Settling of mollusks and sedimentation on artificial substrata in the Sukhodol Bay (​​Japan Sea)

Abstract

Density of bivalve spat settled on collectors determines the yield of aquaculture plantation. It varies considerably in different water areas at Primorye coast and has year-to-year variability. The spat settling intensity in the last decade is considered for a marine farm in the Sukhodol Bay (Ussuri Bay) and sedimentation of suspended matter on collectors is estimated for the same plantation in the summer of 2012. Period of the scallop spat settling is rather long and continues until late June. Mean spat size is 9.2 ± 2.2 mm (modal group 8-10 mm), mean weight is 0.08 g. The average density of juvenile scallops Mizuhopecten yessoensis changes year-to-year from 77 to 200 ind./collector, and the density of juvenile mussels Mytilus trossulus - from 500 to 2,330 ind. per meter of the collectors set. These values provide the annual harvesting of > 2 million ind. of the scallop spat and 10-30 ton of commercial-size mussels from 1 hectare of plantation. Juveniles of sea cucumber Apostichopus japonicus settle on collectors as well, in less number, but sufficient for their growing on bottom plantations in some years. Suspended matter sedimentation on collectors, including agrestal marine organisms, is rather high in the first months after the collectors installation - up to 0.31 ton/month per 1 hectare of standard plantation. Reclamation measures are recommended in the cases of high sedimentation, possibly installation of bicultural plantations in the water column.