Chinook salmon

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n.
A very large, commercially valuable salmon (Oncorhynchus tshawytscha) of northern Pacific waters, characterized by irregular black spots on its back. Also called king salmon, quinnat salmon.

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Oncorhynchus tshawytscha

FAMILY

Salmonidae

TAXONOMY

Salmo tshawytscha Walbaum, 1792, rivers of Kamchatka, Russia.

OTHER COMMON NAMES

English: King salmon, Pacific salmon; French: Saumon chinook; German: Königslachs; Spanish: Salmón chinook.

PHYSICAL CHARACTERISTICS

Length 59 in (150 cm); weight 136.36 lb (61.4 kg). The fusiform body is streamlined and laterally compressed among large adults. Important distinguishing characteristics are small black spots on the back and the upper and lower lobes of the caudal fin, as well as on the black gums of the lower jaw. The gill rakers are widely spaced and rough. Coloration varies with environmental conditions. At sea, adults are dark greenish to blue black on top of head and back and silvery to white on the lower sides and belly; they also present numerous small and dark spots along back and upper sides and on both lobes of the caudal fin. In fresh water, they acquire an olive brown to red or purplish coloration, which is particularly noticeable among males.

DISTRIBUTION

Arctic and Pacific regions, in the drainages from Point Hope, Alaska to California, United States, as well as Japan, the Bering Sea, and the Okhotsk Sea. Successfully introduced in Australia, New Zealand, and Chile.

HABITAT

Similar to that of other salmoniforms; however, in lakes they may inhabit depths down to 1,230 ft (375 m).

BEHAVIOR

Like other salmoniforms, adults show a strong homing behavior. Their migratory behavior varies greatly. Usually, after three months in fresh water, most fry migrate to the sea, although some may stay in fresh waters for as long as three years. Some individuals remain close inshore throughout their lives, others make extensive migrations.

FEEDING ECOLOGY AND DIET

Food in streams consists mainly of terrestrial insects and small crustaceans; at sea major food items include fishes, crustaceans, and other invertebrates. The young are preyed upon by fishes and birds, such as mergansers and kingfishers; adults are preyed upon by sharks, large mammals (including killer whales), and birds.

REPRODUCTIVE BIOLOGY

Anadromous adults can migrate nearly 3,100 mi (5,000 km) from the ocean upstream to spawn. In December adults start to migrate from the sea, so that by early spring the first individuals arrive near the river mouths. The female is in charge of selecting the spawning spot where she will dig her nest, and aggressively drives away other females competing for the same spot. Once she has established her territory, a dominant male and several smaller males join her, at the same time driving away other males that compete for her. Male courtship behavior includes resting beside the female, quivering, swimming around over her, touching her dorsal fin with his body and fins, and occasionally nudging her side gently with the snout. Once the nest is complete, the female drops into it, and is immediately joined by the dominant male. Both open their mouths, vibrate, and eggs and sperm are released. At this point smaller males may swim into the nest and release their own sperm. (It is unclear to what extent these smaller males play a role in fertilizing the eggs.) The female then quickly covers the eggs by moving to the upstream edge of the nest and digging small pebbles for a new nest. This process, which may last several days, is repeated several times, until the female releases all her eggs. The female guards the nest for as long as she can. The male leaves the female and may mate with another female. Spent adults usually die a few days after spawning.

CONSERVATION STATUS

Not listed by the IUCN. The Alaskan fishery of this species has been certified by the Marine Stewardship Council as well managed and sustainable.

SIGNIFICANCE TO HUMANS

Highly regarded commercial and game fishes, whose red meat commands a high price. The viscera are rich in vitamin A and are used as food for hatchery fish.

[shih-NUHK] see salmon

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Last updated December 09, 2009 22:49 (EST)

oncorhynchus tshawytscha.

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