Rearing of Brood fish and Egg-taking from the Carangid fish Seriola rivoliana in Chichi-jima, Ogasawara Islands, Southern Japan.

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Rearing conditions leading to natural spawning of the carangid fish <I>Seriola rivoliana</I> in the Tokyo Metropolitan Ogasawara Fisheries Center in 1988 and 1989 are reported. High quality eggs were obtained from wild brood fish reared without artificial treatments such as hormonal or water temperature manipulation to induce maturation and spawning. Brood fishes were usually fed formula food floured with minced fish, mackerel scarf or mackerel. During the spawning season, squid and krill, which are low calory foods, were fed to improve the egg quality and reduce the value of condition factor. The size of brood fish ranged 61.3-82.2 cm in fork length and 4.8-12.5 kg in body weight. Almost all spawning occurred at daybreak. Spawnings were observed between April and November, and were particularly frequent between June and October. The total amount of eggs obtained in 1988 and 1989 was approximately 152 million with an average daily production of 0.5-1 million eggs. Water temperature during the spawning season varied between 21.4 °C and 28.1 °C. The optimum water temperaure for spawning was estimated to be between 24.1 and 27.0 °C. The average rates of buoyant eggs and hatching were 47.6±30.1% and 69.3±25.0%, respectively. Egg diameter ranged from 1.03 to 1.13 mm (average: 1.09 mm) .
日本水産増殖学会の論文