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AIS in the Lake
Aquatic invasive species (AIS) include include plants, animals, and pathogens that may be intentionally or unintentionally introduced to the Basin. Nonnative species—species that were not present at the time of European settlement—were first documented in Lake Champlain as early as 1840. As of 2012, 49 known aquatic non-native and invasive species have been identified.
The Lake Champlain Basin Program was a key partner in the development of the 2005 Lake Champlain Basin Aquatic Nuisance Species Management Plan, along with the states and many other groups. The plan sets priorities for AIS control and management and is eligible for U.S. Fish and Wildlife Service funding to support programs such as water chestnut control and boat launch stewardship.
- Asian Clam
- Eurasian Watermilfoil
- Japanese Knotweed
- Purple Loosestrife
- Water Chestnut
- Zebra Mussel
Other species, while not identified in the plan, are of particular concern to managers:
More on Aquatic Invasive Species
For the latest information on AIS, please visit the “What new aquatic invasive species have invaded the Lake” section of our State of the Lake website.
To learn about actions taken to address AIS, please visit the “Managing Aquatic Invasive Plants and Animals” chapter in the Lake Champlain Management Plan Opportunities for Action.
For additional information and maps, please visit the Lake Champlain Basin Atlas.
- Lake Champlain Basin Aquatic Invasive Species Guide
- NY Invasive Species Speaker Series (YouTube Channel)
- Aquatic Invaders Brochure (Spread Prevention Tips)
- Baitfish of Vermont Including Lake Champlain (VTFWD)
- New York Invasive Species Clearinghouse (Cornell University Cooperative Extension and NY Sea Grant)
The alewife (Alosa pseudoharengus) is a marine fish species from the herring family that is native to the Atlantic Ocean. Each spring, adult alewives migrate into freshwater rivers to spawn. The young hatch in the rivers, reside there for the summer, and then migrate out to sea in early fall where they mature as adults. Alewives can, however, live and reproduce in freshwater. Alewife populations have become established in Great Lakes and many landlocked lakes in New York, Maine, Connecticut, and other New England states.
In 2003, alewives were confirmed in Lake Champlain when several juvenile fish were found during a yearly forage fish survey by Vermont Fish and Wildlife Department. The number caught in subsequent surveys has increased. A widespread alewife die-off in 2008 (and smaller die offs since) confirmed that large numbers are now present. Although alewives do undergo periodic mass mortality events, the specific cause of the Lake Champlain die-offs is unclear. Long-term monitoring conducted by the Vermont Department of Fish and Wildlife since the 1990s has shown that alewife have become the dominant forage base in the Lake, replacing rainbow smelt. Research has shown that alewife growth rates in Lake Champlain are higher than those observed in the Great Lakes populations, suggesting that alewife populations are still expanding in Lake Champlain.
Alewives threaten the native species of Lake Champlain and other Basin waters by altering zooplankton communities, competing with other fish for food, and feeding on native fish eggs and larvae. They also pose a threat to lake trout and Atlantic salmon who can experience reproductive failure when feeding on an alewife diet due to a severe thiamine (vitamin B) deficiency. Alewives in Lake St. Catherine have led to decreased water clarity and a threatened smelt population. In February 2006, the LCBP and Lake Champlain Sea Grant co-hosted a Lake Champlain Alewife Impacts workshop to assess the potential impacts of the fish.
More on Alewife
- Alewife Factsheet (VT DEC)
The Asian clam (Corbicula fluminea) is hermaphroditic bivalve that is native to tropical areas in Asia, the eastern Mediterranean, and Australia. Their shells are brown or yellow-green with thick concentric rings on the outside and smooth with a purple tinge on the inside. They are generally smaller than a penny in diameter, but can reach sizes of up to 5cm. Unlike zebra mussels, which colonize on hard surfaces, the clams prefer open, sandy bottom areas with limited plant growth, where they can form dense, thick mats. Asian clams usually reproduce twice annually with one clam capable of releasing up to 2,000-4,000 offspring each cycle. The literature suggests that water temperatures must rise above 59 degrees Fahrenheit (15 degrees Celsius) for the clams’ reproductive cycle to become active.
