman et al. 1996, 

Silverman et al. 1997).

• Zooplankton abundance dropped 55-71% following mussel invasion in Lake Erie, with microzooplankton 

more heavily impacted (MacIsaac et al. 1995). Mean summer biomass of zooplankton decreased from 130 

to 78 mg dry wt. m-3 between 1991 and 1992 in the inner portion of Saginaw Bay. The total biomass of 

zooplankton in the Hudson River declined 70% following mussel invasion, due both to a reduction in large 

zooplankton body size and a reduction in microzooplankton abundance. These effects can be attributed to 
364

reduction of available food (phytoplankton) and direct predation on microzooplankton. 

• Reductions in zooplankton biomass may cause increased competition, decreased survival, and decreased 

biomass of planktivorous fish.

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion, potentially due to reductions in phytoplankton abundance (an important food source) or

through the introduction of toxins and pathogens associated with dreissenids and their waste products 

(Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007).

• Other effects include the extirpation of native unionid clams through epizootic colonization (Baker and 

Hornbach 1997, Schloesser et al. 1996). Zebra mussels restrict valve operation, cause shell deformity, 

smother siphons, compete for food, impair movement, and deposit metabolic waste onto unionid clams.

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)

6 √

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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

• Zooplankton abundance dropped 55-71% following mussel invasion in Lake Erie, with microzooplankton 

more heavily impacted (MacIsaac et al. 1995). Mean summer biomass of zooplankton decreased from 130 

to 78 mg dry wt. m-3 between 1991 and 1992 in the inner portion of Saginaw Bay. The total biomass of 

zooplankton in the Hudson River declined 70% following mussel invasion, due both to a reduction in large 

zooplankton body size and a reduction in microzooplankton abundance. These effects can be attributed to 

reduction of available food (phytoplankton), and direct predation on microzooplankton. 

• Experimental evidence exists that zebra mussels can reduce the growth rate of larval fish through food web 

interactions (Raikow 2004).

• While dreissenids now appear to be a contributing food source to whitefish diet, this shift appears to be less 

energetically profitable to whitefish, whose growth rate has declined following dreissenid invasion despite 

sustained levels of consumption (Pothoven and Madenjian 2008).

• Declines in Diporeia spp., another benthic invertebrate, have been highly correlated with dreissenid 

expansion (Fahnenstiel et al. 2010, Nalepa et al. 2006, Watkins et al. 2007). Diporeia is an important prey 

item linking the benthos to higher trophic levels, and it has been suggested that the shift from Diporeia to 

Dreissena has transformed the benthic community into an energy sink which may no longer support the 

upper food web (Nalepa et al. 2009).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

levels/cycles)?
365

Yes, and it has had a widespread, long term, or severe negative effect on water quality

AND/OR

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U

• Diatom abundance declined 82-91%, and transparency as measured by Secchi depth increased by 100% 

during the first years of the invasion in Lake Erie (Holland 1993).

• In Lake Huron’s Saginaw Bay, sampling stations with high zebra mussel populations experienced a 60-

70% drop in chlorophyll a and doubling of Secchi depth (Fahnenstiel et al. 1993). Phytoplankton biomass 

declined 85% following mussel invasion in the Hudson River (Caraco et al. 1997). 

• Microcystis became a prevalent alga in Saginaw Bay, Lake Huron following the invasion of zebra mussels. 

The introduction appeared to spur a number of other changes to the phytoplankton community as well, 

including a shift from shade-tolerant species to light-tolerant species (Fishman et al. 2010). This study, 

along with others, indicates that zebra mussels can have a significant effect on nutrient cycling in invaded 

ecosystems.

• Zebra mussels can direct phosphorous and other nutrients to those nearshore areas inhabited by mussels 

and retain them there, while offshore regions suffer from declining nutrient levels and often become 

mesotrophic or oligotrophic (Hecky et al. 2004).

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U

• In Lake Erie, the rate of biosedimentation through pseudofeces production was very high (28mg/cm2 day at 

a density of 1180 individuals/m2) under turbid conditions, lending support to the hypothesis that zebra 

mussels are responsible for increased water clarity observed since mussel introduction (Klerks et al. 1996). 

• Increased water clarity allows light to penetrate further, potentially promoting macrophyte populations 

(Scheffer et al. 1993, Skubinna et al. 1995).

• Increasing amounts of pseudofeces and biodeposits could also have an impact on multiple trophic levels 

via changes to the physical environment. A current study in Brocton Shoal, Lake Erie, suggests that 

colonization of lakebed areas by dreissenid mussels and the consequent filling of remaining interstitial 

spaces with pseudofeces and fine-grained sediments may significantly eliminate valuable habitat native 

habitat (S. Mackey, pers. comm.). Brocton Shoal, once thought to be an important area for lake trout 

spawning, appears to have diminished suitability as a spawning ground, potentially due to such impacts (S. 

Mackey, pers. comm.).

Environmental Impacts Total 30

Total Unknowns (U) 0
366

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• Zebra mussels are notorious for their biofouling capabilities—colonization of water supply pipes of 

hydroelectric and nuclear power plants, public water supply plants, and industrial facilities. When 

inhabiting pipes, they tend to constrict water flow, thereby reducing the intake in heat exchangers, 

condensers, fire-fighting equipment, and air conditioning and cooling systems.

• Zebra mussel densities have been as high as 700,000/m2 at one power plant in Michigan and have reduced 

pipe diameters by as much as two-thirds at some water treatment facilities (Griffiths et al. 1991).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• The reemergence of nuisance algal species Cladophora in Lake Ontario, Lake Erie, and Lake Michigan 

following the establishment of zebra mussels has been largely attributed to the resulting changes in nutrient 

cycling and water clarity (Auer et al. 2010, Hecky et al. 2004). Residents and business owners on Lake 

Ontario have attributed decreases in revenue or property values to these excessive blooms following zebra 

mussel invasion (Limburg et al. 2010).

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
367

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

• Direct economic costs have resulted from the invasion of zebra mussels in the form of maintenance and 

repair of power plants, industrial facilities, and other businesses, as well as research, monitoring, and 

control. A wide variety of estimations have been made regarding zebra mussel-related expenses, ranging 

from $92,000 per hydroelectric plant per year to $6.5 billion in total costs over 10 years (Lovell et al. 

2006).

• Reductions in zooplankton biomass may cause increased competition, decreased survival, and decreased 

biomass of planktivorous fish, including commercially important species.

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

• Navigational and recreational boating can be affected by increased drag from attached mussels. Small 

mussels can get into engine cooling systems causing overheating and damage. Navigational buoys have 

been sunk under the weight of attached zebra mussels. Fishing gear can be fouled if left in the water for 

long periods. Deterioration of dock pilings has increased when they are encrusted with zebra mussels. 

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

• Residents and business owners on Lake Ontario have attributed decreases in revenue or property values to 

excessive blooms of Cladophora following zebra mussel invasion (Limburg et al. 2010).

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
368

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

• Zebra mussels have also been used in biomonitoring of contaminants (Mackie et al. 1989).

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 

• Zebra mussels removed metals from the water column of Lake Erie and deposited it to the bottom at high 

rates (Klerks et al. 1996).

• Increased water clarity following zebra mussel introduction is perceived as a benefit by some, especially 

business owners and residents on invaded water bodies (Limburg et al. 2010)

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, or commercially valuable)?
369

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

• Experimental studies have shown that zebra mussels generally increase benthic macroinvertebrate 

densities, sometimes by more than 10-fold (Botts et al. 1996, Ricciardi et al. 1997, Ward and Ricciardi 

2007). Some benthic fishes may benefit from the increased food resource.

• Several species of native fish may prey on zebra mussels in varying degrees, including lake whitefish 

(Madenjian et al. 2010, Rennie et al. 2009), freshwater drum, pumpkinseed, yellow perch, and rock bass 

among others (Watzin et al. 2008).

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
370

Scientific Name: Elimia virginica

Common Name: Piedmont elimia

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Elimia virginica is a known host of trematode parasites, including Philophthalmus megalurus and 

Sphaeridiotrema globulus (Huffman and Fried 1983, Smith 1980). In one New Jersey Lake, multiple mute 

swan (Cygnus olor) deaths appeared to be caused by S. globulus hosted in E. virginica at an infection rate 

of roughly 50% (Huffman and Fried 1983).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 √
371

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U

• During glaciation, the Alleghenian Divide geographically isolated congeners E. virginica and E. 

livescens—the former was only found in Atlantic Slope drainages, while the latter was only found in 

Interior basin drainages (Bianchi et al. 1994). There is recent evidence for hybridization and introgression 

between the species, whose populations were brought into contact with the opening of the Erie Canal 

(Bianchi et al. 1994). Hybridization and introgression have the potential to jeopardize the genetic integrity 

of a species, especially when the population is already small.

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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
372

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
373

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

BENEFICIAL EFFECT

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

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

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

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
374

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 

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, 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
375

Scientific Name: Gillia altilis

Common Name: Buffalo pebblesnail

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √
376

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
377

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
378

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
379

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, 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
380

Scientific Name: Lasmigona subviridis

Common Name: Green floater

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

• Given the limited distribution of L. subviridis, lack of evidence of spread, high densities, or remarkable 

ecological behaviors, as well as its threatened status in its own native region, it appears unlikely that L. 

subviridis is capable of having a significant impact via competition.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 

• Given the limited distribution of L. subviridis, lack of evidence of spread, high densities, or remarkable 

ecological behaviors, as well as its threatened status in its own native region, it appears unlikely that L. 

subviridis is capable of having a significant impact via food web effects.

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 6
381

or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
382

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
383

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

BENEFICIAL EFFECT

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

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

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

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
384

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 

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, 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
385

Scientific Name: Pisidium amnicum

Common Name: Greater European peaclam

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
386

Unknown U√

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
387

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
388

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
389

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, 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
390

Scientific Name: Pisidium henslowanum

Common Name: Henslow peaclam

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Recent sampling in Lake Superior indicates that P. henslowanum has a greater abundance in the DuluthSuperior Harbor area than any species of native peaclam (Pisidium spp.), suggesting that P. henslowanum

may possess some invasive trait(s) or compete with native species (Mackie 2000b, Trebitz et al. 2010).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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 
391

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6
392

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
393

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 √
394

Unknown U 

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, 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
395

Scientific Name: Pisidium moitessierianum

Common Name: Pygmy peaclam

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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√

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0
396

Unknown U√

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
397

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
398

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
399

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, 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
400

Scientific Name: Pisidium supinum

Common Name: Humpbacked peaclam

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 
401

Unknown U √

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1
402

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
403

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 
404

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, 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
405

Scientific Name: Potamopyrgus antipodarum

Common Name: New Zealand mudsnail

Environmental: Moderate

Socio-Economic: Unknown

Beneficial: Low

Comments:

Most impacts thus far have been documented in the Western U.S.; across studies, results are often conflicting.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Potamopyrgus antipodarum is capable of serving as a host for a number of trematode parasites, although 

the extent of occurrence and consequences in its nonindigenous range is largely unknown (see Morley 

2008).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

• Abundant populations of introduced P. antipodarum may outcompete other grazers for food resources and 

inhibit colonization by other macroinvertebrates and native snails (Kerans et al. 2005).

• In one Australian stream, increasing densities of P. antipodarum were positively correlated with density 

and species richness of native invertebrates, possibly due to coprophagy (ingestion of the snail's feces) 

(Schreiber et al. 2002). However, in Europe, P. antipodarum has caused declines in species richness and 

abundance of native snails in constructed ponds (Strzelec 2005).

• A colonization experiment in Yellowstone National Park found a negative relationship between the 

abundance of P. antipodarum colonizers and native macroinvertebrate colonizers on stone tiles placed in 

several rivers, suggesting that P. antipodarum may interfere with the colonization activity of native species 

(Kerans et al. 2005). However, across sites, Kerans et al. (2005) did not find significant negative 

correlations between the densities of P. antipodarum and native macroinvertebrate densities, and overall 

impacts in this area remain largely unknown.

• Stable isotope analysis indicated that the diet of P. antipodarum overlaps with the diets of coexisting native 

invertebrates in the Columbia River Estuary; however, the authors also found that P. antipodarum foraging 

was decreased in the presence of native Gnorimosphaeroma insulare, while foraging of G. insulare was 

unaffected by interspecific competition (Brenneis et al. 2010).

• Cross et al. (2010) did not detect any impact on native species biomass following the invasion of P. 
406

antiodarum in Glen Canyon of the Colorado River. In contrast, field surveys below the Flaming Gorge 

Dam, documented an overall decrease in total invertebrate abundance following P. antipodarum invasion 

(Vinson et al. 2007). Interestingly, some invertebrate groups that were not affected by P. antipodarum

overall were reduced in the presence of P. antipodarum in certain habitats (e.g., amphipods in eddies and 

mayflies in runs/riffles) (Vinson et al. 2007).

• In an enclosure competition experiment in Branbury Springs, ID, Richards (2004) found that resourcerelated competitive interactions likely have adverse effects on growth rates of a threatened native snail, 

Taylorconcha serpenticola, at P. antipodarum densities above 4,000 m-2. Riley et al. (2008) also found that 

P. antipodarum was a superior competitor to a native snail Pyrgulopsis robusta in Yellowstone National 

Park, documenting a negative correlation between their growth rates. Interestingly, analysis indicated that 

both species consumed similar amounts of algal resources, discrediting resource acquisition ability as a 

mechanism for interspecific competition. The authors suggest that adverse impacts on P. robusta could 

stem from lower maintenance costs or more efficient resource conversion within P. antipodarum (Riley et 

al. 2008).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 P. antipodarum has been documented as a food source for recreationally valuable salmonids 

(Bersine et al. 2008, Vinson et al. 2007), its lack of digestibility could be detrimental to its predators 

(Vinson and Baker 2008).Vinson and Baker (2008) found that 53.8% of New Zealand mudsnails passed 

through the digestive system of rainbow trout alive, with only 8.5% of snails estimated to have been fully 

digested. Furthermore, rainbow trout that were fed on a diet of P. antipodarum lost 0.14-0.48% of their 

initial weight per day.

• Unsuitability of P. antipodarum as a food source and its potential competitive effects within lower trophic 

levels may affect food availability and alter food web processes in invaded systems (Kerans et al. 2005).

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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 1 √
407

have been mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U

• In geothermal streams of the western U.S., P. antipodarum can reach densities of 300,000 snails/m2 and 

has been shown to alter nutrient (nitrogen and carbon) flows, consume a large portion of daily gross 

primary production (GPP), and account for most of the invertebrate production (Hall et al. 2003, Hall et 

al. 2006). Potamopyrgus antipodarum also appeared to play a large role in nitrogen cycling through 

extensive ammonium excretion (Hall et al. 2006).

• A study by Arango et al. (2009) suggested that by selectively grazing on non-nitrogen-fixing components of 

the algal assembly, P. antipodarum was able to increase nitrogen fixation in a high-productivity stream.

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

• In geothermal streams of the western U.S., P. antipodarum can reach densities of 300,000 snails/m2 and 

consume a large portion of daily gross primary production (GPP) and account for most of the invertebrate 

production (Hall et al. 2003, Hall et al. 2006). P. antipodarum also appeared to play a large role in 

nitrogen cycling through extensive ammonium excretion (Hall et al. 2006).

• A study by Arango et al. (2009) found that P. antipodarum altered periphyton community composition over 

a short time period by selective feeding in the high-productivity stream.

Environmental Impact Total 2

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

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)?
408

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

• Densities have reached 500,000 individuals per square meter in a Snake River tributary of Idaho (Richards 

et al. 2001); a species this prolific has potential to be a biofouler at facilities drawing from infested waters. 

Historically, P. antipodarum has both blocked and been distributed through water pipes in Australia 

(Ponder 1988).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 √

• If P. antipodarum has adverse impacts on food web interactions in invaded ecosystems (see above), it is 

possible that certain recreationally or commercially valuable species such as rainbow trout (Oncorhynchus 

mykiss) and brown trout (Salmo trutta) could be negatively impacted at high snail densities (Proctor et al. 

2007).

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
409

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) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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 √
410

Not significantly 0 

Unknown U

• Partially due to their relatively high tolerance of environmental stressors, P. antipodarum is often used as a 

research organism to test novel experimental/analytical techniques (e.g., Myrick 2009, Schmitt et al. 

2010a) or to test the physiological effects of toxic chemicals an aquatic fauna—particularly effects on the 

endocrine system (e.g., Alonso and Camargo 2009, Gust et al. 2009, Schmitt et al. 2010b) 

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 

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, 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
411

Scientific Name: Radix auricularia

Common Name: European ear snail

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

• In Europe and Asia, R. auricularia is a host to such parasites as Echinoparyphium recurvatum (Sohn et al. 

2002), Trichobilharzia franki (Ferte et al. 2005), T. ocellata (Zbikowska 2004), T. szidati (Kolarova et al. 

1997), Clinostomum complanatum (Chung et al. 1998), Mantoscyphidia radixi (Boshko 1993), and 

Orientobilharzia turkestanica (Tang et al. 1990), some of which may also infect birds, mammals, and 

amphibians (Soldánová et al. 2010).

• In one German survey, 20% of captured R. auricularia were infected with trematode parasites (Soldánová 

et al. 2010).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
412

Yes, and it has caused a loss or alteration of genes that 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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
413

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

• Radix auricularia is a documented host of a number of parasites that cause dermatitis known as 

“swimmer’s itch,” including Orientobilharzia turkestanica (Majoros et al. 2010, Tang et al. 1990), 

Trichobilharzia franki (Ferte et al. 2005), and T. ocellata (Zbikowska 2004). Cases related to R. auricularia 

have been documented in Europe (Zbikowska 2004).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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
414

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

BENEFICIAL EFFECT

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

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

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

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 1
415

OR

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U

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 

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, 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
416

Scientific Name: Sphaerium corneum

Common Name: European fingernail clam

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• In North America, Sphaerium corneum hosts such digenean species as Crepidostomum transmarinum, 

Bunodera lucipercae, and Phyllodistomum simile, which also parasitize fish, including salmonids. These 

species have been recorded from the Ottawa River, which flows into the St. Lawrence River in Canada 

(Mackie 1976, Mackie 2000b).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √

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 

or extinction of one or more native species

6

Yes, some genetic effects have been observed, but consequences have been limited to the individual 1 
417

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

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

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)?
418

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U√

• Sphaerium corneum shells have reportedly caused blockages in one water supply plant in Britain, although 

this type of problem has not been reported frequently (Clarke 1987).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
419

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

BENEFICIAL EFFECT

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

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

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

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

• Sphaerium corneum has been used frequently to conduct research on accumulation rates and metabolism 

of toxic chemicals and contaminants (e.g., Borchert et al. 1997, Penttinen et al. 1996, Verrengia Guerrero 

et al. 2002).
420

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 

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, 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 

• In Lake Ontario and Cayuga Lake (part of the Lake Ontario drainage in New York state), S. corneum has 

been recorded as a host to the oligochaete Chaetogaster limnaei limnaei. This oligochaete is probably quite 

widespread in North America, where it is typically a commensal of native snails, some other native 

Sphaerium spp., and at least one native limpet species (Barbour 1977).

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
421

Scientific Name: Valvata piscinalis

Common Name: European stream valvata

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

• Valvata piscinalis could act as a vector of parasites, including the parasitic trematode flukes

Echinoparyphium recurvatum and E. mordwilokoi, which it has hosted in its native range (Evans et al. 

1981, Grabda-Kazubska and Kiseliene 1991, McCarthy 1990).

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral

changes) 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 √

• This species has the potential to compete with native gastropods for food and space (Grigorovich et al. 

2005). Unlike native gastropods, it is capable of filter feeding on suspended food items in eutrophic 

conditions, which could conceivably allow it to become competitively dominant in such conditions 

(Grigorovich et al. 2005).

• When V. piscinalis was introduced to Oneida Lake, native gastropods (in particular, hydrobiid snails) 

appeared to decrease in abundance (Grigorovich et al. 2005), possibly due to competition.

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 √
422

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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
423

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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 6
424

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

BENEFICIAL EFFECT

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

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

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

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 √
425

Unknown U

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 

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, 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
426

Scientific Name: Viviparus georgianus

Common Name: Banded mystery snail

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it outcompete native species for available resources (e.g., habitat, food, nutrients, light)?

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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 √

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

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 banded mystery snail may prey on fish embryos. Viviparus georgianus has been shown to significantly 

reduce survival of largemouth bass eggs in guarded nests both in the laboratory and in ponds, and may 

contribute to high incubation mortality seen in natural field settings (Eckblad and Shealy 1972).

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 

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 
427

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6
428

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
429

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

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

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 √
430

Unknown U 

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, 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 

• Anecdotal evidence suggests that mallard ducks are adapting to foraging on this species in Lake George, 

New York.

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
431

A.8 Plants

Scientific Name: Agrostis gigantea

Common Name: Retop

Environmental: Unknown

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

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√

Agrostis gigantea exhibits aggressive reproductive characters and is reportedly very competitive with native species 

(CNPS 2002). It should not be introduced if native revegetation is sought (Tilley et al. 2010).

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 √

Redtop provides a new food source for some grazers. However, Dugger et al. (2004) found that rabbit density was 

lower in redtop-dominated habitat relative to natural areas with taller and denser vegetation, probably due to 

relatively reduced cover and food availability in redtop areas. Additionally, one foraging study of introduced Rocky 
432

Mountain elk (Cervus elaphsu nelsoni) in the French River region (Ontario) suggested that A. gigantea is not a 

significant forage species for elk populations in the Great Lakes region (Jost et al. 1999).

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U√

Environmental Impact Total 0

Total Unknowns (U) 4

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown
433

1 ≥1
434

Scientific Name: Alnus glutinosa

Common Name: Black alder, European alder

Environmental: Moderate

Socio-Economic: Low 

Beneficial: Unknown 

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

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 

Black alder is an ornamental species, but may be discouraged for use in natural areas due to its reported ability to 

form monocultures (Eckel 2003, NatureServe 2010).

With the potential to dominate wetland communities, the Ontario Invasive Plants Working Group has labeled A. 

glutinosa as a top priority for management (Havinga 2000).

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 

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 6
435

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Alnus glutinosa hybridizes readily with many other alders; three of these species are native to the US (Funk 1990, 

USDANRCS n.d.). Two of the species,Alnus rhombifolia Nutt. and Alnus rubra Bong. are native to the west coast. A 

portion of the native range for Alnus serrulate (AIton) Willd. is in the Great Lakes; it can be found in Illinois, 

Indiana, Ohio, Pennsylvania, and New York (USDANRCS n.d.).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Black alder leaf litter easily leaches nitrogen and water-soluble organic substances (Funk 1990).

Black alder could further impact water courses by de-oxygenating the water, shading out other species, and 

degrading habitat. Black alder’s dense root system is capable of trapping sediment and subsequently altering water 

flow in wetland ecosystems (Funk 1990).

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Alnus glutinosa is associated with number of nitrogen-fixing actinomycetes fungi that directly increase soil nitrogen 

concentrations (Hall et al. 1979). Its leaves are also nitrogen-rich and have been shown to significantly increase 

nitrogen concentrations via leaf litter leaching (Mikola 1958).

Black alder is a pioneer species capable of modifying the environment by colonizing exposed soils, fixing nitrogen, 

and producing copious amounts of litter (Funk 1990, USDANRCS 2006).

Results from a study conducted by Vogel et al. (1997) suggest that as atmospheric carbon dioxide concentration 

increases, nitrogen fixing species (such as black alder) will be able to fix more atmospheric nitrogen. This will lead 

to an increase in nitrogen concentration (above current fixation rates) in leaves and, ultimately, in soils via leaf 

litter decomposition (Vogel et al. 1997).

Areas planted with black alder at a mine restoration site in Kentucky had twice as much leaf litter and higher 

concentrations of soluble salts than areas without black alder; this leaf litter also resulted in significantly more 

acidic spring soil (Plass 1977).
436

Environmental Impact Total 3

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

While black alder does have small scale environmental impacts on water quality (see Environment Impact section), 

these impacts are not significant to recreational, commercial or other human uses of water. 

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 
437

Not significantly 0 √

Unknown U

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

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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√

While it is not considered a commercially-valuable hardwood, Alnus glutinosa is kept by some US nurseries to meet 

the demand for use in orchards (as a windbreak) and at mine revegetation sites (Mikola 1958, USDA NRCS 2006).

The wood may be used for carving and the leaves for medicinal purposes (Mills et al. 1993).
438

Black alder acts as a significant source of nitrogen, which typically becomes available for other species and has 

been shown to increase growth in nearby trees (Funk 1990, Mikola 1958, Plass 1977). For this reason, black alder 

is sometimes recommended as a nurse crop (a species interplanted with the species of interest in order to assist in 

its growth) for numerous hardwood tree species (Bohanek and Groninger 2005, Plass 1977, Shepperd and Jones 

1985, Vogel 1981).

When interplanted on coal mine reclamation sites, black alder’s presence was associated with the doubling in size 

of adjacent yellow-poplar (Liriodendron tulipifera), white ash (Fraxinus americana), and American sycamore

(Plantanus occidentalis) (Vogel 1981). In a seven year study of shale mining reclamation sites in Estonia, black 

alder stands showed high survival and productivity rates, as well as reduced soil pH and phosphrous concentration 

(Kuznetsova et al. 2011).

Potential for commercial benefits exists; the extent of applicability to the Great Lakes region is unknown.

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0√

Unknown U

The wood may be used for carving and the leaves for medicinal purposes (Mills et al. 1993).

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 a supercritical carbon dioxide extraction of A. glutinosa, β-sitosterol and eleven pentacyclic triterpenes were 

identified (Felföldi-Gáva et al. 2012). These compounds have a variety of potential pharmacological applications, 

including stunting cancer tumor growth and protecting against the side effects of chemotherapy and radiation 

treatment (Laszvzyk 2009, MDidea 2010). This group of compounds has also been found to have anti-inflammatory, 

antioxidant, antimicrobial, and antiviral properties, as well as cardiovascular benefits (MDidea 2010, Patočka 

2003). One identified compound, betulinic acid, has been demonstrated to have antiviral properties against HIV 

(DeClercq 2000).

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 

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, 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 √
439

Due to its ability to colonize acidic soils and provide a source of nitrogen, black alder can aid in the restoration of 

disturbed sites and spoil banks (Funk 1990).

In an evaluation of the soil remediation ability of trees, Chodak and Niklińska (2010) found that A. glutinosa caused 

the largest accumulation of organic carbon and total nitrogen of all examined tree species, but was also associated 

with the most acidic soils.

Black alder may provide food for deer, rabbits, hares, and several bird species. Black alder seeds are released from 

cones throughout the winter, potentially benefiting seed-eating birds (Funk 1990).

Beneficial Effect Total 1

Total Unknowns (U) 2

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
440

Scientific Name: Alopecurus geniculatus L.

Common Name: Water foxtail, marsh foxtail, floating foxtail

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

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 areas outside of the Great Lakes, Kalusová et al. (2009) found that A. geniculatus abundance increased with 

increasing soil phosphorus levels and speculated that it could be a competitive grass species in nutrient-rich soils. 

However, Peeters (2004) classified A. geniculatus as a generally poor competitor.

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 √

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
441

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Although it is capable of hybridizing with the native shortawn foxtail (Alopecurus aequalis), only sterile offspring 

are produced (Klein 2011).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

It may dominate wet microsites, and if infestations reach sufficiently high densities, it could alter community 

structure (layers) in invaded wet areas (Klein 2011, Peeters 2004).

It is typically found in wet, nutrient-rich soils and is described as moderately to very demanding of soil nutrients 

(Peeters 2004). This suggests that A. geniculatus could influence nutrient availability or soil chemistry (Klein 2011, 

Peeters 2004). 

Environmental Impact Total 1

Total Unknowns (U) 3

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
442

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
443

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0√

Unknown U

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

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
444

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 

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, 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) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
445

Scientific Name: Butomus umbellatus

Common Name: Flowering rush

Environmental: Moderate

Socio-Economic: Unknown 

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

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

Butomus umbellatus forms dense stands in southern Lake Champlain, where it appears to displace native species 

(Marsden and Hauser 2009).

Butomus umbellatus can displace native riparian vegetation via competition and could diminish native biodiversity 

as a result (MPLP 2006).

At about 40% of the sites at which it was found on the St. Lawrence River, B. umbellatus made up more than 50% of 

the total species cover, suggesting that it is capable of dominating wetland sites (Lavoie et al. 2003). However, 

Shannon diversity indices and number of native plant species were still greater at sampling stations with B. 

umbellatus than at stations with the harmful exotic grasses Phalaris arundinacea and Phragmites australis (Lavoie et

al. 2003). Lavoie et al. (2003) speculated that even the densest populations of flowering rush may leave some 

available space for native species as a result of its particular growth form.

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
446

Unknown U √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

It is capable of forming dense mats which could affect the availability of light, nutrients, and dissolved gasses in 

colonized waters (MPLP 2006).

Infestations could also result in increased water temperatures and altered nutrient flows and/or sedimentation rates. 

Flowering rush has resulted the complete obstruction of open water, reduced water flow and increased 

sedimentation in Montana and southwest Idaho (Rice and Dupuis 2009).

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

Infestations could result in increased water temperatures and altered nutrient flows and/or sedimentation rates 

(Rice and Dupuis 2009).

In the western U.S., emergent monocultures have colonized and reduced areas of open water; although scientific 

study is limited, these invasions have reportedly reduced water flow in canals and modified the physical structure of 

previously unvegetated localities (Rice and Dupuis 2009).

Environmental Impact Total 3

Total Unknowns (U) 1
447

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U √

Concerns have arisen in the western U.S. regarding the role of B. umbellatus populations as an ideal habitat for the 

great pond snail (Lymnaea stagnalis), an intermediate host of a trematode (Trichobilharzia ocellata) responsible for 

swimmer’s itch (Rice and Dupuis 2009).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U 
448

Wild rice (Zizania aquatic) has been identified as a species potentially threatened by the spread of B. umbellatus in 

the wetlands of the northern United States and Canada (Lui et al. 2005, MPLP 2006). Reduction in wild rice 

harvests could affect indigenous people who live in the area (B. Ranta pers. comm. to Lui 2001).

In the Aberdeen-Springfield canal system (ID), B. umbellatus has colonized an estimated 150 miles of the 300 mile 

main canal, threatening water availability for potato and cash crops and requiring removal every 2 or 3 years. Full 

management of flowering rush in this canal system could raise costs to farmer shareholders by as much as 8% (Rice 

and Dupuis 2009). 

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

Butomus umbellatus can obstruct irrigation canals and interfere with industrial shoreline uses, boat traffic, and 

other recreational activities (Eckert et al. 2000, MPLP 2006). 

Flathead Lake (MT) has been infested by monocultures of flowering rush that have inhibited boat passage and 

reduced open water availability for swimming and fishing (Rice and Dupuis 2009). 

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√

Stands of B. umbellatus can become thick and undesirable, even in its native range (Hroudová et al. 1996).

Socio-Economic Impact Total 1

Total Unknowns (U) 2

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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
449

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

It has been used as an aquatic ornamental plant, though it is now prohibited in several Great Lakes states (GLPANS 

2008, Les and Mehrhoff 1999).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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 

The roots and seeds of B. umbellatus are edible, and the plant has been investigated for some medicinal uses (e.g., 

anti-microbial properties were tested but not discovered) (Özbay and Alim 2009).

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 

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, 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 √

Muskrats use parts of the plant for habitat, and ducks reportedly graze on B. umbellatus in its native range 

(potentially offering some control of the plant) (Hroudová et al. 1996).

Flowering rush could provide structural habitat for some fish species, particularly those which depend on 

vegetation for spawning (Rice and Dupuis 2009). 

Beneficial Effect Total 1

Total Unknowns (U) 1

Scoring

Score # U’s Impact
450

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
451

Scientific Name: Cabomba caroliniana Gray

Common Name: Carolina fanwort

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

Cabomba caroliniana is an extremely persistent and competitive plant, growing quickly and crowding out other 

vegetation (WI DNR 2012, Wilson et al. 2007).

Populations of C. caroliniana readily form dense mats that block sunlight penetration to lower water depths and 

shade out germinating seeds or propagules (ENSR International 2005, Forest Health Staff 2006 Wilson et al. 2007).

After an analysis of invasive species by the U.S. Army Corps of Engineers, the predicted expansion of C. caroliniana 

was so extensive that this species could pose a severe threat to ecosystems in Minnesota (Madsen 1999). Warmer 

winter temperatures and lower water levels may aide in the continued northward expansion of C. caroliniana 

(Hudon and Carignan 2008). 

Cabomba caroliniana has formed monocultures in Kasshabog Lake, Ontario (Hosgsden et al. 2007 Wilson et al. 

2007). The main difference between native macrophyte beds and beds of C. caroliniana in this location is 

significantly reduced light penetration (Hogsden et al. 2007). 

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)

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 
452

Dense stands of C. caroliniana disrupts fish habitat and replaces native foods sources; which can alter 

predator/prey relationships among the fish populations (ENSR International 2005, OISAP 2005, PA DCNR 2011, 

Program 2013).

Morrison and Hay (2011) found that in response to direct feeding activity, C. caroliniana is capable of inducing a 

chemical defense to suppress herbivory. 

Cabomba caroliniana extracts also inhibited growth of 5 different microbes by 20-90%, suggesting that C. 

caroliniana has an anti-microbial defense at feeding scar sites (Morrison and Hay 2011). 

Due to its ability to induce a chemical defense, the establishment of C. caroliniana could have implications for 

herbivore fitness and trophic interactions, as well as important microbial activities (Morrison and Hay 2011). 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Large infestations can affect the oxygen concentrations, pH, and organic content of the nearby water and soil 

(ENSR International 2005, PADCNR 2011).

Furthermore, dieback and decomposition could alter nutrient cycling, potentially reducing dissolved oxygen levels 

and increasing manganese levels (Wilson et al. 2007).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Cabomba caroliniana mats can trap detritus and increase sedimentation which could alter the hydrology or even 

clog freshwater streams and drainage canals (ENSR International 2005, Forest Health Staff 2006, U.S. EPA 2008). 

Environmental Impact Total 4
453

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dense mats of C. caroliniana clog streams, drainage canals, and drinking water intakes and interferes with 

agricultural water uses (WI DNR 2012). 

