Population genetic structure of coho salmon (Oncorhynchus kisutch ) in California

We used allozymes to examine the genetic structure of 27 populations of coho salmon from northern and central California. Genetic variability was low throughout the study area. Although 23 of 45 loci were variable, much of the observed variation was due to rare and uncommon alleles (frequency < 10%). Average heterozygosity estimates ranged from 0.000 to 0.050 with a mean of 0.027. We found little pattern in the distribution of variant alleles or genetic variation; we observed only weak associations between genetic identity and geographic location. Substantial transfers of coho salmon have taken place in California, and stocks of coho from Oregon have been introduced into the State. It is difficult to assess the relative influence of these stocking practices, selection, and random processes on the genetic structure of California coho salmon populations. The genetic structure of coho salmon in California, as well as current stocking practices, indicate that genetic stock identification of California coho salmon from individual stream or localized areas may be difficult with isozyme technology. Differences among coho salmon populations from the Pacific Northwest and California may allow genetic identification of stocks from broad geographic areas.