Effect of Temperature on Fertilization, Hatching and Survival Rates of Heterobranchus bidorsalis Eggs and Hatchlings
S. A. Okunsebor *
Faculty of Agriculture, Shabu-Lafia Campus, Nasarawa State University Keffi, P.M.B. 135, Lafia, Nasarawa State, Nigeria.
P. C. Ofojekwu
Fishery Unit, Zoology Department, University of Jos, Nigeria.
D. G. Kakwi
Federal Ministry of Agriculture and Rural Development, Plateau State, Nigeria.
B. S. Audu
Fishery Unit, Zoology Department, University of Jos, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Temperature fertilization, hatchability, survival rate, fry