A shell of their former selves.

• Author: Frasca, Salvatore, Jr.
• Position: EYE ON ECOLOGY - American lobster

THE AMERICAN LOBSTER long has been a vital commodity for the coastal communities of New England and the provinces of Canada. Valued at hundreds of millions of dollars, the lobster fishery is one of the few remaining viable, traditional, natural fisheries in eastern North America. There is growing concern that this natural resource may be in peril in the face of emerging diseases and climatic and environmental changes.

During the past six years, normally robust lobster populations, particularly in the southernmost extent of their natural range (New York's Long Island Sound), have suffered from a number of ailments that significantly have reduced the volume and worth of catches. Diseases are not new, but increased incidences and spread are raising new questions, especially since oysters, clams, and other mollusks also are affected.

Diseases that harm harvest and post-harvest lobsters are well known and some are the cause of systemic infections that already have induced economic losses to the industry. We have spent years studying the impact of the two newest diseases--epizootic shell disease and paramoebiasis--on lobster populations.

Epizootic induces deterioration of the lobster's normally hard shell while leaving behind unsightly lesions. This renders affected lobsters unappetizing, thus reducing their marketability and commercial value. This disease has spread from its original locale (Buzzard's Bay, Mass.) to the eastern Long--Island Sound; Cape Cod Bay, Mass.: Kittery, Maine; and the offshore waters of New England. Paramoebiasis, meanwhile, is an infection of the internal tissues, particularly those of the nervous system. It is caused by the single-celled amoeba. Because of the deterioration, the shells are so unsightly that the infected lobsters cannot be marketed as live.

During the autumn of 1999, there was a large-scale die-off of lobsters in Long Island Sound. There also were reports of increased numbers of dead or dying crabs and sea urchins. Many theories about the cause have been put forth, including pesticide applications, effluents from sewage treatment plants, dredging sediment, ecological and climatic factors, and infection by a parasitic paramoeba species. At present, little can be done to stop it.

Although not as well known as the lobster trade, the aquaculture production of bivalves is an industry valued at approximately $26,000,000. The eastern oyster and hard clam are the most common types of bivalves, and both have...