An extended model for the formation of the number of generations for the Amur River summer chum salmon (Oncorhynchus keta)

We analyzed the reasons for deviations in the number of summer Amur chum salmon offspring from the theoretical «parent-offspring» relationship described by the Ricker equation. It is shown that the strongest deviations are caused by precipitation in the year of spawning and in the year of downstream migration of juvenile fish. The second most influential factor is the pre-winter air temperature in the year of spawning. These both factors are positively correlated with the magnitude of deviations. It is proposed an equation describing the relationship between the number of offspring and the number of parents, precipitation and air temperature, which satisfactorily simulates the dynamics of the number of offspring. The results are discussed in connection with similar results from studies of other salmon populations and species.