Cabomba caroliniana is capable of significantly reducing water storage capacity and tainting/discoloring drinking 

water supplies, potentially increasing water treatment costs (Lui et al. 2010).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

1 √
454

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U 

If C. caroliniana spreads from Kasshabog Lake to the Trent-Severn Waterway and Great Lakes system, power 

generation, aquaculture, and other water-based industries could be impacted (Wilson et al. 2007).

Limitations on water uses can negatively impact real estate values (ENSR International 2005). 

An estimated $500,000 a year was spent on control of C. caroliniana in Australia as of 2003 (ADEH 2003, Schooler 

et al. 2006). 

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 

Cabomba caroliniana's dense mass of underwater leaves and stems provide a tangling hazard for swimmers, boats, 

fishing lines, and other recreational water users (Ensbey and Oosterhout 2010, Schooler et al. 2006, Wilson et al. 

2007).

At Kasshabog Lake, Ontario, C. caroliniana has become a nuisance for residents and recreational users, 

discouraging swimming and boating... (Wilson et al. 2007). 

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 

Infestations of this species can cause the water to become stagnant will can cause it to become dark and foulsmelling; ultimately reducing the aesthetic value (Ensbey and Oosterhout 2010).

At Kasshabog Lake, Ontario, C. caroliniana has reportedly affected the aesthetic value of shoreline property (Wilson 

et al. 2007). 

Socio-Economic 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

BENEFICIAL EFFECT

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 
455

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 

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

Because of its attractive appearance and its ability to grow quickly, C. caroliniana has been a commerciallyimportant plant in the aquarium trade worldwide (Wilson et al. 2007).

Rixon et al. (2005) documented its presence in 20% of investigated aquarium stores in the Great Lakes region, while 

Cohen et al. (2007) reported C. caroliniana as one of the top 10 plants in the Montreal aquarium trade.

Additionally, C. caroliniana was one of the most popular aquatic plants among surveyed aquarium owners in 

Canada (Marson et al. 2009). 

However, C. caroliniana is also restricted or prohibited in some Great Lakes states (GLPANS 2008).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Preliminary research indicated that C. caroliniana plant matter that is mechanically harvested for control purposes 

could be anaerobically digested to produce and harness methane-rich gas for energy purposes (O'Sullivan et al. 

2010).

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 

Cabomba caroliniana is capable of sequestering lead and may be useful in reclamation efforts (Mikulyuk and Nault 

2011).

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, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6 
456

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 

Unknown U √

While the composition of algae and macroinvertebrate communities were similar between native macrophyte and C. 

caroliniana beds in Kasshabog Lake, both were more abundant in C. caroliniana beds, potentially because its growth 

morphology provided more favorable structure for habitat (Hogsden et al. 2007). 

Relative to native macrophytes, its ecological value as a source of food or habitat for wildlife is unclear (Wilson et 

al. 2007). 

However, in some instances C. caroliniana may provide cover for macroinvertbrates and spawning ground for fish 

(Hamel 2013, Tilt 2013).

Beneficial Effect 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
457

Scientific Name: Carex acutiformis

Common Name: Swamp sedge, lesser pond sedge, European lake sedge

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 1982, C. acutiformis was observed forming a near monoculture around the entirety of St. Joseph Lake, South 

Bend, IN.

Carex acutiformis was discovered dominating a 6-acre open marsh area in the Stony Swamp Conservation Area 

near Ottawa, ON, where it co-existed with native trees but had displaced nearly all other native plants in both open 

water and some relatively dry areas (Catling and Kostiuk 2003).

This species may be a very serious threat to native vegetation on a local geographic scale due to its ability to spread 

rapidly via vegetative growth and out-compete native species for nutrients and light (Catling and Kostiuk 2003, A. 

Reznicek, pers. comm.).

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 √
458

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

As of 1992, a total of 253 Carex hybrids had been reported in North America. This indicates that this genus is highly 

capable of hybridization, and invasive species, such as C. acutiformis, may be a genetic threat to native sedge 

species (Cayouette and Catling 1992).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

The decomposition of cellulose in C. acutiformus plant matter may occur slowly, preventing the full release of 

nutrients until 3-4 years after death and immobilizing N and P for a longer period of time relative to other sedges 

(Aerts and de Caluwe 1997, Verhoeven and Arts 1992). However, because C. acutiformis produces more leaf litter 

than most sedges, it may actually facilitate a higher rate of nutrient cycling than what the other sedges attain (Aerts 

and de Caluwe 1997).

Carex acutiformis may smother native plants via accumulation of its excess litter (Catling and Kostiuk 2003). 

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U’s Impact

>5 Any High
459

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 √
460

Unknown U

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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 1
461

OR

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U

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 

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, 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) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
462

Scientific Name: Carex disticha Huds.

Common Name: Tworank sedge, two-tank sedge, two rank sedge

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0√

Unknown U

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

It was reportedly a dominant plant where it established in Simnoe County, Ontario (Catling et al. 1988).

Carex spp. can transport oxygen from above ground portions to its deep root system, which enables these species to 

compete in water-logged ecosystems (Riutta et al. 2007).

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 

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
463

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

As of 1992, a total of 253 Carex hybrids have been reported in North America. This indicates that this genus is 

highly capable of hybridization, and invading species, such as C. disticha, may be a genetic threat to native species 

of sedges (Cayouette and Catling 1992).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
464

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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 
465

Not significantly 0 √

Unknown U

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0√

Unknown U

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

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
466

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 

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, 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) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
467

Scientific Name: Chenopodium glaucum

Common Name: Oak-leaved goosefoot

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

Chenopodium glaucum is one of the many members of the Chenopodium genus that is reported to produce saponins 

(Al-Jaber et al. 1992, Larina 2008). 

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 √

Chenopodium glaucum could pose a competitive threat to Chenopodium spp. that extend into the Great Lakes for at 

least a part of their native range. These species include (but are not limited to): C. album, C. berlandieri, C. 

capitatum, C. foggii, C. humile, C. leptophyllum, C. overi, C. pallescens, C. pratericola, C. rubrum, C. salinum, C. 

simplex, C. standleyanum, and C. subglabrum (USDA NRCS 2012).

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 √

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

etc.)?
468

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Chenopodium glaucum is capable of naturally hybridizing with C. rubrum, which is native to Ontario, Michigan, 

Wisconsin, Minnesota, and Illinois (USDA NRCS 2012, Wisskirchen 2006). 

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Environmental Impact Total 0

Total Unknowns (U) 3

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
469

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Plants, such as C. glaucum, that contain saponinshave been blamed for non-fatal poisonings in livestock, such as 

poultry and swine. New research indicates that saponins might be beneficial to species with rumen digestion systems 

(Cornell University 2009).

This species is described as a widespread weed in Russia, invading crop fields and vegetable gardens (Larina 

2008).

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

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
470

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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 √

Chenopodium glaucum is reported to have some value as forage due to high protein content in the leaves; however, 

over fertilization and insufficient water can create high, potentially toxic, nitrate concentrations (Brotherson et al. 

1980, Duan et al. 2004).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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 1
471

OR

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U

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 

Chenopodium glaucum is able to uptake mercury from contaminated soils. Application of thiosulphate greatly 

increases the solubility of mercury and increases phytoextraction by C. glaucum (Wang et al. 2011).

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, 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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
472

Scientific Name: Cirsium palustre (L.) Coss. ex Scop.

Common Name: Marsh thistle

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

There is also some evidence that C. palustre may be allelopathic, although this possibility has not been thoroughly 

investigated (Ballegaard and Warncke 1985).

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 

Realized impacts on native species and habitats following establishment have yet to be comprehensively documented 

or investigated (NatureServe 2011). Concern exists over the rapidly expanding range of C. palustre in the Great 

Lakes region (e.g., its southward movement in Michigan (Voss 1996)). Cirsium palustre can spread aggressively, 

resulting in reduced biodiversity and compromised ecological integrity; especially in the wetland ecosystems of 

Great Lakes islands (Cuthbert et al. 2007, USDA Forest Service 2005b). 

This plant is capable of spreading into open, undisturbed wetlands and forming clumps or impenetrable stands of 

flowering stalks or carpets of rosettes, potentially displacing native vegetation, altering community structure, and 

threatening natural diversity (Fraser 2000).

Marsh thistle is able to produce 2,000 viable seeds per plants; only a few plants are needed to have a drastic impact 

on the seed bank of an area (Fraser 2000, Sheehan 2007).

In British Colombia, C. palustre has been blamed for the degradation of sedge (Carex spp.) meadows (Sheehan 

2007). This species could pose a threat to the numerous native sedge communities; especially to rare, threatened, or 

endangered species (USDA NRCS 2012b.). 

Cirsium palustre poses a threat to C. pitcheri (Torr. ex Eaton) Torr. & A. Gray, which is native to the Great Lakes 

region and is classified as threatened by the federal government and the province of Ontario (COSSARO 2011, 

USDA NRCS 2012a.). Native swamp thistle, C. muticum, may also be at risk for adverse competitive effects 

(GLIFWC 2006).

Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 6
473

(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.)

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 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

In Europe, Cirsium arvense (a native to the Great Lakes) invades native populations of C. palustre and 

hybridizations between the two species have occurred. Such hybridizations are possible in North America where 

these species grow in close proximity, but none have been reported in the Great Lakes (Gucker 2009). 

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Environmental Impact Total 2

Total Unknowns (U) 1
474

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Although it is reportedly not a threat to cultivated agricultural areas, it may reduce forage quality following 

establishment in damp pastures (OLA and MAFF 2002).
475

It could form dense clumps in logged cut blocks, competing for moisture and nutrients with tree seedlings planted 

for reforestation. Tall stems can lead to snow press, permanently damaging tree seedlings (OLA and MAFF 2002).

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

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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 6
476

tourism

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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

Polyphenolic compounds extracted from C. palustre exhibit anti-microbial properties (Nazaruk et al. 2008). 

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 

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, 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

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
477

Scientific Name: Conium maculatum L.

Common Name: Poison hemlock

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

The effects of C. maculatum on livestock are well-known, but corresponding effects on wildlife are less commonly 

studied. However, poisoning has been documented in elk, rabbits, rats, and some birds (Forsyth and Frank 1993, 

López et al. 1999, Vetter 2004).

Conium maculatum is capable of hosting several disease-causing agents (e.g., Xylella fastidiosa, celery mosaic 

virus, carrot thin lead virus, and alfalfa mosaic virus) that could spread to surrounding plants from agricultural 

fields or vineyards (Howell and Mink 1981, Woodard 2008).

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

Conium maculatum is highly competitive and often grows taller than native species, shading and competing for 

space and nutrients with grasses and forbs (Pitcher 2004). It can be particularly competitive in soils with high 

nitrogen concentrations, where it rapidly utilizes nitrogen and outgrows other vegetation early in the growing 

season (Mamolos and Veresoglou 2000).

Recent research indicates that C. maculatum is more tolerant of heavy metal contaminants relative to native species, 

which may explain its ability to colonize disturbed habitats and displace natives during early successional stages. 

However, Granberg et al. (2009) also found it capable of inhabiting soils of diverse characteristics, suggesting that 

it is capable of spreading into natural areas.

There are no specific cases of Conium maculatum outcompeting native species in the Great Lakes region; however, 

given its pervasive competitive nature it is probable that this species affects natives in the Great Lakes. 

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
478

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 

Most vertebrates suffer from the toxic effects of this species, while very few invertebrates appear to inhabit C. 

maculatum or utilize it as a food source, even after being established in the U.S. for two centuries (Castells and 

Berenbaum 2008).

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 2

Total Unknowns (U) 0

Scoring
479

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Poisoning of humans has occurred following ingestion of seeds, leaves, and roots, and as a result of blowing 

through the plant’s hollow stems (e.g., when used as whistles or pea-shooters). 

The conium alkaloids found in C. maculatum are volatile and can cause toxic reactions when inhaled. 

Symptoms can include temporary skin reactions (hyperpigmenation, blisters, or burning sensation); decreased 

muscle control; gastro-intestinal symptoms; nervous system symptoms; and death from respiratory failure, if 

exposure is large/prolonged (Centre for Aquatic Plant Management 2004, Mitich 1998, Vetter 2004). 

Human deaths have occurred from harvesting and consuming the roots as wild carrots or parsnips, but the 

frequency of cases in the Great Lakes region is unknown.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

1 √
480

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0

Unknown U

Animals of agricultural importance are also affected by the toxicity of C. maculatum, including cows, horses, goats, 

sheep, swine, and poultry (turkeys, chicken, and quails) (Centre for Aquatic Plant Management 2004, Frank and 

Reed 1990, López et al. 1999). 

Ingestion of plant matter results in acute toxicity characterized by increased salivation, tremors, ataxia, depression, 

and respiratory distress, possibly leading to respiratory failure with high or prolonged doses (López et al. 1999, 

Vetter 2004). 

Cows and pigs may also experience temporary blindness after ingestion (Panter et al. 1992).

Animals that suffer from chronic toxicity during critical stages of pregnancy often give birth to young with mild to 

severe skeletal malformations, including cleft palates, arthrogryposis, scoliosis, and palatoschisis (Keeler and Balls 

1978, López et al. 1999, Panter et al. 1992, Vetter 2004). 

If the initial poisoning is not lethal, livestock animals can recover if future ingestion of C. maculatum is avoided 

(Frank and Reed 1987, López et al. 1999).

Cattle, pigs, goat, and elk should be kept away because they exhibit a preference to continue eating C. maculatum

even after the initial exposure (López et al. 1999, Panter and Keeler 1989).

Conium maculatum can outcompete desirable forage species (OLA and MAFF 2002). In addition to its status as a 

serious pasture weed in the U.S. and other countries, it is also known to infest cereal and vegetable crop fields, as 

well as orchards (Mitich 1998).

Alkaloids may be excreted through the milk of poisoned cattle, which can pose a threat to nursing animals or be a 

food safety concern if the milk is intended for human consumption (Panter and James 1990, Vetter 2004).

Conium maculatum is capable of hosting several disease-causing agents (e.g., Xylella fastidiosa, celery mosaic 

virus, carrot thin lead virus, and alfalfa mosaic virus) that could spread to surrounding plants from agricultural 

fields or vineyards (Howell and Mink 1981, Woodard 2008).

The extent of impact on Great Lakes agriculture is unknown.

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

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
481

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

Coniine (a derivative from C. maculatum) serves as an effective insecticide against aphids and blowflies 

(Mohammed 1999). 

Conium maculatum also contains the alkaloid gamma-coniceine which displays antifeedant properties against 

Deroceras reticulatum (Muller), a field slug (Birkett et al. 2004). This species is native to Western Europe, but has 

been introduced to Michigan, Ohio, and Ontario (White-McLean 2011).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Extracts of hemlock have been used medicinally for many years in treating tumors, ulcers and gout (Parsons 1973). 

However, its medicinal importance is ultimately very limited by the narrow distinction between therapeutic and 

toxic levels of administration (Vetter 2004).

Coniine hydrobromide, derived from C. maculatum, is used as an antispasmodic (Penn Veterinary Medicine 2012).

Ultra-diluted natural Conium remedies used in India were tested to see if this genus had inhibitory effects on breast 

cancer. These remedies caused cell cycle delay/arrest and apoptosis of the two breast cancer cell lines tested 

(Frenkel et al. 2010).

Mixtures of alkaloid containing water-alcohol extracts from C. maculatum and salicylic acid inhibit symptoms of 

inflammation (exudation, pain, fever) to the same extent as conventional non-steroidal anti-inflammatory treatments 

(Nesterova et al. 2009). Nesterova et al. (2009) believe that these substances could be an alternative treatment for 

pain caused by various inflammatory conditions.

Conmaculation, a piperidine alkaloid found in C. maculatum, exhibited strong antinocicpetive activity in mice; 

however, doses over 20mg/kg were lethal (Radulović et al. 2012). This compound also does not seem to affect 

locomotor skills (Arihan et al. 2009).
482

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

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, 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

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
483

Scientific Name: Echinochloa crus-galli

Common Name: Barnyard grass

Environmental: Moderate

Socio-Economic: High

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

This grass has been reported to accumulate levels of nitrate high enough to be toxic to farm animals (Holm et al. 

1977).

Echinochloa crus-galli has been identified as capable of hosting and transmitting the southern rice black-streaked 

dwarf virus in south China (Li et al. 2012b).

Root exudates from E. crus-galli were found to contain 15 phytotoxic compounds that are thought to be 

allelochemicals against the growth of other plant species (Xuan et al. 2006). Allelochemicals produced by young 

shoots inhibit the growth of rice and other plants growing in close proximity (Yamamoto et al. 1999 in Xuan et al. 

2006).

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

Echinochloa spp. are early successional hydrophytes that quickly colonize disturbed wetlands. However, members 

of this genus do not persist over time and are replaced by perennials (WIDNR 2012). 

Bhowmik and Reddy (1988) found that the presence of barnyard grass in tomato fields reduced the concentrations of 

nitrogen, phosphorous and potassium in the leaves of tomato plants.

Echinochloa crus-galli may pose a competitive threat to native species of Echinochloa such as E. muricata and E. 

walteri, which is endangered in Pennsylvania (PLANTS Team 2012). 

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

1
484

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 √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Echinochloa crus-galli also poses a genetic threat to E. muricata, because these two species are able to produce 

hybrids when growing in the same community (OLA and MAFF 2002).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

In 2008, the Great Lakes Indian Fish and Wildlife Commission (GLIFWC) reported that this species was too 

common to map (Falck et al. 2009).

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact
485

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great 

Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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 √

Yes, some damage to markets or sectors has been observed, but negative consequences have been 

small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 

Unknown U

In 1985, Hamill and Thomas found barnyard grass in 58% of the cornfields surveyed in Ontario. Estimated corn 

yield loses of 38% were reported for cornfields with an average barnyard grass density of 9 plants/m2 (Bosnić and

Swanton 1997). 
486

Echinochloa crus-galli has been observed to impact at least 36 different crops (e.g., rice, lettuce, cotton, tomato) in 

at least 61 different countries (Bhowmilk and Reddy 1988, Holm et al. 1991 in Xuan et al. 2006, Keely and Thullen

1991, Xuan et al. 2006).

The longer E. crus-galli is allowed to grow with a desired crop species, the greater the reduction in yield (Keely and 

Thullen 1991). Experiments conducted in Sunderland, Massachusetts showed that barnyard grass growing with 

tomato crops reduced the marketable fruit weight from 26-84% depending on density (Bhowmilk and Reddy 1988). 

Barnyard grass has been found in 81% of tested rice seed lots and reduced rice yields by up to 40% in one 

agricultural study (Kennedy et al. 1983). In China, densities of 25 plants/m2 reduced rice yield by 50% (Chin 2001).

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

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 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

BENEFICIAL EFFECT

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

Is it commercially valuable (e.g., for fisheries, aquaculture, agriculture, bait, ornamental trade, etc.)? 
487

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

Echinochloa crus-galli was originally cultivated for forage and sold under the name “wonder grass” (OLA and 

MAFF 2002). It is typically fed to livestock while still green and is appropriate for ensilage, but not for hay (Duke

1996).

Echinochloa crus-galli contains diethyl phthalate and phthalic acid, derivatives of which are used commercially in 

plasticizers in high-molecular-weight polymers. Unfortunately, these derivatives are toxic to humans, animals, fish, 

aquatic invertebrates, algae, and other microorganisms (Xuan et al 2006). 

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Echinochloa crus-galli is used in folk remedies for carbuncles, hemorrhage, sores, spleen disorders, cancer, and 

wounds (Duke 1996).

Echinochloa crus-galli contains a lipid transfer protein that inhibits the action of Phytophthora infestans, a 

pathogenic fungus that causes late blight of tomatoes and potatoes. These results suggest the possibility of creating 

crop plants tolerant to late blight by altering their existing genetic code to include this lipid transfer protein 

(Rogozhin et al. 2009). 

Barnyard grass also has two novel defensins that inhibit several phytopathogenic fungi (Odintsova et al. 2008). 

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

Echinochloa crus-galli is capable of leaching excess salts from soils and has been used for soil reclamation in Egypt 

(Abogadallah and Quick 2009, Aslam et al. 1987). It is also able to remove cadmium, copper, and lead from the 

soil; this ability is enhanced when citric acid is added to the soil (Kim and Lee 2010). Barnyard grass is also 

capable of accumulating zinc from wastewater (Liu et al. 2007). Germination of E. crus-galli was unaffected when 

exposed to the waste from a coke plant, a pulp mill, and a waste water treatment facility. Barnyard grass seedling 

growth increased after exposed to the some of the pollutants from a wastewater treatment plant (Adamus et al. 

2001). The ability to withstand unknown pollutants, even thrive under some conditions, indicated the potential to use 

E. crus-galli in constructed wetlands for wastewater treatment. 
488

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, 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

Seeds of barnyard grass can be eaten by songbirds and waterfowl; plants offer cover for waterfowl. 

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
489

Scientific Name: Epilobium hirsutum L.

Common Name: Great hairy willow herb 

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

Shamsi and Whitehead (1977) determined that this species can germinate and grow under conditions of low 

temperatures and short days; furthermore, due to its growth form and pattern of vegetative reproduction, it can 

rapidly exploit available space.

The persistent nature of hairy willow herb enables it to form monospecific populations that exclude other, especially 

native, species (Shamsi and Whitehead 1974) .

A joint survey conducted by the Invasive Plant Associate of Wisconsin (IPAW) and the Great Lakes Indian Fish and 

Wildlife Commission (GLIFWC) found that Epilobium hirsutum is a moderate competitor and has a moderate to 

high impact (Reinartz 2003).

Epilobium hirsutum could be a competitive threat to native species in Ohio, including E. angustifolium (state 

endangered) and E. strictum (state threatened) (ODNR 2012).

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
490

Unknown U √

In Washington state, hairy willow herb disrupts wetland food chains (State of Washington 2012).

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

A few occurrences of hybridization between E. hirsutum and E. ciliatum, a native to the Great Lakes and other 

parts of North America, have been found in Europe, resulting in E. x novae-civitatis (Online Atlas 2012). No such 

hybridization has been reported in the Great Lakes.

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Dense stands of E. hirsutum impede hydrology in waterways and wetlands (King County 2008, State of Washington 

2012).

Environmental Impact Total 2

Total Unknowns (U) 1

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate
491

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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
492

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

Epilobium hirsutum can co-exist with Lythrum salicaria (purple loosestrife) along riparian areas created by 

erosion. Great hairy willow herb outcompetes and grows faster than purple loosestrife in the shorter days and 

colder temperatures of autumn. In the spring, this relationship is reversed, with purple loosestrife having a faster 

growth rate (Shamsi and Whitehead 1974, Shamsi and Whitehead 1977).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

Does the species have some medicinal or research value (outside of research geared towards its control)?
493

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

Epilobium hirsutum L. is considered a medical plant in Bulgaria (Ivancheva et al. 1992).

Ethanolic extracts of E. hirsutum have antimicrobial properties (Battinelli et al. 2001). 

Methanolic extracts of E. hirsutum exhibited antinociceptive activity in mice. Doses of 500 mg/kg resulted in higher 

pain tolerance than doses of diclofenac (50 mg/kg) and morphine (5 mg/kg). Furthermore, doses of the methanolic 

extract (200-500 mg/kg) did not impair locomotor skills of mice (Pourmorad et al. 2007). 

A polyphenolic mixture of E. hirsutum (combined with a water-alcohol extract) had a significant inhibitory effect on 

the reproduction of influenza viruses (Ivancheva et al. 1992). 

A few of the polyphenols extracted from E. hirsutum, galloylglucose and monomeric and dimeric ellagitannins, are 

important compounds for the treatment of prostate cancer (Cristea et al. 2009). 

Initial experiments of alcohol extracts from E. hirsutum indicate other anti-tumor properties. Small doses of alcohol 

extract (1-3 mg/kg) prolonged the lifespan of mice with tumors by over 150% (Voynova et al. 1991). 

Flavonoids (3-O-glycosides of quercetin, myricetin, and kaempferol) and a macrocircular dimeric ellagitannin 

oenothein D have been detected in dried fragments of E. hirsutum (Strgulc Krajšek et al. 2011). Increased intake of 

total flavonols is associated with a reduced risk of pancreatic cancer, with kaempferol linked to greatest reduction 

in risk (Nöthlings et al. 2007). In epidemiological studies quercetin supplements reduced blood pressure in 

hypertensive rodents. Quercetin is thought to be linked with a lowering the risk of coronary heart disease and/or 

stroke (Edwards et al. 2007). 

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 

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, 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

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown
494

1 ≥1
495

Scientific Name: Rhamnus frangula (Frangula alnus)

Common Name: Glossy buckthorn

Environmental: High

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

European starlings, rose-breasted grosbeaks, cedar waxwings, and American robins, all of which have at least part 

of their range in the Great Lakes, feed on the fruits of glossy buckthorn (Michigan Natural Features Inventory 

2012). Small mammals, such as rodents, also feed on this berries (NRCS 2007). However, consuming these berries 

often leads to a net energy loss due to their diarrheic qualities (Czarapata 1999 in Falck and Garske 2002).

Rhamnus spp. are a winter host to the introduced pest soybean aphid, Aphis glycines (NRCS 2007). Soybean aphids 

have been collected from R. frangula in Springfield fen, Indiana (Hill et al. 2010). 

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 Gavin Bog, Illinois, R. frangula has displaced Ilex verticillata, a native species to the Great Lakes (Taft and 

Solecki 1990 in Frappier et al. 2003).

Rhamnus frangula leafs out early in spring and retains its leaves late into the fall (Ohio EPA 2001, PADCNR n.d.) 

The leaves remain photosynthetically active until the senesce from the plant, allowing glossy buckthorn to outcompete native trees, shrubs, and wildflowers for light (GLC 2006, NRCS 2007, State of Minnesota 2009).

The extensive root system of R. frangula allows it to out-compete native plant for nutrients and water (Ohio EPA 

2001, State of Minnesota 2009). 

Rhamnus frangula may be a competitive threat to two endangered Rhamnus spp. in the Great Lakes: R. alnifolia

(endangered in Illinois) and R. lanceolata (endangered in Pennsylvania) (PLANTS Team 2012).

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 
496

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 √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U

Glossy buckthorn is threatening the current ground vegetation and preventing oak seedling growth in oak savannas, 

which is an endangered ecosystem in the Midwest (Mills 1993 in Pleasant Valley Conservancy 2012; Reid and 

Holland 1997).

In Indiana, glossy buckthorn has been recorded invading the understory and reducing the diversity of native plants 

crucial to native wildlife (Illinois Natural Heritage Database 2011). 

Rhamnus frangula is invading various wetland ecosystems in Wisconsin and is shading out native plants in the 

process (Thompson and Luthin 2004). 

Sinclair and Catling (1999 in Frappier et al. 2004) found that the presence of R. frangula in wetlands in Ontario 

reduced species richness and that when removed, the density of native plants increased. 
497

Possessky et al. (2000 in Frappier et al. 2004) found that in savanna ecosystems in Pennsylvania the species 

richness was higher in areas were R. frangula was present. 

Mills et al. (2009) also found little change in the resident plant community after glossy buckthorn was allowed to 

grow and expand freely into the study site. 

Monocultures are formed, which harms songbird habitat and shifts the plant ecosystem to those that are more shade 

tolerant (NRCS 2007, Roman 2007). 

Along with changing the amount of available light in an ecosystem, glossy buckthorn also uses allelopathy to alter 

the plant community around it (PADCNR n.d.). 

If glossy buckthorn becomes a dominating species in an ecosystem, the ability of a forest to regenerate and continue 

through the steps of succession may become severely limited (Forest Health Staff 2006). 

Dense patches of glossy buckthorn may also contribute to erosion by shading out other plants that grow on the 

forest floor (State of Minnesota 2009).

Buckthorns are often found in soils with higher nitrogen content, although it is unknown if this is due to initial 

establishment conditions or if buckthorns alter the surrounding soil chemistry via their leaf litter. This also makes 

the surrounding soil environment more favorable for exotic earthworms. Exotic earthworms are known to alter soil 

characteristics by increasing carbon, nitrogen, pH, and moisture as well as modifying the microbial community 

(Roman 2007). 

Environmental Impact Total 13

Total Unknowns (U) 2

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
498

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Forests of Pinus strobes that are invaded by R. frangula may become less valuable for logging as glossy buckthorn 

spreads and prevents white pine from regenerating (Fagan and Peart 2004). 

Horses may become poisoned if allowed to consume R. frangula (van den Dikkenberg and Holtkamp 1987). 

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

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

Fruits from R. frangula will stain houses, cars, patio furniture, sidewalks, etc. (State of Minnesota 2009).

Socio-Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
499

BENEFICIAL EFFECT

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

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

In some areas glossy buckthorn is still sold in nurseries in two different forms Columnaris and Asplenifolia 

(Michigan Natural Features Inventory 2012).

Glossy buckthorn provides attractive wood that can be used to build trellises, carved into walking sticks, or used in 

artwork (Larson 2009).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

Many homeowners appreciate dense thickets of R. frangula forms, because it provides privacy (Larson 2009). 

The wood also burns slowly, making it a good choice for firewood (Larson 2009).

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

Extracts of R. frangula, often in combination with other plants, have been used in laxatives for humans. Matev et al. 

(1981) reports that the combination of R. frangula, Citrus aurantium, and Carum carvi was an effective laxative in 

100% of the subjects. 

Anthraquinones extracted from R. frangula successfully inactivated the herpes simplex virus type 1 in laboratory 

experiments (Sydiskis et al. 1991). 

Methanol extracts of R. frangula may have anti-fungal properties (Manojlovic et al. 2005).

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 

Rhamnus frangula is able to accumulate manganese and may be useful is soil remediation (Alvarez et al. 2003). 
500

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, 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 

This species provides cover and nesting space for a variety of birds for a longer period of time than native species. 

However, species nesting in glossy buckthorn can be more susceptible to predation because glossy buckthorn lacks 

the protective thorns of many native shrubs (Roman 2007). 

Beneficial Effect Total 2

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
501

Scientific Name: Glyceria maxima

Common Name: Reed manna grass

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low 

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0

Unknown U √

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

Glyceria maxima invades numerous wetland ecosystems: swamps, lakes, ponds, slow-moving rivers and creeks, 

ditches, and wet meadows (Boos et al. 2010). 

Early emergence in spring and rapid growth enables this species to outcompete other wetland plants (Buttery and 

Lambert 1965, King County 2012).

Glyceria maxima can form monospecifc stands and reduce plant diversity along the shore to a depth of about 15 cm 

(Andersson 2001, Boos et al. 2010, Forest Health Staff 2006).

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 

Expansion of G. maxima degrades the ecological dynamics in the wetland (Forest Health Staff 2006). The 

displacement of native vegetative often leads to an altered macroinvertebrate community which can impact the 

entire food web for the ecosystem (King County 2012).
502

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Glyceria maxima may also be a competitive threat to native species of manna grass. These native species that are 

listed as threatened or endangered in at least one Great Lake State: G. acutiflora Torr., G. arkansana Fernald, G. 

borealis (Nash) Batchelder, G. grandis S. Watson, and G. obtusa (Muhl.) Trin (PLANTS Team 2012).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Glyceria maxima have an extensive system of roots and rhizomes (King County 2012). Dense populations of this 

species create rhizomal mats that can trap sediment faster than native species. This increased sedimentation can 

alter the flow of water, restrict or even clog small waterway and drainages, and cause flooding (Forest Health Staff 

2006, King County 2012).

Availability of organic material and denitrifying capacity is high in G. maxima dominant ecosystems (Kallner 

Bastviken et al. 2007). Glyceria maxima also uptakes available ammonium, which further decrease nitrifying 

activities (Bodelier et al. 1998). As G. maxima increases in a habitat, the availability of nitrogen in the soil could 

decrease. 

Environmental Impact Total 3

Total Unknowns (U) 2

Scoring
503

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Reduced flow rates in water ways from siltation and debris build-up also creates breeding habitat for mosquitoes 

(Department of Primary Industries 2012). 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Large communities of G. maxima can impede water flow, alter hydrology and even restrict access to natural 

waterways, and irrigation or drainage channels. In Tasmania, populations of G. maxima have created so much 

additional silt (from reduced water flow) that shallow dams have become useless (Department of Primary Industries 

2012).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 
504

Not significantly 0 √

Unknown U

Glyceria maxima has been used as forage, however cattle may experience cyanide poisoning if allowed to graze on 

young shoots (Boos et al. 2010, King County 2012).

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

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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 G. maxima could begin growth early in the season it can out-compete Phragmites australis (StuderEhrenseberger et al. 1993).

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
505

Sold and used as an ornamental (King County 2012).

Used in wastewater treatment in some European countries (Harrington et al. 2012, Sundblad and Robertson 1988)

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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

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 

Glyceria maxima tolerates low oxygen concentrations and it thrives in eutrophic environments, making it an ideal 

species for artificial wetland systems (Sunblad and Robertson 1988). Glyceria maxima has been used to treat the 

wastewaters from swine farms in integrated constructed wetlands (ICW) in Ireland. During an 18-month study, the 

ICW successfully removed 98.1-99.9% of the ammonia-nitrogen (Harrington et al. 2012). In other ICWs planted 

with only G. maxima, there was significant reduction in total organic nitrogen, ammonia-nitrogen, nitrate-nitrogen 

and molybdate reactive phosphorus (Harrington and Scholz 2010). In experiments by Sundblad and Robertson 

(1988) in the Czech Republic, harvesting G. maxima may increase the nutrient recovery from the wastewater.

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, 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

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
506

1 0

0 ≥2 Unknown

1 ≥1
507

Scientific Name: Hydrocharis morsus-ranae L.

Common Name: Common frogbit

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

This species is also capable of aggressive growth: one hibernaculum (starting material for a new plant) can grow to 

cover an area one diameter in diameter in a single season (Haynes 1988). 

The free-floating form can lead to densely tangled floating mats, which can crowd and shade out native aquatic 

vegetation (Catling et al. 2003, Grant 2013).

Populations of H. morsus-ranae can also compete for nutrients and gases; further reducing the growth of nearby 

vegetation (Lui et al. 2010).

There was a 95% decline submerged vegetation species below mats of H. morsus-ranae (Catling et al. 1988 in 

Mudrzynski et al. 2011). 

There are discrepancies regarding the extent of H. morsus-ranae in the Great Lakes. Trebitz and Taylor (2007) state 

that this species rarely becomes dominant in Lakes wetlands. However, there have also been reports that H. morsusranae population have been aggressively growing in large areas of shallow, open waters in Michigan (Reznicek et 

al. 2011). 

