Idaho Aquatic Nuisance Species Plan 

A Supplement to Idaho’s Strategic Action Plan 

For Invasive Species 

Prepared for 

Governor C. L. “Butch” Otter 

And the 

Idaho Invasive Species Council 

By 

The Idaho Invasive Species Council 

Technical Committee 

2007 
2

Idaho Aquatic Nuisance Species Plan 

Executive Summary............................................................................................................ 3 

Acknowledgements......................................................................................................... 7 

List of Acronyms ................................................................................................................ 8 

Introduction - Managing Aquatic Nuisance Species in Idaho ............................................ 9 

Invasive Species in Idaho................................................................................................ 9 

The Aquatic Nuisance Species Plan for Idaho.............................................................. 10 

What is At Stake?.............................................................................................................. 14 

Facing the Enemy—What is out there and how might it arrive in Idaho? ....................... 17 

Types of ANS ............................................................................................................... 17 

The Known Threats................................................................................................... 20 

The Framework for Aquatic Nuisance Species Management in Idaho ............................ 23 

Federal Policies and Efforts.......................................................................................... 23 

Nonindigenous Aquatic Nuisance Prevention and Control Act and the National 

Aquatic Nuisance Species Task Force...................................................................... 23 

National Invasive Species Act .................................................................................. 23 

Invasive Species Executive Order ............................................................................ 24 

Individual Federal Agency Programs ....................................................................... 24 

Regional Organization and Efforts ............................................................................... 26 

The Western Regional Panel on Aquatic Nuisance Species..................................... 26 

Western Governors Association ............................................................................... 26 

Pacific States Marine Fisheries Commission/Bonneville Power Administration 

Aquatic Nuisance Species Program for the Columbia River Basin.......................... 27 

100th Meridian Initiative ........................................................................................... 27 

Current State Programs................................................................................................. 28 

Current Efforts and How We Can Be More Effective.................................................. 33 

1. Early Intervention – Prevention, Early Detection, & Rapid Response............. 33 

2. Containment, Control and Restoration ............................................................. 37 

3. Reaching Important Audiences through Education and Training..................... 40 

4. Broadening Knowledge through Research and Technology Transfer.............. 42 

5. Assuring Adequate Funding ............................................................................. 43 

6. Creating an Adequate, Effective Legal Structure ............................................. 44 

7. Coordination of efforts...................................................................................... 46 

Closing the Net on ANS—Idaho’s Plan ........................................................................... 47 

Glossary ............................................................................................................................ 56 

Sources.............................................................................................................................. 58 

Appendix A. Idaho’s ANS Technical Advisory Committee ...................................... 61 

Appendix B. Species and Categories ......................................................................... 62 

Appendix C. List of Known Nonindigenous Aquatic Species in Idaho................... 127 

Appendix D. Idaho’s Rapid Response Strategy ....................................................... 131 
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Idaho Aquatic Nuisance Species Plan 

Executive Summary 

The Plan and why it is Necessary 

In 2005, the Governor approved Idaho’s “Strategic Action Plan for Invasive Species”, 

prepared by the Idaho Invasive Species Council (IISC) as a statewide effort to limit the 

introduction and spread of invasive species. Invasive species are generally those plants 

and animals that are not native to an area, have the potential to spread uncontrollably, and 

when they do, cause significant economic or ecological harm. They include noxious 

weeds that invade all lands ranging from cultivated farms to vacant city blocks, as well as 

unwanted insects and some animals. Their economic impacts of these species nationwide 

in terms of the costs of treatment and prevention, in lost agricultural production and in 

restoring infested areas have been estimated in the billions of dollars. 

A special class of invasive species that deserve particular attention are the “aquatic 

nuisance species” (ANS). ANS are those plants and animals that are dependent upon 

aquatic and riparian ecosystems. Here, as is the case with all other invasive species, 

introductions and uncontrollable spreads wreak havoc with native fish and ecological 

communities as well as the importance our streams, rivers and lakes have for recreation, 

irrigation and power generation. 

By definition, ANS are those non-native plant and animal species that threaten the 

diversity or abundance of native species, the ecological stability of infested waters, or 

commercial, agricultural, aquacultural, or recreational activities dependent on such 

waters. While ANS are defined as non-native or nonindigenous, not all nonindigenous 

species are nuisance species since many alien species are non-invasive and support 

human livelihoods or a preferred quality of life. 

Despite the fact that Idaho is a landlocked semi-arid state, there are factors that make it 

extremely vulnerable to the impacts of ANS. Indeed the scarcity of water in many parts 

of the state and the overall values associated with aquatic resources demand actions to 

protect this resource. Here is why Idaho must be particularly vigilant: 

• Impacts to and from an agricultural economy that depends upon a complex 

irrigation system and which also has a flourishing aquaculture industry depending 

on quality supply waters 

• Fishing and boating opportunities on Idaho’s lakes, rivers and streams that attract 

enthusiasts from all parts of the United States 

• A growing population of new and part time residents with second homes in Idaho 

that spend part of the year pursuing recreational interests on our waters 
4

• Migratory steelhead and salmon runs in the Lower Snake, Salmon and Clearwater 

drainages that are vital to the recovery of these populations throughout the 

Northwest 

• A seaport in Lewiston where barges and tugs are exposed to international ships 

and the species that live in their holds and ballast water. 

Add to these factors the ease of buying and transporting plants for aquatic landscaping or 

exotic fish for ponds. In addition, there is a tendency for ANS to “hitchhike” on boats or 

fishing gear commonly moved between all states. For these reasons, the IISC believes 

that a separate set of actions and emphasis on ANS as a component of the state’s 

Strategic Action Plan for Invasive Species is not only justified but also essential. In 

addition, development of this ANS plan fulfills the mandate of the federal “National 

Aquatic Nuisance Prevention and Control Act for individual state plans as part of the 

national strategy on ANS and qualifies Idaho for federal funding under this Act. 

What is Idaho’s ANS Plan? 

Idaho’s ANS plan has a clear goal: 

“Minimize the harmful ecological, economic, and social impact of ANS through 

prevention of introduction. If ANS are established, manage population growth and 

prevent dispersal, within, and from Idaho.” 

The ANS plan complements the current Idaho Strategic Action Plan for Invasive Species 

and is intended to help the state coordinate efforts and secure cooperative funding to 

prevent, eradicate or control new introductions more effectively, before they cause major 

environmental and economic damage. An advisory committee consisting of state, 

federal, tribal, and private sector members, developed this plan with interagency and 

public support. This ANS plan, including its goals and objectives, is a dynamic 

document to be reviewed and revised as necessary and as situations change. 

Like the Idaho Strategic Action Plan for Invasive Species, the ANS plan recognizes that 

prevention is, in the long term, easier and less expensive than eradication and restoration. 

It is also based upon a thorough understanding of the types of ANS we might expect and 

the invasion pathways that might facilitate their entry and spread. Idaho’s ANS plan 

takes a streamlined view of categories of ANS and the threats that might be associated 

with each. There are two categories of ANS: those that are in the state now and further 

spread is undesirable, and those that are not here and which must be kept out. Granted, 

within those broad categories, there are individual species that pose greater risks than 

others. Therefore, assigning risks in each category for species helps guide rapid response 

actions, risks are based upon the following criteria: 

• High-Not Present—Species which are not present in Idaho but which would 

likely have a high adverse impact if they were to arrive. 
5

• High-Present— Those which are present in Idaho and likely to have a high 

adverse impact but are still in a potentially containable state, with areas of local 

eradication possible. 

• Medium-Present—Established species which warrant long-term control actions 

to prevent further spread. 

• Low-Not Present—Those species which may not be in Idaho but which present 

low risks of establishment or adverse impacts. 

• Low- Present—Established species where control is unlikely or which present 

low risks to the state. 

As noted in Idaho’s Strategic Action Plan for Invasive Species, there is a myriad of 

existing programs and other efforts at the federal and regional level that are in place to 

control ANS. These range from the work of the national Aquatic Nuisance Species Task 

Force (Task Force) which is responsible for reviewing and approving state plans to the 

individual programs of agencies to manage such prominent invasion pathways as the 

discharge of ballast water. They also include regional efforts such as the 100th Meridian 

Initiative directed at zebra mussel or the “Stop Aquatic Hitchhikers” campaign, which 

empowers recreational users to become part of the solution in stopping the transport and 

spread of these harmful hitchhikers 

There are state programs in Idaho, with the state departments of Agriculture, 

Environmental Quality, Fish and Game, Lands, Parks and Recreation, and Transportation 

all engaged through various initiatives of their own or through cooperative efforts at the 

state, regional or national levels. These fall into seven broad categories: 

• Early Intervention – Prevention, Early Detection, and Rapid Response 

• Containment, Control and Restoration 

• Reaching Important Audiences through Education and Training 

• Broadening Knowledge through Research and Technology Transfer 

• Assuring Adequate Funding 

• Creating an Adequate, Effective Legal Structure 

• Coordination of Efforts 

 

It is noteworthy that despite the development of the overall state strategic action plan and 

the ongoing actions of not only federal but state agencies, Idaho’s ANS plan currently 

identifies 21 gaps in those programs which need to be filled by completing 43 separate 

tasks if we are to fully prevent and control ANS in the state. These actions are 

summarized in the “Implementation Table”, which also includes the major resources 

needed, the lead entity and a timetable for completing the individual tasks. 

One final component of the state’s ANS plan is a plan for early detection and rapid 

response (EDRR) to a new or spreading invasion of an unwanted species. This EDRR 

plan mirrors a similar Columbia Basin rapid response plan that is being developed for the 
6

control of zebra\quagga mussels, which have been recently detected in the nearby 

Colorado River system. This unfortunate event, underscores the importance of vigilance 

and the ability to respond. It also provides a model for rapid response and a test of that 

model upon which Idaho’s rapid response plan is based. 
7

Acknowledgements 

The Idaho Invasive Species Council Technical Committee with support from Idaho state 

agencies and universities, federal land management agencies, tribes and numerous private 

parties, companies, and interested parties prepared this plan for Idaho. 

We would like to thank Stephen Phillips and the Pacific States Marine Fish Commission 

for providing resources and encouragement to complete this plan. 

We would like to thank the Northwest Natural Resource Group, LLC for their preparation 

of preliminary drafts. 
8

List of Acronyms 

ACOE Army Corps of Engineers 

ANS Aquatic Nuisance Species 

APHIS Animal and Plant Health Inspection Service 

BPA Bonneville Power Administration 

BOR Bureau of Reclamation 

CRANSI Columbia River Aquatic Nonindigenous Species Initiative 

CWMA Cooperative Weed Management Area 

IDEQ Idaho Department of Environmental Quality 

EDRR Early Detection, Rapid Response 

ELI Environmental Law Institute 

FIFRA Federal Insecticide, Fungicide and Rodenticide Act 

HACCP Hazard Analysis and Critical Control Points 

IDFG Idaho Department of Fish and Game 

IDL Idaho Department of Lands 

IISC Idaho Invasive Species Council 

IPR Idaho Department of Parks and Recreation 

ISDA Idaho State Department of Agriculture 

ISSG Invasive Species Specialist Group (Global Invasive Species Database) 

ITD Idaho Transportation Department 

MOU Memo of Understanding 

NANPCA Nonindigenous Aquatic Nuisance Prevention and Control Act 

NEPA National Environmental Policy Act 

NISA National Invasive Species Act 

NOAA National Oceanic and Atmospheric Administration 

NPDES National Pollution Discharge Elimination System 

NRCS Natural Resource Conservation Service 

PSMFC Pacific States Marine Fisheries Commission 

PSU Portland State University 

Task Force Aquatic Nuisance Species Task Force (national) 

TNC The Nature Conservancy 

U of I University of Idaho 

USAID United States Agency for International Development 

USBLM United States Bureau of Land Management 

USCG United States Coast Guard 

USDA United States Department of Agriculture 

USEPA United States Environmental Protection Agency 

USFS United States Forest Service 

USFWS United States Fish and Wildlife Service 

USGS United States Geological Survey 

WGA Western Governors’ Association 
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Introduction - Managing Aquatic Nuisance Species in Idaho 

Invasive Species in Idaho 

In 2003-2005, Idaho adopted both a comprehensive assessment in 2003 and the 

subsequent Idaho’s Strategic Action Plan for Invasive Species in 2005 to limit the 

introduction and spread of invasive species within the state (IISC 2003 and 2005). 

Invasive species are generally those plants and animals that are not native to an area, have 

the potential to spread uncontrollably, and when they do, to cause significant economic or 

ecological harm (IISC 2005). Idaho’s invasive species action plan recognized that these 

undesirable invaders occupy city lots and residential areas, farms and rangelands as well 

as aquatic environments, such as lakes, streams and riparian areas. While there have 

been many separate efforts to prevent and control these invasive species in the state, the 

assessment of current conditions and future efforts to manage or prevent their 

introduction to the state were based upon these premises: 

• Invasive species management in Idaho is fragmented. Responsibilities and 

authorities for invasive species management are not clearly defined for most 

agencies. There is no clear relationship among budgets, needs, and results. There 

is a need to set priorities and measure results. 

• Levels of education and awareness among landowners, policy-makers, and the 

public are not commensurate with the degree of the problem. Landowners need to 

understand their obligations to control invasive species and the costs associated 

with failure to manage them. Political leaders need to ensure adequate funding, 

appropriate legal authorities, and agency accountability. The public needs to 

understand invasive species so they become mindful of actions they can take, and 

help build broad public and political support for adequate programs. 

• Idaho has expanded significant programs for managing noxious weeds, 

agricultural pests, forest insects, and invasive species that threaten human or 

animal health. Other invasive species, such as aquatic invaders, have received 

little attention to date. 

• Resources are scarce so we must ensure that we expend them wisely. Applied 

science can help us set priorities and develop cost-effective methods for managing 

invasive species. 

• There is a need for adequate resources to do the job, including funding. This was 

perceived as the greatest barrier to effective invasive species management in 

2004, when Idaho’s invasive species action plan was being considered. 

• It is less expensive to prevent introductions of invasive species than to control 

them because of our limited ability to eradicate or control invasive species once 

they become established. Idaho’s land managers place a high premium on 
10

prevention i.e., actions to keep an invasive species from ever arriving here and on 

early detection and rapid response once an invasive species arrives. 

Idaho’s Invasive Species Council (IISC), the sponsor of the statewide assessment and 

strategic plan, anticipated subsequent detailed action strategies for invasive species by 

those entities responsible for various aspects of invasive species management and 

prevention. The specialized efforts of the “Cooperative Weed Management Areas” 

(CWMA) and the statewide coordination of this work by the Idaho State Department of 

Agriculture (ISDA) are an excellent example of an “on the ground” program. This 

aquatic nuisance species (ANS) plan is both a logical and a necessary refinement of the 

state’s overall strategic action plan. 

By definition, ANS are those non-native plant and animal species that threaten the 

diversity or abundance of native species, the ecological stability of infested waters, or 

commercial, agricultural, aquacultural, or recreational activities dependent on such 

waters. While ANS are defined as non-native or nonindigenous, not all nonindigenous 

species are nuisance species since many alien species are non-invasive and support 

human livelihoods or a preferred quality of life. ANS are the cause of significant 

ecological and socio-economic problems throughout North America. Populations of 

invasive species, such as zebra mussel Dreissena polymorpha , New Zealand mudsnail 

Potamopyrgus antipodarum, Eurasian watermilfoil Myriophyllum spicatum, and the 

parasites that cause whirling disease are increasing in prevalence nationwide. After 

introduction, these populations can expand and spread rapidly due to lack of natural 

controls and their ability to adapt to a variety of habitats. ANS can displace native 

species, clog waterways, impact municipal and industrial irrigation and power systems, 

degrade ecosystems, reduce or threaten recreational and commercial fishing 

opportunities, and can cause wildlife and public health problems. 

Many governmental agencies have recognized the threat posed by ANS. In 1990, the 

Nonindigenous Aquatic Nuisance Prevention and Control Act (NANPCA) was passed by 

Congress and enacted to address ANS problems in the United States. This legislation 

provided federal cost-share support for implementation of state ANS plans. While 

programs created by this national legislation initially were aimed at problems in the Great 

Lakes region, the reauthorization of NANPCA in 1996 as the National Invasive Species 

Act (NISA) established a national goal of preventing new ANS introductions and limiting 

the dispersal of existing ANS in all of the states. NISA specifies that state ANS plans 

identify feasible, cost-effective management practices and measures that can be 

implemented by the state to prevent and control ANS infestations in a manner that is 

environmentally sound. 

The Aquatic Nuisance Species Plan for Idaho 

Most of Idaho’s eastern border is a mountainous wall through which only four major 

rivers flow from the east. Three of the rivers, the Kootenai, the Clark Fork, and the 

Snake, are major components of the Columbia River Basin. The fourth, the Bear River in 

southeast Idaho crosses the Utah, Wyoming and Idaho borders before returning to Utah 
11

and ending in Great Salt Lake. Except for three smaller Snake River tributaries 

originating in Nevada, most of the other rivers in the state arise from within its borders, 

and virtually all of them flow into the Columbia River. These watercourses represent 

ready-made invasion pathways. The Pacific Ocean is 465 river miles away from the Port 

of Lewiston; commercial barges and tugs regularly travel the Snake and Columbia rivers 

to and from the Pacific Ocean. Recreational boating and fishing enthusiasts from across 

the country use the waterways of Idaho and neighboring states, increasing the potential 

for unwanted invasions or spread of ANS. There is a need to be doubly vigilant with 

respect to ANS in Idaho—the results of our efforts are reflected in what happens to the 

states downstream of our major rivers (Figure 1). 

Idaho has temperate to alpine climates, ranging from warmer, usually snow free river 

canyons and lower valleys to high mountain ranges with much colder water and severe 

winter conditions. However, cold-water temperatures cannot always be counted upon to 

prevent exotic species that are intolerant of cold. The state has 2,614 documented 

geothermal sources of water, primarily springs or wells (IDWR //idahogeothermal.org/) 

(Figure 2). While these generally have a negligible effect on the ambient temperature of 

larger streams, they do represent small pockets of warm water where tropical species can 

and do survive. These geothermal waters contribute to a significant portion of Idaho's 

aquacultural economy. 
12

Figure 1. Potential ANS Migration Routes between Idaho and Neighboring States. 
13

The goal of the ANS plan and the actions outlined in it are: 

“Minimize the harmful ecological, economic, and social impact of ANS through 

prevention of introduction. If ANS are established, manage population growth and 

prevent dispersal, within, and from Idaho.” 

The ANS plan is based on these assumptions: 

• Prevention is the best course of action. Species management plans, education 

programs, and regulations are strategies that can help in the prevention and spread 

of ANS 

• There are many pathways of introduction and spread for ANS, virtually all of 

which are related to human activities, both accidental and intentional 

• New introductions and the spread of existing infestations have many associated 

costs. There are the economic impacts such as lost recreational opportunities or 

damage to water conveyance systems, as well as the ecological costs of the loss of 

desirable native species and the degradation of aquatic habitats 

• Often there are few control methods available for use in water bodies once ANS 

become established. 

• Once species become established and widespread, any control efforts will usually 

be very expensive and the potential for eradication becomes very unlikely. 

The coordinated efforts contained within this ANS plan are designed to protect Idaho and 

its aquatic resources from the multitude of potential losses associated with ANS. It 

complements and adds to the current Idaho Strategic Action Plan for Invasive Species 

(IISC 2005). The ANS plan is intended to help the state coordinate efforts and secure 

long term cooperative funding to prevent, control, and hopefully, eradicate new 

introductions before they cause major environmental and economic damage. An advisory 

committee consisting of state, federal, tribal, and private sector members developed this 

plan with interagency and public support. This ANS plan, including its goals and 

objectives, will be reviewed and revised as necessary. Interested or impacted parties are 

welcome to participate in plan revisions and public comments will help provide guidance 

and support of the ANS plan’s goals, objectives and implementation strategies. 

The draft ANS plan was made available for public review from June 26 to July 27, 2007. 

Notices of its availability were provided to interested groups and published in local 

papers. Copies of the ANS plan were available in electronic or hard copy formats. Open 

houses were held in Boise, Coeur d'Alene, and Pocatello during July 2007. Public 

comments were limited and related to controlling Eurasian watermilfoil. Primary 

editorial comments were made from members of the national Task Force and IISC 

Technical Advisory Committee (Appendix A). 
14

What is At Stake? 

Despite the state, regional and federal responses to the growing challenge of invasive 

species, Idaho remains vulnerable to new introductions and unmanaged spread of existing 

ANS. Physical, social and economic factors within the state heighten the threat of 

unwanted species. Among these are: 

• Impacts to and from an agricultural economy that depends upon a complex 

irrigation system, including numerous impoundments, canals and diversion 

structures 

• Impacts to and from a flourishing aquaculture industry 

• A growing population of new and part time residents with second homes in Idaho 

that spend part of the year pursuing recreational interests on our waters 

• Fishing and boating opportunities on Idaho’s lakes, rivers and streams that attract 

enthusiasts from all parts of the United States, who bring their own boats and 

fishing gear, which may have some unwanted ANS“hitchhikers” 

• Access to maritime trade through the Port of Lewiston, via barges and tugs that 

come in contact with international ships and the species that arrive in their holds 

and ballast water 

• Migratory steelhead and salmon runs in the Lower Snake, Salmon and Clearwater 

drainages that are vital to the recovery of these populations throughout the 

Northwest 

• Impacts to ESA “threatened”, “endangered” or “candidate” species that are either 

aquatic or partially dependent on riparian areas 

• A wide variety of aquatic habitats, including mountain streams, natural lakes, 

reservoirs, and desert riparian areas, along with a large number of hot springs that 

provide unique warm water “micro-sites” 

• Expansion of private ornamental ponds, waterscapes and other water features 

• Ease of sale and rapid shipping of live organisms from anywhere in the world to 

Idaho. 

Figure 2 illustrates the important streams, lakes and other water bodies in Idaho. Their 

value for recreation, irrigation, wildlife, scenic beauty and aquaculture increases the 

potential for ANS to be a threat. An example is the undeniable value of springs in the 

Hagerman area for aquaculture, which by the nature of the industry makes the springs 
15

potential waters where ANS cab become established. One of the ways ANS might arrive 

in Idaho and infect wild fish and their habitats is through the movement of fish eggs, live 

fish or their food. Similarly, boaters attracted to our magnificent rivers and lakes, can 

inadvertently introduce invasive invertebrates, parasites or plants that adhere to boats or 

trailers. One of the greatest potential losses to Idaho from ANS is the intangible but 

incalculable value of the complex aquatic and riparian ecosystems that characterize the 

state and upon which much of our economy and lifestyles depend. 

The economic and environmental costs of harmful ANS in Idaho have not been 

adequately determined. Costs can be incurred through the loss of economic output, such 

as reductions in aquaculture, fisheries, or crop production, and also through the direct 

cost of combating and mitigating the impacts of the species (Mack et. al. 2000). 

Profitability in agriculture for example is reduced by the costs associated with controlling 

aquatic nuisance plants that clog irrigation canals. If zebra mussel or quagga mussel

Dreissena rostriformis bugensis become established in Idaho, substantial expenses would 

be involved for the maintenance of industrial, hydropower, irrigation, and water supply 

systems. The impacts of the zebra mussel in the United States have been an estimated in 

the billions of dollars annually (Khalanski 2005). 
16

Figure 2. Main waterways of Idaho. 
17

Facing the Enemy—What is out there and how might it arrive 

in Idaho? 

When species are introduced into a new environment, there is the potential for significant 

ecological, economic, and social effects. Non-native species may have few natural 

enemies, such as parasites or predators. Lack of natural enemies and the ability to adapt 

to new environments may allow a population to increase rapidly. Not all nonindigenous 

species pose an identified threat and some, such as warm water game fish can provide 

significant economic and recreational benefits in appropriate habitats. 

We cannot know what new and unanticipated ANS might surface in Idaho or surrounding 

states. Some threats are known given the impacts certain species have had in other states. 

We can anticipate their points of possible entry into Idaho, along with the areas of likely 

establishment (Figure 3). 

Types of ANS 

In general, there are three basic types of ANS: 1) harmful nonindigenous aquatic animals, 

2) harmful nonindigenous aquatic plants, and, 3) harmful nonindigenous pathogens, 

diseases and micro parasites. These organisms have the potential for significant negative 

ecological, economic, and social effects. Once introduced, the lack of natural controls 

allow a population to increase at an exponential rate. Establishment of new species can 

cause the disruption of native species in the ecosystem as the introduced species may 

prey upon, out-compete, or transmit disease to the native species. 

Animal ANS have arrived in Idaho from a variety of intentional or unintentional actions 

(Figure 3). ANS such as zebra and quagga mussels can attach to boats, fishing gear, be 

moved in the live wells, and\or bait buckets from one body of water to another. Water 

diversions allow fish or other ANS from different drainages to invade new habitats. 

Although not intentional, the ability of some ANS to "hitchhike" during importation of 

approve species can put bodies of water at risk for invasion. Although aquaculture is 

well regulated in Idaho, the out of state propagation of animals for commercial or 

recreational purposes provides a potential source for ANS. ANS may also be introduced 

through intentional, unpermitted releases of fish, baits or plants by anglers and aquarium 

owners. 
18

Figure 3. 
19

Nonindigenous aquatic plants cause significant economic and ecological problems 

throughout North America. Pathways for introduction of aquatic plant species include 

boats and trailers, the aquarium trade, nursery and garden centers, and mail order and 

internet suppliers. Many nonindigenous aquatic plant species have become established in 

the United States outside of their natural range. Vascular species such as hydrilla 

Hydrilla verticillata and Eurasian watermilfoil are examples well known for their ability 

to alter physical and biological functions of aquatic systems. They affect water quality, 

recreational uses of water, and fisheries in many states. A wide variety of pondweed 

Potomogeton spp. species clog irrigation and drainage ditches. Filamentous and 

planktonic algae can clog waterways, impact water quality, and produce toxic blooms in 

lakes and ponds. Emergent species such as purple loosestrife Lythrum salicaria and 

Japanese knotweed Polygonum cuspidatum reduce wildlife cover and habitat. Saltcedar 

or tamarisk Tamarix spp. seriously degrades wetlands, completely drying up some lakes, 

ponds, and river areas along with altering soil chemistry. 

Microorganisms include pathogens, diseases, bacteria, viruses fungi and related 

microbes. They can enter Idaho on plants or animals imported into the state or through 

the water in which plants or animals are transported. When microorganisms are allowed 

into a new aquatic environment, they also have the ability of infecting native or existing 

plants or animals. Importation of pathogenic organisms must be regulated and the spread 

of these microorganisms must be controlled. Parasites, such as Myxobolus cerebralis, the 

cause of salmonid whirling disease, may affect wild trout fisheries in Idaho, resulting in 

serious loss of recreational activity and financial loss to Idaho. Other parasites and viral 

or bacterial pathogens like Viral Hemorrhagic Septicemia can cause heavy mortalities of 

trout and salmon, plus other fish species, both those in the wild or in Idaho’s aquaculture 

industry. These viruses must be kept out of Idaho through comprehensive efforts to 

identify and control sources of their entry. Although included in this plan as ANS, many 

aquatic micro-organisms associated with fish and aquaculture are addressed through other 

state and regional programs such as the Model Comprehensive Fish Health Protection 

Program (PNFHPC 2007) and the policies of the Columbia Basin Integrated Hatchery 

Operations Team (Shelldrake et al. 1993). 