The Asian clam was first found in the Lake Champlain Basin in August 2010. After its initial discovery in Lake George by a researcher at Rensselear Polytechnic Institute’s Darrin Fresh Water Institute (DFWI), scientists found that the invasive mollusk had colonized nearly six acres of lake bottom near the Village of Lake George. Experts believe that the clams had been in the lake for two to three years before discovery and had possibly completed four to six reproduction cycles. As a result, the clams formed mats with densities of up to 8,000 clams per square meter. It is unknown how Asian clam reached Lake George, but potential vectors of introduction include an aquarium dump, live bait or juvenile transport in water in a boat or in recreational equipment.
The Asian clam is a filter feeder that excretes fecal matter into the water. Research conducted in Lake Tahoe suggests the clams are associated with algal blooms and their presence may change the water chemistry, possibly providing a calcium-rich breeding ground for other potential invasive species such as zebra or quagga mussels. The Asian clam crowds out native species and reduces biodiversity on the lake bottom. Asian clams can clog water intake systems of boats, homes, drinking water, industry, and municipalities.
The Lake George Asian Clam Rapid Response Task Force was quick to launch efforts to eradicate the clam. A pilot project in fall 2010 found that the installation of benthic barrier mats on the lake bottom—which cuts off the oxygen supply and smother the clams—was the most effective method of combating the infestation. Additional surveys of the lake have found a total of eight additional infestation sites; these sites have been treated with a combination of benthic mats and suction harvesting. The Task Force is working to determine the best course of management action to eradicate new smaller sites and contain other sites for long term management.
More on Asian Clam Management
For press releases, photographs, and reports please visit the Lake George Asian Clam Eradication Project website.
Didymo (Rock Snot)
Didymo (Didymosphenia geminata), or “rock snot,” is a freshwater algae native to cool temperate regions of northern Europe and northern North America. Didymo cells attach to stream beds with a fibrous stalk, forming dense mats with a texture similar to wet wool and mimicking strands of toilet paper (as opposed to the slimier feel of other algae species). Research has not shown significant impacts to salmon and trout, but a few studies have shown that didymo can alter local macroinvertebrate species diversity at a bloom site.
Didymo was confirmed in the Lake Champlain Basin in the Mad River in July 2008 and the Gihon River in June 2010 by the Vermont Agency of Natural Resources. In June 2007, didymo was found in the upper reaches of the Connecticut River and soon after in the White River. In August 2007, a small infestation was reported in the lower Battenkill River.
Because its microscopic cells can cling to boats, waders, fishing gear, sandals, and anything else that comes in contact with water, Didymo easily can be spread unintentionally by river users. Gear must be dried for a minimum of 48 hours or cleaned with a bleach solution to get rid of the algae.
The Ausable River Association in New York and the Mad River Association in Vermont have worked proactively to prevent the introduction of Didymo into their watersheds. River stewards monitor popular river recreation sites, discussing Didymo and the threat of aquatic invasive species transport on gear and equipment. In 2011, Vermont passed a law that prohibits the use of felt soled waders and boots.
More on DIdymo
Eurasian watermilfoil (Myriophyllum spicatum), first discovered in the Basin in 1962, is found in a number of areas in the Lake and Basin. In some areas infestations are severe; however the majority of these infestations are light or moderate. Detailed watermilfoil studies have been conducted for many of Lake Champlain’s bays and for 41 other lakes within the Basin and many other water bodies, but many areas have little or no study regarding the extent of infestation. Because Eurasian watermilfoil is primarily spread by plant fragments transported by waves, wind, currents, people, and to some extent, animals, and is a perennial, it is not easily controlled.
Controlling Eurasian watermilfoil is costly. Millions of federal, state, and local funds (excluding salaries and administrative costs), and thousands of volunteer hours have been spent on controls in New York and Vermont lakes and ponds since 1982. Control mechanisms that have been employed in the Basin include mechanical harvesting, diver-operated suction harvesting, installation of benthic barriers, fragment barriers, handpulling, hydroraking and herbicides. Use of biological controls such as the release of a species of aquatic weevil are experimental at this time.
