Acute Toxicity of Mercury and Chromium to Clarias batrachus (Linn)

Pollution of the aquatic ecosystems by heavy metals is a worldwide problem. In the present study, Clarias batrachus was exposed to Mercury and Chromium for 24, 48, 72 and 96 hrs. The median lethal concentration (LC50) of mercury to C. batrachus for 24, 48, 72 and 96 h of exposure were 1.4 ppm, 1.2 ppm, 1.0 ppm and 0.8 ppm respectively. The median lethal concentration (LC50) of chromium to C. batrachus for 24, 48, 72 and 96 h of exposure were 120 ppm, 115 ppm, 110 ppm and 102 ppm respectively. The acute toxicity levels were derived from LC50 concentrations of the heavy metals. Both the heavy metals produced lethality at smaller doses. Physiological responses like rapid opercular movement and frequent gulping of air was observed during the initial stages of exposure after which it became occasional. All these observations can be considered to monitor the quality of aquatic eco system and severity of pollution.