The ability to prevent entry or manage the spread of each species varies and the resources 

available are limited. Management efforts must be focused on species for which actions 

can produce the greatest benefit. In recognition of the known threats, impacts, and 

potential problems of certain ANS and the state’s current management capabilities, 

management actions should be directed toward species for which the threats are the 

highest. Idaho’s ANS plan is based on the categories of threats and risks described in this 

section. 

Although this plan is directed towards introduced ANS, information and actions in the 

plan and from future ANS work in Idaho can also be applicable for native species, which 

can become "nuisances" in our changing and altered environments. One such species that 

is native to Idaho is the stalked diatom, Didymosphenia geminate, more commonly 

known as "rock snot". This diatom can become abundant to the point of being a nuisance 

(resembling whitish-gray sewage fungus) in rivers and streams where it can form thick 
20

gelatinous mats under certain environmental conditions (Stevenson et al. 1996 as cited by 

Holderman, et. al. 2004). Actions such as cleaning equipment, taken to prevent 

movement of new species into Idaho should also be taken to prevent the movement of 

native species out of the state or into other drainages within Idaho. 

The Known Threats 

It is possible to place too much emphasis on identifying the species most likely to arrive 

or spread in Idaho and calculating the relative risks of damage if they do. It is tempting 

to do so as the basis for formulating prevention strategies and control actions that are 

based upon threats and risks. However, some species may not be obvious threats. 

Consider the appearance of “sudden oak death syndrome” in Oregon and California. 

Before it appeared, the pathogenic cause for the disease was not on any list of potentially 

invasive species. In Washington, piranhas and a potentially invasive member of the 

“tunicate” family of marine organisms from the East Coast were recently found, neither 

of which would have appeared on a watch list for that state (Joan Cabreza, USEPA, 

personal communication). While existing authorization was apparently either sufficient 

to allow funds to be spent on control measures or was quickly amended to allow this, 

valuable time can be lost if there is a requirement to modify lists of species for which 

funds can be legally directed. 

For these reasons, Idaho’s ANS plan takes a streamlined view of categories of ANS and 

their associated threats. There are two basic categories of ANS: Those that are in the 

state now and where their spread is undesirable, and those that have not yet been 

introduced and must be kept out. Within these broad categories there are individual 

species that pose greater risks than others do. Therefore, assigning risks in each category 

for species helps guide rapid response actions, risks are based upon the following criteria: 

• “High-Not Present”— Species which are not present in Idaho but which would 

likely have a high adverse impact if they were to arrive. 

• "High-Present"— Those which are present in Idaho and likely to have a high 

adverse impact but are still in a potentially containable state, with areas of local 

eradication possible. 

• “Medium-Present”— Established species which warrant long-term control 

actions to prevent further spread. 

• “Low-Not Present”— Those species which may not be in Idaho but which 

present low risks of establishment or adverse impacts. 

• "Low- Present" — Established species where control is unlikely or which 

present low risks to the state. 
21

Appendix B includes detailed descriptions of high priority species currently established 

in Idaho, and those that are not currently present here but likely to have a high adverse 

impact. Those species are summarized in Tables 1 and 2. 

Appendix C contains a list of all known aquatic nonindigenous species in Idaho. Species 

in this list include not only those that would rank in the high, medium and low criteria as 

ANS species, but also species that are currently considered beneficial in some waters of 

the state. 
22

Table 1. High-Priority Aquatic Nuisance Species known to be in Idaho 

These species are defined as present in Idaho, but still in a potentially containable state in 

known waters or with local eradication possible. 

Scientific Name Common Name 

Animals 

Potamopyrgus antipodarum New Zealand mudsnail 

Corbicula fluminea Asian clam 

Myxobolus cerebralis Whirling disease 

Plants 

Myriophyllum spicatum Eurasian watermilfoil 

Myriophyllum aquaticum Parrot feather milfoil 

Iris pseudacorus Yellow flag iris 

Potamogeton crispus Curly leaf pondweed 

Lythrum salicaria Purple loosestrife 

Tamaricaceae spp. Saltcedar 

Table 2. High Priority Species Not Currently Found in Idaho 

These species are defined as not currently present in Idaho, and likely to have a high adverse 

impact. 

Scientific Name Common Name 

Animals 

Dreissena polymorpha / Dreissena rostriformis bugensis Zebra mussel/Quagga mussel 

Mylopharyngodon piceus, Hypophthalmichthys molitrix, H. 

nobilis, Ctenopharyngodon idella 

Asian Carp (black, silver, 

bighead, grass (fertile variety)) 

Orconectes rusticus Rusty crayfish 

Neogobius melanostomus Round goby 

Gymnocephalus cernuus Eurasian ruffe 

Rhinogobius brunneus Amur goby 

Channa argus, C. maculata, C. marulius, C. micropeltes Snakehead fish, sp. 

Bythotrephes cederstroemii / Bythotrephes longimanus Spiney/fishhook water flea 

Myocastor coypus Nutria 

Viral hemorrhagic septicemia 

Plants 

Eichhornia sp. Water hyacinth 

Hydrilla verticillata Hydrilla 

Egeria sp. Brazilian elodea 

Hydrocharis morsus-ranae Frog's bit / European frogbit 

Trapa natans Water-chestnut 

Cabomba sp. Carolina fanwort 
23

The Framework for Aquatic Nuisance Species Management in 

Idaho 

Federal Policies and Efforts 

Generally, federal programs have sought to either coordinate or encourage the roles and 

activities of the individual states, although federal programs are responsible for interstate 

commerce and other related potential invasion pathways that transcend state borders. For 

example, the regulation of ballast water discharges in the Great Lakes or in coastal ports 

is a responsibility of the USGC. The growing challenge posed by ANS and the role of 

the federal government in coordination and regulation of activities that cross state or 

international borders, Congress has authorized a number of specific actions. While no 

single federal agency has clear authority over all aspects of ANS management, many 

agencies have programs and responsibilities that address aspects of the problem, such as 

importation, interstate transport, exclusion, control, and eradication. 

Nonindigenous Aquatic Nuisance Prevention and Control Act and the 

National Aquatic Nuisance Species Task Force 

The Nonindigenous Aquatic Nuisance Prevention and Control Act (NANPCA) of 1990 

established a federal program to prevent or control introduced ANS and the brown tree 

snake. The mandate is prevention, monitoring, and control with these activities 

supported by research and education. Under NANPCA, state governors are authorized to 

submit comprehensive ANS management plans to the national Aquatic Nuisance Species 

Task Force (Task Force) for approval. The plans identify areas or activities for which 

technical and financial assistance is needed. Grants are authorized to states for 

implementing approved ANS management plans. The federal share cannot exceed 75% 

of cost incurred by the State and the non-federal share must come from non-federal 

sources (www.anstaskforce.gov). 

Federal activities on ANS management are coordinated through the Task Force as 

authorized by the NANPCA. The Task Force is an intergovernmental organization 

dedicated to prevention and control of ANS, and implementing the NANPCA. The 

various NANPCA mandates were expanded later with the passage of the National 

Invasive Species Act NISA, (see below) in 1996. The Task Force consists of 10 Federal 

agency representatives and 12 Ex-officio members, and is co-chaired by the USFWS and 

NOAA. The Task Force coordinates federal governmental efforts dealing with ANS with 

those of the private sector and other North American interests via regional panels and 

issue-specific committees and work groups (www.anstaskforce.gov). When appropriate, 

the Task Force develops national species specific management and control plans. The 

current plans can be found at http://anstaskforce.gov/control.php. 

National Invasive Species Act 

 In 1996, National Invasive Species Act (NISA) amended NANPCA to mandate 

regulations to prevent the introduction and spread of ANS into the Great Lakes through 
24

ballast water and other vessel operations. This Act required a USCG study and report to 

Congress on the effectiveness of existing near-shore ballast water facilities used by crude 

oil tankers. It also authorized funding for research on ANS prevention and control in the 

Chesapeake Bay, the Gulf of Mexico, the Pacific Coast, the Atlantic Coast, and the San 

Francisco Bay-Delta Estuary. In addition, NISA required a ballast water management 

program to demonstrate technologies and practices to prevent aquatic nonindigenous 

species from being introduced into and spread through ballast water in United States 

waters. The Act also modified: 1) the composition and research priorities of the Task 

Force; and 2) zebra mussel demonstration program requirements 

(www.invasivespecies.gov). 

Invasive Species Executive Order 

In addition to these authorities, in February 1999, President Clinton signed Executive 

Order 13112, which requires all federal agencies to collaborate in developing a national 

invasive species management plan that will include terrestrial and aquatic species. This 

seeks to prevent the introduction of invasive species, provide for their control, and 

minimize their impacts through better coordination of federal agency efforts under a 

National Invasive Species Management Plan to be developed by a national interagency 

Invasive Species Council. The Order directs all federal agencies to address invasive 

species concerns as well as refrain from actions likely to increase invasive species 

problems (Federal Register 1999). The National Invasive Species Management Plan was 

finalized on January 18, 2001 and is on the national Invasive Species Council website at 

www.invasivespecies.gov. 

The response of the federal government toward the increasing threat of invasive species 

and the mandates of Congress has been to create a wide variety of federal programs. 

While not all of these directly relate to aquatic species, more than 20 federal agencies in 

10 cabinet level Departments have some responsibility for some aspect of invasive 

species management, including responsibilities for ANS (General Accounting Office 

2002). These range from the regulation of ballast water of ships coming to United States 

ports to customs inspections to the interstate shipments of animals and plants. The State 

Department even negotiates provisions aimed at preventing the movement of invasive 

species in various trade and other agreements with foreign governments. 

Individual Federal Agency Programs 

One of the lead federal agencies battling the spread of ANS is the USFWS. This agency, 

as co-chair of the ANS Task Force, provides federal funding for implementation of state 

and regional ANS management plans and maintains a number of “hands on” efforts for 

controlling ANS through training of field managers and research. Other agencies that 

maintain or support ANS programs include: NOAA, ACOE, Customs Bureau, USCG, 

plus agencies of the Departments of Energy and Agriculture (General Accounting Office 

2001). 

Table 3 summarizes the various roles of many federal agencies and the authorities 

provided to carry out these efforts (but are not exhaustive). 
Table 3. Examples of Federal Roles in Invasive Species Management 

Invasive Species Function Authorities Agencies Key R

Prevention Plant Protection Act; Animal quarantine laws; 

Lacey Act; Federal Seed Act; Nonindigenous Aquatic Nuisance Prevention and Control Act; National Invasive Species Act 

APHIS; USFWS; NOAA, USEPA, USCG, Depts. of Defense, State and Transportation (for aquatic noxious weeds) 

Prohibit or restrict impoincluding noxious weedinvasive animals and thControl weed infested sinjurious animals; Preveweeds 

Early Detection and Rapid Response 

Plant Protection Act; Animal quarantine laws; NUSEPA; 

Various agencies have the emergency authority to deal with incipient invasions 

Seize, hold, quarantine imported into the Unitestates 

Control, Management and Restoration Such acts and NFMA, FLPMA and those that 

guide the management of lands or waters under various agency jurisdiction; the Nonindigenous Aquatic Nuisance Prevention and Control Act; Clean Water Act; FIFRA; NUSEPA; Plant Protection Act; Emergency Watershed Program

Forest Service, NOAA, USEPA, BOR, ACOE, NRCS; No single agency has overall responsibility 

Control and manage invareas on federal lands a

Research and Monitoring Cooperative Agriculture Pest Survey; 

Nonindigenous Aquatic Nuisance Prevention and Control Act, various organic acts 

Various USDA, Interior agencies, NOAA, USEPA Develop databases on v

species and micro-organagricultural lands, rangerisks associated with inv

Information Management International Plant Protection Convention; 

NAFTA; Convention on International Trade in End. Species of Wild Fauna and Flora; Convention on Biological Diversity; N. American Agreement for Environmental Cooperation 

USDA agencies, Office of the U.S. Trade Representative, World Trade Organization, Depts. of Interior, Transportation, State; International Maritime Organization, USEPA, U.S. AID 

Develop strategies for i

species and share informcountries; treaty and tramanagement; 

Public Outreach and Partnership Efforts 

Various statutory authorities USDA, Dept. of Interior, NOAA Dissemination of public 

local and tribal governm

Interagency Efforts Various statutory authorities Task Force, National Invasive Species Council, Federal 

Interagency Committee on the Management of Noxious and Exotic Weeds, Committee on Environment and Natural Resources of the National Science and Technology Council 

Problem specific coopeof control and research 
26

Regional Organization and Efforts 

The Western Regional Panel on Aquatic Nuisance Species 

The Western Regional Panel (WRP) on Aquatic Nuisance Species was formed under a 

provision of the NISA in 1997 to help limit the introduction, spread, and impacts of ANS 

into western North America. The panel includes representatives from federal, state and 

local agencies and private environmental and commercial interests. The purposes of the 

WRP, as described in NISA, are to: 

• Identify regional priorities for responding to ANS; 

• Make recommendations to the Task Force, including an education, monitoring 

(including inspection), prevention, and control program to prevent the spread of 

the zebra mussel west of the l00th Meridian; 

• Coordinate, where possible, other ANS program activities in the West not 

conducted pursuant to the Act; 

• Develop an emergency response strategy for federal, state, and local entities to 

stem new invasions of ANS in the region; 

• Provide advice to public and private individuals and entities concerning methods 

of preventing and controlling ANS infestations; and 

• Submit an annual report to the Task Force describing activities within the western 

region related to aquatic nuisance species prevention, research and control. 

Idaho IDFG staff have attended the annual WRP meetings and provided reports on state 

activities since the formation of the panel. Currently the state Invasive Species 

Coordinator is the official Idaho representative. 

Western Governors Association 

The Western Governors’ Association (WGA) is involved with programs to address 

undesirable aquatic and terrestrial invasive species in the West. In 1998, the WGA 

passed Resolution 98-018, “Undesirable Aquatic and Terrestrial Species”; which in part 

directs states to develop and coordinate Western strategies and to support management 

actions to control and prevent the spread and introduction of undesirable species. In 

2005, Resolution 05-11, "Undesirable, Invasive Aquatic and Riparian Species" 

recognizes the importance of, and need for, a coordinated Western regional approach to 

all invasive species. It also directed the WGA to convene an Aquatic Invasive Species 

Working Group to develop, fund, and implement a comprehensive program to prevent the 

spread of aquatic invasive species in the water resources of the Western states. The 

Working Group shall partner with the WRP and other western groups to coordinate 

invasive species lists and efforts across the regions, establish model legislation to prevent 

the transport, sale, and dispersal of undesirable species, and develop the needed public 
27

outreach and education tools as identified by the regional working groups. (Western 

Governor’s Association, www.westgov.org). 

Pacific States Marine Fisheries Commission/Bonneville Power 

Administration Aquatic Nuisance Species Program for the Columbia River 

Basin 

In 1999, the Bonneville Power Administration (BPA), recognizing the potential impact to 

its operations, funded the Pacific States Marine Fisheries Commission (PSMFC) to carry 

out an ANS prevention program for the Columbia River Basin. The USFWS and NOAA 

Fisheries also provide program support. In addition to species-specific projects, the 

PSMFC coordinate regional ANS activities and some support funding to regional states 

in conjunction with the 100th Meridian Initiative and the Columbia River Basin ANS 

Coordinating Group. A primary emphasis is to assist states in the development of state 

ANS plans. An additional goal of this regional program is to include ANS public 

outreach in Montana, Washington, Idaho, and Wyoming in the prevention of zebra 

mussel movement. 

100th Meridian Initiative 

One major regional ANS partnership is the 100th Meridian Initiative, a cooperative effort 

among federal, state, provincial and tribal entities, potentially affected industries, and 

other interested parties to begin addressing the threat of the spread of zebra mussels and 

other ANS in the western United States. The goals of the Initiative are to be attained 

through the implementation of the following six components: 1) information and 

education, 2) voluntary boat inspections and boater surveys, 3) involvement of those who 

haul boats for commercial purposes, 4) monitoring, 5) rapid response, and 6) evaluation. 

The 100th Meridian Initiative has three subgroups or “Teams” for the Colorado, Columbia 

and Missouri Basins. Idaho participates in the Columbia River basin team, which is 

administered by the PSMFC with funding support from the USFWS and Bonneville 

Power Administration. The Columbia River ANS Team includes representation from the 

IDFG, PSMFC, Portland State University (PSU), tribal agencies, and state and federal 

entities in Oregon, Washington, Idaho and Montana. This team has developed a working 

draft rapid response plan for zebra and quagga mussels in the Columbia River Basin 

(www.100thmeridian.org/ColumbiaRT). Idaho is a participant in the Initiative and has 

conducted surveys of boater movement, developed a statewide cooperative sign program 

for marinas and is conducting early detection monitoring for zebra and quagga mussel on 

lakes and reservoirs throughout the state. 
28

 “Stop Aquatic Hitchhikers!” 

The USFWS leads the Task Force national campaign known as Stop 

Aquatic Hitchhikers!TM. Using strategic communications, social 

marketing and branding processes, the intent of the campaign is to 

unify the entire conservation community to provide consistent 

messaging about this complex issue. The campaign can empower all 

recreational users to adopt environmentally responsible behaviors to 

prevent the spread of harmful species. By targeting aquatic recreation users, Stop 

Aquatic Hitchhikers!TM strives to make stewardship inherent in all recreational 

experiences. 

A part of the Stop Aquatic Hitchhikers program has focused on the Greater Yellowstone 

Area. The focus is on attracting public-sector groups to join federal, state and county 

agencies to promote the conservation message. This public-sector momentum has 

attracted numerous nonprofit organizations like local lake homeowner associations, Trout 

Unlimited and BASS chapters, statewide marine trade associations, and local, regional 

and national environmental and conservation organizations. All of these organizations 

are complemented by diverse private sector interests including fishing tackle and boat 

manufacturers, consumer travel product companies, recreational and multi-media 

companies, regional internet publishers, hotel chains, chambers of commerce, lodges and 

full-service resorts, fly and tackle shops, marinas, dive shops and resource restoration 

businesses. Over forty businesses and nonprofits from Jackson Hole, Cody, Livingston, 

Bozeman, Ennis, West Yellowstone, Island Park and other communities of the Greater 

Yellowstone area have joined the campaign (www.protectyourwaters.net/). 

Current State Programs 

Idaho is a leader in managing invasive species, with a number of programs, task forces, 

studies, organizations and partnerships designed to identify, prevent, eradicate or manage 

various harmful species. A model for cooperation in dealing with invasive species is the 

Cooperative Weed Management Area (CWMA) which originated in Idaho. The CWMA 

concept focuses on involving all landowners in a watershed or region, developing 

integrated management plans, and defining roles and partnerships that allow for the 

blurring of jurisdictional lines of ownership. CWMA now cover more than 82 percent of 

the state. Due to the success achieved in Idaho, CWMA have become a national model 

for successful weed management across the country. 

State and local programs often work in concert with the implementation of federal 

programs, frequently sharing funding and expertise. Idaho’s current laws and programs 

address both established and potential invasive species, and combine education, 

regulation, prevention, detection and control actions as the needed basis for managing all 

invasive species, including those associated with aquatic or riparian habitats. 

A variety of Idaho laws has been passed and programs established to address each of 

these classes of invasive species (IISC 2003). They include: 
29

• Idaho’s Noxious Weed Law that addresses weed control on public and private 

lands and is administered by the ISDA and individual counties 

• IDFG authorities to govern the importation, release, sale, possession and 

transportation of any species of wildlife, which by definition includes non 

domestic fish species 

• ISDA authorities that require weed free seeds, straw for revegetation projects, and 

livestock feed, and regulate the propagation of species not classed as “wildlife” 

• Idaho’s Plant Pest Act, with its broad authorities to inspect nursery and 

horticultural operations and to quarantine areas or articles that may spread plant 

pests or plant diseases 

• IDL authorities to manage and control forest pests 

• The ability of the state or individual counties to take steps on private or state lands 

to suppress insect outbreaks or weeds or control unwanted animals 

• Broad county authority to quarantine or undertake other control mechanisms for a 

variety of invasive species. 

In 2002, the Environmental Law Institute (ELI) published “Halting the Invasion: State 

Tools for Invasive Species Management”, a comprehensive review of the laws, policies 

and programs related to invasive species management in each state. Their work 

considered state efforts to identify, prevent or control invasive species, as well as state 

level mechanisms to coordinate efforts and enforce existing laws. Among their findings 

for Idaho, ELI noted several shortcomings in Idaho’s statutory framework for invasive 

species management, including a lack of specific authority to identify future threats and 

the absence of a comprehensive statewide invasive species management plan. However, 

since ELI’s report, the state has enacted the Plant Protection Act (2002) and a new law 

addressing “deleterious animals” passed in 2003. Perhaps equally importantly, Idaho has 

attempted to address all invasive species issues in a comprehensive fashion by the 

creation of a statewide Idaho Invasive Species Council (IISC) created by Executive Order 

No. 2001-11 in 2001 (Office of the Governor 2001) and reauthorized in 2006 by 

Executive Order No. 2006-28 (Office of the Governor 2006). 

This IISC includes representatives of state, local, federal and tribal governments as well 

as private entities who “provide policy level direction and planning for combating 

harmful invasive species infestations throughout the state and for preventing the 

introduction of others that may be potentially harmful” IISC (2005). The overall goals of 

the IISC include using the existing authorities to minimize the effects of harmful nonnative species, to serve as a non-partisan forum to build understanding of invasive 

species, to encourage control and prevention, to organize and streamline the process for 

identifying and controlling invasive species, and to find ways to bring current problems 

under control (IISC 2005). The role of the IISC is to coordinate among the various 
30

public agencies and tribes toward achieving the goals outlined above, and active 

participation in the IISC is largely voluntary, except for state agencies. It operates 

without a dedicated budget, but leadership is provided by a full time statewide “invasive 

species coordinator”, established in 2004 and housed in ISDA. 

The IISC addresses all categories of invasive species, both terrestrial and aquatic. The 

purpose of the IISC is to provide policy level direction and planning for combating 

harmful invasive species infestations throughout the state and for preventing the 

introduction of others that may be potentially harmful. The IISC is charged to: 

• Minimize the effects of harmful non-native species on Idaho citizens and to 

ensure the economic and environmental well being of the State of Idaho; 

• Serve as a nonpartisan forum for identifying and understanding invasive species 

issues from all perspectives; 

• Take measures that will encourage control and prevention of harmful non-native 

species; 

• Organize and streamline the process for identifying and controlling invasive 

species; and consider ways to halt the spread of invasive species as well as finding 

possible ways to bring current problems under control. 

Table 4 summarizes the existing statutory authorities for state agencies related to invasive 

species management in Idaho (highlighted in blue) and the actions of the agencies 

charged with administering the law, including efforts directed at ANS. It should be noted 

that several other agencies have responsibilities for either assisting in the implementation 

of existing laws or for cooperating with overall efforts. For example, the IDEQ does not 

have specific statutory authority for managing invasive species even though the agency 

does monitor and report infestations of aquatic weeds or animals as part of its 

responsibilities to protect water quality within the state. 
Table 4. Summary of Idaho's Invasive Species Regulatory Authorities 

Non-Native Species:

Authority Statute Import Introduction 

IDFG 36-104 Fish and 

Game Authorities 

Permits for allowable 

species. Prohibitions against 

specific species 

Permits for allowable 

species based upon 

American Fisheries 

Society protocols. 

A

d

ISDA 22-2016, Plant Pest 

Act 

Permits for allowable species Permits for allowable 

species 

Import/Introduction/Release:

What are the general requirements for the import, introduction or release of nonnative or imported species?

ISDA 25-3900, Deleterious 

Animals 

Prohibitions and permits Prohibitions and permits 

Authority Statute Quarantine Regulations 

ISDA 22-2012, Plant Pest 

Act 

Broad authority, but specific to "plant pests". Authorizes cooper

quarantines 

ISDA, except for 

domestic sheep 

25-218, Animal 

management 

Broad authority for control of livestock di

IDL, in cooperation with 

ISDA 

36-106, Forest pests IDL, through the Forest Pest Act and ISDA, through the Plant Pest 

and have broad authorities for control and pre

Quarantines: Is there authority for 

quarantines of potentially invasive species, either for an area or for transportation through the state?

ISDA, Counties 22-2404, Noxious 

Weed Law 

Broad authority in the case of actual or potential noxiou

Authority Statute Shipping/Transportation Regula

ISDA 25-214 It is unlawful to transport animals infected with communicable dis

The law gives the Ports of Entry and the ITD authority to inspec

Federal laws govern most aspects of interstate 

Interstate Transportation and Shipping: Are there requirements for 

shipping or transportation of invasive species through the state?

IDFG, in cooperation 

with ISDA 

36-106 Wildlife that is transported is generally subject to the same rules tha

or importation. 
Table 4. Continued. 

Biological Control Agents:

Authority Statute Import Introduction 

IDFG 36-104 Fish and 

Game Authorities 

Permits for allowable 

species. Prohibitions 

against specific species 

Permits for allowable species 

based upon American 

Fisheries Society protocols 

A

ISDA 22-2016, Plant Pest 

Act 

Permits for allowable 

species 

Permits for allowable species 

ISDA 25-3900, Deleterious 

Animals 

Prohibitions and permits Prohibitions and permits 

Management of Biological Control Agents: Are there 

requirements for approval, permit or a license to use biological control agents and standards for using them?

Authority Statute Emergency Powers 

ISDA 22-2404, Noxious 

Weed Law 

Emergency Powers: Is there 

authorization of emergency powers to address invasive species outbreaks?

ISDA 22-2009, Plant Pest 

Act 

The Noxious Weed Law and the Plant Pest Act contain specific re

state agency to take emergency actions. This authority may be imp

public health, animal health, or agricultura

Authority Statute Enforcement Mechanisms 

ISDA 22-2009, Plant Pest 

Act 

The Plant Pest Act allows the ISDA to stop sales of infectious mate

actions. If landowners refuse to control pests on their lands, the IS

and impose liens on the property in the amount of the control cost

Act or misdemeanors are punishable by fines, civil penalt

ISDA 22-2409, Noxious 

Weed Law 

Violations of the Noxious Weed Law are misdemeanors punishab

Counties may impose liens and collect control costs, if they must ta

private lands. 

ISDA 25-3905, Animals Violations of the Deleterious Animal Act can result in the assess

penalties 

Enforcement Mechanisms: What 

authorities help assure the enforcement of various laws that regulate invasive species?

ISDA 25-219, Animals Failure to control animal diseases as specified in 25-200 are misde

by fines or imprisonment. 

Blue highlights are authorities related to invasive species management. 
33

Current Efforts and How We Can Be More Effective 

Idaho has a comprehensive program to prevent new introductions and spread of unwanted 

invasive species, as described in the Idaho Strategic Action Plan for Invasive Species 

(IISC 2005). Virtually all of them are relevant for the management of ANS and many are 

already being implemented by various agencies. In addition, the state’s efforts on 

invasive species management are coordinated through the IISC and the work of a fulltime invasive species coordinator. 

