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Salmon is the common name for several species of fish in the family Salmonidae. Other fish in the same family include trout, char, grayling and whitefish. Salmon are native to tributaries of the North Atlantic (genus ''Salmo'') and Pacific Ocean (genus ''Oncorhynchus''). Many species of salmon have been introduced into non-native environments such as the Great Lakes of North America and Patagonia in South America. Salmon are intensively produced in aquaculture in many parts of the world. Typically, salmon are anadromous: they are born in fresh water, migrate to the ocean, then return to fresh water to reproduce. However, populations of several species are restricted to fresh water through their lives. Various species of salmon display anadromous life strategies while others display freshwater resident life strategies. Folklore has it that the fish return to the exact spot where they were born to spawn; tracking studies have shown this to be mostly true. A portion of a returning salmon run may stray and spawn in different freshwater systems. The percent of straying depends on the species of salmon. Homing behavior has been shown to depend on olfactory memory.〔(ncbi.nlm.nih.gov ), Scholz AT, Horrall RM, Cooper JC, Hasler AD. Imprinting to chemical cues: the basis for home stream selection in salmon. Science. 1976 Jun 18;192(4245):1247-9.〕〔(ncbi.nlm.nih.gov ), Ueda H. Physiological mechanism of homing migration in Pacific salmon from behavioral to molecular biological approaches. Gen Comp Endocrinol. 2010 Feb 6.〕 == Species == The term "salmon" comes from the Latin ''salmo'', which in turn may have originated from ''salire'', meaning "to leap".〔(Salmon etymonline.com ), ''Online Etymology Dictionary''. Retrieved 25 April 2012.〕 The nine commercially important species of salmon occur in two genera. The genus ''Salmo'' contains the Atlantic salmon, found in the north Atlantic, as well as many species commonly named trout. The genus ''Oncorhynchus'' contains eight species which occur naturally only in the North Pacific. As a group, these are known as Pacific salmon. Chinook salmon have been introduced in New Zealand and Patagonia. Coho, freshwater sockeye, and Atlantic salmon have been established in Patagonia, as well. † Both the ''Salmo'' and ''Oncorhynchus'' genera also contain a number of species referred to as trout. Within ''Salmo'', additional minor taxa have been called salmon in English, i.e. the Adriatic salmon (''Salmo obtusirostris'') and Black Sea salmon (''Salmo labrax''). The steelhead anadromous form of the rainbow trout migrates to sea, but it is not termed "salmon". Also a number of other species have common names which refer to them as being salmon. Of those listed below, the Danube salmon or ''huchen'' is a large freshwater salmonid related to the salmon above, but others are marine fishes of the unrelated Perciformes order: ''Eosalmo driftwoodensis'', the oldest known salmon in the fossil record, helps scientists figure how the different species of salmon diverged from a common ancestor. The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred by 10 to 20 million years ago. This independent evidence from DNA analysis and the fossil record rejects the glacial theory of salmon divergence.〔Montgomery, David. ''King Of Fish'' Cambridge, MA: Westview Press, 2004. 27.28. Print.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Salmon」の詳細全文を読む スポンサード リンク
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