Trace metal concentrations in two shellfish species of commercial importance.

Abstract

The Public Health Service (Shellfish Sanitation Branch) continually collects and maintains data on metal levels in shellfish from approved shellfish areas. On the East Coast, three species are surveyed: the quahaug, Mercenaria mercenaria; the surf clam, Spisula solidisma; and the eastern oyster, Ostrea virginica. While a standard for cadmium in shellfish does not exist, the highest value for this metal in any of these shellfish from approved areas is 1.9 ppM (wet wt.) (PHS data, April 1976). In the present Public Health Program, neither the sea scallop Placopecten magellanicus nor ocean quahaug Arctica islandica are regularly surveyed (LAMB, 1976). Both species are found in deeper continental shelf areas and hence presumably farther removed from coastal sources of contamination. In recent years in the mid-Atlantic, the marketing of the sea scallop has become increasingly inportant with landings between 1974 and 1975 increasing by 81 percent (PILEGGI and THOMPSON, 1976). Furthermore, more than 80 percent of these commercial landings were caught between 12 and 200 miles offshore (a total of 3557 kg, wet weight with shell). There is at present much more limited fishing for the ocean quahaug; however, the potential for commercial exploitation is great (SAILA and PRATT, 1973). In viewmore » of the present importance of the sea scallop and the potential of the quahaug in the shellfish industry, in addition to the lack of published information on cadmium levels in these species, we present here some data on cadmium (and other trace metals) in these organisms. Samples are from a region of the continental shelf (Figure 1) which at present is reportedly fished for scallops (SAILA and PRATT, 1973). This area is removed from any large-scale inputs of trace metals from human activity (e.g., dredge spoils, industrial or municipal sewage sludge disposal).« less