Period of occurrence, density and distribution of larvae of three commercial crab species in Peter the Great Bay, Sea of Japan

The period of occurrence, density, and distribution of larvae of three commercial crab species in Peter the Great Bay and adjacent waters of the Sea of Japan were studied on the basis of data from plankton surveys carried out in 2004-2009. The larvae of the hair crab Erimacrus isenbeckii (Brandt, 1848) were found in the plankton from mid-March and to early June at a water temperature from -1 to 10.8 degrees C. The larvae of the helmet crab Telmessus cheiragonus (Tilesius, 1812) were encountered from mid-April to late June at a water temperature from 2.8 to 13.0 degrees C. The larvae of the snow crab Chionoecetes opilio (O. Fabricius, 1788) also appeared in mid-April but could be found in very low numbers until early August. All species of crabs produced one larval generation during the breeding season. The timing of occurrence of the crab larvae in the plankton was related to water temperature; the length of the pelagic period increased in colder years. Larval density was the highest in C. opilio (up to 41 indiv./m(3)), zoeae of E. isenbeckii and T cheiragonus were not numerous (density not exceeding 2 indiv./m(3)). C. opilio larvae were generally distributed throughout Peter the Great Bay, maximum concentrations of early stages were observed in its open southwestern part. Maximum densities of E. isenbeckii zoeae were found in the southern part of Amursky Bay and in Possjet Bay. T cheiragonus larvae occurred in very low numbers in Possjet Bay, southern Amursky Bay, and Ussuriisky Bay. Late larval stages of all species concentrated in areas of coastal eddies.