Spawn taking on one-year-old red seabream Pagrus major reared in net cage.

概要

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The red seabream <I>Pagrus major</I> is one of the important species in Japan. It is well known that this species mature at the age of two around the main lands of Japan. In Chichi-jima Island, one of the Ogasawara (Bonin) Islands where locates about 1, 000km south of Tokyo, this species spawn in May 1985 even at one year old. The data on the egg taking from this species are presented here, and the quality and quantity of the eggs are discussed comparing with those of older brood fishes (2 to 4 years) .<BR>Coastal sea water temperature around Chichi-jima Island is ranging between about 18 and 29°C. In Chichi-jima Island, the red seabream grows 1.5 to 2 times as fast as in the main lands of Japan. The shorter maturation period may be associated with high water temperature in Chichi-jima Insland.<BR>The average diameter of eggs taken from one-year-old female were varied from 0.76 to 0.84mm, and were smaller abaut 0.1mm than those from older females. However, the rate of floating eggs and hatchability were higher than those from older female and abnormality was low.
日本水産増殖学会の論文