A distinctive microsatellite locus that differentiates ocean-type from stream-type Chinook salmon in the interior Columbia River basin

Chinook salmon Oncorhynchus tshawytscha display two life history strategies that are referred to as ocean type and stream type. Ocean-type Chinook salmon typically differ from stream-type fish in juvenile migration timing, adult spawning location, and run timing. Spatial and temporal separation during spawning can lead to reproductive isolation and genetic divergence between the two life history strategies. We identified a distinctive microsatellite locus, OtsG474, capable of distinguishing ocean-type from stream-type Chinook salmon in 93% of the samples collected from various rivers within the interior Columbia River basin (east of the Cascade Mountains). Allele frequencies at OtsG474 revealed major differences in the dominant allele as well as in the number of alleles detected in each type. This distinctive marker may be highly useful as part of a suite of microsatellite loci, allowing managers to detect the two types of Chinook salmon in the Columbia River basin. Further research is necessary to determine the ability of this locus to discriminate Chinook salmon types in the lower Columbia River and other river basins coastwide.