There were 57 steelhead caught in a study of the winter ecology of Pacific salmon in the Gulf of Alaska from February 25 to March 25, 2022. The study used experimental gillnets and baited longlines to capture Pacific salmon with steelhead only captured in gillnets. Steelhead catches were the largest of all Pacific salmon catches with most steelhead caught in the top 4 m of the gillnet that was set at the surface and all steelhead were caught in the top 6 m. These catches and a review of published studies indicated that steelhead spend virtually all of their life in the open ocean in the surface few meters. There were 34 ocean age 1 and 21 ocean age 2 steelhead with 9 of these fish mature. DNA identification of these mature steelhead indicated they were returning to the Columbia River, Puget Sound, West Coast of Vancouver Island and the Nass River area. These fish would arrive in rivers after the calendar winter and would be expected to spawn quickly. There were 45 other fish identified to their spawning location using DNA, but the spawning location assignments of all steelhead are tentative because of the limited baseline data base. There were no ocean age 2 fish that had a second annulus and 16 of 33 ocean age 1 fish had an annulus. The circuli on the scales of ocean age 1 fish that formed after the annulus ranged from 2 to 7 indicating that annuli on the scales of all steelhead form over a protracted period. Steelhead were caught at some stations where surface temperatures exceeded the upper thermal limit published for steelhead in the winter. The inherited requirement to live at the ocean surface and the continued ocean warming that includes recent marine heat events, identify the urgent need to better understand the ocean ecology of steelhead, particularly in the winter.

   The role of scientific research surveys in the stock assessment system and justification of total allowable catches of crabs and crab-like species is analyzed. It is shown that the biological characteristics of these species – discontinuous growth through molting, impossibility of direct age determination, complex size-sex structure of the commercial stock – determine the key and irreplaceable role of trawl and trap surveys in obtaining primary data for stock assessment. The requirements for information support of TAC justification established by the current regulatory framework of the Russian Federation are examined, and the place of survey data in procedures at various levels of information support – from structured models to empirical methods – is considered. The evolution of methodological approaches in Russian practice is traced: from the area-swept method through empirical balance equations for direct forecasting to the use of survey indices for calibration of population models. Limitations of balance equation methods due to the lack of verification and validation procedures are identified. The main modeling approaches used in crab stock assessment are characterized, including CSA-family models (Collie-Sissenwine Analysis), surplus production models, and indicator methods, and the dependence of their results on the quality and regularity of survey data is demonstrated. It is shown that CSA models occupy an intermediate position between the first and second levels of information support and have a fundamental limitation – the complete exclusion of females from the model structure, which prevents the determination of spawning biomass reference points. As an example of direct use of survey data in a formalized fishery management system, the Canadian experience in managing snow crab (Chionoecetes opilio) stocks is examined, based on harvest control rules linked to trawl survey indices and validated through Management Strategy Evaluation. This approach is analyzed not as an alternative to model-based methods, but as a complementary tool whose applicability depends on survey regularity, length of historical data series, and the state of model support for a given stock. The advantages and limitations of both approaches are discussed, and the necessity of ensuring regularity and standardization of survey operations as a prerequisite for reliable crab stock assessment regardless of the chosen methodology is substantiated.

   The spiny king crab is a commercially fished species of aquatic biological resources in the Far Eastern seas of the Russian Federation. Published data on the biology of P. brevipes are available for populations in the Sea of Okhotsk and the Sea of Japan, off south-eastern Kamchatka, and in the waters around the Kuril Islands and Hokkaido. This is the first description of the life cycle, growth, and sexual and size structure of the spiny king crab inhabiting the Shelikhov Bay area of the Sea of Okhotsk. On the shelf of Western Kamchatka in August, the densest aggregations of males were recorded at depths of 31 to 43 m (34,7±1,5 m); the water temperature at these depths ranged from +8,9 to +10,6 °C (9,8 ± 0,4 °C), while females were found at depths of 31 to 43 m (35,7 ± 2,3 m), with temperatures ranging from +8,9 to +10,6 °C (9,8 ± 0,9°C). In September, dense aggregations of males were found at depths of 48 to 67 m (59,5±4,6 m), with water temperatures at these depths ranging from +10,4 to +10,7 °C (10,6±0,2°C), while females were found at depths ranging from 44 to 56 m (48,0 ± 2,8 m), with temperatures ranging from +10,4 to +10,7 °C (10,6 ± 0,2°C). The maximum group growth size (CWinf) for males and females was 180,4 and 132,5 mm respectively, which is higher than that of males off Hokkaido – CWinf 170,4 mm. Moulting of the spiny king crab in Shelikhov Bay presumably occurs in May, and larval release in October. The average estimated value for the onset of sexual maturity was CWmat 81,0 mm for males and 78,2 mm for females.

