News from the DNR Office of Communications

Zebra Mussels Now Established In Susquehanna River Below Conowingo Dam

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

Port Deposit, MD (July 15, 2010) — On July 6th, a team of biologists from the Maryland Department of Natural Resources’ (DNR) Monitoring and Non-tidal Assessment Division spotted several suspected zebra mussel adults for the first time in the lower Susquehanna River below the Conowingo Dam. These recent findings indicate that a population of this non-native, invasive mussel is established in this part of the Susquehanna. The first-ever sightings of zebra mussels in Maryland occurred in the lower Susquehanna River upstream of the Conowingo in November 2008.

“Most of the specimens were the largest I’ve ever seen, ranging up to 38 mm (almost 1-1/2 inches) in shell length, and they were probably three to four years old,” said DNR Biologist Ron Klauda.

Zebra mussels (Dreissena polymorpha) have caused over five billion dollars in damages and economic losses in North America since they were introduced into the Great Lakes during the 1980s. Based on studies conducted in the Hudson River Estuary, New York, the potential impacts of zebra mussels on the freshwater to slightly brackish portions of Maryland’s aquatic ecosystem could be substantial, with effects on all aspects of the food web from plankton to fish by outcompeting native species, filtering all available plankton and rapidly colonizing large areas.

“The good news is that, at least for now, the density of zebra mussels appears to be low,” said DNR Natural Resource Biologist Jay Kilian.

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:
(1) Remove all aquatic plants and mud from boats, motors, and trailers, and put the debris in the trash.
(2) Drain river water from boat motors, bilges, live wells, bait buckets and coolers before leaving to prevent aquatic hitchhikers from riding along.
(3) Dispose of unused live bait on shore far from the water body or in the trash.
(4) Rinse boats, motors, trailers, live wells, bait buckets, coolers and scuba gear with high pressure or hot water between trips to different water bodies.
(5) Dry everything at least two days (preferably five days) between outings.

DNR urges boaters to do their part to stop the introduction and spread of zebra mussels and other invasive species in Maryland. Citizens who find what look like zebra mussels should seal them in a zip lock bag, put the bag in the freezer, record where and when they were found and report the find to DNR at 410-260-8615. For more information about zebra mussels and other invasive species in Maryland, call 1-877-620-8DNR or visit

   July 15, 2010

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

The Maryland Department of Natural Resources (DNR) is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages more than 449,000 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 12 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