TOXICITY BIOASSAY OF CHLORPYRIFOS ON SOME LOCAL FISH SPECIES OF NORTHERN BANGLADESH

Abstract

Stinging catfish (Heteropneustes fossilis), Spotted snakehead (Channa punctatus), Climbing perch (Anabas testudineus) and Tangra (Batasio tengana) were exposed to various concentrations of chlorpyrifos (Expert 20 EC) to investigate mortality rate and the toxicity level of the pesticide. The median lethal concentration (LC50) values of chlorpyrifos (Expert 20 EC) on stinging catfish, spotted snakehead, climbing perch and tangra were 23.10, 20.32, 16.61 and 13.94 ppm, respectively for 96 hours of exposure. Mortality rate and behavioral changes of fish at different concentrations were determined. Remarkable behavioral abnormalities were found during the exposure. Fish performs all their body functions in water. The quality of the water in which fish are contained is therefore very important to their livelihood. In the present study, some physicochemical parameters such as temperature, pH, dissolved oxygen, total dissolved solids and electrical conductivity. Studies were undertaken during the month of November, 2017 to April, 2017 during which the physicochemical parameters were analyzed and compared with the aquaculture water quality standard. The temperature values remained within the standard values in the all the aquaculture pond types. pH values of the aquaculture ponds ranged, from 4.7-6.8 as against the standard water quality i.e., 6.5-8.0 and the pH of this experiment with presence of pesticide was 6.64- 7.30. Fish kills occurred in every month of the year but were most abundant in summer from June through September as was the abundance of rainfall and warmer water temperature along with the abundant use of pesticide was a major factor. Pesticides caused a number of fish killing in ponds throughout the year. Conclusives, erratic swimming and lethargy were symptomatic of pesticide toxicity. If an organophosphate insecticide is the cause, the pectoral fins of the fish will be reversed. The pectoral fins of a healthy fish point toward the tails, but the pectoral fins of a fish poisoned by insecticide curl up and point toward the head. Fish ponds should not be built in areas adjacent to crops that are likely to be treated with pesticides toxic to fish.