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Closeup of mussels on boat prop

Conservation > AIS What are Aquatic Invasive Species?


Aquatic Invasive Species (AIS) are plants, animals, or pathogens that are not native to Montana and can cause harm to our environment and economy.


AIS are introduced accidentally or intentionally outside of their native range. AIS populations can reproduce quickly and spread rapidly because there are no natural predators or competitors to keep them in check. AIS can displace native species, clog waterways, impact irrigation and power systems, degrade ecosystems, threaten recreational fishing opportunities, and can cause wildlife and public health problems.


Prevention is our best defense!

Once established, there are few if any means to control AIS in natural waterbodies.  Control efforts are very expensive and total eradication is very unlikely.

You are the first line of defense in preventing the spread of aquatic invasive species.

How AIS got to Montana


AIS can be moved to new locations in many ways, most the result of human activity. 

Just one organism, or in some cases a piece of a plant, is enough to start a new invasion.

Some common way that AIS may be moved include:

  • Attaching to watercraft, motor or trailer

  • Transporting by ballast water, bilge, and other water containing devices

  • Dumping of unwanted live bait

  • Attaching to fishing gear, nets and downriggers

  • Sticking to the soles of waders

  • Attaching to waterfowl decoys and hunting dogs

  • Releasing unwanted aquarium fish, pets and plants

  • Transplanting prohibited plants and fish into water gardens and ponds

Aquatic Invasive Species Profiles

Report Suspected AIS

If you see a boat or trailer with aquatic organisms attached to it, call 1-800-TIP-MONT (1-800-847-6668) immediately.

If you see or suspect a new infestation of an invasive plant or animal, please save a specimen and complete a Report a Suspected AIS form

You can also notify the FWP Fisheries office at (406) 444-2440.

Impacts of AIS

Aquatic invasive species pose a threat to the environment, economy, recreation, and human health in Montana.


Environmental Impacts

Humans have created conditions where plants and animals can aggressively invade and dominate natural areas and water bodies in three ways:

  1. Introducing non-native species from other regions or countries that lack natural competitors and predators to keep them in check.

  2. Disrupting the delicate balance of native ecosystems by changing environmental conditions – e.g., stream sedimentation, ditching, building roads – or by restricting or eliminating natural processes – for example building a dam. In such instances, even some native plants and animals can become invasive.

  3. Spreading aquatic invasive species through various methods – these include moving watercrafts from water body to water body without removing invasive plants and animals and releasing bait into water bodies.

The net result is a loss in diversity of our native plants and animals as invasive species rapidly multiply and take over. About 42 percent of the species on the federal threatened or endangered species lists are at risk primarily because of invasive species.

In U.S. water bodies, the rapid spread of zebra mussels shows how profoundly an AIS can alter the environment. These tiny mussels with huge appetites for microscopic plants and animals rapidly reproduce and are capable of severely altering their environment by reducing the food supply for native organisms and by enhancing conditions for the rapid growth of blue-green algae and aquatic vegetation.


Avian Botulism

In the Great Lakes, researchers are trying to determine if zebra mussels promote conditions for the growth of avian botulism, which have caused massive bird fatalities in the past few years, especially on Lake Michigan.


Heavy Metals

Aquatic invasive species affect the amount of heavy metals in our waters in two ways. First, many aquatic invasive species (like zebra and quagga mussels) are filter feeders, meaning they filter the water for free-floating microscopic organisms to feed on. However, this process can cause accumulation of heavy metals in the tissues of filter-feeders, which can in turn lead to increased levels of heavy metals in the surrounding sediments in areas with high densities of invasive mussels. Second, anti-biofouling boat paints and coatings that are used to keep zebra and quagga mussels from attaching to boats are usually made with copper or other toxicants. The increased use of these paints has led to higher levels of copper and other heavy metals in harbors and surrounding areas.


Economic Impacts

In the United States, expenses associated with ecological damage and control of invasive species is estimated at $137 billion per year and increasing.

