Homing, Straying, and Gene Flow among Seasonally Separated Populations of Chum Salmon (Oncorhynchus keta)

摘要: To test the hypothesis that salmonids that stray into established populations can successfully reproduce, we compared the spatial and temporal pattern of return of marked individuals with the pattern of gene flow suggested by electrophoretic analysis in three populations of chum salmon (Oncorhynchus keta) on Vancouver Island. Substantial straying occurred between populations that spawned during the same season. Populations where there was both spatial and temporal isolation in spawning had little straying. Electrophoretic analysis suggested that gene flow was substantially lower than the rate of straying and that it was highest among populations in close geographic proximity. The results of analysis using a log-linear model showed that the probability of discovering an individual stray was dependent on the population sampled and whether one sampled by mark–recapture or using biochemical genetic analysis. We propose that the difference between the rate of straying as measured by mark–recapture and by the analysis of polymorphic enzymes could be accounted for if salmonids straying onto the spawning grounds of established populations of conspecifics had lower reproductive success than fish that return to their natal streams.