Two groups of giant sea perch Lates calcarifer juveniles with average body weight of 5.23±0.33 g and 5.86±0.17 g were exposed to different concentrations of ammonia and nitrite, respectively, by a static renewal method. The 24、48、72 and 96h LC50 (median lethal concentration) was 1.95、1.59、1.50 and 1.49 mg/l for NH3 - N (un-ionized ammonia as nitrogen) and 36.61、29.81、28.18 and 28.08 mg/l for ammonia-N (un-ionized plus ionized ammonia as nitrogen), respectively, in 32.1-33.0?, pH 7.8 - 8.3 and 24.7 - 26.4℃. The 24、48、72 and 96h LC50 of nitrite - N was 188.0、141.6、87.8 and 62.8 mg/l, respectively, in 32.8 - 33.7?, pH 7.9 - 8.2 and 27.2-28.0℃. The safe value of NH3 - N、ammonia - N and nitrite - N was 0.15、2.81 and 6.3 mg/l, respectively.
Key words: Ammonia, Nitrite, Giant sea perch, Acute toxicity