Invasive Species of Concern in Maryland

ANNAPOLIS, MD - The zebra mussel, a small freshwater mollusk from the Caspian Sea, has infested much of the Great Lakes region, causing devastating economic and ecological damage. Now scientists fear that Maryland may become the next victim in the spread of this harmful exotic species. To heighten awareness about the threat and preventative actions boaters can take to help keep the invader away, the Maryland Invasive Species Council has named the zebra mussel the invader of the month.

Since its inadvertent introduction into the Great Lakes in the mid-1980s, the zebra mussel has spread rapidly into freshwater habitats from Louisiana to New Hampshire.

"The rate of spread of this species is nothing short of astounding" says Dr. Ron Klauda, a biologist with the Maryland Department of Natural Resources (DNR). "There are now populations in neighboring states Pennsylvania, Virginia, and West Virginia. We want to keep them out."

Zebra mussels have encrusted boats, ruined power plant intakes, and changed the way municipal water systems operate. Free-swimming zebra mussel larvae will stick to any hard surface. As the larvae grow up, they literally clog water systems. Ecologically, zebra mussels are killing native mussels, including endangered species. They have been connected with widespread ecological impacts from increasing toxic microorganisms to declining duck populations.

Klauda notes that the species is moving rapidly throughout the St. Lawrence and Mississippi River systems, in part because of its free?swimming larvae being moved by currents. But the main mechanism for its transport up rivers and to inland lakes is by hitchhiking with people.

"Recreational boaters can inadvertently carry larval zebra mussels around in their bilge, in minnow buckets, or on aquatic vegetation on their trailer" says Klauda. In Minnesota and a number of other states, fishermen and boaters have been very effective in halting the spread of this serious pest by a little preventative maintenance. Maryland now hopes that local boaters will get on board by washing down hulls, cleaning bilges and removing aquatic vegetation from props and trailers when returning from potentially infected waters, and not bringing back bait when fishing out of state. Maryland DNR has teamed up with the Chesapeake Bay Trust to post signs at all Maryland Boat ramps to inform Maryland boaters about the problem and how they can avoid being carriers.

The stakes are high for uninfected areas. New York state alone figures its losses between 1993 and 1999 at over $5 billion, even without accounting for ecological damage.

"Places like Deep Creek Lake have a lot to lose if the zebra mussels get in and rewire the ecosystem" says DNR's Klauda. "Our hope is that people will realize that and take a few simple steps to prevent serious economic and ecological misfortune."

For more information about zebra mussels and other Invasive Species of Concern, visit or call DNR at 410.260.8539.
photos available electronically on request