VALIDATION OF MEDIAN LETHAL CONCENTRATION OF LEAD CHLORIDE IN BANDED GOURAMI, Trichogaster (Colisa) fasciata, BY ACUTE TOXICITY BIOASSAY

Industrial revolution in India has been useful in terms of national economy, but it has one major deleterious effect on the environment, as heavy metals that are toxic and utilized in industries in enormous scale, are alarmingly being discharged into aquatic environment and are found to cause serious adversities to the biotic organisms living in water like fish, molluscs. Lead chloride, an inorganic salt used in industries like batteries, petroleum, dye, chemical, mining in a major scale, is chosen as the toxicant for this study. Trichogaster (Colisa) fasciata (common name banded gourami), a fresh water fish of air-breathing habit having ornamental as well as nutritional values, is chosen as the test organism for this study. Acute toxicity bioassay was done in this study following the guidelines of United States Environment Protection Agency, in which a static test of 96 hours’ duration was performed in 4 replicates, each containing 1 control and 5 different concentrations (100, 125, 150, 175 and 200 mg/lit respectively) of lead chloride. Total number of fish used in the study was 192, distributed in 4 series, with each series having eight fish for each concentration of the salt. During the entire study, the temperature of water was kept at 21℃ to 23℃. Finney’s Probit Analysis was the method used to analyse the observed data statistically by the help of SPSS Software. The median lethal concentration (LC50) value of lead chloride at 96 hours for the chosen fish species was estimated to be 145.3 mg/lit. From this toxicity assay, it can be concluded that increasing concentrations of toxic heavy metals like lead in water can be detrimental and even fatal for aquatic organisms like fish. This study also helps in validating a permissible level of lead in water for the selected fish species.