Pacific Slope from Kuskokwim River drainage in Alaska to Otay River drainage in California, USA. Widely introduced and established in Canada and USA, including Arctic, Atlantic, Great Lakes, Mississippi River, and Rio Grande basins, and elsewhere in the world (Ref. 86798). Eastern Pacific: Kamchatkan Peninsula and have been recorded from the Commander Islands east of Kamchatka and sporadically in the Sea of Okhotsk as far south as the mouth of the Amur River along the mainland. The records outside Kamchatka probably represent migrating or straying Kamchatkan steelhead (penshinensis) rather than the established native population (Reg. 50080). Several countries report adverse ecological impact after introduction.