Purpose: Determine the likely causes of deviations in the abundance and seasonal dynamics of pink salmon (Oncorhynchus gorbuscha) catches on Sakhalin Island (east coast) and Iturup Island from those expected in 2024. Research Material: Catch statistics (Rosrybolovstvo), biological analyses (materials of VNIRO and Glavrybvod Sakhalin branches), pink salmon numbers on spawning grounds (Glavrybvod). Methods used: Comparative analysis of data on catch and its seasonal dynamics, on fish length (FL), female fecundity and the ratio of fish of different sexes, as well as on the dynamics of downstream migration of juveniles. Results: The dynamics of pink salmon catch is determined by the ratio of its two temporal forms – early and latein approaches to the coast. Catches of pink salmon during the approach of its early form exceeded the forecast. However, with the completion of the migration of these fish, further pink salmon approaches declined sharply, resulting in an almost complete cessation of catches. Earlier estimates of juvenile fish abundance in rivers and the dynamics of their downstream migration, based on the conditions of fry habitat in coastal marine waters do not provide a basis for explaining the occurrence of this phenomenon. When different stocks of pink salmon co-occur in open marine waters, high selective mortality of fish of one of the temporal forms is unlikely. It is not excluded that this phenomenon was a consequence of “failure” of the migration mechanism in accordance with the well-known hypothesis of “fluctuating stock of pink salmon”, according to which large- scale redistribution of spawning flows of fish of this species between the areas of reproduction of different stocks is possible. Practical Significance: The results indicate additional nuances that may be useful for use in the fisheries science management process.
Каев et al. (Sun,) studied this question.