Biological studies in the Russian Far Eastern and Arctic seas in the VNIRO Transarctic expedition

The results of biological research on the RV “Professor Levanidov” in the Bering, Chukchi, East Siberian, Laptev and Kara seas, July 6 — October 2, 2019 are presented. Expatriates from the Pacific and Atlantic oceans made a significant contribution to the biomass of plankton communities in the Arctic seas. Plankton biomass was depended on the distance from the Bering Strait in the east, the Fram Strait and the Barents Sea in the west. A noticeable level of biomass was maintained by local Arctic plankton species. In megabenthos, crustaceans dominated in the Kara and Chukchi seas, and echinoderms in the Laptev and East Siberian seas. The biomass of demersal fishes (mostly Pacific cod, Saffron cod, yellowfin flounder, great sculpin and starry flounder) in the Karaginskaya subzone was 318 thousand tons, pollock biomass was 539–1349 thousand tons. The biomass of demersal fishes (mostly cod, great sculpin, and arrowtooth flounder) in the Olyutorsko-Navarinsky area was 768 thousand tons, pollock biomass 359–897 thousand tons. Representatives of Cottidae, Zoarcidae, Liparidae, Gadidae, Pleuronectidae, and Agonidae families comprised the bulk of catches in Arctic seas. Polar cod dominated in all seas, with exception of the Chukchi Sea, where pollock biomass increased many times compared to previous years. In the Laptev Sea, the abundance of Greenland halibut increased significantly. In the Chukchi Sea, Polar cod biomass was 117 thousand tons, flathead sole 43 thousand tons, pollock 897 thousand tons, snow crab 51 thousand tons. In the Kara Sea, Polar cod biomass was 171 thousand tons, snow crab 67 thousand tons. Significant differences in food composition and feeding intensity of pollock, Polar cod, capelin and Greenland halibut of different sizes revealed the existence of a complex trophic system. Anthropogenic pollution was assessed, the distribution of species- indicators of vulnerable marine ecosystems was studied, and materials for genetic research were collected