Mortality of late juvenile and adult stages of the scallop Mizuhopecten yessoensis (Jay)

Abstract

Age and size distributions of living populations of the Japanese scallop Mizuhopecten yessoensis (Jay) and accumulations of dead scallop shells were compared in two areas of Peter the Great Bay (northwestern Sea of Japan) to determine the life stages at which higher mortality occurs. The highest mortality was recorded in the juvenile and pre-mature stages, when scallops were less than 2 years of age, and for individuals 6–7 years of age (probably the beginning of the senile period of scallop development) and 9–10 years of age (transition to the old-aged stage). The possible seasons of death were determined by examining the microsculpture of the external shell surface. The seasons at which the highest mortality occurred differed in various localities and was dependent on the extent of deviation of environmental characteristics from the optimal values for the scallop.