Assessment of Sodium Cyanide Toxicity on Freshwater Teleosts

Abstract

Short term definitive tests by static renewal bioassay method were conducted to determine the toxicity of sodium cyanide on freshwater teleosts, Catla catla, Labeo rohita, Cirrhinus mrigala, Cyprinus carpio and Oreochromis mossambicus. Fishes were exposed to various concentrations of sodium cyanide for 96 h and the mortalities were recorded. The acute toxicity (LC₅₀) of sodium cyanide calculated over 96 h period for C. catla, L. rohita, C. mrigala C. carpio and O.  mossambicus was found to be 0.11 mg/L, 0.19 mg/L, 0.33 mg/L, 1 mg/L and 0.420 mg/L, respectively. Behavioural patterns were observed in lethal (1, 2, 3 and 4 d) concentration. Some of the common behavioural changes exhibited by teleosts in toxic media include hyperexcitability, erratic and darting movements with imbalanced swimming activity, which might be due to inhibition of cytochrome c oxidase activity and decreased blood pH. The combination of cytotoxic hypoxia with lactate acidosis depresses the central nervous system and myocardium, which are the most sensitive critical sites for anoxia, resulting in respiratory arrest and death.