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Recent estimates suggest that there are over 600 aquatic and terrestrial non-native species present in the Great Lakes region. With no natural enemies to limit their spread, these species have the ability to invade and displace native species, spread disease and alter ecosystem dynamics. Of these, only a small percentage creates serious problems. Where they do, these problems can be costly and can wreak havoc on natural areas. Lake St. Clair has been particularly vulnerable - because the lake is shallow, ships discharge ballast water as they pass through, releasing such invasive species in the process.
The zebra mussel, native to the Caspian Sea region, was first discovered in Lake St. Clair in 1988. Since then, it has spread to all five Great Lakes. Because zebra mussels attach themselves in barnacle-like colonies to water intake screens and restrict water flow, they have caused extensive problems for industries and municipalities that rely on large-scale water withdrawals from Great Lakes. The ecology of native mussel communities changed substantially after the invasion of the zebra mussel. Native mussels were unable to adequately compete with the zebra mussel and virtually all of the 18 native species have been extirpated from the open lake. Zebra mussels effectively filter water at relatively high rates and have consequently increased water transparency, particularly on the Ontario side of the lake. An additional concern with zebra mussels is that they may bioaccumulate contaminants that could then be passed to predators, many of which are popular sport and commercial fish species.
Sea Lamprey are a primitive, jawless fish native to the Atlantic Ocean. They have a large mouth designed for sucking and a well developed sense of smell. Sea lamprey first appeared in Lake Ontario in the 1830's and eventually spread throughout all of the Great Lakes. Sea Lamprey attach to fish with their sucking mouth and sharp teeth, and suck out their prey's body fluids. This often kills the prey, and is one of the reasons why the lampreys have had an enormous negative impact on Great Lakes fishery . Sea Lamprey were a major cause of the collapse of lake trout, white fish and chub populations in the Great Lakes during the 1940s and the 1950s.
Round and tubenose gobies are bottom-dwelling fish that were discovered in the St. Clair River in 1990. Round goby are aggressive, voracious feeders that can forage in total darkness. The round goby takes over prime spawning sites traditionally used by native species, competing with native fish for habitat and changing the balance of the ecosystem . Gobies can also survive in degraded water conditions, and spawn more often and over a longer period than native fish. They are found in high abundance in the St. Clair River and Lake St. Clair and are also common along the tributaries to the lake and river. In Lake St. Clair, round gobies have become an important component of the diet of muskellunge, smallmouth bass and yellow perch.
The Great Lakes Panel on Aquatic Nuisance Species engages in ongoing efforts to prevent and control the occurrence of aquatic nuisance species in the Great Lakes.
For more information, see: Coastal Habitat Plan, Section V (PDF)