Chinook salmon (Oncorhynchus tshawytscha) is a member of the Pacific salmon family. It is a very large fish, reaching 108 cm in length and weighing up to 50 kg. It is mainly distributed along the American coast of the North Pacific. It enters the rivers of Kamchatka, occurs sporadically in Anadyr, and is known on the Commander Islands. Forms dwarf habitats. Matures at the age of 4-7 years. Spawns in rivers with fast currents, from June to August at depths of up to 1.5 m. Fecundity from 4.5 to 14.3 thousand eggs, up to 5-7 mm in size. Juveniles migrate to the sea in the same year, some remain in the river for up to 2 years. Adults feed on fish. Very valuable fish, commercially important.
The back, dorsal and caudal fins are covered with small roundish black spots. Chinook salmon are distinguished from other salmon by their large number of gill rays (more than 15). The mating colours are weaker than those of chum and pink salmon, and only the male becomes blackish with red spots during spawning. Small chinook salmon can be confused with silver salmon, but chinook salmon are characterised by black gums on the lower jaw and small dark spots covering not only the back and tail stalk, but also both blades of the caudal fin.
To spawn, Chinook salmon enter large rivers, often travelling long distances (up to 4,000 kilometres). It spawns from June to August, and in North American rivers it also spawns in autumn and winter. Chinook salmon spawn throughout the summer. This powerful fish is not afraid of fast currents (1-1.5 m/sec) and uses its tail to dig spawning holes in large pebbles and cobbles. The female lays up to 14,000 eggs, larger than those of chum salmon. The fry that emerge from the eggs remain in the river for a long time (from 3-4 months to 1-2 years), as do the juvenile coho salmon; some of them, especially the males, mature there and reach a length of 75-175 mm at the age of 3-7 years. There is a dwarf form, represented only by males, which reach maturity without going to sea at a length of 10-47 cm at the age of 2 years and participate in spawning on a par with the migratory males. True resident forms also occur in American rivers. In the Columbia River, Chinook salmon are represented by two forms, spring and summer.
The timing of spawning is hereditary in these forms. Chinook salmon live at sea for 4 to 7 years. It is a rather cold-loving species and prefers to fatten in the waters of the Bering Sea, adjacent to the ridge of the Commander and Aleutian Islands. In the river, juveniles feed on aerial insects and their larvae, crustaceans and juvenile fish. In the ocean, Chinook salmon feed on planktonic crustaceans, small fish and squid.
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