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‰, 25‰ and 35‰ (g/kg) pH 8.02 and 18 °C. 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‰; 274,1, 244.0, 224.8, 178.3, 152.4 mg/l at 25‰; 521.2, 423.9, 375.0, 321.7, 257.2 mg/l at 35‰, respectively. As the salinity decreased from 35‰ to 15‰, 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‰, 25‰ and 35‰, respectively. The relationship between LC50 of nitrite-N (mg/l), salinity (S) and exposure time (T) is as follows: LC50=123.0182+0.3657S−0.6072T (R2=0.9847).