Are there zebra mussels in the Chesapeake Bay Watershed?

Bay watershed map with Potomac drainage basin highlighted

The water in the Chesapeake Bay comes from many states. The shaded area shows the extent of the lands that send water to the Bay. The darker orange shaded area is the portion of the Bay watershed that drains to the Potomac River. Dots are known reproducing populations of zebra mussels in the Bay watershed as of June 2004.

Yes, zebra mussels occur in the Chesapeake Bay watershed. But, fortunately, they currently have colonized only a few water bodies and are not yet widespread.

In the summer of 2002, thriving zebra mussel populations were discovered in Eaton Brook Reservoir and Canadarago Lake, upper Susquehanna River watershed, New York State. In June 2004, adults and larval zebra mussels were collected in Goodyear Lake, the first major impoundment on the Susquehanna River, near Cooperstown, New York, about 25-30 miles downstream of the river's headwaters. Scientists from the State University of New York at Oneonta confirmed that the downstream movement of larval zebra mussels from Canadarago led to successful colonization of the Upper Susquehanna River.

In 2002, and even closer to Maryland, a population of zebra mussels was discovered in Millbrook Quarry, a 12-acre, popular recreational diving spot in Prince William County near Haymarket, Virginia. Although hydrologically isolated, the quarry is adjacent to Broad Run, a tributary to Lake Manassas, and upstream from Occoquan Reservoir and the Potomac River. Virginia Department of Game and Inland Fisheries developed a plan that successfully eradicated this population in early 2006. For more details, see their website:

Zebra mussels have apparently not become established in the Pennsylvania, Maryland, West Virginia and Delaware portions of the Chesapeake Bay watershed. Nevertheless, they pose a serious threat and the current risk of dispersal is high. The following material relates the possible dangers and what people can do to avoid spreading this non-native, invasive species to uninfected areas.

Two page fact sheet explaining why boaters should be concerned about zebra mussels, and how they can help.

The following documents are available in the DNR Carter Library and Information Resource Center (IRC ):

(1995) Introduction of non-indigenous species to the Chesapeake Bay via ballast water: strategies to decrease risk of future introductions through ballast water management. This Chesapeake Bay Commission report discusses ways of avoiding the spread of invasive species through ballast water management. The report includes a clear picture of the negative aspects of ballast water dumping, a list of recent Bay invaders, and the current proposals on how to alleviate the problem.

(1993) Chesapeake Bay policy for the introduction of non-indigenous aquatic species. This report, produced by the Chesapeake Bay Program, provides the guidelines for dealing with non-native species that enter the Bay and sets up governmental regulations against introducing any new non-indigenous species into the watershed.

(1993) Zebra mussels and the Mid-Atlantic: reports from the Sea Grant programs of New Jersey, Delaware, Maryland, Virginia and North Carolina. The regional summaries in this report result from the conference: “Zebra mussels: a threat to the Mid-Atlantic, a conference for educators, technical experts and resource managers”, held in Baltimore on March 10-12, 1993. The regions covered are: Virginia, North Carolina, Maryland, New Jersey, Delaware, and New York.

Date page was last updated: 4/22/2009

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