Food consumption of Sarotherodon mossambicus (Trewaves) exposed to sublethal concentration of diammonium phosphate

Abstract

S. mossambicus was exposed to toxic and sublethal concentrations of the fertilizer diammonium phosphate (0.2 to 1.0 g l−1). Mortality, food utilization and growth were studied. At a concentration of 0.6 g l−1 DAP, 100% mortality was observed within 96 h; no mortality occurred at 0.5 g l−1; LC50 was 0.55 g l−1. Rearing the fish in increasing sublethal concentrations of DAP, it was found that the feeding rate decreased from 25.4 mg g−1 fish−1 d−1 (fish reared in DAP-free water) to 10.1 mg g−1 d−1 at the highest sublethal concentration (0.5 g l−1). Growth rate was drastically reduced. At high sublethal concentrations of DAP, the fish lost reserve energy, in addition to the energy obtained from food intake for survival, as a result of increased swimming activity and opercular beats.