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)

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 
508

Unknown U 

As colonies H. morsus-ranae displace native plants; other native aquatic life experience a reduction in food and 

habitat (Environment Canada 2003, WI DNR 2012). 

Dense mats can inhibit the movement of waterfowl or larger fish; which could alter predator/prey cycles as the 

waterfowl and fish move to other locations to find food (O’Neill Jr. 2007, University of Minnesota, Wisconsin Sea 

Grant Institute 2012). 

Catling et al. (1988) surveyed life H. morsus-ranae mats and found a decline in snails, crustacean, and insect larvae 

(in Mudrzynski et al. 2011).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

In the autumn, H. morsus-ranae dies and sinks to the bottom of the water body, where it decomposes (IL DNR 2009). 

Altered hydrology and/or increased decomposition can reduce oxygen concentration in nearby waters and could 

potentially lead to the death of nearby plants, insects or fish and insects (Catling et al. 2003, IL DNR 2009). 

However, Thomas and Daldorp (1991) found that the addition of the H. morsus-ranae had no effect on the 

macrophyte community or on the dissolved oxygen profiles. 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dense stands can alter the water flow or currents (Mikulyuk and Nault 2011).

Environmental Impact Total 3

Total Unknowns (U) 2
509

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)? 

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Large infestations of H. morsus-ranae have reduced water currents in canals and irrigation systems (Catling et al. 

2003). 
510

Dense layers of tangled stems and roots can wrap about boat propellers and impede water traffic (Lui et al. 2010, 

University of Minnesota Wisconsin Sea Grant Institute 2012).

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 

Large populations of common frogbit also limit recreational activities such as swimming, fishing, and waterfowl 

hunting (Grant 2013, Lui et al. 2010, University of Minnesota Wisconsin Sea Grant Institute 2003).

The decreased recreational and aesthetic value linked to large populations of H. morsus-ranae can... even cause 

declines in tourism and associated revenue (Mikulyuk and Nault 2011). 

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 decreased recreational and aesthetic value linked to large populations of H. morsus-ranae can lead to a 

reduction in property value along the affected waterfront... (Mikulyuk and Nault 2011). 

Socio-Economic 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

BENEFICIAL EFFECT

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 

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 
511

Yes, but its economic contribution is small 1 

Not significantly 0 √

Unknown U 

Some property owners consider it to have aesthetic appeal and is used in water gardens (New York Invasive 2012). 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Spermidine, an anti-aging compound, can be found in dormant turions of H. morsus-ranae (Villanueva et al. 1985).

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 

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, 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 

Some species of water birds, fish, and insects feed on H. morsus-ranae (O’Neill Jr. 2007). 

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
512

Scientific Name: Impatiens glandulifera Royle

Common Name: Ornamental jewelweed

Environmental: Unknown 

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √

Impatiens glandulifera is considered to be one of the most invasive plants of the world (Weber 2000 in Vervoort et 

al. 2011).

It is able to out-compete beneficial, and often native, plants for physical space, light, and nutrients (Tanner 2011).

Early spring emergence, plus the ability to capitalize on disturbance opportunities, can lead to dense monospecific 

stands (Perrins et al. 1993).

As access to nutrients increases, I. glandulifera individuals will allocate extra resources and energy for seed 

production (Willis and Hulme 2004).

However, studies of six riparian communities in the Czech Republic indicated that I. glandulifera has a negligible 

effect on existing communities and therefore is not a threat to plant diversity there (Hejda and Pyšek 2006).

Preferential visitation of ornamental jewelweed by pollinators could ultimately lead to a reduction in fitness of 

neighboring species (Chittka and Schürkens 2001 in Tanner 2011). In a study conducted by Vervoort et al. (2011) in 

Belgium, I. glandulifera was visited by potential pollinators up to 250 times—substantially more than other 

Impatiens species studied (< 10 visits). However, in a study conducted in Germany, there was no significant 

evidence to suggest that I. glandulifera out-competes native plants for pollinators during periods of simultaneous 

blooming (Bartomeus et al. 2010).

Due to its genetic variation, I. glandulifera has the ability to adapt to local environments within a few generations 

and has a strong probability of expanding northward into previously unoccupied niches (Kollmann and Bañuelos 

2004). Ornamental jewelweed also seems to react positively to increases in carbon dioxide and temperature. With 

increasing global mean temperature, I. glandulifera could expand its range northward by several degrees latitude 

(Beerling 1993).

Even though impacts of I. glanulifera have been studied in detail elsewhere, the extend of the impacts in the Great 

Lakes are not as well documented.
513

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 √

As native plants become displaced, specialized herbivorous insects leave the area and subsequently lead to a shift in 

the predatory insect community (e.g., spiders). There is the potential for further trophic shifts, as well (Tanner 

2011).

However, alterations to predator-prey cycles or trophic shifts have not been recorded in the Great Lakes. 

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0
514

Unknown U

If it displaces perennial vegetation along water bodies, soil erosion is likely to occur (IPANE 2004). 

The adventitious roots of ornamental jewelweed can obstruct waterways and wetlands, which can alter hydrology of 

the ecosystem. This altered hydrology can lead to increased erosion or flooding (Forest Service 2007, King County 

2007). A larger sediment load in the river could in turn reduce available habitat and smother benthic communities 

(Tanner 2011).

At maturity, ornamental jewelweed is taller and has relatively larger leaves than most grasses and forbs. This 

shading effect creates bare patches nearby, facilitating germination and emergence of additional I. glandulifera

seedlings (Centre for Aquatic Management 2004, King County 2007).

The stems of I. glandulifera have high holocellulose content (insoluble carbohydrates) that does not fully decompose 

over the winter. As a result, litter still present in the spring can suppress other plant seedlings (Beerling and Perrins 

1993).

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

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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
515

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

BENEFICIAL EFFECT

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
516

When I. glandulifera and Lythrum salicaria (purple loosestrife, another major invasive of the Great Lakes) share a

pollinator community, I. glandulifera will out-compete L. salicaria for pollinators, ultimately decreasing pollen

deposition and seed production in the latter (Thijs et al. 2012).

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

In the Czech Republic, I. glandulifera is an important source of nectar and pollen because its bloom period lasts

longer than many of the native plant species. Starý and Taklcú (1998) have concluded that the present of I.

glandulifera has contributed to the conservation of several bumble-bee species.

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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

Scoring

Score # U Impact
517

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
518

Scientific Name: Iris pseudacorus

Common Name: Yellow iris

Environmental: High

Socio-Economic: Moderate

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Yellow iris contains glycosides that can cause skin irritation in wildlife that come in contact with this plant; animals 

can also experience non-fatal poisoning if plant matter is ingested (Lui et al. 2010).

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

Iris pseudacorus is tolerant of a range of water conditions (salinity, poor water quality, drought) that enable it to be 

a good competitor in a variety of wetland ecosystems (Sarver et al. 2008). 

The clonal nature of I. pseudacorus causes it to form dense stands and thick, submerged rhizome mats (Idaho 

Invasives 2007, Lui et al. 2010) that can prevent the germination and growth of native species (sedges, rushes, etc.) 

and eventually displace them entirely (Lui et al. 2010, MNDNR 2012, Noxious Weed Control Program 2009, ODA 

2012).

Iris pseudacorus can also out-compete neighboring plants for pollinators (Dieringer 1982).

Iris pseudacorus may be a competitive threat to native irises, including I. brevicaulis (listed as threatened in Ohio), 

I. cristata, I. lacustris (endemic to the Great Lakes), I. robusta [versicolor x virginica] (endemic to the Great Lakes), 

I. setosa, I. verna (listed as threatened in Ohio), I. versicolor, I. virginica, and I. virginica var. shrives (USDA and 

NRCS 2012, ODNR 2012).

In wetland ecosystems in the eastern United States, I. pseudacorus has reduced the density of native sedges and 

rushes that serve as habitat for other species, especially waterfowl (Jacobs et al. 2011).

In Connecticut, I. pseudacorus successfully excluded native arrow-arum (Peltandra virginica), which is an important 

food source for nesting wood ducks (Cox 1999).

By 1970, yellow iris was found growing to the complete exclusion of Typha and other native marsh plants along the 

Merced River in California (Raven and Thomas 1970). It later expanded along 1300 miles of irrigation canals and 

laterals near Flathead Lake in northwestern Montana (Lake County Weed District, Pablo, Mont., pers. comm. 

2001).

Yellow iris has a high anoxia tolerance. During the growing season, it can survive at least 28 days of dark and 

anoxia; this period is increased to 60 days for overwintering plants (Schlüter and Crawford 2001). When exposed to 
519

prolonged periods of anoxia, I. pseudacorus increased production of superoxide dismutase enzymes that help the 

plant cope with oxidative stress (drought, nutrient deficiencies, injury, etc.) (Monk et al. 1987). The ability to cope 

with and recover from stress faster than neighboring plants may enable it to be a better competitor.

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 √

Populations of yellow iris create a positive feedback loop: once established, the roots trap sediment, which enables 

growth of new seedlings, which in turn trap more sediment (Jacobs et al. 2011). This increase in sedimentation also 

creates new habitat for shrubs and trees, thereby altering it to a drier ecosystem (Lui et al. 2010, Sarver et al. 

2008). This alteration reduces the food supply and nesting habitat of many fish and waterfowl that depend on 

wetlands (Noxious Weed Control Program 2009, ODA 2012).

Such alterations have not been documented in the Great Lakes.

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

Yes, and it has had a widespread, long term, or severe negative effect on the physical ecosystem

AND/OR

6
520

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

The vegetative growth of yellow iris can trap sediment, raise local elevation of the ecosystem, and alter wetland 

hydrology (Noxious Weed Control Program 2009, Sarver et al. 2008). Increase in sedimentation also creates new 

habitat for shrubs and trees, thereby altering it to a drier ecosystem (Lui et al. 2010, Sarver et al. 2008).

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

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

All parts of I. pseudacorus are poisonous (Idaho Invasives 2007). Resins can cause skin irritation and blistering; if 

ingested, this plant will cause gastric distress in humans (ISCBC 2012, Lui et al. 2010, Sutherland 1990).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Stands of I. pseudacorus can reduce flow and block irrigation systems and flood control ditches (Noxious Weed

Control Program 2009, ODA 2012). 

Its seeds can clog pipes and water control structures (Noxious Weed Control Program 2009). 

Removal of plant material from these systems may require herbicides or excavation equipment and can be costly 

(ODA 2012).
521

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Yellow iris (live or dried) can cause gastroenteritis in cattle and sicken other livestock if ingested, although grazing 

animals tend to avoid it (Lui et al. 2010, Sutherland 1990). 

Because palatable species go relatively untouched when intermingled with I. pseudacorus, the quality of pastureland 

can be reduced (Bossuyt et al. 2005).

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

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 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
522

BENEFICIAL EFFECT

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

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

Iris pseudacorus is a popular ornamental plant.

Historically, the flowers of I. pseudacorus has been used to make a yellow dye, and the rhizomes were used as a 

powerful herbal laxative and emetic (Jacobs et al. 2011).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

Ripe seeds, if well roasted before consumption, can be a substitute for coffee (Sturtevant and Hedrick 1972).

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

Water-soluble polysaccharides extracted from I. pseudacorus appear promising for pharmaceutical uses (Sanavova 

and Rakhimov 2004).

Ethanol extracts of I. pseudacorus show larvicidal and mirscidiacidal/cercarcidal (compounds that kills trematode 

larvae) properties (Ahmed and Hamshary 2005).

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 √

Many studies have investigated the use of I. pseudacorus in wastewater treatment to reduce total nitrogen and total 

phosphorus concentration, and some treatment wetlands in the Czech Republic already use this species (Benson et 

al. 2004, Vymazal and Kröpfelová 2008). Wu et al. (2011) claimed that I. pseudacorus is a preferred plant species 

for treatment wetlands in Northern China because of its ability to uptake nutrients and its pleasant appearance. 

Barbolani et al. (1986) determined that I. pseudacorus was able to uptake cadmium and copper from contaminated 
523

waters, with a preference to uptake copper. Yellow iris is able to absorb these metals in proportion to what is 

available in the environment, with stands exposed to higher initial metal concentrations tending to absorb more 

metal than stands exposed to lower concentrations (Barbolani et al. 1986). Iris pseudacorus was able to remove 

copper from solutions that also contained surfactants and chlorides (Piccardi and Clauser 1983). Iris pseudacorus

may be an economic choice for treatment wetlands designed to treat complex, urban wastewaters that contain heavy 

metals (Larue et al. 2010, Piccardi and Clauser 1983, Zhang et al. 2007). The rhizomes of I. pseudacorus can also 

reduce populations of Escherichia coli, Salmonella, and Enterocoli by 50-70% in a 24 hour period (Jacobs et al. 

2011).

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, 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

It can be planted along slopes and shores to prevent erosion control (Jacobs et al. 2011).

Muskrats use this species for building their dens (Jacobs et al. 2011).

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
524

Scientific Name: Juncus compressus Jacq.

Common Name: flattened rush 

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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 this species establishes in an ecosystem, it will likely persist (Stuckey 1981 in Vincent and Cusick 1998).

In wetland environments, rushes will out-compete other plant species (Stevens and Hoag 2003).

Juncus compressus poses a competitive threat to the native and naturalized Juncus spp. in the Great Lakes, 

especially those listed as threatened or endangered including J. alpinus auct. non Vill., J. ambiguus Guss., J. 

balticus Willd., J.biflorus Elliot, J. marginatus Rostk. var. biflorus (Elliot) Alph. Wood, J. brachycarpus Engelm., J. 

brachycephalus (Engelm.) Buchenau, J. dichotomus Elliot, J. diffusissimus Buckley, J. ensifolius Wikstr., J. greenei 

Oakes & Tuck., J. interior Wiegand, J. militaris Bigelow, J. pelocarpus E. Mey., J. scirpoides Lam., J. secundus P. 

Beauv. ex Poir., J. stygius L., J. stygius L. ssp. americanus (Buchenau) Hultén, J. subcaudatus (Engelm.) Coville & 

S.F. Blake, J. vaseyi Engelm. (USDA NRCS 2012c).

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 √
525

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

There are no known records of hybrids between J. compressus and other species, but this genus contains several 

natural hybridizations (USDA NRCS 2012a). Furthermore, several species of this genus have synchronous 

flowering to attract pollinators, which creates the potential for outcrossing (Michalski and Durka 2007).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

In the United Kingdom, the roots of Juncus spp. have been observed to trap water and alter the hydrology in shallow 

water environments (Centre for Aquatic Plant Management 2004).

Environmental Impact Total 2

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
526

1 0

0 ≥2

Unknown 1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

Many Juncus spp. serve as a host for larvae of Coquillettidia, a genus of mosquitoes that can serve as a vector for 

various animal-borne vectors (Sérandour et al. 2010).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 √
527

Unknown U

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

Juncus compressus may be confused with or pose a competitive threat to rushes that are culturally important, 

including J. arcticus ssp. littoralis and J. effusus (USDA NRCS 2012b).

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

BENEFICIAL EFFECT

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

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

Cattle, horses, and sheep will graze on Juncus spp., but their specific value as fodder is unknown (Centre for 

Aquatic Plant Management 2004, Cosyns et al. 2005).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U
528

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

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 rhizome matrix can support numerous bacteria, which can be used in wastewater treatment (Stevens and Hoag 

2003).

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, 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

Numerous animals feed on the seeds of rushes, including waterfowl, songbirds, quail, cottontail, muskrat (also feeds 

on roots and rhizomes), porcupine, and other small mammals (Martin 1951 in Stevens and Hoag 2003).

Juncus spp. provide habitat for amphibians and various wetland birds, as well as spawning ground for some fish 

species (Stevens and Hoag 2003).

The dense root and rhizome system of Juncus spp. enable them to survive periods of stress (drought, flood, etc.), 

accumulate soil, and provide erosion control (Stevens and Hoag 2003).

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
529

Scientific Name: Juncus gerardii Loisel.

Common Name: black-grass rush

Environmental: Moderate

Socio-Economic: Low 

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

Juncus gerardii cannot invade areas with existing vegetation or dense litter (Ericson 1981 in Jutila 1999). Juncus 

gerardii seedlings also have little resistance to burial by wrack (floating plant material); significant amounts can 

lead to burial and ultimately seedling death (Brewer et al. 1998). For these reasons, J. gerardii becomes established 

in the first stages of succession after a disturbance (Bouzillé et al. 1997). Once established, this species can 

dominate terrestrial borders of high marshes and displace native species, such as Spartina patens (Bertness 1991 in 

Charpentier et al. 1998, Levine et al. 1998). 

Juncus gerardii poses a competitive threat to the native and naturalized Juncus spp. in the Great Lakes, especially 

those listed as threatened or endangered, including J. alpinus auct. non Vill., J. ambiguus Guss., J. balticus Willd., J. 

biflorus Elliot, J. marginatus Rostk. var. biflorus (Elliot) Alph. Wood, J. brachycarpus Engelm., J. brachycephalus 

(Engelm.) Buchenau, J. dichotomus Elliot, J. diffusissimus Buckley, J. ensifolius Wikstr., J. greenei Oakes & Tuck., 

J. interior Wiegand, J. militaris Bigelow, J. pelocarpus E. Mey., J. scirpoides Lam., J. secundus P. Beauv. ex Poir., J. 

stygius L., J. stygius L. ssp. americanus (Buchenau) Hultén, J. subcaudatus (Engelm.) Coville & S.F. Blake, J. vaseyi 

Engelm. (USDA NRCS 2012c).

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

1
530

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 √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

There are no known records of hybrids between J. gerardii and other species, but this genus contains several natural 

hybridizations (USDA NRCS 2012a). Several species of this genus have synchronous flowering to attract 

pollinators, which creates potential for outcrossing (Michalski and Durka 2007). However, Bouzillé et al. (1997) 

determined that sexual reproduction and seed dispersal had little significance on total reproduction and expansion 

of communities of J. gerardii.

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U 

In the United Kingdom, the roots of Juncus spp. have been observed to trap water and alter the hydrology in shallow 

water environments (Centre for Aquatic Plant Management 2004).

Environmental Impact Total 2

Total Unknowns (U) 2
531

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Many Juncus spp. serve as a host for larvae of Coquillettidia, a genus of mosquitoes that can serve as a vector for 

various animal- and human-borne vectors (Sérandour et al. 2010).

The vegetative parts of J. gerardii are round, stiff, and sharp enough to puncture human skin (College of 

Environment 2012).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
532

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

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

Juncus gerardii may be confused with or pose a competitive threat to rushes that are culturally important, including 

J. arcticus ssp. littoralis and J. effusus (USDA NRCS 2012b).

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

BENEFICIAL EFFECT

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

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

Cattle, horses, and sheep will graze on Juncus spp., but their specific value as fodder is unknown (Centre for 

Aquatic Plant Management 2004, Cosyns et al. 2005).

Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal activity)?
533

Yes, it is commonly employed recreationally and has some perceived value for local communities and/or 

tourism

6

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 rhizome matrix can support numerous bacteria that are useful in wastewater treatment (Stevens and Hoag 

2003).

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, 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

Numerous animals feed on the seeds of rushes, including waterfowl, songbirds, quail, cottontail, muskrat (also feeds 

on roots and rhizomes), porcupine, and other small mammals (Martin 1951 in Stevens and Hoag 2003).

Juncus spp. provide habitat for amphibians and various wetland birds, as well as spawning ground for some fish 

species (Stevens and Hoag 2003).

The dense root and rhizome system of Juncus spp. enable them to survive periods of stress (drought, flood, etc.), 

accumulate soil, and provide erosion control (Stevens and Hoag 2003).

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
534

1 ≥1
535

Scientific Name: Juncus inflexius L.

Common Name: European meadow rush

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 this species establishes in an ecosystem, it will likely persist (Stuckey 1981 in Vincent and Cusick 1998). 

Under ideal conditions, J. inflexus can live up to 8 years (Chalet Nursery 2012).In wetland environments, rushes 

will out-compete other plant species (Stevens and Hoag 2003).

Juncus inflexus tends to have a significant presence in the seed bank in areas of intensive agriculture (Reiné et al. 

2004).

Juncus inflexus poses a competitive threat to the native and naturalized Juncus spp. in the Great Lakes, especially 

those listed as threatened or endangered, including J. alpinus auct. non Vill., J. ambiguus Guss., J. balticus Willd., J. 

biflorus Elliot, J. marginatus Rostk. var. biflorus (Elliot) Alph. Wood, J. brachycarpus Engelm., J. brachycephalus 

(Engelm.) Buchenau, J. dichotomus Elliot, J. diffusissimus Buckley, J. ensifolius Wikstr., J. greenei Oakes & Tuck., 

J. interior Wiegand, J. militaris Bigelow, J. pelocarpus E. Mey., J. scirpoides Lam., J. secundus P. Beauv. ex Poir., J. 

stygius L., J. stygius L. ssp. americanus (Buchenau) Hultén, J. subcaudatus (Engelm.) Coville & S.F. Blake, J. 

vaseyi Engelm. (USDA NRCS 2012c).

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 

1
536

which have not been widespread or severe

Not significantly 0

Unknown U √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Juncus inflexus also poses a genetic threat, because hybrids with J. effusus are possible when these species grow in 

the same location (Clifford 1958). Several species of this genus have synchronous flowering to attract pollinators, 

which creates potential for outcrossing (Michalski and Durka 2007).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1√

Not significantly 0

Unknown U 

In the United Kingdom, the roots of Juncus spp. have been observed to trap water and alter the hydrology in shallow 

water environments (Centre for Aquatic Plant Management 2004).

Environmental Impact Total 2

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High
537

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Many Juncus spp. serve as a host for larvae of Coquillettidia, a genus of mosquitoes that can serve as a vector for 

various animal- and human-borne vectors (Sérandour et al. 2010).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
538

Yes, but negative consequences have been small 1

Not significantly 0 √

Unknown U

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

Juncus inflexus may be confused with or pose a competitive threat to rushes that are culturally important, including

J. arcticus ssp. littoralis and J. effusus (USDA NRCS 2012b).

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

BENEFICIAL EFFECT

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

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

Cattle, horses, and sheep will graze on Juncus spp., but their specific value as fodder is unknown (Centre for 

Aquatic Plant Management 2004, Cosyns et al. 2005).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √
539

Unknown U

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

After 20 days of exposure, J. inflexus was able to remove all 100 mg/L of ethylene glycol dinitrate (EGDN), an 

explosive ingredient in dynamite, from in vitro regenerants (Podlipná et al. 2010). However, when exposed to 500 

mg/L, J. inflexus began to die (Podlipná et al. 2008).

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 rhizome matrix can support numerous bacteria that are useful in wastewater treatment (Stevens and Hoag 

2003).

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, 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

Juncus inflexus can be planted in rain gardens and for erosion control (Missouri Botanical Garden 2012).

Numerous animals feed on the seeds of rushes, including waterfowl, songbirds, quail, cottontail, muskrat (also feeds 

on roots and rhizomes), porcupine, and other small mammals (Martin 1951 in Stevens and Hoag 2003).

Juncus spp. provide habitat for amphibians and various wetland birds, as well as spawning ground for some fish 

species (Stevens and Hoag 2003).

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
540

Scientific Name: Lupinus polyphyllus

Common Name: Lupine

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Twenty-nine quinolizidine alkaloids have been found and characterized from the combined leaf/hypocotyl extracts of 

Lupinus polyphyllus (Veen et al 1992). Alkaloids present in the plant are mildy toxic and cause a bitter taste. Most 

herbivores quickly learn to avoid them, consumption (including in hay) may be harmful to sheep and cattle.

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., critical reduction, extinction, behavioral 

changes) 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 √

It can outcompete native species occurring in road verges, ruderal areas, gravelly floodplains and other open 

habitats.

Lupin alkaloids are also allelopathic, inhibiting germination of many seeds, and L. polyphyllus may outcompete 

native plants via this mechanism (Wink 1983, Muzquiz et al 1994).

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)

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 

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 which may be irreversible or has led to the decline or 6 
541

extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Lupinus polyphyllus is known to hybridize with other lupines. It is unknown whether it is hybridizing with the 

sundial lupine (Lupinus perennis) native to the Great Lakes region. 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Due to the nitrogen-fixing nodules L.polyphyllus changes the soil chemistry in favour of nitrogen-demanding 

species. Thus, L. polyphyllus causes a change in nutrient content of soil and, eventually, in plant communities. 

Eutrophication of nutrient-poor sites and consequent changes in community structure and diversity is the main 

problem when L. polyphyllus invades an area. 

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
542

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Lupine contamination of hay raises alkaloid content and may negatively impact the usefulness of hay as fodder and 

hence its value.

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 

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
543

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

BENEFICIAL EFFECT

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 

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 

Several cultivars are considered valuable garden plants. It has also been widely used as a ‘green fertilizer’ due to 

its ability to support nitrogen fixation. Low alkaloid cultivars have been developed for use as forage crops. 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 √

Not significantly 0 

Unknown U 

Several cultivars are popular garden plants. 

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

1 
544

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 √

Unknown U 

Lupinus polyphyllus extracts (from low alkaloid cultivars) are sold as ‘herbal medicines’. Lupine seeds (also from 

low alkaloid cultivars) are cultivated for the edible seeds. 

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 

Lupine absorbs radiation well and has been planted around Chernobyl for bioremediation. [source not confirmed]

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, 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
545

Scientific Name: Lycopus asper

Common Name: Western water horehound

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

Lycopus asper is found in industrialized areas, polluted habitats and other man made habitats. 

It is now frequent in the western Lake Erie area and local elsewhere in wet ground, especial disturbed shores and 

ditches (Reznicek et al. 2011). In a survey of fens in Ohio, Lycopus spp. Constituted less than 2% of vegetation 

cover (Barry et al. 2008).

Lycopus asper could pose a competitive threat to native species: L. americanus Muhl. Ex W. Bartram, L. 

amplectens Raf., L. rubellus Moench, L. uniflorus Michx., and L. virginicus L. (USDA NRCS 2012).

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 √

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 6
546

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Environmental Impact Total 0

Total Unknowns (U) 2

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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) 
547

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

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
548

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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

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 
549

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, 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) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
550

Scientific Name: Lycopus europaeus

Common Name: European water horehound

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Stammel et al. (2003) report that L. europaeus possess a chemical compound that may be effective against 

herbivores in the Great Lakes.

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

Lycopus europaeus invades numerous wetland ecosystems and is capable of displacing natives, such as: L. 

americanus Muhl. Ex W. Bartram, L. amplectens Raf., L. rubellus Moench, L. uniflorus Michx., and L. virginicus 

L. (USDA NRCS 2012).

In its native range European water horehound is a common, widespread species that can come to dominate in some 

ecosystems (Lucassen et al. 2006, van der Valk and Verhoeven 1988). 

A majority of seeds collected during a survey of moving bodies of water in the Netherlands were from L. europaeus. 

This species also had the highest germination rate of all the seeds collected (Boedeltje et al. 2003). 

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 √
551

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Hybridization between L. europaeus and L. americanus can occur when both species are living in close proximity. 

Hybrids have been found in North America; however, there are no records of hybrids in the Great Lakes (Reznicek 

et al. 2011).

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Environmental Impact Total 1

Total Unknowns (U) 3

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown
552

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Lycopus europaeus can be found in brick and concrete wall structures in urban environments (Francis and Hoggart 

2011). Over time these structures could weaken.

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
553

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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

Historically, L. europaeus has been used as an astringent, cosmetic, douche, narcotic, refrigerant and to treat fever, 

sores, and wounds.

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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 √
554

Not significantly 0 

Unknown U

Six isopimarane diterpeniods, which are frequently used in pharmaceuticals, have been isolated from L. europaeus 

(Hussein et al. 1999).

A diterpenoid isolated from L. europaeus, euroabienol, showed activity against 15 strains of bacteria and 6 fungal 

strains. Euroabienol has great potential to be used as a broad spectrum antibiotic and/or antifungal (Radulović et 

al. 2010). 

Gibbons et al. (2003) found that diterpenes from L. europaeus, when combined with other compounds, have 

potential at regulating bacteria that have resistance to multiple drugs.

Polar extracts from L. europaeus contain flavonoids and phenolic acids; both of which are antioxidants (López et al. 

2007). 

Another polyphenolic compound extracted exhibits the potential to influence the thyroid glands and gonads (Fecka 

and Cisowski 1999). 

Mild forms hyperthyroidism can be improved by taking extracts from L. europaeus (Beer et al. 2008, Wojciechowski 

et al. 2003). Patients who are given low doses of L. europaeus experience reduced levels of thyroid hormone and 

reduced cardiac symptoms (Vonhoff et al. 2006).

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 

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, 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

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
555

Scientific Name: Lysimachia nummularia L.

Common Name: moneywort

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Lysimachia spp. are susceptible to rust and leaf spots (Missouri Botantical Garden 2012).

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., critical reduction, extinction, behavioral 

changes) 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 

Lysimachia nummularia spreads quickly in moist ecosystems: floodplain forests, prairies, marshes, and swamps 

(IPANE 2013, Kennay and Fell 2011). 

This species forms dense mats of vegetation that excludes other herbaceous vegetation (IPANE 2013, Kennay and 

Fell 2011).

It may occupy the same niche as Lysimachia radicans, which is endangered in Indiana (Indiana Natural Hertiage 

Database 2011).

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)

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 √

This species is not a preferred food source for any mammal species, but rabbits and ground hogs may eat it 

occasionally (Kennay and Fell 2011).

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
556

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Populations of moneywort can clog small springs (IPANE 2013). 

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
557

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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 
558

Not significantly 0 √

Unknown U 

Historically it has been used as groundcover in the Northeast, but it quickly becomes a pest in gardens, pastures, 

and lawns (IPANE 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

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

This species has been used for ornamental purposes because the attractive yellow flowers of Lysimachia 

nummularia occasionally attract bees (Missouri Botanical Garden 2013).

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 
559

Unknown U 

Saponins taken from the roots of L. nummularia suppress cancer cells growing in the prostate, brain, and lungs 

(Podolak et al. 2013).

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 

Lysimachia nummularia is able to bioaccumulate mercury (Ribeyre and Boudou 1994).

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, 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
560

Scientific Name: Lysimachia vulgaris L.

Common Name: yellow loosestrife

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Lysimachia vulgaris is an unpatalable species that is avoided by large herbivores due to toxic compounds (Bossuyt 

et al. 2005).

Lysimachia spp. are susceptible to rust and leaf spots (Missouri Botanical Garden 2012).

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., critical reduction, extinction, behavioral 

changes) 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 Washington, yellow loosestrife has displaced native vegetation in wetlands and along streambanks and reduced 

habitat for waterfowl and fish (King County 2010). 

Yellow loosestrife has also been observed outcompeting purple loosestrife (Lythrum salicaria); a very problematic 

weed that is also found in the Great Lakes (State of Washington 2013). 

Bossuyt et al. (2005) observed that plant populations dominated by L. vulgaris had decreased total species richness 

compared to populations nominated by other invasive plant species.

It may occupy the same niche as Lysimachia radicans, which is endangered in Indiana (Indiana Natural Heritage 

Database 2011).

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)

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 √
561

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

It was also observed that when there was a majority of L. vulgarius present, palatable plant species produced 

significantly more inflorescences (Bossuyt et al. 2005).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

This species can also create dense communities which alter the local hydrology by clogging shallow waterways and 

increasing sedimentation (King County 2010).

Environmental Impact Total 2

Total Unknowns (U) 3

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2 Unknown
562

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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 6 
563

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

BENEFICIAL EFFECT

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 

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 

Lysimachia vulgaris has been used as a garden ornamental or for other landscaping purposes outside the Great 

Lakes (King County 2010). 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 
564

Unknown U 

Extracts taken from L. vuglaris contain many flavonoids; which have anti-oxidation properties (RzadkowskaBodalska and Olechnowicz-Stepień 1975). 

These flavanol glycosides are used in Chinese folk medicine to treat high blood pressure (State of Washington 

2013).

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

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, 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 

Lysimachia vulgaris is an unpatalable species that is avoided by large herbivores due to toxic compounds (Bossuyt 

et al. 2005).

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
565

Scientific Name: Lythrum salicaria

Common Name: Purple Loosestrife

Environmental: High

Socio-Economic: Low

Beneficial: Unknown

ENVIRONMENTAL IMPACTS

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

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

As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that 

provide a higher quality source of cover, food, or nesting sites for native wetland animals (U.S.EPA 2008).

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

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

Habitat and foraging is reduced for a number of wildlife species including birds and waterfowl, insects, and other 

semi-aquatic species, and in some cases reduced wildlife diversity in the community is documented (Blossey et al., 

2001, Malecki et al., 1993, Schooler et al., 2009, Whitt et al., 1999)

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 6
566

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Areas dominated by purple loosestrife (Fig. 2) show significantly lower porewater pools of phosphate in the summer 

compared to areas dominated by Typha latifolia L. (Templer et al., 1998).

Purple loosestrife leaves decompose quickly in the fall resulting in a nutrient flush, whereas leaves of native species 

decompose in the spring (Barlocher and Biddiscombe, 1996; Emery and Perry, 1996; Grout et al., 1997).

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

It has resulted in significant negative consequences for at least one native species

6

Yes, it has affected they physical ecosystem to some extent, but the alterations and resulting adverse 

effects have been mild

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Purple loosestrife causes annual wetland losses of about 190,000 hectares in the United States (Thompson et al. 

1987; Mal et al. 1997).

Change in timing of nutrient release to autumn, a time of little primary production, results in significant alterations 

of wetland function and could jeopardize detritivore consumer communities (Grout et al., 1997).

Environmental Impacts Total 9

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown
567

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 

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 6
568

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 

Economic Impact Total 0

Total Unknowns (U) 0

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL IMPACT

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

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

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

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
569

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 √

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, 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

Positive Impact Total 1

Total Unknowns (U) 1

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1
570

Scientific Name: Marsilea quadrifolia L.

Common Name: European waterclover

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 √

Marsilea quadrifolia is capable of outcompeting native aquatic and moist terrestrial species and creating monotypic 

vegetative stands (Benson et al 2004, Illinois Department 2013). 

These monospecific stands can also persist throughout the winter seasons because of the underground rhizomes 

(Benson et al. 2004). 

During the growing season M. quadrifolia plants are able to adjust the angle of the floating leaflets to optimize 

access to sunlight and the ability to photosynthesize (Kao and Lin 2010). This ability could allow this species to 

outcompete neighboring species for sunlight. 

The presence of M. quadrifolia in an aquatic ecosystem can also have an effect on molluscan communities (U.S EPA 

2008).

