Two groups of juvenile white shrimp Litopenaeus vannamei with average body weight of 0.33 ± 0.11g and 0.15 ± 0.09g were exposed to different concentrations of ammonia and nitrite to determine the median lethal concentration (LC50) by a static renewal method. The corresponding 24, 48, 72 and 96 h LC50 of ammonia were 3.70, 2.27, 1.83 and 1.65 mg/l for NH3-N (un-ionized ammonia as nitrogen) and 71.51, 43.79, 35.30 and 31.80 mg/l for ammonia-N (un-ionized plus ionized ammonia as nitrogen), in 21? seawater at pH 7.9-8.3 and at 27℃. The 24, 48, 72 and 96 h LC50 of nitrite-N were 164.2, 47.9, 32.5 and 23.9 mg/l, respectively, in 21? seawater at pH 7.9-8.3 and at 27℃. The safe values of NH3-N, ammonia-N and nitrite-N for white shrimp were 0.17, 3.18 and 2.4 mg/l, respectively.
Key words：Ammonia, Nitrite, White shrimp Litopenaeus vannamei, Acute toxicity