Evidence for the existence of a native population of sockeye salmon (Oncorhynchus nerka) and subsequent introgression with introduced populations in a Pacific Northwest watershed

The Lake Washington watershed (Washington, USA) has been the recipient of numerous transplantations of nonnative Oncorhynchus nerka (both sockeye salmon and their landlocked form, kokanee) over the past century and currently contains self-sustaining populations of both ecotypes. Microsatellite DNA markers were used to identify native and introduced groups while characterizing population structure. This study confirmed that Baker Lake sockeye transplantations during the 20th century contributed to three current sockeye populations: Cedar River, Issaquah Creek, and Pleasure Point Beach in the Lake Washington watershed. Distinctive allele distributions at two loci. One101 and One114, provide evidence that a fourth Lake Washington sockeye population, Bear Creek, is divergent from other Lake Washington sockeye and may be of substantially native origin despite heavy stocking activity in the watershed over the past century. Data from these loci also suggest the presence of native genes in populations that had been regarded as entirely of introduced origin.