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Abstract
In this study a total number of 660 fishes (330 were Oreochromis niloticus and 330 were Clarias gariepinus) were obtained from Abbasa fish hatchery were used to investigate the toxicological effect of heavy metal and herbicide.
1. Toxicity of Zinc sulphate on Oreochromis niloticus:
The 96hrs LC 50 of Zinc sulphate in Oreochromis niloticus fingerlings was 545.6 mg/L. The fish at acute toxicity showed hyper excitability and fighting against each other and skin surface carry excessive amounts of mucus, while at chronic toxicity showed signs of sluggish, lazy to move and have dark color skin. Grossly fish at both acute and chronic toxicity have anemic and friable gills. Pathologically, gill arch was vacuolated with increased mucous cells and skin showed separation or sloughing of the superficial layers of the epidermis. The remaining cells revealed hyperplasia of alarm substance-cells. The mucous cells, at the lower zone of epidermis, appeared hypertrophied with basophilic mucus on the outer surface.
Concerning to hematological parameters there were found decrease in Hb, RBCs and PCV % while increase in ALT,AST, Urea, Creatinine and Cortisol.
Oreochromis niloticus exposed to 1/3 96hrs LC 50 of zinc sulphate showed difference in behavior, histopathological and hematological parameters in fish during exposure and after recovery .
The residues of zinc in muscle and gills of Oreochromis niloticus were time and concentrations dependant.