The Latin name for Chum salmon is Oncorhynchus keta.
The Chum salmon can grow 50–70 cm long and weigh between 2–5 kg. The Chum salmon has a fairly tall body. Like the other Pacific salmon species (Oncorhynchus), it has 12-20 fin rays in its tail fin. During the mating period, the color of the fish changes and the males form a hump on their backs and their jaws bend and can no longer be closed completely. In most cases, the body of the Chum salmon is silver-colored. The back is darker and has some indistinct dots placed in random places. When the fish are to spawn, the otherwise sivel-colored salmon turn dark olive green. The abdomen also gets darker. On the sides, flame-like patterns of stripes appear, which in the tail end are dark and in the middle violet. The males’ stomach fins turn white on the tip.
When it’s time to breed, the Chum salmon migrate upstream to spawn. They then look for shallow gravel bottoms where they can spawn with the females. After the spawning, they die.
Their main food is crustaceans, squid and other fish.
When the Chum salmon have been planted off, among other places, off Murmansk’s shores in Russia, the latter have been found in the Tana River and Näätämöjoki, where they spawn. The Chum salmon have multiplied in these waters, but it is unclear whether the salmon that come to spawn are young specimens from these rivers, or whether they were born or planted in other watercourses.
The Chum salmon are anadromous fish that live in saltwater but reproduce in freshwater and brackish water. They are usually up to 60 cm long, but there are specimens that have become up to one meter long. The heaviest Chum salmon that have been caught weighed 15.9 kg but usually weigh much less than that. The oldest Chum salmon that is documented was 7 years old. An ordinary Chum salmon lives only for four years and dies after the spawning. As soon as the Chum salmon have reached their sexual maturity, they seek to return to the freshwater to spawn. The spawning takes place at a depth of three meters. The female digs a hole of about one meter in diameter and with a depth of 50 cm before the spawning can begin. The hole is created by the female lying on one side and wagging the tail fin to remove the sand and sludge from the bottom. The female and the male place themselves in the nest and yawn with their mouths. Rapid vibrations cause the eggs and spleen to be released. The female then covers the nest. The males can spawn with several different females and can become aggressive by themselves.
The females can also spawn with several males and therefore build several different nests where the eggs can be fertilized. Within a week, the adult fish have died. Between 700-7000 eggs are fertilized during the two to three egg releases that are made. Usually 300-3500 eggs are released per spawn.
The eggs are only 6.7 mm small and thrive in a water temperature between 8-10 ° C 60 days before hatching. The fry are about 16 mm when the eggs hatch. In the spring, the young fish swim at sea and return 3-4 years later to their exact birthplace. The Chum salmon become sexually mature when they are between 2-4 years old. The fry stay at their birthplace where the spawning took place while the young fish move along the coast.