Tuesday, September 4, 2012

Freshwater Mussels in New Jersey

Eastern lampmussel     Lampsilis radiata

In North America, there are 281 species and 16 subspecies of freshwater mussels. And yet, they are among the most rapidly declining animal groups on the continent.

North America's freshwater mussels (AKA pearly mussels) are listed by The Nature Conservancy as 55% extinct or imperiled compared to only 7% of the continent's mammal and bird species.

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.

These mussels are sometimes referred to as nature's vacuum cleaners. They actually 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.

Freshwater mussels are among the oldest living organisms on Earth. Individuals are thought to reach ages in excess of a century.

They are food sources for wildlife such as raccoons and muskrats and young mussels are eaten by ducks, herons and fishes.

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).

We believed that the dwarf wedgemussel was extirpated in the state, but 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).

Searching for freshwater mussels using a viewing scope.
© Mike Davenport via conservewildlifenj.org
Since 1993, Endangered and Nongame Species Program biologists have been conducting freshwater mussel surveys for rare species and shorelines for shells and relicts (very old shells) at all survey sites. As part of the Landscape Project, critical areas for freshwater mussels are now being mapped using criteria designed specifically for aquatic species.

SOURCES:
  • Freshwater Mussel Surveys http://www.state.nj.us/dep/fgw/mussels.htm
  • For more detailed information, search "mussel" on Conserve Wildlife Foundation NJ's excellent New Jersey Endangered and Threatened Species Field Guide conservewildlifenj.org/species/fieldguide/

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