It is a principle in ecology that the abundance of plants and animals that produce large numbers of seeds or babies is regulated by the available habitat and not by the number of seeds or babies. Pacific salmon produce a large number of babies which means that when an adequate number of smolts or fry enter the ocean, it is the carrying capacity of the ocean that regulates the production of Pacific salmon. Recent studies confirm that growth in the early marine period is related to total production of Pacific salmon with individuals that grow faster, surviving better. We propose that the recent increasing or decreasing trends in Pacific salmon abundances are caused by increasing or decreasing abundances of preferred prey in the coastal areas within the first few months after ocean entry. Fish that survive the first ocean winter will primarily be individuals that exceeded a growth – energy threshold at a critical time in the early marine period.

The analyses revealed that the return rate of chum salmon is positively correlated with coastal sea surface temperatures (SSTs) at ocean entry timing. This suggests that the SST during the ocean entry timing of chum salmon juveniles would be a major driver in controlling the broodyear abundance, and that the decline of the stock level would be caused by the «cold-spring» phase around the Pacific coastal area in Hokkaido, but 2015 brood year was exceptional. I analyzed the relationships between age at maturity of brood years and the ratio of 4 (5)-yearold fish to 3 (4)-year-old fish abundance, i. e., sibling relationships, to identify the factors affecting precision of the forecast. The analyses revealed that the age at maturity had decreased, and it resulted in the recent decline in precision of pre-season forecast. Additionally, recent decline of the age at maturity suggests that survival rate of fish with slower growth rate might be decreasing. These results suggest that the decline of chum salmon stock levels in Hokkaido would have been mainly caused by cold ocean conditions at the Pacific coast during spring. But, the low survival rate of the 2015 brood year, which matched favorable ocean conditions in the coastal area, was not explained by the general survival mechanism above, suggesting that survival rate in the Okhotsk Sea and/or farther area might be decreasing, recently.

Based on data on climate variability, it was found that, starting in 2014, during the warming period off the Pacific coast of the United States, the emergence of both productive generations and lean generations of salmon was noted. It was found that in the main fishing areas in the period after 2014 there was a downward trend in abundance, despite the fact that in some years the commercial catches were at a high level.

The high heat content of surface waters in northern North Pacific and Far Eastern Seas in 2014– 2019 has resulted in the formation of extremely favorable environmental conditions for pink salmon spawning in the Kamchatka rivers, at all stages of marine period of their life cycle. The growth of Far East pink salmon catches in 2014–2018 was associated to a great extent with an unusual increase in the catch of even-year generations of East Kamchatka pink salmon, which were not dominant for this stock. In 2018, their share in the total catch of Russian pink salmon reached almost 22%, while in 2006–2010 it did not exceed 3–6%. The growth of catches of evenyear generations of East Kamchatka pink salmon in 2014–2018 coincided with an anomalous decrease in the ice cover in the Bering Sea and shift of its border far to the north. The return of thermal and ice conditions in the Bering Sea and the near-Aleutian region to the mean long-term level in the winter of 2019/2020 obviously contributed to the less favorable survival conditions for the 2018 East Kamchatka pink salmon generation and recovering of the «sawshaped» variations of biomass observed during the recent decades and, as a result, the similar variations of catches, with their high volumes in odd years and low volumes in even years.

The paper presents an analysis of the relationship between the variability of sea surface temperature anomalies (SSTa) in the areas of autumn-winter migrations of young Pacific salmon from Eastern and Western Kamchatka and the dynamics of the number of catches of their producers. The series of observations includes the period 1971–2020. The SSTa data collection site covers the waters of the western part of the Bering Sea, the southern part of the Sea of Okhotsk and the northwestern part of the Pacific Ocean.
The results of the studies showed that in the areas of mass feeding of juvenile pink salmon, chum salmon and sockeye salmon, the SSTa indicators have a stable relationship with the number of catches of these species. Most of the reliable relationships are indicated by moderate correlation coefficients at the level of r = 0,30–0,60. The pattern is observed for all salmon species in a significant part of the considered water area in the autumn period (September-October). In winter, the relationship is observed much less frequently. It is proposed to use the accumulated SSTa series for multidimensional modeling.
In addition, the promptly obtained SSTa data in the autumn period of the year preceding the year of fishing, will allow using this indicator as an indicator information characterizing the conditions of feeding of juvenile salmon.

This paper discussed the impact of global warming on the Pacific salmon of the Russian Far East. The probable reasons for changes in catch volumes, timing of spawning migration and biological indicators of fish are considered.

The paper presents an analysis of the dynamics of stocks of two mass long-cycle species of Pacific salmon of Kamchatka — chum salmon and sockeye salmon. It is noted that, since the mid-1990s, the number of the main units of stocks of these species has reached a historical maximum. However, by 2020, there are trends to reduce some regional groups of chum salmon and sockeye salmon stocks. In addition, in 2020 adult fish of the dominant age cohorts were characterized by very low size-mass indicators. Attention is drawn to the negative trends in changes in the average weight in the generations of sockeye salmon and chum salmon over a sufficiently long period of time. It is assumed that in the near future, the stocks of chum salmon and sockeye salmon may move to a lower level of abundance. Presents the main methods used in predicting the number of returns of Pacific salmon with a long life period and the validity of the estimates obtained. The elements of the salmon fishery management system in the Kamchatka are described.