Other sources report that M. quadridfolia does not spread aggressively and poses a small ecological threat (Benson 

et al. 2004, Connecticut Aquatic 2006)

In a survey by Henry and Myers (1983), M. quadrifolia only migrated 151 feet per year Spring Creek (Illinois); for a 

total range expansion of 1 mile downstream in 35 years. 

The New York Invasive Species Council ranks this species as posing an unknown ecological threat (New York 

Invasive 2010). 

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)

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 

1 
571

have not been widespread or severe

Not significantly 0 

Unknown U √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

The native fern Marsilea vestita is endangered in Minnesota (Illinois Department 1996). 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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
572

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
573

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

BENEFICIAL EFFECT

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 

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 

European waterclover is commonly used in water gardens and aquariums (Campbell et al. 2010).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

Marsilea quadrifolia is an edible leafy plant with high crude protein content, but has a widely varying nutrient 

composition depending on the season it was harvested (Dewanji et al. 1993).

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

1 √
574

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0 

Unknown U 

Extracts from M. quadrifolia reduced the severity of seizures in rats (Sahu et al. 2012). 

This species also possesses compounds that may act as acytylcholinesterase and butyrylcholinesterase inhibitors; 

which could play a role in the management of Alzheimer’s disease (Bhadra et al. 2012). 

In a study conducted by Ripe et al. (2009), extracts from M. quadrifolia were found to have antibacterial, cytotoxic 

and antioxidant properties. These properties may be useful in antiproliferative, antitumor, and pesticidal 

applications (Meyer et al. 1982 in Ripe et al. 2009). 

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 

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, 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 

Marsilea quadrifolia is an edible leafy plant with high crude protein content, but has a widely varying nutrient 

composition depending on the season it was harvested (Dewanji et al. 1993).

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
575

Scientific Name: Mentha aquatica L.

Common Name: watermint

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 
576

Mentha aquatica can hybridize with M. spicata to result in Mentha X piperita (Gobert et al. 2002). 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
577

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
578

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Historically, mint species have been used for medicinal and culinary purposes (Ohio State University 2012).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 Jordan M. aquatica, in combination with other plant species, is used in numerous ways: as an expectorant, an 

astringent, a muscular relaxant for the uterus and arteries, a carminative, an antispasmodic, an antiepileptic, a 

narcotic, an antipyretic, a diaphoretic, a cathartic, a hypnotic, an anal gesic, an antineuralgic, an antiarthritic, an 

antirheumatic, and an antitussive (Al-Qura'n 2007).

Extracts taken from M. aquatica have shown to have selective antiproliferative activity on breast cancer, as well as 

neurochemical properties that may have medicinal purposes (Conforti et al. 2008, López et al. 2010). 

Essential oils derived from M. aquatica have antimicrobial activity (Mimica-Dukić et al. 2003). 

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 
579

Not significantly 0 √

Unknown U 

Mentha aquatica may also be able to uptake lead from its surrounding environment; depending on the local pH 

(Saygideger and Dogan 2005).

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, 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
580

Scientific Name: Mentha gracilis

Common Name: gingermint 

Environmental: Unknown

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √
581

As a hybrid of the native wildmint (M. arvensis), gingermint has the potential to impact wildmint populations. 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
582

Handling plant may cause skin irritation or allergic reaction; (http://www.misin.msu.edu/facts/detail.php?id=96)

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Known to carry or be susceptible to more than 20 plant viruses, including viruses such as strawberry latent ringspot 

viris (SLRSV), alfalfa mosaic, cucumber mosaic, tobacco mosaic, and tomato spotted wilt which are pests on other 

crops (Tzanetakis et al 2010b) Potential effects to these other susceptible crops is unknown. 

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 

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
583

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Widely grown essential oil crops in more northern latitudes (Zheljazkov et al 2010) 

Scotch spearmint is derived from a cross between field mint (Mentha arvensis L.) and native spearmint and has 

organoleptic properties slightly different to that of native spearmint - scotch spearmint has 20% limonene of the 

total oil and native spearmint has only 8% limonene. (Poovaiah et al. 2006)

In the United States, the cultivated area for mint is about 50,000 ha, with spearmint (M. spicata and M. gracilis) 

representing 20% of the production area and the crop value. Oregon and Washington are the largest producers 

followed by Idaho, Indiana, Wisconsin, and Michigan. (Tzanetakis et al 2010b) The USDA (2008) estimates the 

direct value of the spearmint oil crop at $24 million. 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 √

Not significantly 0 

Unknown U 

Many cultivars are available to gardeners/hobbyist. The flowers attract many different kinds of butterflies and bees 

and it is a beautiful addition to any garden.” (http://bygl.osu.edu/content/vegetable-mint-mentha-spp)

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 
584

“Mint has been used for thousands of years for anything from medicinal wraps to talismans that scare away 

demons. Today it is commonly used in cooking and tea for its distinctive flavor and calming scent” 

(http://bygl.osu.edu/content/vegetable-mint-mentha-spp)

Menthol is a mint product.

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 √

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, 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 13

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
585

Scientific Name: Mentha spicata

Common Name: spearmint

Environmental: Unknown

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √
586

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
587

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
588

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

The plant repels insects and was formerly used as an strewing herb. Rats and mice intensely dislike the smell of 

mint. PlantLife.org, 2013

The three major pure constituents extracted from the M. spicata leaf EO were also tested individually against three 

mosquito larvae. The LC(50) values of carvone, cis-carveol, and limonene appeared to be most effective against A. 

stephensi (LC(50) 19.33, 28.50, and 8.83 ppm) followed by A. aegypti (LC(50) 23.69, 32.88, and 12.01 ppm), and C. 

quinquefasciatus (LC(50) 25.47, 35.20, and 14.07 ppm). The results could be useful in search for newer, safer, and 

more effective natural larvicidal agents against C. quinquefasciatus, A. aegypti, and A. stephensi. (Govindarajan 

2012)

The oils of R. officinalis, M. spicata, and O. majorana showed strong repellency against the ticks. (El-Seedi 2012)

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 the United States, the cultivated area for mint is about 50,000 ha, with spearmint (M. spicata and M. gracilis) 

representing 20% of the production area and the crop value. Oregon and Washington are the largest producers 

followed by Idaho, Indiana, Wisconsin, and Michigan. (Tzanetakis et al 2010b) The USDA (2008) estimates the 

direct value of the spearmint oil crop at $24 million. 

“Grown commercially for the essential oil, which is used in gum.” (New Mexico State University) 

An essential oil is obtained from the whole plant. The oil is used commercially as a flavoring for toothpaste and 

confectionery, and is sometimes added to shampoos and soaps.

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 √

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 

Unknown U 

Many cultivars are available to gardeners/hobbyist. The flowers attract many different kinds of butterflies and bees 

and it is a beautiful addition to any garden.” (Ohio State University 2013)

“Herb gardens. Naturalize as a ground cover in moist informal areas such as pond/water garden margins or low 

open woodland areas.’ (Missouri Botanical Gardens 2013)

The leaves of spearmint are edible raw or cooked. Having a strong spearmint flavor, they are used as a flavoring in 

salads or cooked foods. Spearmint leaves can be used whole, chopped, dried and ground, frozen, preserved in salt, 

sugar, sugar syrup, alcohol, oil, or dried. The leaves lose their aromatic appeal after the plant flowers. They are 

best dried by cutting just before, or right as the flowers open, about 1/2 to 3/4ths the way down the sock (leaving 
589

smaller shoots room to grow). There is some dispute as to what drying method works best, some prefer different 

materials (such as plastic or cloth) and different lighting conditions (such as darkness or sunlight). The leaves are 

often used in 'mint sauce', which is used as a flavoring in meals. A herb tea is made from the fresh or dried leaves. It 

has a very pleasant and refreshing taste of spearmint, leaving the mouth and digestive system feeling clean. An 

essential oil from the leaves and flowers is used as a flavoring in sweets, ice cream, drinks etc. It has a spearmint 

flavor. (PlantLife.org, 2013)

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 

“Mint has been used for thousands of years for anything from medicinal wraps to talismans that scare away 

demons. Today it is commonly used in cooking and tea for its distinctive flavor and calming scent” (Ohio State 

University 2013)

Menthol is a mint product.

Spearmint is a commonly used domestic herbal remedy. A tea made from the leaves has traditionally been used in 

the treatment of fevers, headaches, digestive disorders and various minor ailments. The herb is antispasmodic, 

urine-inducing, restorative, stimulant, and has agents that prevent vomiting, that relieve and remove gas from the 

digestive system, and give tone and strength to the stomach.

Spearmint also stops gonorrhoea, fluor albus and immoderate flow of the period. A cataplasm of the green leaves 

applied to the stomach, is said to prevent vomiting, and to women's breasts prevents hardness and curdling of milk. 

Two or three drops of oil can be taken on a lump of sugar for flatulence. Adding eight drops of the oil to 1 pt (568 

ml) of water makes Aqua menthae, or Mint Water, which can be given to babies with colic. The infusion of 1 oz (28 

g) of dried herb to 1 pt (568 ml) of boiling water is also said to be excellent for nausea and wind. PlantLife.org,

2013

Further studies are needed to test the reliability of these results and the availability of spearmint as a drug for 

hirsutism. (Akdogan 2007)

M. spicata or M. × piperita essential oils are safe and effective for antiemetic treatment in patients, as well as being 

cost effective (Tanyarani-Najaran 2013)

The essential oils obtained from Foeniculum vulgare, Mentha piperita and M. spicata, O.cimum basilicum, 

Origanum majorana, O. onites, O. vulgare, and Satureja cuneifolia as well as common essential oil components have 

shown notable inhibitory effects against 10 isolated strains of illness producing microorganisms. (Orhan 2011

Spearmint (Mentha spicata L.) essential oil has an antifungal effect on Fusarium oxysporum f. sp. radiciscucumerinum the causal agent of stem and crown rot of greenhouse cucumber (Nosrati 2011)

the flower hexane extract obtained from M.spicata associated with M. rotundifolia presents an antineoplastic 

activity against KB and MCF-7, and an antiproliferative effect at a high concentration toward NIH 3T3 

[experimental cancer cell lines]. (Begnini 2012)

The majority of the tested essential oils exibited considerable inhibitory capacity against all the organisms tested, as 

supported by growth inhibition zone diameters, MICs and MBC's. Thyme, coriander and basil oils proved the best 

antibacterial activity, while thyme and spearmint (Mentha spicata) oils better inhibited the fungal species. 

(Lixandru 2010)

Extracts of Mentha spicata have shown XO inhibtory activity, suggesting that they may be useful in the treatment of 

gout (Hudaib 2011)

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 
590

Unknown U 

Spearmint (Mentha spicata) extracts contained a compound that induced cometabolism of a PCB (Gilbert and 

Crowley, 1997).

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, 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 20

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
591

Scientific Name: Myosotis scorpiodes

Common Name: True forget-me-not

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

This species contains pyrrolizidine alkaloids that are toxic to mammals and can cause weight loss, poor body 

condition, and liver disease (DiTomaso and Healy 2007). 

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., critical reduction, extinction, behavioral 

changes) 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 √

Competes with native plants in wet areas (Ling 2010) and can form large monocultures (Mehrhoff et al. 2003); 

therefore, it has the potential to significantly reduce populations of native plant species, and it may change the 

density of vegetation.

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)

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 

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 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 
592

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

Myosotis has been documented to hybridize with other members of the genus, but it is not known whether or not it 

will hybridize with the natives Myosotis laxa (listed as endangered in Indiana), Myosotis macrosperma, or Myosotis 

verna.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
593

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
594

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Cultivated as an ornamental plant.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

The nectar and pollen attract pollinating insects (Plants for a Future 2010).

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 

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 
595

Not significantly 0 √

Unknown U 

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, 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 

Plants provide additional habitats for aquatic, winged insects (Ling 2010). 

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
596

Scientific Name: Myosoton aquaticum

Common Name: water chickweed 

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
597

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
598

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
599

1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Young leaves and stems are edible if cooked, but not of commercial value.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

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, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6 
600

Yes, it provides some positive contribution to the ecosystem, but is not vital 1 

Not significantly 0 √

Unknown U 

The nectar of the flowers attracts small bees and Syrphid flies; some bees may collect pollen, while flies 

occasionally feed on pollen. The caterpillars of several moth species probably feed on the foliage, like other 

chickweeds. The seeds of chickweeds are attractive to sparrows and other birds, while the foliage is eaten by 

rabbits. Because Water Chickweed frequently occurs in wetland habitats, its foliage is probably eaten by the 

Canada goose.

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
601

Scientific Name: Myriophyllum spicatum L.

Common Name: Eurasian watermilfoil

Environmental: High

Socio-Economic: High

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Myriophyllum spicatum populations and stagnant water also create habitat for the parasites that cause swimmer’s 

itch and mosquitoes (Jacobs and Margold 2009, OISAP 2013). 

In lab experiment, polyphenolic allelochemicals taken from M. spicatum, inhibited the growth of green algae and 

cyanobacteria; such as Microcystis aeruginosa (Leu et al. 2002, Nakai et al. 2012). 

In studies in Finland, chemicals secreted by M. spicatum caused high mortality (73% to 89%) of the mysids

Neomysis integer and Praunus flexuosus (Lindén and Lethiniemi 2005).

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., critical reduction, extinction, behavioral 

changes) 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 

This species is tolerant of low water temperatures and begins to photosynthesize and grow early in the spring 

(IISCTC 2007, MISIN and MNFI 2013). This growth habit allows M. spicatum to reach the water’s surface before 

native plants and create a dense canopy to out-compete for sunlight and space (IL DNR 2009, Madsen et al. 1991, 

MISIN and MNFI 2013). This advantage allows Eurasian milfoil to form dense beds with stem densities in excess of 

300/m2 in shallow water; essentially excluding other plant species (Aiken et al 1979).

Although in small tank experiments the native northern watermilfoil (Myriophyllum sibiricum) appears 

competitively superior, in the field, however, M. spicatum has replaced M. sibiricum over much of the temperate 

range of this species in North America (Valley and Newman 1998).

Suppression of native plant communities in the field can happen in only a few years (GLIFWC 2006).

Myriophyllum spicatum has difficulty becoming established in existing populations of native plants (IL EPA 1996, 

Michigan Sea Grant 2012). This species thrives in waterbodies that have experienced a disturbance: nutrient 

loading, intense plant management (i.e. yard management on private property), heavy recreational use, and/or 

fluctuating water levels (Benson et al. 2004, IL DNR 2009, Swearingen et al. 2002).

Myriophyllum spicatum is found in hundreds of Michigan inland lakes (Michigan Sea Grant 2007). 

The Minnesota Sea Grant states that Eurasian watermilfoil is not problematic in ecosystems with sandy or low 

sediment fertility (Jensen 2010). 
602

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)

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 

Keast (1984) found that stands of Eurasian watermilfoil in lakes in Ontario had reduced abundance and diversity of 

aquatic insects and other benthic macroinvertebrates compared to native communities. 

Keast (1984) also found that there were 3-4 times as many fish feeding in native plant communities than in beds of

M. spicatum. 

Dense cover allows high survival rates of young fish; however, larger piscivorous fish lose foraging space and are 

less efficient at obtaining their prey (Lillie and Budd 1992). 

Madsen et al. (1995) found growth and vigor of a warm-water fishery reduced by dense Eurasian watermilfoil 

cover. 

Myriophyllum spicatum also has less value as a food source for waterfowl than the native plants it replaces (Aiken 

et al. 1979). 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Myriophyllum spicatum is capable of hybridizing with the native M. sibiricum to produce M. sibricum X spicatum 

which has an intermediate number of leaf segments between the two parent species (Reznicek et al. 2011). 

These hybrids have been found in Wisconsin (Moody and Les 2002, Ortenblad et al. 2006). 

Any hybrid of M. spicatum and a native milfoil could create a more aggressive species of invasive plant (Lui et al. 

2010).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Altered hydrology (caused by M. spicatum) can result in decreased dissolved oxygen levels and it can alter 

temperature and pH of the surrounding water (Engel 1995, GLIFWC 2006, Jacobs and Margold 2009)
603

Myriophyllum spicatum communities also impact nutrient cycling by uptaking phosphorus from the sediments and 

releasing them during fall senescence; which could contribute to eutrophication of ponds and lakes (GLIFWC 2006, 

Jacobs and Margold 2009).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Large infestations of M. spicatum can also alter the hydrology of waterbodies and even create stagnant waters 

conditions (OISAP 2013). 

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Myriophyllum spicatum populations and stagnant water also create habitat for the parasites that cause swimmer’s 

itch and mosquitoes (Jacobs and Margold 2009, OISAP 2013).

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

AND/OR

1 √
604

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U 

Dense mats of M. spicatum can reduce water flow or clog agricultural, residential, industrial, and/or power plant 

water intakes; removal from these structures can be expensive (IL DNR 2009, Jacobs and Margold 2009).

Property owners, lake associations, and local governments incur costs to keep boat channels clear and the disposal 

of M. spicatum (Bowen 2010). 

Waterfront property owners in Michigan spend an estimate $20 million annually to control aquatic invasive 

plants—primarily Eurasian watermilfoil and curly lead pondweed ( Michigan Sea Grant Coastal Program 2007). 

In New York, annual costs of control of Eurasian watermilfoil are estimated at $500,000 (Johnson and Blossey 

2003).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Given the reduction in recreational access and aesthetics associated with large, obstructive populations of M. 

spicatum, the values of nearby property could decline (Bowen 2010, IL DNR 2009). 

According to an economic study conducted in New Hampshire, the value of property adjacent to waterbodies with 

large submerged aquatic plants was reduced by 15% or more (Halstead et al. 2003 in RICRMC 2007).

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 

Even with control efforts, large infestations of M. spicatum can severely limit recreational activities such as boating, 

fishing, swimming, and/or waterfowl hunting (IL DNR 2009, Jensen 2010). 

Long stems can get tangled around boat propellers and may cause damage (IL EPA 1996). 

It is estimated that Eurasian watermilfoil costs Michigan millions of dollars annually in lost tourism revenue 

(Michigan Sea Grant 2012).

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 

Large populations of Eurasian watermilfoil are often found to be aesthetically unpleasant (IL DNR 2009).
605

Socio-Economic Impact Total 10

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

BENEFICIAL EFFECT

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 

Myrophyllum spicatum is one of the few species that is capable of shading out the invasive curly pondweed, 

Potamogeton crispus (Aiken et al. 1979). 

Myriophyllum spicatum is also known to inhibit the growth of cyanobacteria; which are responsible for causing 

harmful algal blooms (Nakai et al 2012). 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
606

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 

If concentrations of nitrate are high, M. spicatum can absorb nitrogen from the sediments or the water (Best and 

Mantai 1978). This ability could help improve water quality for those waterbodies affected by fertilizer runoff. 

Myriophyllum spicatum is able to uptake moderate amounts of cadmium, zinc, copper, lead, and selenium from its 

environment and store it in its leaves (Fawzy et al. 2012, Mechora et al. 2013). This species could be used in 

remediation efforts where the plants are grown in contaminated water and harvested before the leaves can break 

down and release the contaminants. 

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, 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 

Freshwater crustaceans and bass can utilize stands of M. spicatum for habitat and cover (Jacobs and Mangold 

2009). 

Dense mats of Eurasian watermilfoil can support the weight of frogs and wading birds (Aiken et al. 1979). 

Eurasian watermilfoil can grow in adverse conditions (high nutrients/pollution or high traffic areas) that native 

submerged species cannot tolerate (Benson et al. 2004, GLIFWC 2006). 

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
607

Scientific Name: Najas marina L.

Common Name: spiny naiad

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

Najas marina is found throughout the Great Lakes and is considered to be a nuisance threat to the ecosystem (U.S. 

EPA 2008). 

In the 1940s, this species was replacing other plants species in Michigan lakes (Wentz and Stuckey 1971).

About a third of the N. marina seeds by mallard ducks are viable after passing through the digestive track, which 

means a single duck can carry viable seeds 100-200 km per day (Agami and Waisel 1986).

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)

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 √

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 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 1 
608

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 1 
609

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

Large infestations of Najas marina can sometimes interfere with recreational boating and fishing (U.S. EPA 2008).

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
610

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 √

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 
611

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, 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 

Mallard ducks and 18 other types of waterfowl eat the seeds of many Najas spp. (Agami and Waisel 1986, Tarver et 

al. 1986). 

The seeds of N. marina are also eaten by fish such as tilapia, grass carp and common carp (Agami and Waisel 

1988).

Beneficial Effect 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
612

Scientific Name: Najas minor All.

Common Name: brittle waternymph

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Unknown

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

Brittle waternymph starts growing early in the season, which often leads to the block the sunlight from reaching 

native species and inhibiting their growth (Ohio EPA 2001, Robinson 2004). 

This species can also out-compete nearby plants for space (Office of Water Resources 2010).

Najas minor grows aggressively in shallow waters and has formed dense, monospecific stands in the shallow waters 

of Lake Erie (Reznicek et al. 2011, U.S. EPA 2008).

Najas minor can also form dense underwater meshes with other exotic species such as Hydrilla verticillata (Kay and 

Hoyle 1999).

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)

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 √

These dense plant communities can produce unfavorable conditions for to fish and waterfowl (Kay and Hoyle 1999, 

Office of Water Resources 2010).

Animals may also be driven out of N. minor dominate ecosystems if they are dependent on the displaced native 

vegetation for survival (Robinson 2004).
613

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

As dense mats of brittle waternymph die and decompose, the amount of oxygen in nearby water and sediment maybe 

be significantly decreased (Robinson 2004). In extreme cases, anoxic conditions can lead to fish kills (Robinson 

2004).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Although, this species typically invades shallow water, in North Carolina dense shoals of N. minor have grown in 

waters up to 4 meters deep (Kay and Hoyle 1999). 

Dense populations of brittle waternymph have increased sedimentation rates and clogged waterways in 

Massachusetts (Robinson 2004).

Environmental Impact Total 3

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
614

1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Najas minor populations can reduce the discharge capacity (quantity of water) of channels (WI DNR 2010).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 
615

Dense stands of N. minor can hinder recreational activities such as, boating, fishing, and/or swimming (Office of 

Water Resources 2010, U.S. EPA 2008, WI DNR 2010). 

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 

Along with reduced recreational ability, populations of brittle waternymph can also diminish the aesthetic value of 

the surrounding areas (WI DNR 2010).

Limited recreational use and a decline in aesthetic value associated with large N. minor infestations can lead to 

reduced property values around the effected waterbody (Robinson 2004).

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

BENEFICIAL EFFECT

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 √

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 
616

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 

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 √

Najas minor is tolerant of adverse growing conditions including increased turbidity, eutrophic ecosystems, and 

some pollution (Wentz and Stuckey 1971, WI DNR 2010).

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, 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 

Mallard ducks and 18 other types of waterfowl eat the seeds of many Najas spp. (Agami and Waisel 1986, Tarver et 

al. 1986).

Beneficial Effect 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
617

Scientific Name: Nasturtium officinale W.T. Aiton

Common Name: Watercress

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Newman et al. (1992) found that watercress produces a chemical defense that deters generalist feeders such as the 

amphipod Gammarus pseudolimnaeus, the caddisflies Hesperophylax designates and Limnephilus spp., and the 

physid snail Physella spp. (Newman et al. 1992).

Nasturtium officinale can host the Spongospora subterranea (crook root fungus) and yellow spot virus (Walsh and 

Phelps 1991). 

Cabbage black-ringspot versus and the cucumber mosaic virus has been found on cultivated populations of 

Nasturtium officinale (Howard and Lyon 1952).

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., critical reduction, extinction, behavioral 

changes) 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 

Water cress is able to take up large amounts of nitrate from water bodies it lives in (Howard-Williams et al. 1982).

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)

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 √

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
618

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Nasturtium officinale can hybridize with N. microphyllum Boenn. ex Rchb, another invasive found in the Great 

Lakes, to produce the hybrid N. X sterile (Airy Shaw) Oefelein (Bleeker et al. 1999). 

However, this hybrid only produces viable seeds when the female parent is N. mircophyllum (Howard and Lyon 

1952). 

The sterile hybrid can still propagate and expand vegetatively (Reznicek et al. 2011). 

Observations of this hybrid species in Germany found that N. x sterile is more rigorous and is quicker at 

establishing itself from cuttings than either parent species (Bleeker et al. 1999). 

Nasturtium X sterile individuals have been found in Wisconsin Robert W. Freckman Herbarium 2012). 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Watercress if able to uptake large amounts of nitrate from water bodies it lives in (Howard-Williams et al. 1982).

The nitrogen is released when the plants die and decompose; however, if the plants are removed (as is the goal with 

most invasive species) this could alter the amount of nitrogen available (Howard-Williams et al. 1982).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Watercress can grow into large mats in slow parts of streams, typically in the bends and curves of the steam’s path. 

If populations get big enough, they could contribute significantly to the meanders of the stream (Kullberg 1974). 

However, Benson et al. (2004) found that this species causes minimal impact on natural communities in the 

Northwest region of the United States (Benson et al. 2004). 

Environmental Impact Total 1

Total Unknowns (U) 3
619

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Watercress can also host Fasciola hepatica, common live fluke (CDC 2013). People can become infected by eating 

raw watercress contaminated with fluke larvae (CDC 2013).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
620

Nasturtium officinale can host the crook root fungus, yellow spot virus, cabbage black-ringspot virsus, and the 

cucumber mosaic virus (Howard and Lyon 1952, Walsh and Phelps 1991). If watercress is growing near cultivated 

lands, these viruses could infect and damage crops. 

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 

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

BENEFICIAL EFFECT

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 

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 

Nasturtium officinale can be eaten raw, has high concentrations of vitamins and minerals, and has a peppery flavor 

(Benson et al. 2004, Robert W. Freckman Herbarium 2012, State of Washington 2013). 
621

This species is harvested recreationally and grown commercially in the United States (CANSWP 2006, State of 

Washington 2013). 

People can become infected by eating raw watercress contaminated with fluke larvae (CDC 2013).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 √

Not significantly 0 

Unknown U 

Nasturtium officinale can be eaten raw, has high concentrations of vitamins and minerals, and has a peppery flavor 

(Benson et al. 2004, Robert W. Freckman Herbarium 2012, State of Washington 2013). 

This species is harvested recreationally and grown commercially in the United States (CANSWP 2006, State of 

Washington 2013). 

People can become infected by eating raw watercress contaminated with fluke larvae (CDC 2013).

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 

Watercress has been used an herbal remedy for a variety of ailments: common cold; sore throat; earache; improve 

heart, kidney, and respiration health; the juice has been used to heal skin sores and acne (Robert W. Freckman 

Herbarium 2012). 

Nasturtium officinale has potent anti-oxidative properties and may have applications in the prevention of free 

radical-related diseases (Bahramikia and Yazdanparast 2010). 

Gill et al. (2007) found that consumption of watercress may lead to decreased damage to DNA and increased 

carotenoid concentrations; ultimately reducing the risk of cancer. 

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 test sites monitored by Redding et al. (1997), N. officinale was able to significantly reduce the concentrations of 

ammonia-N, nitrate-N and phosphorus in the wastewater. Effective treatment was dependent on harvesting the plant 

biomass (Redding et al. 1997). 

Nasturtium officinale is able to withstand the stress and accumulate moderate amounts of arsenic, nickel, and lead 

(Duman and Ozturk 2010, Keser and Saygideger 2010, Ozturk et al. 2010). 

A year after the closure of a paper mill on a stream in Michigan, this species was one of a few found growing 

downstream of the polluted site (Kullberg 1974). 

This ability to uptake nutrients and contaminants make N. officinale a possible candidate for use in 

phytoremediation or wastewater treatment operations. 

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, or commercially valuable)?
622

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 

In Washington, watercress was reportedly eaten by ducks, muskrats, and deer (Robert W. Freckman Herbarium 

2012). 

Newman et al. (1992) found that watercress produces a chemical defense that deters generalist feeders such as the 

amphipod Gammarus pseudolimnaeus, the caddisflies Hesperophylax designates and Limnephilus spp., and the 

physid snail Physella spp. (Newman et al. 1992).

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
623

Scientific Name: Nymphoides peltata (S.G. Gmel.) Kuntze

Common Name: yellow floating heart

Environmental: Moderate

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

These areas of stagnant waters (created by N. peltata) can be an ideal location for mosquitos to breed (OISAP 

2013).

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., critical reduction, extinction, behavioral 

changes) 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 

Nymphoides peltata can form dense floating mats of vegetation that block sunlight from reaching native plants and 

algae (IL DNR 2005, Lui et al. 2010, OISAP 2013).

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)

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 

Depending on the extent of the yellow floating heart population, the algae population could decline and disrupt the 

food web (Kelly and Maguire 2009).

The reduction in native plant species degrades the habitat and may reduce access to food for fish and wildlife (IL 

DNR 2005, OISAP 2013)

If the population of yellow floating heart is large enough, fish and other wildlife may be forced to relocate (CEH 

2004). 
624

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dense stands of N. peltata can cause slow-moving water to become stagnant and the water beneath the mats to have 

a low oxygen concentration (DiTomaso and Healey 2003, IL DNR 2005, Lui et al. 2010, WI DNR 2012).

Dense surface mats of N. peltata can hinder the air exchange between the water’s surface and the atmosphere (Kelly 

and Maguire 2009).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dense stands of N. peltata can cause slow-moving water to become stagnant... (DiTomaso and Healey 2003, IL 

DNR 2005, Lui et al. 2010, WI DNR 2012).

In large populations of yellow floating heart, sedimentation levels increase and could alter nearby hydrology (Kelly 

and Maguire 2009).

In New England, dense stands of N. peltata have blocked waterways (IPANE 2013). 

Environmental Impact Total 4

Total Unknowns (U) 1

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
625

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

These areas of stagnant waters (created by N. peltata) can be an ideal location for mosquitos to breed (OISAP 

2013).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

The reduction in aesthetic and recreational value can lead to a decline in nearby waterfront property (Kelly and 

Maguire 2009).

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

damage, decline of recreational species)?
626

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 locations outside the Great Lakes, dense mats of yellow floating heart have interfered with or even prevented 

recreational boating, canoeing, angling, water skiing, and swimming (CEH 2004, Lui et al. 2010, WI DNR 2012).

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 reduction in aesthetic and recreational value can lead to a decline in nearby waterfront property (Kelly and 

Maguire 2009).

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

BENEFICIAL EFFECT

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 

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 

Nymphoides peltata is a popular ornamental plant for outdoor water gardens and is easily purchased via the 

internet or by mail-order (Benson et al. 2004, IL DNR 2005, OISAP 2013).

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 6 
627

tourism

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

Nymphoides peltata has the ability to move nitrogen and phosphorus up from the sediment into the aboveground 

biomass and back down into the root structure during the winter. This ability regenerates the nitrogen and 

phosphorus levels in the sediment (Brock et al. 1983).

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, 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
628

Scientific Name: Pluchea odorata var. odorata (L.) Cass.

Common Name: marsh fleabane 

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low 

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 
629

Pluchea odorata is capable of hybridizing with P. indica to produce Pluchea X fosbergii (Cooperrider and Galang 

1965).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √
630

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
631

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

The leaves and stems of P. odorata have been used medicinally in Africa and India (King-Jones 2001). 

Extracts of P. odorata have been shown to heal wounds, reduce inflammation, and inhibit the growth of cancer cells 

(Gridling et al. 2009, Seelinger et al. 2012). 

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 
632

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, 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
633

Scientific Name: Pluchea odorata var. succulent (Fernald) Cronquist

Common Name: sweetscent

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 

Pluchea odorata var. succulenta has invaded high marsh ecosystems in New York (Lamont and Stalter 1991).

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 
634

Unknown U 

Pluchea odorata is capable of hybridizing with P. indica to produce Pluchea X fosbergii (Cooperrider and Galang 

1965).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 
635

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
636

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

The leaves and stems of P. odorata have been used medicinally in Africa and India (King-Jones 2001). 

Extracts of P. odorata have been shown to heal wounds, reduce inflammation, and inhibit the growth of cancer cells 

(Gridling et al. 2009, Seelinger et al. 2012). 

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 
637

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, 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
638

Scientific Name: Poa trivialis

Common Name: rough-stalked meadow grass

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
639

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
640

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

Considered a nuisance species in turfgrass (e.g.,fairways, sports fields).

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
641

1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Widely planted as a pasture grass. It is used for forage hay and pasturage in marshlands.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

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, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6 
642

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
643

Scientific Name: Polygonum persicaria

Common Name: Lady’s thumb, smartweed, spotted knapweed 

Environmental: Unknown

Socio-Economic: High

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 √

P. persicaria competes with natural vegetation, particularly in moist areas along ditches, streams, rivers, and 

marshes.

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)

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 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 
644

Not significantly 0 

Unknown U √

Several Polygonum species are native to the Great Lakes region, but information on potential hybridization is not 

readily available.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Stands can slow water flow in canals and streams (DiTomaso and Healy 2003)

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 1 
645

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

Common name ‘smart weed’ reflects that this plant contains a chemical compound which causes a burning 

sensation and mild irritation.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 √

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U 

The economic impact of P. persicaria in agricultural production is sufficient for various governments to declare this 

weed as a noxious pest (Anon., 1996; Anon., 2003). The state of Minnesota in the USA has declared P. persicaria as 

a secondary noxious weed and several states have categorized it as invasive (USDA-NRCS, 2002).

P. persicaria can be very competitive with crop plants, particularly in moist soils and as such can have significant 

economic impacts in the requirements for use of increased tillage and herbicides, though exact data on costs due to 

the presence of this species are not known. Holm et al. (1997) note that it is a weed of 35 crops in 50 countries.

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 

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 
646

Yes, but negative consequences have been small 1 

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

BENEFICIAL EFFECT

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 

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 

leaves and young shoots may be eaten, but not grown commercially for this purpose.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 
647

Contains persicarin. persicarin should be viewed as a candidate therapeutic for the treatment of severe vascular 

inflammatory diseases, such as, sepsis or septic shock. (Kim et al 2013).

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 

Has been demonstrated to removed >60% of nitrite from ground and surface water, however other aquatic 

macrophytes are available which are even more efficient at nitrite remediation (Rawat et al 2012). 

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, 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 

Seeds are important food sources for many birds and mammals (DiTomaso and Healy 2003).

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
648

Scientific Name: Potamogeton crispus L.

