PrimoryeSea
 Brook masu salmon, Oncorhynchus masou
Brook masu salmon      Passing species, occurring everywhere in Primorye waters. The southernmost and most warm-water representative of Pacific salmon, widespread preferentially in Japan Sea basin. Enters rivers of Korea, Primorye, Japan and Sakhalin to travel northward to the coasts of Kamchatka. One of the most beautiful representatives of Pacific salmon, particularly in wedding attire. Externally, the brook masu salmon resembles the gorbuscha, but differs from other salmon species by presence on its body sides of transversal stripes, lesser number of gill rays and richness of color gamut of wedding attire. When it attains sexual maturity, its back darkens, and the stripes on the body sides become bright red with crimson tinge to merge on the abdomen into one common longitudinal band of lighter color. No wonder, in English this species is also called cherry salmon. In Primorye, it grows to larger sizes than in other regions to become 71 cm long and to weigh 9 kg.
   Like in other Pacific salmon, its life cycle is subdivided into marine and freshwater periods; in rivers, this species lives from 1 to 3 years and can form living fresh-water forms. The sea life cycle, depending on the age of the young, continues for 2-3.5 years. In the sea, the cherry salmon feeds intensely on crustaceans, less often on young fish. On attaining sexual maturity, in its third through seventh years of life it enters rivers to spawn. Its spawning run starts earlier than that of other salmon species. In Primorye  it enters rivers from late May to early September. Spawning grounds are situated in river upper reaches and in brook channels. The roe is spawned into nests of 10-45 cm deep on pebbly-silty soils with weak currents. In Primorye rivers, lower spawning grounds are located 10-15 km away from river estuaries, though we know of facts when in Razdolnaya River and its tributaries the cherry salmon ascended along the current up to 100 km from the estuary. After spawning, passing fish die, and those that remain alive (preferentially dwarf males) participate in spawning next year, too. After  emerging from the nest, the young do not roll into the sea, like those of gorbuscha and keta, but remain in spawning areas, in the upper reaches of rivers, and on shallows with weak currents. The young move to pools and rolls of the river core to feed on chironomid, stone fly and may fly larvae, and on air insects. The cherry salmon rolls into the sea in its second, occasionally even third year of life.
   Young fish that live in rivers are known as  brook trout. Not infrequently, it is mistakenly taken for another species due the presence of dwarf males permanently living in the river to attain sexual maturity and take part in spawning. The cherry salmon young that had rolled into the sea would gradually depart from the coastline into open waters to return to their native rivers in two or three years. In the nineteen thirties, lots of brook trout were observed in Malaya Sedanka River near Vladivostok. It is a valuable commercial species. Among Pacific salmon occurring in Primorye, its population ranks third after keta and gorbuscha.
  
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