Location: Zumbro River near Rochester, Minnesota
Last week, I spent a rainy morning fishing on the Zumbro River. As I waded upstream, my water shoes crunched on a carpet of shells. Zebra mussels (Dreissena polymorpha), an invasive freshwater species, covered the river bottom. Zebra mussels originated in the Balkans, Poland and Russia. In 1988, a ship unknowingly carried them in ballast water across the Atlantic, and then discharged them in Lake St. Clair, between Lake Huron and Lake Erie.
These inch-long mollusks get their name from the striped pattern on their shells, and like their namesake mammal, the shell patterns vary greatly and are sometimes not present. Young zebra mussels swim in water currents. Older ones spread by attaching themselves to boats and wildlife such as turtles and crayfish.
So what’s the problem? Hydro-power plants spend millions each year to keep zebra mussels out of intake pipes, the cost of which gets passed on to you and me. These prolific mollusks anchor on native mussels, killing them. They eat algae, which makes water seem cleaner, though all it really does is steal food from bottom-of-the-food-chain creatures. The water may look clearer, but they do not remove pollutants.
You can help prevent the spread of zebra mussels by not transporting aquatic plants and wildlife to other water sources. Wash your boat. If you go fishing, clean your gear, empty water wells and bait buckets on dry land and throw your leftover bait in the trash.