Effect of Concentrations of Glyphosate, Paraquat and Cypermethrin on Mortality of Red Claw Crayfish Cherax quadricarinatus (von Martens, 1868)

Abstract

This research aimed to study the effect of three chemicals namely glyphosate, paraquat, and cypermethrin on acute mortality of red claw crayfish Cherax quadricarinatus (von Martens, 1868) in laboratory at the Faculty of Agriculture, Ubon Ratchathani Rajabhat University to assess the possibility in controlling the invasion of red claw crayfish if they escape into natural waters contaminated with these three chemical substances. The recently hatched red claw crayfish with the average length of 22.5±0.06 cm and the average weight of 0.85±0.03 g were used in the study. They were raised in 5 liter-plastic ponds (10 animals in each pond). Numbers of death were collected every 24, 48, and 72 h at each level of concentration. It was found that the lethal rates of the young red claw crayfish increased at all times studied depending on the increased concentrations of all three chemicals. The 50% lethal concentrations of glyphosate for the young red claw crayfish at 24, 48, and 72 h were 8.518, 7.161, and 6.252 ppm, respectively. While those of paraquat at 24, 48, and 72 h were 0.719, 0.482, and 0.363 ppm, respectively and those of cypermethrin at 24, 48, and 72 h were 0.007, 0.005, and 0.003 ppm, respectively. These results indicated that cypermethrin had the most effect on acute mortality of the young red claw crayfish, followed by paraquat and glyphosate, respectively. Since that maximum allowable concentrations of chemicals in environment are lower than lethal concentrations for the young red claw crayfish obtained in this study. Therefore, it is unlikely that toxicity contaminated in natural waters will control the invasion of red claw crayfish if they escape into such environment.