This paper considers organization of biological structure of the sockeye salmon population of Northeast Kamchatka, spawning within the Karaginskaya subzone. Characteristics of the spatial and ecologicaltemporal structure of the species are described. Biological statistics data on sockeye salmon for the period 1979–2021 are summarized

The paper presents generalized information for the ten-year period (2011–2020) on the stock abundance status of some West Kamchatka cherry salmon populations. Data on spawning stock abundance and catch statistics from scientifi c and recreational fi sheries are given. The sex and age structure is considered. Dynamics of body length and weight and absolute fecundity are analyzed. The results of the study make it possible to consider the West Kamchatka cherry salmon as a recreational fi shery object for the nearest decade.

Seasonal growth and formation of annual rings on scale of juvenile Pacifi c salmon (Chinook, sockeye, coho and cherry salmons) restart in the Bolshaya River basin from mid May to mid June. In the last half of June and until the end of July, there are actually no additional formations on the scales of both underyearlings and yearlings. In August–October false annual rings (FARs) of dense circuli can be observed on scales of underyearlings of species mentioned above. Forming the extra FARs in the yearlings of coho and cherry salmon during their second season of growth not found (few exceptions only). The underyearling’s FARs are most frequent (17.4%) in Chinook salmon, following by sockeye salmon (12.1%) and coho salmon (7.1%), and the most rare (1.0%) in cherry salmon. The frequency of the FARs in yearlings during their growth period in the fi rst summer is 28.1% in Chinook salmon, 12.6% in sockeye salmon, 11.7% in coho salmon and 4.8% in cherry salmon.

The object of the research is microalgae of HAB complex (harmful algal “bloom”). The purpose of the work is to provide monitoring data on HABs and the microalgae habitat conditions near the eastern coast of Kamchatka, which is currently the focus of attention of the Kamchatka government in terms of development of recreational and tourist activities, one of the priority economic directions. Suface water samples were collected at the coastal transect, stretching along the whole coast of the Avachinsky Gulf in the process of the work from April to October. Hydrological data were collected with Rinko- Profi lerASTD-102 and YCI CastAway probes. In June, the data were collected as part of planned ichthyoplankton survey. As a result, a real database on taxonomic composition, quantitative vales and distribution of microalgae of the HAB complex was formed. Data on water temperature and salinity, biogenic background of the Avachinsky Gulf coastal waters were obtained.

According to the results of bottom grab surveys carried out in 2013–2016, data on the biomass (g/m2) of the dominant sea urchin species Echinarachnius parma and the complex of brittle stars on a plot of the West Kamchatka shelf are given. The average biomass of Echinarachnius parma for the surveyed plot varied over the years and in 2013 was 45.298 ± 25.582 g/m2, in 2014 – 48.784 ± 26.561 g/m2, in 2015 – 19.557 ± 11.678 g/m2, in 2016 – 18.957 ± 13.192 g/m2. In terms of biomass on the surveyed plot (g/m2) the main role among the echinoderms belongs to fl at sand dollars, and in terms of population density (ind./m2) – to brittle stars. 11 species of brittle stars from 4 families were noted. In terms of population density the most common species among the brittle stars are Amphiodia craterodmeta and Ophiura quadrispina.