Sockeye or red salmon (Oncorhynchus nerka)
The size and body shape of bright sockeye is closer to chum than to other salmon. Sockeye has small black dots on the back and very bright, silver scales, each outlined with a dark edge. It’s also easy to distinguish sockeye by the number of gill rakers: chum can have between 18 and 28, but sockeye always have more than 30 and normally 34–40 gill rakers. Dark, spawning sockeye with a bright red body and green head is very attractive.
Contrary to other Pacific salmon, most sockeye stocks reproduce in clear lakes or in the tributaries of such lakes. This species has a very strong homing instinct: it comes back not only to the native lake but even to the very spawning ground where the fish was born. On the way to the native lake, migrating sockeye can do heroic wonders. Some population reproduce in the lakes located at an altitude of 800 m – 1000 m over the sea level. In some drainages, there are stocks of sockeye reproducing in the rivers – on the same type of spawning grounds as chum salmon. Behavioral patterns of this salmon in rivers are also similar to chum.
Sockeye are the earliest anadromous fish running into the rivers of the Russian Far East — on the Kamchatka Peninsula some salmon can enter on the first days of May. This is the spring run; the second, summer run occurs at the end of June and in July.
Sockeye fry live in lakes from one to three years; the sea-feeding period of the species can also last from one to three years. Both in fresh and salt water, sockeye feed on zooplankton.
A lot of red salmon enter the Okhota River on the north coast of the Sea of Okhotsk. There are big populations of the species in the Kamchatka Peninsula, both in the east in the Kamchatka River drainage and in the southwest – in the Kurilskoe Lake. Lots of sockeye enter the Palana River in the northwest of the peninsula. Red salmon are also numerous in some lakes of Koryak Upland (Mainopilgino) and Chukotka peninsula (Achchen).
Like Chinook and cherry salmon, small anadromous males (grilse) and lake-resident dwarf males are present in sockeye stocks. In some waters, there are lake-resident stocks of this species, called kokanee. The biggest kokanee stock in Asia reproduces in huge Kronotskoe Lake in the eastern Kamchatka. Kokanee is a small salmon not more than 30 cm long. Both males and females die after their first spawning.