PARENT SESSION
Oral Session #43: Fish: Ecology and Conservation.
Presiding: B. Harvey
Tuesday, August 6. 1:00 PM to 4:45 PM. Cochise Meeting Room, TCC.

Genotypic and phenotypic divergence among seasonal runs of sockeye salmon of Bear Lake, Alaska.

Ramstad, Kristina^*,1, Foote, Chris², Olsen, Jeff³, Rogers, Don⁴, ¹ University of Montana, Missoula, MT² Malaspina University-College, Nanaimo, British Columbia, CANADA³ U.S. Fish and Wildlife, Anchorage, AK⁴ University of Washington, Seattle, WA

ABSTRACT- Effective conservation of salmonids requires the preservation of populations that are diverse in life history and genetic composition. The presence of two seasonal runs of sockeye salmon (Oncorhynchus nerka) in Bear Lake, Alaska was suggested by a bimodal pattern of escapement, and management of the fishery is directed toward conserving multiple runs. However, the bimodal escapement distribution was not stable among years and there are other possible causes of such an escapement pattern. We measured variation in genetic composition and life history to investigate reproductive isolation between proposed multiple runs of sockeye salmon in Bear Lake. Significant allele frequency differentiation and unbiased estimates of FST (0.018) confirm reproductive isolation but also high gene flow between early and late run fish. Early and late fish differed significantly in egg size, ovary weight, body weight and somatic weight among females after correction to equal body size. Scale pattern analysis revealed highly significant differences in growth at age patterns between early and late run sockeye salmon. The strong evidence provided by these results supports a management strategy that will conserve the two distinct runs.

KEY WORDS: sockeye salmon, run timing, population genetics, life history