Growth performance and robustness of African Catfish Clarias gariepinus (Burchell) in biofloc-based nursery production with different stocking densities

The aim of this research is to evaluate the effects of biofloc system application at different fish density on the nursery production performance and the robustness of African catfish Clarias gariepinus (Burchell) against Aeromonas hydrophila and salinity stress. An economic analysis was also performed to determine the most optimum fish density in biofloc-based African catfish nursery production. African catfish with an average body weight of 0.96 +/- 0.04g and average body length of 4.20 +/- 0.46cm, respectively, were distributed in 12 units of circular plastic-lined tanks (1,020L). The experiment consisted of four treatments in triplicates, that is, a control without carbon source addition at a density of 4fish/L, and three biofloc treatments at different densities, that is, BFT4 (4fish/L), BFT6 (6fish/L) and BFT8 (8fish/L). Tapioca flour was used as the organic carbon source in biofloc systems and was added at an estimated C/N ratio of 10. Housing the fish in biofloc systems resulted in higher fish growth, more efficient feed utilization, higher fish robustness against A.hydrophila infection and salinity stress, as well as higher profitability of nursery production. Increasing the fish density resulted in higher mortality. However, higher number of fish produced and lower feed conversion ratio were observed in the treatments with higher density (6 and 8fish/L). In conclusion, the application of biofloc technology at a density of 8fish/L could be recommended to increase the production and profitability of African catfish nursery culture.