Impact of fertilizer (urea) on oxygen consumption and feeding energetics in the fresh water fish Oreochromis mossambicus.

The effects of urea on survival, food utilization and oxygen consumption of the fresh water fish Oreochromis mossambicus were studied. The percentage survival of O. mossambicus when exposed to different concentrations of urea at 24, 48, 72 and 96h exposures was noted and it was found that 22,000 and 38,000mgL(-1) urea concentration were sublethal and lethal, respectively. The median lethal concentration, which killed 50% of the fishes during 96h exposure, was 28,000mgL(-1). Rearing the fish in increasing sublethal concentrations of urea, it was found that the feeding rate decreased from 34.341±7.067mgglivefish(-1)d(-1) (control) to 13.921±2.315mgglivefish(-1)d(-1) at the highest concentration of urea (22,000mgL(-1)). Growth rate was drastically reduced. The consumption of oxygen in O. mossambicus diminished from 0.962±0.208 to 0.645±0.118mgglivefish(-1)h(-1) when reared in the highest sublethal concentration of urea.