Models for operational forecasting of pink salmon return abundance (runs) have been worked out based on the data about pink salmon stock abundance in Western Kamchatka in 2001–2025 and climate and ocean indices, characterizing conditions of pink salmon winter-spring feeding in the North Pacific basin. Potential climate and oceanic predictors selected included values of the sea surface water temperature anomalies (SSTa) and some of climate indices (West Pacific Pattern (WP), Pacific Decadal Oscillation (PDO), Arctic Oscillation (AO), North Pacific Gyre Oscillation (NPGO)). Two variants of predictive model for short-term forecasting of pink salmon runs in Western Kamchatka have been proposed.

This paper presents mathematical models used to forecast the abundance of chum salmon runs in Kamchatka Territory. The models are classified into two groups, each characterized by specific approaches to data analysis: time-series extrapolation and regression-based models. The first group includes two models: an exponential smoothing model (ETS) and an autoregressive moving average (ARIMA) model. The second group includes models based on an analysis of the relationship between chum salmon recruitment and the abundance of juvenile escapement and feeding underyearlings, pink salmon year-classes, and climate indices during the juvenile downstream migration from spawning rivers to the coastal part of the sea and the autumn migration to open sea waters, as well as the abundance of older age cohorts versus younger cohorts. The implementation algorithm for the applied models is presented as R scripts.

The article examined a variability of temperature and sea ice concentration in the Bering Sea in winter (November–March) for the period from 1949 to 2024. Analysis of linear trends and anomalies of sea surface temperature, surface air temperature and sea ice concentration and relationship of the parameters with climatic indices ismade. The results obtained demonstrate a long-term trend to temperature increase and a gradual reduction of ice cover, accompanied by significant inter-annual variability. The study showsan importance to continue monitoring and analysis in mentioned region forassessment of potential effects from climate changes in future.

Based on data collected during longline fishing in the guyots of the central and southern parts of the Emperor Seamounts, new information is presented on the frequency of occurrence, distribution, and some biological characteristics of the poorly studied highfin dogfish Centroscyllium excelsum. This species has been shown to be a permanent resident of cartilaginous fishes in the thalassobathial zone within the research area. Individuals of C. excelsum were found on the summits and slopes of Mounts Jingu, Ojin, Lira, and Koko at depths of 451–1068 m, with the largest catches recorded in the 801–1000 m range. Their body length in the catches ranged from 40–68 cm, and their body weight from 260–1960 g. Within the Emperor Seamounts, this species presumably exhibits spatial differentiation between juveniles and adults.

Ichthyopathological studies of juvenile chum salmon at a salmon hatchery in the Sakhalin Region, conducted in May–June 2023, revealed two interrelated problems: a chronic mixed bacterial and saprolegniosis infection causing continuous low-level mortality, and seasonal acute hypoxic events leading to mass fish kills. Characteristic histopathological changes were identified, and the antibiotic susceptibility of the isolated microorganisms was assessed.