Acute toxicity of nitrite on Litopenaeus vannamei (Boone) juveniles at different salinity levels

Litopenaeus vannamei juveniles (total length 56 +/- 9.6 mm) were exposed to different concentrations of nitrite-N (nitrite as nitrogen), using a static renewal method at salinity levels of 15 parts per thousand, 25 parts per thousand and 35 parts per thousand (g/kg) pH 8.02 and 18 degreesC. The 24-, 48-, 72-, 96- and 144-h LC50 value of nitrite-N on L. vannamei juveniles were 187.9, 142.2, 92.5, 76.5, 61.1 mg/l at 15 parts per thousand; 274.1, 244.0, 224.8, 178.3, 152.4 mg/l at 25 parts per thousand; 521.2, 423.9, 375.0, 321.7, 257.2 mg/l at 35 parts per thousand, respectively. As the salinity decreased from 35 parts per thousand to 15 parts per thousand, susceptibility of nitrite-N increased by 277%, 298%, 405% and 421% after 24-, 48-, 72-, 96- and 144-h exposure, respectively. The safe level for rearing L. vannamei juveniles was estimated to be 6.1, 15.2, 25.7 mg/l for nitrite-N in 15 parts per thousand, 25 parts per thousand and 35 parts per thousand, respectively. The relationship between LC50 of nitrite-N (mg/l), salinity (S) and exposure time (7) is as follows: LC50 = 123.0182 + 0.3657S - 0.6072T (R-2 = 0.9847). (C) 2003 Elsevier Science B.V. All rights reserved.