EFFECT OF AMMONIA ON GROWTH OF PENAEUS-PENICILLATUS JUVENILES

1. The 42- and 56-day LC50 (median lethal concentration) on Penaeus penicillatus juveniles were 13.02 and 10.15 mg/l for ammonia-N (un-ionized plus ionized ammonia as nitrogen), and 0.78 and 0.61 mg/l for NH3-N (NH3 as nitrogen). 2. Growth in weight and length of the shrimps exposed to 10 and 15 mg/l ammonia-N was significantly lower (P < 0.05) than those exposed to control after 28 days. 3. The 56-day EC50 (concentration that reduced growth by 50% of that of the control) was 12.65 mg/l ammonia-N, 0.76 mg/l NH3-H for weight gain and 16.67 mg/l ammonia-N, 1.00 mg/l NH3-N for length increase. 4. The MATC (maximum acceptable toxicant concentration) was 6 mg/l ammonia-N and 0.36 mg/l NH3-H for rearing P. penicillatus juveniles.