仔魚床の有無・飼育密度の違いがサクラマス仔魚の成長・生残に及ぼす影響

Abstract

We investigated the impacts of incubation substrate and rearing density on the growth and survival of masu salmon (Oncorhynchus masou) alevins. Eyed eggs of masu salmon were stocked in incubation tanks at different egg densities with or without gravel substrate. The survival rate from eggs to emergent fry did not differ depending on the presence of gravel substrate, nor on the rearing density. The mean body weight of emergent fry reared with the gravel substrate was significantly heavier than that of fry at the same rearing density without gravel substrate. In the absence of gravel substrate, the mean body weight of emergent fry reared at a high density was significantly heavier than that of fry reared at a low density. These results indicate that the growth of masu salmon alevins is affected by the presence of incubation substrate as well as rearing density. The incubation substrate may restrain alevins from actively moving, promoting their efficient absorption of yolk nutrient for growth.