Effect of Stocking Density on Growth and Survival of African Catfish Clarias gariepinus (Burchell, 1822) Cultured in Floating Net-Hapas in an Outdoor Concrete Tank
African catfish (Clarias gariepinus Burchell, 1882) fry were cultured at three different stocking densities in net hapas (submerged volume 0.75 m3) suspended in an outdoor concrete tank of the Aquaculture and Fisheries Department, University of Agriculture, Abeokuta, Nigeria. Catfish fry (mean weight 0.12 ± 0.10 g) were randomly stocked at densities 50, 100 and 150 fish m−3 and fed commercial diet (55% Crude Protein) for twelve weeks using a Randomized Complete Block (RCB) Design. Twenty percent of the stocked fish was sampled for growth performance fortnightly. Physico-chemical parameters (pH, temperature, dissolved oxygen and conductivity) were monitored. At harvest, weights (gross yields) were respectively 471.88 ± 0.30, 446.78 ± 0.31 and 460.06 ± 0.42g m−3. Analysis of the fish carcass for growth response revealed that there were no significant differences (P>0.05) in all growth parameters analyzed among the various stocking densities. Fish stocked at 50 fry per hapa only recorded the best mean final weight (5.02g); best mean daily weight gain (0.058g/d); best specific growth rate (4.44g/day) and best relative growth rate (4083%). Best protein efficiency ratio (0.219) was recorded in fish stocked at 100fish/m3. The ability of fish to convert feed given to flesh increased with increase in stocking density. Survival was generally high. The results showed that the maximum stocking density for culturing catfish in net-hapa of this capacity was not reached.
Key Words: African catfish, Cage culture, Carrying capacity, Growth.