Common Name: curlyleaf pondweed

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

Potamogeton crispus is tolerant of many ecological conditions (low/high nutrients, slow/fast water flow, low/high 

temperatures, low/high light) and can invade numerous aquatic ecosystems (CEH 2004, Group 2006, Guard 1995). 

Curlyleaf pondweed germinates in the fall and survives the winter (IPANE 2013). This growth habit, along with 

tolerance of low light and low water temperatures, allows curlyleaf pondweed to begin growing in the spring before 

native plant species (IPANE 2013, WIDNR 2012).

Potamogeton crispus can outcompete native species for light and space early in the growing season; often reducing 

plant diversity by forming monocultures (ENSR International 2005, PA DCNR n.d., WI DNR 2012). 

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)

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 

Dense stands of curlyleaf pondweed can alter the predator/prey relationship and affect the overall ecology of an 

aquatic ecosystem (ENSR International 2005).

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
649

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Potamogeton xcooperia is a hybrid between P. crispus and P. perfoliatus, which is also found in the Great Lakes., 

has been found in Europe (Kaplan and Fehrer 2004).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

When dense stands of curlyleaf pondweed die off midsummer, it can have a drastic effect on the water quality. A 

large amount of phosphorus is released into the water which can lead to eutrophic waters and possible algal blooms 

(Benson et al. 2004, PA DCNR n.d., WI DNR 2012). 

As the vast quantity of plant matter decomposes, the concentration of oxygen in the water can drop significantly and 

possibly impact fish (IPANE 2013, Lui et al. 2010).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Large infestations of P. crispus can impede water flow and cause stagnant water conditions (Catling and Dobson 

1985 in ENSR International 2005, Lui et al. 2010).

Environmental Impact Total 5

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
650

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Waterfront property owners in Michigan spend an estimated $20 million annually to control aquatic invasive 

plants—primarily Eurasian watermilfoil and curlyleaf pondweed (MSGCP 2007).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Decomposing mats of curlyleaf pondweed release phosphorus; which can cause an increase in algal blooms and 

effect drinking water quality (WI DNR 2012). 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dense growth of P. crispus can reduce the flow in irrigation canals (Catling and Dobson 1985 in ENSR 

International 2005). 
651

Expensive control programs are often needed to reduce the impacts on recreational activities and to maintain 

waterfront property values (IL DNR 2005).

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 

Surface mats of P. crispus can become a nuisance and inhibit aquatic recreation such as boating, fishing, and 

swimming (ILDNR 2009, Jensen 2009, PA DCNR n.d.).

Dense colonies of curlyleaf pondweed can restrict access to docks and fishing areas until July, when the plants 

dieback (Jensen 2009).

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 

Dead mats of P. crispus can pile up along the shoreline; greatly reducing the aesthetic value of waterfront property 

(WI DNR 2012).

Socio-Economic Impact 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

BENEFICIAL EFFECT

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 

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 
652

Not significantly 0 √

Unknown U 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Aqueous extracts of P. crispus demonstrated antimicrobial activity against 17 different microorganisms including

Escherichia coli and Staphylococcus aureus (Fareed et al. 2008). 

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 

Potamogeton crispus is able to remove dibutyl phthalate and phthalic acid esters when grown experimentally in 

contaminated water (Chi and Cai 2012, Chi and Yang 2012). 

Experiments conducted in China showed that P. crispus is able of removing nitrogen from eutrophic water and 

sediment; thus improving the water quality (Ren et al. 2011). 

Curlyleaf pondweed is able to uptake cerium, cobalt, cesium, and their isotopes; indicating that it could be used to 

treat low level liquid radioactive waste (Hafez et al. 1992). 

This species is also able to remove cadmium from water, but at the cost of decreased photosynthesis (Sivaci et al. 

2008). 

Populations of P. crispus have no effect on dissolved oxygen concentrations, slightly increase the pH and reduce the 

total dissolved solids and the nitrogen concentration; leading to an overall improvement in water quality (Wang et 

al. 2011).

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, 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 

Curlyleaf pondweed provides habitat for aquatic life when native plants are not present in the winter and early 

spring (IL DNR 2005). 

Populations provide habitat for macroinvertbrates, which are food sources for fish and waterfowl on their northern 

migration (Catling and Dobson 1985 in ENSR International 2005, GLC 2006). 
653

Beds of P. crispus also provide spawning substrate and habitat for game fish (GLC 2006, Lembi 2003).

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
654

Scientific Name: Puccinellia distans

Common Name: reflexed salt grass 

Environmental: Low

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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., critical reduction, extinction, behavioral 

changes) 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 

Appears to outcompete native grasses only in areas of salt contamination.

Puccinellia seedlings are described as having low competitive ability (Virtue and Melland 2003) and this is 

supported by Barrett-Lennard and Moore (2003) who report that in sown situations seedlings compete poorly with 

annual weeds. However, Puccinellia may readily establish in suitable habitats where there is limited competition 

from native vegetation or in areas of bare ground (such as salt marsh, lake edges or estuaries) (Virtue and Melland 

2003). It may cause some displacement of other plant species but is unlikely to become dominant.

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)

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 

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 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 1 
655

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

It may slow water flow in previously open areas, but the effect is not likely significant. It is not believed to effect 

nutrient levels.

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Given its habitat preference it is possible that it may have some silting effect in certain ecosystems, but this is 

undocumented.

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

0 ≥2

Unknown 1 ≥1
656

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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 
657

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

BENEFICIAL EFFECT

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 

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 

Puccinellia distans (Weeping Alkali-Grass) is apparently of no economic importance in the U.S. (Hitchcock and 

Chase 1950).

Cultivars are sometimes used for fairways (roughs) and occasionally as a turfgrass in areas where salt 

contamination prevents other species from thriving (e.g., roadside trails). 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 
658

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 

Research indicates that Puccinellia distans increases the microbial population significantly and may be of use in 

hydrocarbon degradation for phytoremediation (Ezzatian et al 2009)

It can be used as a pioneer plant for the reclamation of badly salt affected and/or eroded sites.

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, 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
659

Scientific Name: Rorippa sylvestris

Common Name: creeping yellow cress

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Allelopathic, inhibiting germination of seeds of many other plants (Yamane et al 1992).

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., critical reduction, extinction, behavioral 

changes) 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 

Described as a pioneer species, it does not generally outcompete dense, established natives.

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)

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 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 
660

Not significantly 0 

Unknown U √

R. sylvetris is known to hybridize with other members of the genus, but the degree to which it will hybridize with

Rorippa spp. native to the Great Lakes region (e.g., Rcurvipes, R. palustris, R. sessiliflora, R. sinuate) is unknown. 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

1 
661

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Designated as a noxious weed. Considered a serious pest to horticulture (ornamentals) and potential threat to crop 

and grazing lands. can reduce bulb crop value and marketability as a contaminate of nursery stock

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 

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
662

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 
663

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, 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
664

Scientific Name: Rumex longifolius

Common Name: Yard dock

Environmental: unknown

Socio-Economic: unknown

Beneficial: low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

The seeds and vegetation of docks can be toxic to animals (Royer and Dickinson 1999).

Dock species are also an alternate host for number of viruses, fungus, and nematodes (Edwards and Taylor 

1963).Pplants can host high diversity of plant pathogens and invertebrate pests that may affect surrounding plants 

(Martinkova et al., 2009 and references therein).

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., critical reduction, extinction, behavioral 

changes) 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 √

It is an invasive species which can compete with native species. It likely pushes out native species once established.

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)

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 

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 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 1 
665

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

The species hybridizes frequently

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

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)?

Yes, significant effects on human health have already been observed 6 
666

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Dock is occasionally eaten – in high quantities, the oxalic acid it contains can be a health risk.

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

These docks are undesirable in grasslands because they decrease yields and reduce forage feeding value. As a weed 

of pastures and meadows, the main impact of this plant is to reduce the value of infested land as grazing for 

livestock. R. obtusifolius is only 65% as valuable as grass as grazing material because of a combination of reduced 

palatability (and therefore grazing levels) and reduced digestibility (Courtney & Johnson, 1978 in Grossrieder & 

Keary, 2004). It also contains oxalic acid which may be poisonous to livestock. Mature plants also suppress the 

grass yield of pasture. Oswald and Haggar (in Grossrieder & Keary, 2004) found that increasing ground cover by 

Rumex reduced grass yields, as did increasing Rumex density.

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 

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 
667

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U 

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

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
668

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 

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, 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
669

Scientific Name: Rumex obtusifolius

Common Name: Bitter dock

Environmental: Unknown

Socio-Economic: Unknown

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Dock species are also an alternate host for number of viruses, fungus (Dal Bello and Carranza 1995), and 

nematodes (Edwards and Taylor 1963, Townshend and Davidson 1962).

The seeds and vegetation of docks can be toxic to animals (Royer and Dickinson 1999).

Plants can host high diversity of plant pathogens and invertebrate pests that may affect surrounding plants 

(Martinkova et al., 2009 and references therein).

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., critical reduction, extinction, behavioral 

changes) 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 √

It is an invasive species which can compete with native species. It likely pushes out native species once established

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)

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 

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 which may be irreversible or has led to the decline or 

extinction of one or more native species

6 
670

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Dock species frequently hybridize.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

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)?

Yes, significant effects on human health have already been observed 6 
671

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

These docks are undesirable in grasslands because they decrease yields and reduce forage feeding value. As a weed 

of pastures and meadows, the main impact of this plant is to reduce the value of infested land as grazing for 

livestock. R. obtusifolius is only 65% as valuable as grass as grazing material because of a combination of reduced 

palatability (and therefore grazing levels) and reduced digestibility (Courtney & Johnson, 1978 in Grossrieder & 

Keary, 2004). It also contains oxalic acid which may be poisonous to livestock. Mature plants also suppress the 

grass yield of pasture. Oswald and Haggar (in Grossrieder & Keary, 2004) found that increasing ground cover by 

Rumex reduced grass yields, as did increasing Rumex density.

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 

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 
672

Yes, but negative consequences have been small 1 

Not significantly 0 √

Unknown U 

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

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
673

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 

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, 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 

Bitter dock is avoided by rabbits, but it appeared to be a favorite food plant of deer (Amphlett and Rea 1909, cited 

in Cavers and Harper 1964). 

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
674

Scientific Name: Salix alba

Common Name: White willow

Environmental: Unknown

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Salix alba is susceptible to many diseases and parasites. The degree to which it may serve as a vector of disease 

into to related species is unknown.

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 
675

Not significantly 0 

Unknown U √

Salix alba will hybridize with other willows. The degree to which this effects native willows is unknown

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 
676

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
677

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

White willow is cultivated as a source of salicyclic acid (a component of aspirin), for willow bark (natural 

medicine), for its soft elastic wood (commonly used in basketmaking and other crafts), for fiber (papermaking) and 

other purposes. 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 √

Not significantly 0 

Unknown U 

Commonly used as a landscape plant, but native alternatives are available.

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 

The original source of salicyclic acid (aspirin), still a common component of natural medicines.

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 √
678

Unknown U 

This species has been investigated for potential use in pytoremediation of iron cyanide (Yu et al 2006).

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, 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 

Provides riparian habitat for many species of birds and insects. Along with native willows, can be an important 

food source for many species of caterpillars.

Beneficial Effect 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
679

Scientific Name: Salix fragilis

Common Name: Crack willow

Environmental: Unknown

Socio-Economic: Moderate

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Crack willow is susceptible to a variety of parasites and diseases. The degree to which it may serve as a vector for 

these into native willows is not known.

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., critical reduction, extinction, behavioral 

changes) 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 √

There are negative consequences for biodiversity where S. fragilis becomes invasive since the thick canopy created 

when it is dominant is sufficient to shade out other plants and reduce invertebrate abundance (Weber, 2003). These 

changes may also affect fish (Anon, 2000). Flora and fauna associated with both the banks and aquatic environment 

may be affected.

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)

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 √

Some research shows that increased shade cover may impact benthic macroinvertebrate communities, but whether 

this effect is specific to crack willow (as opposed to other riparian trees) is not known.

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
680

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Salix fragilis will hybridize with other willows, but the degree to which this has affected native willows is unknown.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Willow debris can block streams during floods and damage bridges and roads (Anon., 2000). Where large 

infestations have established the costs of removal and restoration may be high.

Environmental damage from S. fragilis invasion includes changes to stream hydrology, higher erosion and 

sedimentation rates and flooding patterns, and they may also use more water than indigenous plant species and 

cause changes to nutrient cycling, water temperature, energy fluxes and general water quality may also result 

(Anon., 2000).

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
681

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Crack willows are relatively fragile and storm-damaged trees can cause damage to adjacent infrastructure.

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

Willows such as S. fragilis may impede recreational activities such as canoeing and fishing (Anon., 2000).

Does it diminish the perceived aesthetic or natural value of the areas it inhabits?
682

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

BENEFICIAL EFFECT

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 

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. fragilis is considered an important species in hedgerows, shelterbelts and windbreaks, along fields and field 

channels. It has also been planted to prevent soil erosion along streambanks. S. fragilis is not a timber species 

(wood density is about 450 kg/m3 at 15% moisture content) and has been mainly used for fuelwood. S. fragilis was 

once an important species for basket-making industries. (CABI 2014).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 
683

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 

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 

Salix fragilis has been investigated for suitability for phytoremediation of metals. It may be suitable for remediation 

of sites contaminated with cadmium and zinc (Vandesasteele et al 2005). It has also been investigated and has 

potential for phytoremediation of sulfonamide anitibiotics (from confined feedlot livestock operations) (Michelini et 

al 2012). 

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, 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 

Has been used for bank stabilization, riparian habitat, etc.

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
684

Scientific Name: Salix purpurea

Common Name: purple willow, purple osier willow

Environmental: Unknown

Socio-Economic: Low

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

Susceptible to many diseases and parasites, but the extent to which it forms a vector for these into native willows is 

unknown.

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., critical reduction, extinction, behavioral 

changes) 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 √

“The crack willows have the ability to produce dense stands in floodplains and other favorable habitats. Because 

most native willows are much smaller in stature than the crack willows, and because most willows are not very 

shade-tolerant, is seems likely that crack willows would tend to overtop and displace native willows.” 

http://invasives.glifwc.org/Salix_spp/eco_impacts.html.

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)

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 √

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 which may be irreversible or has led to the decline or 

extinction of one or more native species

6 
685

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

This species will likely hybridize with other willows, but the degree to which this effects native willows is unknown.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Stabilizes streambanks and prevents erosion.

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

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)?
686

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
687

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

BENEFICIAL EFFECT

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 

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 

Used to control erosion along streambanks.

Used for basket-making.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 
688

Yes, but positive impact for humans or native species is considered negligible 1 

Not significantly 0 √

Unknown U 

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, 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 

Provide cover for small animals and browse for deer, beaver and rabbits as well as exceptional nesting sites for 

birds.

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
689

Scientific Name: Solanum dulcamara L.

Common Name: bittersweet nightshade

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Low

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Solanum dulcamara, along with other plants in the nightshade family, is poisonous. It produces solanine in its 

leaves, shoots, and unripe berries. If ingested by animals, it can cause difficult breathing, weakness, dermatitis, 

gastrointestinal irritation/pain, nervous system problems, and in severe cases death (Forest Health Staff 2006, King 

County 2010). 

Bittersweet nightshade also has a strong, unpleasant odor so most animals will avoid it and poisonings from this 

plant are not very frequent. 

Water extract from the leaves of S. sulcamara significantly inhibited the growth of Pinus resinosa seedlings; 

however, this allelopathy has not been studied in the field (Waggy 2009).

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 √

The vines of S. dulcamara can grow over nearby trees and shrubs, and even pull down smaller plants (Forest Health 

Staff 2006, IPANE 2013).This growing ability can quickly lead to dense thickets of bittersweet nightshade (King 

County 2010).

Bittersweet nightshade is abundant throughout Michigan and Ohio (OARDC Extension 2013, Reznicek et al. 2011).

The New York Invasive Species Council ranks this species moderate ecological risk (New York Invasive 2010). 

Falck and Garske (2002) acknowledge that given this species small size and ability to thrive in forested areas, that 

data about its presence is likely underrepresented.

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 
690

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 √

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

In studies conducted in New Zealand, species within the Solanum genus showed resistance to hybridization 

(Armstrong et al. 2005). This indicates that S. dulcamara may pose only a small genetic threat to native or crop 

species.

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Solanum dulcamara can also become dominant along small waterways and alter the flow of water (King country 

2010).

Environmental Impact Total 2

Total Unknowns (U) 2
691

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

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)? 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

All portions of this plant are poisonous (Forest Health Staff 2006).

It has been reported that paralysis can occur in humans after consuming only 6 berries (OARDC Extension 2006).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U

Poisoning from S. dulcamara has been reported in cattle, sheep, and horses (OARDC Extension 2006).
692

Bittersweet nightshade can act as a host for Leptinotarsa decemlineata (Colorado potato beetle). This beetle can 

invade species from the Solanaceae family, such as potatoes and tomatoes, and could damage the crops (IPANE 

2013, OARDC Extension 2006). 

However, success of beetles reared on S. dulcamara varied depending on seasonally varying phytochemicals present 

in the plant (Hare 1983).

Solanum dulcamara can also host two other pathogens: Phytophthora infestans (causes potato blight) and Ralstonia 

solanacearum (causes brown rot in potatoes) (Golas et al. 2010, Knapp 2013).

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

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’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0

0 ≥2 Unknown

1 ≥1

BENEFICIAL EFFECT

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

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 √
693

Unknown U

Solanum dulcamara contain glycosides; which can be used in the production of steroidal hormones (Curtis et al. 

2000).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U

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

Extracts from the roots, bark, and stems of S. dulcamara have been used to relieve pain caused by rheumatism, poor 

circulation, ulcers, and skin afflictions. Currently, these extracts are not widely used (Waggy 2009).

Alcoholic extracts of S. dulcamara, taken from plants grown in New York and Wisconsin, exhibited tumor-inhibitory 

activity in mice (Kupchan et al. 1965).

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 

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, 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

Scoring

Score # U’s Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low

1 0
694

0 ≥2 Unknown

1 ≥1
695

Scientific Name: Solidago sempervirens

Common Name: seaside goldenrod

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

It has been reported that the release of root exudates by seaside goldenrod produce allelochemicals that negatively 

affect the growth of nearby vegetation. Studies By Cheplick and Aliotta (2009) have found that seaside goldenrod 

has a negative effect on the growth of native grasses.

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., critical reduction, extinction, behavioral 

changes) 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 

Growing in areas that collect salt runoff they compete with few native plants in this harsh environment.

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)

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 √

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 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 
696

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

1 
697

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

In areas where it is native, this plant has been used for dune stabilization and erosion control. 

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
698

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

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, or commercially valuable)?
699

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
700

Scientific Name: Sparganium glomeratum

Common Name: bur reed

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 √

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √
701

Many hybrids are reported in Sparganium but few are verified.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
702

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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 
703

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

BENEFICIAL EFFECT

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 

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 

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 6 
704

native species

Yes, but positive impact for humans or native species is considered negligible 1 

Not significantly 0 √

Unknown U 

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, 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
705

Scientific Name: Trapa natans L.

Common Name: Water chestnut 

Environmental: High

Socio-Economic: High

Beneficial: Moderate

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Water chestnut is also capable of an allelopathic response that inhibits the growth of phytoplankton (Lui et al. 

2010a).

Areas of stagnant water caused by dense stands of T. natans create breeding grounds for mosquitoes (Naylor 2003).

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., critical reduction, extinction, behavioral 

changes) 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 

Trapa natans is a fast-growing species that forms mats of vegetation that float on the water’s surface (IPANE 2013, 

Swearingen et al. 2002). 

Given its biological structure, T. natans is able to cover the water with up to three layers of leaves (Pemberton 

2002). 

These dense mats inhibit the growth of native aquatic species and enable water chestnut to outcompete for sunlight, 

nutrients, and space (IN DNR 2012, OISAP 2013, Pennsylvania Sea Grant 2012).

Water chestnut is able to prevent sunlight from reaching the bottom sediments; making it especially threatening to 

native grasses (Naylor 2003).

The introduction of T. natans leads to a reduction in plant biodiversity as it comes to dominate aquatic ecosystems 

(OISAP 2013, Pennsylvania Sea Grant 2012).

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)

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 √
706

Not significantly 0 

Unknown U 

Trapa natans offers little nutritional value for wildlife (IPANE 2013, Pennsylvania Sea Grant 2012, VDEC 2002). 

Water chestnut is also capable of an allelopathic response that inhibits the growth of phytoplankton (Lui et al. 

2010a). 

These two impacts may alter existing predator/prey relationships as native species go elsewhere to search for food.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

During the growing season, dense surface mats block the air exchange between the water’s surface and the 

atmosphere (Pennsylvania Sea Grant 2012). 

Caraco and Cole (2002) found that beds dominated by T. natans had dissolved oxygen levels below 2.5 mg/l about 

40% of the time. Low levels of oxygen caused by the presence of this species, makes T. natans populations 

unsuitable for fish species and likely effects the redox reactions in bottom sediments (Caraco and Cole 2002). 

When water chestnut populations die and sink, the decomposition of this large amount a plant material reduces the 

dissolved oxygen level even further and in extreme cases, can cause fish kills (IN DNR 2012, OISAP 2013, 

Swearingen et al. 2002, VDEC 2002). 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0 

Unknown U 

Large infestations of T. natans can reduce water flow and even clog waterways (CANSWG 2006, Naylor 2003, 

Pennsylvania Sea Grant 2012).
707

Environmental Impact Total 5

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Areas of stagnant water caused by dense stands of T. natans create breeding grounds for mosquitoes (Naylor 2003).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Large infestations of T. natans can reduce water flow and even clog waterways (Group 2006, Naylor 2003, 

Pennsylvania Sea Grant 2012). 

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm 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 √

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

1 
708

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0 

Unknown U 

Dense patches of T. natans can hinder commercial navigation (IN DNR 2012, IPANE 2013). 

The major economic costs associated with water chestnut populations are mechanical or chemical control efforts 

(Naylor 2003).

The Pennsylvania Department of Conservation and Natural Resources (n.d.) states that this species costs hundreds 

of thousands of dollars to control.

Millions of dollars have been spent on mechanical harvesting and manual removal of T. natans populations; these 

programs have had limited success (Wu and Wu 2006). Vermont spent almost $500,000 in 2000 to mechanically 

remove water chestnut (Pennsylvania Sea Grant 2012). 

From 1982-2005 various state organizations spent over $5 million to control T. natans in Lake Champlain (IPANE 

2013). 

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 

Infestations of water chestnut can also limit or even prevent recreational activities such as boating, fishing, and 

hunting (WI DNR 2012). 

These nuts can also wash up and accumulate along the shore; reducing the access to beaches (IN DNR 2012, 

OISAP 2013). 

In Vermont, many previously fished bays of southern Lake Champlain are now inaccessible, and floating mats of T. 

natans can create a hazard for boaters. Large stands of water chestnut may also restrict fish farming and batfish 

harvesting (Gunderson and Kinnunen 2004).

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 hard, spiny seeds can punctuate leather and can cause painful wounds to humans and animals that step on them 

(Haber 1999, Swearingen et al. 2012).

Socio-Economic Impact 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
709

BENEFICIAL EFFECT

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 

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 ornamental plant has been used in ponds and outdoor water gardens (Liu et al. 2010).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 √

Not significantly 0 

Unknown U 

Once cracked open, the flesh inside the nut-like fruit can be cooked, eaten raw, or used in other foods (Lui et al. 

2010a, Magness et al. 1971).

Even though this is not the water chestnut typically found in Asian cuisine, T. natans is a food source typically used 

in Asia (O’Neill Jr. 2006). 

Dried nuts can be ground into flour for baking (Sturtevant and (ed) 1972).

Unfortunately, this species stores toxic compounds in the edible parts of the plant; reducing the ability of this 

species to be utilized as a food source (Rai and Sinha 2011). 

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 

The fruit has historically been used to treat conditions such as rheumatism and sunburn (Lui et al. 2010a).

In an experimental study, extracts from T. natans (combined with extracts from other species) decreased pain for 

patients suffering from shingles (Hijikata et al. 2005). 

In another study, an herbal mixture containing T. natans brought symptom relief to those suffering herpes genitalis 

and labialis outbreaks (Hijikata et al. 2007).

A peptide contained in T. natans has anti-fungal properties (Mandal et al. 2011).

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 
710

Unknown U 

The husks from T. natans can be transformed into iron-modified activated carbon; an adsorbent compound that is 

able to remove chromium (VI) from wastewater (Lui et al. 2010b). 

In experiments in India, T. natans was able to remove a significant amount of mercury from paper mill effluent 

(Mishra et al. 2013). 

Trapa natans is also able to remove nitrite from the water (Rawat et al. 2012). 

Trapa natans can remove metals from contaminated water (Baldisserotto et al. 2007, Rai and Sinha 

2011).Unfortunately, this species stores the toxic compounds in the edible parts of the plant; reducing the ability of 

this species to be utilized as a food source (Rai and Sinha 2011). 

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, 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 √

Strayer et al. (2003) found increased diversity in epiphytic and benthic macroinvertebrates in T. natans populations, 

compared to stands of native vegetation in the Hudson River (New York). Even with this increase in biodiversity, 

Strayer et al. (2003) concluded that these macroinvertebrates were not available to fish because of the low oxygen 

concentrations.

Surveys conducted by Kornijów et al. (2010) also found dense, diverse benthic communities under floating mats of 

T. natans containing insects, oligochaetes, crustaceans, and other taxa. However, Kornijów et al. (2010) determined 

that water chestnut beds provided valuable habitat for invertebrate biodiversity and production, and may contribute 

substantially to fish production.

Beneficial Effect 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
711

Scientific Name: Typha angustifolia L.

Common Name: Narrow-leaved cattail

Environmental: High

Socio-Economic: Low

Beneficial: High

ENVIRONMENTAL IMPACT

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.)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Narrow-leaved cattail is thought to be allelopathic, producing chemicals that discourage growth of other plant 

species (Ohio EPA 2001).

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

Typha angustifolia can out-compete native species in a variety of wetland ecosystems and its presence limits 

biodiversity (Forest Health Staff 2006, Ohio EPA 2001).

High seed production and wind dispersal enable seeds to reach newly disturbed sites or areas of disturbance within 

a colonized site (Grace and Harrison 1986 in Miklovic 2000). Typha angustifolia is especially invasive in disturbed 

wetlands and readily forms dense, monotypic stands that shade out other species (Ohio EPA 2001, Stevens and 

Hoag 2006).

Narrow-leaved cattail is also tolerant of saline conditions and uses this tolerance to out-compete less tolerant 

species (Miklovic 2000).

When growing at a depth at or exceeding 0.25 m, populations of T. angustifolia can expand at a rate of 1 m per year 

(Weisner 1993). Reports of cattail dominated habitats have greatly increased in the Midwest over the last few 

decades (Borland et al. 2009). 

In studies where cattail litter was added to test sites, native wetland plants such as marsh bellflower (Campanula 

aparinoides), bulb-bearing water-hemlock (Cicuta bulbifera), and stiff marsh bedstraw (Galium tinctorium) did not 

emerge. Narrow-leaved cattail has large energy reserves in its rhizomes that supply new shoots with the necessary 

energy to push through the litter in the spring (Vaccaro et al. 2009).

Typha angustifolia emerges earlier in the spring and grows more rapidly and taller than T. latifolia, often giving it 

the competitive advantage in areas where the two species coexist. In test areas, T. angustifolia slowly replaces T. 

latifolia, except in very shallow water (Weisner 1993).

Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 6
712

(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.)

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

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Hybridization between T. angustifolia and T. latifolia results in the invasive Typha x glauca. 

Previously, it was thought that the hybrid was sterile and could only spread via growth of its rhizomes; however it is 

now known that some Typha x glauca individuals can reproduce sexually (McKenzie-Gopsill et al. 2012, Travis et

al. 2010).

Typha x glauca often grows larger and can tolerate a wider range of environmental conditions than either parent 

species (Borland et al. 2009, Galatowitsch 2012, Travis et al. 2010). 

In Hoosier Prairie Nature Preserve, Indiana T. angustifolia and Typha x glauca constitute almost 100% of the 

vegetation in the wetlands (Indiana Lake Michigan Coastal Program 2007). 

Some experts believe T. glauca is more invasive and problematic than T. angustifolia (Reeb 2007). However, 

coexistence of T. angustifolia and T. latifolia does not guarantee that hybridization will occur. In Ohio, T. 

angustifolia blooms 2 weeks earlier than T. latifolia, leaving a short period of time when cross-pollination is 

possible (Selbo and Snow 2004). 

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

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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.)?

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 1 √
713

effects have been mild

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0

Unknown U

Dense root and rhizome mats produce a thick layer of litter that prohibits the growth of many other plants species 

(Forest Health Staff 2006). Stable water levels and stands of dead stems result in litter accumulation, which can 

alter nutrient levels and species diversity in benthic communities.

When Typha x glauca individuals die, there is a substantial amount of dead shoots and litter that remains; especially 

in areas dense with Typha spp. The dead biomass effectively blocks sunlight, smothers new growth, and modifies the 

concentration of nutrients (Galatowitsch 2012).

Environmental Impact 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great 

Lakes

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
714

Yes, but the effects are negligible and/or easily reversed 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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

BENEFICIAL EFFECT

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
715

Not significantly 0 √

Unknown U

A stand of cattails can act as a nutrient regulator in aquatic ecosystems, taking up nutrients when they are overly 

abundant and releasing nutrients when there is a deficit. This regulation of nutrients can play an important role in 

controlling phytoplankton blooms (Mason and Bryant 1975).

Typha angustifolia also contains three phenic acids, which act as allelochemicals and may further control algal 

blooms in eutrophic waters (Zhang et al. 2011).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

If collected at the appropriate stage (and in some cases cooked) all parts of the narrow-leaved cattail are edible 

(Stevens and Hoag 2006).

It is estimated that one acre of T. angustifolia would yield about 6,475 pounds of flour (from the pollen) consisting 

of about 80% carbohydrates and 6-8% protein (Harrington 1972 in Stevens and Hoag 2006).

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

Narrow-leaved cattail pollen has been used for the treatment of dysmenorrhea, stranguria, and metrorrhagia in 

China (Tao et al. 2011). 

Oxidative stress, which is usually associated with inflammatory bowel disease, was reduced in rats whose diets 

included T. angustifolia rhizome flour (Fruet et al. 2012).

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

Typha angustifolia can be planted in constructed wetlands (CWs) to aid in tertiary water treatment (Stevens and 

Hoag 2006).

CWs in Canada with monocultures of T. angustifolia were able to remove between 94%-99% of the pollutants 

(primarily nitrogen and phosphorus) from highly concentrated fish farm waste (Gagnon et al. 2012).

Typha angustifolia was able to remove lead, iron, manganese, copper, zinc, and nickel from aqueous solutions and 

was especially effective at taking up the latter three (Chandra and Yadav 2010, Muhammad et al. 2009).
716

Typha angustifolia showed no signs of toxicity after 30 days exposure to 1 mM chromium, cadmium, or lead. During 

the experiments with lead, narrow-leaved cattail increased its uptake of calcium, iron, and zinc (Bah et al. 2011).

Narrow-leaved cattail is tolerant of cadmium and may be able to remove it from soils via phytoremediation (Xu et

al. 2011).

Jomjun et al. (2011) demonstrated that T. angustifolia is capable of removing 56 mg of arsenic per m2 soil per day.

Typha angustifolia is tolerant of relatively high concentrations of hexachlorobenzene and its two metabolites and 

may therefore be useful in phytoremediation of these pollutants (Ma and Havelka 2009). 

Narrow-leaved cattail can also absorb synthetic dyes, making it a possible plant for treating complex wastewaters 

(Nilratnisakorn et al. 2007).

There has also been some initial success using T. angustifolia in constructed wetlands to remove pharmaceuticals 

and personal care products from urban waste water (Hijosa-Valsero et al. 2011, Reyes-Contreras et al. 2012).

Given the variety of pollutants that T. angustifolia can absorb, it has the potential to be used in complex 

phytoremediation and constructed wetlands.

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, 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

In limited quantities, T. angustifolia can actually be beneficial to an ecosystem by adding food and habitat diversity 

(Miklovic 2000).

Its seeds are eaten by several duck species; however, they are not as nutritious those of as native species (Stevens 

and Hoag 2006).

Muskrats, beavers, and rats eat the stalks and roots of narrow-leaved cattail (MINN-DNR 2012).

It provides cover and nesting habitat for waterfowl and marsh birds such as the red-winged blackbird (Agelaius 

phoeniceus) (MNDNR 2012, Pennsylvania State Department 2006).

Stands of T. angustifolia offer breeding ground and hiding places for numerous invertebrates and small fish (Fell et

al. 2003, Olson et al. 1999).

When planted along shorelines, this cattail can provide habitat for largemouth bass and northern pike (MNDNR 

2012, United States Forest Service 2012).

Other organisms often found in stands of T. angustifolia include leeches, crustaceans, mollusks, and insects such as 

dragonflies and damselflies (Olson et al. 1999, Su et al. 2007).

For Swan Lake, Minnesota (located outside the Great Lakes watershed), it is recommended that the lake be 

managed to encourage T. angustifolia expansion to help increase the biomass of macroinvertebrates for young 

waterfowl to eat (Olson et al. 1999).

Typha spp. serve as important nutrient reservoirs (Su et al. 2007).

Narrow-leaved cattail is used in prairie wetland restoration (United States Forest Service 2012). 

It can also be planted along lakes and ponds to both stabilize marsh areas and protect shores from erosion 

(MNDNR 2012).

Constructed wetlands (CWs) tend to emit higher levels of greenhouse gas (GHG) than natural wetlands. However, 

Maltais-Landry et al. (2009) reports that of the CWs tested, those planted solely with T. angustifolia emitted the 

lowest levels of GHG.

Beneficial Effect Total 7

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
717

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
718

Scientific Name: Veronica beccabunga

Common Name: European brooklime 

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 

Not significantly 0 

Unknown U √

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., critical reduction, extinction, behavioral 

changes) 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 

Can form large stands (clonal patches, Grime et al., 1988), that cover the stream and significantly reduce native 

riparian and wetland species (Mehrhoff et al., 2003); however, no documention of stands larger than 1/4 acre.

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)

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 √

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 
719

Not significantly 0

Unknown U √

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Environmental Impact Total 3

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

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)?

