Development of techniques for synchronization of natural spawning in Nile tilapia (Oreochromis niloticus)

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• 作者：Longalong ; Felicisima M. ; Eknath ; Ambekar E.
• 刊名：Aquaculture
• 出版年：1995
• 出版时间：December 1, 1995
• 年：1995
• 卷：137
• 期：1-4
• 页码：283-284
• 全文大小：107 K

文摘

Synchronous spawning of a large numbers of broodstock will, to a large extent, solve the confounding problems of initial age and size effects during comparative evaluation of different genetic group of fish. Hypophysation, manipulation of stocking density and exposure to low temperature have been attempted by several investigators with variable results. While induction of synchronous spawning may be possible by some of these techniques, the quality of egg and swimup fry may not always be uniform. In this study, an attempt was made to study synchronization of natural spawning by correlating external morphological attributes of genital papilla of females with their readiness to spawn and to predict the time schedule of spawning based on the morphological changes of genital papilla. A total of 50 pairs of O. niloticus with mean weight of 81 g were used in this study. Breeders were conditioned in 2 m cages in fertilized ponds for 12 days before they were stocked into the spawning hapas. Daily diet consisted of 70 % rice bran and 30 % fish meal. A caliper was used to measure genital papilla characteristics i.e. slit, length and width. Visual evaluation of the genital papilla was made and a score was given to characterize the spawning condition in females. The stages of the papilla were categorized as follows: not ready to spawn, swollen, ready to spawn and had spawned. Stocking of males and females were done in single pairs in (1 m) hapas installed in earthen ponds. Inspection of eggs or sac fry was done every week. Significant differences on papilla measurements were found between groups for papilla condition. This indicates that papilla width, length, and slit varies greatly as the papilla condition changes with advancing maturity. Results showed that predictability of spawning based on the genital papilla condition was effective and useful in determining the onset of spawning in female O. niloticus. Significant correlations were observed between papilla condition and the day of spawning (0.58). The correlation increased to (0.8) with experience of field personnel in proper scoring of papilla condition. The technique described here is being routinely used to produce fry of relatively uniform age and size of fry in a large scale combined-family selection program.