ANNAPOLIS, MD (April 15, 2013) - The zebra mussel, a small freshwater mollusk native to southern Russia and the Caspian Sea, was first discovered in North America in June 1988, in Lake St. Clair. Since this inadvertent introduction, zebra mussels have spread as far west in the United States as California, and now occur in at least 25 states, including Maryland.

In November 2008, 20 years after making its debut in North America, zebra mussels finally showed up in Maryland. A single adult mussel was found at the Conowingo Dam in the lower Susquehanna River. Less than a month later, a second adult zebra mussel (dead) was found on a boat hull at Glenn Cove Marina, upstream from Conowingo Dam in Harford County, Maryland.

Since 2008, a few more zebra mussels have been found in the lower Susquehanna River, Maryland, and in upper Chesapeake Bay. However, with less than 50 live and dead specimens reported, the zebra mussel population there, although apparently established, does not seem to expanding rapidly. “So far, there is no evidence that zebra mussels are causing any ecological or economic impacts in the areas in Maryland where it’s currently found”, says Dr. Ron Klauda, a biologist with the Maryland Department of Natural Resources (DNR).

Zebra mussels have caused serious problems in the Great Lakes and other areas where they've invaded. The have encrusted boat hulls and outboard motors, clogged power plant cooling water intake pipes, and forced expensive changes in the way municipal drinking water supply systems operate. From an ecological perspective, zebra mussels can kill native freshwater mussels, including endangered species, and clams. Zebra mussels also accumulate pollutants and toxins, and have contributed to thousands of fish-eating bird deaths.

“It’s unfortunate that zebra mussels finally made it to Maryland”, says Klauda. “Although, frankly, we feel lucky that it took so long for them to get here. What we are trying to do now is keep them from spreading from the lower Susquehanna River and upper Bay to other Maryland waters that have suitable zebra mussel habitat.”

To help stop the spread, DNR is spreading the word to boaters and anglers. “We’re asking them to Stop Aquatic Hitchhikers by following several simple guidelines listed on signs that have been posted at boat ramps and marinas in zebra mussel-infested areas”, says Klauda. “I’m also asking anyone who finds what they suspect is a zebra mussel to call me at 410-260-8615. We want to know if zebra mussels are spreading and the public can help us by being alert.”

DNR staff recently compiled water quality data collected in non-tidal areas throughout out the State. Zebra mussels are freshwater mollusks, but need
non-acidic habitats with sufficient levels of calcium to survive and thrive. “As expected, there are many rivers and reservoirs in Maryland with suitable zebra mussel habitat”, remarked Klauda. “However, we were somewhat relieved to find out that Deep Creek Lake, a popular recreational area in Garret County, is probably not good habitat for zebra mussel establishment and proliferation because the calcium levels are quite low”.

For more information about zebra mussels and other Invasive Species of Concern in Maryland, go to http://www.dnr.state.md.us/invasives/