Accumulation of paralytic shellfish toxins in the scallop Patinopecten yessoensis caused by the dinoflagellate Alexandrium catenella in Otsuchi Bay, Iwate Prefecture, northern Pacific coast of Japan

: The survey on scallop toxicity in association with causative dinoflagellates was conducted when the cultured scallops Patinopecten yessoensis were found to accumulate paralytic shellfish toxins in late November of 1997 at Otsuchi Bay, Iwate Prefecture, Japan. Alexandrium catenella was observed in high density at the beginning of the survey. The cell density of A. catenella decreased and completely disappeared in early December. The scallop toxicity also decreased with decrease of the cell density of A. catenella. The toxin profile of the scallop was similar to that of natural and cultured cells of A. catenella isolated from the Bay, showing that scallop toxicity is due to A. catenella. This is the first case in which paralytic shellfish toxins were confirmed in scallops during a bloom of A. catenella in Sanriku coast of Iwate Prefecture.