マルソウダの人工ふ化と仔魚飼育について

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[Author abstract]Hitherto, no successful study has been reported on the artificial fertilization and rearing of larvae inAuxis tapeinosoma (marusoda in Japanese, frigate mackerel in English). The authors made some trials of artificial fertilization of this fish aboard some professional fishing vessels during spawning season of the fish (May～July). The mature fish were caught on June 16, 24 and 25, 1972 by a trap net near the coast of Oshima Island near Cape Shionomisaki. About 40 thousand ripe eggs were obtained from the fish and fertilized in dry method. The fertilized eggs were buoyant, spherical in shape, measuring 0.97 to 0.99mm in diameter. The fertilized eggs were then transported from Oshima to the Shirahama Fisheries Laboratory of the Kinki University, Wakayama Prefecture, and kept in cylindrical tanks of 0.03 to 30 tons. The eggs hatched out in 38 to 52 hours at the water temperature ranging from 21.4 to 23.5℃. The newly hatched larvae measured 3.3～3.6 mm in total length. The hatched larvae were fed three days after hatching with a kind of rotifer previously cultivated, which was replaced 7 days after hatching by the second food, several kinds of marine zoo-plankton, and these were then replaced about 20 days after hatching by the third food, several kinds of minced fish. Under best conditions, the larvae grew up to 49 mm in total length in 18 days,.and to 157 mm in 52 days after hatching. Stages up to 157 mm in total length are shown in Plates 1 and 2. This demonstrates the very rapid gorwth of young Auxis tapeinosoma.[著者抄録]1. 1972年5月から7月までの間、和歌山県串本町大島樫野定置網から漁獲されるマルソウダから採卵･人工授精を試み、授精卵を得て同県白浜町の本学水産研究所へ輸送し、ふ化・仔魚の飼育実験を行なった。2. .紀伊半島南部の沿岸に 5～6月(水温18～22 ℃)に来遊するマルソウダから熟卵が採取され、人工授精･ふ化が可能なことが明らかとなった。3. 卵は直径00.98mm内外の分離浮性で1個の油球を持ち、水温 22.5～23.3℃では、授精後35時間から44時間までの間でふ化した。4. 仔魚は培養したシオミズツボワムシ･天然海産プランクトン･小魚のミンチなどを摂取して成育し、ふ化当日全長3.49mm内外の仔魚は、小型水槽ではふ化後20日8.5～11.0mm、43日89.0～95.0mmに成長したが、大型水槽ではふ化後18日49.0mm、40日140.0mm、52日144.0～157.0mmに成長した。5. 本実験の結果、マルソウダの採卵･人工ふ化および仔魚から未成魚までの飼育が可能なことが実証され、マグロ頬の人工ふ化･仔魚飼育研究上参考となると思われる知見が得られた。
1973-03-15

マルソウダの人工ふ化と仔魚飼育について

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