The responsibilities for invasive species management, including those for ANS, are 

seldom the domain of a single agency and there are overlaps and potential duplications. 

For example, new additions to the state code that address deleterious exotic species 

specifically calls for cooperation between the departments of Agriculture and Fish and 

Game in implementing the sections of the new law concerning threats to fish, wildlife or 

the environment. While many agencies have some authority to regulate ANS, no 

centralized authority or management structure exists to coordinate ANS activities in 

Idaho. In Idaho, there are a number of programs dedicated solely to the prevention of 

new introductions and spread of ANS. Some of these programs reside exclusively with 

state agencies. Others, like the state’s participation in the previously mentioned “100th

Meridian Initiative”, take the form of regional programs conducted in cooperation with 

other states or with various federal agencies. This section describes the existing 

programs in Idaho for managing ANS, including both those that are specific to individual 

state agencies along with those that cross agency boundaries and are administered 

through cooperative actions. 

1. Early Intervention – Prevention, Early Detection, & Rapid Response 

One point of consensus from the “Invasive Species Summit”, held at the request of 

Governor Kempthorne in 2004, is that it is more desirable and cost effective to prevent 

new invasions of unwanted species than to attempt to eradicate or control them once they 

become established. Prevention is a multi-faceted task that includes actions ranging from 

education of those who might inadvertently introduce unwanted species to enforcement 

of laws for inspections and quarantines. 

By far, the most effective method to control ANS and their impacts is to prevent their 

introduction in the first place. New species can arrive in Idaho by many different 

pathways. Species that provide sport fishing opportunities, erosion control, food, fur, and 

aesthetic enjoyment have been intentionally brought to Idaho and released into the wild 

or escaped from private ponds or holding facilities. Common carp Cyprinus carpio, 

goldfish Carassius auratus, nutria Myocastor coypus , Eurasian watermilfoil, and parrot 

feather milfoil Myriophyllum aquaticum can and some have become established through 

these pathways. Humans, through recreational, development, and management activities 

can unintentionally introduce ANS. ANS introduced and established in neighboring 

states and Canada may be dispersed into and throughout Idaho by natural means such as 

"hitchhiking" on domestic or wild birds and animals. Even firefighting efforts can spread 
34

ANS, when equipment used to move water to fires is not cleaned between drainages. 

Understanding how various pathways function as conduits for ANS into Idaho is critical 

for intercepting species and preventing introductions. 

Once ANS have arrived, there is usually a window of opportunity to eradicate small 

pioneering populations before they become wide spread, however species are not often 

detected until large populations are formed. Usually, it is too late or too expensive to 

eradicate a species once it has reached these levels, and when management is conducted 

after a population is well-established, long-term routine activities will often be required 

to control the population and reduce environmental impacts. By initiating an early 

detection, rapid response and monitoring program, hopefully the state will be able to 

discover and manage pioneering infestations at a point when the species can be 

eradicated in a cost effective manner. This has been successful is several recent 

terrestrial instances such as gypsy moth Lymantria dispar in north Idaho and the potato 

cyst nematode Globodera pallida in eastern Idaho. 

Some examples of early detection and rapid response to ANS or undesired fish species 

introductions into Idaho include such actions as IDFG’s efforts to: 1) Aggressively 

pursuing eradication of undesirable and non-native species of fish in select locations or as 

a result of illegal introductions, 2) Modifying fish stocking from state and federal 

hatcheries to prevent releasing fish from hatcheries with New Zealand mudsnail into 

waters where the snail is not present, and, 3) Establishing a whirling disease research and 

management program. As a partner in the 100th Meridian Initiative, IDFG made a special 

effort to communicate with boat owners and anglers in the state by providing 

informational articles to the media and in Department rule booklets. 

Responsible agencies: ISDA, IDFG, IDEQ, USFWS, PSMFC, U of I 

Major current initiatives: 

• Major initiatives coordinated at the regional level to survey for the spread of 

quagga mussel in the Columbia Basin and to educate boaters on this new threat; 

• Along with the Task Force, develop and maintain a list of taxonomic experts for 

ANS identification; 

• In 2001, with PSMFC, USFWS, and BPA funding, PSU began to recruit and 

enlist volunteers to deploy zebra mussel colonization substrates. By 2002, about 

200 substrates had been distributed in Oregon, Washington, Idaho, Wyoming, 

Montana, Arizona, Utah and other states. The PSU program also now has the 

capability to process zebra mussel veliger (larvae) samples (Stephen Phillips, 

PSMFC, personal communication). 

• Further development of the “Columbia River Basin Rapid Response Plan for 

Zebra Mussels and other Dreissena species.” 

Gaps:

• New aquatic species may not be reviewed before importation; 

• Limited inspection programs; 
35

• No agency is actively, routinely and systematically monitoring or surveying for 

new or spreading ANS; 

• Response time to an invasion is slow due to a lack of contingency plans, advance 

environmental compliance arrangements, and funding. 

Tasks

1A). Identify high-risk invasion pathways and water bodies. With this information, 

create early intervention strategies that reflect the risk and values of each. For example, 

where the risk of zebra mussel is high, develop an inspection and control program for 

trailered boats and water-based equipment, which includes appropriate wash stations for 

boats and equipment; 

1B). Conduct an annual survey of high-risk waters, utilizing both existing state and 

federal field personnel and crews specifically targeting ANS; 

1C). Work with agencies and industries to develop protocols to guide the importation 

and transport of non-native species; 

1D). Develop a “watch list” of all species where introduction or spread is unwanted, 

along with management strategies for dealing with them according to their priority class; 

1E). Refine and implement the Rapid Response Plan as outlined in Appendix D 

1F). Encourage and train volunteer groups to work in cooperation with state agencies 

to monitor for new invasions or spreads by such methods as distributing zebra mussel 

substrates; 

1G). Develop a response program that can be quickly invoked for various species 

when there is imminent threat of their introduction; 

1H). Develop, maintain and implement Hazard Analysis and Critical Control Points 

(HACCP) plans for hatcheries, field, and survey crews. 
36

...And Now There Is Another One 

Ironically, during the development of this plan, a new aquatic species that promises to 

truly be a nuisance found its way into waters in the Southwest, with the discovery of 

invasive quagga mussel in Lake Mead in January 2007. Like its better known cousin 

the zebra mussel, the freshwater quagga mussel can grow on many surfaces and form 

dense colonies that clog water pipes, foul irrigation screens and fish ladders, restrict 

water recreation, harm native aquatic life, and result in costly maintenance. In the 

event of a quagga or zebra mussel invasion, estimated maintenance and control costs 

to the Federal Columbia River Power System could run into the hundreds of millions 

of dollars, which would pass down to Pacific Northwest consumers. After the initial 

discovery of quagga mussel in Lake Mead, biologists found the invasive shellfish 

growing in the Lake Mead Fish Hatchery. Although that hatchery normally releases 

fish within the Lake Mead region, it did transport fish into Northeast Nevada’s Wild 

Horse Reservoir in April and May 2006. Wild Horse Reservoir drains into the 

Owhyee River, which flows into the Snake River. So far, surveys conducted in 2007 

in Wild Horse Reservoir have not found any quagga mussel; however, a small number 

of zebra or quagga mussel veligers were detected in Lake Powell, Utah in July 2007. 

Cross-country transport from the Great Lakes on a recreational boat is the likely route 

that recently brought quagga mussel to the Colorado River drainage. “Stopping the 

quagga mussel from entering the waters of Columbia River Basin will require the 

cooperation and vigilance of the general public,” says Randy Fisher of the Pacific 

States Marine Fisheries Commission. “Anglers, people at gas stations, and people 

using lakes, marinas, and beaches can all help by being lookouts for this invasive 

mussel.” 

Below is a list of actions boaters including personal watercraft, canoe, and kayak) and 

anglers can take to ensure that their boats, vehicles, trailers and other equipment do 

not become the means of infecting other waters: 

• Drain the water from your motor, live well, and bilge on land before leaving 

the immediate area of the lake. 

• Wash the hull, live well, equipment, and any other exposed surface, and flush 

the motor and bilges, using hot over 140 degrees F) soapy water or use a 

solution of 1 part household bleach to 19 parts water. 

• Completely inspect your vessel and trailer, removing any visible mussels, but 

also feel for any rough or gritty spots on the hull. These may be young 

mussels that can be hard to see. 

• Clean and wash your trailer, truck or any other equipment that comes in 

contact with water. Mussels can live in small pockets anywhere water collects. 

• Air-dry the boat and other equipment for at least five days before launching 

in any other waterway. 
37

2. Containment, Control and Restoration 

Some unwanted species are already here and have proven to be truly invasive. Others 

will arrive despite our efforts to prevent them. It is important to control ANS by 

eradicating small, incipient populations and by preventing the spread of larger 

populations where eradication will no longer be possible. This might be viewed as the instate version of prevention, early detection and rapid response, where the object is not to 

keep the unwanted species from our state but rather to keep those that are already here 

from spreading into other drainages. 

Aquatic Weed Efforts 

An important outgrowth of the successful approach of the CWMA has been the 

development of a parallel effort to address aquatic weeds, particularly Eurasian 

watermilfoil. Between 2003 and 2005, the Idaho Eurasian Watermilfoil Task Force (a 

subcommittee of the IISC) used almost $30,000 of ISDA CWMA funding to survey 107 

sites on 75 water bodies to provide the much needed basis for a statewide Eurasian 

watermilfoil control program (Idaho Milfoil Task Force 2006). In addition, the Idaho 

Milfoil Task Force developed educational materials and began a database of Idaho’s 

waters to help guide future survey and control efforts. Finally, the Idaho Milfoil Task 

Force is sponsoring research by the University of Idaho on control methods in small 

impoundments. There are also cooperative agreements between the Department of Fish 

and Game and the counties for controlling purple loosestrife. 

In 2006, the Legislature appropriated four million dollars for the 2006-07 treatment 

seasons to control Eurasian watermilfoil in Idaho. As directed by the Legislature, ISDA 

is using the appropriated funds to support on-the-ground eradication and control efforts. 

This included approval of 13 locally developed projects totaling $2.5 million. Over 5,000 

acres were treated, mostly with herbicides specifically approved for aquatic use. In 2007, 

the Idaho Legislature approved another $4 million for additional survey and control 

work. 

An additional program of cooperative agreements between the IDFG and CWMA is in 

place for controlling purple loosestrife along the Snake River in southern Idaho. With 

funding from CWMA, the IDFG provides boats and staff to chemically treat or to release 

and monitor biological control agents in areas infested with purple loosestrife. The 

biocontrol agents are significantly reducing large stands of this plant. In conjunction with 

this program IDL has provided funding to IDFG to help contain other noxious weeds on 

inaccessible IDL managed islands along the Snake River. 

Responsible Agencies: CWMA, IDFG, ISDA, IDL 

Major Current Initiatives: 

• Idaho agencies are using two biocontrol agents to control purple loosestrife; 

• IDFG is pursuing the eradication of undesirable and non-native species of fish in 

select locations or as a result of illegal introductions 

• IDFG has established a whirling disease research and management program; 
38

• ISDA is leading a statewide effort to control or, where possible, eradicate 

Eurasian watermilfoil from Idaho’s waters. 

• University of Idaho, USGS, and USFWS are collaborating on research and 

development of New Zealand mudsnail treatment systems for fish hatcheries. 

Gaps:

• Current efforts are directed at individual populations and not at controlling 

species in their entirety. 

• Restoration techniques and\or acceptable vegetation are lacking for artificial 

habitats such as ponds established in gravel quarries. 

Tasks:

2A). Continue surveys and control actions associated with Eurasian watermilfoil, 

including grants for local actions; 

2B). Continue current management programs for New Zealand mudsnail and whirling 

disease. Develop and implement an eradication and management program for saltcedar 

and other unfunded ANS. 
39

New Plant, Bigger Headache 

If ever an individual aquatic nuisance species illustrates both the problems it causes if 

left unchecked and the costs of control, it is Eurasian watermilfoil. Eurasian 

watermilfoil is an attractive plant with feathery underwater foliage. It was once 

commonly sold as an aquarium plant, introduced to North America many years ago 

and is now found over much of the United States. 

The spread of this plant can drastically alter a water body’s ecology. Eurasian 

watermilfoil forms very dense mats of vegetation on the surface of the water. These 

mats interfere with recreational activities such as swimming, fishing, water skiing, and 

boating. In eastern Washington, it interferes with power generation and irrigation by 

clogging water intakes. The sheer mass of plants can cause flooding and the stagnant 

mats can create good habitat for mosquitoes. Eurasian watermilfoil mats can rob 

oxygen from the water by preventing the wind from mixing the oxygenated surface 

waters to deeper water. 

Eurasian watermilfoil reproduces extremely rapidly and can infest an entire lake 

within two years of introduction to the system. Break a plant and the portion 

remaining in the lakebed continues to grow, while the piece that was broken off will 

sprout roots and grow equally well, whether in the original water body or a new one, 

transported there by the boat trailer that broke the piece off in the first place. This is 

why Eurasian watermilfoil can so easily be transported from lake to lake on boat 

trailers or fishing gear. Once established in its new home, water currents may carry 

Eurasian watermilfoil fragments and start new colonies within the same water body. 

Eurasian watermilfoil is gaining a foothold in Idaho's lakes, ponds, rivers and other 

waterways, with infestations in Idaho’s Panhandle, Payette Lake and other lakes in 

Ada, Canyon and Payette Counties. There has been approximately 4,000 surface acres 

of the plant identified through surveys that have been conducted in the state. In 2006, 

the Idaho State Legislature passed a bill that allows for $4 million in funding to 

control Eurasian watermilfoil in Idaho. An additional $4 million was approved by the 

Legislature for more control measures in 2007 and beyond. 

How do we control Eurasian watermilfoil once it has become established? Only with 

great difficulty and at great expense. The list of options narrows, ranging from using 

herbicides to installing plastic sheets on the lakebed and employing divers to hand pull 

the plants or dredge them so they can be brought to the surface and removed. IISC is 

currently developing a statewide management strategy for Eurasian watermilfoil in 

Idaho. 
40

3. Reaching Important Audiences through Education and Training 

There is a consensus that education lies at the heart of most successful efforts to prevent 

and control unwanted invasive species. The resources and the political will necessary to 

inspect, regulate and mandate control actions for all potential invasive species and all 

invasion pathways do not exist now and likely will not exist in the future. People will 

only change their behavior because they understand the risks and they want to do their 

part. Creating that climate is a function of education. 

ANS information 

IDFG has included information on ANS in the state fishing regulations, posting of signs, 

purchase and distribution of videos, video segments in IDFG “Idaho Outdoors”, and 

conducted direct mailings to permit holders. U of I provides research-based invasive 

species information, including aquatic species, and informal education programs to 

individuals, businesses, and communities. Some of the work of the U of I is disseminated 

through individual agencies, including an array of pamphlets, papers and other various 

print materials that help inform various audiences about invasive species and why they 

need to be addressed. One example of an ongoing educational effort involves the 

cooperative program to help make boaters aware of harmful aquatic invasive species like 

Eurasian watermilfoil, parrot feather milfoil, and New Zealand mudsnails that have 

already spread to many parts of Idaho. 

Marina Signage Project

In 2004, a number of partners joined together to prevent the spread of aquatic invaders by 

posting signs at boat access sites around the state. The eye-catching signs provide 

information on the threat of ANS and ask boaters to clean their vessels before entering 

and after leaving any water body. Participants include the ISDA, IDFG and IDPR. 

Federal partners include the ACOE, USBLM, USFS and the USFWS. Private and local 

participants include Ada County, the Idaho Weed Awareness Campaign, The Nature 

Conservancy (TNC), PSMFC, and the Western Whitewater Association, together with 

the USEPA, which provided funding for the signs and accompanying brochures. 

Together, the partners have raised approximately $27,000 to distribute and erect 1,500 

aluminum signs and 2,000 laminated posters (Andy Brunelle USFS and Bas Hargrove 

TNC, personal communication). 

Responsible agencies: IDFG; ISDA; IDPR, USFS, USBLM, USDA; U of I; ACOE; 

USFWS; PSMFC 

Major current initiatives: 

• IDFG has included information on ANS in the state fishing regulations, posted 

informational signs, purchased and distributed videos, published articles in “Idaho 

Outdoors” and conducted direct mailings; 

• U of I through the statewide Cooperative Extension Service provides researchbased weed information and informal education programs to individuals, 

businesses, and communities. A variety of extension programs include invasive 

species issues including ANS; 
41

• USFWS provides training, signs, and informational brochures; 

• The PSMFC is completing an ANS boater survey and has been conducting 

outreach and education efforts of marinas in the state of Idaho and other states for 

the past four years. With partners such as the USFWS and BPA, PSMFC has 

been conducting watercraft inspection training for boating law enforcement/safety 

staff professionals. A watercraft inspection training video has also been 

developed. The PSMFC also prints and distributes ANS educational materials 

(brochures, cards, key chains) to recreational boaters in the Columbia River basin 

at sport and outdoor shows. The PSMFC also supports Portland States 

University’s zebra mussel monitoring program activities (Stephen Phillips, 

PSMFC, personal communication). 

Gaps:

• There is no systematic effort to identify all audiences with a stake in ANS 

prevention and control and then to develop a comprehensive strategy across state 

and federal agencies to reach those audiences; 

• Little training is provided to agency and private personnel to identify ANS and to 

provide avenues to report new sightings. 

Tasks:

3A). Develop a comprehensive education program to raise the awareness of ANS 

introduction and spread for such businesses as nurseries, aquatic pet stores, bait dealers, 

private pond management firms, fish hatcheries, irrigation managers and entities with 

watershed management responsibilities; 

3B). Develop a comprehensive education program to raise the awareness of ANS 

introduction and spread for county, state and federal agency field staffs; 

3C). Provide information on ANS to managers of fishing tournament and various 

sportsmen or recreational groups; 

3D). Build and maintain a comprehensive website on ANS in Idaho highlighting high 

risk water bodies, high risk species and high risk actions that might lead to introduction 

or spread. Incorporate ways to report new sightings of ANS through this website; 

3E). Train enforcement personnel on ANS regulations and the field workers of all 

county, state and federal agencies to better equip them to identify new or spreading ANS; 

Use IDPR boat safety education training program as a foundation, 

3F). Develop an annual report focused on ANS in Idaho and use it as an opportunity to 

reach decision makers and opinion leaders on the need for proper policies and funding for 

ANS efforts; 

3G). Develop and maintain statewide advertisements, PSAs, signing programs and 

other methods of communication with the public to remind them of ANS threats and the 

need for such personal actions as cleaning fishing or boating equipment;

3H). Create an ANS component to the established Project Wild and Project Wet 

curricula for students;

3I). Assign state employees to public education and outreach activities;
42

3J). Increase the capabilities of those who interact with invasion pathways (aquatic pet 

dealers, live plant distributors, irrigation districts, others) to understand the potential harm 

from the introduction and spread of ANS into uncontrolled environments. 

4. Broadening Knowledge through Research and Technology Transfer 

Little is known about the extent and magnitude of the ANS problem in Idaho. In fact 

many more nonindigenous species may occur in Idaho than are recognized (Appendix C). 

Of these nonindigenous species, we still do not know which have the potential to become 

ANS. Information and research is needed to quantify and clarify the effects that 

nonindigenous species are having on native species and habitat. Research can identify 

the threat posed by ANS and the mechanism responsible for their movement. By 

compiling available information and by providing quick access to information on 

taxonomy, management methods, and experts to contact; the response to new ANS can 

be quick, and existing ANS can be readily recognized and managed. 

It is not enough, however, to simply compile data and conduct research. The lack of 

awareness concerning ANS impacts is one of the largest obstacles to preventing the 

introduction and spread of unwanted species. Few people understand the threat ANS 

pose and how their actions might introduce them. Uninformed people, through the 

dumping of an aquarium or a bait bucket, launching of a contaminated boat, or stocking 

of a private pond have introduced many species. The improper importation and holding 

of plants and animals have allowed species to escape, or caused the receipt of unwanted 

species mixed in with intentionally imported ones. In the past, many policy makers, 

natural resource administrators, and private interest groups have facilitated the intentional 

introductions of species for economic or recreational purposes without fully 

understanding the effects these species would have on native species. Currently, IDFG 

requires a review of new species using the American Fisheries Society's introduction 

policy (IDFG 2007). These intentional and unintentional methods of introduction can be 

eliminated or curtailed by educating people about their potential to transfer ANS into 

Idaho. 

There is much to be learned about invasive species. Legitimate areas of inquiry include 

their biological parameters, how they can best be controlled and the assessment of the 

risks of their arrival, spread and potential damage. We must also increase our ability to 

predict their occurrence, detect, map and monitor their presence. It is equally important 

that the results of research and the practical experience of others be synthesized and made 

available to Idahoans. There are excellent models for research and technology transfer in 

the agricultural research and extension programs carried out by land grant universities 

across the country. Many of these programs are directly applicable or could be easily 

expanded to include invasive species. 

Responsible Agencies: IISC, U of I, IDFG research, federal agency research programs 

Major Current Initiatives:
43

• The U of I, has two graduate students working on New Zealand mudsnails 

research, including testing a device to rid hatcheries of New Zealand mudsnails; 

• U of I is involved in the development of biological control agents for Common 

Reed and potentially Eurasian watermilfoil 

• U of I researchers are exploring development of a risk assessment model for 

ANS; 

• The IISC has requested that U of I conduct a review of invasive species research 

in Idaho; 

Gaps:

• There are no risk analysis protocols for aquatic species; 

• There is limited understanding of the impacts of ANS. 

Tasks:

4A). Using nationally developed risk assessments and research as a basis, focus 

necessary additional research efforts on the potential harm and control methods for 

specific ANS for Idaho, 

4B). Evaluate the potential for aquarium and live food fish to serve as vectors of 

disease and parasites to native fish populations; 

4C). Continue investigation on the effects of such established ANS as the New Zealand 

mudsnails or whirling disease on native species; 

4D). Research the impacts management alternatives have on ANS and native species; 

4E). Investigate and develop new and innovative methods of managing ANS, 

including the efficiency of herbicides and various other management practices in aquatic 

and riparian habitats; 

4F). Facilitate the collection and dispersal of information, research, and data on ANS 

in Idaho through a central source for reference information and data; 

4G). Using nationally developed risk assessments as a basis, develop ANS risk 

assessment guidelines that will help local government and other managers understand the 

potential impacts and the need to manage ANS; 

4H). Develop a set of uniform definitions and terms to describe ANS. 

5. Assuring Adequate Funding 

There are three certainties. First, most ANS efforts are public sector programs and these 

must have sufficient dollars to support them. Second, the costs of preventing and 

controlling ANS will increase as commerce and travel increase. Mounting an adequate 

defense against ANS will require more funds and most of those will come from either 

federal or state sources. Third, it is far less expensive to prevent rather than control, and 

dollars can be saved in the long term through adequately funded prevention measures. 
44

Responsible Agencies: The Idaho Legislature and the United States Congress provide 

funding for state and federal agency efforts. Other funds are available through grant 

programs and the collection of user fees. 

Major Current Initiatives: 

• The Idaho Legislature provided funding for Eurasian watermilfoil control; 

• Legislation to increase boater registration fees has been approved. A portion of 

those fees could go to ANS efforts. 

Gaps:

• Limited funding to implement laws relating to ANS, particularly the lack of a 

dedicated fund that is stable and continually available for ANS efforts. 

Tasks:

5A). Identify possible funding sources for implementing Rapid Response Plan actions; 

5B). Increase existing funding and resources for ANS management and explore new 

funding possibly through permit fees or other sources; 

5C). Create stable funding sources for ANS management in Idaho by seeking federal 

funding from the NANPCA and other potential funding sources 

6. Creating an Adequate, Effective Legal Structure 

Laws are needed to address management efforts to prevent the introduction and spread of 

ANS. Those laws fall into two categories—those that seek to shape behavior and those 

that spell out the role and functions of government for ANS. In Idaho, there is a strong 

existing legal framework but there is perhaps a need for some adjustments that would 

markedly increase our effectiveness, as summarized in Table 4. 

At least five separate statutes provide some authority for state departments, primarily 

Fish and Game and Agriculture, to take actions to prevent the introduction or spread of 

aquatic nuisance species (IISC 2005). 

They are: 

• 36-100, Fish and Game authorities; 

• 25-3900, Deleterious Animals; 

• 25-2600, Extermination of Wild Animals and Pests; 

• 22-2400, Noxious Weed Act; 

• 22-2001, Plant Pest Act. 

These authorities provide most regulatory powers that might be necessary to detect, 

prevent or control most ANS. There are some gaps in needed authorities and questions to 

be answered. For example, it is not clear whether any agency has the authority to 
45

impound or order the cleanup of a boat entering the state with zebra mussel or other ANS 

attached to it. There are also some apparent overlapping authorities. IDFG’s general 

authorities to control imports of various wildlife species would seem to overlap the 

authorities given the ISDA under the “Deleterious Animals” statute. 

Granted, much of what can be accomplished is a function of education and coordination 

among the various agencies. A first step in detecting an undesirable species or pathway 

that might harbor ANS is to make sure those who encounter them know how to recognize 

them. This requires that those in the IDFG, IDPR, IDT or other agencies help train port 

of entry personnel, conservation officers or law enforcement officials on what to look for 

and what actions to take. However, the regulatory authorities are important as well, for if 

someone is trained to recognize a dangerous situation from an ANS standpoint but cannot 

take the necessary control actions, the detection holds little value. 

Responsible agencies: IDFG; ISDA, IDPR, IDT 

Current initiatives: 

• Implementation of Plant Pest Act and Deleterious Animal Act, as they apply to 

ANS. 

Gaps:

• Limited authority and funding to quarantine species and infested waters; 

• Limited ability to monitor direct mail shipments or internet sales that might 

introduce or spread ANS; 

• Limited authority to inspect, regulate or control ANS in private ponds; 

• Agencies lack the authority to inspect and quarantine a specific water body once 

an ANS is detected; 

• Vague authority for search, detention and seizure for suspected carriers of ANS. 

Tasks:

6A). Promote legislation and regulatory rules that establish or increase the state's 

authority to control the introduction of new species, including such authorities for 

detaining and require cleaning of any vehicle, vessel or water based equipment 

containing or infested with ANS that is traveling in Idaho; 

6B). Increase the ability of the State to regulate the importation of aquatic organisms, 

including requirements that imported aquatic organisms are disease and parasite free; 

6C). Establish the authority to quarantine water bodies to prevent ANS from spreading 

and to contain ANS for future eradication; 

6D). Develop policies, rules and if needed legislation to prevent the introduction of 

ANS into private ponds, including increased authority to inspect ponds, remove ANS 

species and provide penalties for illegal introductions of ANS into private ponds; 

6E). Assure that existing laws controlling the transport, propagation, sale, collection, 

possession, importation, purchase, cultivation, distribution, and introduction of ANS are 

enforced; 
46

6F). Establish and administer a program for ANS management efforts that allow state 

agencies to quickly respond to new detections of ANS in Idaho. 

