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Assessing sexual maturity of feminized Japanese eel Anguilla japonica by measuring eye size
Okamura, A.; Oka, H.P.; Horie, N.; Utoh, T.; Yamada, Y.; Mikawa, N.; Tanaka, S.; Tsukamoto, K. (2009). Assessing sexual maturity of feminized Japanese eel Anguilla japonica by measuring eye size. Aquacult. Int. 17(1): 91-99.
In: Aquaculture International. Springer: London. ISSN 0967-6120, more
Peer reviewed article  

Available in  Authors 

    Aquaculture; Brood stocks; Fertilization; Hatching; Sexual maturity; Survival; Anguilla japonica Temminck & Schlegel, 1846 [WoRMS]; Marine
Author keywords
    Estradiol-17 beta; Eye index; GSI; Induced maturation; Fertilization;Hatching; Survival

Authors  Top 
  • Okamura, A.
  • Oka, H.P.
  • Horie, N.
  • Utoh, T.
  • Yamada, Y.
  • Mikawa, N.
  • Tanaka, S.
  • Tsukamoto, K.

    For efficient production of Japanese eel Anguilla japonica eggs, knowledge of the status of the sexual maturity of potential broodstock females is important because this status directly influences the time required to produce mature eggs by successive hormone doses. Here we apply an eye index (relative eye size) to evaluate the gonadal status of feminized A. japonica, which were induced by administration of estradiol-17ß. Examination of gonad somatic and eye indexes of 267 feminized eels, cultivated for 12-56 months, revealed a significant correlation between these two indexes. Artificial maturation of 35 feminized eels showed that the number of hormone injections administered before ovulation was significantly lower as the eye index score increased, indicating availability of this noninvasive method of predicting sexual maturity of feminized eel. There was no correlation between eye index and fertilization rate, hatching rate, or larval survival rate, suggesting that sexual maturity before hormonal treatment does not affect egg quality.

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