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Invasive Zebra Mussels Found In Second Maryland River

DNR Asks Citizens to Help Stop the Spread of this Harmful Species

Annapolis, Md. (October 17, 2011) - The Maryland Department of Natural Resources (DNR) recently confirmed the presence of zebra mussels in the lower Sassafras River, a tidal tributary to the Chesapeake Bay on Maryland’s Eastern Shore. A single adult zebra mussel attached to a dock in the river near Turner Creek was spotted by a concerned citizen who reported the find. This is a first-time discovery of zebra mussels in the Sassafras.

“One mussel does not necessarily constitute a population,” said DNR Biologist Dr. Ron Klauda. “But it is extremely unlikely that this is the only one out there in the Sassafras. Had the person, who discovered this single mussel not been very aware of its identity and the problems it can cause, DNR would probably not know it was there.”

DNR biologists believe that the unusually low levels of salt in upper Chesapeake Bay waters this summer may have played a role in allowing zebra mussels to expand their distribution to the Sassafras River. The Sassafras is near the Susquehanna River, which is where the invasive species was first discovered in Maryland in 2008. The Susquehanna is the likely source of the mussel and the only other place in Maryland where zebra mussels have been found.

Zebra mussels (Dreissena polymorpha) have caused over $5 billion in damages and economic losses in North America since they were introduced into the Great Lakes during the 1980s. Free-swimming zebra mussel larvae will attach to any hard surface and begin to grow. As the mussels grow, they can physically clog water systems, coat boat bottoms and any other suitable structures in the water. Zebra mussels have encrusted boats, damaged power plant intakes and changed the way municipal water systems must operate.

Ecologically, zebra mussels are killing native mussels, including endangered species, by out-competing them for food and space. Zebra mussel presence has been connected with other widespread ecological impacts, ranging from increasing toxic microorganisms to declining duck populations. The main mechanism for their transport up rivers and to inland lakes is hitchhiking with people, especially by attaching themselves to watercraft and boat trailers.

“Recreational boaters can unknowingly carry zebra mussels around in bilges, minnow buckets, coolers, or attached to aquatic vegetation clinging to their boat props and trailers,” said Klauda. “In Minnesota and a number of other states, anglers and boaters have been very effective in halting the spread of this serious pest by a little preventative maintenance.”

Boaters, anglers and other recreational water users who enjoy the lower Susquehanna River can help stop the spread of harmful zebra mussels to other Maryland waters by taking these simple precautions before launching and before leaving:

  • Remove all aquatic plants and mud from boats, motors, and trailers, and put the debris in the trash.
  • Drain river water from boat motors, bilges, live wells, bait buckets and coolers before leaving to prevent aquatic hitchhikers from riding along.
  • Dispose of unused live bait on shore, far from the water bodies or in the trash.
  • Rinse boats, motors, trailers, live wells, bait buckets, coolers and scuba gear with high pressure or hot water between trips to different water bodies.
  • Dry everything at least two days (preferably five days) between outings.
  • Limit boating from place to place, particularly from the Susquehanna and Sassafras rivers to other water bodies in the State where zebra mussels haven’t invaded.

“There may be other zebra mussels that have taken advantage of the freshwater conditions in the upper Chesapeake this year to colonize new habitat, especially in the Bohemia, Northeast, and Elk Rivers,” said Klauda.

Klauda also asks that people who live and work on the water keep an eye out for zebra mussels, and call 410-260-8615 if they find anything that looks suspicious. For more information on zebra mussels in Maryland, visit

   October 17, 2011

Contact: Josh Davidsburg
410-260-8002 office I 410-507-7526 cell

The Maryland Department of Natural Resources is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages nearly a half-million acres of public lands and 17,000 miles of waterways, along with Maryland's forests, fisheries and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic and cultural resources attract 11 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at