7. Coordination of efforts 

The proposals in this ANS plan envision additional efforts that must be efficient and 

coordinated, which poses a significant challenge. While more work is clearly needed, it 

is difficult for those who currently have invasive species responsibilities to find time to 

assume new duties. In addition, each of those managers works within an existing 

program such as weed management, plant or forest pests or fisheries management. 

Therefore, it is impossible for any one of them to assume a statewide role for the 

management of all invasive species. Finally, a myriad of federal actions also affects state 

efforts. An ANS coordinator would help unify Idaho’s efforts and add to them. 

The IISC developed the previously mentioned statewide assessment and a Strategic 

Action Plan for Invasive Species and, in 2007, hired an Idaho Invasive Species 

Coordinator to improve the coordination of invasive species activities within the State of 

Idaho. Staff works to coordinate efforts throughout Idaho by working with state 

agencies, federal agencies, local governments and non-governmental organizations to 

address the IISC’s recommendation to ensure that a comprehensive invasive species 

program in Idaho is not diluted by competing efforts among various agencies. 

Responsible agencies: IISC, ISDA 

Current initiatives: 

• An implementation plan for Idaho’s Action Plan for Invasive Species has been 

developed to set program priorities for developing work plans, assign 

accountability, prepare budgets, and report activities; 

• The IISC is working with the U of I to conduct a Research Review for invasive 

species in Idaho; 

• The IISC is developing a list of unwanted and high risk species that should trigger 

rapid responses in Idaho; 

• The IISC is developing a system to display location data on invasive species in 

Idaho: 

 

• The IISC is identifying key audiences and educational efforts needed to reach 

them; 

• The IISC is establishing a single statewide point of contact and clearinghouse for 

reporting new or spreading invasive species and for disseminating information 

about them; 
47

• The IISC is coordinating USEPA Wetlands Grant efforts with the Idaho Milfoil 

Task Force and the development of the ANS Management Plan. 

 

Gaps:

• There is no clear authority or agency charged with limiting and managing ANS; 

• Most management activities are focused on isolated problems or are speciesspecific and do not address the issue of ANS strategically; 

• ANS activities are currently uncoordinated in Idaho and the region; 

• The lack of a strategic plan to deal with some ANS has allowed some species to 

become established in Idaho, and new introductions are not being monitored, 

prevented or eradicated; 

• No single state agency has a clear program directed at controlling or eradicating 

ANS across taxa. 

Tasks:

7A). Develop cooperative agreements and or MOUs with states and provinces that 

share common waters; 

7B). Participate in monitoring and/or rapid response efforts for high priority ANS in 

Idaho; 

7C). Develop partnerships with private groups to fund prevention and eradication 

efforts; 

7D). Coordinate all ANS management programs and activities within Idaho through 

the IISC; 

7E). Create and fund a state ANS coordinator position using Task Force monies and 

matching funds; 

7F). Continue participation in the Task Force’s Western Regional Panel and support 

for such regional or national efforts as the 100th Meridian Project or the Columbia River 

Aquatic Nonindigenous Species Initiative (CRANSI). 

Closing the Net on ANS—Idaho’s Plan 

The purpose of this plan for ANS is to create a clear focus on those species and to spell 

out additional actions needed within the state to effectively prevent new or spreading 

invasions. It is meant to supplement the overall invasive species strategy for the state. In 

order to do this, it is necessary to focus attention on those existing ANS efforts as well as 

to review the progress toward implementing relevant actions that were adopted through 

the statewide invasive species strategy. Thus, the ANS plan can serve as both a review of 

progress to date and an identification of any shortcomings in current or proposed efforts, 

which, if corrected, would strengthen Idaho’s ANS programs. 

The advisory group charged with the developing Idaho’s plan for ANS has identified 

changes, which need to take place if we are to have an effective program of managing 

these unwanted species. The elements of this ANS plan, together with the agency or 

other entity responsible for initiating the action items and what will be necessary for them 
48

to meet those responsibilities are summarized in Table 5. In addition to funding, there is 

a primary need for prioritization of staff time by agencies to meet the ANS challenge. 

With finite resources available to agencies, a greater prioritization will be dependent on 

increased education and awareness of ANS issues. 
49

 

What Does it Take to Close the Net? 

It might be easy to assume that preventing the entry and spread of aquatic nuisance 

species is something a “government agency” does. Federal and state agencies do have 

a clear role, whether is it inspecting interstate shipments of plants or animals, surveys 

of streams or control of species that have escaped to areas where they are not wanted. 

However, there is an equally important role that individuals not only can play, but 

must, if we are to achieve the goals of this plan. Often the actions that individuals take 

tell the tale of whether aquatic nuisance species are not introduced or their spread 

prevented. Here are a few simple steps that sportsmen, homeowners and farmers can 

take in order to do their part in controlling aquatic nuisance species. 

• Use only bait that is approved by the Idaho Department of Fish and Game and 

never dump unused bait or live fish, crawfish or insect larvae into a lake or 

stream, 

• Always check your boat and trailer for strings of aquatic weeds or strange 

mollusks that might adhere to fenders or transoms, when leaving an area or 

before moving to a new stream or lake. Remove those you find. 

• Watch for strange or new mollusks or weeds in irrigation ditches, storage 

ponds or on headgates. Call a representative of Idaho Department of Fish and 

Game or the Idaho Department of Agriculture if something seems out of the 

ordinary. 

• Clean the mud off the soles of your waders after you leave a stream, 

particularly if you are going to a new area. Wash and if possible, complete dry 

equipment between waters. 

• Never dump aquarium plants or fish in an area where they might enter a stream 

or pond. Never use live tropical fish like goldfish as bait. 

• Be cautious when planning for an ornamental outdoor pond or fountain to 

make sure the plants and fish you want in it cannot follow a downstream flow 

into a neighboring stream. 

• Coordinate with neighboring states and provinces on the permitted introduction 

of any new species and species which are on the ANS watch lists. 
Table 5. Summary of Needed Implementation Actions 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

1A Identify high-risk invasion pathways and water bodies. 

With this information, create early intervention strategies that reflect the risk and values of each. For example, where the risk of zebra mussel is high, develop an inspection and control program for trailered boats and water-based equipment 

IISC Agency commitments 

for staff and funding 

Fall 0

1B Conduct an annual survey of high-risk waters, utilizing 

both existing state and federal field personnel and crews specifically targeting ANS 

ISDA, IDFG, 

IDEQ 

ANS Coordinator, .66 

FTE, $100,000 

annually, training and 

coordination 

Spring

1C Work with agencies, industries to develop protocols to 

guide the importation and transport of non-native species that might become nuisances if they spread to uncontrolled environments 

ISDA, IDFG 

1D Develop a “watch list” of all species where 

introduction or spread are unwanted, along with management strategies for dealing with them according to their priority class 

ISDA, IDFG 

1E 

Refine and implement the Rapid Response Plan as outlined in Appendix D 

IDFG, IPR, 

ISDA 

1. Early Intervention – Prevention, Early Detection, & Rapid Response 

1F Encourage and train volunteer groups to work in 

cooperation with state agencies to monitor for new invasions or spreads by such methods as distributing zebra mussel substrates 

ISDA, IDPR, 

IDFGI 
Table 5. Continued. 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

1G Develop a system that can be quickly invoked for 

various species when there is imminent threat of their introduction 

IDFG, IDEQ Training Fall, 0

IH Develop, maintain and implement Hazard Analysis and 

Critical Control Points (HACCP) plans for hatcheries, field, and survey crews 

IDFG, ISDA, 

IDEQ 

Training Ongoi

2A Continue surveys and control actions associated with 

Eurasian watermilfoil, including grants for local actions 

2. Containment, ISDA, IISC Funding OngoiControl and Restoration 

2B Continue current management programs for New 

Zealand mudsnail and whirling disease. Develop and implement an eradication and management program for saltcedar and other unfunded ANS 

IDFG, ISDA, 

IDEQ, IDPR 

Funding Spring

3A Develop a comprehensive education program to raise 

the awareness of ANS introduction and spread for such businesses as nurseries, aquatic pet stores, bait dealers, private pond management firms, fish hatcheries, irrigation managers and entities with watershed management responsibilities 

IISC Funding Fall, 0

3B Develop a comprehensive education program to raise 

the awareness of ANS introduction and spread for county, state and federal agency field staffs 

IISC Funding Fall, 0

3. Reaching Important Audiences through Education and Training 

3C Provide information on ANS to managers of fishing 

tournament and various sportsmen or recreational groups 

IDFG Funds for brochures Fall, 0
Table 5. Continued. 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

3D Build and maintain a comprehensive website on ANS 

in Idaho, highlighting high risk water bodies, high risk species and high risk actions that might lead to introduction or spread. Incorporate ways to report new sightings of ANS through this website 

IISC 

3E Train enforcement personnel on ANS regulations and 

the field workers of all county, state and federal agencies to better equip them to identify new or spreading ANS. Use the IDPR Boat Safety Education training program. 

IDPR, IDFG, 

ISDA, 

 Winter 0

3F Develop an annual report focused on ANS in Idaho and 

use it as an opportunity to reach decision makers and opinion leaders on the need for proper policies and funding for ANS efforts. 

IISC, IDFG, 

ISDA 

 Fall 

3G Develop and maintain statewide advertisements, PSAs, 

signing programs and other methods of communication with the public to remind them of ANS threats and the need for such personal actions as cleaning fishing or boating equipment 

IISC, IDFG, 

IDPR 

3H Create an ANS component to the established Project 

Wild and Project Wet curricula for students. 

IDFG Summe

3I Assign state employees to public education and 

outreach activities. 

 IDPR, IDFG, 

U of I 

3J Increase the capabilities of those who interact with 

invasion pathways (aquatic pet dealers, live plant distributors, irrigation districts, others) to understand the potential harm from the introduction and spread of ANS into uncontrolled environments 

ISDA 
Table 5. Continued. 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

4A Using nationally developed risk assessments and 

research as a basis, focus necessary additional research efforts on the potential harm and control methods for specific ANS for Idaho 

U of I 

4B Evaluate the potential for aquarium and live food fish 

to serve as vectors of disease and parasites to native fish populations 

U of I, IDFG, 

ISDA 

Funding Fall, 0

4C Continue investigation on the effects of such 

established ANS as New Zealand mudsnails or whirling disease on native species. 

U of I Funding Fall, 0

4D Research the impacts management alternatives have on 

ANS and native species. 

U of I 

4E Investigate and develop new and innovative methods 

of managing ANS, including the efficiency of herbicides and various other management practices in aquatic and riparian habitats. 

U of I 

4F Facilitate the collection and dispersal of information, 

research, and data on ANS in Idaho through a central source for reference information and data. 

IDFG, ISDA 

4G Using nationally developed risk assessments as a basis, 

develop ANS risk assessment guidelines that will help local government and other managers understand the potential impacts and the need to manage ANS 

IISC 

4. Broadening Knowledge through Research and Technology Transfer 

4H Develop a set of uniform definitions and terms to 

describe ANS 

IDFG, IISC Ongoi

5. Assuring Adequate Funding 

5A Identify possible funding sources for implementing 

Rapid Response Plan actions. 

IISC Fall, 0
Table 5. Continued. 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

5B Increase existing funding and resources for ANS 

management and explore new funding possibly through permit fees or other sources. 

IDFG, IDPR, 

IISC 

 Fall, 0

5C Create stable funding sources for ANS management in 

Idaho by seeking federal funding from the NANPCA Act and other potential funding sources. 

IDFG, IISC Fall, 0

6A Promote legislation and regulatory rules that establish 

or increase the state's authority to control the introduction of new species, including such authorities for detaining and require cleaning of any vehicle, vessel or water based equipment containing or infested with ANS that is traveling in Idaho. 

ISDA, IDFG, 

ITD, IDPR 

 Fall, 0

6B Increase the ability of the State to regulate the 

importation of aquatic organisms, including requirements that imported aquatic organisms are disease or parasite free. 

IDFG, ISDA 

6C Establish the authority to quarantine water bodies to 

prevent ANS from spreading and to contain ANS for future eradication. 

IISC 

6. Creating an Adequate, Effective Legal Structure 

6D Develop policies, rules and if needed legislation to 

prevent the introduction of ANS into private ponds, including increased authority to inspect ponds, remove ANS species and provide penalties for illegal introductions of ANS into private ponds. 

IDFG Fall, 0
Table 5. Continued. 

Category

Task 

Number Recommendation Lead Entity Major Resource Needs Start D

6E Assure that existing laws controlling the transport, 

propagation, sale, collection, possession, importation, purchase, cultivation, distribution, and introduction of ANS are enforced 

IDFG, ITD, ISP 

6F Establish and administer a program for ANS 

management efforts that allow state agencies to quickly respond to new detections of ANS in Idaho 

IISC 

7. Coordination of efforts 

7A Develop cooperative agreements and or MOUs with 

states and provinces that share common waters. 

IISC 

7B Participate in monitoring and/or rapid response efforts 

for high priority aquatic nuisance species in Idaho 

IDFG, ISDA, 

IDEQ, IDPR 

7C Develop partnerships with private groups to fund 

prevention and eradication efforts 

IISC 

7D Coordinate all ANS management programs and 

activities within Idaho through the IISC 

IISC 

7E Create and fund a state ANS coordinator position using 

Task Force monies and matching funds 

IDFG, IISC Fall, 0

7F Continue participation in the Task Force’s Western 

Regional Panel and support for such regional or national efforts as the 100th Meridian Project or the Columbia River Aquatic Nonindigenous Species Initiative (CRANSI) 

IDFG, IISC Fall, 0
56

Glossary 

Accidental introduction: an introduction of nonindigenous aquatic species that occurs as 

the result of activities other than the purposeful or intentional introduction of the species 

involved, such as the transport of nonindigenous species in ballast water or in water used 

to transport fish, mollusks, or crustaceans for aquaculture or other purposes. 

Aquatic nuisance species: a plant or animal species that threatens the diversity or 

abundance of native species, the ecological stability of infested waters, or commercial, 

agricultural, aquacultural, or recreational activities dependent on such waters. (Note: for 

the purposes of the State management plans, reference to an aquatic nuisance species will 

imply that the species is nonindigenous.) 

Biocontrol: The use of living organisms, such as predators, parasites, and pathogens, to 

control pest insects, weeds, or diseases. 

Control: eradicating, suppressing, reducing, or managing nuisance species populations, 

preventing spread of nuisance species from areas where they are present, and taking steps 

such as restoration of native species and habitats to reduce the effects of nuisance species 

and to prevent further invasions. 

Ecological integrity: the extent to which an ecosystem has been altered by human 

behavior; an ecosystem with minimal impact from human activity has a high level of 

integrity; an ecosystem that has been substantially altered by human activity has a low 

level of integrity. 

Eradicate: the act or process of eliminating an aquatic nuisance species. 

Established: An introduced organism with a permanent population(s), i.e., one that has 

the ability to reproduce and is not likely to be eliminated by humans or natural causes. 

Exotic: (same as nonindigenous and non-native) any species or other variable biological 

material that enters an ecosystem beyond its historic range, including such organisms 

transferred from one country to another. Species may or may not be classified as a 

nuisance species. 

Fouling: entanglement, clogging, or obstruction by an undesired organism often resulting 

in diminished functioning of ships, intake pipes, and other submerged equipment or 

machinery. 

High Risk species: an ANS that is considered to be a significant threat to Montana 

waters and is recommended for immediate or continued management action to minimize 

or eliminate their impact. 
57

Intentional introduction: all or part of the process by which a nonindigenous species is 

purposefully introduced into a new area. 

Introduction: The intentional or unintentional escape, release, dissemination, or 

placement of a species into a Idaho ecosystem as a result of human activity. 

Invasive: (same as nuisance) a species that takes over a new habitat where it was not 

previously found, often to the detriment of species which were there before. 

Native species: A species within its natural range or natural zone of dispersal, i.e., within 

the range it would or could occupy without direct or indirect introduction and/or care by 

humans. Existing within a historical ecological range, usually within a balanced system 

of coevolved organisms. 

Nonindigenous species: any species or other variable biological material that enters an 

ecosystem beyond its historic range, including such organisms transferred from one 

country to another. Species may or may not be classified as a nuisance species. 

Pathogen: a microbe or other organism that causes disease. 

Pioneer infestation: a small ANS colony that has spread to a new area from an 

established colony. 

Watershed: an entire drainage basin including all living and nonliving components.
58

Sources 

100th Meridian Initiative; (www.100thmeridian.org/ColumbiaRT) 

Cabreza, J. 2002. Invasive Species: Issue Evaluation and Proposed Region 10 

Approach. Unpublished USEPA internal memorandum. Seattle. 

Environmental Law Institute. 2002. Halting the Invasion: State Tools for Invasive 

Species Management. Washington, D.C. 

Eurasian Water Milfoil Task Force. 2006. report. 

Federal Register. 1999. Invasive Species. Executive Order No. 13112. Vol. 64, Pgs. 

6183-6186. Washington, D.C. 

General Accounting Office. 2001. Invasive Species: Federal and Selected State Funding 

to Address Harmful, Nonnative Species. Report to Congress. Washington, D.C 

General Accounting Office. 2002. Invasive Species: Clearer Focus and Greater 

Commitment Needed to Effectively Manage the Problem. Report to Executive Agency 

Officials No. 03-01. Washington, D.C. 

Global Invasive Species Database: www.issg.org/database

Holderman, C., R. Hardy, P. Anders, H. Andrusak, K. Ashley, J. Hammond, and B. 

Shafii. 2004. Kootenai River Ecosystem Project; An Ecosystem Approach to Evaluate 

and Rehabilitate a Degraded, Large Riverine Ecosystem. 2005-2004 Technical Report, 

Project No.199404900, 269 electronic pages, BPA Report DOE/BP-00004029-1. 

Idaho Department of Fish and Game. 2007. Fisheries Management Plan 2007-2012. 

Boise. 

Idaho Interactive Geothermal Map, Idaho Department of Water Resources, (www. 

idahogeothermal.org). 

Idaho Invasive Species Council. 2003. Preparing to Meet the Challenge: An Assessment 

of Invasive Species Management in Idaho. Northwest Natural Resource Group, LLC. 

Idaho Department of Agriculture. Boise. 

Idaho Invasive Species Council and the Northwest Natural Resource Group, LLC. 2005. 

Idaho’s Strategic Action Plan for Invasive Species. Idaho Department of Agriculture. 

Boise, Idaho. 

Khalanski, M. 2005. Economic Impacts of Aquatic Invasive Species. Workshop, July 

2005. U.S. Environmental Protection Agency, Unpublished Report. 
59

Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Evans, M. Clout, and F. Bazazz. 2000. 

Biotic Invasions: Causes, Epidemiology, Global Consequences, and Control. Issues in 

Ecology 5. Washington: Ecological Society of America. 

McAllister, P. E. 1990. Viral Hemorrhagic Septicemia of Fishes. U.S. Fish and Wildlife 

Service, Fish Disease Leaflet 83. Accessed online at 

www.lsc.usgs.gov/fhb/leaflets/83.asp

National ANS Task Force; www.anstaskforce.gov. 

National Invasive Species Council, www.invasivespecies.gov. 

New Zealand Mudsnails: www.esg.montana.edu/aim/mollusca/nzms

NOAA VHS factsheet: www.glerl.noaa.gov/res/Programs/ncrais/resources/VHSVfactsheet.pdf 

Office of the Governor. 2001. Executive Order No. 2001-11 Establishing the Idaho 

Invasive Species Council. Boise, Idaho. 

Office of the Governor,. 2006. Executive Order No. 2006-28 Continuing the Idaho 

Invasive Species Council. Boise, Idhao. 

Protect Your Waters and Stop Aquatic Hitchhikers, (www.protectyourwaters.net/). 

Shelldrake, T., C. Christianson, L. Peck, B. Hutchison. 1993. Integrated Hatchery 

Operations: Existing Policy Affecting Hatcheries In The Columbia River Basin 

Combined Reports. Report to Bonneville Power Administration. Contract No. 

1991BP60629, Project No. 199204300. 228 electronic pages BPA Report DOE/BP60629-1. 

Schering-Plough Animal Health: Aquaculture (VHS): 

www.spaquaculture.com/default.aspx?pageid=534 

Stevenson, R. J., M.L. Bothwell, and R.L. Lowe. 1996. Algal Ecology. Academic 

Press. San Diego, as cited by CA. Stockner, J. G., E. Rydin, and P. Hyehstrand. 2000. 

Cultural oligotrophication:

USDA National Invasive Species Data Center: 

www.invasivespeciesinfo.gov/plants/saltcedar.shtml

USDA plants data: plants.usda.gov/index.html 

USGS Nonindigenous Aquatic Species Database: nas.er.usgs.gov/queries; 

Western Governor’s Association, http://www.westgov.org. 
60

Whelan, G. E. 2007. Viral Hemorrhagic Septicemia (VHS) Briefing Paper. Michigan 

Department of Natural Resources. 4pp. Accessed online at 

www.michigan.gov/documents/dnr/Viral-Hemorrhagic-Septicemia-Fact-Sheet-11-9-

2006_178081_7.pdf 

Whirling Disease: whirlingdisease.montana.edu/default.asp 

Zebra and quagga mussels: www.100thmeridian.org/zebras.asp
61

Appendix A. Idaho’s ANS Technical Advisory Committee 

Department\Agency Appointee Address Phone Email 

IDFG Fred 

Partridge 

PO Box 25, 600 

South Walnut 

Boise, ID 83707 

208-334-

3791 fpartridge@idfg.idaho.gov 

Coeur d'Alene Tribe Dave Lamb 

401 Annie 

Antelope Rd. 

Plummer, ID 

83851 

208-686-

6206 dlamb@cdatribe-nsn.gov 

ISDA Amy Ferriter aferriter@idahoag.us 

IDEQ Mark Shumar 

1410 North Hilton 

Boise, ID 83706-

0417 

208-373-

0132 Mark.Shumar@deq.idaho.gov 

IDL Eric Wilson ewilson@idl.idaho.gov 

UI Christine 

Moffitt 

208-885-

7047 cmoffitt@uidaho.edu 

IPR Mary 

Lucachick 

208-334-

4180 ext 

037 

mlucachick@idpr.state.id.us 

IPR David Dahms ddahms@idpr.state.id.us 

IDT Cathy Ford 

PO Box 7129 

Boise, ID 83707-

1129 

334-

8416 cathy.ford@itd.idaho.gov 

Idaho Aquaculture 

Association Linda Lemon iaa@northrim.net 

Idaho Association of 

Counties Tom Kerr twkfrk@ctcweb.net 

TNC Bas Hargrove 

950 W Bannock 

St, Ste 210 

Boise, ID 83702 

350-

2207 bhargrove@TNC.ORG 

PSMFC Stephen 

Phillips Stephen_Phillips@psmfc.org 

Oregon Department 

of Fish and Wildlife James Gores James.K.Gores@state.or.us 

USEPA Joan Cabreza Cabreza.joan@epa.gov 

USFWS Paul 

Heimowitz 

911 NE 11th Ave, 

6E 

Portland, OR 

97232-4181 

503-872-

2763 

Paul_Heimowitz@fws.gov 

USFS Jim Olivarez jolivarez@fs.fed.us 

University of Florida 

Center for Aquatic 

and Invasive Plants 

Bill Haller 

7922 NW 71st St. 

Gainesville, FL. 

32653 

352-392-

9615 whaler@ufl.edu 

USACE – 

Waterways 

Experiment Station 

Kurt 

Getsinger 

3909 Halls Ferry 

Road 

Vicksburg, MS 

39180-6199 

601-634-

2498 getsink@wes.army.mil 

Office of Species 

Conservation Nate Fisher nfisher@osc.state.id.us 

Portland State 

University Mark Sytsma systsmam@pdx.edu 
62

Appendix B. Species and Categories 

HIGH-PRIORITY 

AQUATIC NUISANCE SPECIES 

CURRENTLY FOUND IN IDAHO 

These species are defined as present in Idaho, but still in a potentially containable state, 

with local eradication possible. 

New Zealand mudsnail Potamopyrgus antipodarum 

Ecology: This very small snail (average size 5 mm) can be found in all types of aquatic 

habitats from eutrophic mud bottom ponds to clear rocky streams. It can tolerate a wide 

range of water temperatures (except freezing), salinity, and turbidity in clean as well as 

degraded waters. It feeds on dead and dying plant and animal material, algae, and 

bacteria. Its tolerance of a broad range of ecological factors makes the possibility of 

further spread likely. 

Densities have been known to reach over 300,000 individuals per square meter. A species 

as prolific as this has potential to be a biofouler at facilities drawing from infested waters. 

It also may compete for food and space occupied by native snails. The species degrades 

habitat due to its high reproductive capacity and the subsequent impacts on invertebrate 

food sources. Fish receive little, if any, nutritive value from eating the New Zealand 

mudsnail. The snail has an operculum that it closes when threatened, which prevents 

digestive juices from reaching the soft tissue of the snail’s body when ingested by fish. 

Distribution: New Zealand mudsnail have become established in all major river 

drainages in Yellowstone National Park, in the Madison River Drainage in Montana, at 

several other locations in the western United States, and in Lake Ontario, New York. 

Native to New Zealand but long established in Australia and Europe, this species was 

discovered in North America in 1987 in the Snake River in south-central Idaho, and has 

now spread throughout the Snake River Basin and elsewhere in the state. 

Pathways of Introduction: This aquatic snail most likely accompanied live game fish 

shipped from their native waters to western rivers in the United States. Other modes of 

transportation may include hitchhiking on recreational equipment and other equipment 

used in water, in the guts of harvested or transported fish, or via transport on waterfowl 

and other aquatic birds. 

Management considerations: Their large populations at many sites, small body size and 

broad environmental tolerance, make the New Zealand mudsnail well adapted to 

accidental transport by humans. As an asexual live-bearer, a single individual can start a 

new population. However, there is no resistance stage, nor is there any attachment 

mechanism, so fairly simple precautions should prevent accidental transport. While these 

snails can live for weeks if wet and cold, they are quickly killed by heat or thorough 

drying. 
63

• Very small and found in all types of aquatic habitats from mud 

bottom ponds to clear rocky streams 

• Prolific, with potential to foul facilities drawing from infested waters 

• Degrades habitat due to its high reproductive capacity and 

subsequent impacts on invertebrate food sources 

• Discovered in the Snake River in south-central Idaho, and has now 

spread throughout the Snake River Basin 

• Most likely accompanied live game fish shipped from infested waters 

to western rivers, and transportation may include hitchhiking on 

recreational equipment 

• A single individual can start a new population 

• Fairly simple precautions should prevent accidental transport

New Zealand mudsnail 
64

Asian clam Corbicula fluminea

Ecology: A bivalve native to tropical and subtropical waters, the Asian clam is a filter 

feeder that removes particles from the water column. It can be found at the sediment 

surface or slightly buried. Its ability to reproduce rapidly, coupled with low tolerance of 

cold temperatures, can produce wild swings in population sizes from year to year in 

northern water bodies. Factors that may affect population density and distribution of 

Asian clams include excessively high or low temperatures, salinity, drying, low pH, silt, 

hypoxia, pollution, bacterial, viral and parasitic infections, inter- and intraspecific 

competition, predators, and genetic changes. 

