Abstract:

The effect of broodstock age on the reproductive potential of the tilapia Oreochromis spilurus was studied in the brackishwater (3-5 ppt) during the 1987 spawning season (April-September). Spawners of three different year classes (Year Class I, II and V) were stocked in 2-m³ fiberglass tanks; mean weights of females were 33.9, 174.1 and 683.3 g, respectively. The fecundity of the offspring of young females was compared with that of the same females three years later.
Results showed significant differences in fecundity between the three year classes (P > 0.01). Year Class I had a higher fecundity rate (60 seeds [eggs and fry]/kg female/day) than Year Classes II and V (27 and 2 seeds/kg female/day, respectively). The peak spawning period occurred in the first three months of the spawning season (April-June).
The recovery rates of swim-up fry from eggs or from yolk sac fry in Year Class I were not significantly different from the Year Class II. The recovery rate of swim-up fry from sac fry in both year classes was higher than that of swim-up fry from eggs. The recovery rates for Year Class V were not determined due to the low fecundity and poor quality of the seeds.
The offspring of young females had a higher fecundity rate (196 seeds/kg female/day) than that of old females (60 seeds/kg female/day). It is recommended that spawners of Year Class I and possible Year Class II be used to produce seeds for culturing tilapia. Older spawners should be discarded as unproductive.

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Date 1989/06/01

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