Some features of natural spawning and problems of artificial reproduction of the cherry salmon Oncorhynchus masou (Brevoort, 1856)

Abstract

The article discusses certain aspects of the dispersal and biology of cherry salmon, Oncorhynchus masou (Brevoort, 1856). It is noted that the species is the southernmost within the Pacific Salmon family and is also the only member of the Oncorhynchus genus whose habitat is exclusively in Asia. The decline in the number of cherry salmon across their range has been highlighted, and the main underlying factors have been identified. Some features of cherry salmon spawning run in various parts of their range are examined. A long stay of spawners in fresh water before spawning with preservation of feeding behavior is noted, which makes the species an extremely compelling object of recreational and commercial fishing. Some features of natural reproduction, such as spawning timing and fertility, depending on the habitat and size of the spawners, are indicated. The issue of preserving and restoring the species population is touched upon; the most appropriate method of its implementation is the artificial reproduction of the young with subsequent release into the natural habitat. The paper highlights a number of obstacles to the implementation of such programs, such as the undeveloped technology for growing young masu salmon and the difficulty of optimizing the temperature regime at hatcheries. As one of the limitations to increasing release volumes, it is indicated that masu salmon belongs to a species that have a long freshwater period, with the young spending up to three years in the river. A large number of juvenile masu salmon in the river leads to insufficient food supply and high mortality. In order to overcome this factor, it has been proposed to conduct research aimed at stimulating the smoltification of hatchery salmon fingerlings. This measure will allow significantly increasing the number of smolt and the return rates of spawners, which can be removed without affecting the natural populations.