In Montana, some industries affected negatively by AIS include sport and commercial fishing, agriculture and raw water users – i.e. power companies and utilities. In the case of power companies and utilities, expenses from AIS are passed on to Montana consumers – in the form of higher water and electric bills.

In 2007, Montanans and visitors spent $343 million on fishing across the state. In the Upper Missouri River reservoirs alone, the money spent on fishing is estimated as $13.7 million dollars annually from 1989 to 2011. This could change drastically if invasive species take hold in these waters.

In the United States, congressional researchers estimated invasive mussels cost the power industry $3.1 billion in the 1993-1999 period, with its impact on industries, businesses, and communities over $5 billion (New York Sea Grant 1994a). In Canada, Ontario Hydro has reported zebra mussel impacts of $376,000 annually per generating station (New York Sea Grant 1994b).

A study has recently shown that the presence of dense, mat-like aquatic invasive plants decreases property values up to 16%.


Recreational Impacts

Aquatic invasive species can also alter your recreational activities. Hunters, anglers, and even birdwatchers, among others are impacted by AIS and may find that they are no longer able to comfortably swim, or easily navigate their favorite water bodies. Also, as the habitat is modified by these invaders, the wildlife that depends on it disappears.

Fishing outings can result in disappointment when AIS modify our lake and stream habitat. Eurasian watermilfoil can clog boat motors and invasive animals such as the rusty crayfish gobble up aquatic plants like underwater lawn mowers, reducing habitat for native fish at every stage of their life cycle. The invading crayfish may even eat the eggs of our favorite sport fish.

Boats can be damaged by mussels! Proper boat hull, engine maintenance and cleaning are key to saving thousands of dollars in repair costs resulting from damage caused by zebra and quagga mussels. Juvenile and adult mussels can attach to many different types of substrate including fiberglass, aluminum, wood, and steel. This ability to attach decreases fuel efficiency and damages the boat's finish. Their larvae (called veligers) are extremely small – too small to see without a microscope. When veligers are present in the water they can be drawn into engine passages or can move into them on their own. Once they settle out in the engine cooling system, they can grow into adults and may block intake screens, internal passages, hoses, seacocks, and strainers.


Health Impacts

Some invasive species may cause significant health problems. For example, a South American strain of human cholera-causing bacteria was found in ballast water tanks of ships in the port of Mobile, Alabama in 1991. Also, sharp zebra mussel shells can cut the feet of unsuspecting swimmers and waders. Zebra mussels “clean” the water by removing the phytoplankton at the base of the food chain which can then affect species higher up on the food chain including game fish. This also allows sunlight to reach higher depths which can increase unwanted plant growth.


Swimmer's Itch

Swimmer's itch is caused by the larvae of certain parasitic flatworms that can burrow into your skin while swimming. Humans are not the intended host of this parasite (waterfowl are the intended hosts) but can become an accidental host. Invasive species such as certain snails and plants can harbor the organism’s causing swimmer’s itch and therefore increasing its occurrence in infested water bodies.


Learn more about invasive species in Montana at the Montana Invasive Species Council website.

Monitoring AIS


Montana’s Aquatic Invasive Species (AIS) Early Detection and Monitoring Program has been in place since 2004. Early detection allows Montana Fish, Wildlife & Parks biologists to locate small or source AIS populations, while monitoring allows FWP to study existing population trends and investigate suspect findings.

Montana utilizes a variety of techniques in monitoring for AIS populations. All of Montana’s monitoring protocols have been scientifically reviewed, are updated annually, and are coordinated with neighboring states. Since there are a variety of aquatic invasive species, different sampling techniques are used to increase the likelihood of early detection of each of these species.

Control of AIS

Once an aquatic invasive species is established in a water body, complete eradication is usually impossible or prohibitively expensive, which is why prevention is so important.

However, control options do exist, and the Montana Department of Natural Resources and Conservation (DNRC) offers state-funded grants for the prevention and control of AIS. The goal of the grants is to protect the natural resources of Montana from severe and unacceptable damage from AIS.