More on Eurasian Watermilfoil
Japanese knotweed (Polygonum cuspidatum) was first introduced to the United States as an ornamental plant in the late 1800s because of its appealing flowers. It was also used for erosion control because of its rapid and prolific growth. It has subsequently spread into the wild across the majority of the United States, including the Lake Champlain Basin. It spreads via underground rhizomes that easily fragment and spread to other areas. This is especially problematic along streambanks and in riparian zones where natural forces contribute to the spread of knotweed.
Japanese knotweed has already altered the natural characteristics of the Lake Champlain Basin’s riparian zones. Knotweed grows early in the season and is very dense which excludes the growth of the Basin’s native plant species, decreasing diversity and altering wildlife habitat. It is also quickly rebounds from disturbances such as flooding. In the fall, when the plant dies back, the dead stems and leaf litter form a dense mat that decomposes slowly, further inhibiting native plant growth. Dense growth in riparian zones also excludes recreational uses such as swimming, fishing and boat access. When dense stands are removed from river banks there is an increased risk of erosion until native plants are able to reestablish themselves.
Japanese knotweed continues to spread throughout the Lake Champlain Basin. The spring flooding in Lake Champlain in 2011 and more frequent and intense storms such as tropical storm Irene and Lee in 2012 was the cause for significant spread of this species along the lake shoreline and along stream corridors.
While there are several methods to control knotweed, they are expensive and generally require intensive labor and reapplication. Despite the fact that some people enjoy the taste of the young shoots and the appearance of the plant as an ornamental, it is an undesirable resident of the Basin.
More on Japanse Knotweed
Purple loosestrife (Lythrum salicaria) is native to Eurasia and has been present in New England for almost 100 years. It now can be found throughout the temperate portions of the United States and Canada. It has no natural predators in North America.
Although it adds vibrant swaths of color to the Basin’s roadside ditches and wetlands, purple loosestrife is an unwanted alien to this region. It crowds out native wetlands and vegetation such as cattails, grasses, sedges, and rushes, and is of little or no value to wildlife. Loosestrife is quick to invade many habitats, including wet meadows, marshes, river banks, and the edges of ponds and reservoirs. Gardeners can accidentally increase its spread by planting it in home gardens. Even sterile varieties, often sold by nurseries, are now considered a problem and should never be planted
The VT DEC, APIPP and other NY partners have been working for several years to determine whether an introduced beetle (Galerucella) that eats loosestrife can help control the plant’s spread. This beetle has been placed in several test wetlands throughout Vermont and New York and has shown promising results.
More on Purple Loosestrife
The rusty crayfish (Orconectes rusticus) is a species native to Ohio and Tennessee but is spreading to many other parts of the country including New York and all New England states (except Rhode Island). They have been found in Lake Carmi and were spotted in the lower Winooski River in 2005. Rusty crayfish typically displace or hybridize with native crayfish populations and opportunistically prey on native plants, benthic invertebrates, fish eggs, and small fish. Their aggressive predation of native species decreases diversity, destroys habitat, and has an overall negative impact on many aquatic ecosystems. Rusty crayfish may also spread Eurasian watermilfoil by fragmenting the plants and defoliating native flora which clears the way for further milfoil infestation.
There are currently no successful management techniques for rusty crayfish once a population is established.
More on Rusty Crayfish
Tench (Tinca tinca) are native to Europe and similar to carp that live on lake or river bottoms. They are a slimy, slow moving carnivorous member of the minnow family that prefers tranquil, shallow water and weedy areas where they feed on invertebrates. In Europe, the tench is harvested and consumed by people.
The tench was first caught and identified by two fishermen on the Great Chazy in New York in May 2002. Brian Ellrott from UVM’s Rubenstein Science Lab and Drew Price from the Center for Lake Champlain caught the 20- inch specimen near the lamprey barrier dam on the Chazy River. It is unknown how the tench found its way to the Great Chazy, although the Richelieu River already has a viable tench population.They are now found throughout northern Lake Champlain.
It is too early to tell the effects of the tench on Lake Champlain’s native species. Female tench may lay up to 600,000 eggs annually. The tench has a tendency to cloud the water where it lives by stirring up the bottom sediments. These fine sediments can suffocate the eggs and newly hatched fish of native species such as pike, perch or crappie.
