Pesticide residues contamination analysis in water samples of Sreenagar upazila in Munshiganj district and malathion effects on the mortality rate of tilapia, Oreochromis mossambicus (Peters, 1852)

Abstract

Different types of pesticides are widely used in Bangladesh. Pesticide residues pose harmful effect to the target and non-target organisms like fish and many other aquatic and terrestrial organisms including human either directly or indirectly through the food chain. The present study was undertaken to determine contamination analysisof some selected organochlorine (DDT, DDE and DDD), organophosphorus (malathion, diazinon and chloropyrifos) and carbamate (carbaryl) pesticide residues in water samples of different sources from Sreenagar upazila in Munshiganjdistrict using High Performance Liquid Chromatography (HPLC) equipped with Ultra Violate (UV) detector.Thirty onewater samples were collected from fish pond and lake to analyze the suspected pesticide residues. None of the tested water samples was found to be contaminated with malathion, diazinon, chlorpyriphos, carbaryl or DDT and its metabolites (DDE and DDD). Malathion is an organophosphate pesticide used in agriculture and houses to control the variety of insects, which may exert adverse effect on untargeted organisms, such as fish and other aquatic animals. The Mozambique tilapia (Oreochromis mossambicus) is very much sensitive to malathion. Lethal concentration of malathion in tilapia (Oreochromis mossambicus) and the LC50 value was calculated in exposure of (24, 48, 72, and 96) h malathion. The test was performed by following semistic (renewal) bioassay method in which the exposure medium was exchanged after every 24 h to maintain toxicant strength and level of dissolved oxygen, as well as minimizing the ammonia excretion levels during this experiment. Based on the experiment, Malathion seems to be highly toxic to tilapia (Oreochromis mossambicus). The 24 h, 48 h, 72 h and 96 h LC50 value is 3.236 ppm, 2.362ppm, 1.256 ppm and 0.690 ppm respectively. The results showed that LC50 values is decreased with increase in exposure duration, in other words in longer periods of exposure, lower concentrations of pesticide is caused 50% mortality in studied fish population and their mortality rate is dose dependent.