Interannual variability of hydrometeorological conditions in Avacha Bay was analyzed on the basis of data obtained in the course of complex standard surveys in the period from 2013 to 2022. Steady excess of climatic norm for air temperature and precipitation is shown in the area mentioned throughout the entire period of the hydrological studies. The air temperature, however, experienced significant interannual fluctuations in the considered range of years, while precipitation levels increased noticeably only in the period from 2013 to 2015, and then there was a tendency to a slow decline with a minimum in 2022. The surface atmospheric pressure exceeded the multiyear average in summer and autumn, but was below it in winter. Ten-year averages of temperature, salinity, chlorophyll-α concentration, and oxygen saturation for April through October at 10 stations on standard horizons were calculated. Analysis of interannual variability of the temperature and salinity integral indices for the entire studied water column of Avacha Bay has demonstrated a gradual increase of heat content and a slight decrease of salinity. 

Systematized information on the species composition of parasites of S. malma complex in the water bodies of Kamchatka based on own and literature data is provided. Presented taxonomic list of parasites gives information about localization, distribution, host range, findings with indication of water body, malmoid form, infestation indices and authors of findings for each species. The parasitofauna of Dolly Varden in Kamchatka includes 65 species from 3 kingdoms, 10 types, 15 classes, 25 orders and 42 families. The most diverse taxa are trematodes (16 species), nematodes (10), myxosporidia (10), cestodes (8) and acanthocephalans (7). The basis of the parasitofauna of Dolly Varden in Kamchatka is formed by freshwater species (47), species with a complex life cycle (50), using fish as definitive hosts (38), having Holarctic and circumpolar distribution (29), being a part of the Arctic freshwater and Pacific piedmont faunal complexes (33), specific to fish of the genus Salvelinus, family Salmonidae and the order Salmoniformes (39). The high species and ecological diversity of Dolly Varden parasites is due to its ubiquitous distribution in the region and its complex population structure, including several ecotypes and forms that differ in life strategy, diet, and habitats.

Results of using a state-space cohort model with smoothing unscented Kalman filter for assessment of Pacific cod stock abundance and the other population parameters in the Petropavlovsk-Komandorskaya Subzone are presented. Series of numerical experiments were carried out with various variants of the recruitment model. The results of the work performed can be used in preparing forecasts of the TAC of marine commercial fish in terms that the observational data allow the use of age-structured models in the state space.

Analysis of short-term threats to the welfare of a group of Pacific walruses (Odobenus rosmarus divergens Illiger, 1815) at the Cape Vankarem haulout showed significant changes in the structure and strength of sources of disturbance to the animals appeared over the 10 years since the last survey. Anthropogenic disturbance from passenger helicopters and traditional hunting (by spear slaughter) has decreased. The main sources of disturbance have been utilities and “northern importation”, which has increased mortality, especially of young animals. It is significantly higher than in haulouts remote from populated areas. Polar bears and local dogs are the next sources of concern.

New findings of Pacific lamprey in the Northwestern Pacific Ocean are described. New information on the morphology and biology of the species during the oceanic feeding period is provided.