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Oncorhynchus tshawytscha (Walbaum, 1792)
Chinook Salmon
Family: Salmonidae
Introduction to the Fish

Photograph

© Aaron Baldwin     (Photo ID #15637)

Map


Distribution of Oncorhynchus tshawytscha in British Columbia.
Source: Distribution map provided by Don McPhail for E-Fauna BC

Introduction


The Chinook Salmon is native to the rivers along the Pacific coast of both Asia and North America, and spends part of its life in freshwater rivers and streams, and part at sea. They return to the rivers to breed when they are mature. The time to maturation varies from May to August, but in BC, peak migration is generally mid-June in northern populations, although there is variation in some populations (McPhail 2007).

This is a silver-coloured species that darkens in colour as it matures. It is very similar looking to the coho salmon and can be confused with that species. McPhail 2007 indicates that "...both species have dark spots on their backs and tails. However, the black spots on the tail of the Chinook are on both the upper and lower lobes of the caudal fin, whereas in coho, the spots are confined to the upper lob of the caudal fin. Additionally, the gums at the base of the lower jaw teeth are black in Chinook and white in coho." During breeding season, these fish change to olive brown, red or purplish. As males mature, the head enlarges, however, it has a much less developed hooked nose than other salmon species (McPhail 2007).

Coho salmon spawn in more than 250 medium- to large-sized rivers and streams in BC, including the Fraser River upstream to Rear Guard Falls and the Skeena River to its headwaters (McPhail 2007). Hydroelectric dams have impacted this species, with significant loss of stock (McPhail 2007). The Okanagan population is listed as threatened in Canada by COSEWIC (2006). "The Chinook salmon (Okanagan population) are the only remaining Columbia Basin population of Chinook salmon in Canada, and are geographically, reproductively and genetically distinct from all other Canadian Chinook salmon populations.. They consist of anadromous salmon that migrate to and from the Pacific Ocean through the Columbia River, and also individuals that remain in Osoyoos Lake" (COSEWIC 2006).

Species Information

Dorsal spines (total): 0; Dorsal soft rays (total): 10 - 14; Anal spines: 0; Anal soft rays: 13 - 19; Vertebrae: 67 - 75. Distinguished by the small black spots on the back and on the upper and lower lobes of the caudal fin, and the black gums of the lower jaw (Ref. 27547). Body fusiform, streamlined, noticeably laterally compressed in large adults, somewhat deeper than other species (Ref. 6885). Gill rakers wide-spaced and rough; pelvic fins with axillary process (Ref. 27547). Fish in the sea are dark greenish to blue black on top of head and back, silvery to white on the lower sides and belly; numerous small, dark spots along back and upper sides and on both lobes of caudal; gum line of lower jaw black (Ref. 27547). In fresh water, with the approach of the breeding condition, the fish change to olive brown, red or purplish, the color change being more marked in males than in females (Ref. 27547).

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.

Biology

Species Biology

Adults return to natal streams from the sea to spawn (Ref. 27547). Fry may migrate to the sea after only 3 months in fresh water, some may stay for as long as 3 years, but generally most stay a year in the stream before migrating (Ref. 27547). Some individuals remain close inshore throughout their lives, but some make extensive migrations (Ref. 27547, 44894). Also found in lakes (Ref. 1998). Possibly up to 375 m depth (Ref. 6793). Epipelagic (Ref. 58426). Food in streams is mainly terrestrial insects and small crustaceans; in the sea, major food items include fishes, crustaceans, and other invertebrates (Ref. 27547). Young are preyed upon by fishes and birds (such as mergansers and kingfishers); adults are prey of large mammals and large birds (Ref. 1998).

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.

Distribution

BC Distribution and Notes

This is another genetically heterogeneous species and locally adapted populations are common. Apparently, much of the variation within the species is derived from the presence of two behavioural forms of Chinooks — a “stream type” and an “ocean type”. Stream type Chinooks have a relatively long period of freshwater residence (one or more years), at sea they make major offshore migrations, and they return to their natal rivers in the spring or summer. In contrast, ocean type Chinook usually migrate to sea within about three months of emergence, they spend most of their ocean life in inshore waters, and they return to their natal streams in the fall. From a biodiversity perspective, any management plans for this species should attempt to preserve a wide range of these life history variants.

Source: Information provided by Don McPhail for E-Fauna BC.
Global Distribution

Arctic, Northwest to Northeast Pacific: drainages from Point Hope, Alaska to Ventura River, California, USA; occasionally strays south to San Diego in California, USA. Also in Honshu, Japan (Ref. 6793), Sea of Japan (Ref. 1998), Bering Sea (Ref. 2850) and Sea of Okhotsk (Ref. 1998). Found in Coppermine River in the Arctic. Several countries report adverse ecological impact after introduction.

Source: FishBase. Page, L.M. and B.M. Burr 1991 A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p.
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Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
NativeS4No StatusNot Listed



BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Notes

Read more about the Chinook salmon in Don McPhail's book The Freshwater Fishes of British Columbia (2007), published by The University of Alberta Press.

Additional Range and Status Information Links

NatureServe Explorer
 University of Alaska Museum

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