Toxic effect of lead on the fingerlings of Cirrhinus mrigala (Hamilton, 1822)

Abstract

Pollution of water bodies caused by heavy metals such as lead is a major problem affecting aquatic fauna. The effect of lead on the fingerlings of fishes has not been widely investigated. The present study was undertaken to evaluate the impact of heavy metal lead on the fingerlings of the freshwater fish, Cirrhinus mrigala. Different concentrations of lead nitrate solutions, viz., 1 ppm, 10 ppm, 40 ppm, 100 ppm, 120 ppm, 160 ppm, 200 ppm, 240 ppm, 300 ppm, 400 ppm and 500 ppm were prepared. Ten fingerlings were introduced into each concentration. The mortality rate and the time of survival of fingerlings in the lead nitrate solution during next 96 hours were recorded. The mortality rate increased to a sudden plateau from 100 ppm to 200 ppm (from 10% to 100%) and total mortality was attained at 200 ppm. LC50 for the fingerlings was found to be 160 ppm. There was almost instantaneous mortality – absolute intolerance – of the fingerlings at 500 ppm. Our study results show that the fingerlings of Cirrhinus mrigala can survive the toxic effect of lead nitrate up to 40 ppm, without physiological stress.