Genetic contribution of three introduced life history forms of sockeye salmon to colonization of Frazer Lake, Alaska

Colonization of Frazer Lake (Kodiak Island, Alaska) by sockeye salmon (Oncorhynchus nerka) represents a rare, successful introduction of this species into a new environment. Eggs, fry, and adults were introduced repeatedly into Frazer Lake from 1951 to 1971. Donors originated from three source populations, each with different life histories: late-run lake shoreline spawners (Karluk Lake), early-run inlet tributary spawners (Red Lake), and late-run lake outlet spawners (Ruth Lake). We used six nuclear DNA (nDNA) microsatellite loci and mitochondrial DNA (mtDNA) to determine which donor population(s) had colonized the principal spawning habitats of Frazer Lake: three shoreline areas and four inlet tributaries. Based on nDNA comparisons, two shoreline-spawning populations were most similar to the shoreline donor, and the four tributary-spawning populations were most similar to the tributary donor. However, five of the seven Frazer Lake populations appeared to be influenced genetically by more than one donor. Genetic distances based on mtDNA were independent of life histories with high (relative to nDNA) interpopulation variation, suggesting significant female founder effects and poststocking drift. Our data suggest that life history adaptations of donor populations were critically important for successful colonization of Frazer Lake, thus underscoring the need to consider life history traits in other introduction and recovery programs.