The Origin of the Snow Crab Chionoecetes opilio in the Kara Sea

Most likely, the alien snow crab Chionoecetes opilio entered the Kara Sea from the Barents Sea, both due to the migration of adults and with currents at the larval stage. Currently, all bottom stages, including mature individuals and a large number of pelagic larvae, are present in the Kara Sea. However, the origin of larvae has not yet been clarified. The larvae hatched in the Kara Sea should be at an earlier stage of development compared with the larvae arrived here from the Barents Sea due to later development of phytoplankton and, accordingly, later hatching. The larvae of the snow crab Chionoecetes opilio and the spider crab Hyas araneus were collected in the central and southwestern Kara Sea in July–early August 2019 by a Bongo zooplankton net with a diameter of 60 cm. It was established that the larvae were unevenly distributed across the Kara Sea. The most populus region was the border with the Barents Sea in the St. Anna Trough (up to 860 ind./m 2 ), and relatively high concentrations of larvae were recorded in the southwestern part, where their abundance at stations varied from 18 to 302 ind./m 2 . In the zone of the Ob–Yenisei plume, crab larvae were absent or their abundance was minimal. Using molecular genetic methods, the species identity of 361 larvae (344 C. opilio and 17 H. araneus ) was reliably determined, and measurements of a number of morphological structures were made for 401 larvae. Significant differences in size were found at the zoea II stage between C. opilio and H. araneus . In July 2019, in most of the Kara Sea, in zooplankton samples, crab larvae were represented by zoea I of C. opilio with rare specimens of zoea I of H. araneus of the Kara Sea origin. Only in the southwestern part, at the boundary with the Barents Sea, was the presence of zoea II of C. opilio and H. araneus observed in samples with an increased share of the latter species in catches, which probably originated from the Barents Sea.