Bimodal return distribution in a northern population of salmon: Genetic, life history, and habitat analysis of adult and juvenile sockeye salmon (Oncorhynchus nerka)

Bimodal return migration patterns are evident in many populations of North American salmonids. This thesis analyzes how bimodal return distribution affects genetic structure, life history, and habitat partitioning in a Northern population of sockeye salmon (Oncorhynchus nerka). This thesis is divided into two sections; (1) adult population genetics and (2) juvenile habitat distribution. Genetic analysis of adult spawners using eight microsatellite loci indicates that the early and late runs are genetically divergent in all seven years analyzed (1994–2000), and that differentiation is greater between the runs than among the seven years analyzed. Life history analysis (age at maturation, sex ratio, fork length) of the early and late run fish, showed contradictory results; while fork length, sex ratio, and age at maturation did differ significantly between early and late runs in some years, no consistent pattern emerged. Using the same genetic markers as for the adult analysis, habitat ecology was addressed in early and late run juvenile Klukshu sockeye salmon. (Abstract shortened by UMI.)...