The environment, economy, recreation, tourism, and humans are all impacted by the introduction of aquatic invasive species.

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 have the ability to 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

Ecological 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.

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.