Bioassay of Lindane (Gamalin 20) to Hetrobrancus bidorsalis Juveniles

摘要

The study was carried out to determine the acute toxicity of lindane (Gammalin 20) to Hetrobranchus bidorsalis juveniles using static bioassays. The mean weight and total length of the fish samples were 2.5 g and 8.6 cm respectively. Six groups of the experimental units were set up containing 10 fish individuals in each bowl with 20 litres water capacity. The Gammalin 20, organo chlorine pesticide was distillated and the active ingredient lindane was condensed and collected and the stock solution was prepared. Graded concentration of 0.02, 0.04, 0.06, 0.08 and 0.10 ml/L were prepared and the fish of 10 individuals in each of the bowls were exposed to the different concentration with a control experiment where the toxicant was not introduced. The experimental set was replicated three times. The exposed fish were observed daily and death ones were removed immediately and mortality was recorded for 24 and 48 hours exposure period. The LC50 was determined to be 0.06 ml/L for the 24 and 48 hours exposure period. The obtained result was transformed to probit analysis which was plotted against the graded concentration of lindane for the 24 and 48 hours exposure period. The R2 values of 0.76 and 0.80 were obtained for the 24 and 48 hours respectively indicating a strong relationship of lindane with mortality. The result of the water quality varied from pH: 7, 80-8.46, temperature: 28.39-28.42°C DO: 5.06-5.17 mg/L, Conductivity: 462.00-482.00 μS/cm and TDS: 231.00-241.00 mg/L. Although the water quality parameters increase with increase in the lindane concentration yet it was within the maximum permissible level and did not have any effect on the fish and the death of the fish was due to the toxic potential of lindane. It was recommended that Gammalin 20 is very toxic and persistent in the aquatic environment and it use should be greatly discouraged.