Somatic and Reproductive Growth of the Yesso Scallop in Polluted Amur Bay

Abstract

To elucidate the reproductive activity of the Yesso scallop Mizuhopecten yessoensis (Jay, 1857) in polluted Amur Bay (Peter the Great Bay, Sea of Japan), the seasonal patterns of growth of its gonad, adductor muscle, and digestive gland were studied. As the results of this study have shown, spawning in this polluted bay leads to a decrease in the weight of not only the gonads, but also the adductor muscle, and the digestive gland of scallops, which suggests that the energy spent for gametogenesis is provided, in particular, by the energy reserves of these somatic tissues. It has been found that in the years of heavy pollution of these waters, the decrease in the weight of the organs of the scallop for first gametogenesis was insignificant during the spawning period, which indicates the incomplete contribution of first-time spawning two-year-old individuals to reproduction of the population. With a decrease in the level of environmental pollution, two-year-old scallops show a significant loss in the weight of their gonad and somatic tissue during spawning; i.e., they undergo successful spawning. In the period of sexual maturity, the annual increment of somatic tissues decreases with age, but the reproductive activity increases, subsequently decreasing in the senile stage of the life history of the scallop.