The most prominent effect of the introduction of the Asian clam into the United States 

has been biofouling, especially of complex power plant and industrial water systems. It 

has also been documented to cause problems in irrigation canals and pipes and drinking 

water supplies. It alters benthic substrate and competes with native species for limited 

resources. 

Distribution: The Asian clam was introduced to the eastern United States in the early 

20th century. It has since spread to most of the waterways in the east, and somewhat less 

widely in the west. In Idaho it is currently found in the lower Boise River in Ada and 

Canyon Counties, and in the Snake River from C.J. Strike Reservoir in Elmore County 

downstream. 

Pathways of Introduction: Corbicula fluminea was thought to have first entered the 

United States as a food item. With man shown to be the primary agent of dispersal, no 

large-scale geographic features function as dispersal barriers. It is thought to spread 

primarily through human activity such as bait bucket introductions, accidental 

introductions associated with imported aquaculture species, and intentional introductions 

by people who buy them as a food item in markets. The only other significant dispersal 

agents are water currents or flooding events. Fish and birds are not thought to be 

dispersal vectors. 
65

• Native to tropical and subtropical waters 

• Filter feeder that removes particles from the water column 

• Most prominent effect has been fouling of complex power 

plant and water systems, with documented problems in 

irrigation canals and pipes and drinking water supplies 

• Currently found in the C.J. Strike Reservoir in Elmore 

County and in the Snake River at the Idaho-Washington 

state line 

• It is thought to spread primarily through human activity 

such as bait bucket introductions; there are no large-scale 

geographic barriers 
66

Whirling Disease Myxobolus cerebralis 

Ecology: Whirling disease is caused by a metazoan parasite that can infect most wild or 

farm-raised salmonid species, although rainbow trout and cutthroat trout appear to be 

more susceptible than other trout species. This parasite has a two-host life cycle which 

includes both the primary salmonid host and a common aquatic worm Tubifex tubifex. 

When an infected fish dies and decays, spores are released and ingested by tubifex 

worms. The spores undergo development in the worm's intestine and multiply rapidly. 

When released by the worm, the water-borne spores infect susceptible fish by attaching to 

the fish's body. The parasite then migrates through the skin to the central nervous system 

and the cartilage of the fish. The spores are believed to be capable of remaining dormant 

in mud for thirty years. 

Whirling disease afflicts juvenile fish (fingerlings and fry) and causes skeletal 

deformation and neurological damage. Fish "whirl" rather than swim forward, find 

feeding difficult, and are more vulnerable to predators. The mortality rate is high for 

fingerlings, up to 90% of infected populations, and those that do survive are deformed by 

the parasite residing in their cartilage and bone. They act as a reservoir for the parasite, 

which is released into water following the fish's death. 

Distribution: M. cerebralis was first recorded in North America in 1956 in 

Pennsylvania, having been introduced via infected trout imported from Europe, and has 

spread steadily south and westwards. Until the 1990s, whirling disease was considered a 

manageable problem affecting rainbow trout in hatcheries. However, it has recently 

become established in natural waters of the Rocky Mountain states including Idaho in 

1987, where it can cause heavy mortalities in trout populations. Some streams in the 

western United States have lost 90% of their trout. 

Pathways of Introduction: The manner in which whirling disease was spread to Idaho 

is not known, but may have been a result of aquaculture release. Other avenues for 

spread of this disease include landscape/fauna "improvement", live food trade, 

transportation of domesticated animals, transportation of habitat material, and water 

currents. Wild salmonid populations may have been infected through the alimentary 

tracts of fish-eating migratory birds. 

Management considerations: As young fish are the most susceptible, management 

techniques have traditionally focused on controlling exposure of fry to the infectious 

stage of M. cerebralis, which are microscopic spores called triactinomyxons. Hatcheries 

have previously done this in two ways: 1) rear the young fish in well water to prevent 

exposure until they are older and more resistant, or 2) use pond designs that reduce 

potential habitat for oligochaetes. New research suggests that exposing water to 

unltraviolet light can inactivate triactinomyxons. A dose of 1300 mWs cm-2 ultraviolet 

light can inactivate 100% of the triactinomyxons. 

For reasons that are poorly understood, but probably have to do with environmental 

conditions, the impact on infected fish has been greatest in Colorado and Montana and 

least in California, Michigan, and New York. 
67

Recreational anglers can help to prevent the spread of the parasite in a number of ways. 

Cleaning fishing equipment between fishing trips and never transporting fish from one 

body of water to another should protect against cross contamination of waterways. 

Spores are particularly persistent in felt soled wading shoes, which can be treated with 

10% chlorine bleach and water for at least 15 minutes and then rinsed thoroughly. Fish 

bones or entrails should never be disposed of in any body of water, since spores from the 

carcass will be released into the waterway. Salmon and trout should not be used as bait. 
68

• Caused by a parasite that can infect most wild or farm-raised 

salmonids, particularly rainbow trout and cutthroat trout 

• When an infected fish dies and decays, spores are released and 

ingested by tubifex worms. When released by the worm, the 

water-borne spores infect susceptible fish by attaching to the 

fish's body. 

• Spores are believed to be capable of remaining dormant in 

mud for thirty years 

• Afflicts juvenile fish and causes skeletal deformation and 

neurological damage 

• First recorded in North America in 1956 in Pennsylvania, 

having been introduced via infected trout imported from 

Europe. Established in natural waters of the Rocky Mountain 

states including Idaho in 1987), where it may causing heavy 

mortalities in wild trout populations 

• Recreational anglers can help to prevent the spread of the 

parasite by cleaning fishing equipment and never transporting 

fish from one body of water to another 

• Fish bones or entrails should never be disposed of in any body 

of water, since spores from the carcass will be released into 

the waterway 
69

Eurasian watermilfoil Myriophyllum spicatum

Ecology: This is a submersed, rooted, perennial vascular plant consisting of long 

underwater stems that branch and produce whorled, finely divided leaves near the water 

surface. It colonizes lakes, ponds, shallow reservoirs, low energy areas of rivers and 

streams, and the brackish water of protected tidal creeks and bays. Key factors in the 

plant’s success is its ability to reproduce through stem fragmentation and seeds. A single 

segment of stem can take root and form a new colony. 

Eurasian watermilfoil competes aggressively to displace and reduce the diversity of 

native aquatic plants. It survives and photosynthesizes under the ice in winter and begins 

spring growth earlier than most native aquatic plants. Tolerant of low water 

temperatures, it quickly grows to the surface, forming dense canopies that overtop and 

shade the surrounding vegetation. Canopy formation and light reduction are significant 

factors in the decline of native plant abundance and diversity observed when Eurasian 

watermilfoil invades plant communities. Typical dense beds restrict swimming, fishing 

and boating, clog water intakes and result in decaying mats that foul lakeside beaches. 

Eurasian watermilfoil has less value as a food source for waterfowl than the native plants 

it replaces. Although fish may initially experience a favorable edge effect, the 

characteristics of Eurasian watermilfoil's overabundant growth negate any short-term 

benefits it may provide fish in healthy waters. At high densities, its foliage supports a 

lower abundance and diversity of invertebrates and other organisms that serve as fish 

food. 

Distribution: First documented in 1942 in a pond in Washington D.C., Eurasian 

watermilfoil probably was intentionally introduced to the United States from Europe, 

possibly for aquarium use. Spread westward into inland lakes primarily by boats and 

water birds, it reached the Midwestern states between the 1950s and 1980s. It is now one 

of the most widely distributed of all nonindigenous aquatic plants, having been confirmed 

in 45 United States and in the Canadian provinces of British Columbia, Ontario and 

Quebec. In Idaho it is abundant throughout the northern and southwestern portions of the 

state. 

Pathways of Introduction: It is not known exactly how Eurasian watermilfoil was 

introduced into Idaho, but it was likely carried by boats and/or water birds. Fragments 

clinging to boats and trailers can spread the plant from lake to lake. Once the plant is 

established it is almost impossible to eradicate. 

Management considerations: The occurrence of sixteen species of including 

Potamogeton illinoensis and Potamogeton pectinatus may be indicators of conditions 

suitable for Eurasian watermilfoil invasion. Searching areas colonized by these species 

may provide early detection, the best method for preventing new infestations. 
70

Several aquatic herbicides are available for control of Eurasian watermilfoil, including 

fluridone, 2,4-D, diquat, endothall, copper and confentrazone. Mechanical harvesting has 

also been widely used in the Midwest and the northeast. 

A North American weevil, Euhrychiopsis lecontie, is widely associated with Eurasian 

watermilfoil and may be linked with natural declines at northern lakes. Studies have 

found the herbivorous weevil occasionally causes significant damage to Eurasian 

watermilfoil while having no impact on native species. However, extensive testing over 

the past decade has shown its effects are unpredictable and research on this agent is 

ongoing. 
71

• Submerged, rooted, perennial herb with long underwater stems 

that branch and produce many whorled, finely divided leaves 

near the surface 

• A single segment of stem and leaves can take root and form a 

new colony, displacing and reducing the diversity of native 

aquatic plants 

• Dense beds restrict swimming, fishing and boating, clog water 

intakes and result in decaying mats that foul lakeside beaches. 

• Probably intentionally introduced to the United States from 

Europe, possibly for aquarium use, spread westward into 

inland lakes primarily by boats and water birds 

• Abundant throughout the western and southwestern portions of 

the state, as well as in numerous watersheds in the north 

• Fragments clinging to boats and trailers can spread the plant 

from lake to lake 

Eurasian watermilfoil 

Myriophyllum spicatum 

(Eurasian watermilfoil) 
72

Parrot feather milfoil Myriophyllum aquaticum

Ecology: Parrot feather milfoil exhibits two different leaf forms depending on whether it 

is growing as a submersed plant or as an emergent shoot extending above the water 

surface. The submersed leaves are 1.5 to 3.5 centimeters long and have 20 to 30 

divisions per leaf while the emergent leaves are 2 to 5 centimeters long and have 6 to 18 

divisions per leaf. The bright green emergent leaves are stiffer and a darker green than 

the submersed leaves. 

Parrot feather milfoil grows in sluggish waters, edges of streams, lakes, ponds, drainage 

and irrigation ditches, and canals, backwaters, sloughs and lagoons. It appears to be 

adapted to high nutrient environments, and does well in good light and a slightly alkaline 

environment. 

Populations often become dense and sometime occur as floating mats that have been 

uprooted, often choking waterways and impeding navigation. While parrot feather 

milfoil may provide cover for some aquatic organisms, it can seriously change the 

physical and chemical characteristics of lakes and streams. Infestations can alter aquatic 

ecosystems by shading out the algae in the water column that serve as the basis of the 

aquatic food web. In addition, the plant severely restricts water flow in both natural and 

artificial channels, providing choice mosquito larvae habitat. The plant can restrict water 

flow in canals and recreational opportunities. 

Distribution: Parrot feather milfoil is a popular aquatic garden plant offered for sale by 

retailers throughout the United States. However, it has escaped cultivation and spread via 

plant fragments and intentional plantings. Parrot feather milfoil is also spread by floods, 

animals, boating and other recreational activities. In Idaho it is presently found in the 

Clearwater subbasin and in the lower Payette and Boise basins. 

Pathways of Introduction: Parrot feather milfoil’s route into Idaho is not known, but 

may have been via waterfowl or boats. It was first reported in the Clearwater drainage 

about 50 miles east of Moscow in 1928. It is currently still offered to sale for water 

gardens throughout the United States. 

Management considerations: Mechanical control of parrot feather milfoil usually 

provides only temporary reduction of biomass and can spread plant fragments 

downstream or to other locations where they can start new growth. There are no known 

bio-control agents that are in widespread use and grass carp do not eat a significant 

amount of any of the milfoil families. Several contact and systemic herbicides offer 

temporary reduction in plant biomass. The most effective, long term control might be 

achieved by treating plants that are exposed by drawdown of water levels so that a greater 

portion of the vegetation comes into contact with the herbicide. 
73

• Grows in sluggish waters, edges of streams, lakes, ponds, 

drainage and irrigation ditches 

• Floating mats may choke waterways and impede navigation 

• Provides choice mosquito larvae habitat 

• A popular aquatic garden plant that escaped cultivation and 

spread via plant fragments and intentional plantings 

• Presently found in the Clearwater subbasin and in Emmett, 

Twin Falls, and some private ponds in Ada County 

• First reported in the Clearwater about 50 miles east of 

Moscow in 1928 

• Mechanical methods that cut up stems will increase the spread 

of parrot feather milfoil 

Parrot feather milfoil 

Myriophyllum aquaticum 

Parrot feather milfoil 
74

Yellow iris Iris pseudacorus

Ecology: Yellow iris is a perennial monocot plant that forms dense stands along the 

margins of water bodies. It thrives in temperate climates, and can grow in water up to 25 

cm deep. It is a fast-growing and fast-spreading invasive plant that dominates other 

wetland plants, forming almost impenetrable thickets. All parts of the plant are 

poisonous, especially the rhizomes, and caution should be used when hand-pulling this 

plant because it causes skin irritations. 

Once established, yellow iris thick tuberous rhizomes can tolerate both prolonged anoxic 

and/or drought conditions, and its rhizomes and seeds can be transported downstream for 

further spread. The rhizome mat can prevent the germination and seedling growth of 

native plant species. The mat also creates improved habitat for yellow iris by compacting 

soil and elevating the topography, thereby creating a drier habitat with an increased rate 

of sediment and organic matter accumulation. 

Distribution: Yellow iris is not equally distributed or problematic throughout the 40 

states in which it is reported. It is relatively new to the western United States, where 

early records from California and western Montana date to the 1950s. Yellow iris is 

widespread in the northeastern United States, where it has been found in the wild for 

close to 140 years. In Idaho, it is found in streams and irrigation canals in Latah, 

Benewah, Ada, Canyon, Boise, Jerome, and Twin Falls counties.

Pathways of Introduction: It has typically been introduced as an ornamental, but has 

also been used in erosion control and for making dyes and fibers. It remains a 

horticultural favorite and often escapes cultivation to spread along shorelines, stream 

flats, and into fresh and brackish marshes. 

Management considerations: Because of its strong tendency to resprout from rhizomes, 

burning is not recommended for control. Similarly, fire in late summer was not found to 

suppress seedling recruitment the following spring. Yellow iris is susceptible to many 

registered herbicides. It can be controlled either by directly applying herbicides to 

foliage, or by immediately applying herbicide to freshly cut leaf and stem surfaces. 
75

• Forms dense stands of robust plants that are fast-growing and 

fast-spreading, out-competing other wetland plants, forming 

almost impenetrable thickets 

• All parts of the plant are poisonous 

• Relatively new to the western United States, where notable early 

records from California and western Montana date to the 1950s 

• It is found in streams and irrigation canals in Latah, Benewah, 

Ada, Canyon, Boise, and Twin Falls Counties

• Still a horticultural favorite and often escapes cultivation to 

spread locally 

• Cutting followed by herbicide glyphosate) treatment may be the 

best method for controlling plants in sensitive sites 
76

Curly-leaf pondweed Potamogeton crispus

Ecology: Curly-leaf pondweed is a perennial, rooted, submersed aquatic vascular plant 

native to Eurasia, Africa, and Australia. It is found in freshwater lakes, ponds, rivers and 

streams, and in slightly brackish waters. This pondweed shelters small fish and aquatic 

insects that provide food for larger fish and amphibians but becomes invasive in some 

areas because of its tolerance for low light and low water temperatures. These tolerances 

allow it to preempt native plants in the early spring. 

By late spring it forms dense mats which may interfere with recreation and limit the 

growth of native aquatic plants. By July, this plant senesces and forms vegetative 

propagules called turions which are dispersed by water movement throughout a water 

body. 

In some lakes, it coexists with native plants and does not cause significant problems. In 

other lakes, it becomes the dominant plant and interferes with late spring and early 

summer recreation due to the formation of dense mats. Its mid-summer senescence 

triggers an increase in phosphorus concentrations sometimes causing algae blooms, and 

dying plants pile up along the shore. 

Distribution: This species is widespread throughout the northern United States. 

Although its first arrival in Idaho is not known, it has been reported since at least 1973, 

and is currently found in several counties in southeastern, western, and northern Idaho. 

Pathways of Introduction: Curly-leaf pondweed can spread by plant fragments attached 

to boats and equipment. Its turions may also be transferred to uninfested lakes through 

human or animal transport or by water currents. 

Management considerations: Curly-leaf pondweed has a unique lifecycle, which 

influences management options for its control. It is the first pondweed to resume growth 

in spring and dies back during mid-summer. Before it dies, it forms vegetative 

propagules called turions (hardened stem tips) that disperse by water movement. Turions 

lie dormant during summer when native plants are growing, and germinate in late fall or 

early spring when most native vegetation has died back. Long-term management of 

curly-leaf will require the reduction or elimination of turions to interrupt its life cycle. 

Management activities should be undertaken in spring or very early summer to have the 

maximum benefit. Mechanical control includes raking, cutting or harvesting vegetation. 

Raking and hand cutting generally remove the plants at the sediment surface while 

harvesting removes the top 5 ft of the plant. Mechanical methods control plants in the 

specific areas where they are causing a nuisance, and there is immediate relief from the 

nuisance. There is some evidence that early season cutting of pondweed at the sediment 

surface can prevent turion production. 

There are no known biocontrol agents. Early spring herbicide treatments, repeated over a 

2-3 year period, have been shown to reduce the density of this species significantly. It is 

susceptible to several herbicides, but both herbicides and mechanical control are 

expensive. 
77

• Invasive in some areas because of its tolerance for low light 

and low water temperatures, which allow it to get a head start 

on and outcompete native plants in the spring 

• As the pondweed dies back and decomposes in the midsummer, phosphorus is released into the water column which 

can cause algal blooms. 

• In Idaho since at least 1973, and currently found in several 

counties in southeastern, western, and northern Idaho 

• Spread by plant fragments attached to boats and equipment 

that are not properly cleaned 

• Before it dies, it forms vegetative reproductive buds called 

turions that lie dormant during the summer and germinate 

when most native vegetation has died back 

Curly-leaf pondweed 

Potamogeton crispus 

(Curly-leaf pondweed) 
78

Purple loosestrife Lythrum salicaria

Ecology: Purple loosestrife is an emergent, perennial plant with a woody stem and 

whirled leaves. It has the ability to reproduce prolifically by both seed dispersal and 

vegetative propagation. It is capable of invading a variety of wetland habitats, including 

marshes, river and stream banks, pond edges, lakes, road site ditches, and reservoirs. The 

plant prefers moist soil with neutral to slightly acidic pH. Once established, however, 

purple loosestrife can exist in a wide range of soil types. Disturbed areas are more prone 

to invasion because exposed soil is ideal for seed germination. 

As purple loosestrife establishes itself, it outcompetes and replaces native grasses, sedges, 

and other plants that provide a higher quality food source and habitat for wildlife. It can 

deleteriously impact wildlife habitat used by birds and furbearers. Purple loosestrife 

forms dense homogeneous stands that restrict native wetland plant species, including 

some endangered plants. Purple loosestrife dominates wetlands and almost entirely 

eliminates shallow open water habitat if left uncontrolled. The recreational and aesthetic 

value of wetlands and waterways is diminished as dense stands of purple loosestrife 

choke waterways and decrease biodiversity. Its vegetative dominance may increase the 

likelihood of listing additional native species as “threatened” or “endangered” under the 

ESA. 

Distribution: It is currently found in the wild in 42 of the 48 contiguous states and is 

widespread in Idaho’s wetlands. 

Pathways of Introduction: Purple loosestrife can spread via floating vegetation/debris, 

landscape/fauna "improvement", garden escape or garden waste, and water currents. 

Purple loosestrife is also widely sold as an ornamental in states where regulations do not 

prohibit its sale and distribution. In Idaho, it is listed as a noxious weed and its sale is 

prohibited. 

Management considerations: Herbicides are most commonly used for quick, effective 

control of purple loosestrife. They may be most effectively applied when plants are 

preparing for dormancy; however, mid-summer and late season treatments may be 

needed to reduce the amount of seed produced. Multiple chemical treatments are usually 

required as new seedlings emerge annually from the seed bank. 

Although chemical control measures are effective, they are usually costly. In the United 

States, four insects from Europe have been approved by the APHIS for use as biological 

control agents: The root-mining weevil Hylobius transversovittatus, two leaf-feeding 

beetles Galerucella calmariensis and G. pusilla, and Nanophyes marmoratus, an 

herbivorous weevil. G. calmariensis, G. pusilla and H. transversovittatus have been 

released across the United States and Canada. In many release sites G. calmariensis has 

provided successful control of the target weed in as little as 3 years by reducing plant 

populations as much as 100%. The two leaf beetles have been successful in Idaho, with 

little to no impact on native, non-target species. 
79

• Can reproduce prolifically by both seed dispersal and 

sprouting. invading a variety of wetland habitats, including 

marshes, river and stream banks, ponds and lakes 

• Outcompetes and replaces native grasses, sedges, and other 

flowering plants that provide a higher quality food source and 

habitat for wildlife 

• Widely available as an ornamental in states where regulations 

do not prohibit its sale 

• Imported from Europe for its medicinal value and for the 

beautiful purple spikes of the blooming plant 

• Twenty-four states, including Idaho, have listed it as a noxious 

weed and prohibit its sale 

• USDA has approved four insects for biological control of 

purple loosestrife

Purple loosestrife 
80

Saltcedar Tamarix ramosissima 

Ecology: Saltcedar is a deciduous shrub that can appear as a small tree. It can be found 

where its roots reach the water table, such as floodplains, along irrigation ditches and on 

lake shores and it can tolerate a wide range of saline or alkaline soils. Periods without 

access to the water table are also well tolerated, which contributes to its becoming an 

invasive species in Idaho. 

Saltcedar benefits from altered hydrology, especially where natural flooding is attenuated 

by water regulation. Alteration of natural flooding regimes through dam construction 

has resulted in saltcedar replacing many native tree species in riparian areas, such as 

cottonwood Populus deltoides and willows Salix spp.. The invasion of saltcedar along 

streams is likely to have altered the food webs in these aquatic ecosystems. The roots of 

saltcedar bind together gravel and cobble riverbeds, resulting in enlarged bars and 

narrowed channels, which contribute to flooding, accelerated erosion, and undercutting of 

the stream banks. 

The leaf litter and foliage produced by saltcedar is flammable and encourages the spread 

of wildfires. Native vegetation and wildlife are destroyed in these fires, saltcedar 

seedlings are fire tolerant and can re-sprout more successfully than native plants 

following fire. Moreover, enormous numbers of seeds—up to half a million per year 

from a mature shrub—are spread by wind or fire. 

Saltcedar is also known to transpire large amounts of groundwater, which desiccates soils 

and lowers the water table. Its transpiration rate is similar to native plants on a per-leaf 

basis but it maintains a larger leaf area per ground area, and therefore uses more water. 

Because saltcedar can take up water from non-saturated soils, it has an added advantage 

in out competing native vegetation. 

Saltcedar supports few native insects and is considered poor habitat for birds. It is able to 

dominate floodplain communities in desert environments due to its ability to tolerate 

water stress for extended periods. 

Distribution: This species is found in nearly all of the 48 contiguous states of the United 

States including Idaho, where it is found in several locations throughout the Snake River 

Basin. 

Pathways of Introduction: Saltcedar is thought to have been introduced to North 

America from its native Eurasia in the 19th century by the nursery trade. It is widely 

available for sale as an ornamental, due to its feathery foliage and its profusion of white 

or pink flowers. It has also been use as windbreaks. In coastal environments it has been 

used for sand-binding and has become naturalized in many coastal areas. In addition to 

deliberate spread by humans, it can also spread easily by its abundant wind-borne seeds.

Management considerations: An integrated management approach that incorporates 

multiple control techniques is most widely used in the western United States. Mechanical 

control methods (hand-pulling, cutting, bulldozing) or chemical applications are effective 
81

but can be expensive and/or labor intensive. Cattle and goats will eat saltcedar, but 

grazing alone is not a feasible control method in many locations. However, goats might 

be able to control dense stands of saltcedar where little native vegetation is present, 

particularly if the stands are cut or burned first, allowing goats to eat the regrowth. 

A biocontrol agent, the saltcedar leaf beetle Diorhabda elongata, has been released in 

certain areas in nine western states. It is anticipated that control by the leaf beetle will 

occur gradually because three years of defoliation are required for major dieback, with 

very little mortality of host plants. A mealy bug Trabutina mannipara and a weevil 

Coniatus tamarisci have also been approved for re-introduction by 

APHIS, but not yet released pending results from beetle introductions. Several other 

specialist herbivores are being studied for their biocontrol potential. 
82

• A deciduous shrub or small tree usually found in areas with a 

shallow water table 

• The leaf litter and foliage are flammable and encourage the 

spread of wildfires 

• Known to transpire large amounts of groundwater, which 

desiccates soils and lowers the water table 

• Found in several locations throughout the Snake River Basin 

• Introduced to North America from its native Eurasia by the 

nursery trade and still widely available for sale as an 

ornamental 

• Mechanical control methods hand-pulling, cutting, bulldozing) 

or chemical applications are effective in controlling smaller 

sites, but can be expensive and/or labor intensive 

• Biological control methods are being developed but due to the 

longevity of the plant are likely to only be useful in the long 

term.
83

HIGH-PRIORITY

AQUATIC NUISANCE SPECIES 

NOT YET IN IDAHO 

These species are defined as not currently present in Idaho, and likely to have a high 

adverse impact. 

Zebra mussel Dreissena polymorpha 

Ecology: Zebra mussel are freshwater, bivalve mollusk that typically have a dark and 

white (zebra-like) pattern on their shells. However, color patterns can vary to the point of 

having only dark or light colored shells and no stripes. They are usually about an inch 

long or less, and attach to hard substrates much like marine mussels but unlike any native 

freshwater bivalve. They are prolific, often found in colonies with some colonies 

reported to be over 700,000 individuals per square meter in some locations in the Great 

Lakes. They produce microscopic larvae (veligers) that float freely in the water column, 

passing through screens installed to exclude them. Females generally reproduce in their 

second year by expelling eggs, which are fertilized outside the body by the males; this 

process usually occurs in the spring or summer, depending on water temperature. 

Optimal temperature for spawning is 14-16° C. Over 40,000 eggs can be laid in a 

reproductive cycle and up to one million in a spawning season. In thermally polluted 

areas, reproduction can occur continually through the year. After the eggs are fertilized, 

the veligers emerge within 3 to 5 days and are free-swimming for up to a month. Optimal 

temperature for larval development is 20-22° C. Dispersal of larvae is normally passive 

with the flow. The larvae begin their juvenile stage by settling to the bottom where they 

crawl about by means of a foot, searching for suitable substrate. They then attach 

themselves by means of a byssus, an organ outside the body near the foot consisting of 

many threads. The vast majority of veliger mortality (99%) occurs at this stage due to 

settlement onto unsuitable substrates. Sensitivity to changes in temperature and oxygen 

are also greatest at this stage. Once attached, the life span of zebra mussel ranges from 3-

9 years. Maximum growth rates can reach 1.5-2.0 cm/year. Adults are sexually mature 

at 8-9 mm in shell length i.e. within one year. 

