Effect of salinity on growth, survival, and proximate composition of Macrobrachium rosenbergii post larvae as well as zooplankton composition reared in a maize starch based biofloc system

Abstract

Improved sustainable aquaculture can be achieved through biofloc technology (BFT) by reducing feed input and water use. Although BFT is considered a viable culture strategy to various crustaceans, including Macrobrachium rosenbergii, the influence of salinity has not received much attention. The aim of this study was to investigate the effects of increasing salinities of BF0, BF5, BF10, and BF15 PSU on M. rosenbergii post larval (PL) growth performance and proximate composition in a biofloc system as well as water quality, total bacteria and Vibrio spp. and zooplankton abundance/composition. A carbon: nitrogen ratio was maintained at 10 by maize starch additions. Each tank contained 500 prawns (42.5 ± 5.6 mg) in triplicate. Growth was similar (p > 0.05) in BF0, BF10 and BF15, but was significantly lower in BF5. The best FCR was observed in BF15 and BF10. PL survival was significantly (p < 0.05) higher at BF10 and BF15 than in BF5 and BF0. Higher gross return, net return and benefit cost ratio were obtained (P < 0.05) at BF10 and BF15 than in BF0 or BF5. Whole-body crude protein was significantly elevated in BF15 than all others. Nitrate-N, pH, floc volume and VSS were unaffected by salinity (p > 0.05); however, at weeks 3 and 4, ammonia-N was higher in BF0 (p < 0.05). Total bacteria density and Vibrio spp. were significantly (p < 0.05) higher at BF10 and BF15 than in BF5 and BF0. Total zooplankton density was higher (P < 0.05) at BF15. This study demonstrates that a salinity of 15 PSU improved survival, production economics and protein content of M. rosenbergii, which was likely linked with greater zooplankton abundance in the biofloc-based system.