photo of zebra mussels

Zebra mussels, Dreissena polymorpha, are tiny, ranging from approximately 1/64th of an inch (0.5 mm) to 2 inches (50.80 mm), bivalve mollusks that inhabit fresh to brackish or even estuarine waters. Each mollusk is patterned with dark and light stripes on the small shell, which gives this non-native species its name. Zebra mussels are native to Eastern Europe, and it is believed that the planktonic larvae were transported in cargo-ship ballast water to the Great Lakes Region in the mid-to-late 1980’s where they have become an invincible problem to industry and the native species of the area.

Since zebra mussels are filter feeders, they tend to be stationery, using thin and strong threads (called byssal threads) to adhere to many different surfaces. The planktonic larva, known as a veliger, is the free floating stage of the lifecycle. This dispersal mechanism permits the zebra mussel to locate and attach to virtually anything and quickly colonize, growing into layers, often inches thick. They attach themselves to any hard surface which includes: water intake pipes, buoys, and channel markers. They even attach to native freshwater mussels, clams, and crayfish, limiting their ability to move and often smothering them.

At this time, there are relatively few ways to control zebra mussels and/or prevent them from traveling further into the interior of the United States. While biologists are testing many different types of chemical controls such as chlorine, bromide and molluscides, they are finding that these solutions are only temporary and also can affect other marine organisms. Recently, a population of zebra mussels in a freshwater quarry in Virginia was successfully eradicated using potassium chloride treatment. More information on this project is found on the Virginia Department of Game and Inland Fisheries website. Alternatives to chemical control include: hand scraping, ultra violet light, and power washing, but these control methods are often expensive and tedious. Zebra mussels are here to stay.

To avoid accidental introduction of zebra mussels to significant Maryland waters, any live bait used in Prettyboy, Loch Raven, Tridelphia or Liberty reservoirs must be from zebra-mussel-free sources. Inquire if your bait dealer can confirm zebra-mussel-free certification before purchasing live bait for these locations.

It is illegal to import or possess live zebra mussels or their reproductive products for any purpose in Maryland, including scientific research, without written permission from the Secretary of the Department of Natural Resources. Contact Richard Bohn, permit coordinator for the Fisheries Service, at 410-260-8317 (Toll-free: 1-877-620-8DNR ext.8317) before importing any zebra mussels into Maryland.

Potential Proposal To Address Specific Nonnative Species

Photo credit: GLSGN Exotic Species Library. Organization: U.S. Fish and Wildlife Service

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Date page was last updated: 04/21/2009

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