Objectives

1. Characterize the population structure and genetic diversity of Lake Clark sockeye salmon.

This will aid managers in defining and prioritizing conservation units of sockeye salmon within Lake Clark National Park and Preserve.

2. Provide genetic samples and data to the Alaska Department of Fish and Game (ADFG) for use in mixed stock fishery analyses.

This will provide the first estimates of commercial fishery impacts on Lake Clark sockeye salmon.

3. Assess the relative importance of geologic history (colonization and subsequent gene flow) and local adaptation (selection) in shaping spawning populations of Lake Clark sockeye salmon.

This analysis will identify factors that are key in maintaining the diversity of sockeye salmon present in Lake Clark.

Methods

Populations were located using radio telemetry and spawning was confirmed by ground surveys (see Radio Telemetry page).  Since 1999 we’ve collected fin tissue from over 3600 fish representing 22 spawning populations throughout Lake Clark.  Our genetic analysis includes 13 of these populations (Figure 1) that spawn in habitats representing a wide range of ages (100 to 8,000 years old) and habitat types (glacially influenced, spring-fed, beach and stream).  We are currently genotyping 100 fish per population at 11 microsatellite loci and characterizing mitochondrial DNA variation through restriction fragment length polymorphism analysis.

Patterns of genetic diversity within and divergence among populations will be tested for correlation with the geologic history (currently being reconstructed by Dr. Patricia Heiser),  and current geography of Lake Clark.  In addition, we’ve measured phenotypic traits of spawners (egg size, body size, age at maturity, and secondary sexual morphology) and habitat characteristics (depth, substrate size, temperature, and turbidity).  We’ll assess evidence of local adaptation by comparing fish spawning in different habitat types (beach, stream, glacial and non-glacial) to evaluate patterns of phenotypic variation against the backdrop of selectively neutral genetic variation.

Preliminary Results

Preliminary microsatellite analysis (10 populations) suggests significant genetic variation within Lake Clark.  Pairwise estimates of F_ST (a statistic that describes the degree of reproductive isolation between spawning populations) range from zero to 0.08 and suggest: 1) divergence between populations of lower and upper Lake Clark, 2) strong differentiation of Sucker Bay Lake fish from all other populations, and 3) weaker but still significant divergence of Kijik system fish from other populations of upper Lake Clark.  Principal component analysis supports this pattern of genetic differentiation.  In Figure 2, the proximity of population points reflects how genetically similar they are and the numbers in parentheses indicate how much of the total genetic variation is explained by each axis (component).  Fish spawning in younger habitats do not have reduced genetic variation (allelic diversity or heterozygosity) relative to fish spawning in older habitats.  Genotyping and mtDNA analysis of fish collected in 2001 and outgroups are ongoing, a final report will be completed in December 2002.

Results

Founding events influence genetic population structure of sockeye salmon (pdf 320k) - poster given at the American Fisheries Society Annual Meeting in Anchorage, Alaska on September 12-15, 2005.

Acknowledgements

This research is funded by the Federal Office of Subsistence and the National Park Service - Natural Resources Parks and Preservation Program.  Many thanks to the personnel of Lake Clark National Park and Preserve, the people of Nondalton, and all those who assist in the field and lab.