Delayed fertilization and short-term storage methods affects the viability of stripped eggs of African catfish Clarias gariepinus

Abstract

The fertilization of eggs may be delayed during induced fish breeding due to unforeseen circumstances. It is, therefore, necessary to know the optimal delay period and explore short-term storage options that can extend the viability of the eggs in such instances. In two studies, African catfish Clarias gariepinus eggs were obtained from broodstocks induced using ovaprim® hormone at 0.5ml/kg. A batch of the stripped eggs was then exposed in triplicate to atmospheric oxygen for 0, 1, 2, 3, 4, 8 and 12 hours post-stripping (HPS). In contrast, another batch was stored for 8 hours using sole and combined methods of “refrigeration”, “addition of extender” and “aeration”. The eggs were then fertilized using fresh sperm in all instances. In both experiments, egg characteristics, breeding parameters, and biometric parameters of hatched fry were recorded. Results showed a size reduction in the eggs as the time of exposure to atmospheric oxygen increased. Also, the fertilization and hatchability of eggs were similar to 4HPS; beyond this threshold, the value declined significantly to zero. However, the hatched fry’s biometric parameters showed no significant difference among treatments (P<0.05). The second study showed a poor breeding performance of eggs stored in all the different storage methods tested. Meanwhile, egg sizes and biometric parameters of the few hatched fry show no significant difference among the treatments (P<0.05). It was therefore concluded that the fertilization of stripped C. gariepinus eggs should not be later than 4HPS to optimize the breeding performance of the fish.