Toxicity of Nitrite to Nile Tilapia: Effect of Fish Size and Environmental Chloride

Abstract

Small (4.4 ± 1.50 g; mean ± SD) Nile tilapias Oreochromis niloticus were more tolerant of nitrite than large (90.7 ± 16.43 g) fish. The 96-h median lethal concentration of nitrite-N to small fish was 81 mg/L (95% confidence interval = 35–127 mg/L) compared with 8 mg/L (4–11 mg/L) for large fish. Addition of chloride to test water (as either calcium chloride or sodium chloride) protected both small and large fish from nitrite. Sodium chloride and calcium chloride appeared to be similarly effective in inhibiting nitrite toxicity.