Zebra mussels have been discovered at the Conowingo Hydroelectric Dam in Maryland; the first time it has been found in the lower Susquehanna River.
The mussel, about a half-inch in size, was found inside a water intake at the hydroelectric plant while monitoring juvenile shad migration on the river. It had not yet attached itself to the intake structure.
The nine-mile lake behind the Conowingo Dam stretches into Pennsylvania for five miles. No other zebra mussels have been found in the lake at this time.
"Controlling zebra mussels has cost more than $1 billion since they were first discovered in the Great Lakes in 1988," DEP acting secretary John Hanger said in a statement. "It will require constant vigilance by fishermen, boaters and others who use our waterways to keep these invasive creatures out of the Susquehanna River and its tributaries."
Zebra mussels pose serious threats because of their potential to plug industrial and public water supply intakes that draw from infested waters. Zebra mussels also disrupt aquatic food chains by filtering out the microscopic plankton upon which fish and other aquatic organisms rely.
The zebra mussel is native to the Black and Caspian seas region of Eastern Europe. They were introduced to North American waters when oceangoing ships released infested ballast water into the Great Lakes.