Yes, significant effects on human health have already been observed 6 

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 

Not significantly 0 √
720

Unknown U 

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture)?

es, it has caused significant damage to one or more markets or economic sectors 6 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 

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 

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
721

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 

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 

Grown as a bee/butterfly plant, in water gardens, and as an ornamental. Leaves are edible as a bitter green.

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

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 

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, or commercially valuable)?

Yes, it significantly contributes to the ecosystem in one or more of these ways 6 
722

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
723

A.9 Algae

Scientific Name: Actinocyclus normanii fo. subsalsa

Common Name: Diatom

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Due to a high demand of silica for its heavily silicified walls, during blooms, A. normanii f. subsalsa may deplete 

dissolved silica concentration in shallow bays. The resulting silica-limited environment is detrimental to species of 

native diatoms that are dependent on silica availability and promotes the growth of harmful blue-green algae 

(Edlund et al. 2000, Theriot and Stoermer 1985). Sediment cores taken from Lake Ontario indicate the introduction 

of Stephanodiscus binderanus and A. normanii f. subsalsa is correlated with the extirpation of native species 

including S. transilvanicus, Cyclotella comta, C. michiganiana, C. ocellata, and C. stelligera (Stoermer et al 1985).

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)

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

Actinocyclus normanii f. subsalsa was found to be a major source of particulate nitrogen in one New England 

estuary, where it reached 99% abundance—greater than that observed in the Great Lakes. Under these conditions 
724

Actinocyclus normanii f. subsalsa supported many consumers, including planktonic copepods, benthic amphipods, 

grass shrimp, mud crabs, alewife, and white perch (Hughes et al. 2000). It is unclear if A. normanii f. subsalsa has a 

similar effect in the Great Lake populations.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Actinocyclus niagarae is the only other species of the same genus in the Great Lakes and no research indicates that 

the two species are influencing each other genetically (Stoermer and Kreis 1978).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1√

Not significantly 0 

Unknown U

Actinocyclus normanii f. subsalsa has been associated with the depletion of dissolved silica in shallow bays and 

coastal areas in the Great Lakes (Edlund et al. 2000, Theriot and Stoermer 1985). 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate
725

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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) 

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

A high abundance of A. normanii f. subsalsa is associated with blue-green algae blooms, which can severely impact 

water quality (Edlund et al 2000).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
726

Not significantly 0 √

Unknown U

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
727

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

Actinocyclus normanii f. subsalsa is a species that is used to identify the history of pollution in sediment cores from 

lakes (Stoermer et al 1985).

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

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, 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
728

Scientific Name: Bangia atropurpurea

Common Name: red alga

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Bangia atropurpurea can adapt to a broad range of salinities over time and can tolerate desiccation and osmotic 

stress. These traits allow B. atropurpurea to occupy the high littoral zone where other filamentous algae do not 

typically grow (Graham and Graham 1987, Jackson 1988, Lin and Blum 1976, Sheath and Cole 1984, Stewart 

2008). There are conflicting reports about whether these characteristics allow B. atropurpurea to out-compete 

native species (Edlund et al. 2000, Stewart 2008).

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)

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 √

The mucilaginous cell wall of B. atropurpurea is advantageous when living in the upper littoral zone; however, it 

supports approximately 1000 fewer epiphyte cells/mm2 compared to native organisms like Cladophora (Lowe et al. 

1982). This lack of quantity and diversity of algal epiphytes could negatively impact the littoral food web. 

Furthermore, B. atropurpurea can only support larval chironomids, while native Cladophora supports a larger 
729

diversity of macroinvertebrates (Chilton et al. 1986). Whether this will have an impact on invertebrate composition 

hinges upon the ability of B. atropurpurea to outcompete Cladophora.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

The populations of B. atropurpurea in the Great Lakes are limited to asexual reproduction and therefore will not 

affect native species genetically (Chilton et al 1986, Sheath and Cole 1984).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Bangia atropurpurea can be a biofouling organism and has contributed to hypoxic conditions in Lake Erie (Edlund 

et al. 2000, Stewart 2008).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 2

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
730

1 0

0 ≥2

Unknown 1 ≥1

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).

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

Bangia atropurpurea typically grows in association with Uthorixa and Cladophora. All three of these species are 

considered biofouling organisms (Lin and Blum 1977). There is considerable research on the negative impacts of 

these three macrophytes in Lake Erie, however, it is difficult to identify what impacts can be specifically attributed 

to B. atropurpurea (Chilton et al. 1986, Edlund et al. 2000, Jackson 1988, Lowe et al. 1982, Stewart et al. 2008).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
731

Not significantly 0 √

Unknown U

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
732

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

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

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, 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
733

Scientific Name: Chaetoceros muelleri var. subsalsum

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Given the right water chemistry Chaetoceros muelleri var. subsalsum is capable of sustaining abundant populations 

(Fuji et al. 1995). Saginaw Bay, the area of the Great Lakes where C. muelleri var. subsalsum was collected 

historically, has high nutrient levels. Water salinity is the primary factor controlling population growth rates of C. 

muelleri var. subsalsum. Nutrient conditions in Saginaw Bay, particularly regarding salinity levels, are not 

available and therefore limit predictions of the potential impacts of C. muelleri var. subsalsum (Chapra et al. 2009). 

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)

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

Large populations of C. muelleri could alter predator-prey relationships, but the water conditions for a large 

population are not currently being met in Saginaw Bay. Depending on other restoration initiatives this could 

change.

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
734

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Chaetoceros muelleri var. sublasum is the only species in the Great Lakes of this genus and there is only one other 

species of its order found in the Great Lakes, making hybridization unlikely. 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

SOCIO-ECONOMIC IMPACT
735

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 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U 

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

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
736

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
737

Yes, but positive impact for humans or native species is considered negligible 1 

Not significantly 0 √

Unknown U

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, 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
738

Scientific Name: Chroodactylon ornatum (ramosum)

Common Name: red alga

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

As a part of the Cladophora epiphyton community, Chroodactylon ramosum has a widespread distribution 

throughout Lakes Huron, Erie and Ontario. It is, however, a minor part of that community and has no recorded 

ecological impacts (Sheath and Morison 1982). 

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 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
739

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

1
740

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
741

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
742

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, 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
743

Scientific Name: Conticribra (Thalassiosira) guillardii

Common Name: diatom

Environmental: Low

Socio-Economic: Low 

Beneficial: Low 

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Conticribra guillardii has been recorded at abundances reaching 95% of the diatom community in locations outside 

of the Great Lakes, although it is more typically less abundant in freshwater (Hasle 1978). In the Great Lakes, C. 

guillardii has only been recorded once (Sandusky Bay, OH), and the abundance of this sample compared to the rest 

of the phytoplankton was not recorded (Hasle (1978).

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
744

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
745

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
746

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
747

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, 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
748

Scientific Name: Cyclotella atomus

Common Name: Diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Cyclotella atomus often forms algal blooms, and in some locations outside of the Great Lakes basin, it composes 

95% of the phytoplankton community (Jackson et al. 1987, Kiss 1996, Murakami et al. 1998). In portions of Lake 

Ontario and Lake Erie, C. atomus has been recorded as making up an abundant portion of the phytoplankton 

community, but there are no records of direct effects from competition with native species (Klarer and Millie 1994, 

Makarewicz 1987).

Cyclotella atomus thrives in a wide range of salinities, at high nutrient levels, and under small-scale turbulence 

(e.g., 0.38 m s−1) (Jackson et al. 1987, Weckstrom and Juggins 2006, Wang et al. 2012, Yang et al. 2005). Native 

diatoms in eutrophic water bodies where silica is limiting could be in competition with C. atomus, which has a high 

affinity for silica (Weckstrom and Juggins 2006). Cyclotella atomus has also been seen in locations with reduced 

algal diversity, but this is likely due to agricultural eutrophication rather than to the presence of C. atomus.

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)

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
749

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

There are over 50 species of Cyclotella in the Great Lakes, but there is no known research indicating that there is 

any genetic interaction between C. atomus and native species.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Cyclotella atomus is often found in locations that have high levels of nutrient pollution, but it does not directly 

decrease water quality (Jackson et al. 1987, Stoermer and Labewski 1976, Weckstrom and Juggins 2006, Yang et al. 

2005). 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
750

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Within the Great Lakes basin, C. atomus occurs primarily in shallow waters with high nutrient levels. Cyclotella 

atomus does not create eutrophic conditions, but it can contribute to the negative effects of eutrophication by further 

reducing silica availability for native diatoms (Stoermer and Labewski 1976, Weckstrom and Juggins 2006).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
751

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

1 √
752

It is potentially important to medicine or research and is currently being or scheduled to be studied

Not significantly 0

Unknown U

The appearance of C. atomus, along with other small planktonic diatoms, can be used as an early indicator that the 

water quality is deteriorating (Collins et al. 1997, Weckstrom and Juggins 2006, Yang et al. 2005). Stewart et al. 

(2008) used C. atomus as an indicator of increasing surface temperature due to climate change in Sanagak Lake, 

Nunavut, Canada.

Cyclotella atomus has also been used in paleoflood studies to identify historical floods in an attempt to enhance 

predictive models for extreme flood events. This same paleoflood data was used to assess the impact of climate 

change on flood severity and frequency (Medioli and Brooks 2003).

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

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, 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
753

Scientific Name: Cyclotella cryptica

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Cyclotella cryptica can grow heterotrophically for up to one year and could potentially outcompete native species in 

low or no light conditions, although this has not been recorded in the Great Lakes (White 1974).

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)

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

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 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

AND/OR

1
754

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Cyclotella cryptica is a euryhaline species and within the Great Lakes in found primarily in nearshore areas, bays, 

and river mouths that have an elevated salinity (approximately 100-160 Cl- mg/mL) due to salt pollution (Liu and 

Hellebust 1976, Makarewicz 1987). It does not itself affect water quality.

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
755

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
756

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

BENEFICIAL EFFECT

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

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

Cyclotella cryptica is a species that is very important to the growing algal biofuels industry. Roessler (1988) found 

that C. cryptica grown in silicon-deficient conditions had significantly higher levels of lipid production. Researchers 

are currently attempting to genetically engineer other species of algae that contains the acetyl-CoA carboxylase 

enzyme found in C. cryptica in order to increase lipid content (Day et al. 2012).

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 

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1 

Not significantly 0 √

Unknown U 

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 

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
757

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 

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, 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
758

Scientific Name: Cylindrospermopsis raciborskii

Common Name: Cylindro

Environmental: Low

Socio-Economic: Moderate

Beneficial: Low

Comments: In general, populations of Cylindrospermopsis raciborskii in the Great Lakes region are small and have 

had relatively little impact on the environment or socio-economic factors. However, C. raciborskii is known to cause 

serious water quality and ecosystem health issues in other parts of the world. These impacts outside of the Great 

Lakes should be seriously considered as the range of C. raciborskii is expanding with global climate change. If water 

temperatures continue to increase and water levels continue to drop, studies suggest that these isolated populations 

within the Great Lake could become much more prominent (Conroy et al. 2007, Wiedner et al. 2007, Xie et al. 

2007).

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Some strains of C. raciborskii produce a variety of toxins including cylindrospermopsin, anatoxin-a, and saxitoxin. 

These toxins have been responsible for fish kills in a reservoir in Brazil and cattle deaths in Australia (De Souza et 

al. 1998, Saker et al. 1999b, Thomas et al. 1998). Cylindrospermopsin has been found to bioaccumulate in certain 

species of mollusks, crayfish, and snails; in some cases this exposure was toxic (Kiss et al. 2002, Saker et al. 2004, 

Saker and Eagleshame 1999, White et al. 2006). 

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., critical reduction, extinction, behavioral 

changes) 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

None of the populations dispersed throughout the Great Lakes basin are large enough currently to outcompete 

native phytoplankton species for resources (Conroy 2007, Xie et al. 2011). 

At high densities (e.g., > 90% phytoplankton biomass) in more tropical climates, C. raciborskii can cause a 

reduction in biodiversity. This is because of its ability to fix atmospheric nitrogen, sequester phosphorous, and move 

throughout the water column (Borics et al. 2000, Bouvy et al. 2001, Dobberfuhl 2003, Leonarda and Paerl 2005).

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 

6
759

native species 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 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

In the St. Johns River System, Florida, C. raciborskii appears to reduce the size and diversity of zooplankton by 

sequestering nutrients and making them unavailable to grazers in the water column (Leonard and Paerl 2005).

Some rotifers and cladocerans exhibit reduced feeding rates, growth rates, or growth potential in the presence of C. 

raciborskii (Hawkins and Lampert 1989, Nogueira et al. 2004, Rothaupt 1991). 

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 0
760

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Treatment of a C. raciborskii bloom with copper sulfate resulted in contamination of a reservoir on Palm Island, 

Australia with cylindrospermopsin. After drinking the contaminated water, 141 people were hospitalized with 

heptoenteritis and other symptoms affecting kidneys, adrenal glands, small intestine, lungs, thymus, and heart 

(Bernard et al. 2003, Bouke et al. 1983, Hawkins et al. 1985). There is also accumulating evidence that 

cylindrospermopsin is carcinogenic (Falconer and Humpage 2001).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Strains of C. raciborskii that produce toxins can severely impact water quality both in drinking water for humans 

and as a result of bioaccumulation in aquatic organisms (Bernard et al. 2003, Bouke et al. 1983, Hawkins et al. 

1985, Kiss et al. 2002, Saker et al.2004, Saker and Eagleshame 1999, White et al. 2006).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small 1
761

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

There are multiple reports of toxic C. raciborskii blooms occurring in aquaculture ponds in Australia and other 

tropical regions. This often results in bioaccumulation of cylindrospermopsin within the organisms intended for 

harvest and the economic loss of infected organisms. Such blooms also create a risk of the toxin getting into the 

human food market if not detected soon enough (Saker and Eaglesham 1999).

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

Cylindrospermopsin is an irritant and causes cutaneous sensitizing that could be harmful to recreational users of 

impacted water bodies; to date, however, populations in the Great Lakes basin have not been known to produce 

cylindrospermopsin (Stewart et al. 2006).

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

In areas outside of the Great Lakes, the overwhelming biomass of C. raciborskii blooms in association with the 

changes to the biodiversity of the system can potentially have a negative impact the natural value of the area 

(Leonard and Paerl 2005).

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

BENEFICIAL EFFECT

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 √
762

Unknown U

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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)?

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
763

1 0

0 ≥2

Unknown 1 ≥1
764

Scientific Name: Diatoma ehrenbergii

Common Name: diatom 

Environmental: Low

Socio-Economic: Low

Beneficial: Low

Comments: Diatoma ehrenbergii was recorded at relatively low levels in eutrophic areas of Lake Michigan, Saginaw 

Bay, and Lake Huron (Mills et al. 1993, Stoermer and Yang 1969). As such, the extent of any impacts is likely to be 

limited.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 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 1
765

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
766

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
767

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
768

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)?

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
769

Scientific Name: Discostella pseudostelligera

Common Name: Diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 Arizona, D. pseudostelligera has been reported to outcompete other diatoms for light in under high light intensity 

conditions. This has not been observed in the Great Lakes (Czarnecki 1979).

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)

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

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 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

AND/OR

1
770

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

There are over 50 species of Discostella in the Great Lakes, but there is no known research indicating that there is 

any genetic interaction between D. pseudostelligera and native species.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Discostella pseudostelligera is often found in locations that have elevated levels of nutrient pollution, but it does not 

directly decrease water quality (Finney et al. 2000, Reynolds et al 2002, Stoermer and Yang 1969, 1970, Stoermer 

and Ladewski 1976).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
771

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
772

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
773

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

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, 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 appearance and increased abundance of D. pseudostelligera, along with other small planktonic diatoms, can be 

used as a historical indicator of pollution and changing water quality (Bere and Tundisi 2011, Lim et al. 2001, 

Moser et al. 2010, Pappas 2010).

Discostella pseudostelligera has also been used in Arctic lakes as an indicator of climate change (Kiarst-Riddoch et 

al. 2005).

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
774

Scientific Name: Discotella woltereckii

Common Name: Diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 

Discostella woltereckii occurs in meso-eutrophic to eutrophic conditions, reaching high densities in locations 

outside of the Great Lakes. As such, it has the potential to out-compete native phytoplankton under nutrient rich 

conditions (Wojtal et al. 2005).

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)

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 

Discostella woltereckii occurs in meso-eutrophic to eutrophic conditions, reaching high densities in locations 

outside of the Great Lakes. These high densities could interfere with trophic level interactions but there is not 

currently any research on the topic (Wojtal et al. 2005).

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 which may be irreversible or has led to the 6
775

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
776

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

Discostella woltereckii grows nonindigenously in artificial drainage systems in some locations outside of the Great 

Lakes, forming thick mats that could potentially clog drains and disrupt water transportation (Kastovsky et al. 

2010). While this species is not currently a problem in the Great Lakes basin, in higher densities, it could pose a 

threat to the functionality of infrastructure.

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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 √
777

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 6
778

native species

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

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)?

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
779

Scientific Name: Hymenomonas roseola

Common Name: Coccolithophorid

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low 

Comments: Hymenomonas roseola can reach high abundances in ponds, small lakes, and the backwaters of polluted 

rivers, particularly in eutrophic conditions. Hymenomonas roseola is unlikely to have similar abundances in large 

lakes, so it is unclear if it will have similar negative impacts in the Great Lakes (Stoermer and Sicko-Goad 1977).

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Hymenomonas roseola can reach high abundances in ponds, small lakes, and the backwaters of polluted rivers, 

particularly in eutrophic conditions. Hymenomonas roseola does not have a high success rate in large lakes 

(Stoermer and Sicko-Goad 1977).

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)

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 √

Hymenomonas roseola can reach high abundances in ponds, small lakes, and the backwaters of polluted rivers, 

particularly in eutrophic conditions. In instances of high abundance, the impact of H. roseola on predator-prey 

relationships is unknown. The impact on predator-prey relationships is less likely in the Great Lakes because H. 
780

roseola is known to occur primarily in the littoral region of larger lakes and does not reach high abundances in 

large bodies of water (Stoermer and Sicko-Goad 1977).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

The only species of the genus Hymenomonas in the Great Lakes is H. roseola, and there is only one other species of 

its order found in the Great Lakes, making hybridization unlikely.

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

Hymenomonas roseola thrives in eutrophic conditions, exacerbating problems associated with nutrient pollution. 

The presence of H. roseola is an effect of eutrophication, however, and not a cause.

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
781

1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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
782

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
783

Not significantly 0 √

Unknown U

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

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)?

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
784

Scientific Name: Nitellopsis obtusa

Common Name: starry stonewort

Environmental: Moderate

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Mats of N. obtusa can act like a commercial benthic barrier and lead to the accumulation of phytotoxins that could 

create redox conditions; these conditions have a reduced impact on the rootless N. obtusa as compared to native 

species (Pullman and Crawford 2010).

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., critical reduction, extinction, behavioral 

changes) 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

When it was first reported, N. obtusa was the ninth most frequently collected macrophyte in the St. Clair-Detroit 

River system (Mills et al. 1993, Nicholls et al. 1988). It was recorded at a peak biomass of 259 g m-2 in September, 

when many other macrophytes were declining, giving it a competitive advantage (Nicholls et al. 1988, Schloesser et 

al. 1986).

Once established in inland lakes, N. obtusa forms dense mats of vegetation that completely cover the lake bottom. 

Mats of N. obtusa correspond with a dramatic decrease in the biomass of competing species. Although specific 

surveys have not been conducted yet, there is serious concern for inland lake populations of native species that are 

dependent on lake bottom habitat, including minnows, logperch, darters, clams, and other invertebrates (Pullman 

and Crawford 2010).

There is also research indicating that macrophyte species have a strong influence on phytoplankton through

allelopathic interactions (Hilt et al. 2010, Mulderij et al. 2007, Pullman and Crawford 2010).

In Sweden, N. obtusa dies off in the winter, which reduces the ability of slow colonizers like the isopod Asellus and 

amphipod Gammarus to establish significant populations in this habitat. As a result, it typically hosts many 

chironomids, while Chara tomentosa harbors more amphipods and isopods (Hargeby 1990). 

Dense mats of N. obtusa directly impact the habitat used by native fish for spawning. Bass and sunfish are known to 

regularly spawn in dense growths of native Chara species, but these spawning behaviors did not occurs in 

correspondingly dense growths of N. obtusa (Pullman and Crawford 2010). 

Does it alter predator-prey relationships? 
785

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)

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

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

There is no indication that N. obtusa is affecting Great Lakes native populations genetically, but it has been 

proposed that the population of N. obtusa in the Great Lakes represents a unique phenotype from its native 

population in Europe (Pullman and Crawford 2010).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Nitellopsis obtusa has been associated with increased water clarity in inland lakes, which could in part be due to 

their association with zebra mussels (Dreissena polymorpha) as a favored substrate. In spite of increased water 

clarity from the mussels, the dense growth of N. obtusa actually reduces light availability for other submersed flora 

(Pullman and Crawford 2010). 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U
786

In Lake Majcz Wielki, Poland, zebra mussels settle at densities of 1000 per m2 on N. obtusa and Stratiotes aloides, 

and at much lower densities on other plants (Lewandowski and Ozimek 1997).

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

While N. obtusa negatively affects water quality for other macrophyte and phytoplankton species, there is no 

evidence to suggest that the quality of drinking water is significantly affected. However, there have been no studies 

conducted to specifically address this issue.

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture)?
787

Yes, it has caused significant damage to one or more markets or economic sectors 6

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 a large economic investment from inland lake communities to manage and control invasions of N. obtusa. 

This is both to protect boat owners from potential damage to their vessels, as well as to maintain economically 

important recreational fishing and swimming areas (Pullman and Crawford 2010).

Nitellopsis obtusa also poses a risk of entanglement to swimmers, who also are displeased with this alga’s rough 

texture.

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

Nitellopsis obtusa is a relatively new invasion, particularly to the inland lakes. The long-term impacts on the 

economic value lake property cannot yet be properly assessed.

As one of the filamentous algae that frequently detaches from the bottom to form a floating mat, N. obtusa

contributes both to lake “scum” and mats that wash up on beaches.

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

BENEFICIAL EFFECT

Does it ac 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 √
788

Not significantly 0

Unknown U

Nitellopsis obtusa is becoming regarded as the most aggressive invasive species in inland lakes and has been 

recorded replacing other nonnative and nuisance species, including Eurasian watermilfoil (Myriophyllum 

spicatum), fanwort (Cabomba caroliniana), and curly leaf pond weed (Potamogeton crispus) (Pullman and Crawford 

2010). Hilt et al. (2010) suggested that N. obtusa could be an effective means of restoration for deep lakes in its 

native range.

It is known to have allelopathic properties towards cyanobacteria (Berger and Schagerl 2004).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Nitellopsis obtusa has a significant stratigraphical account that extends back to the early Quaternary and can be 

useful in biogeographical research, and well as in tracing evolutionary lineages (Soulie-Marsche et al. 2002).

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

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, 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

Nitellopsis obtusa is considered a rare species in Japan and parts of Europe (Blindow 1994, Golombek 1998, Kato 

et al. 2005 Raabe 2006, Simons et al. 1994).
789

In European regions, this species can be a good substrate for epiphytes, even though it is frequently covered in 

marl, which is a byproduct of photosynthesis formed when bicarbonate is used (Brindow 1987).

Nitellopsis obtusa increases in the Netherlands have been associated with increases in populations of red-crested 

pochards (Netta rufina), which feed preferentially on this species, possibly because it is a good source of calcium 

and sulfur (Ruiters et al. 1994).

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
790

Scientific Name: Pleurosira laevis

Common Name: Diatom 

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Pleurosira laevis has been recorded to dominate phytoplankton assemblages in other locations in the United States. 

However, these occurrences were in stream ecosystems and it is unclear if P. laevis is capable of out-competing 

native species in Lake Michigan (Crayton and Sommerfeld 1979). Additionally Ferreira et al. (1999) documented P. 

laevis growing in homogenous communities with low species richness in Portugal. The population recorded in Lake 

Michigan by Wujek and Welling (1981) composed approximately 1% of the overall algal abundance and was codominant with several native taxa.

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)

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 √

The abundance of P. laevis and association with Cladophora in tributary environments could impact predator-prey 

relationships by limiting nutrient and light resources for native algal species. However, presently there is no 

conclusive research on these trophic interactions and it is not apparent if it would be possible in the Lake Michigan 

ecosystem (Kociolek et al. 1983). 
791

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Pleurosira laevis is the only species in its genus in the Great Lakes making hybridization unlikely. 

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

It is not clear if P. laevis alters water quality. However, this species was found close to a water treatment plant in 

Lake Michigan and has been observed in other locations where chloride or nitrogen concentrations were elevated 

(Wujek and Welling 1981).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
792

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
793

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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 √

Pleurosira laevis might act as an indicator of poor water quality, as it thrives in water with increased nitrate or 

chloride (Smucker 2011).
794

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

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)?

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
795

Scientific Name: Skeletonema potamos

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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√

Skeletonema potamos has been recorded at densities up to 20,140 cells/ml in the Little Miami River, Cincinnati, 

OH. In the late summer, during the highest density, S. potamos accounted for approximately 35% of the centric 

diatoms in the Little Miami River (Weber 1970). Skeletonema potamos is considered a pollution tolerant species 

and may be more productive than native species in polluted waters (Nicholls et al. 1983). The implications of 

competition with the native diatom taxa were not specifically investigated.

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)

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 

Skeletonema potamos grows in relatively short (1-10 cells) chains. In polluted water S. potamos grew in chains 2-4 

cells long and under those conditions was considered a functional food chain species (Nicholls et al. 1983). The 

presence of this species as a food source has not been addressed with regards to the specific impact on predators or 

other prey species.
796

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

0 ≥2

Unknown 1 ≥1
797

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
798

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Skeltonema potamos does not directly impact water quality; however, as a pollution tolerant species it can often be 

used as an indicator of poor water quality (Nicholls et al. 1983).
799

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

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, 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
800

Scientific Name: Skeletonema subsalsum

Common Name: Diatom

Environmental: Low 

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Skeletonema subsalsum was recorded to be 17.6% of the biomass in the spring diatom blooms in Lake Erie. These 

blooms were dominated by native taxa and there was no indication that S. subsalsum was out-competing native 

species (Reuter 1979). In its native range, S. subsalsum occurs in brackish waters. While it is able to grow and 

reproduce in freshwater, S. subsalsum does not undergo cell enlargement in freshwater as it does in brackish 

environments (Balzano et al. 2011). 

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
801

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
802

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
803

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
804

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, 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
805

Scientific Name: Sphacelaria fluviatilis

Common Name: Brown alga

Environmental: Low

Socio-Economic: Low 

Beneficial: Low

Comments: Limited research has been conducted on the population of Sphacelaria fluviatilis in Gull Lake, 

Michigan. It was identified over 40 years ago, and while a population is still present, it does not seem to be 

expanding because it only undergoes vegetative reproduction.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

The population in Gull Lake, Michigan is small and unlikely to provide a significant food for any lake herbivores 

(Wehr and Sheath 2003).

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 which may be irreversible or has led to the 6
806

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

The population of Sphacelaria fluviatilis in Gull Lake, MI is not known to reproduce sexually and therefore is not 

expected to affect the genetic composition of native algal populations (Wujek et al. 2006).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
807

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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 √
808

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 6
809

native species

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

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, 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
810

Scientific Name: Sphacelaria lacustris

Common Name: Brown alga

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown

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., critical reduction, extinction, behavioral 

changes) 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

Sphacelaria lacustris was originally reported in Lake Michigan at depths ranging from 5-15 m (Schloesser and Blum 

1980). At the time of that study it was not interfering with the growth of the native Cladophora glomerata, which 

created a dense cover on rocks at depths of 1-5 m. Since the Dreissena invasion and increased penetration of 

sunlight, Cladophora now can be found at depths greater than 20 m (C. Brooks pers. comm., Malkin et al. 2008). 

There has been no more recent research to assess S. lacustris impacts on Cladophora given this expanded range of 

suitable habitat.

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)

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

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 which may be irreversible or has led to the 6
811

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Sphacelaria lacustris does not reproduce sexually in the Lake Michigan population and is therefore unlikely to affect 

native populations genetically (Schloesser and Blum 1980).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
812

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
813

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Does the species remove toxins or pollutants from the water or otherwise increase water quality?
814

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

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, 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
815

Scientific Name: Stephanodiscus binderanus

Common Name: Diatom 

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Low

Comments: A recent study conducted by Hawrshyn et al. (2012) in Lake Simcoe, Ontario found historical 

microfossils of S. binderanus dating back the 17th century. This discovery brings the status of S. binderanus as a 

nonindigenous species in the Great Lakes basin into question. Stephanodiscus binderanus may be better classified as 

a range expander rather than as a nonidigenous species. 

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Stephanodiscus bineranus thrives in phosphorous rich and silica depleted waters. It reached peak abundance in 

Lake Michigan and Lake Ontario in the 1950s and 1960s, but since efforts to improve water quality began in the 

1970s and grazing from the Dreissena invasion increased in the 1980s, there have been marked declines in S. 

binderanus populations (Barbiero et al. 2006, Stoermer et al. 1996). In a more recent survey conducted in 2001, S. 

binderanus was not found Lakes Superior, Michigan, or Huron. However, S. binderanus was present in Lake 

Ontario and had a few very large populations in Lake Erie reaching biovolumes of 32,028 ug/mL (Barbiero and 

Tuchman 2001).

The introduction and establishment of S. binderanus, along with Actinocyclus normanii f. subsalsa, were 

accompanied by the reduction of five native diatoms (S. transilvanicus, Cyclotella comta, C. michiganiana, C. 

ocellanta, and C. stelligera) in Lake Ontario (Edlund et al. 2000, Stoemer et al. 1985). While it is unclear if these 

local population reductions were due entirely or in part to competition with exotic taxa, the appearance of S. 

binderanus in Lake Ontario spring diatom collections tends to be associated with the absence or rare occurrence of 

C. comta, C. michiganiana, C. ocellanta, and C. stelligera (USEPA 2012). These native species reappear at sample 

sites in summer, when S. binderanus is no longer found (USEPA 2012), suggesting that strong seasonal competition 

may drive fluctuations in native diatom abundances.

Does it alter predator-prey relationships? 

Yes, and it has resulted in significant adverse effects 6
816

(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)

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

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High
817

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Stephanodiscus binderanus has clogged filters at water filtration plants in both Chicago and Montreal (Brunel 1956, 

Stoermer and Yang 1970, Vaughn 1961).

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

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Stephanodiscus binderanus has caused taste and odor problems at water filtration plants within the Great Lakes 

(Stoermer et al. 1996).

At high abundances, S. binderanus reduces water quality (Stoermer et al. 1985).

Does it harm 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 

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 

Not significantly 0 √

Unknown U 
818

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 

Stephanodiscus binderanus forms surface scums and, at high abundances, negatively affects recreational uses of the 

lake (Stoermer et al. 1985).

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 

Stephanodiscus binderanus forms surface scums and, at high abundances, negatively affects recreational uses of the 

lake (Stoermer et al. 1985).

Socio-Economic 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

BENEFICIAL EFFECT

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

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

Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal activity)?
819

Yes, it is commonly employed recreationally and has some perceived value for local communities and/or 

tourism

6

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Stephanodiscus binderanus has been used to assess historical pollution and climate conditions both in the Great 

Lakes and in Lake Baikal, Russia (Edlund et al. 1995, Stoermer et al. 1985).

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

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, 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
820

Scientific Name: Stephanodiscus subtilis

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Stephanodiscus subtilis has been recorded as an abundant diatom taxon in Lake Erie and Lake Ontario during 

summer and early fall blooms (Mille and Lowe 1983). However, the specific impact of these blooms on native 

species was not investigated.

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)

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

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 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
821

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

1
822

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

The distribution of S. subtilis has been primarily nearshore areas or eutrophic waters with a considerable amount of 

chloride contamination, but it does not itself cause a reduction in water quality (Stoermer and Yang 1970).

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
823

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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 √

Stephanodiscus subtilis may serve as an indicator of poor water quality (Stoermer and Yang 1970).

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
824

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, 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
825

Scientific Name: Thalassiosira baltica

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

The introduction and establishment of T. baltica were accompanied by the extirpation of the native diatom 

Stephanodiscus niagarae in Lake Ontario, both estimated as occurring around 1988 (Edlund et al. 2000, Julius et 

al. 1998). It is not clear whether T. baltica caused this local extinction or if lake change or another biological 

explanation (e.g., silica limitation inhibiting sexual reproduction in S. niagarae) drove the observed species turnover 

(Edlund et al. 2000).

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
826

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6
827

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
828

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
829

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, 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
830

Scientific Name: Thalassiosira lacustris

Common Name: diatom

Environmental: Low 

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

There have been reports of blooms of T. lacustris in Tokyo Bay, but these high densities have never been recorded in 

the Great Lakes basin (Hasle 1978).

It is able to survive at salinities as low as 0.5‰ but only grows rapidly above 8‰. This is likely a limiting factor on 

the distribution of T. lacustris in the Great Lakes (Hasle 1978).

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)

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

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 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 1
831

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
832

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
833

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
834

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, 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
835

Scientific Name: Thalassiosira pseudonana

Common Name: diatom 

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Thalassiosira pseudonana has been found in the Great Lakes basin composing 31% of the periphyton community and 

90% of the plankton community (Lowe and Busch 1975). McQuoid (2005) reported growth of T. pseudonana after 2 

years in storage, indicating the presence of a dormant state that seems to be triggered by temperature and light 

cues. This dormant state could give T. pseudonana a competitive advantage over native species, however this has 

not been specifically researched.

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
836

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
837

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
838

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

Thalassiosira pseudonana was found to be useful for mariculture because it has a high fatty-acid compostion 

(Volkman et al. 1989).

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Thalassiosira pseudonana is used as a model organism for silica biomineralization because its entire gene 

sequenced has been published. Biomineralizaton is a growing field that is using diatoms to accelerate silica 

formation and form macromolecular assemblies that might act as structure-directing templates (Sumper and 

Brunner 2008).

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 6
839

native species

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

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, 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
840

Scientific Name: Thalassiosira weissflogii

Common Name: diatom

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Outside the Great Lakes, T. weissflogii is one of several species that has been associated with red tides (Yamaoka et 

al 1998). In California, Thalassiosira sp. was reported to clog the gills of fish during these red tide events, which led 

to a reduction in fish populations (Núñez-Vázquez et al. 2011).