More on Tench
Variable-leaved watermilfoil (Myriophyllum heterophyllum) is native to the southern portions of the United States. It can crowd out native aquatic plants and can impede boating, fishing, and swimming. It spreads by stem pieces, roots, and seeds, and “hitchhiking” on boats and recreational equipment.
VLM was confirmed in the southern end of Missisquoi Bay in Lake Champlain in September 2009 and subsequently in the southern end of Lake Champlain in summer 2011. It is also distributed through several lakes in the Adirondack Park. Like Eurasian watermilfoil, variable-leaved watermilfoil is an aggressive, rapidly-growing nonnative species.
More on Variable-Leaved Watermilfoil
European water chestnut (Trapa natans) is an annual plant that can form dense mats, limit boat traffic and recreational use, crowd out native plants, and create an oxygen depleted zone uninhabitable to fish and other organisms. Is of little food value to wildlife. The plant must be controlled each year before its seeds drop to the lake bottom where a small percentage can remain viable for up to twelve years.
First documented in Lake Champlain in the 1940s, water chestnut is a high priority species for management, and notable progress in controlling it has been made. Since the 1960s, its local range has fluctuated in correspondence with management funding levels. It was nearly eradicated by the early 1970s, but lack of consistent control allowed water chestnut to expand its range. Water chestnut is known to occur in two places in Lake Champlain in 2011, but it has also infested other inland water bodies in the Basin. The largest infestation is in the south lake of Lake Champlain. By 1997 it was found 52 miles north of Whitehall. A Pike River infestation has been eradicated as of 2007 and a Missisquoi National Wildlife Refuge population is under careful management.
The South Lake population is aggressively managed by mechanical and hand harvesting methods. A management program begun in 1998 with an average annual budget of $500,000 has greatly reduced this population. Due to the program’s success, mechanical harvesting was needed only as far north as the Dresden Narrows, VT by then end of 2012. Remaining areas are managed by handpulling.
More on Water Chestnut
White Perch (Morone americana) are a relatively new nonnative invasive species of increasing concern in the Lake. In 2003, Québec researchers found that white perch far outnumbered native perch in Missisquoi Bay and are now the Bay’s most abundant fish. White perch are now found throughout Lake Champlain and in the lower sections of its tributaries. They may displace native perch by feeding on their larvae and compete for zooplankton which can lead to an increase in algal growth. White perch are also known to prey on walleye eggs along with white crappy, which has contributed to the significant decline in the walleye population.
More on White Perch
The zebra mussel (Dreissena polymorpha) is a small freshwater mollusk native to the Caspian and Black Sea regions of Eurasia. They are thought to have been transported to North America in the ballast tanks of ships. Since their arrival in the Great Lakes around 1986, zebra mussels have resulted in millions of dollars of damage and lost revenues.
Adult zebra mussels have spread throughout nearly all of Lake Champlain since they were first found in 1993. Fewer mussels are found in Missisquoi Bay where refuges of native mussel populations are holding on but are increasingly threatened. In 1999, adult zebra mussels were also found in Lake George, NY near Lake George Village and in Lake Bomoseen, VT. Zebra mussel veligers have been found in Lake Dunmore, Hortonia, and Carmi, but no adults have been found to date.
Zebra mussels can clog residential, municipal and industrial water intake pipes, foul boat hulls and engines, cover recreational beaches and lake bottoms cutting the feet of swimmers, and obscure underwater and archeological artifacts. Zebra mussels take over spawning habitats for Lake Trout, Smelt, and other fish. They consume microscopic plants and animals in large quantities, in competition with juvenile fish and native mussels. This also has the effect of increasing water clarity, which has some benefits, but can aid the spread of invasive plants to deeper areas of the lake. Zebra mussels have begun to kill many of Lake Champlain’s native mussels by attaching to their shells, preventing them from opening to feed and respire. Seven mussel species native only to the Basin are now severely threatened.
Because no effective zebra mussel control methods exist, efforts are focused on education to slow their spread to other lakes. Management actions have focused on controlling the mussels’ attachment to surfaces and water intake pipes and on preventing further spread. The impacts of zebra mussel infestations on the ecosystem and underwater cultural artifacts are also not well understood, but ongoing worldwide research may offer some understanding of possible effects.
More on Zebra Mussels