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Freshwater Mussel Surveys


Although freshwater mussels are most diverse in North America, where there are 281 species and 16 subspecies, they are among the most rapidly declining animal groups on the continent. The Nature Conservancy recognizes 55% of North America's mussel species as extinct or imperiled compared to only 7% of the continent's mammal and bird species. In North America above Mexico, there are 19 taxa presumed extinct, 44 species listed or proposed as federally endangered, and 60 species that may be endangered. In addition, a number of the endangered species are functionally extinct, with individuals of a species surviving but not reproducing. Freshwater mussel extinctions and declines can be attributed to several factors, including habitat degradation, construction of dams and subsequent loss of host fishes, and expansion of exotic mollusks such as the zebra mussel and Asian clam.

Freshwater mussels, or pearly mussels as they are sometimes called, are among the oldest living organisms on Earth. Individuals are thought to reach ages in excess of a century. As vital ecosystem components, they are food sources for wildlife such as raccoons and muskrats. Young mussels are eaten by ducks, herons and fishes. Often referred to as nature's vacuum cleaners, they improve water quality by straining particles and pollutants from rivers. In addition, since mussels have a low tolerance for water-borne pollutants, they are excellent indicators of water quality.

New Jersey is home to twelve native species of freshwater mussels, including the federally endangered dwarf wedgemussel (Alasmidonta heterodon) and three federal species of special concern - the brook floater (Alasmidonta varicosa), green floater (Lasmigona subviridis) and yellow lampmussel (Lampsilis cariosa). Although the dwarf wedgemussel was thought to be extirpated in the state, a recent finding of live individuals in the Paulins Kill River, Sussex County has prompted intensive surveys of the waterway. The brook floater is only known from small, most likely non-breeding occurrences in three areas of the state, whereas the yellow lampmussel is restricted to the Delaware River. The green floater is by far the most endangered mussel in the state, represented only by a single individual in the Stony Brook, Mercer County. Other species that are under consideration for state endangered or threatened status are the eastern lampmussel (Lampsilis radiata), eastern pondmussel (Ligumia nasuta), tidewater mucket (Leptodea ochracea), and triangle floater (Alasmidonta undulata).

Recognizing national and regional declines, as well as impending threats such as zebra mussel infestation, Endangered and Nongame Species Program biologists have been searching the state's waterways for freshwater mussels. Since 1993, Program biologists have been conducting freshwater mussel surveys for rare species by targeting historic locations, suitable habitats and areas with host fishes present. Viewing scopes and sometimes snorkeling gear are used by staff and volunteers to search for mussels in our state's streams, rivers and ponds. In addition to wading in water, we inspect shorelines for shells and relicts (very old shells) at all survey sites. Locating populations, however, is only the first step to protecting these inconspicuous, yet vitally important mollusks.

As part of the Landscape Project, critical areas for freshwater mussels are now being mapped using criteria designed specifically for aquatic species. We will develop protection strategies for endangered and threatened species by working with local municipalities, landowners, other state and federal agencies, planners, and organizations such as water watch and conservation groups. In addition, plans are underway to produce an atlas of New Jersey's freshwater mussels which will include life history narratives, color plates of shells, location maps, and information on national and state range, status, shell description and host fishes for each of the state's twelve species.


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