Effect of ammonia-N on growth and feeding of juvenile Macrobrachium rosenbergii (De-Man)

Survival rate, growth and feed intake were determined for late juveniles (4.31 +/- 0.18 g) of river prawn Macrobrachium rosenbergii in freshwater with total ammonia-N (NH3-N+NH4-N) concentrations of 0.015 (control), 0.5, 1.0 and 1.5 mg L-1 for 60 days at pH 7.53 +/- 0.04 and temperature 24.0 +/- 2.5 degrees C. Survival rate was significantly (P < 0.05) lower (54 +/- 4.2-70 +/- 5.4%) for total ammonia concentrations from 0.5 to 1.5 mg L-1 [0.0139-0.0419 mg L-1 of unionized ammonia (NH3)]. Growth (0.026-0.030 g day(-1) range) of the prawns did not differ for the different NH3 levels but were significantly (P < 0.05) lower compared with control (0.056 g day(-1)). Feed intake rates also diminished significantly (P < 0.05) from 77.60 +/- 2.45% at control (0.015 mg L-1 NH3-N) to 48.69 +/- 2.13% at 1.5 mg L-1 NH3-N (0.0419 mg L-1 of unionized NH3).