Comparative acute toxicity of three pyrethroids (Deltamethrin, cypermethrin and lambda-cyhalothrin) on guppy fish (Poecilia reticulata peters, 1859)

Abstract

Pesticides are agrochemicals synthesized to manage a specific range of biological agents and have been yielding desirable results. However, they have been associated with harmful effects on non-target organisms. The focus of this study was to determine and compare the acute toxicity of three commonly used Pyrethroids (deltamethrin, cypermethrin and lambda-cyhalothrin) on non-target guppies, Poecilia reticulata, in order to guide the decision making for pest management. Twenty frys of P. reticulata (average weight of 0.28±0.13 g and length of 2.13±0.27 cm) were exposed to acute concentrations of each of the three pesticides over 96 hrs. The bioassay experiments were set up in duplicates of five test concentrations and untreated control. All three examined pesticides exhibited varying degree of toxicity (median lethal concentration (LC50); Cypermethrin - 27.07 µg/L, Lambda-cyhalothrin - 81.83 µg/L and Deltamethrin - 31.51 µg/L). Cypermethrin was 1.16 and 3.02 more toxic to the fishes compared to Deltamethrin and Lambda-cyhalothrin respectively. It is concluded that all three Pyrethroids are dangerous to aquatic life with the potential to disrupt the normal trophic balance. Their usage must be regulated and farms should be remotely sited from rivers.