Rusty Crayfish: Native to the Ohio River Basin in the U.S.; believed to be the result of anglers discarding crayfish used as bait. Eat large amounts of aquatic vegetation; aggressive nature helps protect them from native fish.
Spiny Water Flea: Microscopic creatures native to Europe and Asia; eat small animals (zooplankton), including daphnia, an important food for native Great Lakes fish.
Round Goby: Bottom-dweller native to central Eurasia that can displace native fish, eat their eggs and young, take over habitats, spawn multiple times a season, and survive poor-quality water. Also eats zebra mussels and quagga mussels.
Tubenose Goby: Similar to the round goby but doesn't feed on invasive mussels.
Rudd: A European minnow that competes with native species for limited resources.
Ruffe: Native of Eurasia and a member of the perch family; can seriously damage native sportfish populations by directly competing for food, habitat or through heavy predation of native sportfish eggs.
Sea Lamprey: Native to the north Atlantic and the Baltic; large eel-like fish that attaches to native fish and sucks their blood. During parasitic phase, a sea lamprey can destroy an average of 18 kilograms of fish.
White Perch: A member of the bass family from Atlantic coastal region, white perch compete with Great Lakes species and can cause declines in fish populations by eating eggs of walleye and other fish species.
Zebra, Quagga Mussels: Freshwater bivalves from Black Sea region of Eurasia. Heavily colonize hard and soft surfaces — docks, boats, breakwalls and beaches. Often clog intake structures in power stations and water treatment plants.
Source: The Great Lakes Information Network