Efficacy of formalin in the removal of adhesiveness from Clarias gariepinus eggs during artificial propagation
2009
Adebayo, O.T. | Olayinka, S.O.
The aim of this study was to establish the efficacy of formalin in removing the adhesiveness of Clarias gariepinus eggs during artificial propagation and the effects on prospective fry. 1g of catfish eggs were put in five concentrations of formalin \{O.O (control), 0.4, 0.6, 0.8 and 1.0 mg/l\} at three exposure times (10, 15 or 20min). In each treatment, the detachment of eggs increases with exposure time but were not significantly different (P>O.05). 0.4mg/1 of formalin had the highest number of detached eggs. At the highest formalin concentration 72% of the eggs still adhered together which provide a good substrate for the growth of fungi. The use of formalin delayed hatching of C. gariepinus eggs when compared with the control. The more the exposure period of C. gariepinus eggs to formalin, the higher the hatching time. Survival of fry was highest in the group that has been exposed to 0.4mg/1 and exposure period of l0min. At the highest concentration (1.0mg/l) and exposure period (20min), the survival was lower by 55.5%. Based on this study, the optimum concentration of formalin was O.4mg/l and exposure period of l0min. for the removal of egg adhesiveness, increase hatching and improved survival success of C. gariepinus.
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