Abstract

The acute toxicity of blue tilapia, Oreochromis aureus (3.28 ± 0.36 g in body weight, 61.84 ± 2.08 mm in body length) exposed to environmental un-ionized ammonia at different salinities (1, 8, 12, 16 and 20 ppt) was assessed via a series of static exposure trials. Median lethal concentrations of 24 h of exposure were calculated for each salinity. Tolerance of blue tilapia to acute un-ionized ammonia exposure was not influenced by salinity. Median lethal concentrations (24-h LC₅₀) values were found to be 2.83, 2.26, 3.14, 3.11 and 1.93 mg/l NH₃ at 1, 8, 12, 16 and 20 ppt of salinities, respectively. The results of this study indicate that using brackish water for blue tilapia culture may not be a single factor to reduce the toxicity of high ammonia.

Key words: Oreochromis aureus, blue tilapia, ammonia, salinity.