For many aquatic nuisance species, preventing introduction to the Lake Champlain Basin is our only hope. Extermination or spread prevention of established invasive species is often expensive and dificult, if not impossible. For these reasons, it is important that we familiarize ourselves with the nonnative species that threaten the Basin and do everything we can to prevent thier establishment. The following species have not yet been found in Lake Champlain, but could have significant negative impacts if introduced. The following are of concern for the Lake and/or high priority species for prevention in the Lake Champlain Basin Aquatic Nuisance Species Management Plan - 2005 (species with a *).

• Eurasian ruffe*
• Hydrilla*
• Quagga Mussels*
• Round Goby*
• Rusty Crayfish
• Fishhook & Spiny Waterfleas*
• Didymo (Rock Snot)

The Eurasian ruffe (Gymnocephalus cernuus) is a nonnative nuisance species of fish that threatens the ecosystem and sport fish population of Lake Champlain. The ruffe was first found in Lake Superior in 1986 and has since expanded its population and range substantially. It is a perch-like fish native to Eurasia that usually grows no bigger than six inches.

Ruffe impact native species and sport fish populations by preying on their eggs and competing for food and habitat. They are highly competitive because they mature quickly, have high reproductive potential, and are adaptable to a wide variety of habitats due in part to their tolerance of poor water conditions. Studies have shown decreases in native fish populations where ruffe populations have established.

• Ruffe Information and Links (University of Minnesota)
• Ruffe Pictures & Distribution Map (USGS)
• Ruffe Fact Sheet (Army Corp of Engineers)

Hydrilla (Hydrilla verticillata) is a nonnative aquatic plant that is spreading across fresh waters of the northeast. Hydrilla was first introduced to the United States as a popular aquarium plant, which was then accidentally released into the wild in Florida. Hydrilla is capable of completely clogging waterways. Its vertical branches often out-compete native plants, affecting water quality and restricting flow. The widespread growth of this plant has dramatic impacts on recreational uses such as boating, fishing and swimming.

Hydrilla spreads rapidly, is adaptable to a variety of habitats, and is very difficult to control once a viable population is established. Hydrilla has been confirmed in Connecticut, Massachusetts and Maine. Hydrilla poses a serious threat to the waters of the Lake Champlain Basin.

• Hydrilla Website (University of Florida)
• Hydrilla Distribution Map & Fact Sheet (USGS)
• Hydrilla Biological Control Options (University of Georgia / USDA)

Quagga mussels (Dreissena bugensis) are a nonnative nuisance species native to the Caspian Sea area. They were first introduced to the Great Lakes in 1989 and can now be found throughout the Great Lakes, the St. Lawrence River and in a few inland water bodies in New York. They threaten the Lake Champlain Basin by having the potential to cause many of the same problems that have resulted from zebra mussels.

While the quagga mussel is a close relative of the zebra mussel, scientists believe that it poses a greater threat. Quagga mussels are able to colonize a wider variety of lake bottom surfaces than zebra mussels and are more tolerant of a greater range of temperatures, depth and other environmental conditions. In the Great Lakes, quagga mussels are already out-competing and replacing zebra mussel populations, but in greater numbers, resulting in more substantial negative impacts. Quagga mussels have the potential to significantly exaggerate the negative impacts currently caused by zebra mussels in Lake Champlain and must be monitored carefully to prevent infestation.

• Quagga Information and Control Strategies (Cornell University)
• Quagga Fact Sheet & Distribution Map (USGS)
• Quagga Impacts in the Great Lakes Article (Penn State)

Native to Europe, the round goby (Apollonia [Neogobius] melanostomus) was first found in the St. Clair River in 1990 and has subsequently expanded its distribution to many areas of the Great Lakes, the interior of New York, and the St. Lawrence River in Quebec. The goby is gray, four to ten inches in length, and is physically similar to other species native to US waters.

The round goby is a nuisance nonnative species because it out-competes native species for food and habitat by feeding at night, thriving in poor water conditions, spawning multiple times a season, and preying on native eggs and young. It has already substantially impacted recreational and commercial fisheries in the Great Lakes, resulting in seasonal restrictions on certain types of fish whose populations have been reduced by goby. While the round goby is known to eat zebra mussels, scientists don't believe that its impacts are worth the trade off. The introduction of the round goby to Lake Champlain could dramatically impact that Lake's game fish.

• Round Goby Fact Sheet (Army Corp of Engineers)
• Round Goby Distribution Map (USGS)
• Round Goby Taxonomy & Fact Sheet (Columbia University)

The rusty crayfish (Orconectes rusticus) is a species native to Ohio and Tennessee but is spreading to many other parts 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. This leaves prevention as the only option for protecting Lake Champlain from rusty crayfish infestation.

• Rusty Crayfish Fact Sheet (University of Minnesota)
• Rusty Crayfish Distribution Map (USGS)
• Rusty Crayfish PDF fact sheet with links (Indiana DNR)

Fishhook and spiny waterfleas (Cercopagis pengoi & Bythotrephes longimanus), despite their diminutive size, greatly threaten Lake Champlain. Native to Eurasia, these species were discovered in Lake Ontario in 1998 and 1992 (respectively). Both species have spread to many parts of the Great Lakes and fishhooks have spread to the Finger Lakes of New York. They impact aquatic ecosystems by competing with native fish for food. This bottom level impact on the food chain can have a dramatic impact on the overall productivity of a fishery. They also affect recreational and commercial fishing by clogging and damaging gear. The fleas' spiky exoskeletons not only snag on fishing gear but make them undesirable prey to many would-be predators, resulting in unchecked population growth.

There are currently no successful management techniques for the fishhook and spiny waterfleas once a population is established. This leaves prevention as the only option for protecting Lake Champlain from the impacts of waterflea infestation.

• Spiny Waterflea Fact Sheet and Distribution Map (USGS)
• Fishhook Waterflea Fact Sheet and Distribution Map (USGS)
• Fishhook Waterflea Fact Sheet (University of Minnesota)

In June 2007, didymo was found in the upper reaches of the Connecticut River and soon after in the White River (VT ANR News Release). In August, a small infestation was reported in the lower Battenkill River (NYSDEC News Release). Didymosphenia geminata, commonly referred to as "didymo" or "rock snot" is a freshwater algae that has invaded streams and rivers in parts of North America and New Zealand. While not much of a threat to Lake Champlain itself, didymo is a threat to the many streams and rivers in the Lake Champlain Basin—especially waters inhabited by trout and salmonid fish. Didymo forms extensive mats on stream beds, smothering plants and rocks, and other aquatic life. Didymo attaches to the streambed by a stalk. It has a rough texture similar to wet wool and mimics strands of toilet paper, as opposed to other algal species which feel more slimy.

Didymo can be accidentally spread by people using rivers, as its microscopic cells can cling to boats, waders, fishing gear, sandals, and anything else that comes in contact with water. Gear must be dried for a minimum of 48 hours or cleaned with a bleach solution to get rid of the algae. For more details on how to clean gear, please read the fact sheets below. If you think you see didymo contact the LCBP immediately!

• NYSDEC News Release on Didymo (August 7, 2007)
• Vermont ANR News Release on Didymo (July 6, 2007)
• Didymo Fact Sheet (US EPA)
• Didymo Fact Sheet (Portland State)