toxicity of potassium permanganate to caspian kutum (rutilus frisii kutum) at two sizes (1 and 3g)

acute toxicity (96h-lc50) of potassium permanganate (pm) was determined for caspian kutum rutilus frisii kutum at two size classes (1 and 3 g). static renewal method was used. fish were exposed to different concentrations of pm and mortality was recorded thereafter, until 96 h. exposed fish showed behavioral stress indicators. 96h-lc50 was calculated to be 3.204 (3.147-3.260) mg/l for small fish and 3.460 (3.393-3.528) mg/l for large fish. safe concentration for small and large fish was calculated to be 0.003-0.320 and 0.003-0.342 mg/l, respectively. no observed effect concentration (noec) and lowest observed effect concentration (loec) were 2.6 and 2.8 mg/l for small and 2.8 and 3.0 mg/l for large fish. results indicated that caspian kutum is susceptible to pm toxicity; although less than many tested species. likewise, toxicity of pm significantly decreases with increase in fish weight. higher tolerance in large fish compared to small fish might be as a result of increased stress resistance and higher quality of these fish.