A number of subspecies are known, including the widespread nominate subspeciesyamame (O. m. masou), the critically endangered Formosan salmon (O. m. formosanus) in landlocked waters of Taiwan, the Biwa trout (O. m. rhodurus) endemic of Lake Biwa, and the anadromousamago (O. m. macrostomus) restricted to western Japan.
Appearance
Oncorhynchus masou
A masu salmon which has reached sexual maturity has a darkened back, 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. For this reason, it was given the name cherry salmon.
As adults, masu salmon tend to weigh 2.0 to 2.5 kg (4.4 to 5.5 lb) and measure roughly 50 cm (20 in) in length.[3] The maximum size that can be attained by this species (which is in the region of Primorsky Krai) is 71 cm (28 in) long and 9 kg (20 lb) in weight.
Ecology
On average, this salmon prefers a temperate climate around the latitude of 65-58°N, and in the sea, it prefers a depth of 0–200 m (0–656 ft).
Like other Pacific salmon, masu salmon’s biological life cycle is subdivided into freshwater and marine periods; in rivers, this species lives from 1 to 3 years and can form living freshwater forms. The sea lifecycle, depending on the age of the young, continues for 2.0 to 3.5 years. In the sea, the masu salmon feeds intensely on crustaceans, less often on young fish. On attaining sexual maturity, in its third to seventh years of life, it enters rivers to spawn. Its spawning run starts earlier than that of other salmon species.
After spawning, most passing fish die, and those that remain alive (preferentially dwarf males) participate in spawning the next year, too. Emerging from the nest, the young do not travel to the sea immediately, 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 chironomids, stone flies, and may fly larvae, and on airborne insects. The masu salmon travels to the ocean in its second, or occasionally even third year of life.
This salmon, like most others, is a highly commercial species caught in fisheries, raised for aquaculture, and sought after as a game fish. It is marketed fresh and frozen and is often eaten broiled or baked.
O. m. macrostomus — Red-spotted masu salmon; endemic to western Japan
O. m. formosanus — Formosan salmon, Lishan trout (Chinese: 梨山鱒) or Slamaw trout (the Tayal name for Lishan), landlocked form endemic to mountainous central Taiwan