   Estimates of the total biomass of the Far Eastern capelin, calculated based on the results of bottom trawl surveys off the Okhotsk coast of Sakhalin in 2002–2024, showed that in the Aniva Bay they reached a maximum of 3986 tons (2011), in the Bay of Patience and near Southeastern Sakhalin – 5761 tons (2015), in Northeastern Sakhalin – 3602,5 tons (2002). In general, three levels of capelin biomass were identified for the East Sakhalin subzone during the specified period of years: high – within 5,0–6,0 thousand tons (occurrence – 18,8 %), medium – 1,0–3,0 thousand tons (25 %), low – less than 1.0 thousand tons (56,2 %). Based on the results of bottom trawl surveys, the total biomass of East Sakhalin capelin falls within the range of similar parameters established for the area under consideration earlier. A certain conjugacy was revealed between the estimates of the total biomass and the commercial catches of this fish for the next year.

   Based on data collected in 2019 during the expedition conducted on research vessel «Professor Levanidov» in the Laptev Sea there was analyzed size and age composition of Greenland halibut. As well as comparative analysis of age determination using two recording structures (otoliths and scales) was carried out. According to the Shapiro-Wilk test, the null hypothesis of normal distribution is rejected with high probability. Therefore, the Mann-Whitney U-test was chosen to compare the lengths by age groups. There weren’t found statistically significant differences between the groups. Greenland halibut were found in catches ranging in age from 1 to 7 years and in length from 11 to 58 cm. Greenland halibut’s male ranged in age from 2 to 7 years, while females ranged from 1 to 7 years. The size range within the same age groups showed practically no difference between males and females. The only exception was seven-year-old fish, where females were on average 2 cm larger than males. The results of this study can be used to monitor the status of Greenland halibut stocks in the Laptev Sea for subsequent analysis of possible changes dynamic.

   Data on the dynamics of atlantic salmon smolt migration in the Keret River in 2022–2025 are presented. An analysis of the relationship between water temperature and the dynamics of downstream migration of juveniles was carried out. The greatest number of smolts migrate at a water temperature of 14,5–16,5°C. The Pearson correlation coefficient shows a very weak relationship between the variables (r = 0,19). The Spearman correlation coefficient showed a strong direct correlation (ρ = 0,81). Average size and weight characteristics of juveniles: weight 23,8 g, length 12,9 cm. Sex ratio (♂:♀) 1:1,9. The Smolt age classes are represented by two, three, and four-year-olds. The predominant age group in each year of the study is three-year-olds. The average age of salmon tarts is 2,0 years. The results of the research can be used to monitor the state of the atlantic salmon population, develop measures to conserve salmon stocks, and also to generate materials for forecasting salmon production in the Republic of Karelia.

   Peled (Coregonus peled) are a key aquaculture and commercial fishery species in Siberia. Introduced to the Krasnoyarsk Reservoir in 1968, they are currently the only whitefish species targeted for commercial fishing. This paper presents an analysis of changes in main biological parameters of the Krasnoyarsk Reservoir peled spawning stock (age and size composition, length, and body weight) from 2010 to 2024, based on our own data and a comparison of these data with data from previous years (1980–2009). Since the 2010s, a consistent decline in the linear and weight growth rates of peled in the reservoir has been observed.Compared to data from 1980–1989, the standard length of fish aged 2+ and 3+ has currently decreased by more than 10 cm, and body weight by 400 and 900 g, respectively. Low growth rates of this aquatic biological resource in recent years may be due to a combination of factors, both natural (food supply, availability of spawning sites) and anthropogenic (high level of reservoir depletion, intensification of fishing, low stocking volumes).

