A note on domoic acid in California coastal molluscs and crabs

Between the end of October 1991 and July 1993, a total of 1182 bivalve shellfish samples were analyzed for domoic acid (787 mussel, 349 oyster and 46 clam samples). Overall, 53 (4.5%) were found to be positive, with the maximum concentrations being 47 ppm in mussels, 1.9 ppm in oysters and 29 ppm in razor clams. The highest concentratiosn were observed during November and December, 1991, in mussels from Monterey Bay and razor clams from Humboldt County, approximately 300 miles north of Monterey Bay. Low concentrations of DA have now been identified in mussels from each of California's fifteen coastal counties, and in oysters from most commercial growing areas in the state. There has been no demonstrable seasonality to these low level occurrences of DA. More pronounced seasonality has been observed in P. australis abundances in Monterey Bay. In addition to DA being found in bivalves and anchovies, it also has been found in both rock and Dungeness crabs harvested along the California coast.