The Spring-Run Ecotype of the Steelhead Trout Parasalmo ( Oncorhynchus ) mykiss (Walbaum, 1792) (Salmonidae, Salmoniformes) in the Kamchatka Peninsula

A seasonal spring-run (vernal) ecotype of the Steelhead Trout Parasalmo ( Oncorhynchus ) mykiss (Walbaum, 1792) has been found in western Kamchatka for the first time. Fish of this ecotype perform anadromous migration in May; however, the timing and grounds of spawning of the spring- and fall-run (hiemal) ecotypes in Kamchatka completely overlap. An analysis of microsatellite loci of both ecotypes has shown no differences between them; therefore, they are suggested to represent a single population. The spring- and fall-run steelhead of Kamchatka are not analogous to the winter- and summer-run steelhead of North America. The spring-run ecotype of anadromous steelhead from Kamchatka rivers can be considered a temporal adaptive form that appeared during the warm periods of the large-scale climate and ocean fluctuations in the North Pacific.