Zebra mussel have some well-defined but broad environmental limitations. The optimal 

temperature range for adults extends to 20-25°

 C, but they can persist for a short term in 

temperatures up to 35° C. Zebra mussel are described as poor oxygen regulators, possibly 

explaining their low success rate in colonizing eutrophic lakes. They can tolerate slight 

salinity (up to 4 ‰). They require calcium concentrations of 10 mg Ca/l to initiate shell 

growth and 25 mg Ca/l to maintain it. Optimal larval survival occurs at a pH of 8.4, and 

optimal adult growth occurs at pH 7.4-8.0. 

They adhere to almost any surface, including the shells of native mussels and turtles, 

rocks, macrophytes, artificial surfaces (cement, steel, rope, pilings, etc.), crayfish, 

unionid clams, and each other. Factors exist, however, that cause the substrate to be 

unsuitable for both initial and long term colonization, including extensive siltation, some 

sessile benthic macroinvertebrates, macroalgae, and fluctuating water levels. Spatial 

patterns of pelagic veliger density and benthic adult dispersion within a lake are 
84

controlled by physical conditions including wind strength, lake/shore morphometry, and 

current patterns. 

 

Monitoring and control of zebra mussel costs millions of dollars annually. Zebra mussel 

are known for their biofouling capabilities by colonizing water supply pipes of 

hydroelectric and nuclear power plants, public water supply plants, and industrial 

facilities. They typically constrict flow in pipes by two-thirds or more and reduce the 

intake in heat exchangers, condensers, fire fighting equipment, and air conditioning and 

cooling systems. Although there is little information on zebra mussel affecting irrigation, 

farms and golf courses could be likely candidates for infestations. Navigational and 

recreational boating can be affected by increased drag due to attached mussels and 

fouling of cooling systems. Navigational buoys have been sunk under the weight of 

attached zebra mussel. Deterioration of dock pilings has increased when they are 

encrusted with zebra mussel which corrode steel and concrete, affecting its structural 

integrity. 

Zebra mussel negatively impact aquatic ecosystems, harming native organisms including 

already imperiled indigenous mussels. In huge numbers, they out-compete other filter 

feeders. Lakes infested with zebra mussel have experienced decreases in phytoplankton 

and zooplankton biomass of 70-90%, leading to increased water clarity and greater 

penetration of sunlight, altering water temperature and thermoclines. As phytoplankton 

are consumed, levels of dissolved organic carbon decrease. Increased light penetration 

may promote macrophyte populations. As macrophytes can be colonized by veligers, the 

macrophyte community may be altered if such colonization proves detrimental. 

Moreover, there is some evidence that pollutants are concentrated in zebra mussel feces, 

possibly affecting other trophic levels. 

Effects may continue through the food web. Reduction in zooplankton biomass may 

cause increased competition, decreased survival and decreased biomass of planktivorous 

fish. Alternatively, because microzooplankton are more heavily impacted by zebra 

mussel, the larval fish population may be more greatly affected than later life stages. In 

addition, proliferation of macrophytes may alter fish habitat. Other effects include the 

extirpation of native unionid clams through crowding. Many species of birds are known 

to be predators of zebra mussel, and while a new food source may benefit such predators, 

biomagnification of toxins into both fish and birds is another potential risk. 

Distribution: Zebra mussel are native to the Black, Caspian, and Azov seas. By the late 

18th and early 19th centuries, zebra mussel had spread to most major drainages of Europe 

through widespread construction of canal systems. Zebra mussel were first discovered in 

North America in 1988 in the Great Lakes. It is suspected that zebra mussel were 

transported in ballast water tanks of commercial ships. 

By 1990, zebra mussel had been found in all the Great Lakes. By the following year, 

they had spread throughout the Illinois and Hudson rivers and the Mississippi River 

drainage. By 1994, 19 states east of the Rockies had reported records of zebra mussel 

within their borders or in water bodies adjacent to their borders. During the summer of 
85

2003, zebra mussel veligers were collected in the Missouri River where it borders 

Nebraska and South Dakota. 

Pathways of Introduction: The rapid invasion of North American waterways has been 

facilitated by the zebra mussel's ability to disperse during all life stages. Passive drift of 

large numbers of pelagic larval veligers allows invasion downstream. Yearlings are able 

to detach and drift for short distances. Both veligers and yearlings can be carried in 

ballast water, bait buckets, or any other water reservoir. Adults routinely attach to boat 

and floating objects and are transported to new locations. Under cool, humid conditions, 

zebra mussel can stay alive for several days out of water. At one time, they were being 

promoted as biofilters for aquariums. In addition, speculation exists that waterfowl can 

disperse zebra mussel, but this has yet to be proven. 

Management considerations: A number of approaches have been taken to controlling 

zebra mussel infestations, with varying success. With the exception of molluscicides, 

most are mitigation methods that do not eliminate infestations. Of course, not all of them 

are suitable or practical for all situations: 

• Chemical molluscicides: oxidizing (chlorine, chlorine dioxide) and non-oxidizing 

• Manual removal (pigging, high pressure wash) 

• Dewatering/desiccation (freezing, heated air) 

• Thermal (steam injection, hot water) 

• Acoustical vibration 

• Electrical current 

• Filters, screens 

• Coatings: toxic (copper, zinc) and non-toxic (silicone-based) 

• Toxic constructed piping (copper, brass, galvanized metals) 

• CO2 injection 

• Ultraviolet light 

• Anoxia/hypoxia 

• Flushing 

• Biological (predators, parasites, diseases) 
86
87

Quagga mussel Dreissena bugensis 

Ecology: The quagga mussel is a freshwater bivalve mollusk up to 1.5 inches in size, 

slightly larger than a zebra mussel. Color patterns in the quagga mussel vary widely with 

black, cream, or white bands, ranging to a nearly uniform whitish coloration. The quagga 

mussel has a rounded angle, or carina, between the ventral and dorsal surfaces. It also has 

a convex ventral side that can be distinguished from a zebra mussel by placing shells on 

their ventral side; a quagga mussel will topple over, whereas a zebra mussel will not. If 

quagga mussel are viewed from the front or from the ventral side, the valves are clearly 

asymmetrical. 

Quagga mussel are prodigious water filterers, removing substantial amounts of 

phytoplankton and suspended particulate from the water. As such, their impacts are 

similar to those of the zebra mussel. By removing the phytoplankton, they decrease the 

food source for zooplankton, therefore altering the food web. Impacts associated with the 

filtration of water include increases in water transparency, decreases in mean chlorophyll 

a concentrations, and accumulation of feces. Water clarity increases light penetration, 

sometimes causing an increase in aquatic plants that can change species dominance and 

alter the ecosystem. The feces that are produced from filtering the water accumulate and 

create a foul environment. As the waste particles decompose, oxygen deficits occur, the 

pH becomes very acidic, and toxic byproducts are produced. In addition, quagga mussel 

accumulate organic pollutants within their tissues to levels more than 300,000 times 

greater than concentrations in the environment and these pollutants are found in their 

feces, which can be passed up the food chain, therefore increasing wildlife exposure to 

organic pollutants. 

Like zebra mussel, quagga mussel will clog water intake structures and reduce pumping 

capabilities for power and water treatment plants, costing industries, companies, and 

communities millions of dollars in treatment costs. Quagga mussel have a greater 

tolerance for cooler water temperatures than zebra mussel, and have been found to 

colonize substrates at greater water depths. Recreation-based industries and activities 

have also been impacted. Docks, break walls, buoys, boats, and beaches have all been 

heavily colonized on both hard and soft substrates. It is clear that the genus Dreissena is 

highly polymorphic and has a high potential for rapid adaptation to extreme 

environmental conditions, possibly leading to significant long-term impacts on North 

American waters. 

In the 1990's, the absence of quagga mussel from areas where zebra mussel were present 

may have been related to the later timing and location of introduction, rather than 

physiological tolerances. If the native habitat of quagga mussel provides any sort of 

indicator, the quagga mussel will most likely colonize areas where the zebra mussel is 

now established to become the dominant dreissenid of the Great Lakes. Indeed, this trend 

does appear to be occurring in the lower Great Lakes. Mean shell size and biomass 

increased for both dreissenid species from 1992 to 1995 in southern Lake Ontario, but the 

increase was sharper in quagga mussel, and they now dominate in southern Lake Ontario 

instead of zebra mussel. 
88

Distribution: Quagga mussel are indigenous to the Dneiper River drainage of Ukraine. 

It was first documented in the Great Lakes in September 1989, and after confirmation 

that this mussel was not a variety of zebra mussel, the new species was named "quagga 

mussel" after the quagga, an extinct African relative of the zebra. 

Quagga mussel are currently distributed throughout most of the Great Lakes – Saint 

Lawrence system, and there are also a few inland occurrences in New York, Ohio, 

Michigan, and Pennsylvania. They were reported in Missouri and Illinois in 1995. More 

recently, in January 2007, populations of quagga mussel were discovered in Lake Mead 

on the lower Colorado River and may possibly be in Lake Powell in Utah. 

Pathways of Introduction: The introduction of quagga mussel into the Great Lakes 

appears to be the result of ballast water discharge from transoceanic ships that were 

carrying veligers, juveniles, or adult mussels.. Like zebra mussel, there are other factors 

that can also aid in the spread of quagga across North American waters, such as larval 

drift in river systems, and fishing and boating activities that allow for overland transport 

or movement between water basins. 

Management considerations: Chlorination has been the most common treatment for 

control. Another alternative has been potassium permanganate, especially for drinking 

water sources. Other methods of control include: oxygen deprivation, thermal treatment, 

exposure and desiccation, radiation, manual scraping, high-pressure wash, mechanical 

filtration, removable substrates, molluscicides, ozone, antifouling coatings, electric 

currents, and sonic vibration. Some industries even built their intake structures and piping 

at depths too low for zebra mussel colonization; however, when the quagga mussel were 

discovered at lower water depths these new structures became vulnerable to quagga 

colonization. Biological control so far has proven to be ineffective in controlling 

Dreissena species. Predation by migrating diving ducks, fish species, and crayfish may 

reduce mussel abundance, though the effects appear to be short-lived. A proposed 

approach to controlling Dreissena populations may be to disrupt the reproductive 

process, by interfering with the synchronization of spawning by males and females in 

their release of gametes. Another approach would be to inhibit the planktonic veliger 

from settling, since this is the most vulnerable stage in the life cycle. 
89
90

Asian carp, Including:

Black carp Mylopharyngodon piceus

Silver carp Hypophthalmichthys molitrix

Bighead carp Hypophthalmichthys nobilis

Grass carp Ctenopharyngodon idella

Asian carp hybrids H. molitrix x nobilis, C. idella x H. idella x nobilis

Ecology: Typical habitat for these carp species includes quiet waters, such as lakes, 

ponds, pools, and backwaters of large rivers, and a range of water depths. They are 

generally considered a nuisance because they prey on native species and/or compete with 

them for food and habitat. In addition, carp may carry several parasites and diseases 

known to be transmissible or potentially transmissible to native fishes. 

The black carp is a bottom-dwelling molluscivore that has been used by fish farmers in 

the South to prey on and control disease-carrying snails in their farm ponds. Black carp 

are superficially very similar in appearance to grass carp, leading to a risk that the species 

be misidentified and unintentionally introduced as "grass carp" to some areas. There is 

high potential that the black carp would negatively impact native aquatic communities by 

feeding on, and reducing, populations of native mussels and snails, many of which are 

considered endangered or threatened. 

The silver carp is a filter-feeder capable of consuming large amounts of phytoplankton. 

Its diet also includes zooplankton, bacteria, and detritus. It has the potential to cause 

enormous damage to native species because it feeds on plankton required by larval fish 

and native mussels. This species would also be a potential competitor with adults of some 

native fishes that also rely on plankton for food. 

Similar to the closely-related silver carp, the bighead carp is a filter feeder that prefers 

large river habitats. Because bighead carp are planktivorous and attain a large size, they 

have the potential to deplete zooplankton populations, leading to reductions in 

populations of native species that rely on plankton for food including all larval fishes, 

some adult fishes, and native mussels. 

Grass carp, which are herbivores, seem to affect other animal species by modifying 

preferred habitat; however, they may directly influence other animals through either 

predation or competition when plant food is scarce. These influences include interspecific 

competition for food with invertebrates and other fishes, significant changes in the 

composition of macrophyte, phytoplankton, and invertebrate communities, interference 

with the reproduction of other fishes, and decreases in refugia for other fishes. Increased 

phytoplankton populations are often a secondary effect of grass carp presence: a grass 

carp can digest only about half of the plant material that it consumes each day, expelling 

the rest into the water where it promotes algal blooms. These blooms can reduce water 

clarity and decrease oxygen levels. A sterile variety (triploid) of grass carp is approved 
91

for use in Idaho in isolated ponds. All such fish imported into Idaho must be certified as 

triploid and be free of specific diseases. 

Silver/bighead carp hybrids have been reported in a number of locations in the United 

States. The hybrid fish can be intermediate or externally indistinguishable from either 

parent species and are documented to be fertile. Grass/bighead carp hybrids have been 

reported in Florida, Texas, California and Arizona, where it was intentionally stocked. It 

is believed to be sterile. Both of these hybrids exhibit similar behavior and impact their 

habitat in similar ways to their parent species. 

Distribution: : Fertile grass carp have been documented in Idaho in only a limited 

area, in the Snake River between King Hill and Shoshone Falls in the early 1980s. These 

fish were escapes from unscreened waters where they introduced to control vegetation. 

With the establishment of restrictions on their importation and use in Idaho in the mid 

1980s, they have disappeared from the Snake River and currently there are no known 

reproducing populations in Idaho. However, the species has a tolerance for a wide range 

of temperatures, which makes it a likely candidate to establish in some water bodies in 

the state if illegally released. The other three species of Asian carp and the known 

hybrids have not been reported in Idaho to date, but are reported to be established in 

many other areas of the United States, particularly the Mississippi River drainage and in 

the South. 

Pathways of Introduction: These four carp species were introduced in the United 

States in the 1970s as food fish and/or as biological control agents in aquaculture ponds 

or eutrophic water bodies. Some were illegally stocked in ponds or commercial fish 

farms. In many cases, they made their initial escape during episodes of flooding or 

through accidental release from a farm or aquaculture facility. 

The possibility of deliberate transportation and release of these species is a likely 

occurrence. Asian carp have been discovered in public ponds and lagoons in the Great 

Lakes region, and media stories indicate that these fish are being intentionally released as 

part of religious ceremonies. . 

Management considerations: Asian carp species are so widely established in the United 

States that eradication is impossible and control is unlikely. A regulatory approach of 

identifying legal responsibility and developing consistent regulations will be needed on a 

regional basis to prevent intentional or unintentional release of invasive species including 

Asian carp. Several of the Asian carp species have or are being added to the USFWS 

injurious species list. 
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Rusty crayfish Orconectes rusticus

Ecology: The rusty crayfish is a dark-colored crustacean reaching about 4 inches in 

length, with large, robust claws and sometimes with “rusty” spots on the sides of its 

carapace. It is native to the Ohio, Tennessee, and Cumberland drainages. Rusty crayfish 

inhabit lakes, ponds, and streams. They prefer areas that offer rocks, logs, or other debris 

as cover. Bottom types may be clay, silt, sand, gravel, or rock. Rusty crayfish inhabit 

both pools and fast water areas of streams. They generally do not dig burrows other than 

small pockets under rocks and other debris, although there have been reports of more 

substantial burrows. Rusty crayfish need permanent lakes or streams that provide 

suitable water quality year-round. 

Mature rusty crayfish mate in late summer, early fall, or early spring. The male transfers 

sperm to the female, which she then stores until her eggs are ready to fertilize, typically 

when water temperatures begin to increase. The stored sperm are released as the eggs are 

expelled, and external fertilization occurs. The eggs are then attached to the swimmerets 

on the underside of the crayfish's abdomen. Rusty crayfish females lay from 80 to 575 

eggs. The eggs hatch in three to six weeks, depending on water temperature. Once 

hatched, young crayfish cling to the female's swimmerets for three to four molts, usually 

a period of several weeks. The young undergo eight to ten molts before they mature, 

which may occur during the first year, but more likely the following year. Rusty crayfish 

reach maturity at a total length of one and three-eighths inches and reach a maximum 

length of about four inches (not including claws). A typical rusty crayfish lives three to 

four years. 

Invading rusty crayfish frequently displace native crayfish, reduce the amount and kinds 

of aquatic plants and invertebrates, and reduce some fish populations. Perhaps the most 

serious impact is the destruction of aquatic plant beds that rusty crayfish causes. These 

aquatic plants are important for habitat for invertebrates, food for fish and ducks, shelter 

for young game fish or forage species of fish, nesting substrate for fish, and erosion 

control (by minimizing waves). Although other crayfish eat aquatic plants, rusty crayfish 

eat about twice as much because they have a higher metabolic rate. Rusty crayfish, 

especially juveniles, also feed heavily on benthic invertebrates such as mayflies, 

stoneflies, midges, and side-swimmers. Thus they are more likely to compete with 

juvenile game fish and forage species for invertebrates than are native crayfish species. 

Distribution: In the 1990s rusty crayfish were spread, probably through bait bucket 

transfers, to several states in northeastern and north-central US and to New Mexico. 

To date, they have not been reported in Idaho waters. 

Pathways of Introduction: Anglers using crayfish as bait are thought to be the primary 

cause of introduction. Developing a viable commercial harvest of rusty crayfish from 

natural lakes could be an incentive for unscrupulous trappers to plant them in other 

waters. 

Rusty crayfish are also sold to schools by biological supply houses. Even though a 

warning not to release them into the wild accompanies crayfish sold to schools, such 
96

warnings may not be effective, as live crayfish may be given away to students and may 

eventually be released into the wild. 

Management considerations: It is important to note that it is not necessary to have 

both a male and a female crayfish to begin a new infestation. One female carrying viable 

sperm could begin a new population if released into a suitable environment. Rusty 

crayfish readily mate in captivity so it is reasonable to expect that mature females, 

whether used as fishing bait or as science class study specimens, could produce offspring. 

Currently the only method of control is to prevent their introduction. Educating anglers, 

crayfish trappers, bait dealers, and teachers about the threats posed by rusty crayfish will 

help reduce the risk of spreading it to new areas. Environmentally-sound ways to 

eradicate or control introduced populations of rusty crayfish have not been developed. 
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Round goby Neogobius melanostomus

Ecology: Native to the Black Sea, Caspian Sea, and Sea of Azov, this small (about 7 in 

max) fish has prominent eyes and a grey body with black and brown blotches. They can 

become established in lakes, ponds, rivers, creeks, and canals. The diet of round gobies 

collected in the United States consists of aquatic insects, zebra mussel, and some native 

snails. Studies have shown a single goby can eat as many as 78 zebra mussels per day. 

Given the proliferation of zebra mussel in the Great Lakes system, and the fact that no 

other fish species feeds on the zebra mussel as heavily, the goby population is apparently 

undergoing a population explosion in that area. Trawls in the Great Lakes in the mid-90s 

collected thousands of gobies, and densities in one location exceeded 20 individuals per 

square meter. They have been found in a range of habitats, from near-shore rocky or 

weedy areas to about 20m water depth. 

Round gobies are aggressive feeders and will eat other small fish or each other, as well as 

the eggs and fry of many larger species including several popular game fish. Native fish 

species have declined in locations where round gobies have become abundant. They are 

also aggressive about seizing and defending optimal spawning sites and daytime refugia 

from native fishes, driving them out to where they can be preyed upon. Round gobies 

undergo a long spawning period during which individuals can spawn every 20 days, 

while they aggressively defend their nests. Moreover, round goby fry compete with the 

fry of some native species for food, due to the overlap of an arthropod diet at this age. 

Distribution: Since 1990, round gobies have become established in many locations in 

the Great Lakes and in parts of the Saint Lawrence River system. 

Pathways of Introduction: The round goby was introduced into the Great Lakes about 

1990 by freighter ballast from Eurasia, and has been spread throughout the Great Lakes 

system by boats and freighter ballast. The potential for spread to Idaho is primarily in 

illegal shipments of live fish. 

Management considerations: No biological control agents are known at this time and 

chemical control would be economically restricted to smaller waters; the best 

management policy is to prevent the spread of this species. 
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Ruffe Gymnocephalus cernuus 

Ecology: The ruffe is a small (4 to 6 inch) freshwater fish, olive-brown to golden-brown 

on its back, with yellowish-white undersides. It is native to northern Europe and Asia 

and lives in lakes, rivers, streams and ponds. Spawning takes place in the spring. The 

diet of ruffe changes throughout the course of development, becoming more benthic with 

increasing size. Copepods, typify the diet of larval ruffe. The bottom-dwelling larvae of 

other insects, mainly mayflies and stoneflies, become increasingly important in the diet of 

ruffe as they grow. 

Ruffe exhibit rapid growth and high reproductive rates and are able to adapt to a wide 

range of habitat types, posing a threat to native North American fish. In the Great Lakes 

system, there is concern that ruffe may have a detrimental effect on more desirable 

species such as yellow perch and walleye, by feeding on the young of these species 

and/or by competing for food. Ruffe prey heavily on benthic insects, the primary food 

source for native benthic-feeding fishes. In the Great Lakes, ruffe hold an advantage over 

native yellow perch in their greater ability to select moving objects under relatively dim 

light conditions or in high turbidity. Further, it has been found that native pike, bass, 

bullhead, walleye and perch prefer feeding upon native fish species rather than ruffe. 

Distribution: Eurasian ruffe has been established in the western Great Lakes since about 

1988 and has become the dominant species in some areas. It has been reported in 

Wisconsin, Michigan, and Minnesota, and Ontario, Canada, and continues to spread 

eastward. Its potential habitat would include the lakes and rivers of Idaho. 

Pathways of Introduction: The ruffe was probably introduced via ship ballast water 

discharged from a vessel arriving from a Eurasian port, possibly as early as 1982-1983. 

Within the Great Lakes, the species spread may have been augmented by intra-lake 

shipping transport. The potential for spread to Idaho is primarily in illegal shipments of 

live fish. 

Management considerations: No biological control agents are known at this time and 

chemical control would be economically restricted to smaller waters; the best 

management policy is to prevent the spread of this species. Some native fishes feed on 

ruffe but they are not preferred, and populations control by native fishes is unlikely. 
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Amur goby Rhinogobius brunneus

Ecology: The Amur goby is a small (4 in) fish native to Japan, the Russian Far East, 

Taiwan, Korea, China and the Philippines. They have fused pelvic fins, which form a 

suction-cup structure on the chest of the fish; a red or dark line running from the front 

edge of the eye to the tip of its snout; and breeding males are red or blue with colorful 

fins. 

Many goby species are distinguished primarily by body coloration, but they also often 

occupy different habitat types within the same stream, and are collectively referred to as 

the Amur goby species complex. Species in this complex have different life histories and 

egg sizes. At this time, the taxonomy of this species complex is not resolved. Therefore, 

it is not clear whether the type(s) introduced to the US constitute one or more species of 

Rhinogobius, so it is prudent that all species of goby be prohibited in Idaho. 

While some species in the Rhinogobius species complex are landlocked, others have an 

amphidromous life history, spending portions of their lives in both fresh and saline 

waters. In the spring, males construct nests under stones and entice females to spawn. 

After spawning, males defend and care for the eggs. Larvae hatch and drift downstream 

to the sea where they feed and grow. Larval drift occurs nocturnally, and the larvae halt 

their migration in pools with low flow rates during the day. After a few months in marine 

waters, juveniles migrate upstream into freshwater for further growth and reproduction. 

At this time, the impact of this fish on native species is not known, but it is likely that it 

will compete for resources with native fishes. 

Distribution: This species has spread from its native Asia elsewhere in the world via 

shipping. Amur goby was discovered in the Lewis River in western Washington in 2004, 

and is reported to be spawning there. Since that time, another specimen was collected 

from the Columbia River (River Mile 54) at Crims Island. 

Pathways of Introduction: Its initial introduction into North America was probably in 

ballast water, though it may have been the aquarium trade. It could be transported 

elsewhere in the US by similar means. 

Management considerations: No biological control agents are known at this time and 

chemical control would be economically restricted to smaller waters; the best 

management policy is to prevent the spread of this species. 
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Spiny water flea Bythotrephes longimanus, formerly B. cederstroemii

Ecology: Bythotrephes longimanus is a large (15 mm) cladoceran distinguished by a 

long straight tail spine that is twice as long as its body and has one to three pairs of 

barbs. Parthenogenically produced animals have a kink in middle of their spine and 

sexually produced animals lack the kink. The spiny water flea is native to Northern 

Europe and Asia. 

Bythotrephes are found among the zooplankton in the upper water column of temperate 

lakes, can tolerate brackish water, and are most abundant in late summer and autumn. 

Occurrence and density of Bythotrephes populations are apparently determined mainly by 

water temperature and salinity. Within both its native and its introduced range, it appears 

to prefer large, deep, clear lakes with relatively low summer bottom temperatures, which 

is characteristic of many Idaho lakes. Bythotrephes is limited to regions where water 

temperature ranges between 4 and 30°C and salinity values up to 8.0‰, but prefers 

temperatures between 10 and 24°C and salinity values between 0.04 and 0.4‰. 

Temperature appears to be the major factor in determining the abundance and location of 

Bythotrephes in the Great Lakes. Bythotrephes can reproduce asexually as well as 

sexually; unfertilized eggs are carried in a brood pouch, and fertilized eggs are cast in the 

fall, hatching the following spring. 

The first noticeable impact of Bythotrephes was on anglers. The tail spines of 

Bythotrephes hook on fishing lines, fouling fishing gear. The invasion of B. longimanus

into the Great Lakes has resulted in substantial and sustained decreases in the populations 

of a number of native zooplankton species. Bythotrephes consume small cladocerans, 

copepods, and rotifers, thus competing directly with planktivorous larval fish for food. 

They have been implicated as a factor in the decline of alewife Alosa pseudoharengus. 

Bythotrephes are used as a food source by some fish species. 

Distribution: Bythotrephes was first reported in December 1984 in Lake Huron, and had 

spread to the other four Great Lakes by August 1987. They are now established 

throughout the Great Lakes and many inland lakes in the region, although their densities 

vary widely by location. More recently they have been collected from lakes and 

reservoirs in Minnesota, Michigan, and New York. 

Pathways of Introduction: Bythotrephes were probably first introduced from ships 

ballast water. Spiny water flea eggs and adults spread unseen in bilge water, bait buckets, 

and livewells. In addition, boat hulls, fishing gear, fishing lines and downriggers will 

often be coated with both eggs and adults. 

