Zebra mussels spotted in upper bay

Zebra mussels have finally made their way down the Susquehanna River to the Chesapeake Bay, though it's unclear what if any harm the invasive aquatic species might do there.

This month, state biologists found 20 of the non-native shellfish attached to three channel marker buoys off Havre de Grace as they were removing the buoys from the water for the winter, the Department of Natural Resources reported.

Native to the Caspian and other seas in eastern Europe, zebra mussels were first discovered in the United States in the Great Lakes region in the 1980s, likely transported there in the ballast water of ships. Since then, they've spread rapidly throughout the rivers and lakes in the central and eastern portions of the country.

Because they breed prolifically and attach themselves in great numbers to hard surfaces, the mussels have clogged water intakes for power plants and other facilities, causing billions of dollars in damage. They also wreak ecological havoc by crowding out native mussels and other shellfish.

Zebra mussels were first spotted in Maryland in 2008, at two locations on the lower Susquehanna River — Conowingo Dam and Glen Cove Marina in Harford County. There have been occasional sightings of them since then, including last year in the lower Sassafras River, but no indication yet that they're proliferating.

The Havre de Grace discovery is the first confirmation of their presence in the upper bay.

"We know that these mussels are from this year's spawn since these buoys and anchors were deployed this spring," Matt Ashton, a DNR biologist said in an announcement released by the department.

Biologists have said they doubt the mussels can thrive in the brackish bay because they're a freshwater species. But experts are concerned that they or their eggs could be carried by currents to other rivers, where they could spread into fresher water and thrive.

Meanwhile, DNR officials are warning boaters to beware of unwittingly aiding the mussels' spread, since they could attach hitch a ride on boats, trailers and other recreational gear. Boaters are urged to drain all river water from their boats and equipment whenever pulling out, and to rinse everything with high-pressure or hot water between trips to different water bodies, then let it dry for two to five days before putting back in the water.

tim.wheeler@baltsun.com

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