Salmon and trout with ranges generally in waters draining to the Pacific Ocean are members of the genus. Their range extends from Beringia southwards, roughly to Japan in the west and Mexico to the east. In North America, some subspecies of O. clarki are native to the landlocked Great Basin, while others are native to the Rio Grande and western tributaries of the Mississippi River Basin which drain to the Gulf of Mexico, rather than to the Pacific.

Unlike many trout species of the mainly European genus Salmo, many Oncorhynchus are anadromous (migratory) and die after spawning . Some species of char ( Salvelinus genus) are native to Pacific waters and are also referred to as trout.

Several late Miocene (~7 m.y.a.) trout-like fossils appear in Idaho, in the Clarkia Lake beds appear to be Oncorhynchus ???the current genus for Pacific salmon and some trout. The presence of these species so far inland established that Oncorhynchus was not only present in the Pacific drainages before the beginning of the Pliocene (~5-6 m.y.a.), but also that rainbow and cutthroat trout, and Pacific salmon lineages had diverged before the beginning of the Pliocene. Consequently, the split between Oncorhynchus and Salmo (Atlantic salmon) must have occurred well before the Pliocene. Suggestions have gone back as far as the early Miocene (~20 m.y.a.).

Speciation among Oncorhynchus has been examined for decades, and to this day, a family "tree" is not completely developed for the Pacific salmonids. Mitochondrial DNA (mtDNA) research has been completed on a variety of Pacific trout and salmonid species, but the results do not necessarily agree with fossil research, or molecular research. It is generally agreed that chum , pink and sockeye salmon lineages diverged in the sequence after other species.

One interesting case involving speciation with salmon is that of the Kokanee, sockeye that have been landlocked. Kokanee sockeye evolve differently from anadromous sockeye???they reach the level of "biological species". Biological species???as opposed to morphological species???are defined by the capacity to maintain themselves in sympatry as independent genetic entities. This definition can be vexing because it appears that it does apply only to sympatry, and this limitation makes the definition difficult to apply. There are examples in Washington, Canada and elsewhere where two populations live in the same lake but spawn in different substrates, at different times, and eat different food sources. There is no pressure to compete or interbreed (two responses when resources are short). These types of Kokanee salmon show the principal attributes of a biological species: they are reproductively isolated and show strong resources partitioning.

• Oncorhynchus chrysogaster – Mexican golden trout

• Oncorhynchus clarkii – Cutthroat trout

• * Oncorhynchus clarki alvordensis – Alvord cutthroat trout ( extinct)

• * Oncorhynchus clarki bouvieri – Yellowstone cutthroat trout

• * Oncorhynchus clarki behnkei – Snake River fine-spotted cutthroat trout

• * Oncorhynchus clarki clarki – Coastal cutthroat trout

• ** Oncorhynchus clarki clarki f. crescentii – Lake Crescent cutthroat trout, Crescenti trout (sometimes O. c. crescentii )

• * Oncorhynchus clarki henshawi – Lahontan cutthroat trout

• * Oncorhynchus clarki lewisi – Westslope cutthroat trout, Black-spotted cutthroat trout

• * Oncorhynchus clarki macdonaldi – Yellowfin cutthroat trout (extinct)

• * Oncorhynchus clarki pleuriticus – Colorado River cutthroat trout

• * Oncorhynchus clarki seleniris – Paiute cutthroat trout

• * Oncorhynchus clarki stomias – Greenback cutthroat trout

• * Oncorhynchus clarki utah – Bonneville cutthroat trout

• * Oncorhynchus clarki virginalis – Rio Grande cutthroat trout

• Oncorhynchus gilae – Gila trout and Apache trout

• * Oncorhynchus gilae gilae – Gila trout

• * Oncorhynchus (gilae) apache – Apache trout, Arizona trout

• Oncorhynchus gorbuscha – Pink salmon, Humpback salmon

• Oncorhynchus keta – Chum salmon, Dog salmon, Keta salmon, Silverbrite salmon

• Oncorhynchus kisutch – Coho salmon, Silver salmon, " silvers"

• Oncorhynchus masou – Seema, Masu salmon, Cherry salmon, Japanese salmon

• * Oncorhynchus masou masou – Seema, Yamame

• ** " Oncorhynchus masou ishikawai" – Satsukimasu salmon, Red-spotted masu salmon, amago (formerly O. ishikawai , sometimes included in O. masou masou )

• ** Oncorhynchus masou var. iwame – Iwame trout, Markless trout (formerly O. iwame )

• * Oncorhynchus masou formosanus – Taiwanese salmon, Formosan landlocked salmon

• * Oncorhynchus masou rhodurus – Biwa trout

• Oncorhynchus mykiss – Rainbow trout, Steelhead, Ocean trout, Redband trout

• * Oncorhynchus (mykiss) aguabonita – Golden trout

• * Oncorhynchus mykiss gairdnerii – Columbia River redband trout

• * Oncorhynchus mykiss irideus – Coastal rainbow trout

• ** Oncorhynchus mykiss irideus f. beardsleei – Beardslee trout, " blueback" (sometimes O. m. beardsleei )

• * Oncorhynchus mykiss newberrii – Great Basin redband trout

• Oncorhynchus nerka – Sockeye salmon, Red salmon, Blueback salmon, Kokanee

• * Oncorhynchus nerka kawamurae – Kunimasu, Local Salmon, Land-locked subspecies that occurs only in Lake Tazawa (extinct)

• Oncorhynchus tshawytscha – Chinook salmon, Blackmouth, Black salmon, Chub salmon, Columbia River salmon, Hookbill salmon, King salmon, Quinnat salmon, Spring salmon, Tyee salmon, Winter salmon

Oncorhynchus rastrosus, the Sabertooth salmon (sometimes called Smilodonichthys ), was a 9-foot-(3 meter-)long species known from Late Miocene to Pleistocene fossil.

• (2002): Trout and Salmon of North America . Free Press, 2002.

• (2006): Oncorhynchus species . Version of 2006-MAR-14. Retrieved 2008-JAN-31.

• (2002): Osteichthyes. In: A compendium of fossil marine animal genera. Bulletin of American Paleontology 364 : 560. HTML fulltext

• (1993): Phylogeny of the Pacific trout and salmon ( Oncorhynchus ) and the genera of family Salmonidae. Transactions of the American Fisheries Society 122 (1): 1-33. DOI :10.1577/1548-8659(1993)122<0001:POTPTA>2.3.CO;2 HTML fulltext

• (2005) The distribution of Pacific salmon (Oncorhynchus spp.) in the Canadian western Arctic . http://www.dfo-mpo.gc.ca/Library/321160.pdf

• US mulls Pacific salmon fishing ban

• Watershed Watch Salmon Society A British Columbia advocacy group for wild salmon

• Wild Salmon in Trouble: The Link Between Farmed Salmon, Sea Lice and Wild Salmon - Watershed Watch Salmon Society. Animated short video based on peer-reviewed scientific research, with subject background article Watching out for Wild Salmon .

• Aquacultural Revolution: The scientific case for changing salmon farming - Watershed Watch Salmon Society. Short video documentary. Prominent scientists and First Nation representatives speak their minds about the salmon farming industry and the effects of sea lice infestations on wild salmon populations.

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