The dynamics of the approaches of the pink salmon of the Kamchatka region has undergone significant changes in 2010 years. The increase in the number of runs (catch + escapement) approaches occurs simultaneously with an increase in the range of variability of fluctuations in the fishing stock, which requires constant improvement of the methodology for forecasting approaches. The main forecasting methods of this type used in Kamchatka are considered. Taking into account the large fluctuations in the stock, the rules for regulating the fishery are proposed, based on precautionary management guidelines.

Several significant forecast failures occurred during 2020 pink salmon (Oncorhynchus gorbuscha) fishing season in Russia. The major crush was observed for eastern Kamchatka. Precarious harvest was also observed for some Alaskan stocks. This paper represents an opposing representation of environmental and feeding condition during pink salmon offshore migration and wintering in 2019–2020 which were considered as unfavorable according to several authors. A comparison of 2019 prey composition and feeding intensity with long-term data showed that feeding conditions were sufficient. The feeding conditions in the fall of 2019 could not be the reason for the low returns of pink salmon in 2020. Analysis of environmental conditions (configuration of the western subarctic gyre, temperature distribution, position of isotherms, ecology and abundance of zooplankton species) demonstrated no significant difference with previous years. Therefore, in our opinion, the dramatic thermal regime shift during the winter 2020 in the North Pacific which caused structural changes biomass decrease in zooplankton communities and, consequentially, deterioration of the feeding conditions, seems quite doubtful.

The analysis of Pacific salmon stock dynamics in the Amur River for an almost 100-year period was conducted. Until 2017, a salmon fishery was produced without additional regulation measures that was explained by an increase in number and a stable state of reproduction conditions of these species. This fact has led to an increase in the number of fishing companies and fishing areas, and aggravated IUU fishing. At present, the abundance of the Amur summer chum salmon after the outbreak of 2008–2018 fell to the average long-term level, the stock of autumn chum salmon is also declining, but at a slower pace. The article describes fishery regulation measures and the restrictions launched in 2018–2020. A positive dynamic was revealed in the number of fishes in spawning grounds and in laying eggs in salmon hatcheries. It confirms efficiency of the restrictions introduced in recent years.

The hydrological characteristics of the coastal area are described in four areas: 1) the northern part of Aniva Bay — Lososy Bay, 2) the southeastern part of Aniva Bay, 3) stone-rocky coast of southeastern Sakhalin and 4) open sandy coast of southeastern Sakhalin on the results research in 2017–2020. The stage-by-stage (from the second decade of May to the first decade of July) variability of the structure and production parameters of zooseston was analyzed. The variability of the coastal ichthyofauna and the feeding of planktophagous fish are described. The calculation of the receiving capacity for smolts of Pacific salmon (pink salmon and chum salmon) has been made. In the northern part of Aniva Bay (section 1), the receiving capacity for smolts of chum salmon is estimated as 335 million units, for smolts of pink salmon as 426 million units. The receiving capacity of the southeastern part of Aniva Bay for smolts of chum salmon is estimated as 78.3 million units, for smoltsof pink salmon as 398,3 million units. The receiving capacity in section 3 above a depth of 0–3 m for smolts of chum salmon is about of 138,7 million units, for smolts of pink salmon about of 129., million units. The receiving capacity in section 4 above a depth of 0–3 m is about of 18,2 million smolts of chum salmon and about of 67,2 million smolts of pink salmon.

Pink and chum salmon are the most popular Pacific salmon species for hatchery propagation comprising together more than 87% of Pacific salmon juveniles released into the North Pacific Ocean. These two species heavily contribute to the total Pacific salmon harvest-85.7% in numbers and 80.0% by weight since 2001. Last years, efficiency of pink and chum salmon hatchery propagation started to decline under the recent climate changes. Ocean heat waves impact the southern part of salmon area, where 95% of hatcheries are located southward from 50°N. Hatchery juveniles mortality increases and hatchery salmon impact on wild salmon stocks looks to be overestimated. Despite the emerging crisis situation in the salmon hatchery propagation, the issues of adopting its technologies and management are almost being not investigated. The results of otolith marking are not published regularly. It is necessary to revise the efficiency of the existing hatcheries, develop an adaptive strategy for the further development of hatchery propagation, which will be based on the principles of their concentration in relatively isolated areas to allow fishing mainly for hatchery pink and chum salmon. Extensive experimental work is required on the basis of federal-owned fish hatcheries using new advances in genetics and genomics, as well as conducting biochemical and genetic monitoring of salmon run along with parasitological one.

Based on the identification of otolith tags of chum salmon of the 2009–2014 generations (a total of 1621 specimens were studied) return coefficients were calculated for salmon fish breeding plants of the Naiba River (south-eastern Sakhalin). Significant differences were found in the effectiveness of the salmon fish breeding plants of the Naiba River: the average return rates of chum salmon return of the hatchery «Zalom» was 1,59%, the hatchery «Bereznyakovsky» — 0,84%, the hatchery «Sokolovsky» — 0,48%. It is shown that the value of the return coefficient was more closely related to the release dates of the young than to the weight of its body and the reservoir of origin of the parent individuals. It is concluded that there are reserves for the growth of the catch of factory chum salmon on Sakhalin, provided that the timing of the release of artificial juveniles is optimized.