Genetic improvement of farmed tilapias: estimation of genetic variation and heritability for age and size at first spawning in Nile tilapia (Oreochromis niloticus)
详细信息 查看全文
- 作者：Eknath ; Ambekar E. ; Reyes ; Ruben A. ; Bolivar ; Hernando L. ; De Vera ; Marietta P. ; Danting ; Jodecel C. ; et. al.
- 刊名：Aquaculture
- 出版年：1995
- 出版时间：December 1, 1995
- 年：1995
- 卷：137
- 期：1-4
- 页码：279-280
- 全文大小：119 K
文摘
A total of 7500 individually tagged fingerlings from 123 full-sib families within 50 half-sib families were communally reared for about 160 days in two earthen ponds each measuring 1200 m. The families were produced from a genetically mixed base population, built by combining the best performing genetic groups from eight diverse strains of Nile tilapia and their crosses. Individual body weights and incidence and frequency of spawning by females (condition of genital papillae, mouthbrooding, etc.) were recorded every 2 weeks by draining the ponds completely. Draining of ponds and sampling of all individuals were done on a rotational basis to conserve and reuse the green pondwater. An additional earthen pond was used for storing the green water while sampling. No supplementary feed was given throughout the rearing period. Estimated heritabilities for age and size at first spawning were 0.15 ± 0.02 and 0.20 ± 0.05, respectively. At the first instance of spawning, the early spawning individuals were relatively larger than the late spawners. These results indicate good prospects for including age at first spawning as an additional performance trait in the on-going selection program for growth and survival. However, objective separation of genetic eftects from the effects of environment (density, food, etc.), behaviour (establishment of territories in ponds, ratio of males to females) and physiology of fish on maturation and spawning is essential before embarking on a selection program for early or late maturation. There is a need to develop objective methods for measuring maturation and spawning and such indicators should be repeatable and applicable to diverse tilapia farming systems.