Thermal Conditions in Marine Coastal Waters as a Favorable Factor for Formation of Extremely Strong Year Classes of Karaginsky Bay Pink Salmon

The variability of the timing of downstream migration of juvenile pink salmon from the Hailulya River to the adjacent coastal waters of the Karaginsky Bay is considered. The influence of the coastal water temperature on variations in the strength of year classes for two lines of pink salmon spawning in the Karaginsky Bay is analyzed for 1978–2020. The conditions for the downstream migration after 2002 are considered optimal because the mean water temperature weighted by the migration intensity for 10-day periods in those years exceeded 5.6°C and reached 9.9°C in some years (with an average of 7.8°C) and showed a tendency to steadily increase. It is proposed that the factor of food availability for juveniles in marine coastal waters ceased to be limiting for the formation of year-class strength in Karaginsky Bay pink salmon by the end of the first decade of the 2000s. An original model of variations in year-class strength with an acceptable quality is proposed, which takes the temperature of coastal waters in late June into account, and the number of parents (R² = 0.791). The attempt to simulate forecasts of the pink salmon that returned in 2021–2023 yielded satisfactory results. It has been found that it is necessary to revise the level of the return reference point and the fishing management models for obtaining and managing extremely strong year classes.