Upper Midwest Environmental Sciences Center
November 17, 2000
Zebra Mussels Why are they a problem? Because they attach themselves to hard surfaces and can produce millions of offspring annually, Zebra mussels have caused drastic declines in native clam and mussel populations in some locations. Zebra mussels compete with other invertebrates and young fish for plankton, the primary food source for these groups. Industries that use river water for cooling and other uses spend millions of dollars annually for cleaning intake structures clogged by the mussels. Fast Facts How far have they spread? Origin: Caspian Sea region
Preferred habitat: Fresh water with hard substrates
Size: up to 50 mm
Method of introduction: Ballast discharge from oceangoing ships
Zebra mussels were discovered in Lake St. Clair near Detroit in 1988. They have now spread to parts of all the Great Lakes and the Mississippi River and are now appearing in inland lakes.
See the progression of zebra mussels from June 1988 to February 1998.
What are UMESC scientists doing to help?
Zebra mussel samplers after removal from the Upper Mississippi River. The wire cage prevented fish from eating mussels on that block.
The UMESC scientists are investigating the effects zebra mussels are having on the riverine ecosystem. One study examined the effects of fish predation on zebra mussels. After examining the stomach contents of fish found near zebra mussel samplers, the investigators concluded that at least five fish species are consuming zebra mussels in the Upper Mississippi River. Other scientists have researched how zebra mussels have altered the distribution and migration routes of diving ducks.