Aquatic Invasive Species

Most AIS were transported by humans, through ballast water in ships, dumping from aquariums, or hitchhiking on boat hulls. Outside of their native ecosystem, they find an absence of ecological controls such as disease and predators. This can result in rampant growth and reproduction. Of the non-native species whose origin of introduction to Lake Champlain is known, more than 60 percent entered via canals, particularly the Champlain Canal at the southern end of the lake. Read below about other species poised to join them.

Alewives (Alosa pseudoharengus) were first found in the lake in 2003 and their population has since skyrocketed. They have displaced native smelt species and interfere with trout and salmon reproduction. In the years since their introduction, alewives have become the dominant forage fish. Alewives contain thiaminase, an enzyme that breaks down vitamin B1 (thiamine) and causes deficiency in predator fish. Winter kills of alewives have led to tons of rotting fish washing ashore after the ice has melted, but populations of the fish have remained steady.

Curly-leaf pondweed (Potamogeton crispus) is the only invasive out of dozens of Potamogeton (pondweed) species in Lake Champlain. Introduced in the early 1900s, it spreads primarily by hard, burr‐like winter buds called turions. A single plant can produce hundreds of turions that can germinate the following spring. With a high tolerance for cold water, this species gets a jump start on the growing season by growing in the spring and early summer before conditions are favorable for most other species. By mid‐July, it begins to die back. Curly-leaf pondweed can form dense stands, restricting the growth of native plants, depleting nutrients, and impeding recreation.

Eurasian watermilfoil (Myriophyllum spicatum) was first identified in St. Albans Bay in 1962 and has since spread throughout Lake Champlain. It reproduces almost exclusively by fragmentation—parts of the plant break off, drift, sink, develop roots, and grow into new plants. They can form canopies that block light, inhibiting the growth of native plants and reducing abundance and diversity of invertebrates. Dense populations of Eurasian watermilfoil pose a nuisance to swimmers and boaters. Wind and waves may break plants loose, and boating activity through dense watermilfoil beds also contributes to fragmentation and spread. The closely related AIS variable-leaf milfoil (Myriophyllum heterophyllum) was discovered in Missisquoi Bay and in the South Lake in 2009.

European frogbit (Hydrocharis morsus-renae) is a free‐floating aquatic plant with clusters of small, lily-like heart-shaped leaves. Frogbit does not anchor itself in the sediment but rather is moved around a waterbody by wind and wave action. As a result, the plant often ends up in quiet still waters, such as wetlands and coves. Plants are typically connected by a runner, which can create a dense surface mat. Mats of frogbit block light to submersed plants and crowd out native species, as well as inhibiting the movement of fish and ducks and impairing recreation. 

Spiny waterflea (Bythotrephes longimanus) was first discovered in Lake Champlain in 2014, and the similar fishhook waterflea (Cercopagis pengoi) came shortly thereafter in 2018. Both are native to Europe and Eurasia and have been present in the Great Lakes since the 1980s. Invasive waterfleas compete with native zooplankton and are difficult for small fish to ingest, thus a poorer food source. The long spines of these species can hook them onto anglers’ lines in the hundreds, making fishing difficult.

Golden clam (Corbicula fluminea) is a small freshwater bivalve filter feeder with distinctive concentric ridges that can be found at the surface of sediment or slightly buried in sand. A single adult can produce 35,000 larvae per year, making eradication difficult once established. Large infestations can have negative effects on ecosystems: out-competing native mussels, altering the nutrient cycle, disrupting habitat, and limiting planktonic food availability. The species was detected in Lake George in 2010 and since has resisted management, quickly spreading to occupy 85% of sandy areas. In 2024, a few individuals were discovered in Lake Champlain by an LCC CHAMP volunteer in the southern reaches of the lake. Their presence is being monitored through CHAMP and by state partners.

Water chestnut (Trapa natans) is native to Europe and Asia and was brough to the U.S. as an ornamental plant in the late nineteenth century. By the 1940s it was reported in the southern reaches of Lake Champlain. The plant has a submersed, flexible, feathery stem whose roots anchor into the mud of shallow lakes, ponds, and slow-moving streams. The stem can extend up to 16 feet toward the surface, where the plant will put out rosettes of glossy, floating, fan-shaped leaves. Water chestnut forms dense mats that block sunlight from reaching submersed native species, provide little nutritional or habitat value to native species, and inhibit recreation. One of the few AIS that only reproduces by seed, it produces a distinctive seed with four sharp spines and barbed hooks, posing a threat to swimmers and walkers. Since it does not reproduce with fragmentation, it is responsive to active management through mechanical and hand harvesting.

Zebra mussels (Dreissena polymorpha) are small, freshwater, bivalve shellfish that were likely brought to the U.S. as stowaways in the ballast water of ships travelling through the St. Lawrence Seaway. Native to the Caspian and Black Seas south of Russia and Ukraine, they have become widespread in both Europe and the U.S. Zebra mussels were first reported in Lake Champlain in 1993 and have since proliferated. The mussels are armed with root-like proteins called byssal threads that allow them to attach to nearly any surface--including rocks, docks, and native species. Adaptable and prolific, zebra mussels can smother native mussel species, coat water intake pipes, and slice the feet of unsuspecting swimmers. As filter feeders, they dramatically alter the water quality and native food web of the lake by overconsuming plankton. Read more about zebra mussels in Lake Champlain here.

