BIOLOGIYA MORYA, 2015, Vol. 41, No. 1, pp. 28-35

Species composition, season of occurrence and distribution of crab larvae (Decapoda: Brachyura) in the Vostok Bay, Sea of Japan

© 2015 O. M. Korn, E. S. Kornienko

A.V. Zhirmunsky Institute of Marine Biology, Far East Branch, Russian Academy of Sciences, Vladivostok 690041

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Based on the data of plankton surveys carried out in May-November, 2002, the species composition, season of occurrence, density and spatial distribution of brachyuran larvae (Decapoda: Brachyura) in Vostok Bay (Sea of Japan) were studied. The average monthly density of zoeae of this decapod group was not high and did not exceed 25 ind./m³. Larvae of 11 brachyuran species were found. The zoeae of the crab Pinnixa rathbuni occurring from May to November absolutely dominated among brachyuran larvae. Several peaks of density of the early zoeal stages of this species were recorded, implying its multiple reproduction. In summer, the ratio of P. rathbuni zoeae varied from 71 to 96% of the total brachyuran larvae, in May and November they were the only species of this group. Larvae of the rest of 10 species were few and occurred from June to October, with their highest density in August under the highest temperatures. Zoeae of shore crabs of the Hemigrapsus genus were referred to subdominant group. Brachyuran larvae were generally concentrated along the western coast of the Vostok Bay. The highest density of larvae (150-160 ind./m³) occurred in the innermost part of the bay entailed by cyclonic gyration under the south wind. The surface current along the western coast prevailing under the east and southeast winds probably carried out the larvae further south up to Srednyaya Bay, where their significant density was also recorded.

Key words: zoea, Brachyura, plankton, season of occurrence, Vostok Bay, Sea of Japan.