The Current Status of Demersal and Pelagic Fish Stocks in the Olyutorsky-Navarin Shelf Area

AbstractStocks of demersal and pelagic fish species in the near-bottom layer over the outer shelf and upper part of the continental slope between Cape Olyutorsky and Cape Navarin (Olyutorsky–Navarin Area), northwestern Bering Sea, were assessed using data of a bottom trawl survey over depths 20–400 m conducted aboard the R/V Professor Levanidov in the summer of 2019. The total biomass of demersal fish in the surveyed area was estimated at 682 262 t. In this biomass, Pacific cod accounted for 51.50%; arrowtooth founder, 9.80%; great sculpin, 9.64%; northern rock sole, 4.60%; Alaska skate, 4.57%; fathead soles, 2.56%; and yellow Irish lord, 2.30%. The biomass of each of the other species was less than 2%. The total biomass of pelagic fish species in the near-bottom layer, estimated with the use of catchability coefficients differentiated for species, was 759 639 t. In this value, adult walleye pollock accounted for 85.12%; juvenile walleye pollock, 9.94%; and Pacific herring, 4.67%. The rest of the pelagic species together constituted only 0.27%. The proportions of the biomasses of the major commercial species that inhabiti waters beyond the area surveyed in 2019, that is, the Gulf of Anadyr and at depths greater than 400 m in the Olyutorsky-Navarin Area,were calculated using average long-term data of bottom trawl surveys conducted in 2005–2017. There such species as the yellow Irish lord, saffron cod, Pacific halibut, arrowtooth founder, great sculpin, Kamchatka founder, northern rock sole, and Aleutian skate had proportions from 0.5 to 69.2% of the biomass in the area surveyed in 2019. The proportions of Pacific cod, Pacific black halibut, Alaska skate, and walleye pollock were from 102.9 to 190.4%; the proportions of Alaska plaice, fishes of the genus Hippoglossoides, and Pacific herring, were from 533.4 to 1380.5%. The biomass values of the commercial stocks in the study area were determined both by the status of the stocks within their ranges and by their spatial and bathymetric redistribution due to the shrinkage of the St. Lawrence Cold Water Pool that forms in winter. The conclusion was made that fluctuations in the stocks of the commercial species under study are mainly caused by natural factors and are not associated with commercial fishery.