EFFECT OF BROODSTOCK SIZE ON THE SURVIVAL AND GROWTH OF HYBRID CATFISH (Clarias gariepinus S? and Heterobranchus longifilis 0')

Abstract

Investigation on the effect of broodstock size on fry survival and growth during the primary rearing phase (14 days) of the hybrid of female Clarias gariepinus and male Heterobranchus longifilis in glass aquaria was carried out. The use of small size-range broodstock (:$ 250g) resulted in higher percentages fertilization than broodstocks of medium size-range (300- 650g) and large size-range (700- 950g). The percentage egg hatching and fry survival were not significantly (P > 0.05) influenced by the weight and size of the broodstock, During the secondary rearing phase (56 days duration) growth and survival of the fingerlings of the same group of fish in hapa net cages were studied. Fingerlings from large size-range broodstock had the greatest average daily growth but fingerlings from medium size-range had the best specific growth rate and was significantly different (P < 0.05) from the other treatments. The percentage fingerling survival for the treatments were similar. Cost-benefit analysis of production revealed that it is most profitable to use broodstocks of medium size-range (300- 650g) than smaller or larger broodstocks for optimum fingerlings production.