Lake Champlain has over 50 non-native species in its waters, about a dozen of which are considered aquatic invasive species. Surrounding waterways have even more non-native species: the Hudson River has 146, and the Great Lakes have 190. These waterbodies are hydrologically connected to Lake Champlain, posing a threat of AIS spread. Some species present in nearby waters are projected to have strong negative impacts on Lake Champlain should they be introduced, and preventing entry is the best way to avoid this. LCC is working on keeping these species out of Lake Champlain by training volunteers to monitor for them and supporting Early Detection and Rapid Response protocols.

Carolina fanwort (Cabomba caroliniana) is a submersed aquatic plant native to South America and the southeastern United States. It is a popular aquarium plant, and aquarium dumping is suspected to be one of the main pathways of introduction to new waterbodies. Fanwort reproduces by seed and fragmentation; stems of the plant become brittle later in the growing season, which causes it to break apart and facilitates in spread. It is capable of dense growth, impeding water flow and interfering with recreation.

Hydrilla (Hydrilla verticillata) is is considered one of the most invasive species in the world. It was released from aquarium trade in Florida in the 1950s and has invaded many waterbodies since, including in New England and New York. Hydrilla has small leaves whorled around a simple stem, and tolerates a wide range of environmental conditions. It spreads primarily through fragmentation and can grow extremely aggressively once introduced. Brazilian waterweed (Egeria densa) is an AIS similar in appearance with populations in New York. It has a slightly narrower range of preferred environmental conditions than hydrilla but can also grow in dense stands. This guide from the Ausable Freshwater Center helps distinguish the species from each other and from native lookalikes. 

Quagga mussels (Dreissena bugensis) are small freshwater mollusks similar to zebra mussels in appearance and in their impact on aquatic systems. Introduced to the Great Lakes through ballast water via the St. Lawrence Seaway in the 1980s, they have since caused severe ecological damage in waterbodies in which they have invaded. They consume large portions of microscopic life that forms the base of the food web, alter water chemistry, and grow prolifically. Quagga mussels can colonize a range of substrates, capitalizing on soft surfaces like sand or silt that zebra mussels don't grow on--they outcompete zebra mussels in some waterbodies where they are both established. Learn more about invasive mussels here.

Round goby is a fish species native to the Caspian and Black Sea regions. First found in North America in the St. Clair River in 1990, they were likely introduced to the Great Lakes from a ship's discharged ballast water. Gobies are bottom-dwelling fish that perch on rocks and substrate. They grow up to 10 inches long and have large heads, soft bodies and dorsal fins that lack spines. Often confused with sculpins, the round goby is distinguished by its fused pelvic (bottom) fin which forms a suction disk that allows them to anchor to the bottom. No fish native to North America has this feature. Round gobies are predators of many native fish such as darters, sculpins, and logperch. Populations of some of these species have seen substantial declines in the St. Clair River. They also eat eggs and fry of lake trout and eggs of lake sturgeon. Round goby can harbor the bacterium that causes avian botulism; this is transmitted to the birds that eat them and has been implicated in major die-offs of birds in the Great Lakes.

LCC’s Aquatic Invasive Species Identification Cards highlight sixteen aquatic invasive species (AIS) – twelve plants, three mollusks, and one fish – that pose a significant threat to Lake Champlain. Of these, some are AIS “watchlist species” not yet detected in Lake Champlain as of 2025 but present in nearby waterbodies and posing a threat of introduction. Others are AIS “target species” that have been detected in Lake Champlain, whose spread LCC is working to prevent. The ID cards provide helpful information for identifying these species and understanding their threats to Lake Champlain. Thanks to Watersheds United Vermont for funding the development and first printing of the ID cards in 2025.

Other useful AIS guides and resources:

• Cornell University Cooperative Extension and New York Sea Grant – NYS Invasive Clearinghouse
• The Lake Champlain Basin Program - The Lake Champlain Basin Aquatic Invasive Species Guide
• New York Dept. of Environmental Conservation Invasives – Speaker Series (YouTube channel)
• United States Geological Survey (USGS) - Nonindigenous Aquatic Species
• University of Vermont - Vermont Invasives Gallery of AIS
• Vermont Dept. of Environmental Conservation - Aquatic Invasives Species
• Vermont Dept. of Environmental Conservation - A Key to Common Vermont Aquatic Plant Species

• Facillitated the discovery of the first confirmed golden clam (Corbicula fluminea) in Lake Champlain. A CHAMP volunteer found it during a survey in Whitehall, NY.
• Created CHAMP - a community science volunteer monitoring program to survey and track aquatic invasive species in Lake Champlain.
• Worked to secure ongoing funding for control of water chestnut populations.

• Developed management plans for the basin's invasive species as a member of the Lake Champlain Basin Aquatic Nuisance Species Task Force.

   

• Sought innovations to limit the amount of pesticide needed to control sea lamprey in Lake Champlain as a member of the US Fish and Wildlife Service Alternative Sea Lamprey Control Task Force.
• Helped develop a plan for rapidly responding to new invaders as they arrive and are discovered.
• Provide educational materials to help community members stop invasive species. 
• Successfully advocated for regulations and fines to make the transport of invasive species a crime. 
• Promoted baitfish regulations to minimize invasive species introductions. 
• Led efforts to initiate the rapid response plan when Asian clams were discovered in the Champlain Canal.
• Undertook vegetation surveys in Missisquoi Bay and the Northeast Arm to assess the prevalence of invasive species and conduct rapid response against any new populations found.