Genetic variation of steelhead trout (Salmo gairdneri Richardson) populations in the South Fork Trinity River, California

Thesis (M.S.)--Humboldt State University, 1988Electrophoretic methods were used to study the genetic characteristics of steelhead (Salmo gairdneri) from the South Fork Trinity River, California. Genetic variation, partitioned into within and between geographic river sections, was analyzed using hierarchical log likelihood statistics and gene diversity analysis. South Fork steelhead populations were also compared to the Trinity River Hatchery population. Significant allele frequency differences occurred between the hatchery and South Fork Trinity River populations. Significant allele frequency differences also occurred between both the geographic sections and between tributaries within sections. Genetic diversity analysis revealed that 95.5% of the genetic variation was due to differences within populations, 3.3% of the variation was due to differences among populations within geographic sections, and 1.2% of the variation was due to differences among geographic sections. Nei's index of similarity was high (I>0.995) in all pairwise comparisons. UPGMA clustering of genetic identity values did not reveal any pattern of geographic association. The South Fork Trinity River is a single stock genetically structured at the tributary level of subdivision. An allele, previously undescribed, was detected at the LDH-4 locus with a relative mobility of 44