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Factors Affecting Acute Toxicity Dose of Lead Nitrate in Certain Indian Air-Breathing Fishes

Pandit DN, Kumari R and Kumari V

The present work was conducted to determine an ideal median lethal concentration of lead nitrate in two air-breathing fishes namely Channa punctatus (Bloch) and Clarias batrachus (Linn.) using following methods and also influence of different factors to get at a logical conclusion. (1) Graphical method: The LC50 value was 12.02 and 165.0 mg/L for Channa punctatus while 350.0 and 380.0 mg/L for Clarias batrachus. (2) Probit Graphical method: The LC50 value was 11.48 and 177.8 mg/L for Channa punctatus while 315.0 and 346.7 mg/L for Clarias batrachus. (3) Regression method of Finney (1971): From this method LC50 value was calculated to be 11.75 and 208.0 mg/L for Channa punctatus while 320.0 and 348.0 mg/L for Clarias batrachus. (4) Behrens and Karber method: By this method, 96 h-LC50 was found 12.75 and 167.5 mg/L for Channa punctatus while 375.0 and 425.0 mg/L for Clarias batrachus. From these values, the average median lethal concentration of 96 h-LC50 value was calculated to be 12.0 mg/L for Channa punctatus (body weight: 50-68 g) and 180.0 mg/L for Channa punctatus (body weight: 55-75 g). Similarly, 340.0 mg/L for Clarias batrachus (body weight: 85-110 g) and 375 mg/L for Clarias batrachus (body weight: 125-150 g). In this paper, factors such as intra-specific variation, physico-chemical features, spatial variation and methodological variation affecting the values of LC50 has also been studied.