What are Aquatic Invasive Species?

Zebra mussels, A. Benson, USGS

Aquatic invasive species (AIS) are “non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health” (1999 Executive Order 13112 – Invasive Species). They are a biological pollutant. Extremely difficult if not impossible to contain, control, or eradicate, invasive species can interfere with our ability to enjoy lakes, ponds, and rivers.

Dense stands of invasive aquatic plants provide unbalanced and substandard physical habitat for many fish species and macroinvertebrates due to the lack of mixed structure normally provided by a diversity of native aquatic plant species. These monocultures also pose a threat to game and nongame species populations alike, and via competition, cause losses or reduction of native plant species.

Invasive aquatic species first turned up in Vermont in Lake Champlain in the 1940s, either because of our direct connection to infestations in New York via the canal system, via hitching a ride on recreational-based water equipment like boats and trailers, or via another pathway.

Some of our largest and most heavily used recreational lakes have infestations of Eurasian watermilfoil – Champlain, Memphremagog, St. Catherine, Bomoseen, Fairlee, among others. Many of these lakes are fortunate to have informed municipalities, active lake associations, and engaged volunteer lake associations dedicated to controlling Eurasian watermilfoil infestations as well as preventing the introductions of other invasive species, including invasive animals like zebra mussels and spiny water fleas. The good news is that roughly 75 percent of Vermont’s 800-plus lakes and ponds do not support an invasive species. Significant resources – time and money – are expended by many of our local communities to keep it this way: Preventing an introduction is far less costly than managing one once an invasive species like Eurasian watermilfoil takes hold.

Understanding Aquatic Invasive Species Threats

The Vermont Department of Environmental Conservation (DEC) tracks both aquatic invasive species confirmed in Vermont, and those threatening Vermont. A full visual listing of aquatic invasive species confirmed and threatening Vermont can be found in the DEC’s “Gallery of Invaders”.


The best defense against aquatic invasive species is to prevent their introduction.

Aquatic invasive species move from waterbody to waterbody by hitching a ride on boats, trailers, water-based gear, and in water. Two effective strategies to prevent their introduction are Vermont Public Access Greeter Programs and Boat Decontamination Stations

Greeter Program:

Vermont Public Access Greeters educate about aquatic invasive species, provide watercraft inspections at public launch points on some Vermont waterbodies, and stop aquatic invasive species introductions. The DEC started this program in 2002 to address the transport of aquatic invasive species by hitching a ride on watercraft, trailers, fishing, and other recreational equipment moving between waterbodies. Information on how to start a Greeter Program can be found on the DEC’s Public Access Greeter Program website. Nearly all Greeter Programs are run by lake associations using both volunteers and paid staff. As of 2018, there are over 25 lakes in the Vermont Greeter network that could help provide you with information on how they work, and how to organize them.

Boat Decontamination Stations:

Public access boat decontamination stations are located at some Vermont waterbodies. These stations provide high pressure, 140°F water needed to effectively remove or kill hitchhiking plants and animals from your watercraft. If the public access has an Agency of Natural Resources authorized inspection station, you must have your vessel and equipment inspected and decontaminated if deemed necessary by the authorized inspection station staff. As of 2021, 4 high-pressure, hot water stations are located at Shadow Lake, Seymour Lake, Harvey’s Lake, and Lake Iroquois.

Vermont law 10 V.S.A. § 1454 prohibits the transport of an aquatic plant, aquatic plant part, or aquatic nuisance species to or from any Vermont waterbody. Violation of this law may result in a fine of up to $1,000. When entering or leaving a waterbody, boaters must inspect their vessel, trailer, motor vehicle and other related equipment and gear to remove any aquatic plants, plant parts and aquatic nuisance species found.

Before moving boats between waterbodies, follow these steps to stop aquatic hitchhikers:

  • CLEAN off any mud, plants, and animals from boat, trailer, motor and other equipment. Discard removed material in a trash receptacle or on high, dry ground where there is no danger of them washing into any waterbody.
  • DRAIN all water from boat, boat engine, and other equipment away from the water.
  • DRY anything that comes into contact with the water. Drying boat, trailer and equipment in the sun for at least five days is recommended if rinsing your boat, trailer parts and other equipment with hot, high pressure water is not an option.

Early Detection

While working on the prevention of aquatic invasive species entering a waterbody, early detection is also extremely important. If the invasive is detected early enough, before it becomes established, it may be possible to eradicate it.

The Vermont Department of Environmental Conservation trains volunteers, Vermont Invasive Patrollers (VIPs) on how to identify and search waterbodies annually for aquatic invasive species. Online and in-person training workshops are scheduled during the summer.

If you discover a new occurrence of an aquatic invasive species in a waterbody, click here to learn what to do, and report it immediately to Kim Jensen from the Vermont DEC at Kimberly.Jensen@vermont.gov or at (802) 490-6120.

Management and Control

Once an aquatic invasive species has become established in a waterbody, control options could include mechanical, physical, chemical, and biological. The most successful programs utilize an integrated approach using multiple control options.

The Vermont DEC has an excellent resource guide to get you started: “Managing Aquatic Invasive Species: A Resource Guide for Vermont Lake Managers”.

Most control methods require an Aquatic Nuisance Control permit from the Vermont DEC, and an integrated pest management plan prior to implementation. Learn more about Aquatic Nuisance Control by the Vermont Department of Environmental Conservation.