Efficacy of Copper Sulphate as a Prophylactic Agent for Fungal Infection on Egg, and its Effect on Hatching and Early Growth of Clarias gariepinus (Burchell 1822)

Abstract

This study was undertaken to determine the efficacy of prophylactic treatment of North African catfish, Clarias gariepinus (Burchell 1822) eggs with copper sulphate (CuSO4) and its effect on hatch rate, survival to first feeding and growth of fry. Copper sulphate concentrations were: 2 mg. L-1, 4 mg. L-1, 6 mg. L-1, 8 mg. L-1 and 10 mg. L-1. The study employed two treatment methods termed “dip treatment” and “continuous treatment”. A homogeneous mass of eggs (2.4 g) from the same fertilized batch treated with either the dip or continuous method were used to determine the hatching success of the eggs. With a mean fertilization rate of 63.2% in all treatments, significant differences in the hatchability between treated eggs and the control was observed. However an increase in concentration did not affect hatch rate significantly for both methods. Eggs subjected to the dip treatment at all concentration had Saprolegnia growth compared to those incubated in the continuous treatment. Survival rates were significantly higher in eggs treated with concentrations above 6 mg. L-1 compared to the control and lower concentrations. The use of the continuous treatment for rearing fry beyond first feeding is recommended at 2 mg. L-1 CuSO4; this concentration exhibited the best growth performance and survival.