アマゴにおける半野生魚の放流効果の検証

摘要

Farmed salmonids that have completed a full life-cycle in the hatchery have been stocked in streams by fisheries cooperative associations since the 1970s in Japan.However, recent studies suggest a lower survival rate of farmed salmonids than wild ones.In the present study, we produced “semi-wild“(hybrids of farmed females and wild males)red-spotted masu salmon Oncorhynchus masou ishikawae and compared the variability of growth between the semi-wild and farmed salmon in five hatcheries, and their survival rates after being stocked in streams.A larger coefficient of variation of semi-wild than farmed salmon was observed in four hatcheries, which suggested that domesticated individuals may be decreased in semi-wild salmon. The survival rate of semi-wild salmon was assumed to be higher than farmed salmon after stocking in streams.Our results show that juveniles fertilized by the sperm of wild males may be modestly adaptable for the stream environment.