Spatial Distribution, Size and Age Composition of Population of Mya japonica Jay, 1857 (Bivalvia: Myidae) in Peter the Great Bay, Sea of Japan

Abstract

In July–August 2022, the spatial distribution and the composition of local settlements of the bivalve mollusc Mya japonica Jay, 1857 in the Vostok Bay (Peter the Great Bay of the Sea of Japan) were studied. M. japonica occurred almost throughout the entire bay in a wide range of depths from 0 to 22 m at water temperatures from –1.9 to 25°С and salinity from 0 to 34‰. M. japonica was the most abundant in the shallow areas of the bays, closed from the direct wave impact, where, at a depth of up to 4–5 m, the density of the mollusc reached 27 ind./m², and the biomass was almost 4 kg/m², which averaged 56% of the total macrozoobenthos biomass. With increasing depth and moving from the dead-end of the bay to the open sea, the abundance of M. japonica decreased by one or two orders of magnitude. Local settlements differed significantly in size and age composition, size-frequency distribution of molluscs, indicating the nature of the replenishment of the benthic population with juveniles, as well as the proportion of commercial size individuals, which ranged from 37 to 98%. The reasons for the revealed features of the distribution and structure of the population of M. japonica are discussed.