California Sea Grant College Program

Zebra mussels (Dreissena polymorpha) are pistachio-sized freshwater bivalves native to the regions around the Black and Caspian seas. Since their discovery in Lake St. Clair, Michigan, in the late 1980s, they have spread distressingly fast through the Great Lakes and Mississippi River basin, as well as to other lakes and rivers in the eastern United States and Canada.