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AQUACULTURE, vol.241, pp.479-489, 2004 (SCI-Expanded)
Penaeus semisulcatus juveniles (1.6 +/- 0.2 g) were exposed to different concentrations of ammonia-N in a series of acute toxicity tests by the semi-static method at four different water temperatures (14, 18, 22 and 26 degreesC) at pH of 8.2 and 39 ppt salinity. The mortality rate increased with increasing concentrations of ammonia and exposure time. Low temperatures clearly increased tolerance of the shrimps to total ammonia-nitrogen (TAN) and un-ionised ammonia (NH3-N). The 24-, 48-, 72- and 96-h LC50 values of TAN were 92.22, 76.56, 64.07 and 55.84 mg l(-1) at 14 degreesC; 57.00, 46.07, 41.85 and 36.01 mg l(-1) at 18 degreesC; 41.10, 33.42, 30.61 and 26.72 mg l(-1) at 22 degreesC; and 25.89, 15.44, 13.44 and 11.44 mg l(-1) at 26 degreesC, respectively The 24-, 48-, 72- and 96-h LC50 values of NF3-N were 3.18, 2.64, 2.22 and 1.92 mg l(-1) at 14 degreesC; 2.94, 2.37, 2.15 and 1.85 mg l(-1) at 18 degreesC; 2.77, 2.25, 2.06 and 1.80 mg l(-1) at 22 degreesC; and 2.26, 1.35, 1.17 and 1.00 mg l(-1) at 26 degreesC, respectively. The safe level for rearing P semisulcatus was estimated to be 5.6, 3.6, 2.7 and 1.1 mg l(-1) for TAN and 0.19, 0.19, 0.18 and 0.10 mg l(-1) for NH3-N at 14, 18, 22 and 26 degreesC water temperatures, respectively. The safe level was fivefold higher for TAN and twofold higher for NH3-N at 14 degreesC in comparison to 26 degreesC. (C) 2004 Elsevier B.V. All rights reserved.