Zebra Mussels (Dreissena polymorpha)


Live zebra mussels underwater

Credit: Wikimedia Commons


Zebra mussel

Credit: U.S. Geological Survey

Where did zebra mussels come from?

  • Zebra mussels are believed to have come from the Caspian Sea in Europe.
  • They arrived in the late 1980s in the ballast water of ships.
  • Zebra mussels have spread to 20 of the United States and the Provinces of Ontario and Quebec.
  • First found in Lake St. Clair, they have spread south to the Gulf of Mexico and north into southern Canada.

What do zebra mussels look like?
  • Zebra mussels can be up to two inches (50 mm) long.
  • They have striped shells that look like a zebra’s stripes, which is how they get their name.
  • Zebra mussels can live for four to five years.
  • Zebra mussels also have sticky byssal threads that they use to attach tightly to any hard surface.

Why are zebra mussels a problem?
  • Zebra mussels are a problem because they filter water, up to a liter per day, to eat the plankton. Since the zebra mussels eat a lot of plankton, they compete with fish for food.
  • They also clog pipes by forming colonies inside of the pipes. Then the water cannot flow through the pipes as easily.
  • The cost to Great Lakes' utilities to control the zebra mussels in water intake pipes from 1989 to 2004 was $267 million (Connelly, et al 2007).

How do zebra mussels spread?
  • Zebra mussels can reproduce by the end of their first year.
  • They usually spawn in the early spring until winter, when the water temperature is about 68*F.
  • A fertilized egg results in a free-swimming planktonic larva called a veliger.
  • Veligers are about the diameter of a human hair and are so small you can’t see them without a microscope.
  • The veliger floats in a water column for 1-5 weeks and then as it grows it begins to sink and search for a hard surface on which to live and grow.

How do we control zebra mussels?
  • Zebra mussels cannot be controlled in the wild.
  • On intake pipes, chemicals can be used that will kill the larva.If these chemicals were used in an open lake, they would also affect fish and native mussels.
  • The spread of zebra mussels can be prevented by draining all of the water from boats, live wells and bait wells.
  • Thoroughly inspect your boat’s hull and trailer for any zebra mussels and weeds.
  • Let equipment sit for 4-5 days or rinse with hot water.
  • Never take fish or plants from one lake and put them in another.






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