Chinook Salmon (Oncorhynchus tshawytscha)


The chinook salmon is one of the most important sportfish and commercial fish in the world, especially, and historically, to the Pacific coast of North America, where this and other salmonids have long had great cultural and food significance. It is the largest member of the Salmonidae family and both the largest and the least-abundant member of the Pacific salmon genus Oncorhynchus.

Pacific stocks of chinook, as well as of other Pacific salmonids, however, have suffered greatly throughout large portions of their range due to dams, other habitat alterations, pollution, and excessive commercial fishing. Some chinook runs in the Pacific Northwest are threatened or endangered.

Identification

The body of the chinook salmon is elongate and somewhat compressed. The head is conical. For most of its life, the chinook’s color is bluish to dark gray above, becoming silvery on the sides and the belly. There are black spots on the back, the upper sides, the top of the head, and all the fins, including both the top and the bottom half of the tail fin.

Coloration changes during upstream migration; spawning chinook salmon range from red to copper to olive brown to almost black, depending on location and degree of maturation, and they undergo a radical metamorphosis.

Males are more deeply colored than the females and are distinguished by their “ridgeback” condition and by their hooked nose or upper jaw, known as a kype. The young have 6 to 12 long, wide, well-developed parr marks, which are bisected by the lateral line, and no spots on the dorsal fin.

One distinguishing feature of the chinook is its black mouth and gums. The very similar-looking coho salmon has a black mouth but white gums.

Size

This species is the largest of all Pacific salmon; individual fish commonly exceed 30 pounds in Alaska and British Columbia and 20 pounds elsewhere. A 126-pound chinook salmon taken in a fish trap near Petersburg, Alaska, in 1949 is the largest known specimen. The all-tackle world-sportfishing record is a 97-pound, 4-ounce fish caught in Alaska’s Kenai River in 1986.

Life history/Behavior

Like all species of Pacific salmon, chinook are anadromous. They hatch in freshwater rivers, spend part of their lives in the ocean, and then spawn in freshwater. Sea-run chinook salmon may become sexually mature from their second through seventh year; as a result, fish in any spawning run may vary greatly in size.

Chinook salmon often make extensive freshwater spawning migrations to reach their home streams on some of the larger coastal river systems. Yukon River spawners bound for the extreme headwaters in Yukon Territory, Canada, will travel more than 2,000 river miles during a 60-day period. The period of migration into spawning rivers and streams varies greatly. Alaskan streams normally receive a single run of chinook salmon from May through July.

Chinook salmon do not feed during their freshwater spawning migration, so their condition deteriorates gradually during the spawning run. During that time, they use stored body materials for energy and for the development of reproductive products. Each female deposits from 3,000 to 14,000 eggs (usually in the lower range) in several gravel nests, or redds, which she excavates in relatively deep, moving water.

The eggs usually hatch in the late winter or the early spring, depending on the time of spawning and the water temperature. The newly hatched fish, called alevins, live in the gravel for several weeks until they gradually absorb the food in the attached yolk sac.

These juveniles, called fry, wiggle up through the gravel by early spring. Most juvenile chinook salmon remain in their natal water until the following spring, when they migrate to the ocean in their second year of life. These seaward migrants are called smolts.

Food and feeding habits

Chinook salmon in the ocean eat a variety of organisms, including herring, pilchards, sand lance, squid, and crustaceans. Salmon grow rapidly in the ocean and often double their weight during a single summer season. Thus, they quickly develop large, stocky bodies.

Other Names

king salmon, spring salmon, tyee, quinnat, tule, blackmouth, Sacramento River salmon, Columbia River salmon; French: saumon chinook, saumon royal; Japanese: masunosuke.

Distribution/Habitat

In North America, chinook salmon occur naturally from San Luis Obispo County in Southern California to the Chukchi Sea area of Alaska; the greatest concentrations are along the British Columbia coast and Alaska. In Alaska, where the chinook is the state fish, it is abundant from the southeastern panhandle to the Yukon River.

Major populations return to the Yukon, the Kuskokwim, the Nushagak, the Susitna, the Kenai, the Copper, the Alsek, the Taku, and the Stikine Rivers. Important runs also occur in many smaller streams.

The chinook is rare in the Arctic Ocean. Most sea-run chinook are encountered by anglers along the coasts and in spawning rivers. Scientists estimate that there are in excess of a thousand spawning populations of chinook salmon on the North American coast.

Scientific understanding of the distribution of chinook in the ocean is still sketchy. It has been speculated that most North American chinook do not wander more than 620 miles from their natal river, and that fish from western Alaska streams roam farther than others from North America. Large numbers are found relatively close to their respective shores and also in distant offshore waters, and their depth preferences vary.
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