Because the native salmon in Lake Clearwater had nearly disappeared, sockeye salmon were introduced in 1940  After being introduced, this genetically uniform group of sockeyes split into two distinct populations that do not interbreed, one inhabiting deep areas of the lake and the other inhabiting shallow areas
Since the two populations now differ genetically, some researchers hypothesize that each has adapted genetically to its distinct habitat
Neither of the two populations of sockeyes has interbred with the native salmon.