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., critical reduction, extinction, behavioral 

changes) 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

Stoermer (1978) reported T. weissflogii as a common diatom along the shores of Lake Michigan and bays of Lakes 

Erie and Ontario. The distribution of T. weissflogii thrives at salinities ranging from 5‰ to marine conditions, but 

this physiological requirement limits its distribution and impact.

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)

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

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 which may be irreversible or has led to the 6
841

decline or extinction of one or more native species

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
842

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
843

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Thalassiosira weissflogii has a high lipid content, which makes it a viable option for mariculture (Ishida et al. 

2000).

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 √
844

Not significantly 0

Unknown U

Thalassiosira weissflogii has a high tolerance for CO2, making it a good candidate eliminating CO2 during 

treatment of emissions from industrial factories (Ishida et al. 2000).

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, 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
845

Scientific Name: Ulva flexuosa subsp. flexuosa and flexuosa subsp. paradoxa

Common Name: green alga

Environmental: Moderate

Socio-Economic: Moderate

Beneficial: Moderate

Comments: Ulva flexuosa is considered primarily a marine species but has a wide range of salinity and nutrient 

tolerance. The Great Lakes range of U. flexuosa is currently limited to Muskegon, Mona and White Lake. However, 

as it is able to form blooms in Muskegon Lake—which has a lower conductivity than Lake Erie—there is potential 

for it to thrive in other locations in the Great Lakes (Lougheed and Stevenson 2004).

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

The first recorded bloom of U. flexuosa in the Great Lakes occurred in Muskegon Lake, where it dominated the 

macrophyte community.

Ulva flexuosa supports a relatively low density and diversity of epiphytes compared to native macrophytes 

(Lougheed and Stevenson 2004). Blooms of U. flexuosa in Europe have been associated with the extirpation of 

species of red algae and epiphytes (Schories and Lotze 1997).

It is hypothesized that shading of macrophytes could become problematic in Great Lakes if blooms were sustained 

for long periods of time (Lougheed and Stevenson 2004).

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)

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
846

Not significantly 0 √

Unknown U

When U. flexuosa blooms in nutrient rich marine coastal areas, a decline in biodiversity of native algae has been 

observed, as well as cascading food web effects that negatively impact macro invertebrates, shorebirds and fish 

(Lougheed and Stevenson 2004).

If U. flexuosa was to replace Oedogonium and Cladophora, which support many diatoms, food webs depending on 

such epiphytes could be negatively affected (Lougheed and Stevenson 2004).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Ulva flexuosa has formed dense, free floating mats during bloom conditions in Muskegon Lake. In other locations, 

mats of U. flexuosa have also impacted abiotic conditions, as the dense algal cover alters redox conditions and 

chemical interactions between the sediment and water column (Lougheed and Stevenson 2004). 

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact
847

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Ulva flexuosa is known to foul a variety of permanent man-made structures and boats. This can lead to expensive 

repairs of fouled boat motors. There are even reports of it growing on boats treated with antifouling paint 

(Kolwalker et al. 2007, Lougheed and Stevenson 2004).

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Mats of U. flexuosa washed up on the shores of Muskegon Lake during the bloom of 2003. In addition to the cost to 

boat users, these blooms also decreased the value of lakeshore property and discouraged tourism (Lougheed and 

Stevenson 2004).
848

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

Mats of U. flexuosa washed up on the shores of Muskegon Lake during the bloom of 2003 discouraged beach use by 

tourists (Lougheed and Stevenson 2004).

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 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

BENEFICIAL EFFECT

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

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

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 6
849

tourism

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Ulva flexuosa is used as a bioindicator for metal contamination, including lead and iron (Ho 1987, Tabudravu et al. 

2002).

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

Ulva flexuosa was found to be an economically efficient species for bioabsorption in industrial settings. It could be 

used as an eco-friendly alternative for wastewater treatment in dye manufacturing, tannery, textile, and cosmetic 

industries (Sivasamy et al. 2012).

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, 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
850

Scientific Name: Ulva intestinalis

Common Name: green alga, grass kelp, gut weed

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

Comments: Ulva intestinalis had caused serious negative impacts in marine and coastal areas outside of the Great 

Lakes region. However, the harmful bloom development seen in marine environments is rare in inland, freshwater 

populations (Messyasz and Rybak 2011).

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Ulva intestinalis has the potential to be a superior macrophyte competitor. Lotze et al. (2000) found that this species 

can produce a propagule bank capable of surviving winter conditions in the Baltic Sea. Such a seed bank allowed U. 

intestinalis to begin growing two months earlier than many native species, enabling it to escape herbivory and 

nutrient competition.

In Indian coastal areas, filamentous forms of U. intestinalis have been associated with lower faunal community 

diversity than areas with more bushy algae (Yogamoorthi 1998).

In European coastal waters, epiphytic benthic diatoms prefer growing on monosiphonous forms of U. prolifera to 

colonizing broad and flattened forms of U. intestinalis (Holt 1980).

Epibionts like Ulva can also exert increased drag on snails living in high flow conditions, causing them to invest 

more energy in foot muscles and less in growth (Wahl 1996).

In conditions of nitrogen scarcity in estuaries and lagoons on the coast of southern California, U. intestinalis can 

out-compete Ulva expansa (Fong et al. 1996).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 1
851

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

In marine and coastal waters, U. intestinalis may form green tides and biofouling mats that cause cascading effects 

throughout the food web. Ulva intestinalis mats can deplete the available oxygen in the water and increase the

production of hydrogen sulphide in the sediment, which can cause population declines in other fauna and flora 

(Bäck et al. 2000, Cummins et al. 2004, Vadas and Beal 1987).

Mats can also shade out native seagrass beds and negatively impact their corresponding communities, as well 

disrupt feeding by wading birds (Raffaeli et al. 1998).

Furthermore, some marine forms of U. intestinalis are more difficult for grazers to handle and ingest than species 

with more frond structure (Watson and Norton 1985).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Ulva intestinalis mats can deplete the available oxygen in the water and increase the production of hydrogen 

sulphide in the sediment (Baeck et al. 2000).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U
852

Romano et al. (2003) observed in England an increase in friction drag with the presence of Ulva intestinalis mats, 

causing a 10% to 56% reduction in current velocities. There was also a significant reduction is sediment erosion. 

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

1 √
853

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0

Unknown U

Mats of U. intestinalis in England caused an order of magnitude decrease in abundance of the economically 

important bivalve Cerastoderma edule (Romano et al. 2003).

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

Ulva intestinalis is one of the species that contributes to the 109 kg of seaweed removed every year from 

recreational beaches in France (Blomster et al. 2002).

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

BENEFICIAL EFFECT

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

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 √
854

Unknown U

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
855

Scientific Name: Ulva prolifera

Common Name: sea lettuce

Environmental: Low

Socio-Economic: Low

Beneficial: Low

Comments: While blooms of U. prolifera have had significant negative environmental and socio-economic impacts 

in Asia (Xu et al. 2012), these impacts have not been realized in the Great Lakes. Moreover, the persistence of a 

population in the Great Lakes region is still uncertain.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 recent years, large blooms (over 1 million tons) of Ulva prolifera have lead to declines in seagrass beds due to 

shading, disruption of feeding by wading birds, and an overall loss of algal biodiversity (Xu et al. 2012). These 

negative effects have not been realized in the Great Lakes because of the small and uncertain nature of the U. 

prolifera population (Mills et al. 1993).

Ulva prolifera mats that formed on intertidal sandflats in Scotland were found to significantly decrease the 

macrofaunal diversity. These negative impacts were particularly on species that use planktonic larval recruitment

(Bloam et al. 2000).

Ulva prolifera has been found to release allelochemicals that inhibited growth and photosynthesis in native 

competitors (Xu et al. 2012).

In intertidal flats of the Wadden Sea, dense mats of E. prolifera and other Enteromorpha spp. have been associated 

with fewer occurrences of brown and red algae (Schories et al. 1997).

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

1
856

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

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

In China, massive blooms covered large extents of the sea bottom (13,000-30,000 km2) and decoupled 

biogeochemical cycles between the sediments and the water column. These chemical changes exposed native flora 

and fauna to oxygen deficiency and anoxia (Xu et al. 2012).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High
857

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

China has been experiencing an increase in U. prolifera-dominated green tides since 2007, with a notable event just 

prior to the 2008 Beijing Olympics. There were significant impacts on the tourism industry as well as on 

aquaculture. The cost for emergency mitigation action in China during the 2008 bloom was estimated to cost 

around 200 million Euro. According to Nai-hao et al. (2011) green tides are responsible for aquaculture losses of 

approximately 86 million Euro annually.

In Spanish waters, U. prolifera is one of the species responsible for fouling intertidal oyster culture systems, 

although this problem can be partly controlled by snail grazing (Cigarria et al. 1998).
858

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

China has been experiencing an increase in U. prolifera-dominated green tides since 2007, with a notable event just 

prior to the 2008 Beijing Olympics. There were significant impacts on the tourism industry (Nai-hao et al. 2011).

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

BENEFICIAL EFFECT

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

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

Zhuang et al. (2012) proposed the use of U. prolifera as green feedstock, biofuel substitute, and chemical 

production. Ulva prolifera is edible and is considered an economically viable food option in Japan and China (Dan 

et al. 2002).
859

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
860

A.10 Amoebae

Scientific Name: Psammonobiotus communis

Common Name: Testate amoeba

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Psammonobiotus communis was first detected in the Great Lakes through surveys of beach sand in 2001 and 2002, 

in which this amoeba was the most abundant psammobiont (obligate sand-dwelling) testate rhizopod collected (> 

100 specimens total) (Nicholls and MacIsaac 2004). However, compared to abundance in marine beaches, the 

density of P. communis in the Great Lakes has been relatively low (Nicholls and MacIsaac 2004).

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)

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 √

While the impacts of P. communis in the Great Lakes have not yet been studied, testate amoebae tend to prey upon 

and modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier 

and Parkinson 1984, Schönborn 1992).
861

Furthermore, selective grazing by testate amoebae may influence microbial community taxonomic composition and 

metabolic activity (Bonkowski 2004, Sherr et al. 1992).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

While the impacts of P. communis in the Great Lakes have not yet been studied, testate amoebae tend to prey upon 

and modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier 

and Parkinson 1984, Schönborn 1992).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
862

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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 
863

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
864

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

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, 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

In studies outside the Great Lakes, testate amoebae have been used as indicators of ecosystem condition and 

function (e.g., Fournier et al. 2012).

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
865

Scientific Name: Psammonobiotus dziwnowi

Common Name: Testate amoeba

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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 √

Psammonobiotus dziwnowi was first detected in the Great Lakes through surveys of beach sand in 2001 and 2002 

at “moderate” numbers (63 individuals total) (Nicholls 2005, Nicholls and MacIsaac 2004). However, compared to 

abundance in marine beaches, densities of psammobiont testate rhizopods in the Great Lakes are relatively low 

(Nicholls and MacIsaac 2004).

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)

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 √

While the impacts of P. dziwnowi in the Great Lakes have not yet been studied, testate amoebae tend to prey upon 

and modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier 

and Parkinson 1984, Schönborn 1992).

Furthermore, selective grazing by testate amoebae may influence microbial community taxonomic composition and 

metabolic activity (Bonkowski 2004, Sherr et al. 1992).
866

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U √

While the impacts of P. dziwnowi in the Great Lakes have not yet been studied, testate amoebae tend to prey upon 

and modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier 

and Parkinson 1984, Schönborn 1992).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
867

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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 
868

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
869

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

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, 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

In studies outside the Great Lakes, testate amoebae have been used as indicators of ecosystem condition and 

function (e.g., Fournier et al. 2012).

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
870

Scientific Name: Psammonobiotus linearis

Common Name: Testate amoeba

Environmental: Unknown

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

Psammonobiotus linearis was first detected in the Great Lakes through surveys of beach sand in 2002 at “low” 

numbers (Nicholls and MacIsaac 2004). Compared to abundance in marine beaches, densities of psammobiont 

testate rhizopods in the Great Lakes are relatively low overall (Nicholls and MacIsaac 2004).

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)

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

While the impacts of P. linearis in the Great Lakes have not yet been studied, testate amoebae tend to prey upon and 

modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier and 

Parkinson 1984, Schönborn 1992).

Furthermore, selective grazing by testate amoebae may influence microbial community taxonomic composition and 

metabolic activity (Bonkowski 2004, Sherr et al. 1992).
871

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

While the impacts of P. dziwnowi in the Great Lakes have not yet been studied, testate amoebae tend to prey upon 

and modify microbial populations, accelerate nutrient cycling, and be consumed by other organisms (e.g., Lousier 

and Parkinson 1984, Schönborn 1992).

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
872

1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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 6 
873

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
874

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

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, 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

In studies outside the Great Lakes, testate amoebae have been used as indicators of ecosystem condition and 

function (e.g., Fournier et al. 2012).

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
875

A.11 Parasites & Diseases

Scientific Name: Acineta nitocrae

Common Name: A suctorian ciliate

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Acineta nitocrae is commensal with the Great Lakes nonindigenous copepods Nitokra hibernica and N. incerta 

(Grigorovich et al. 2001). However, high densities could potentially affect hosts’ exoskeletons, movement, 

respiration, nutrient uptake, and reproduction (Grigorovich et al. 2001). With the exception of Lake Superior,

Nitokra species are abundant throughout the Great Lakes. It is possible that these copepods will transport A. 

nitocrae to Lake Superior if they continue to spread (Grigorovich et al. 2001, Hudson et al. 1998, Lesko et al. 2003).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
876

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
877

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
878

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
879

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

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, 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
880

Scientific Name: Aeromonas salmonicida

Common Name: Furunculosis, ulcer disease, erythrodermatitis

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

In the Great Lakes and connecting tributaries, A. salmonicida has had a larger impact on native salmonids than on 

introduced salmonids. It particularly affects Atlantic salmon (Salmo salar), brook char or trout (Salvelinus 

fontinalis), lake char (Salvelinus namaycush), grayling (Thymallus arcticus), and lake whitefish (Coregonus 

clupeaformis). It secondarily affects other native non-salmonid species such as northern pike (Esox lucius), yellow 

perch (Perca flavescens), dace and minnows (Family Cyprinidae), catfish (Family Ictaluridae), sticklebacks (Family 

Gasterosteidae), and sculpins (Family Cottidae) (Crawford 2001, Mills et al. 1993). Aeromonas salmonicida has 

been found to be ubiquitous and established in commercial fish farms, government fish hatcheries, and wild 

populations throughout the Great Lakes and connecting tributaries (Bruneau et al. 1999). However, the bacterium 

continues to be detected at very low prevalence (GLFHC 2006).

In 2011, A. salmonicida was isolated from a Michigan state hatchery for the first time since 2005 and was detected 

in 2% of returning adult Atlantic salmon collected from the St. Mary’s River, Michigan (GLFHC 2012). Following 

elevated mortalities observed in Michigan in 2011, twenty cases of production and brood stock Atlantic salmon were 

tested for pathogens. Aeromonas salmonicida was detected in three of the twenty cases. However, analysis showed 

that furunculosis was not the cause of mortality (GLFHC 2012). Elsewhere in the Great Lakes region, seven of 

fourteen Pennsylvania state hatcheries tested positive for A. salmonicida in 2011 (GLFHC 2012).

Although furunculosis is not reportable in the U.S, it is a reportable disease in Australia (DAFF 2011).

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., critical reduction, extinction, behavioral 

changes) 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

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)

6
881

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

In salmonid hosts that contract furunculosis as a result of infection by A. salmonicida, symptoms can include: 

furuncles, hemorrhaging, enlarged organs, erratic swimming, and lack of feeding (Cipriano and Bullock 2001, 

Crawford 2001). Because of this, infected fish may be more susceptible to predation (Lafferty and Morris 1996). 

However, cascading food web effects as a result of furunculosis infection in the Great Lakes have not been reported.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Aeromonas salmonicida is capable of transferring plasmids that confer drug resistance from one strain to another, 

which has the potential to result in new and more virulent strains of the disease evolving and appearing among 

salmonid populations (Bakke and Harris 1998).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U
882

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Aeromonas spp. are significant human pathogens causing extra-intestinal infections in various organs (von 

Graevenitz and Mensch 1968). However, A. salmonicida is a fish pathogen and has not been associated with human 

infection (Janda and Abbott 1996).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

1 √
883

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

Not significantly 0

Unknown U

Nationwide, infectious diseases cost the Canadian Aquaculture industry over $400 million annually with 

furunculosis accounting for approximately 10% in losses annually (Nash et al. 2006). The proportion of these losses 

specific to the Great Lakes region has not been reported.

The economic impact of pathogen screening requirements for the baitfish and aquaculture industries (see 

Management) are likely to be significant, but have not been documented.

Non-native Great Lakes wild and cultured salmonid populations susceptible to A. salmonicida infection include 

coho salmon (Oncorhynchus kisutch), brown trout (Salmo trutta), chinook salmon (O. tshawytscha), and rainbow 

trout (O. mykiss) (GLFHC 2006, GLFHC 2012). Prevalence of A. salmonicida in these species is low to moderate 

and mortalities are rare. 

Atypical A. salmonicida is introduced and common among goldfish in Australia (Humphrey and Ashburner 1993, 

Trust et al. 1980). There have been major epidemics of this bacterium in salmonid populations, particularly in fish 

farms and hatcheries in the United Kingdom, Norway, and on the west coast of North America in British Columbia 

and Washington State (Bakke and Harris 1998, Morrison 1995).

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

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

BENEFICIAL EFFECT

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 1
884

effectiveness

Not significantly 0 √

Unknown U

In lab environments, the A. salmonicida bacterium can be pathogenic to zebra mussels (Dreissena polymorpha). In 

the wild, mussel populations may act mainly as reservoirs for A. salmonicida, and further research is necessary to 

understand the ecology of the interaction between these species (Gu and Mitchell 2002, Maki et al. 1998).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
885

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
886

Scientific Name: Bothriocephalus acheilognathi

Common Name: Asian tapeworm

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Historically, B. acheilognathi has had a limited distribution in the Great Lakes—infecting several native species 

including fathead minnow (Pimephales promelas), bluntnose minnow (P. notatus), and golden shiner (Notropis 

crysoleucas) (Choudhury et al. 2006, Marcogliese 2008).

Bothriocephalus acheilognathi infects other U.S. species of importance including roundtail chub (Gila robusta) 

(Brouder 1999), the endangered bonytail chub (G. elegans) (Hansen et al. 2006), and the endangered humpback 

chub (G. cypha) (Choudhury et al. 2004, Hansen et al. 2006) and is listed as a “Pathogen of Regional Importance” 

in the southwestern U.S. (USFWS 2012).

Bothriocephalus acheilognathi displays a low degree of host specificity, and has been observed in 102 species in 14 

families and 7 orders worldwide (Dove and Fletcher 2000, Maldonado 2003).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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
887

Parasitic nutrient competition may lead to reduced body condition and growth, anemia, and temperature-dependent 

mortality. Pathogenic effects include intestinal inflammation, protein depletion, and altered digestive enzyme 

activity (Marcogliese 2008). Because of this, infected fish are more susceptible to predation (Lafferty and Morris 

1996). However, cascading food web effects have not been reported as a result of B. acheilognathi infection in the 

Great Lakes.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 1

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0
888

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Tapeworm-parasitized fish are safe to consume, provided the fish are thoroughly cooked, smoked, or pickled 

(Alexander 2008).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Golden shiner and fathead minnow are the most common commercially farmed baitfish in the United States (ODNR 

2012).

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 √
889

Unknown U

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

BENEFICIAL EFFECT

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

Common carp (Cyprinus carpio) and grass carp (Ctenopharyngodon idella) are principle hosts for Asian tapeworm 

(Dove and Fletcher 2000), infection of which could lead to population reductions in those species.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

Does the species have some medicinal or research value (outside of research geared towards its control)?
890

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

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

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, 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
891

Scientific Name: Dactylogyrus amphibothrium

Common Name: Monogenetic gill fluke

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Dactylogyrus amphibothrium displays host specificity for percids, particularly in the genus Gymnocephalus (Cone 

et al. 1994); however, outside its native region, it has also been recorded on cyprinids (Gibson et al. 1996, 

Kakacheva-Avramova 1977). Yellow perch (Perca flavescens) are potentially also at risk for infection by this 

monogenean parasite, although no such infection has yet been recorded (Cone et al. 1994).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 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 1
892

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
893

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
894

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 the Great Lakes, D. amphibothrium appears to be host specific to the introduced Eurasian ruffe (Gymnocephalus 

cernua) (Cone et al. 1994), infection of which could lead to population reductions. However, no such effects have yet 

been realized in the Great Lakes.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 √
895

Unknown U

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, 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
896

Scientific Name: Dactylogyrus hemiamphibothrium

Common Name: a monogenetic fluke

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Dactylogyrus hemiamphibothrium is a parasite of percids, particularly in the genus Gymnocephalus (U. S. 

Department of the Interior 1993); it has also been reported to parasitize the genus Perca (Gibson et al. 1996). Due 

to host specificity for Eurasian ruffe (G. cernua) in its native range, D. hemiamphibothrium is unlikely to exert 

negative impacts on native fish species in the Great Lakes (U.S. Department of the Interior 1993).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 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 1
897

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 1
898

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
899

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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 the Great Lakes, D. hemiamphibothrium appears to be host specific to the introduced Eurasian ruffe 

(Gymnocephalus cernua) (U.S. Department of the Interior 1993), infection of which could lead to population 

reductions. However, no such effects have yet been realized in the Great Lakes.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 √
900

Unknown U

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, 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
901

Scientific Name: Dugesia polychroa

Common Name: A flatworm

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Great Lakes native organisms consumed by Dugesia polychroa include tubificids, gastropods, amphipods, and 

isopods (Boddington and Mettrick 1974).

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., critical reduction, extinction, behavioral 

changes) 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

Throughout much of its distribution in North America, D. polychroa feeds primarily on oligochaetes (Boddington 

and Mettrick 1974), while the native D. tigrina are is believed to feed extensively on gastropods (Reynoldson 1974). 

However, in Toronto Harbour, Ontario, D. polychroa and D. tigrina are found to coexist; the latter is found at lower 

densities at each locality, suggesting potential intra-specific competition between the triclads (Boddington and 

Mettrick 1974).

In Britain, competition for food resources, specifically gastropods, is observed between D. polychroa and D. tigrina 

(Reynoldson and Davies 1970).

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)

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
902

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
903

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
904

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

BENEFICIAL EFFECT

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

Planarians have been used in medicinal and scientific research in topics including, but not limited to, genomics 

(Alvarado and Newark 1999), stem cells (Newark and Alvarado 2000, Reddien and Alvarado 2004), and cancer 
905

(Oviedo et al. 2008), as well as for modeling morphogenesis, restoration of pattern and polarity, control of tissue 

proportions, and tissue homeostasis (Salo et al. 2009).

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

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, 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
906

Scientific Name: Glugea hertwigi

Common Name: A microsporidian parasite

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

In the Great Lakes, G. hertwigi exhibits host specificity for rainbow smelt (Osmerus mordax) (Muzzall and Whelan 

2012), a species which competes with and feed on several important native and non-native species in the Great 

Lakes food web. Glugea hertwigi is known to damage the mesentery, intestinal organs, and gonads in rainbow 

smelt. Such parasitism by G. hertwigi can be lethal or non-lethal (Pekcan-Hekim et al. 2005). Infections in the 

stomach and intestine can cause starvation and intestinal poisoning (Chen and Power 1972, Delisle 1972, Mills et 

al. 1993, Pekcan-Hekim et al. 2005, Scarborough and Weidner 1979). Die-offs of rainbow smelt as a result of G. 

hertwigi infection have the potential to indirectly cause significant (generally beneficial) cascading food web effects 

in the Great Lakes (see Beneficial Effects).
907

Great Lakes native Atlantic salmon, lake trout, and other salmonids are known to prey heavily upon rainbow smelt 

(EPA 2008). Osmerus mordax is believed to have aided the growth of landlocked Atlantic salmon in Maine (Havey 

1973). Die-offs of O. mordax as a result of G. hertwigi could have adverse health effects on Great Lakes salmonids.

Furthermore, while there is no evidence of native coregonid infection in the Great Lakes, G. hertwigi is known to 

parasitize Coregonus species in northern Russian lakes (Dykova 1995).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
908

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Glugea hertwigi has been implicated in mass mortalities of rainbow smelt (O. mordax; see GLANSIS rainbow smelt 

fact sheet) in Lake Erie (Nepszy and Dechtiar 1972, Nepszy et al. 1978) and Lake Ontario (A. Dechtiar, unpublished 

data). Mortality events are believed to be seasonal and directly related to parasite prevalence (Dechtiar and Nepszy 

1988). Glugea hertwigi cysts in ovaries of mature rainbow smelt females have also caused greatly reduced egg 

production (Chen and Power 1972). However, it should be noted that the presence of G. hertwigi in rainbow smelt 

in other dieoff events had no significant effect on fecundity or condition, although it did cause growth to slow 

somewhat (Nsembukya-Katuramu et al. 1981). While economic impacts of G. hertwigi on the commercial smelt (see 

Pflieger 1997, Smith 1985) and salmonid (which rely on smelt) fisheries have not been realized, significant impacts 

could be realized if rainbow smelt mortalities were to increase as a result of infection.

In Ontario waters of Lake Erie, G. hertwigi has been isolated at prevalences between 36 and 90%, historically (58% 

between 1961-1969, Dechtiar 1972a; 63% between 1968-1969, Chen and Power 1972; 90% in 1969, Nepszy et al. 
909

1978; 36-78% between 1976-1977, Nsembukya-Katuramu et al. 1981). Additional prevalences of this parasite 

within Lake Erie fall within this range (55% prevalence with ≥ 50 parasites/host between 1970-1975, Dechtiar and 

Nepszy 1988; 88% in the western and west central basins in 1971, Nepszy and Dechtiar 1972). Glugea hertwigi

poses the largest threat (e.g., high infection rates and mortalities) to Lake Erie rainbow smelt populations as 

compared to any other microsporidian (Muzzall and Whelan 2012).

In Lake Ontario, G. hertwigi has been isolated at 5% prevalence (between 1968-1969; Chen and Power 1972) and 

23% prevalence with heavy infections (from 1961-1971; Dechtiar and Christie 1988). Another occurrence was 

recorded in Port Ontario, NY; however, prevalence and intensity were unknown (Ehlinger 1966).

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

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

BENEFICIAL EFFECT

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

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
910

Not significantly 0 √

Unknown U

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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

As rainbow smelt preys heavily upon bloater (Coregonus hoyi), alewife (Alosa pseudoharegus), slimy sculpin 

(Cottus cognatus), emerald shiner (Notropis atherinoides), burbot (Lota lota), and opossum shrimp (Mysis relicta) 

(Brandt and Madon 1986, Creaser 1925, O’ Gorman 1974, Stedman and Argyle 1985, Van Oosten 1940), its diet is 

believed to affect prey population numbers and can be an important component to the total mortality of yearlings 

(Creaser 1925, O’ Gorman 1974). Furthermore, commercially valuable native and non-native salmonids rely on 

several of these prey species (e.g., bloater, alewife, emerald shiner). Die-offs of rainbow smelt as a result of G. 

hertwigi may increase prey fish populations, thus increasing feeding opportunities and improving the health and 

value of the salmonid fisheries. However, such effects have not been realized in the Great Lakes.

Additional potential food web effects include those on lake trout (Salvelinus namaycush). Juvenile lake trout tend to 

eat slimy sculpin, while adults consume rainbow smelt (Brandt and Madon 1986). Direct competition for slimy 

sculpin between juvenile lake trout and rainbow smelt has been observed (Brandt and Madon 1986). Lake trout may 

therefore be a keystone predator in the relationship between rainbow smelt and slimy sculpin (Brandt and Madon 

1986). Mortalities in rainbow smelt by G. hertwigi could decrease competition and stress in juvenile lake trout and 

could have significant beneficial effects on the Great Lakes food web.

Furthermore, rainbow smelt compete with lake herring (Coregonus artedii) and yellow perch (Perca flavescens) and 

may be partially responsible for the decline of Great Lakes whitefish (Coregonus spp.) (Becker 1983, Christie 1974, 

Hrabik et al. 1998, Todd 1986). Increased G. hertwigi infections and die-offs of rainbow smelt could lead to a 
911

decrease in competition and stress on lake herring and yellow perch and may increase the commercially valuable 

whitefish population.

Lastly, rainbow smelt contributed to the extinction of blue pike (Sander vitreus glaucus), a species prevalent in the 

Great Lakes until the 1980s. Rainbow smelt have also affected imperiled species outside the Great Lakes (EPA 

2008). Because of competition between rainbow smelt and native species, and O. mordax diet, other imperiled 

species in the Great Lakes could experience similar effects.

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: Heterosporis sp.

Common Name: Microsporidian

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

This particular species of Heterosporis has been isolated from several native Great Lakes species including walleye

(Sander vitreus), northern pike (Esox lucius), burbot (Lota lota), mottled sculpin (Cottus bairdi), slimy sculpin (C. 

cognatus), pumpkinseed (Lepomis gibbosus), and yellow perch (Perca flavensis). Yellow perch is the only species in 

which impacts have been realized (GLFHC 2012, IDNR 2005, Sutherland 2002, Sutherland et al. 2004). Prevalence 

of this parasite in Great Lakes yellow perch can range between 5% and 30%, with the majority of infections at 20% 

(Sutherland 2002). However, because of the wide range of Great Lakes native species susceptible to both infections 

(see Socio-Economic Impacts) this species is assessed as having a high environmental impact in this region.

Laboratory-based infections of Heterosporis sp. have been observed in Great Lakes native species including channel 

catfish (Ictalurus punctatus), bluegill (Lepomis macrochirus), and white sucker (Catostomus commersonii); the 

latter two species are less susceptible and experience much less muscle damage than the catfish (GLFHC 2012, 

IDNR 2005, Sutherland 2002, Sutherland et al. 2004). 

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., critical reduction, extinction, behavioral 

changes) 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

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)

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
913

Unknown U

Declines to the Great Lakes yellow perch stocks are believed to stress predator-prey relationships. There is no 

evidence to show this parasite causes fish mortality directly, but the destruction of muscle in infected fish increases 

susceptibility to predation (Goodwin 2008, Sutherland 2002).

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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
914

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Lake Ontario commercial fisheries are concerned about the economic impacts of Heterosporis sp. as infected fish 

suffer a significant loss of muscle tissue and are not marketable (i.e. must be discarded) (Sutherland 2002). 

Sutherland (2002) has also expressed concern that the presence of Heterosporis sp. in Lake Michigan may 

significantly impede the recovery of depressed yellow perch stocks, which have experienced population declines in 

Lake Michigan over the past decade. Economic impacts to the yellow perch fisheries could be realized if this 

parasite becomes established there.

Laboratory-based infections of Heterosporis sp. have been observed in commercially valuable Great Lakes native 

species including brook trout (Salvelinus fontinalis), lake trout (S. namaycush), fathead minnow (Pimephales 

promelas), and largemouth bass (Micropterus salmoides), and valuable non-native species including Coho salmon

(Oncorhynchus kisutch), rainbow trout (Oncorhynchus mykiss), and brown trout (Salmo trutta). The trout and 

minnow species are highly susceptible to infection, while the bass and salmon are marginally susceptible and 
915

experience much less muscle damage if infected at all (Sutherland 2002, Sutherland et al. 2004). Economic impacts 

to wild and cultured populations could be realized if natural infections are observed.

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

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

BENEFICIAL EFFECT

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

While there have been no field observation of biological control of nonnative species in the Great Lakes, common 

carp (Cyprinus carpio) and goldfish (Carassius auratus) appear to be highly susceptible to infection by Heterosporis 

sp. based on laboratory experiments (Sutherland 2002, Sutherland et al. 2004).

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

Is it recreationally valuable (e.g., for sport or leisurely fishing, as a pet, or for any other personal activity)?
916

Yes, it is commonly employed recreationally and has some perceived value for local communities and/or 

tourism

6

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
917

Scientific Name: Ichthyocotylurus pileatus

Common Name: A digenean fluke

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

In the Great Lakes, larval or immature I. pileatus have been detected in yellow perch (P. flavescens) at 37.7% 

prevalence (582 fish examined) with light (1-9 parasites/host) to moderate (10-49 parasites/host) infections 

(Dechtiar and Lawrie 1988, Dechtiar and Nepszy 1988, Muzzall and Whelan 2011); walleye (S. vitreus) at 47% 

prevalence (15 fish examined) with moderate infections (Dechtiar and Lawrie 1988); and trout-perch (P. 

omiscomaycus) (Bangham and Hunter 1939) at 54% prevalence (39 fish examined) with light infections (Dechtiar 

and Lawrie 1988, Dechtiar and Nepszy 1988). The larval form of I. pileatus is also found in piscivorous birds of 

Lake Superior and the Lake St. Clair System (Muzzall and Whelan 2011). 

While not documented for this species in the Great Lakes, adult digenean parasites tend not to severely impact their 

definitive host; infection of first and second hosts may result in castration (due to invasion of host gonads) and 

decreased fitness (due to diversion of host energy to parasite nutrition), respectively (Bartoli and Boudouresque 

2007). Ichthyocotylurus pileatus has the potential to be pathogenic to fish, particularly young individuals, when 

intensities of larvae/immature parasites are high (Muzzall and Whelan 2011).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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 √
918

Unknown U

Digenean flukes can cause pathological effects and mortality in juvenile and adult fishes (BychovaskayaPavlovskaya and Petrushevski 1963, Dukes 1975). Because of altered behavior, infected fish may be more 

susceptible to predation (Lafferty and Morris 1996). However, cascading food web effects have not been reported as 

a result of I. pileatus infection in the Great Lakes.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 6

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0
919

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

Recreationally valuable Great Lakes species susceptible to I. pileatus infections include yellow perch, walleye, and 

trout-perch; however, impacts to this sector have not been realized.
920

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

BENEFICIAL EFFECT

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

Non-native Great Lakes species found harboring larval or immature I. pileatus include Eurasian ruffe

(Gymnocephalus cernuaus) (Pronin et al. 1998) and round goby (Neogobius melanostomus) (Pronin et al. 1997b).

