Gonad size and weight dynamics and gonad-somatic index in the course of maturation have been analyzed, size structure and condition of oocytes of Pacific saffron cod at different stages of ovary matura- tion has been clarified. Reproductive cycle has been demonstrated, and scale of gonad maturation stages has provided.

Data on harvesting, seasonal dynamics, structure of coastal and marine fishery, size and age composition of saffron cod catches near the Southern Kuril Islands are given. Summer–autumn distribution and size composition of saffron cod aggregations is considered based on the data of bottom trawl surveys. Distribution of saffron cod is shown almost everywhere near Kunashir Island, the Lesser Kuril Ridge and Pacific coast of Iturup Island. Harvesting is provided throughout the year, but mainly at December fishing for bottom and demersal fish species in the South Kuril Strait and May–June fishing with small fixed nets near Kunashir. Although catches of saffron cod have increased in recent years, the species is still under exploited commercially.

An improvement of the forecast of pink salmon runs is one of the most actual problems in management of salmon stocks of Kamchatka. Algorhythm of Random Forest with the use of iterative selection of most important climate-oceanological predictors seem to be promising. Three authenticly influental predictors have been found for the model of Random Forest at the error of the forecast of 28%. Verification of the obtained results used alternative methods of selection of the best predictors. Obtained results have demonstrated possibility of the use of considered climate-oceanological predictors in modeling the forecasts of stock abundance dynamics of pink salmon in Western Kamchatka.

Data on the dynamics of major biological indices (sex ratio, age composition, length and weight) for the populations of toothed smelt in the lakes Nerpichye and Kalygir (East Kamchatka) were obtained as a re- sult of winter monitoring of the stocks for 2011–2022. The data were collected in the mode of amateur (recreational) ice fishing. This approuch allowed making expert assessment of the annual catch of toothed smelt in the lakes by amature fishermen. It has been found, that the actual total catch of smelt in the lakes Nerpichye and Kalygir, believing average annual data, is about 300 t, what is looking like commercial scale. How- ever, results of the monitoring indicate, that biological structure in both popuations of toothed smelt has not demonstrated any substantial longterm changes, what indicates of a stable modern state of the stocks of the species in the lakes Nerpichye and Kalygir.

The paper shows mechanisms of influence of organic matter of marine origin entering the Bolshaya River basin with spawning escapement of Pacific salmon on the quality of freshwater macrozoobenthos. It has been found out that larvae of amphibiotic insects can receive marine nutrients through direct consumption of benthos in summer-autumn period and indirectly through trophic chains for a long time (till spring of the next year). The effect of Pacific salmon spawning escapements on such invertebrate characteristics as body weight, content of lipids and fatty acid-markers of food sources (phytoplankton, bacterioplankton or detritus) has been established. It is concluded that the trophic conditions of macrozoobenthos organisms, the food items of juvenile fish, have improved due to the intake of more marine nutrients.

The aim of this work is to assess the impact of polar bears (Ursus maritimus Phipps, 1774) on the distribution, abundance, and migration activity of Pacific walrus (Odobenus rosmarus divergens Illiger, 1815) on the coastal rookery Cape Vankarem (Chukotka Autonomous District) during the period from August to October 2017–2021.

Also, based on the analysis of data on the number of walruses and bears on the rookery and analysis of photographs, we tried to assess the physical condition of predators, the degree of their attachment to the rookery, i. e. to determine how the age and sex composition of the bear group at the rookery changes during the development of walrus migration activity on the Cape Vankarem rookery. It has been established that: along with anthropogenic influence, polar bears are one of the main factors scaring walruses on the Cape Vankarem coastal rookery; immature bears spend significantly more time at the rookery than adult females with pups or adult males; the physical condition of the majority of bears is good, but the adult males are more frequently below average in fatness; while in the rookery, no food and space competition for food resources was observed between bears.