著者

藤田 矢郎 与賀田 稔久

出版者

The Ichthyological Society of Japan

雑誌

魚類学雑誌 (ISSN:18847374)

巻号頁・発行日

vol.30, no.4, pp.426-434, 1984

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The present paper deals with ovarian maturation by hormone injection and morphological development of the amberjack, <I>Seriola aureovittata</I> Temminck et Schlegel.Ovarian maturation of the amberjack during the spawning season was successfully induced by injection of either "Gonatropin7" (Teikoku Zoki Mfg.Co.Ltd.), or <I>Hypophthalmichthys molitix's</I> pituitary homogenate, or H.molitrix's pituitary homogenate combined with "Gonatropin".The last dosage was evaluated to be the most effective and reliable.The spawning period seemed to ex-tend from late April to the mid-May in the Sea of the Goto Islands.On May 14, 1977 the authors performed artificial fertilization of the specimens which were artificially induced to mature by the hormone injection, and reared the hatched larvae to grow to the juvenile stage.The eggs of the amberjack are pelagic, spherical in shape and 1.27-1.50mm in diameter.The yolk is roughly segmented and contains a single colorless oil globule of 0.34-0.36mm in diameter.The perivitelline space is narrow.During embryonic development, many melanophores and xantho-phores appear on the embryo and oil globule.Hatching took place in 96 hours after artificial fertilization at water temperatures between 15.5 and 20.4°C.The newly hatched larvae were 4.45-4.55mm TL and had 26 (12+14) myomeres.Characteristic features at the larvae were that the oil globule was situated at the anterior part of the segmented yolk which was extended slightly beyond the head and that the granules existed on the marginal fin which was densely pigmented with xanthophores.The yolk was almost all absorbed when the larvae attained 5.23-5.45mm TL, 4 days after hatching.In a 9-day old postlarva, 6.25mm TL, small denticles appeared on the margin of the upper jaw and there were 4 opercular spines on the preoperculum.In a postlarva 19-days after hatching, 7.5mm TL, the notochord was turned up and caudal, dorsal and anal fins with rudiments of rays were beginning to develop.In a 30-day old juvenile, 15mm TL, the coloration of the body was pale greyish black with the characteristic 2 yellow bands situated at the anterior part of the trunk and the caudal region.In a juvenile of 40-days, 23mm TL, 3 4 greenish dark brown cross bands appeared on the posterior part of the side of the body.The number of the bands increased to 7 at a size of 45mm TL, but such bands had disappeared in a specimen of 195mm TL.