   This paper presents new data on size–weight characteristics and growth parameters for 12 common fish species inhabiting the transboundary section of the Upper Dnieper River (within the Russian Federation and the Republic of Belarus), including representatives of the families Leuciscidae, Percidae, and Esocidae. The material was collected during joint Russian–Belarusian expeditions in 2018–2024. It is shown that the majority of the studied species (8 out of 12) exhibit isometric growth, in which relative body proportions do not change with increasing size. Negative allometry, indicating a relative decrease in body depth in larger individuals, was found in bream Abramis brama, white bream Ballerus ballerus, and black bream Ballerus sapa. For the first time in the region, the parameters of the von Bertalanffy growth equation were calculated for seven species. The highest growth rates (coefficient K > 0,4 year^-1) were established for silver bream Blicca bjoerkna, roach Rutilus rutilus, and pikeperch Sander lucioperca, which corresponds to their life strategy of early maturation and high reproductive capacity. Slow growth, typical of riverine populations with long life cycles, was observed for bream (K = 0,199 year^-1) and chub Squalius cephalus (K = 0,254 year^-1). The obtained length–weight relationships and growth parameters can serve as regional reference values for monitoring population status, stock assessment, and improving fisheries management measures in the Upper Dnieper River basin.

   Comparative studies of the areas of the Babinskaya Imandra bay of the lake Imandra (Murmansk region) with different levels of heat exposure has shown that, despite the preservation of the general oligotrophic status of waters, bottom communities and fish act as sensitive indicators of warming. In the zones of thermal influence, a multiple increase in the quantitative indicators of benthos was recorded, which led to a change in the trophic status of benthic communities to eutrophic and provided the European perch with an excessive food supply. Against the background of restructuring the ichthyocenosis towards the status of the whitefish-perch, the perch has an increased life expectancy up to 10+ years and a significant acceleration of linear growth. It has been established that in modern conditions, the transition to ichthyophagy occurs earlier, at the age of 3+ years, when the length reaches 190 mm, which provides a second surge in growth rate. Technogenic heating acts as a catalyst for the species’ life cycle, reducing the age of mass maturation to 6+ years, after that, there is a natural slowdown in growth due to the redistribution of energy to generative processes. The high ecological plasticity of the perch allows it to effectively use the resources of all zones of the Arctic reservoir, responding to increased environmental productivity by accelerating ontogenesis. Methodologically, it has been confirmed that the most accurate recording structure for verifying the age and correctness of reverse calculations in Arctic perch populations is the articular foramina of the cranial vertebrae.

   The paper presents the main fishery characteristics of the pike-perch population in the Vazuza Reservoir, obtained during the 2025 research within the state assignment of the Russian Federal Research Institute of Fisheries and Oceanography (VNIRO). The age structure of the commercial part of the population, as well as the dynamics of linear and weight growth of fish, were evaluated. Differences in the growth rates of males and females, determined by the biological characteristics of the species and energy expenditures for primary oogenesis, were noted. It was established that the basis of the catches consists of individuals aged 2+ to 8+ years, with the dominance of two modal groups aged 4+ and 5+. The volume of possible removal was calculated taking into account a comprehensive approach to stock exploitation and amounted to 27,68 tons.

   The results of studies of two-and three-year-old stellate sturgeon obtained using cryopreserved and native sperm are considered.

   The purpose of the work is to develop recommendations for the formation of a repair-mother herd of stellate sturgeon (Acipenser stellatus) during the period of somatic growth.

   Fishery-biological and physiological studies of groups of fish were conducted. The results of the growth of two- and three-year-old sturgeon groups (2022, 2023) when kept in ponds and basins, as well as the size and weight characteristics of different-aged sturgeon individuals and their physiological indicators, were obtained, which allowed for the assessment of the fish’s condition. A breeding program was conducted to select sturgeon individuals based on their phenotype, resulting in the selection of promising individuals that meet the fish farming criteria for further cultivation and herd formation. A comparative assessment of the fishery and biological indicators of two-and three-year-old stellate sturgeon obtained using cryopreserved and native sperm is given.