Natural spawning from 2-Year-Old Reared Amberjack, Seriola dumerili in Chichijima Ogasawara Islands, Southern Japan.

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Spawning of 2-year-old amberjack, <I>Seriola dumerili</I> reared from hatching was tried in Chichijima, one of the Ogasawara Islands. Rearing methods and characteristics of fertilized eggs were examined. During the rearing, from July 1994 to June 1996, mean monthly water temperatures ranged between 19.0 and 28.3°C (mean 23.8°C) . Fork length and body weight of one-year old fish were 46.3±1.7 cm and 1, 973±210g, and those of two-year old were 67.8±3.1cm and 7, 258±1, 049g, respectively. Mean daily feeding rate for the first year was 6.4% and dropped to 2.4% for the second year. Mean daily growth rate for the first year was 0.9% and dropped to 0.3% for the second year. Mean food conversion efficiencies for the first and second years were 12.2% and 13.6%, respectively. The spawning was observed between May and June. No artificial treatments such as hormonal injection or temperature shock were required to induce maturation and spawning. The total number of eggs obtained was approximately 10 millions. Water temperature varied between 20.3°C and 23.6°C during the spawning season. Optimum water temperature for the spawning was estimated to be between 22.0°C and 23.4°C. Floating egg rate was 82.9±8.2% and hatching rate was 97.1±2.9%. Egg diameter was 1.10±0.02 mm and oil globule was 0.26±0.01mm.
日本水産増殖学会の論文