The primary purpose of this paper is to provide evidence to a hypothesis: the temporal breadth for potential spawning is so broad for male steelhead/rainbow (Salmon mykiss in Russia, Onchorynchus mykiss in North America) that it is impractical and perhaps impossible to effectively manage for temporal isolation of wild and hatchery steelhead when they cohabit mutual spawning areas. It is proposed that if this hypothesis is correct, then there has been a reshaping of wild steelhead/rainbow populations through fishery management in North America when and where management has been based on the assumption that wild and hatchery steelhead can be temporally isolated from spawning together.

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