Hydrological regime and morphodynamics of the outlet part of the Kamchatka River, dynamics of mixing zone, patterns of juvenile Pacific salmon distribution and migration in the coastal waters of Kamchatsky Gulf in the zone of operating trap nets were analyzed on the results of complex field works prowided in summer period in 2018–2019; fishing and specifics of sockeye salmon spawning run in the river was described. In the course of analyzing the entire complex of available long-term data, an assessment of the likely impact of some key factors on the dynamics of anadromous migration of sockeye salmon in the Kamchatka River was made; biological statistics of spawners and current state of reproduction of this stock was demonstrated. It is found, that natural environmental factors, neither abiotic nor biotic (including fish health as population internal factor), could not cause disturbance of sockeye salmon spawning run dynamics in the Kamchatka River in recent years. Smoller body size and physiological imperfection of the spawners before the anadromous migration due to effects of high number of pink salmon in recent years are suggested to be the most likely cause of spawning run delay in late sockeye salmon morph. Regime of commercial use of the stock and general increasing pressure on the spawning stock by coastal fisheries are demonstrated to be the strongest outer factors to affect modern state of the resources and sockeye salmon population structure in the Kamchatka River, causing permanent escapement deficiency on spawning grounds in the river basin (first of all in the late morph), and also infact lead to disballance between different subpopulation groups in the composition of the stock. Recommendations in order to provide recovery and sustainable level of the Kamchatka River sockeye salmon stock are given in the perspective of more efficient commercial use of the stock next several years; highlights for further researches are outlined.

Long-term trends in distribution and regional composition of the catches of hatchery pink and chum salmon during autumn post-catadromous migrations in the basin of the Sea of Okhotsk in 2011–2017 were evaluated based on the otolith marking data. Qualitative and intraspecific structure of the hatchery fish aggregations was analyzed in connection to the interannual variety in forming abundant and not abundant generations of pink salmon. The analyze is carried out allowed to find out that the aggregation density of Russian and Japan hatchery juvenile chum salmon in the eastern part of the Sea of Okhotsk is higher in the even years of observation. Along that the distribution of the active migrants of the Sakhalin-Kurile and Hokkaido stock complexes in the north-east direction withing the Okhotsk Sea basin is better expressed. We think, that the main reason is low abundance of pink salmon generations (odd years of spawning) on West Kamchatka during autumn migration in the even years.

In general the results obtained indicate that the cyclic migration of juvenile pink and chum salmon in the basin of the Sea of Okhotsk during post-catadromous migrations is of a systemic and mass character. Hatchery and wild fish have been engaged. The scheme of the juvenile distribution is similar in even and odd years.

Analysis of Danish seine catches from the coastal waters of South-East Kamchatka has revealed all seasonal distribution of saffron cod connected to the sites of the continental sandbanks influenced by aquatic vortexes with increased benthic biomass, where the catches could reach 2.5 t/fishing operation. Based on the data of the trawl and Danish seine surveying, the stock abundance, the occurence frequency, the catches of saffron cod and the contribution into the total catch in the area mentioned increased in the fall-winter period, but could not be characterized as significant. In the period of the research (2003–2018) the Danish seine catches of saffron cod varied as 1–189 t, averaged 31.8 t. The fish in the Danish seine catches had the body length from 11 to 56 cm and the body weight from 20 to 750 г. The mean length and weight of saffron cod in summer was 30.8 cm and 241.7 g and in winter – 31.2 cm and 301.6 g respectively. Occurrence of independent reproductive groups of saffron cod in the coastal bays and on the shelf of South-East Kamchatka can be suggested based on the data of stock abundance distribution, differences in the size composition and the time of maturity.

First data about biological structure of Sakhalin sole Limanda sakhalinensis on the northern shelf of the Sea of Okhotsk were obtained as results of researches provided in 2013 and 2019. It is found that the upper part of the shelf to the depth of 80 m is used by Sakhalin sole individuals with the average body length 16.1 cm, and the horizons of 171–200 m – by the 22.1 cm long individuals. The largest individuals with the length 30.5–35.0 cm were observed in catches from the lowest boundary of the area of the research. It was found that in terms of the northern part of the Sea of Okhotsk, males reach 28 cm and 206 g at the age of 18 years, and females – 35 cm and 408 g at the age of 21 years. With a general numerical predominance of males, they often (73.4%) were in catches among individuals with the body length <21 cm and younger than 8 years. The older the males, the lower their relative number (to 42.1%), and 3 last size-age groups consisted of females only. Compared to other locations occupied by Sakhalin sole, the the north-western shelf is one of the most wide; the body length and the age structure demonstrated there has maximum similarity to Sakhalin sole in the eastern part of the Sea of Okhotsk.

An example of red-billed pacu Piaractus brachypomus with standard length 271.8 mm and weight 691 g was captured in the Lake Chervyachnoye (Sakhalin island) in May of 2010. This fish was without parasites, what indicates spending a short period in the Lake. Plenty fat in the abdominal cavity says in favour of good physical condition. Stomach content included typical Sakhalin freshwater invertebrates. The species does not threat local ecosystem, because minimum temperatures in the rivers and lakes of Sakhalin during cold period of the year are lower than red-billed pacu survival temperature limit. Most likely the fish was released into the lake by an amateur aquariumist.