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A quasi-cyclicity associated with variability of environmental conditions is detected for the regression residuals of the stock-recruitment model for chum salmon Oncorhynchus keta in the Okhotsk district, described by Ricker’s equation. The main factors influenced on the chum progeny abundance were the number of spawners and the amount of precipitation in the spawning grounds area in certain months. A mathematical model has been developed that simulates satisfactorily the dynamics of progeny, which can be used for forecasting. Role of the freshwater and marine periods of chum salmon life in formation of the year-classes strength is discussed.