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Zebra and Quagga Mussel

Zebra (Dreissena polymorpha) and quagga (D. bugensis) mussels cost the U.S. economy up to $1 billion each year. These invasive aquatic animals clog drinking water intakes; foul boat hulls, motors, and equipment left in lakes. Their sharp shells litter beaches. They harm native fish by consuming food and often kill native mussels, crayfish, and snails through fouling.

In the late 1980s and early 1990s, these invasive mussels spread from Europe to the Great Lakes in contaminated ballast water discharged from foreign ships. From there, they expanded to the Mississippi River, its tributaries, and to inland lakes. They spread primarily by attaching to boat hulls, aquatic plants, docks and lifts. Adults can survive out of water for days under certain conditions. Your actions are vital to prevent their spread.

Identify Zebra and Quagga Mussels



lineart of zebra and quagga mussel

General Characteristics

  • Zebra and quagga mussels look like small clams with a yellowish or brownish "D"-shaped shell, usually with dark and light-colored stripes
  • They can be up to two inches long, but most are under one inch. They usually grow in clusters containing numerous individuals and are generally found in shallow (6-30 feet), algae-rich water
  • Only freshwater mollusc that can firmly attach itself to solid objects – submerged rocks, dock pilings, boat hulls, water intake pipes, etc.
  • Small attached mussels are difficult to see
  • Newly settled mussels may only be 1/8" long

What You Can Do

Follow Minnesota Aquatic Invasive Species Laws:

  • Clean all aquatic plants, animals and mud from watercraft, trailers, docks, lifts, anchors and other recreational equipment before leaving access.
  • Drain water-related equipment (boat, ballast tanks, portable bait containers, motor) and drain bilge, livewell and baitwell by removing drain plugs before leaving water access. Keep drain plugs out while transporting watercraft.
  • Dispose of unwanted bait, worms and fish parts in the trash.

Also Recommended:

  • Spray watercraft and equipment with high-pressure water, or
  • Rinse with very hot water, or
  • Dry for at least 5 days.

Report New Sightings — note exact location; place specimens in a sealed plastic bag; and call a Minnesota DNR Invasive Species Specialist (see www.mndnr.gov/invasives/contacts.html), 1-888-MINNDNR or (651) 259-5100; or the MN Sea Grant Program in Duluth, (218) 726-8712.

Know the rules!

Specimens are needed to confirm sightings, but some jurisdictions prohibit possession of thesemussels and other invasive animals and plants. InMinnesota, possession and transport of any Dreissena is illegal, exceptwhen providing themto SeaGrant or DNR for identification. Unauthorized introduction of invasive mussels, fish or plants into the wild is illegal. Protect your property and our waters.

Related Content:

Zebra Mussel

Quagga Mussel

Zebra and Quagga Mussel


This page last modified on May 04, 2016     © 1996 – 2017 Regents of the University of Minnesota     The University of Minnesota is an equal opportunity educator and employer.
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