Although differences between selective pressures in hatcheries and streams have been theorized to cause genetic divergence between hatchery and wild salmonids, evidence of this is lacking. This study was initiated to document the presence or absence of genetic change in hatchery and wild stocks by characterizing genetic traits in fish of various life history stages within a single generation. Nine biochemical traits (enzyme loci) and 12 meristic traits were characterized for adult fall chinook and one or more juvenile stages of their progeny of the 1984 brood year. Study groups consisted of hatchery-reared and naturally-reared subunits of populations in two tributaries of the lower Columbia River: Abernathy Creek and the Lewis River. Parents of both groups from Abernathy Creek were primarily of hatchery origin, whereas parents of both groups from the Lewis River were primarily of wild origin. The experimental design thus included reciprocal comparisons of hatchery and wild-reared groups from each of two stocks: one that has been propagated under hatchery conditions for at least five generations and one that has evolved in a stream environment. Both biochemical and meristic traits varied among adult and juvenile stages within hatchery and wild groups. Changes in some of these traits appear to have been caused by natural selection. This was true even for Abernathy hatchery and Lewis wild groups, which have been in the same environment for many generations. The direction and/or degree of change in some biochemical and meristic traits differed between hatchery and wild groups from a given stream, suggesting that selective pressures of the hatchery and wild environments differed in those cases. However, it could not be determined from these data whether the observed divergence of traits reflects general differences in hatchery and stream environments, or if it reflects population-specific responses to site-specific environmental conditions. The extent to which patterns of genetic change within a single generation might vary among year classes or generations is likewise unknown. Evidence of temporal changes in biochemical and meristic traits of hatchery and wild fish within a single generation has important implications regarding the use of those traits to characterize stocks. Assumptions of temporal stability of biochemical or meristic traits within or between year classes should be applied with caution. Sampling strategies of studies involving these characters should account for the possibility of temporal heterogeneity. Finally, these results suggest that workers using allozymes as genetic tags should test the assumption of selective neutrality of the particular allozyme markers being used. / Graduation date: 1991

Genetic differences between early and late forms of Alaskan chinook salmon (Oncorhynchus tshawytscha) were identified using two genetic approaches: mitochondrial DNA (mtDNA) analysis and protein electrophoresis. The study populations consisted of early- and late-run chinook salmon in each of the Kenai and Kasilof rivers in Alaska, and a single population from the Minam River, Oregon, that provided a relative scale for the differences among the Alaskan populations. Two segments of mtDNA were amplified separately using the polymerase chain reaction (PCR) and then digested with 14 to 16 restriction enzymes. Results showed that the two early runs were genetically similar to each other but different from either of the late runs. The late runs were different from each other based on the frequency of the common haplotypes. The Minam River stock shared two haplotypes with the Alaskan stocks and displayed one unique haplotype. The frequency difference in the shared haplotypes together with the presence of a unique haplotype allowed us to separate the Oregon population from those in Alaska. In the protein analysis, each of the five populations was examined at 30 allozyme loci to determine variation within and between the runs. Based on 14 polymorphic loci, Minam River chinook salmon were genetically distinct from the Alaskan populations. Within the Alaskan populations, the two early runs were most similar to each other but different from the two late runs; the two late runs were also genetically most similar to each other. Based on all loci, protein electrophoresis proved to be a useful technique to separate stocks of chinook salmon. On a locus by locus basis, however, mtDNA was more powerful. Both mtDNA and allozyme analysis suggest that chinook salmon may segregate into genetically different early and late forms within a drainage. / Graduation date: 1995