Ebonyi State University, Nigeria
Title: Dietary zinc (ZnSO4) requirement for the African giant catfish Heterobranchus longifilis (Valenciennes, 1840)
Bilikis Iyabo Uneke holds a Ph.D in Fisheries Biology. She is a leading researcher and lecturer in the Department of Biological Sciences, Ebonyi State University, Nigeria. In the last ten years, her work as focused on aquaculture, stock assessment, modeling, fisheries management and policy. She has worked extensively on the food, feeding habits and nutrient requirements of teleost fishes of the inland waters of southeastern Nigeria
The requirement of African catfish, Heterobranchus longifilis for dietary was determined. Two hundred and seventy fingerlings samples of H. longifilis (mean weight 2.3±0.1g) were stocked in eighteen (18) plastic bowls, each of 25 litres capacity at a density of 15 fish samples per bowl. Zinc sulphate of 0.1%, 0.5%, 1.0%, 1.5%, 2.0% and 0.0% were assigned randomly to the water baths which were designated as D1, D2, D3, D4, D5 and D6 respectively and each with three replicates. The fish samples were fed at 5% body weight per day thrice daily at 8:00hrs, 12:00hrs and 16hrs. Water in experimental bowls was changed weekly. Fish weights were taken fortnightly and feed were adjusted (to maintain it at a constant 5% of the body weight of fish). The result showed that the performance of fish diets with different levels of zinc sulphate was significantly different (P = 0.05) between treatments. Fish fed diet 1.5% of zinc sulphate inclusion level performed significantly better than the ones fed with the other diets. Fish fed with 2.0% zinc sulphate inclusion level showed high Food Conversion Ratio (FCR) indicating that when the optimum dietary requirement of zinc is exceeded, it can adversely affect the feed conversion ability of the fish, resulting in poor weight gain. Hence, zinc should be included in the diet of fish at the required level to avoid adverse effect which could be harmful not only to the organism but to tertiary consumer (Human beings).