ABSTRACT: Static renewal bioassay test was conducted to determine the toxicity of technical grade (92.25%
purity) insecticide cypermethrin on the freshwater teleost, Labeo rohita. Fishes were exposed to various
concentrations of pyrithroid insecticide cypermethrin for 96 h and the percent mortality was recorded. The LC50
value was found to be 4.0 μg LG1 and one seventh of LC (0.57 μg LG1) was selected as sub lethal concentration
for sub acute studies. Behavioural patterns were observed in both lethal (1, 2, 3, 4 d) and sub lethal
concentration (1, 5, 10, 15 d). L. rohita in toxic media exhibited erratic and darting movements with imbalanced
swimming activity, which might be due to the malfunctioning of neurotransmitters, followed by hyper and hypo
opercular activity, loss of equilibrium, and mucus secretion all over the body were observed.
World Journal of Zoology. 01/2009; 4:19-23.