The study deals with the up-to-date status of snow crab stock in the Kara Sea and the prospects of the related fishery in the region. Currently, snow crab is distributed on an area of about 270000 km² (app. 30% of the Kara Sea). The potential of further expansion is not quite fulfilled though. Comparative analysis of the distribution density of the stocks in the Barents Sea and the Kara Sea revealed a chance to initiate the fishery in the new region in the upcoming years. The current stock of snow crab in the Kara Sea is estimated as high as 11 000 tones with potential 1,100-2,500 tones as annual yield. Further increase in the stock is possible, provided both increase in abundance within the existing area and extension of the latter.

Comparison of the spatial distribution of spawning walleye pollock, eggs and larvae distribution showed that they are largely spatially close, although there was a slight drift associated with currents. The reason for the «collapse» of stocks is related to walleye pollock reproduction conditions in the open part of the Bering Sea. This is supported by the fact that, despite the insignificant commercial exploitation of walleye pollock in the Commander basin, stocks began to decline sharply after reaching the maximum. In the Bogosloff Island region of the Bering Sea, a sharp decline in stocks and catch was due to weak recruitment of the fishing stock, that is, due to natural causes. At the maximum initial number of walleye pollock spawning fish in 1984, there was a record number of swept eggs, but this did not lead to the appearance of high abundance generations, while at the initial biomass of spawning individuals in 1978, which was 1,5 times less than the average level, extremely generation is appeared. Taking into account the reduced area of the research, the research carried out by American scientists is not complete enough, so there is a need to conduct a large-scale trawl-acoustic survey. Based on the analysis of the variability of the Pacific Decadal Oscillation, it is assumed that there is a high probability of a new outbreak of walleye pollock biomass in the Bogosloff Island region.

Azov-Black Sea branch of Fisheries and Oceanography, Rostov-on-Don, 344002 Stock assessment of the European sprat Sprattus sprattus phalericus, localized in the waters off the shores of the Crimean Peninsula and Caucasus, has been performed for 1994-2019, using XSA cohort model in FLR package in R. The current state of the system «stockexploitation» for the sprat in Russian waters of the Black Sea is characterized by slight overfishing according to the reference points accepted in fisheries management: F₂₀₁₇-₂₀₁₉/F₀₁ = 1,08 and E₂₀₁₇-₂₀₁₉ = 0,45. Comparison of the obtained results against the background of the previous published assessments involving XSA and ICA models allowed us to establish continuous annual time series for Crimean and Caucasian sprat stocks in 1951-2019 and to judge them into three stock states: «good» (1951, 1973-1981, 1985-1989, 1999-2004), «bad» (1953-1958, 1963-1971, 1990-1997, 2006-2019), and moderate (all other years). It is possible that current «bad» state of the sprat stock is due to bonito predation one the part, which mass invasions from the Marmara Sea have become more frequent over the last 15 years, and is also related to reduction of the average weight in 1-3-year individuals. Ongoing climate change gives no reason to expect improvement of the state of Crimean and Caucasian sprat stocks, which leads us to the conclusion that there is no room for increasing Russian exploitation of the sprat stocks in the Black Sea in the medium term.

The results of a comparative analysis of catches size composition of the Norwegian-Barents Sea beaked redfish by fishing and research vessels in 1960-2019, as well as a model evaluation of its stock dynamics under different scenarios of fishing selectivity are presented. It is shown that the intensive and unregulated fishing of the beaked redfish in the 60-70-s of the last century led to a sharp increase of relative portion of young individuals in the stock. The management measures that were taken later on limitation of bycatch of small fish, along with decrease of fishing, facilitated to the recovery of both stock biomass and its size structure. In the model, a change of fishery selectivity by increasing removal of large individuals lead to a growth of stock size, but a decrease of the catches. According to the model estimates, a resistance of the Norwegian-Barents Sea beaked redfish to a fishery pressure should increase with a shift in the fishery selectivity towards the older individuals.

Dynamics of the blue king crab commercial stocks from different Russian seas is given for the period 2013-2018. Each stock assessment is based on the data of research surveys which corrected by the data of fisheries statistics (corrected stock assessment). Generally the difference between the data of representative research surveys and corrected stock assessments are not significant. Comparison of (corrected) stocks dynamics with reference points allowed clarifying the status of each stock unit. By 2020 the largest stocks remained in good condition despite the trend to decline.

The Gobies scales and urostyle were previously used as the gobies (family Gobiidae) registration (recording) structures. The unevenness of the scaly coating of the gobies body is illustrated with the simultaneous presence of different types of scales in different body localities: cycloid and ctenoid. The x-ray of skeleton with fused urostyle is given in two projection. The difficulties of using scales and urostyle for the age determining are small fish with incomplete loss of body is substantiated. Otoliths morphology of two species of the Caspian goby fish: the Sand-goby Neoobius fluviatilis and Khvalynsky goby Neogobius caspius is described for the first time. The size and weight of the fish, as well as morphometric otoliths indicators are given. Photographs of otoliths are given according to which the age of the studied species was first determined. Gobies otoliths are recommended for their age determining.

Dynamics of stocks is considered for three common species of flounders on the shelf of West Kamchatka: yellowfin sole (Limanda aspera), flathead sole (Hippoglossoides elassodon), and brown sole (Limanda sakhalinensis) on the data of bottom surveys conducted in 2007- 2017. All three populations have similar changes: the stocks increased, the portions of juveniles increased, the main aggregations shifted to the northern part of the shelf. Yellowfin and brown sole redistributed to shallow depths, as well, where their juveniles dwelled usually.

In flatfish (order Pleuronectiformes) the initial development is provided by relatively low concentrations of thyroid hormones in the body compared to the period of metamorphosis, at the level of their amount in the embryonic period. At the same time, the stimulating effect of these hormones on the differentiation of the intestinal epithelium and the activity of digestive enzymes, as well as key parameters of the development of fish larvae, including survival, has been shown. The significance and methods of exposure to thyroid hormones contained in flatfish food objects - microalgae and zooplankton with a high content of organic iodine, presumably in the form of iodotyrosines - are discussed.

The influence of various factors on demersal fish biomass fluctuations and the change of dominant species in three climatic zones is considered from an ecosystem point of view. On the shelf in each of them the density of the bottom fish assemblage increased over 40 years (the Anadyr-navarin region - from 13,7 to 35,5, the western Kamchatka region - from 45,2 to 79,0, Peter the Great Bay - from 12,1 to 13,4 ton/km²). Outdated, but still prevailing simplified ideas about the causes and scenarios of biocenotic rearrangements occurring there are criticized. In particular, this is about the presence of severe food competition between the abundant bottom inhabitants, and about another myth that, after overfishing of commercially valuable fishes, their ecological niches occupies previously not numerous species of by-catch, and this irreversibly reduces the useful fish productivity of marine areas.