Management considerations: As anglers and recreational boaters are a primary means 

of transport for the spiny water flea, public education should form a central part of 

control efforts. Personal management practices for boaters and anglers include cleaning 

of boating equipment with high-pressure water or heated water at temperatures of 104oF 

or higher. Bait buckets should not be emptied into natural waters; they should be emptied 

on land. Visual inspection of rigging, fishing, and anchor lines as well as the props and 

hulls of boats can help limit the spread of B. longimanus. Boats should be allowed to dry 
104

for at least 5 days before transport between lakes, but because of B. longimanus resting 

eggs, longer periods are recommended. Boats and trailers should be towed through 

carwashes if exposed to infected waters for long time periods. 
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Snakehead fish, including:

Northern snakehead Channa argus

Bullseye snakehead Channa marulius

Ecology: The snakehead group of species originates in eastern and southeastern Asia 

where they are valued as food for human consumption. They inhabit freshwater lakes, 

watercourses, or wetlands, mostly preferring deep, slow-moving or standing water with 

rocky or sandy substrates. They are all voracious predators with no natural enemies, and 

would severely impact native fishes, crustaceans, insects, amphibians, birds and small 

mammals living near the water’s edge. Snakeheads are obligate air breathers and can 

survive out of water for up to four days. They range from less than 1 ft. to 3.5 ft. long 

and weigh up to 45 lbs, although the bullseye snakehead can reach 6 ft. in length and 

about 65 lbs. 

Snakeheads spawn from 1 to 5 times during the warmest months of the year, the brood 

size consisting of anywhere from several hundred to several thousand pale yellow-red 

eggs. These eggs may float in a nest of weeds and leaves, or simply float in the water 

column, for one or two days until the yolks are absorbed and the eggs hatch. The number 

of broods per year and the rate at which they hatch depends on water temperature. The 

eggs are ferociously guarded by the parents who will attack anyone or anything 

approaching the nest, including humans. 

The fry feed initially on zooplankton, and later on insect and fish larvae and small 

crustaceans. Adults prefer fish but will eat frogs, crustaceans, small reptiles, birds, and 

mammals. They remain close to shore, typically under aquatic vegetation, and are most 

active at dusk and dawn, feeding very near the shore. 

The northern snakehead prefers stagnant shallow ponds, swamps and slow streams with 

mud or vegetated substrate, with temperatures ranging from 0 to >30o

C. It has a wider 

latitudinal range and temperature tolerance than other snakehead species. It also seems to 

be adaptable to a wide range of aquatic environments, indicating that it has the potential 

to invade many water bodies in Idaho and elsewhere in the US. 

Two additional species of snakehead, the blotched C. maculate and giant C micropeltes

are tropical species and unlikely to establish in Idaho except in a few larger geothermal 

waters. 

Distribution: 

Northern snakehead: Collected in California and Massachusetts. Reported in Florida but 

status uncertain. Eradicated where it was established in a pond in Maryland. Believed to 

be established in the Potomac River. Status of a Philadelphia location is uncertain, 

although officials believe the fish may have gotten into the lower Schuylkill and 

Delaware Rivers and see no practical means to eradicate them. 

Bullseye snakehead: Locally established in Florida; reported in Maryland. 

Pathways of Introduction: Probably originally introduced to the United States in the 

Asian food trade at various times in the 19th and 20th centuries, and deliberately stocked 
106

in local ponds. These fish are available, though rare, in the aquarium trade, and isolated 

reports of individual specimens are likely deliberate aquarium releases. Human 

transportation is the most likely means of introduction to new areas. They can also 

spread by moving through river and stream networks. 

Management considerations: The ability to eradicate or control snakehead populations 

depends on where they are found, but in most cases, the prevention of introduction is the 

only effective means of control. If established in large lakes or river systems, eradication 

and/or control are virtually impossible. Control in smaller water bodies depends upon the 

amount of vegetation and the accessibility of the water body. Moreover, there is some 

disagreement about the effectiveness of piscicides on air-breathing snakeheads. 
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Nutria Myocastor coypus

Ecology: The nutria is a large semi-aquatic rodent native to South America. The only 

known mammalian ANS, nutria are found in and around fresh and saltwater ponds, 

streams, and swamps, and are rarely observed over 100 m away from water. Presently, 

they are considered to be a pest species, disrupting irrigation systems, destroying native 

aquatic vegetation, and crops. Additionally, by disturbing the balance of the native biota 

they provide an advantage for non-native plant species to become established. Their 

burrows undermine and damage river banks, dikes and irrigation facilities. By eating the 

young shoots of reeds and their rhizomes, the nutria can completely clear marshland 

communities, converting them into open water areas. It threatens the habitat and survival 

of rare marsh birds, such as bitterns and marsh harriers. Infestation by this animal would 

have very serious consequences for riparian communities statewide. 

Distribution: Since their introduction to North America, some animals have escaped 

and established localized breeding populations from Texas to Virginia, Washington and 

Oregon, and in the Great Lakes area. There has been only one report to date of nutria in 

Idaho, in an unspecified location, in 1991. Populations in western Oregon and 

Washington have been increasing resulting in negative impacts to wetlands. 

Pathways of Introduction: Nutrias were initially introduced into North America and 

farmed for their fur. However, due to escapes from fur farms there are now large feral 

populations in North America, Europe and Asia. 

Management considerations: Management of nutria includes shooting and trapping. 

There is a significant relationship between winter severity and female reproduction in the 

following spring, with prenatal embryo losses common during cold winter and in females 

in poor health condition. Likelihood of establishment in Idaho is low due to cold winters 

but in some lower elevations in the Snake drainage it is feasible. 
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Viral hemorrhagic septicemia 

Ecology: Viral hemorrhagic septicemia (VHS) is a viral fish disease affecting most 

salmonid and a few non-salmonid species. It has caused large scale mortalities in 

rainbow trout and turbot aquaculture operations in Europe and in Pacific herring and 

pilchard populations along the Pacific Coast of North America. The disease is caused by 

a rhabdovirus known as Viral Hemorrhagic Septicemia Virus. There are currently five 

known strains of VHS in Europe, Japan, and North America. The virus infection occurs 

in fishes of any age and may result in significant cumulative mortality. Fish that survive 

may become carriers. The strain in the Great Lakes is a more virulent strain than the one 

on the Pacific Coast. 

A variety of clinical signs and histopathologic changes may be apparent in fish infected 

with VHS virus. Not all fish show clear clinical manifestations of disease. Historically, 

clinical and pathologic signs of VHS have been catalogued into acute, chronic, and latent 

forms. Acute signs are typically accompanied by a rapid onset of heavy mortality. In the 

acute form of the disease, fish become lethargic, dark and anemic, with bulging eyes, 

congested kidneys, and mottled liver. Hemorrhages are evident in the eyes, skin, and 

gills and at the bases of the fins. In the chronic form of the disease, mortality is low and 

all the symptoms are similar to the acute form, except that hemorrhaging is not common; 

instead, the liver, spleen and kidneys experience an accumulation of fluid such that the 

body becomes bloated and the liver and kidneys become very light in color. In the latent 

manifestation of the disease, some mortality may occur and fish become hyperactive, 

sometimes displaying nervous symptoms such as twisting of the body and behavior that 

involves swimming erratically in circles or in a corkscrew pattern. Conversely, some 

carriers of the virus may show no symptoms at all. 

VHSv can be transmitted by fish urine, feces and sexual fluids. The virus can be found 

on the surface of salmonid eggs during spawning of infected female broodstock 

(sometimes at very high levels) and is capable of persisting for a sufficient time to result 

in egg-associated transmission between generations (adult to progeny). It is also likely to 

enter the body through the gills or through wounds. Experiments showed that blood 

sucking parasitic arthropods and leeches can transmit the infection physically. In the 

western United States, salmon eggs are routinely surface disinfected with an iodine 

compound at or after water hardening to eliminate vertical (parent to egg) VHSv 

transmission. 

VHSv is not a human pathogen. There are no concerns with respect to human health with 

this pathogen and it can not infect humans if they eat fish with the pathogen. However, it 

is a reportable animal disease that requires notification of APHIS, the Canadian Food 

Inspection Agency, and the International Organization for Animal Health. 

APHIS issued a Federal Order on 24 October 2006, amended on 14 November 2006, to 

take emergency action to prevent the spread of VHS. According to this Federal Order, 

VHS-susceptible species are prohibited from moving out of the states and Canadian 

provinces bordering the Great Lakes except for: 

• Movement to slaughter with adequate disinfection 
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• Movement to a research or diagnostic lab with adequate disinfection 

• Movement of live fish testing negative for VHS virus by laboratory assays 

• Movement of salmonids from Canada that meet Title 50 requirements 

Distribution: VHS has been reported in the northeastern Pacific Ocean, the northern 

Atlantic, and the Baltic Sea. In North America, outbreaks have occurred in lakes Ontario, 

Erie, and Huron, the Saint Lawrence River, and along the western coast from Alaska to 

San Francisco. It has affected the Columbia River system as far inland as the Sandy 

River in Oregon, and has occurred in at least one of the Finger Lakes in upstate New 

York. 

Pathways of Introduction: VHS was first isolated in Denmark in 1963. The earliest 

confirmed report in the US was in 2003 in a Great Lakes muskellunge from Lake St. 

Clair, so it is likely to have been introduced here in 2002 or 2003. It is not known exactly 

how this virus arrived in the Great Lakes, but ballast water discharge is considered as a 

likely vector given its pattern of distribution in the lakes. 

Live, water-borne virus can move downstream 10-20 km. Fish-eating birds (especially 

herons) can act as mechanical vectors from one aquaculture facility to another. Transfer 

of infected fish in the incubation phase (before onset of visible signs) or of infected 

transport water is another well-known route of infection. Import or interstate transfer of 

potentially infected fish is also a possible avenue for the spread of VHS. 

Management considerations: There is currently no effective treatment for VHS, so 

prevention is paramount. APHIS must develop a rule to replace the temporary Federal 

Order that will provide for specific testing requirements and develop criteria for United 

States import and interstate transfer of fish. 

All of the recommended ways to prevent the movement of ANS i.e. zebra mussel, will 

help prevent the spread of this pathogen. The use of a bleach solution (1 cup bleach to 10 

gallons water) to disinfect and clean boats, bilges and gear is very effective in killing 

VHSv, as is completely drying items in the sunlight for 4-6 hours. It is also critical not to 

move live fish or water between water bodies, in particular baitfish. These measures will 

help control the spread of this pathogen along with many other ANS. 
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Viral hemorrhagic septicemia
113

Water hyacinth Eichhornia sp.

Ecology: Eichhornia sp. is a free-floating aquatic macrophyte growing to 0.5 m in 

height and often forming dense floating mats. Foliage leaves are petiolate with a glossy 

sheen, and are arranged spirally, appearing to be in a rosette. Flowers are borne 

terminally on a lavender spike on an elongated peduncle and are subtended by two bracts. 

As much as 50% of a single water hyacinth’s biomass can be roots. Roots are 

adventitious and fibrous, 10-300 cm in length. As many as 70 lateral roots per cm give 

the roots a feathery appearance. They are dark violet to bluish or pinkish violet (though 

whitish if grown in total darkness) and contain soluble pigments, including anthocyanins 

that may protect the root from herbivory. There are approximately a half-dozen species 

of Eichhornia including E. azurea, known as the rooted water hyacinth, which is listed on 

the Federal Noxious Weed List. 

Eichhornia sp. grows in shallow ponds, wetlands and marshes, sluggish flowing waters, 

lakes, reservoirs and rivers. Disruptions of wetland ecosystems involving irrigation 

canals, hydroelectric projects and construction of artificial lakes have created areas 

particularly susceptible to invasion by water hyacinth. Growth of water hyacinth is 

largely facilitated by nutrient rich waters, particularly those rich in nitrogen, phosphorus 

and potassium. It grows particularly well in waters in which fish production is also very 

good. Originating from the tropical regions of South America, this plant exhibits frost 

sensitivity and does not tolerate brackish water. 

 

Eichhornia sp. has been spread by humans to all tropical and subtropical regions in the 

world where it forms thick mats that cover rice paddies, clog irrigation channels, impede 

navigation, halt fishing, sweep away buildings during floods and foster breeding of 

disease-transmitting mosquitoes. Doubling in biomass every 6 to 18 days, the exact time 

being dependent on location and time of year, this weed rapidly invades waterways and is 

listed as the most serious aquatic weed in the world. 

Environmental problems associated with the water hyacinth are exacerbated in warm 

areas, where the weed flourishes. It reduces dissolved oxygen levels and light, 

significantly altering ecosystems and plant and animal communities. Low oxygen levels 

kill native fish populations and fish spawning areas may be reduced, as well as critical 

waterfowl habitat degraded. Mats of water hyacinth also deposit large amounts of 

organic matter which increase the organic content of sediments and greatly accelerate 

succession patterns, allowing emergent and riparian vegetation to colonize. 

Eichhornia sp. has a detrimental impact on water use by humans. In drainage and 

irrigation canals it reduces the flow, which can result in flooding and damage to canal 

banks and structures, and clogs intakes of pumps used for irrigation. Water flow patterns 

have been disrupted in utility cooling reservoirs. Water hyacinth interferes with 

navigation of both recreational and commercial craft, negatively impacting anglers, 

water-skiers and swimmers in recreational waters. It also impedes subsistence fishing 

and transportation in developing countries in Africa and Asia. 
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Distribution: Water hyacinth originated in the Amazon basin and the extensive lakes 

and marshes of the Pantanal region of western Brazil. Eichhornia sp. now has a 

worldwide distribution throughout the tropics and occurs on every continent except 

Europe, where it is inhibited by climate. In the United States, water hyacinth is 

widespread throughout the southeastern and south-central portions of the country, in 

California, and in Hawaii. It has not been reported in Idaho, but may exist in thermal 

waters and is likely sold in the aquarium trade. 

Pathways of Introduction: Water hyacinth has an attractive purple flower which has 

made it a favorite amongst ornamental pond and botanical garden enthusiasts. Most 

spread can be attributed to deliberate planting of water hyacinth in ponds or dams as an 

ornamental, or use in aquariums. Unwanted plant material discarded into creeks, rivers 

and dams is a major mode of dispersal. Water hyacinth can be spread, though rarely, by 

contaminated boating and waterway equipment. Stolons, solitary plants and drifting mats 

are readily distributed by water currents, winds and boat traffic. High water flows and 

floods can move infestations to new locations. Additionally, seeds may be carried by 

machinery, on boots, in water flow, mud, and by birds. 

Management considerations: Small scale mechanical or hand removal of water hyacinth 

is widely practiced around the world because of the ease of collecting these floating 

plants. Large scale mechanical harvesting requires expensive equipment, and water 

hyacinths have not been efficiently utilized for cattle feed, energy or other use due to the 

high water content of the plants. Biocontrol agents have been introduced into the United 

States from the native range of water hyacinth (South America) which slow the growth of 

the plant and reduce flowering. The introduced insects are widely distributed over the 

range, but do not usually destroy existing populations. Management of water hyacinth in 

the United States is largely accomplished with herbicides. 
115
116

Hydrilla Hydrilla verticillata

Ecology: Hydrilla is a submersed aquatic perennial with heavily branched stems 

towards the water surface. Stems are slender and can grow up to 9 m long depending 

upon water clarity. Leaves are 6 to 20 mm long and 2 to 4 mm wide. The leaves are 

strap-shaped with pointed tips and saw-tooth edges, and grow in whorls of 4 to 8 around 

the stem. Leaf color can vary from green, translucent, yellowish, to brown. Hydrilla 

produces turions (over-wintering dense vegetative buds) in the axils of leaves and tubers 

within the sediment. Small white flowers on long slender stems near the water’s surface 

are female, and small, green, free-floating, inverted bell-shaped flowers are male. The 

plant is usually rooted to the substrate but sometimes grows as floating mats at the 

water’s surface. 

Hydrilla reproduces mostly by asexual vegetative fragmentation (from stem fragments), 

but it also grows new plants from turions and underground tubers, as well as seeds in 

locations where they are produced. One hydrilla tuber can lead to the production of 

5,000 new tubers per square meter. Tubers and turions can survive ice cover, drying, 

ingestion and regurgitation by waterfowl, and may remain viable in the sediment for 

several years. 

Hydrilla is found in freshwater but can tolerate salinities of up to 7‰. It has been found 

in springs, lakes, marshes, ditches, rivers, and tidal zones. It can grow in relatively low 

light and CO2 conditions. Hydrilla prefers temperatures between 20 and 27 degrees C, 

but tolerates and survives for long periods at 4-5 degrees C. 

Hydrilla competes with native plants by growing to the water surface and forming dense 

surface mats that totally exclude sunlight from other plants, which in turn can 

significantly reduce aquatic plant and animal biodiversity. Large populations hydrilla 

may affect fish size and population levels where predatory fish cannot hunt effectively 

within the thick mats. The dense mats also negatively affect recreational activities. 

Apart from interfering with fishing, boat motors can become tangled with them and 

swimming areas choked. Children have become entangled in hydrilla and drowned. 

Hydrilla often slows or clogs rivers, irrigation ditches, and flood control canals, creating 

stagnant water that is prime mosquito breeding habitat. Dense stands can even cause 

flooding, alter water quality by decreasing oxygen levels and increasing pH and water 

temperature. 

Distribution: Hydrilla is thought to be native to Asia, Africa, and northern Australia. 

The dioecious plant is native to southern India and the monoecious plant is probably 

native to Korea. The dioecious and the monoecious plants are now found on every 

continent except Antarctica. In the US, it is widespread in states along the Gulf coast and 

the eastern seaboard, as well as in numerous locations in California and an isolated 

outbreak in a lake east of Puget Sound. Some of these occurrences have been 

successfully eradicated. Hydrilla populations north of South Carolina are mainly 

monoecious, while southern populations are primarily dioecious females. Early biomass 

measurements of the Washington State occurrence reflect high growth potential in the 

northwest. 
117

Pathways of Introduction: The dioecious strain was imported to the United States in 

the early 1950s for use in aquariums. It entered Florida's inland water system after plants 

were discarded or planted into canals. The monoecious strain was a separate 

introduction, first found decades later in the Chesapeake Basin. Hydrilla is mainly 

introduced to new waters as castaway fragments on recreational boats, motors, trailers 

and live wells. Stem pieces root in the substrate and develop into new colonies, which 

are commonly found near boat ramps. Once established, boat traffic continues to shatter 

and spread hydrilla throughout the waterbody. Both types propagate primarily by stem 

fragmentation, although axillary buds (turions) and subterranean tubers are also 

important. Tubers are resistant to most control techniques and may be viable as a source 

of reinfestation for many years. Hydrilla may be unknowingly transplanted into private 

ponds as a contaminant on water garden plants. 

Management considerations: Potential biological controls include grass carp 

Ctenopharyngodon idella and leaf-feeding flies. Grass carp are effective but are 

vegetative generalists, so they should be used with care so as not to destroy native aquatic 

vegetation. Leaf-eating flies are still under evaluation for their effectiveness. They are 

species specific but do not appear to reduce hydrilla biomass significantly. Grass carp, 

themselves are regulated species in Idaho with only certified sterile (triploid) fish being 

permitted. 

Harvesting and use of motorized boats is not recommended in partially infested lakes or 

where uncontaminated water bodies occur nearby, because this can chop the plants and 

facilitate spread of shoot fragments. In ponds and small lakes, water draw-downs, which 

expose and kill the plants, have been found to be temporarily effective. Weed mats in 

public access sites to contain spread and signage to increase public awareness are some of 

the containment methods adopted. 

Aquatic herbicides are effective at temporarily controlling the weed but do not kill the 

tubers, turions, and seeds. 
118
119

Brazilian elodea Egeria sp.

Ecology: Egeria sp. is a submersed, freshwater perennial herb that grows on the bottom 

in depths of up to 20 feet depending on water clarity. It is found in both still and flowing 

waters, in lakes, ponds, pools, ditches, and quiet streams. Stems are erect, cylindrical, 

simple or branched, and grow until they reach the surface of the water where they form 

dense surface mats. This plant is easily and regularly confused with hydrilla. 

Egeria sp. initiates growth when water temperatures reach 10 C. Two major growth 

flushes occur, in spring and fall. Each of these flushes is followed by a period of 

senescence, with a loss of biomass through sloughing and decay of tips and branches. 

Flowers (18-25mm) are produced on the water’s surface in late spring and again in the 

fall. The intensity of flowering varies from year to year. Egeria is not known to produce 

viable seeds in the United States. During the summer, profuse branching forms a canopy. 

The branches form dense, tangled mats on the water's surface. 

The absence of sexual reproduction in introduced populations of Egeria sp. emphasizes 

the importance of the vegetative growth phase of the plant. Specialized nodal regions 

described as double nodes occur at intervals of 6 to 12 nodes along a shoot. A double 

node consists of 2 single nodes separated by a greatly shortened internode. Double nodes 

produce lateral buds, branches, and adventitious roots. Only shoot fragments of Egeria 

sp. which contain double node regions can develop into new plants. Egeria sp. lacks 

specialized storage organs such as rhizomes or tubers and stores carbohydrates in stem 

tissues. 

Egeria sp. forms dense mono-specific stands that restrict water movement, trap sediment, 

and cause fluctuations in water quality. Dense beds interfere with recreational uses of a 

water body by interfering with navigation, fishing, swimming, and water skiing. It has 

exhibited the ability to rapidly recolonize de-vegetated areas following. 

Distribution: Native to South America, this species has been introduced to Asia, 

Australia, Europe, New Zealand, and North America. In the United States, it is 

widespread along the eastern seaboard, the Gulf coast, and in California. It has been 

reported in Washington, Oregon, and Utah. It is not yet naturalized in Idaho but is sold 

here as an aquarium plant. 

Pathways of Introduction: E. densa was first reportedly offered for sale in the United 

States in 1915, where it was recommended as a good "oxygenator" plant. It is a popular 

aquarium plant and can be found for sale in most pet shops, usually under the name 

anacharis. It is one of several invasive aquatic plants sold in aquarium or water garden 

dealerships, advertised on commercial websites, or occurring as contaminants among 

plants that are offered for sale. 

Management considerations: Grass carp find Egeria sp. highly palatable (when older 

than fingerlings) and have been successfully employed as a management tool elsewhere 

in the US, though it is important to note only sterile (triploid) grass carp are legal in 
120

Idaho. Where they have been employed, they have been observed to remove the entire 

submersed aquatic community, and thus represent an equivalent ANS. 

Localized control (in swimming areas and around docks) can be achieved by covering the 

sediment with an opaque fabric which blocks light from the plants. Managers of 

reservoirs and some lake systems may have the ability to lower the water level as a 

method of managing Egeria. Producing no seeds or perennial rhizomes or tubers, Egeria 

can be effectively controlled for a few years by drawdown, desiccation and freezing. 

Because this plant spreads readily through fragmentation, mechanical controls (such as 

cutting, harvesting, and rotovation underwater rototilling) should be used with care. In 

some locations, appropriate herbicides can be used successfully. 
121

European frog-bit Hydrocharis morsus-ranae

Ecology: European frog-bit is an herbaceous, annual freshwater species that can reach 

20 cm in length. It does well in quiet open water and can be found in marshes, ditches 

and swamps. It grows well in sheltered coves and along the still water shorelines of 

rivers, lakes and streams. The leaves of this plant are usually floating, but if the 

vegetation is dense enough, they can be emergent. Each plant has numerous, fibrous, 

free floating roots which can attain a maximum length of 30cm. In early summer, the 

plants produce small, white, three petaled, unisexual flowers. Despite profuse flowering 

during the summer, European frog-bit rarely produces seeds and instead relies on 

vegetative reproduction for survival and spread. Multiple plantlets develop along the 

stolons, or runners, of each plant during the growing season. In the fall, European frogbit produces buds, called turions, which sink to the substrate where they remain dormant 

until the springtime, at which time the developing buds floats to the surface and mature. 

One plant is capable of producing about one hundred of theses turions each year. In 

spring European frog-bit develops free-floating mats comprised of interlocking plants 

that have recently developed from overwintering turions. These mats stabilize in position 

as water levels drop and roots elongate. 

Because of the dense floating mat of vegetation produced by European frog-bit, available 

light, dissolved gases, and nutrients were reduced to submersed aquatic plants attempting 

to grow beneath this mat. The plant is often a dominant species in the wetlands within 

which it occurs. By dominating wetlands with its thick mats, European frog-bit displaces 

native flora and is perhaps affecting the fauna. European frog-bit is also implicated in 

limiting water flow in irrigation systems and restricting water traffic, thereby hindering 

recreational activity. On the other hand, European frog-bit is a food plant for several 

water birds, rodents, fish and insects. 

Distribution: European frog-bit is native to Eurasia but has been present in North 

America since at least 1932, when it was intentionally introduced for horticultural 

purposes in an arboretum in Ottawa. By 1955 its North American distribution extended 

from Ottawa to Montreal. By 1980 it had extended southwest to Lake Ontario and 

northeast to Quebec City. Recently it has spread throughout much of the central and 

southwestern parts of southern Ontario, and further into northern New York, Vermont, 

and eastern Michigan. By 2002 it was found to be established in a lake in Snohomish 

County, Washington. 

Pathways of Introduction: Self-propelled spread takes place primarily vegetatively by 

means of strong cord-like stolons and the production of winter turions. Boats and 

waterfowl can transport both turions and plantlets, expediting the expansion from one 

region to another. Water currents in connected waterways, canals, and watersheds can 

also facilitate its dispersal. 

Management considerations: The best management policy is to prevent the spread of 

this species. Plants can be harvested by mechanical means or by hand depending upon 

the extent of the infestation and the water depth. There are no known biocontrol agents 
122

that have been introduced into the US. Herbicide research has been limited, but the broad 

spectrum herbicides may be effective. 
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Water chestnut Trapa natans

Ecology: Water chestnut is an annual aquatic plant with a submerged flexuous stem that 

is anchored in the mud and extends upward to the surface of the water, much like a water 

lily. Water chestnut features a rosette of floating, fan-shaped leaves, each leaf having a 

slightly inflated petiole (stem); the roots are fine, long and profuse. The small, 4-petalled 

flower is white and the fruit is a large nut with four sharp spines. Water chestnut grows 

best in shallow, nutrient-rich lakes, ponds, canals, and rivers and is generally found in 

waters with a pH range of 6.7 to 8.2 and alkalinity of 12 to 128 mg/L of calcium 

carbonate. 

Flowers are produced singly on stalks arising from the center of the floating rosette of 

leaves. Four triangular sepals surround the flower and develop into barbed spines in the 

mature fruit. Once the ovules of the insect pollinated flowers are fertilized, the flower 

stalks curve downward, allowing the fruit to develop under water into a nut-like, barbed, 

spiny seed. The single-seeded woody fruits produced from the previous year germinate 

in early spring. A single seed may give rise to 10 to 15 plant rosettes, and each rosette 

can produce up to 15 to 20 seeds. Ungerminated seeds may remain viable for many 

years, but most seeds probably germinate in the first two years following their formation. 

Water chestnut is a fierce competitor in shallow waters with soft, muddy bottoms. 

Uncontrolled, it creates nearly impenetrable mats across wide areas of water. In 

Vermont, many previously fished bays of southern Lake Champlain are now inaccessible, 

and floating mats can create a hazard for boaters. It is also a human nuisance because 

mature Water chestnut nuts drift to shore where their sharp spines injure bare feet. This 

noxious plant also severely limits the passage of light into the water, a critical element of 

a well-functioning aquatic ecosystem. It reduces oxygen levels, which may increase the 

potential for fish kills. Water chestnut out competes native vegetation and is of little 

value to wildfowl. 

