Impact of Stocking Density on the Polyculture of C/arias gariepinus and Oreochromis niloticus

Knowledge on stocking density enables the farmer decide on the density limits that will enhance fish yield when intuition and experience are used as guide. Twelve weeks experiment conducted in concrete tanks assessed the growth performance and survival rate at different stocking densities of test specimens. Data analysis revealed that the highest stocking density produced the highest (157.85 ± 36.54 a ) mean weight gain for C. gariepinus. Mean weight gain for O. niloticus in the same tank as just mentioned, took the reverse order. Specific growth data recorded for C. gariepinus revealed an intermediate value at the highest (4.25 ± 1.3 ab ) and lowest (4.23 ± 1.2 ab ) stocking densities, while the highest value was recorded at the intermediate stocking density (4.41 ± 1.34 a ). Data on performance index revealed significant differences between the lowest (339.24 ± 86.95 b ) and intermediate (397.07 ± 103.81 a ) and also between the lowest (339.24 ± 86.95 b ) and the highest (397.81 ± 113.14 a ) stocking densities. The lowest stocking density recorded the highest food conversion efficiency, while the least was recorded at the highest stocking density. Clarias gariepinus recorded 98.3% survival at the highest stocking density, whereas O. niloticus in the same tank recorded 70.83%. The authors therefore conclude that since the highest stocking density gave the best yield in most of the output parameters, it should be recommended to farmers.