Year: 2018, Number: 4, Pages: 92-108
Since 1972, collectors were exposed in the water column of Minonosok Bay for collection of a spat of the Yesso scallop Mizuhopecten (=Patinopecten) yessoensis (Jay). Also the scallops were reared in suspended cages and on the bottom up to their trade size. Previously, the mariculture influence on the dynamic and composition of macro- and meiobenthos was studied, but the changes in the bottom scallop settlement were practically not studied for the period of mariculture in the Bay. The work was made to meet this lack. It was found, that there were significant changes in the structure and abundance of the scallop population all time. The density of the local scallop settlements varied from 50 ind./m2 (just after transfer of juveniles to the bottom) to about of zero density (after taking commercial scallops away) at the same places; and only 1–2 scallop generations were periodically determined at the age structures of these settlements. Usually, the absolute majority in the local scallop settlements were the cultured individuals transferred to the bottom. The growth rate was low for the species. All parameters of native scallops (settled to the bottom in a natural way) were significantly higher than that of cultivated specimens. According to the results of the microsculpture study of the upper scallop valves in was revealed that individuals, transferred to the bottom in the autumn (0.5-year-olds) grew slightly slower than native scallops, but were significantly larger than the scallops transferred in the spring at 1-year-old age. Scallops from muddy sand had significantly larger parameters than individuals from mud. Increasing of a concentration of suspended particles and reducing of an oxygen concentration in the water are more frequent events over mud, than over sand, worsen the environmental conditions for the scallop, which is sensitive to these factors. Besides, it was found that the upper valves of the scallops from the mud were more bioeroded than valves of the individuals of the same age from muddy sand. Bioerosion of the shell also reduces the scallop growth rate. With a decrease of anthropogenic pressure of this kind on the Bay, the growth rates of the bottom scallops changed little, except the innermost area of the Bay, where the scallops became larger in 2004 than in 1990.