クロマグロおよびハガツオの3年飼育*

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[Author abstract]The long-term rearing of bluefin tuna Thunnus thynnus and bonito Sarda orientalis had been considered extremely difficult, because of their incomparably high sensitivity to the factors inevitably introduced in handling them. The authors made some trials of long-term rearing of young bluefin tuna and bonito and reached the conclusion that it was possible to rear them at least for three years. The experiments were carried out at Shirahama and Kushimoto, Wakayama Prefecture, with young bluefin tuna and bonito captured by surface trolling or trap net in late summer. In 1970 and 1971, young tuna fish captured were reared in fiber netting cages, but in 1972 (tuna and bonito), 1973 (tuna) and 1974 (tuna and bonito), fishes were reared in wire netting cages, being fed in both cases with fish meat. All the bluefin tuna captured in 1970 died from suffocation on October 25,1970, while all the fish captured in 1971 were killed by a heavy storm on January 10,1971. In 1972, forty-two young fish of bluefin tuna were captured and reared in a single wire netting cage. Four of these fish were still alive in the cage as of November 1,1975. The fish captured in late August, 1972 were about 33 cm in total length and weighed about 500 g, but found to be about 140 cm in length and 50 kg on November 1,1975. Thirty-three young fish of bonito captured in 1972, were reared in the same cage together with bluefin tuna. Four of them were still alive as of November 1, 1975. The fish captured on September, 1972 were about 40 cm in total length and weighed 675 g, but found to be about 60 cm in length and 3 kg on November 1,1975. In 1973, 208 young fish of bluefin tuna were captured and reared in a wire netting cage. Eleven of them were still alive as of November 1,1975. About 350 tuna and 30 bonito of 1460 young bluefin tuna and 53 young bonito captured in 1974 were still alive in the single cage as of November 1,1975. These records show evidently that both bluefin tuna and bonito could be reared successfully in the wire netting cages from O-age till 3-age. The growth rate was higher in bluefin tuna than bonito, while the survival rate was higher in bonito than bluefin tuna. It was found that in general, bonito could be reared more easily than bluefin tuna.[著者抄録]1.1970年から1975年まで、和歌山県白浜町および串本町沿岸で採捕したクロマグロおよびハガツオの飼育実験を行った。2.1970年および1971年に採捕したクロマグロは合成繊維網で馴致飼育を行ったが、強い風波によって網地が押し寄せられ、魚体が傷ついて収容後5ヵ月までに全部死亡し、1部は溶存酸素の欠乏で窒息死した。3.1972年から1974年までに採捕したクロマグロおよびハガツオはすべて金網いけすに収容し、飼育を続けたところ、いずれもその1部は生き残って、1975年11月1日現在成長を続け、最も長いものは3年1ヵ月飼育したことになる。4.1972年に採捕したクロマグロは1975年11月1日現在4尾が生存し(生残率95%)、全長140cm内外、体重50kg内外に成長していると推定される。5.1972年に採捕したハガツオは、1975年11月1日現在4尾が生存し(生残率12.1%)、全長60cm内外、体重3kg内外に成長していると推定される。6.1975年11月1日現在、1973年に採捕したクロマグロは全長120cm内外、体重20kg内外に成長して11尾が生存し、1974年に探捕したクロマグロは、体重8kg内外に成長し、約350尾が生存、同年に採捕したハガツオは、体重1.8kg内外に成長し、約30尾が生存していると推定される。7.成長はクロマグロの方がハガツオより著しく速かったが、生残率はハガツオの方が高く、ハガツオの方が餌育しやすい魚種と考えられる。
近畿大学の論文
1976-03-15

クロマグロおよびハガツオの3年飼育*

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