Scientific name: Oncorhynchus mykiss (Walbaum, 1792).
Environment: Marine; freshwater; brackish; benthopelagic; anadromous.
Distribution: Native to Pacific Slope from Kuskokwim River, Alaska to (at least) Rio Santa Domingo, Baja California, Mexico; upper Mackenzie River drainage (Arctic basin), Alberta and British Columbia in Canada; endorheic basins of southern Oregon, USA. Widely introduced in cold waters elsewhere in North America and rest of the world. 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 rather than the established native population.
Biology: Inhabits cold headwaters, creeks, small to large rivers, and lakes. Anadromous in coastal streams. Stocked in almost all water bodies as lakes, rivers and streams, usually not stocked in water reaching summer temperatures above 25°C or ponds with very low oxygen concentrations. Feeds on a variety of aquatic and terrestrial invertebrates and small fishes. At the sea, preys on fish and cephalopods. Undertakes short spawning migrations. Anadromous and lake forms may migrate long distances to spawning streams.