Editing Rainbow trout (section)

{{Short description|Fresh-water species of fish}}
{{pp-pc1}}
{{Featured article}}
{{Speciesbox
| image = Close up of rainbow trout fish underwater oncorhynchus mykiss.jpg
| image_alt = Close up of rainbow trout fish underwater oncorhynchus mykiss
| image_caption = Adult rainbow trout
| status = LC
| status_system = IUCN3.1
| status_ref = <ref>{{cite iucn |author1=Hammerson, G.A. |author2=Bogutskaya, N. |date=2024 |title=''Oncorhynchus mykiss'' |volume=2024 |issue=2 |page=e.T166481A18229476 |doi= |access-date=22 March 2025}}</ref>
| status2 = G5
| status2_system = TNC
| status2_ref = <ref>{{cite web |url=https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.105164/Oncorhynchus_mykiss |title=Rainbow Trout |date=10 May 2016 |website=Natureserve.org |access-date=28 October 2021}}</ref>
| genus = Oncorhynchus
| species = mykiss
| authority = ([[Johann Julius Walbaum|Walbaum]], 1792)
| synonyms = {{collapsible list|title=<small>''previous scientific names''</small>|hlist=true|
{{nowrap|''Salmo mykiss'' <small>Walbaum, 1792</small>}}
{{nowrap|''Parasalmo mykiss'' <small>(Walbaum, 1792)</small>}}
{{nowrap|''Salmo purpuratus'' <small>[[Peter Simon Pallas|Pallas]], 1814</small>}}
{{nowrap|''Salmo penshinensis'' <small>Pallas, 1814</small>}}
{{nowrap|''Parasalmo penshinensis'' <small>(Pallas, 1814)</small>}}
{{nowrap|''Salmo gairdnerii'' <small>[[John Richardson (naturalist)|Richardson]], 1836</small>}}
{{nowrap|''Fario gairdneri'' <small>(Richardson, 1836)</small>}}
{{nowrap|''Oncorhynchus gairdnerii'' <small>(Richardson, 1836)</small>}}
{{nowrap|''Salmo gairdnerii gairdnerii'' <small>Richardson, 1836</small>}}
{{nowrap|''Salmo rivularis'' <small>[[William Orville Ayres|Ayres]], 1855</small>}}
{{nowrap|''Salmo iridea'' <small>Gibbons, 1855</small>}}
{{nowrap|''Salmo gairdnerii irideus'' <small>Gibbons, 1855</small>}}
{{nowrap|''Salmo irideus'' <small>Gibbons, 1855</small>}}
{{nowrap|''Trutta iridea'' <small>(Gibbons, 1855)</small>}}
{{nowrap|''Salmo truncatus'' <small>[[George Suckley|Suckley]], 1859</small>}}
{{nowrap|''Salmo masoni'' <small>Suckley, 1860</small>}}
{{nowrap|''Oncorhynchus kamloops'' <small>[[David Starr Jordan|Jordan]], 1892</small>}}
{{nowrap|''Salmo kamloops'' <small>(Jordan, 1892)</small>}}
{{nowrap|''Salmo rivularis kamloops'' <small>(Jordan, 1892)</small>}}
{{nowrap|''Salmo gairdneri shasta'' <small>Jordan, 1894</small>}}
{{nowrap|''Salmo gilberti'' <small>Jordan, 1894</small>}}
{{nowrap|''Salmo nelsoni'' <small>[[Barton Warren Evermann|Evermann]], 1908</small>}}
}}
| synonyms_ref = <ref>{{cite web |url=http://www.fishbase.org/Nomenclature/SynonymsList.php?ID=239&SynCode=22919&GenusName=Oncorhynchus&SpeciesName=mykiss |title=Synonyms of Oncorhynchus mykiss (Walbaum, 1792) |publisher=Fishbase |access-date=2014-02-06}}</ref>
}}
{{Conservation status}}

The '''rainbow trout''' ('''''Oncorhynchus mykiss''''') is a species of [[trout]] native to cold-water [[tributary|tributaries]] of the Pacific Ocean in North America and Asia. The '''[[steelhead]]''' (sometimes called '''steelhead trout''') is an [[Fish migration#Classification|anadromous]] (sea-run) form of the '''coastal rainbow trout''' {{nowrap|(''O. m. irideus'')}} or [[Columbia River redband trout]] {{nowrap|(''O. m. gairdneri'')}} that usually returns to freshwater to [[Spawn (biology)|spawn]] after living two to three years in the ocean.

Adult freshwater stream rainbow trout average between {{convert|1|and|5|lb|kg|round=0.5|order=flip}}, while lake-dwelling and anadromous forms may reach {{convert|20|lb|kg|0|order=flip|abbr=on}}. Coloration varies widely based on [[subspecies]], forms, and [[habitat]]. Adult fish are distinguished by a broad reddish stripe along the [[lateral line]], from [[gill]]s to the tail, which is most vivid in breeding males.

Wild-caught and [[Fish hatchery|hatchery]]-reared forms of the species have been transplanted and introduced for food or sport in at least 45 countries and every continent except Antarctica. Introductions to locations outside their native range in the United States, Southern Europe, Australia, New Zealand, and South America have damaged native fish species. Introduced populations may affect native species by preying on them, out-competing them, transmitting contagious diseases (such as [[Myxobolus cerebralis|whirling disease]]), or [[Hybrid (biology)|hybridizing]] with closely related species and subspecies. The rainbow trout is included in the [[100 of the World's Worst Invasive Alien Species|list of the top 100 globally invasive species]]. Other introductions into waters previously devoid of fish or with severely depleted stocks of native fish have created [[Recreational fishing|sport fisheries]], such as the Great Lakes and [[Wyoming]]'s [[Firehole River]].

Some local populations of specific subspecies, or in the case of steelhead, [[distinct population segment]]s, are listed as either [[Threatened species|threatened]] or [[Endangered species|endangered]] under the [[Endangered Species Act of 1973|Endangered Species Act]]. The steelhead is the official [[List of U.S. state fish|state fish]] of [[Washington (state)|Washington]].<ref>{{cite web |url=http://www.leg.wa.gov/symbols/pages/default.aspx |title=Symbols of Washington State |publisher=Washington State Legislature |access-date=2013-11-29}}</ref><!-- note web site specifies Salmo gairdnerii, just to further confuse matters -->