[Caitlin]

Now for the bad news:

POTENTIAL EXOTIC FRESHWATER BIVALVE INVADERS
The native freshwater bivalves are found in the sediments of streams or lakes. Their shells can be partially exposed, as in the case of Elliptio or other freshwater mussels, or completely buried - allowing breathing through tiny siphons that extend to the sediment surface - as in the case of the fingernail clams.
One potential invader to Rhode Island's freshwaters that also inhabits sediments is Corbicula fluminea, that is native to the Far East. As of 1991, this Asian clam had established itself in the lower Connecticut River, causing concern to Connecticut's state conservation agency. The Asian clam has a heavier shell than most native bivalves, grows to about an inch in length, and has a black exterior coat (periostracum) on the shell.

Zebra mussels, Dreissena polymorpha, are different from the native bivalves and the Asian clam in that they tend to settle on and encrust hard surfaces, such as rocks or man-made structures, by adhesive threads called byssal fibers. Zebra mussels can colonize sediment surfaces by initially attaching to a hard surface, such as an exposed rock, with subsequent generations attaching themselves to the shells of the older mussels. Zebra mussels rarely exceed one inch in length, and often have banded markings on their shells.



Further Information About Native Freshwater Bivalves
Baker, F.C. (1928). The fresh water mollusca of Wisconsin. Part II. Pelecypoda. Bulletin of the Wisconsin Geological and Natural History Survey 70:1-482.
Johnson, R.I. (1980). Zoogeography of North American Unionacea (Mollusca: Bivalvia) north of the maximum Pleistocene glaciation. Bulletin of the Museum of Comparative Zoology (Harvard University) 149:77-189.
Lefevre, G. and W.C. Curtis. (1910). Studies on the reproduction and artificial propagation of freshwater mussels. Bulletin of the United States Bureau of Commercial Fisheries 30:105-201.
Smith, D.G. (1991). Keys to the Freshwater Macroinvertebrates of Massachusetts. Department of Zoology, University of Massachusetts, Amherst. 236pp.
R.I. Department of Environmental Management Fish & Wildlife staff: http://www.dem.ri.gov/programs/bnatres/fishwild/staff.htm

Return to Rhode Island Sea Grant Fact Sheets