Distribution: While established in the northeastern United States since the late 1800s, 

this Asian native continues to advance into new areas in New England and the MidAtlantic states. In the past two years, New Hampshire and Connecticut have experienced 

first occurrences of this robust floating aquatic plant. Water chestnut has reappeared in 

tributaries of the Chesapeake Bay where plants were first experienced in the 1920s. 

Pathways of Introduction: The plant spreads when rosettes detach from the stems and 

float to another area. Currents or waves carry nuts to other parts of water bodies. 

Dispersal of rosettes by boats or waterfowl is possible, though probably not a primary 

method of spread. Some infestations may be a result of water garden escapes. 

Management considerations: Hand harvesting is an effective means for eradication of 

smaller populations because water chestnut roots are easily uplifted. Their removal is 

imperative because floating, uprooted plants can survive and disperse downstream. The 

potential of water chestnut seeds to lie dormant for many years makes total eradication 

difficult. Raking and hand harvesting from canoes have been effective and are a means 

to promote community awareness and involvement. 
124

Herbicides and mechanical harvesting can both be effective for large-scale control of 

water chestnut populations. Aquatic plant harvesting boats are often employed in 

instances where waterways are blocked and the herbicide 2,4-D has been tested and 

found effective. 
125

Fanwort Cabomba sp

Ecology: Fanwort is a submersed perennial aquarium plant that grows in stagnant to 

slow flowing freshwater. It grows from short rhizomes with fibrous roots on the bottom 

of water bodies and the stems reach the surface, growing up to 10m long. Parts of the 

plant can survive free-floating for six to eight weeks. 

Fanwort is sensitive to dessication, but survives wide fluctuations in water depths and 

grows well in silty substrate. It exhibits reduced vigor in hard substrates. It may be 

found in stagnant or slow-flowing water in streams, small rivers, ponds, lakes, reservoirs, 

sloughs, ditches and canals. Growth of 50 mm a day has been reported in Lake 

Macdonald in Australia. It grows well in high nutrient environments with low pH, but in 

more alkaline waters it tends to lose its leaves. High calcium levels inhibit growth, but 

unlike other aquatic weeds, fanwort can grow well in turbid water. It prefers a warm, 

humid climate with a temperature range of 13-27oC but can survive when the surface of 

the water body is frozen. 

Fanwort spreads primarily by stem fragments or rhizomes. The erect shoots are simply 

upturned extensions of horizontal rhizomes. The species forms large clones as new 

rhizomes and floating shoots arise as axillary branches. The rhizomes are fragile and 

easily broken, facilitating vegetative spread and transport to new areas. 

Fanwort is an extremely persistent and competitive plant. Under suitable environmental 

conditions it forms dense stands and crowds out native plants. Once established, this 

plant can clog drainage canals and freshwater streams, interfering with recreational, 

agricultural, and aesthetic uses. Fanwort 's dense mass of underwater stems and leaves 

provide a hazard for recreational water users. When this vegetation dies off, 

decomposition can cause dramatic oxygen reductions and foul smelling water. 

Cabomba sp. is commonly used as an aquarium plant because of its delicate appearance. 

Large numbers of plants are sent from Florida to the rest of the United States for 

commercial use. It is also grown commercially in Asia for export to Europe and other 

parts of the world. In its native habitat Cabomba sp. is eaten by waterfowl and some fish 

and provides cover for some small fish and plankton. 

Distribution: Cabomba sp. is native to southern Brazil, Paraguay, Uruguay and 

northeast Argentina, and the southeastern US. It has been dispersed throughout the world 

by the aquarium trade and is naturalized in Peru, China, India, Japan, Malaysia, parts of 

Australia, and Canada. In the United States it is naturalized in the northeast from 

Maryland to Maine, in western New York and Pennsylvania, in Michigan and Indiana, 

and in Oregon and Washington. 

Pathways of Introduction: Cabomba sp. is commonly used as an aquarium plant 

because of its delicate appearance, and is spread through aquarium release. Like many 

problem aquatic plants, fanwort can reproduce from small fragments. Fanwort stems 

become brittle in late summer, which causes the plant to break apart, facilitating its 

distribution and invasion of new water bodies. 
126

Management considerations: Fanwort is sensitive to dessication and requires 

permanent shallow water; therefore, drawdown can provide temporary control. The root 

ball must dry out thoroughly or the plant will quickly return. Preventing new outbreaks is 

the most effective control method. As the plant is submerged and not easily visible, 

education and public awareness are needed to prevent the spread of fanwort. People also 

need to be educated to buy other species of aquarium plants. 

In a recreational water body or river, hygiene protocols are needed to ensure wash down 

of boats, trailers and fishing equipment. Habitat modification via re-vegetation is also 

recommended and may offer some control if it produces a shading effect. Because 

fanwort requires direct sunlight, shading has been used to kill it in small areas; however 

the cost is prohibitive for large-scale programs. In a closed water body with a heavy 

infestation, it is recommended to use strict hygiene regulations and mechanical control 

(involving cutting and removing plants and ensuring fragments are not spread). In the 

case of isolated plants and in small areas physical control (hand pulling by divers) and the 

use of herbicides may offer suitable control. 

Herbicide treatments have been used for fanwort control. Grass carp are known to eat 

fanwort, but they do not prefer it. Unlike most other rooted aquatic plants, fanwort may 

get most of its important nutrients from the water rather than the sediment. Therefore, 

fanwort may be sensitive to reduction of nutrients in the water. 
127

Appendix C. List of Known Nonindigenous Aquatic Species in 

Idaho. 

The following is a list of nonindigenous species known to be likely present in Idaho. It 

includes species that have been classified as High priority ANS along with others that 

would fall into medium or low categories after complete classification. Not all species in 

this list are ANS. It also contains species that the state would not currently classify as 

ANS species due to their beneficial nature in selected waters, such as introduced game 

fish species. 

Scientific Name Common Name 

Plants 

"Aquatic" Group 

Alopecurus geniculatus water foxtail, meadow foxtail 

Bassia hirsuta hairy smotherweed 

Butomus umbellatus flowering rush 

Callitriche stagnalis pond water-starwort 

Crypsis alopecuroides foxtail pricklegrass, fox-tail timothy 

Glyceria fluitans water mannagrass 

Iris pseudacorus yellow iris, paleyellow iris 

Lythrum salicaria purple loosestrife 

Lythrum tribracteatum threebract loosestrife 

Mentha spicata spearmint 

Myriophyllum aquaticum parrot-feather milfoil 

Myriophyllum spicatum Eurasian watermilfoil 

Nasturtium officinale Syn. Rorippa nasturtium-aquaticum water-cress, watercress 

Nymphaea odorata white water-lily 

Polygonum hydropiper marshpepper knotweed, marshpepper smartweed 

Potamogeton crispus curly pondweed 

Rorippa sylvestris creeping yellowcress 

Sparganium emersum European bur-reed 

Typha angustifolia narrowleaf cattail 

Vaccinium macrocarpon cranberry 

Vallisneria americana eel-grass 

Zizania palustris var. palustris northern wildrice 

"Terrestrial Wetland" Group 

Acer negundo var. violaceum box elder 

Acer saccharinum silver maple 

Aegopodium podagraria bishop's goutweed 

Allium schoenoprasum wild chives 

Alopecurus pratensis meadow foxtail, field meadow foxtail 

Amaranthus blitoides mat amaranth 

Amorpha fruticosa desert false indigo 

Apium graveolens wild celery 

Arctium minus lesser burdock 

Artemisia biennis biennial wormwood 
128

Barbarea vulgaris garden yellowrocket 

Bassia hyssopifolia fivehorn smotherweed 

Briza minor little quakinggrass 

Calystegia sepium hedge false bindweed 

Cardaria draba whitetop, hoary cress 

Carduus acanthoides plumeless thistle 

Carduus nutans musk thistle 

Cirsium arvense canada thistle, creeping thistle 

Cirsium vulgare bull thistle 

Conium maculatum poison-hemlock 

Cynoglossum officinale common hound's-tongue, houndstongue 

Cyperus esculentus yellow nutsedge, chufa flatsedge 

Echinochloa crus-galli barnyard grass 

Echinochloa muricata rough barnyardgrass 

Elaeagnus angustifolia Russian olive 

Elymus repens Syn. Agropyron repens, Elytrigia repens quackgrass, creeping wild rye 

Fraxinus pennsylvanica green ash 

Galega officinalis common milkpea, goatsrue 

Holcus lanatus common velvetgrass 

Impatiens glandulifera ornamental jewelweed, policeman’s helmet 

Juglans regia English walnut 

Lactuca tatarica var. pulchella Syn. Lactuca pulchella blue lettuce 

Lepidium latifolium perennial pepperweed 

Linaria vulgaris butter-and-eggs, yellow toadflax 

Lythrum hyssopifolium Syn. L. hyssopfolia hyssop loosestrife 

Mentha ×piperita peppermint 

Morus alba white mulberry 

Myosotis scorpioides true forget-me-not 

Nepeta cataria catnip 

Phalaris arundinacea reed canary grass 

Phragmites australis common reed 

Plantago major common plantain 

Poa annua annual bluegrass 

Poa trivialis rough bluegrass, Scribner bluegrass 

Polygonum argyrocoleon silversheath knotweed 

Polygonum bohemicum Bohemian knotweed 

Polygonum cuspidatum Japanese knotweed 

Polygonum persicaria spotted ladysthumb 

Polypogon monspeliensis annual rabbitsfoot grass 

Populus deltoides eastern cottonwood 

Populus fremontii Fremont's cottonwood 

Prunus avium bird cherry 

Prunus cerasifera cherry plum 

Puccinellia distans weeping alkaligrass, spreading alkali grass 

Ranunculus acris tall buttercup 

Ranunculus repens creeping buttercup 

Rorippa austriaca Austrian yellowcress, Austrian fieldcress 
129

Rosa eglanteria sweetbriar rose 

Rumex crispus curly dock 

Rumex obtusifolius bitter dock 

Sagina procumbens birdeye pearlwort 

Salix alba white willow 

Sonchus arvensis perennial sowthistle, moist sowthistle 

Sonchus asper spiny sowthistle 

Spergularia diandra diandra sandspurry, Mediterranean sandspurry 

Tamarix spp. saltcedar 

 

Fish 

Ameiurus melas black bullhead 

Ameiurus natalis yellow bullhead 

Ameiurus nebulosus brown bullhead 

Carassius auratus goldfish 

Characidae pacu sp. 

Coregonus clupeaformis lake whitefish 

Ctenopharyngodon idella grass carp 

Cyprinus carpio common carp 

Esox lucius northern pike 

Esox masquinongy x lucius tiger musky 

 Fundulus diaphanus banded killifish 

Gambusia affinis western mosquitofish 

Gila bicolor tui chub 

Ictalurus furcatus blue catfish 

Ictalurus punctatus channel catfish 

Lepomis cyanellus green sunfish 

Lepomis gibbosus pumpkinseed 

Lepomis gulosus warmouth 

Lepomis macrochirus bluegill 

Micropterus dolomieu smallmouth bass 

Micropterus salmoides largemouth bass 

Misgurnus anguillicaudatus oriental weatherfish 

Notemigonus crysoleucas golden shiner 

Notropis hudsonius spottail shiner 

Noturus gyrinus tadpole madtom 

Oncorhynchus clarki henshawi Lahontan cutthroat trout 

Oncorhynchus mykiss aguabonita golden trout 

Perca flavescens yellow perch 

Pimephales promelas fathead minnow 

Pomoxis annularis white crappie 

Pomoxis nigromaculatus black crappie 

Pygocentrus or Serrasalmus sp. piranna sp. 

Pylodictis olivaris flathead catfish 

Salmo salar Atlantic salmon 

Salmo trutta brown trout 

Salvelinus alpinus Arctic char 

Salvelinus fontinalis brook trout 

Salvelinus namaycush lake trout 
130

Salvelinus namaycush x fontinalis splake 

Stizostedion vitreum walleye 

Thymallus arcticus Arctic grayling 

Tilapia aurea blue tilapia 

Tilapia mossambica Mozambique tilapia 

Tinca tinca tench 

Xiphophorus helleri green swordtail 

Amphibians 

Rana catesbeiana bullfrog 

Taricha granulosa rough-skinned newt 

Invertebrates

Corbicula fluminea Asian clam 

Mysis oculata relicta Opossum shrimp 

Orconectes virilis virile crayfish, northern crayfish 

Potamopyrgus antipodarum New Zealand mudsnail 

Radix auricularia big-ear radix 
131

Appendix D. Idaho’s Rapid Response Strategy1

Much of this ANS plan is dedicated to either preventing new unwanted species from 

arriving and becoming established in Idaho, or to control the spread of those that are 

already established. However, another important function of this ANS plan is to be the 

basis for a coordinated early detection and rapid response to newly discovered species or 

to the recent spread to previously uninfested waters. This might be viewed as the 

response to an emergency situation, no less important or demanding of proper planning 

before the event than if a truck of toxic chemicals overturned near a stream. 

Currently, Idaho’s response to a new or spreading invasion of an ANS is likely dependent 

upon chance—a concerned informed sportsman or the employee of any number of 

agencies might see something out of the ordinary and reports it to a supervisor or 

someone they think might be “in charge”. Whether this happens in a timely fashion with 

the report made to a responsible official who will take responsibility for appropriate 

responses is more a matter of luck than thoughtful planning before the fact. As such, this 

portion of this ANS plan is dedicated to outlining a series of rapid response actions 

protocols that, if followed, will provide for an adequate and timely response. It is 

patterned after the recently completed rapid response plan for zebra and quagga mussel, 

necessitated by the discovery of this particular ANS in the Colorado River. It is also 

based upon ten objectives to be achieved through a rapid response plan, including: 

• Verify reported detection 

• Make initial notifications to all relevant managers 

• Define extent of colonization 

• Set up an interagency response management team 

• Establish external communications system 

• Organize resources (personnel, equipment, funds, etc.) 

• Prevent further spread via quarantine and pathway management 

• Launch available/relevant control actions 

• Institute long-term monitoring 

• Evaluate the response and the Rapid Response Plan 

Rapid Response Objective 1: Verify Reported Detection 

Purpose: Confirm the veracity of the report, determine the condition (age, maturity, 

spawning status, etc.) of the species, and ensure that everyone is handling reports 

consistently and judiciously across a broad geographic area. 

Lead entity: The agency that receives and accepts responsibility for handling the initial 

report in coordination with the state, tribal, provincial, and/or federal agency where the 

initial sighting of species occurs. 

 

1

 Adapted from the “Columbia River Basin Rapid Response Plan for Zebra Mussels and other Dreissena 

species.” 
132

Tasks:

1. Interview the reporter(s) to validate detection by: 

• Recording details of the location such as name of the water body, landmarks, 

highway mile, and other (GPS if possible) where the suspect species were found. 

• Collecting contact information from the reporter(s). 

• Securing an estimate of the number, density, extent of the species colonies found. 

• Obtaining a digital or other photograph (with scale indicator), if possible. 

• Securing a sample of the species, if possible. 

• Documenting the date and time of sighting(s). 

• Noting other relevant conditions (access limitations, etc.) 

2. Validate identification as soon as possible via examination of a physical sample. 

• When feasible, arrange for a site visit by at least one recognized expert 

(preferably a small team). 

• If recognized experts cannot feasibly reach the site within 24 hours, arrange to 

have samples and other evidence (e.g., photographs) sent via Express Mail 

Service or email to the most accessible recognized expert. 

• Prior to shipping samples, obtain guidelines from recognized experts and use any 

existing protocols regarding handling of the sample, desired quantity, where and 

how to deliver the sample, etc. 

Rapid Response Objective 2: Make Initial Notifications 

Purpose: Ensure that all parties that have jurisdiction in response decisions or can 

provide technical support are quickly engaged and to also rapidly inform all other 

interested parties. 

Lead entity: The agency that initially receives confirmation of the species identification 

Tasks: 

1. Within the first 24 hours or as soon as practical after a physical sample is visually 

confirmed to be an ANS by a recognized expert, the agency receiving such 

confirmation (with assistance from agencies in relevant jurisdictions) will notify all 

primary management contacts. It is critical that this notification list be updated, and 

preferably tested, at least annually. 

2. Secure verification of notifications to confirm that parties on the contact list did, in 

fact, receive notification (e.g., Internet list server response confirmation requirement, 

phone list call-backs, etc.). 

3. While proceeding with subsequent response activities described below, obtain 

secondary visual confirmation of species identification via a different expert. Also 

submit a sample to an expert who can provide definitive confirmation based on 

genetic or histological analysis. 

This process is summarized in the following figure. 
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Report recipient gathers evidence and provides to 

recognized expert(s) for confirmation. 

Initial identification is 

confirmed by recognized 

expert(s). 

Report is 

received 

Notification Protocol 

Confirmation by 

second expert and/or 

further 

genetic/histological 

analysis. 

Rapid Response Objective 3: Define Extent of Colonization

Purpose: Rapidly provide information on location of introduced species to guide 

subsequent management decisions, including survey design. 

Lead entity: The appropriate state or federal agency where the initial sighting(s) of 

species occurs in partnership with other agencies and organizations. 

Tasks: 

1. Determine geographic extent and demography of infestation, including upstream and 

downstream areas and connected water bodies. Also survey nearby water bodies with 

vulnerability to the same vectors. 

2. Identify a lead monitoring coordinator who can maximize the effectiveness of survey 

efforts by individual agencies. 

Notification of 

Priority 1 contacts. 

Notification of 

Priority 2 and 3 

contacts. 

Proceed with additional response 

activities, including delineation of 

infestation. 
134

3. Identify any potential facilities (e.g., hydropower, fish hatcheries, irrigation systems, 

etc.) that could be affected. 

4. Ensure that surveys are completed and that results are reported through responsible 

tracking organizations. 

Rapid Response Objective 4: Set Up an Interagency Response Management Team

Purpose: Activate a predetermined response management system that expedites 

decision-making, information sharing, avoids duplication, and minimizes authority 

conflicts while preserving flexibility for adaptive management. Use the Incident 

Command System as a foundation for the response organization and decision-making 

processes. Any existing agreement documents developed in association with this rapid 

response plan should be consulted to guide the steps below. 

Lead entity: Incident Commander(s), as defined below, in collaboration with overall 

response team. 

Tasks: 

As soon as possible, the appropriate state agency associated with the initial sighting of 

ANS convenes a meeting and/or conference call involving all relevant managers and 

these cooperators. During this initial meeting, a response organization should be 

established using the Incident Command System (ICS) as a foundation. Where multiple 

agencies have lead jurisdiction, a unified command structure should be used. The 

incident commander(s) will serve as the focal point for coordinating implementation of 

the rapid response plan, and in cooperation with the overall responses team, will establish 

other components of an ICS organization as needed (e.g., Operations Branch). Where 

time allows, the incident commander(s) will seek collaborative decision-making by the 

entire team of involved response agencies. For a multi-state infestation where there is no 

initial consensus on the incident commander role, this default role will fall to the 

appropriate USFWS Regional ANS Coordinator until the relevant authorities reach 

agreement on an alternative. 

The incident commander(s) will: 

• Coordinate Interagency Team notification operations 

• Facilitate creation of an ICS organization involving lead representatives of each 

local, tribal, state, provincial, and/or federal government that has legal authority 

over the response, and comprised as appropriate by specific ICS staff positions 

(e.g., safety officer) and divisions (e.g., Operations). 

• Represent (i.e., be the spokesperson for) the management team. 

• Facilitate a decision-making process that considers consensus processes and 

cascading levels of authority within individual agencies 

• Facilitate development of response priorities 

• Establish planning horizons for the response (e.g., 2 weeks vs. 2 months vs. 2 

years) 
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3. These above actions should take into account roles/relationships/inter-agency 

agreements among: 

• All affected states: e.g., Governor, state agencies, ANS Coordinator and 

Canadian provinces. 

• Federal agencies: USFWS, ACOE, USEPA, NOAA, etc. 

• Tribes. 

• Local governments. 

• Other interested parties, such as irrigation districts, marinas, etc. 

4. The incident commanders should develop a technical advisory team that includes 

experts from outside the region to help advise response activities. 

Rapid Response Objective 5: Establish External Communications System

Purpose: Develop an information center to ensure consistent and effective 

communication to interested external stakeholders, including the media and public. 

Lead Entity: Incident Commander(s) identified in Objective 4 above.

Tasks: 

1. Notify and educate affected landowners, and where appropriate, gain their written 

permission to access property for response activities. 

2. Notify and educate potentially affected water users and water-rights holders. 

3. Develop public information strategy, press packets, press release process, and press 

conferences. 

4. Develop and implement general public education and outreach. Since there are a 

variety of educational materials between regions and states, assure coordination and 

perhaps agreement on materials that can be used region-wide. 

Rapid Response Objective 6: Organize Resources

Purpose: Provide sufficient resources to initiate control actions and associated activities 

(including acquisition of required permits). 

Lead Entity: The Incident Commander(s) identified in Objective 4 above in partnership 

with all other organizations involved in the response.

Tasks: 

1. Develop estimates for staffing needs, facilities and equipment, and funding. 

2. Identify potential sources for staffing, facilities, equipment, and funds. 
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3. Secure commitments for needed staff, facilities and equipment, and funds. 

4. Ensure mechanism for dispersal of funds is in place, and when the funds are needed, 

flow of dollars occurs expeditiously. For applicable jurisdictions, this includes 

pursuing declarations of emergency by elected officials. 

Rapid Response Objective 7: Prevent Further Spread Via Quarantine and Pathway 

Management 

Purpose: Minimize all vectors that might further spread the original infestation. 

Lead Entity: Incident Commander(s) and agencies with regulatory jurisdiction 

Tasks:

1. Evaluate risks, dispersal vectors (including movement by humans, fish and wildlife, 

water traffic, water flow, and other physical processes). 

2. Restrict dispersal pathways, where feasible, including the following or similar 

measures that are suitable for individual species: 

• Quarantine any hatcheries or aquaculture operations that are likely to spread 

the species or their larvae via transfers outside the affected watershed(s). 

• Quarantine infested water bodies as needed to prevent spread by watercraft or 

other vectors following any existing protocols. 

• Assess the likely movement of boats that recently used the infested water body 

to identify inspection needs in other water bodies. 

• Establish wash and inspection requirements on boats and equipment, and 

provide for associated logistical support (e.g., disinfection kits). 

• Ensure that species “alert” signs are adequately deployed. 

• Develop and implement Hazard Analysis and Critical Control Point (HACCP) 

plans to ensure that local, state, tribal or federal government response 

personnel do not further spread the original infestation. 

• Work with the information center to design and implement educational 

outreach programs using print, electronic media and other avenues, with an 

emphasis on water users. 

• Stop or slow water release to potentially uninfested sites. 

• Draw water from below thermocline. 

• Install physical barriers. 

Rapid Response Objective 8: Initiate Available/Relevant Control Measures

Purpose: Evaluate management options, and then proceed with either eradication efforts 

or containment/mitigation activities. 
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Lead Entity: Incident Commanders in collaboration with overall response team 

Tasks: 

1. Decide if eradication is possible based on rapid analysis of population dynamics and 

pathways of spread. Consider the following: 

• Anticipated cost of eradication effort relative to available funding 

• Type of water body – contained lake, mainstem reservoir, tributary reservoir, 

small stream, large river, estuary, or water diversion facility. 

• Type of substrate – e.g., rocks that allow species attachment on their 

undersides where chemicals may not reach them. 

• Extent of population distribution – isolated vs. widespread coupled with a 

priori assumptions about the spread of species before detection. 

• Life stage(s). 

• Amount of water in reservoir or waterway. 

• Does the reservoir need to be drawn down before treatment? 

• How far can the reservoir be drawn down? 

• Is river flow low enough for effective treatment? 

• Circulation patterns in water body. 

• Spreading pattern of population within the water body. 

• Inflow rates and sources. 

• Presence of state or federally listed threatened or endangered species. 

• Special status of water body, including: 

1. Water use designation e.g., drinking water. 

2. ‘Wild and scenic’ designation. 

3. Wilderness area. 

4. Potential impact to cultural resources. 

5. Department of Defense or other restricted access areas 

6. Tribal lands 

7. Endangered Species Act critical habitat 

8. Clean Water Act 303(d) listing 

9. Beneficial Uses of water bodies 

2. If eradication is attempted, select appropriate methods. 

3. If eradication is not possible, develop control objectives and select/design appropriate 

control measures. 

4. Obtain relevant permits and regulatory agency concurrence 

• Determine the permits and other regulatory reviews required for chosen 

eradication methods, including any applicable emergency provisions. 

• Begin with any existing permits and/or templates for required permits. 

• Assign lead person from each regulatory agency to facilitate permit approval in a 

timely manner within their respective agency. 

• Obtain a FIFRA Federal Crisis Exemption e.g., 40 C.F.R. PART 166 if the known 

or accepted methods of eradication are not currently permitted. 
138

• Determine if an environmental impact statement or environmental assessment is 

required and if so, begin that work. 

• NPDES (Section 402) 

• NEPA (using template for environmental assessments where available) 

• Initiate Endangered Species Act Section 7 consultations if needed by contacting 

appropriate USFWS and NOAA field offices. 

5. Implement eradication or control strategies 

• Lead coordinator facilitates implementation of operations plan developed by 

management team 

• Agencies collaborate to coordinate and deploy field resources 

• Establish schedule for frequent management team meetings to resolve operational 

issues that cross jurisdictional interests. 

Rapid Response Objective 9: Institute Long-Term Monitoring 

Purpose: Provide for data for adaptive management and long-term evaluation efforts. 

Lead Entity: Incident Commander(s) in collaboration with overall response team

Tasks: 

1. Design a monitoring program to evaluate the status of the species. Monitoring 

activities should be carried out in coordination with other field operations, such as 

environmental monitoring to meet permit and other regulatory compliance 

requirements (e.g. National Pollution Discharge Elimination System (NPDES)). 

2. Disseminate findings through an easily accessible, consolidated, coordinated realtime database and list serve (e.g., via 100th Meridian Initiative website) 

Rapid Response Objective 10: Evaluate the Response and the Rapid Response Plan 

Purpose: Allow for adaptive management by ensuring feedback on the efficacy of 

response actions and the effectiveness of the Rapid Response Plan; enhance long-term 

Preparedness for response to other aquatic invasive species introductions. 

Lead Entity: Responsible state and federal agencies 

Tasks: 

1. Conduct a follow-up evaluation of response organizations and other interest groups to 

identify opportunities for improving rapid response capacity. Disseminate “lessons 

learned” to other interested organizations e.g., regional ANS panels. 

2. Revise the Rapid Response Plan and associated documents/guidelines based on 

evaluation and long-term monitoring results. 
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3. As resources allow, develop and implement a research plan that evaluates the 

associated ecological and economic impacts of the invasion, the effectiveness of 

management interventions, and negative consequences of management interventions 

beyond that required by permits. 

4. Determine the need for long-term funding for the current management effort and seek 

this funding as warranted. 

• Meet with state and federal legislators to map out a regionally coordinated 

long term funding strategy