• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1402-1411
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• 2014

This study about morphological observation of pre- or post ovulated eggs obtained from artificially maturated female eels. Female eels were divided with two groups as wild eels from nature and feminized eels from farm. Artificial maturation had been conducted with the established methods in this laboratory, and then maturate eggs sampled at fixed 3 times and these were observed with stereomicroscope. Rate of increased body weight (RIW) were measured with 2 times. Egg diameters and development of oil droplets are determined for standardization of egg maturation degree, and the transparency of egg cytoplasm and the homogeneous degrees of egg size were referred to determine of egg quality. Rate of increased body weight (RIW) were good in range about 10 % at final salmon pituitary extracts (SPE) injection time and in range about 20 % at $17{\alpha}$, $20{\beta}$-dihydroxy-4-pregnen-3-one (DHP) injection time. Good matured egg for fertilization had $900-1000{\mu}m$ diameter, and they had about 50 oil droplets in size about $100{\mu}m$ diameter. There were not predominant differences at egg size and oil droplet development between wild female and feminized eels.

• Journal of Aquaculture
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• v.20 no.4
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• pp.219-225
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• 2007

This study investigated the correlationship between artificial maturation season and reproduction coefficient of cultured eel Anguilla japonica from May (spring) to next January (winter). The brood stock, female eels ($400{\sim}600\;g$) were artificially matured by weekly intramuscular injections of salmon pituitary extracts (SPE, 20 mg/fish) to induce a completion of vitellogenesis. After completion of vitellogenesis, final oocyte maturation and ovulation was induced by injection of $17{\alpha}$, $20{\beta}-dihydroxyprogesterone$ (DHP) at about $2\;{\mu}g/g$ body weight. Most fish ovulated $15{\sim}18\;h$ following the DHP injection. The ovulated fish were induced to natural spawning or artificial fertilization by the dry method. Males ($200{\sim}350\;g$) were received weekly intramuscular injections of human chorionic gonadotropin (HCG) at a dosage of 1 IU/g body weight to induce testicular maturation and spermiation. Seasonal reproduction coefficient which includes the rate of ovulation, buoyancy, fertilization and hatching of eggs in the artificially matured eel during spring to summer ($May{\sim}July$) were significantly higher than the other season, while there were no significant difference among spring and summer (P<0.05). Furthermore, the number of eggs spawned and larvae hatched in the artificially maturated eel during spring to summer ($May{\sim}July$) were significantly higher than the other season, while there were no significant difference in spring and summer (P<0.05). These results indicate that artificial maturation by hormone treatment of A. japonica was successful only during spring to summer, which is the maturation period in the wild stock in nature. Consequently, it is possible to determine the period of artificially induced sexual maturity by the reproduction coefficient which includes the rate of ovulation, buoyancy, fertilization and hatching of eggs in the cultured eel A. japonica.