Ichthyocotylurus pileatus is unlikely to have significant effects in terms of regulating the round goby population in 

the Great Lakes (Pronin et al. 1997b). It is possible, however, that its presence in combination with that of other 

more prevalent parasites in Eurasian ruffe increases this species’ susceptibility to the negative effects of anoxia 

(Pronin et al. 1997a).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U
921

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

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

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, 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
922

Scientific Name: Myxobolus cerebralis

Common Name: Myxosporean parasite, salmonid whirling disease

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

Multiple salmonids are susceptible to infection by M. cerebralis, but the degree of susceptibility as well as symptom 

expression varies among species. Great Lakes native salmonid species susceptible to the pathogen include Atlantic 

salmon (Salmo salar), brook trout (S. fontinalis), cutthroat trout (Oncorhynchus clarki), and bull trout (Salvelinus 

confluentus). In contrast, lake trout (S. namaycush) is not susceptible to infection (Bartholomew et al. 2003, Blazer 

et al. 2004, Gilbert and Granath 2003, Krueger et al. 2006, Sollid et al. 2003).

Historically, the realized environmental impacts of whirling disease on native Great Lakes aquacultured and wild 

species have been low (GLFHC 2006, GLFHC 2012). However, while M. cerebralis has not been detected in the 

Great Lakes region of Canada, the Canadian Food Inspection Agency (2012) lists it as a reportable disease. Such 

recognition warrants assessment of this species as having a high environmental effect for the region.

Myxobolus cerebralis myxospores infect the cosmopolitan oligochaete worm Tubifex tubifex prior to development 

into a fish-infecting form (Elwell et al. 2009). Infection of T. tubifex can negatively affect the host’s growth, 

reproduction, and survival (DuBey et al. 2005, El-Matbouli and Hoffmann 1998, Gilbert and Granath 2003, 

Hedrick and El-Matbouli 2002, Stevens et al. 2001). However, such an impact on Great Lakes T. tubifex

populations has not been reported (possibly due to a lack of research in this area).

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., critical reduction, extinction, behavioral 

changes) 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

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)

6

Yes, and it has resulted in some noticeable stress to or decline of at least one native species 

population

AND/OR

1
923

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

Whirling disease can result in whirling behavior or tail-chasing; damage to the central nervous system and organs 

of equilibrium; lesions in the skull, gills, and vertebrae; and sometimes mortality (Crawford 2001, Gilbert and 

Granath 2003, Krueger et al. 2006, Mills et al. 1993). This causes stress and leads to reduction in fish populations 

by making it difficult for individuals to effectively escape predators or feed (WDI 2011). However, cascading food 

web effects as a result of M. cerebralis infection have not been reported in the Great Lakes.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Whirling disease can alter fish community composition by replacing susceptible species with more resistant species 

such as brown trout (Elwell et al. 2009). This has been observed in several Montana drainages, where rainbow 

trout populations decreased while brown trout increased (Baldwin et al. 1998).

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 7

Total Unknowns (U) 0
924

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Whirling disease has no known human health effects (WDI 2006).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

The consequences of identifying this parasite in a hatchery can be severe, including facility closure, expensive 

renovations, and destruction of infected stock, leading to high economic costs. At a national level, trout fisheries—
925

including the $325 million U.S. hatchery-raised rainbow trout industry (economic benefit reported 2004; USFWS 

2006) that generated annual sales of more than $80 million from 2005-2007 (USDA 2008)—are especially at risk. 

In 2007, 86 percent of the United States’ 34.3 million trout intended for sale were lost due to a variety of diseases 

(USDA 2008). This percentage of state and federally raised hatchery trout intended for market but lost to disease 

rose to 90 percent in 2009 (USDA 2010). Furthermore, economic impacts realized at a regional level outside the 

Great Lakes as a result of M. cerebralis infection include a nearly 29 percent reduction in the total value of trout 

sales and the closure of six private hatcheries in Utah in 2005 (Stromberg 2006). 

In 2006, low level infections of M. cerebralis spores were detected in rainbow trout reared in a Pennsylvania state 

hatchery. Whirling disease spores were also isolated from Pennsylvania’s Lake Erie steelhead in 1989, 1991, and 

1997 (GLFHC 2006). However, wild trout populations of the mid-Atlantic region have not experienced observable 

declines, despite the presence of M. cerebralis and susceptible species (Hulbert 2005, Kaeser et al. 2006, Kaeser 

and Sharpe 2006).

In spring 2011, Michigan authorities conducted pre-stocking testing for M. cerebralis on nine representative lots of 

hatchery fish (60 fish per lot, including brown trout, rainbow trout, chinook salmon, Atlantic salmon, coho salmon, 

lake trout, brook trout, splake, and lake herring), and all were found negative for the parasite (GLFHC 2012). 

However, when conducting the same tests on wild-caught fish from hatchery water sources, molecular evidence of 

M. cerebralis was detected in one sample (containing pooled tissue of a total of 60 brown and rainbow trout from 

three sources— Slagle Creek, Harrietta Effluent Pond, and Brundage Spring Pond (GLFHC 2012). 

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 multibillion dollar per year Great Lakes sport fishery and the multimillion dollar per year inland trout fishing 

industry are at risk if whirling disease becomes established in Wisconsin and Minnesota and/or continues to infect 

hatcheries and wild populations in Michigan (Frank 2002).

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

BENEFICIAL EFFECT
926

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

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
927

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
928

Scientific Name: Neascus brevicaudatus

Common Name: A digenean fluke

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

The only occurrence of N. brevicaudatus in the Great Lakes has been from the introduced Eurasian ruffe (G. cernua) 

at 5% prevalence with very light (<1 parasite/host) infections (Pronin et al. 1998). Due to the slow rate of 

population growth and expansion of N. brevicaudatus, its impacts in the Great Lakes are believed to be negligible 

(Pronin et al. 1998). Larvae of this species mature in piscivorous birds (Muzzall and Whelan 2011); however, the 

effects of such infections have not been studied.

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
929

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
930

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
931

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

Neascus brevicaudatus is believed to be unlikely to help regulate populations of the introduced Eurasian ruffe (U.S. 

Department of the Interior 1993).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 √
932

Unknown U

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, 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
933

Scientific Name: Viral hemorrhagic septocemia Virus (Family Novirhabdoviridae, Order 

Mononegavirales) Genotype IV sublineage b

Common Name: Viral Hemorrhagic Septicemia (VHSV-IVb)

Environmental: High

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

VHS is listed as a World Organization for Animal Health (OIE) reportable disease for aquatic animals (OIE 2012).

VHS is believed to have caused large die-offs of freshwater drum (Aplodinotus grunniens) in eastern Lake Ontario 

and muskellunge (Esox masquinongy) in Lake St. Clair in 2005 (Wren and Lee 2006). In the spring and summer of 

2006, VHS was implicated as a cause of large die-offs of muskellunge in the Thousands Islands area of the St. 

Lawrence River (Wren and Lee 2006) and die-offs of muskellunge, northern pike (Esox lucius), gizzard shad

(Dorosoma cepedianum), smallmouth bass (Micropterus dolomieui), walleye (Sander vitreus), and yellow perch 

(Perca flavescens) in Lakes St. Clair, Erie, and Ontario (USDA and APHIS 2006). Die-offs of walleye in Conesus 

Lake, NY and lake whitefish (Coregonus clupeaformis) and walleye in Thunder Bay in the fall of 2006 were also 

believed to have been caused by VHS (Whelan 2009). In May 2007, low to moderate fish kills of freshwater drum 

were experienced in the Wisconsin lakes Butte des Mortes and Winnebago. Later that year, there was a die-off of 

sunfish (Family Centrarchidae) in the Seneca-Cayuga Canal, New York (Focus on Fish Health 2010). VHS has also 

been implicated as the cause of lake whitefish and walleye die-offs in Lake Huron (MSG 2012).

Other Great Lakes native species that are susceptible to VHS and have experienced mild to moderate die-offs 

include black crappie (Pomoxis nigromaculatus) and bluegill (Lepomis macrochirus) in Budd Lake, MI and Lake St. 

Clair, white bass (Morone chrysops) in Lake Erie, and rock bass (Ambloplites rupestris) in Skaneateles Lake, NY 

(Whelan 2009). Die-offs of largemouth bass (Micropterus salmoides) have also been observed (Kim and Faisal 

2010a, Kim and Faisal 2010b).

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., critical reduction, extinction, behavioral 

changes) 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

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 

6
934

native species 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 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

VHS has the potential to infect a wide range of fish species (Kim and Faisal 2010a) with clinical signs such as body 

twisting and erratic swimming (CFSPH 2003). Because of this, infected fish may be more susceptible to predation 

(Lafferty and Morris 1996), which could result in indirect effects on the food web and ecosystem. Die-offs of apex 

predators such as muskellunge and northern pike may have severe impacts on the Great Lakes food web.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 7

Total Unknowns (U) 0
935

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Humans are not susceptible to VHS and there is no evidence that the virus can be transferred to humans by 

consuming infected fish (PFBC 2011).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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 √

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U
936

Increased regulations have limited the scope of operations for those in the bait/live fish industry and have cost a 

substantial amount of additional time and money to fulfill testing and certification requirements. 

Despite the wide host range of the virus, effects on commercial and recreational fisheries related to die-offs have 

been relatively mild in the Great Lakes (Focus on Fish Health 2010).

As of June 2011, there has not been a recorded outbreak of VHS within a hatchery system in the United States. 

Under APHIS policy, total destruction and disinfection of a hatchery is likely if VHS is isolated, leading to 

significant economic loss (PFBC 2011).

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

While many commercially and recreationally-valuable salmonids— including chinook salmon (Oncorhynchus 

tshawytscha), coho salmon (O. kisutch), and rainbow trout (O. mykiss)—are susceptible to the Great Lakes strain 

of the virus (IVb), recent studies indicate they experience VHS-induced symptoms and mortality less often than other 

susceptible species (Al-Hussinee et al. 2010, Kim and Faisal 2010a). Recreationally-valuable species that have been 

particularly affected experimentally include muskellunge (E. masquinongy) and largemouth bass (M. salmoides), 

both of which have experienced very high mortality rates (Kim and Faisal 2010a, Kim and Faisal 2010b).

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) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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
937

VHS has caused die-offs of non-native species in the Great Lakes, including round goby (Neogobius melanostomus) 

(Wren and Lee 2006). In 2008, the first recorded die-off of round goby occurred in Lake Michigan, although 

observed signs of the virus had been documented in Lake Michigan in 2007 (Focus on Fish Health 2010). Die-offs 

of common carp (Cyprinus carpio) have been observed in Lake Ontario (Whelan 2009).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
938

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1
939

Scientific Name: Piscirickettsia cf. salmonis

Common Name: Muskie pox

Environmental: Moderate

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Piscirickettsia cf. salmonis infections have been limited in the Great Lakes to muskellunge (E. masquinongy) and 

yellow perch (Perca flavescens) from Lake St. Clair (Hartig 2006, Thomas and Faisal 2009, MDNR 2004). The 

bacterium was detected in all of the fish (n=26) sampled from Lake St. Clair during a large muskellunge die-off in 

2003. No subsequent mortalities were observed in St. Clair until 2006 (Hartig 2006, Thomas and Faisal 2009).

Piscirickettsia cf. salmonis infection rates in Lake St. Clair muskie have been found to be over 80 percent in fish 

larger than 1,000 mm and or individuals older than 8 yrs (2004-2007; Thomas and Faisal 2009). Piscirickettsia 

cf. salmonis has also been isolated from yellow perch (P. flavescens) from St. Clair with infection rates as high as 

57 percent. Analysis of the two isolates from muskellunge and yellow perch indicate both are identical (Thomas and 

Faisal 2009). However, surveys of P.cf. salmonis infected waters in the Great Lakes do not indicate substantial 

negative impacts on native fish populations (MDNR 2004, WDNR 2012).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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
940

Piscirickettsia cf. salmonis infections can result in anemia, kidney necrosis, an enlarged spleen, hemorrhaging, 

nodules or crater-form lesions in the liver, skin lesions, anorexia, and lethargy (Fryer and Hedrick 2003, Mauel and 

Miller 2002, Rise et al. 2004). Because of altered behavior, infected fish are more susceptible to predation (Lafferty 

and Morris 1996), which could result in indirect effects on the food web and ecosystem. Die-offs of apex predators 

such as muskellunge is likely to impact the Great Lakes food web, although such effects have not yet been reported 

as a result of P. salmonis infection.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 2

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
941

1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

Piscirickettsia cf. salmonis infections in cultured Atlantic salmon (Salmo solar) from the Pacific and Atlantic coasts 

of Canada have led to population mortality levels of 0.6-15% (Evelyn 1992, Olsen et al. 1993, Rodger and Drinan 

1993). However, no such infections have been realized in Great Lakes Atlantic salmon. Atlantic salmon are 

considered less susceptible to infection and mortality; in contrast, coho salmon (Oncorhynchus kisutch), rainbow 

trout (O. mykiss), and Chinook salmon (O. tschwaytscha) are more susceptible (Birkbeck et al. 2004, Fryer and 

Hedrick 2003, Mauel and Fryer 2001, Mauel and Miller 2002, Rise et al. 2004). Infections in non-native salmonids 

have not been realized in the Great Lakes.

Chilean aquaculture facilities have experienced mortality due to P.cf. salmonis in 30-90% of reared coho salmon 

(Bravo and Campos 1989). As a result, this industry has shifted their cultures to Atlantic salmon (Reid et al. 2004). 

If similar effects are realized in the Great Lakes, significant economic impacts could be realized.
942

While impacts to the sport fishing industry by P.cf. salmonis have not yet been realized, such effects could be 

significant. For example, recreational fishing on Lake St. Clair can generate $23 million annually (Thomas and 

Faisal 2009).

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

Surveys of P. cf. salmonis infected waters in the Great Lakes do not indicate substantial negative impacts on native 

fish populations (MDNR 2004, WDNR 2012).

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

BENEFICIAL EFFECT

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

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
943

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
944

Scientific Name: Ranavirus sp.

Common Name: Largemouth bass virus (LMBV)

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

As Ranavirus sp. has resulted in the reduction of native largemouth bass (Micropterus salmoides) populations, this 

virus is assessed as having a high environmental impact in the Great Lakes. Further research is needed to determine 

if a developing immunity similar to the populations seen in Florida is realized in Great Lakes largemouth bass 

populations.

In Michigan, LMBV mortality events typically have involved 100-500 fish or 10 percent of the population per lake 

(Grizzle and Brunner 2003, Whelan 2004). However, Ranavirus sp. has also been implicated in several more 

significant largemouth bass die-offs within the Great Lakes basin, including in Lake George, Indiana—where LMBV 

was detected in 90% of fish sampled (Grizzle and Brunner 2003, Whelan 2004)—and in a small Steuben County, 

Indiana lake (2011; Sarvay 2012). The latter resulted in the death of 50 percent of the lake’s largemouth bass 

population (Sarvay 2012).

Prevalence of Ranavirus sp. in the state of Michigan was determined using 2000-2003 virus survey data. When 

detected (15 of 30 surveyed lakes), prevalence at the other lakes ranged from 6.3% (Lake Orion) to 100% (Lake St. 

Clair, Sanford Lake, Woodland Lake), with detection of the LMBV in close to or more than half of the largemouth 

bass sampled from many of these lakes (Whelan 2004). However, levels of fish infection varied among sites and 

between sample years. For example, the virus was detected in Lake Orion at 6.3% prevalence in 2002 and then at 

48% in 2003. In Woodland Lake, Ranavirus sp. was detected at 100% prevalence in 2002 and at 60% in 2003. The 

virus was also detected in Lake George at 90% prevalence in 2000 and 0% prevalence in 2002 (Whelan 2004). This 

may suggest the virus enters a water body, infects the population until a peak infection rate is observed, and then 

prevalence decreases. 

Other Great Lakes native species susceptible to infection by Ranavirus sp. include smallmouth bass (M. dolomieui), 

bluegill (Lepomis macrochirus), crappie (Pomoxis spp.), and chain pickerel (Esox niger). However, mortality events 

attributed to LMBV are rare in these species (Goldberg 2002, Grizzle and Brunner 2003, Grizzle et al. 2003, 

Whelan 2004, Woodland et al. 2002).

Ranavirus sp. was implicated in the die-off of over 1,000 and 3,000 largemouth bass in South Carolina and a 

northern Mississippi drainage reservoir, respectively (Bister et al. 2006, Hanson et al. 2001, Plumb et al. 1996). In 

2010, LMBV was detected in 40 percent of the largemouth bass in Kerr Reservoir and Buggs Lake, Virginia. Small 

die-offs also occurred in Briery Creek Lake and Sandy River Reservoir, Virginia. However, no significant impacts to 

the fisheries were realized (VDNR 2011). Die-offs have also occurred in Alabama, Georgia, Louisiana, Mississippi, 

and Texas (Bister et al. 2006). Moreover, since 1995, over 25 fish kills throughout the southeast and Midwestern 

U.S. have been linked to LMBV (FFWCC 2012).

Initial exposure to LMBV elicits antibody production, resulting in less severe disease manifestation in subsequent 

exposures (e.g., FFWCC 2012, Goldberg 2002, Grizzle and Brunner 2003, Grizzle et al. 2003, Hodge 2004, Whelan 
945

2004, Woodland et al. 2002). For example, in Florida, largemouth bass die-offs associated with LMBV have 

declined since first detection and no known die-offs have been observed since 2010 (FFWCC 2012).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

Symptoms of LMBV can include lethargy, decreased responsiveness, swimming at the surface and or in circles, and 

difficulty remaining upright (Beck et al. 2006, Goldberg 2002, Grizzle and Brunner 2003, Zilberg et al. 2000). 

Because of this altered behavior, infected fish may be more susceptible to predation (Lafferty and Morris 1996). 

However, cascading food web effects have not been reported as a result of LMBV infection in the Great Lakes.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?
946

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Largemouth bass virus poses no threat to human health (MAF 2008).

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

1
947

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Largemouth bass sport fishing organizations (e.g., Bass Anglers Sportfishing Society/BASS) have increased 

spending and time to evaluate and understand the impacts of LMBV on trophy-sized bass fisheries (Grizzle and 

Brunner 2003, Neal et al. 2009, Terre et al. 2008, Whelan 2004).

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

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

BENEFICIAL EFFECT

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
948

Not significantly 0 √

Unknown U

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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

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, 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
949

1 0

0 ≥2

Unknown 1 ≥1
950

Scientific Name: Renibacterium salmoninarum

Common Name: Bacterial kidney disease (BKD)

Environmental: High

Socio-Economic: High

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

Great Lakes native salmonid species that have tested positive for the bacterium include Atlantic salmon (Salmo 

salar), lake trout (Salvelinus namaycush), brook trout (S. fontinalis), and splake (S. fontinalis x S. namaycush) 

(GLFHC 2006, GLFHC 2012, Hay 2003, Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997). Lake trout and 

brook trout are considered less susceptible to R. salmoninarum infection and may not experience mortality upon 

contracting BKD; in contrast, Atlantic salmon are more susceptible and prone to mortality (Hay 2003, Jonas et al. 

2002, Nuhfer et al. 2005, Starliper et al. 1997).

Other Great Lakes native species found harboring R. salmoninarum include lake whitefish (Coregonus 

clupeaformis), bloater (C. hoyi), lake herring (C. artedi), mottled scuplin (Cottus bairdi), white sucker (Catostomus 

commersonii), muskellunge (Esox masquinongy), channel catfish (Ictalurus punctatus), lake sturgeon (Acipenser 

fulvescens), and walleye (Sander vitreus) (COSEWIC 2005, GLFHC 2006, GLFHC 2012, Hay 2003, Jonas et al. 

2002, Nuhfer et al. 2005, Starliper et al. 1997). Four of the Great Lakes native species (splake, muskie, channel 

catfish, and lake sturgeon) represent new detections since 2005. Lake whitefish and bloater are believed to be less 

susceptible to R. salmoninarum infection and may not experience mortality upon contracting BKD (Hay 2003, Jonas 

et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997). However, strains of the bacterium isolated from Lake 

Michigan have been found to be more virulent than those from the Pacific Northwest (Austin and Austin 1987, 

Grayson et al. 1999, Jonas et al. 2002, Starliper et al. 1997, Thomas et al. 1999) and in some cases have resulted in 

higher than anticipated levels of infection (e.g., Nalepa et al. 2005).

While R. salmoninarum affects multiple Great Lakes native species, as of 2006, prevalence and mortalities in 

infected fish had been relatively low (GLFHC 2006). However, more recent data from 2011 indicates that this 

bacterium has become more widely distributed with varying prevalence throughout Michigan state hatcheries and 

wild populations. The bacterium was detected in brook trout at 1.7% to 54% prevalence; Atlantic salmon 1.7% to 

50%; muskellunge, lake sturgeon, and channel catfish at 1.7% to 10%; and lake trout, splake, and lake herring at 

1.7%-5% prevalence (GLFHC 2012). That same year, R. salmoninarum was detected at low prevalence in 

Minnesota hatcheries and for the first time in lake trout from Mountain Lake, MN. The Minnesota Department of 

Natural Resources is considering whether or not to continue using that lake as a brood stock source (GLFHC 

2012). 

Renibacterium salmoninarum is considered to be endemic in Ontario and is found in OMNR fish culture facilities at 

low levels (GLFHC 2012).

Does it out-compete native species for available resources (e.g., habitat, food, nutrients, light)?
951

Yes, and it has resulted in significant adverse effects (e.g., critical reduction, extinction, behavioral 

changes) 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

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)

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

Symptoms of BKD include abdominal fluid build-up and swelling, pseudomembranes and hemorrhaging on viscera, 

kidney and gill necrosis, intestinal hemorrhaging, ulcers or abscesses in muscles, protruding eyeballs, anemia, 

blood blisters, and lesions of the eyes, liver, spleen, and heart (Austin and Austin 1987, Holey et al. 1998). Because 

of this, infected fish may be more susceptible to predation (Lafferty and Morris 1996). However, cascading food web 

effects as a result of BKD infection in the Great Lakes have not been reported.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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 1
952

effects have been mild

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

Environmental 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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm any markets or economic sectors (e.g., commercial fisheries, aquaculture, agriculture)?
953

Yes, it has caused significant damage to one or more markets or economic sectors 6 √

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

Lake whitefish (C. clupeaformis) collected from Lake Michigan and Lake Huron between 2003 and 2006 tested 

positive for R. salmoninarum at 62.31% prevalence. Lake whitefish have a high commercial value in the Great 

Lakes (Nalepa et al. 2005), and if as a result of BKD infection, populations were to fluctuate significantly, there 

could be serious economic effects.

Great Lakes non-native species that have tested positive for R. salmoninarum include Chinook salmon

(Oncorhynchus tshawytscha) (Holey et al. 1998), coho salmon (O. kisutch), rainbow trout (O. mykiss), and sea 

lamprey (Petromyzon marinus) (Eissa et al. 2006, Jonas et al. 2002). Rainbow trout (O. mykiss) is less susceptible 

to BKD infection and may not experience mortality upon contracting the disease, whereas coho salmon (O. kisutch) 

and Chinook salmon (O. tshawytscha) are more susceptible to infection and more prone to mortality (Hay 2003, 

Jonas et al. 2002, Nuhfer et al. 2005, Starliper et al. 1997).

Prevalence rates of R. salmoninarum were up to 100% in some parts of the Lake Michigan drainage around 1986. 

This outbreak of BKD caused heavy mortality in Chinook salmon in 1988 and persisted in the population until 1992. 

That year, boat fisheries observed at least a 40% decline in Chinook salmon catch per unit effort levels. By 1993, 

catch per unit effort was 15% of the peak observed in 1986 (Holey et al. 1998). In 1986, the Strawberry Creek 

spawning weirs in Wisconsin documented no presence of R. salmoninarum. In 1988, the bacterium was isolated in 

67% of the returning Chinook salmon and then persisted at moderate levels through 1992 (Holey et al. 1998). The 

1980s’ mortality events are believed to have also been influenced by increased vulnerability due to food shortages, 

particularly alewives (Alosa pseudoharengus), high Chinook salmon density, and high parasite loads (Holey et al.

1998). While significant for the fisheries at that time, given the magnitude of the stocks present in Lake Michigan, it 

is improbable that the Chinook salmon die-offs observed in the late 1980s and early 1990s caused a residual 

demographic bottleneck in those populations (Weeder et al. 2005).

As of 2006, the overall prevalence of R. salmoninarum in non-native Great Lakes species was thought to be low and 

declining over time (GLFHC 2006, Jonas et al. 2002). However in 2011, R. salmoninarum was widely distributed 

with varying prevalence throughout Michigan state hatcheries and wild populations. The bacterium was detected in 

brown trout (Salmo trutta) at 1.7% to 54% prevalence, rainbow trout at 1.7% to 40%, coho salmon at 1.7% to 10%, 

and Chinook salmon at 1.7% to 5% prevalence (GFLHC 2012). Renibacterium salmoninarum was detected in 11 of 

12 production lots of rainbow trout and coho salmon from 4 of 5 Indiana state hatcheries with prevalence ranging 

from 1.67% to 26.67%, with six cases exceeding 10% (GLFHC 2012).

Bloater (C. hoyi) is a staple of Great Lakes native and non-native salmonid diets. Reductions in salmonid 

populations and economic effects to the Great Lakes fishing industry could be realized if bloater populations decline 

(Wyns 2002).

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

Prevalence rates of R. salmoninarum were up to 100% in some parts of the Lake Michigan drainage around 1986. 

This outbreak of BKD caused heavy mortality in Chinook salmon in 1988 and persisted in the population until 1992. 

That year, boat fisheries observed at least a 40% decline in Chinook salmon catch per unit effort levels. By 1993, 

catch per unit effort was 15% of the peak observed in 1986 (Holey et al. 1998). In 1986, the Strawberry Creek 

spawning weirs in Wisconsin documented no presence of R. salmoninarum. In 1988, the bacterium was isolated in 

67% of the returning Chinook salmon and then persisted at moderate levels through 1992 (Holey et al. 1998). The 

1980s’ mortality events are believed to have also been influenced by increased vulnerability due to food shortages, 

particularly alewives (Alosa pseudoharengus), high Chinook salmon density, and high parasite loads (Holey et al. 

1998).
954

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

BENEFICIAL EFFECT

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 addition to commercially valuable non-native Great Lakes species (see Socio-economic Impacts), sea lamprey

(Petromyzon marinus) has tested positive for BKD (Eissa et al. 2006). However, infection is not likely to control sea 

lamprey populations.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
955

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

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

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, 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
956

Scientific Name: Rhabdovirus carpio

Common Name: Spring viraemia of carp (SVCv)

Environmental: High

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0

Unknown U

SVC is listed as a World Organization for Animal Health (OIE) reportable disease for aquatic animals (OIE 2012) 

and is also listed as a reportable disease in Canada (CFIA 2012). As such, it is automatically assessed as having a 

high environmental impact in the Great Lakes region. 

Great Lakes native species susceptible to infection by R. carpio include emerald shiner (Notropis atherinoides), 

largemouth bass (Micropterus salmoides), and bluegill (Lepomis macrochirus) (Cipriano 2011). Experimental 

infections have been reported in northern pike (Esox lucius), pumpkinseed (Lepomis gibbosus), golden shiner

(Notemigonus crysoleucas), and perch (Family Percidae) (CFSPH 2007).

Until 2011, when two fish tested positive for SVCv following a die-off of 200-300 carp in Minnehaha Creek, 

Minnesota (GLFHC 2012), SVCv had not been implicated in die-offs of native or non-native species in the Great 

Lakes, nor had there been reports of the virus in commercial aquaculture since 2003 (Cipriano 2011). It should be 

noted that Chryseobacterium and Aeromonas hydrophila group 2 were isolated from the kidneys and Acinetobacter 

baumannii-calcoaceticus was isolated from the eyes of the fish, as well (GLFHC 2012).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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
957

Not significantly 0 √

Unknown U

Symptoms of SVC include exophthalmia, darkened coloration, anemia, and hemorrhage in the gills, skin, and eyes 

(Fijan 1999, Fijan et al. 1971). Because of this, infected fish may be more susceptible to predation (Lafferty and 

Morris 1996). However, cascading food web effects have not been reported as a result of SVC infection in the Great 

Lakes.

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 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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Environmental Impact Total 6

Total Unknowns (U) 0

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1 Low
958

1 0

0 ≥2

Unknown 1 ≥1

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1 √

Not significantly 0

Unknown U

SVCv has been reported from a koi production facility in North Carolina (Goodwin 2003) and a commercial fish 

pond in Missouri (Cipriano 2011), following fish mortality events.

It has also been responsible for mortality-related losses of aquacultured fish in Europe (Goodwin 2009).

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
959

Not significantly 0 √

Unknown U

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

BENEFICIAL EFFECT

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

Rhabdovirus carpio primarily infects common carp (Cyprinus carpio), koi carp (Cyprinus carpio koi), grass carp

(Ctenopharyngodon idella), silver carp (Hypophthalamicthys molitrix), bighead carp (H. nobilis), and goldfish

(Carassius auratus) (CFSPH 2007, OIE 2009). SVCv was implicated in the death of more than 1,500 carp in Cedar 

Lake, Wisconsin (Dikkeboom et al. 2004). However, the overall impact on the Great Lakes common carp population 

is minimal.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U
960

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

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

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, 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
961

Scientific Name: Scolex pleuronectis

Common Name: Cestode

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

According to Muzzall and Whelan (2011), Great Lakes detection of S. pleuronectis have been limited to infections of 

the introduced round goby (Neogobius melanostomus) at 13.5% prevalence with light infections (1-2 parasites/host) 

(Pronin et al. 1997). As such, it is unlikely to exert negative impacts on native fish species.

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 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
962

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

1
963

It has significantly affected human health in past invasions outside of the Great Lakes

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

In 1989, S. pleuronectis was detected in brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) in 

Chile (Torres et al. 1990). However, no such infections have been realized in the Great Lakes.

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

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
964

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

Scolex pleuronectis is believed to be unlikely to help regulate populations of the introduced round goby (Pronin et 

al. 1997).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
965

Not significantly 0 √

Unknown U

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, 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
966

Scientific Name: Sphaeromyxa sevastopoli

Common Name: Myxosporean parasite

Environmental: Low

Socio-Economic: Low

Beneficial: Low

Comments: The distribution of S. sevastopoli in the Great Lakes appears to be limited, with no observations reported 

since 1995. Without documented impacts, it appears to be relatively benign in this system.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Sphaeromyxa sevastopoli is not known to parasitize species native to the Great Lakes basin, although myxosporeans 

in general incorporate both a fish and an annelid host (Wolf and Markiw 1984).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
967

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
968

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
969

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

While a parasite of introduced gobies in the Great Lakes, it is unlikely that S. sevastopoli can regulate their 

populations (Pronin et al. 1997).

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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 √
970

Unknown U

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, 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
971

Scientific Name: Timoniella sp.

Common Name: A digenean fluke, trematode

Environmental: Low

Socio-Economic: Low

Beneficial: Low

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Timoniella sp. has only been isolated in the Great Lakes from the introduced Eurasian ruffe (G. cernua) (Pronin et 

al. 1997, 1998). As such, it is unlikely to exert negative impacts on native fish species. However, members of this 

trematode genus have been documented to parasitize additional fish species (e.g., Kvach and Skora 2006, Zander 

and Reimer 2002).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

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 which may be irreversible or has led to the 

decline or extinction of one or more native species

6
972

Yes, some genetic effects have been observed, but consequences have been limited to the individual 

level

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?

Yes, significant effects on human health have already been observed 6
973

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
974

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

Timoniella sp. infection of the introduced Eurasian ruffe in the Great Lakes has ranged from densities of 7-61 

parasites per ruffe, with up to 100% prevalence (Pronin et al. 1997, 1998). However, Timoniella sp. is believed to 

be unlikely to help regulate populations of the introduced Eurasian ruffe.

A relationship between resistance to anoxia in Eurasian ruffe and its parasite load has been observed, such that 

increased richness of parasites, including Timoniella sp., negatively affects the ruffe's ability to survive low-oxygen 

conditions (Pronin et al. 1997). Furthermore, species of Timoniella have been documented to occur in gobies 

outside the Great Lakes (e.g. Kvach and Skora 2006, Malek 2003). It is not known how the presence of these 

parasites might affect nonnative fish population dynamics and competitive interactions with native fishes in the 

Great Lakes.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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
975

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

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, 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
976

Scientific Name: Trypanosoma acerinae

Common Name: flagellate parasite

Environmental: Low

Socio-Economic: Low

Beneficial: Low

Comments: The distribution of T. acerinae in the Great Lakes appears to be limited, with no observations reported 

since 1992. Without documented impacts and its host specificity for Eurasian ruffe, it appears to be relatively benign 

in this system.

ENVIRONMENTAL IMPACT

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)

AND/OR

It has significantly affected similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Trypanosoma acerinae was found in 10% of the introduced Eurasian ruffe (Gymnocephalus cernua), its only known 

host, sampled from Pokegama Bay, Lake Superior in 1992 (Pronin et al. 1998). It is not known to parasitize any 

Great Lakes native species, although trypanosomes in general incorporate both a fish and a leech host (Laveran 

and Mesnil 1907).

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., critical reduction, extinction, behavioral 

changes) 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

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)

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

Has it affected any native populations genetically (e.g., through hybridization, selective pressure, introgression)?
977

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

AND/OR

It has genetically affected the same or similar species in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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 mild

AND/OR

It has significantly affected water quality in past invasions outside of the Great Lakes

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))?

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

AND/OR

It has significantly altered physical ecosystems in past invasions outside of the Great Lakes

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

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)?
978

Yes, significant effects on human health have already been observed 6

Yes, but negative consequences have not been widespread, long lasting, or severe 

AND/OR

It has significantly affected human health in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

AND/OR

It has a history of causing significant infrastructural damage in past invasions outside of the Great Lakes

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 

AND/OR 

It has a history of significantly affecting water quality in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

Does it harm 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

Yes, some damage to markets or sectors has been observed, but negative consequences have been small

AND/OR

It has a history of harming markets or economic sectors in past invasions outside of the Great Lakes

1

Not significantly 0 √

Unknown U

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

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
979

Scoring

Score # U Impact

>5 Any High

2-5 Any Moderate

0 0-1

Low 1 0

0 ≥2

Unknown 1 ≥1

BENEFICIAL EFFECT

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

While a parasite of the introduced Eurasian ruffe in the Great Lakes, there are no known reports of T. acerinae

impacting ruffe populations.

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

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

Yes, it is sometimes employed recreationally, but adds little value to local communities or tourism 1

Not significantly 0 √

Unknown U

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

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
980

Yes, but positive impact for humans or native species is considered negligible 1

Not significantly 0 √

Unknown U

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, 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
981

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