Effect of Temperature on Fertilization, Hatching andSurvival Rates of Heterobranchus bidorsalis Eggsand Hatchlings

摘要

Aims: To determine the effect of temperature on fertilization, hatching and survival rates of Heterobranchus bidorsalis egg and fry in Jos Plateau, Nigeria.Materials and Methods: This experiment was investigated under controlled temperature hatchery. Stripping was done 9 hours after hormonal injection at 28oC while the male fish was sacrificed and milt prepared for fertilization of the eggs using normal saline. The water temperature was controlled with an adjustable electric thermostat heater empowered by a generator while other water quality parameters were kept constant in acceptable ranges. The eggs were mixed with the milt using chicken feather and 500 of the eggs were spread on kaka ban in aquaria in 4 treatments (26oC, 28oC, 30oC and 32oC) in three replicates. The unfertilized eggs were counted after 6 hours from the time of mixing of the eggs with the milt. The kakabans were removed immediately after hatching and hatchlings were counted then and after 3 days. Results: Fertilization and hatchability of the eggs were significantly highest (p < 0.05) at 28oC and 30oC compared to 26oC and 32oC. Survival rate of newly hatched larvae was significantly highest at 28oC. The lowest survival rate was registered at 32oC while that of 26oC was just within the range of 40%.Conclusion: Fertilization and hatchability of H. bidorsalis eggs are best achieved at temperature range of 28 - 30oC while highest survival rate of the fry was attained at 28oC.