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chum salmon[′chəm ‚sa·mən]
(Oncorhynchus keta), also keta or dog salmon, a migratory fish of the genus Oncorhynchus (Pacific salmon). Maximum length, 1 m; maximum weight, 14 kg.
The chum salmon is found in the northern Pacific Ocean along the Asian coast south to Korea and Honshu and along the American coast to Monterey Bay. In the spring it migrates north, putting on weight. Small numbers of the species are found in rivers of the Arctic Basin, from the Lena to the Mackenzie. The chum salmon feeds on crustaceans, pteropods, and fry (sand lancets, smelts, and herrings).
The chum salmon reaches maturity in its fourth or fifth year. In order to reproduce, the fish enter a river and stop eating. During the reproduction period they acquire a spawning livery, which is more clearly manifested in the males than in the females. The height of the body increases, the body becomes darker and transverse magenta stripes appear on it, the jaws become elongated and bend, and the fish grows powerful teeth. There are summer and autumn forms of the chum salmon. In the Amur the autumn form is larger and more fecund than the summer form. (It may lay 3,000–4,500 eggs.) The autumn form may swim as far as 2,000 km upstream. It reproduces at the outlets of springs between September and December. The summer chum salmon does not swim as far upstream. It spawns in July and August. Where the current is swift and the riverbed pebbly, the females beat out holes with their tails, deposit the eggs, sprinkle them with pebbles, and guard them for several days. After spawning, the fish dies. The eggs usually develop for 60–120 days. After the eggs hatch, the embryos stay in the nests until spring. The young fish stay in the rivers about a month, feeding chiefly on the aquatic larvae of insects.
A valuable commercial fish, the chum salmon may be salted, smoked, or tinned. It is also a source of valuable red caviar. Catches of chum salmon fluctuate sharply from year to year. Japan’s irrational fishing policy has a negative effect on the supply of chum salmon. In the USSR the fish may be caught along the coast, but fishing for them in the rivers is prohibited, and their spawning grounds are being improved. Soviet fisheries release hundreds of millions of fry.
REFERENCESKuznetsov, I. I. Keta i ee vosproizvodstvo. Khabarovsk, 1937.
Berg, L. S. Ryby presnykh vod SSSR i sopredel’nykh stran, 4th ed., part 1. Moscow-Leningrad, 1948.
Nikol’skii, G. B. Chastnaia ikhtiologiia, 3rd ed. Moscow, 1971.
A. I. SMIRNOV