ABSTRACT
An acute toxicity (LC50) test using a static renewal bioassay method was conducted to determine the toxicity of sodium cyanide in freshwater exotic carp, Cyprinus carpio exposed for 96 h to different concentrations of sodium cyanide. The acute toxicity value was found to be 1 mg/L; one third of the LC50 (0.33 mg/L) was selected as the sublethal concentration for subacute studies. Behavioral patterns were observed in lethal (1, 2, 3, and 4 d) and sublethal concentrations (1, 5, 10, and 15 d). Cyprinus carpio in toxic media exhibited irregular, erratic, and darting swimming movements, hyperexcitability, loss of equilibrium, and sinking to the bottom, 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, the most sensitive critical sites for anoxia, resulting in respiratory arrest and death. A decrease in oxygen consumption (-28.36 to -78.28%; -14.22 to -47.25%) was observed at both lethal and sublethal concentrations of sodium cyanide respectively. Fish at the sublethal concentration were found under stress, but that was not fatal.
