RAJIB MAJUMDER, SUCHISMITA CHATTERJEE (SAHA) AND ANILAVA KAVIRAJ
Abstract
Static bioassays were carried out in laboratory to evaluate variation in acute toxicity between technical grade (92% a.i) and commercial formulation (10 % EC) of cypermethrin to two freshwater fish Labeo rohita and Mystus vittatus. Recovery of actual concentrations of cypermethrin in water after 2h of exposure of the nominal concentrations ranged between 86.1% in technical grade (T) to 92.2 % in commercial formulation (F) of cypermethrin. Based on 96h LC50 values of T and F cypermethrin respectively, both L. rohita (3.08 and 2.09 μg/L, 2h actual conc.) and M. vittatus (3.84 and 2.90 μg/L, 2h actual conc.) were found to be susceptible to cypermethrin. Toxicity of T. cypermethrin in water existed up to 48h while toxicity of F cypermethrin existed till 96h. From pairwise comparison of LC50 values between T and F it was concluded that F was more toxic than T. cypermethrin. Moreover, F cypermethrin remained viable in freshwater aquatic ecosystem for longer period.