Abstract

The present study was designed to evaluate the acute toxicity of glyphosate on the juvenile of Clarias gariepinus. The acute toxicity bioassay was conducted to determine the 96h LC50 values following the probit analysis method while the safe level of the test pesticide was estimated by multiplying the 96 h LC50 with different application factors (AF). The 24, 48, 72 and 96h LC50 values (with 95% confidence limits) estimated by probit analysis were 34.72(31.02-37.20), 31.90 (28.12-33.89), 27.40 (24.98-29.30), 24.60 (21.95-26.54) mgL-1 respectively. There were significant differences (p<0.05) in the LC50 values obtained at different exposure time. The safe level for the herbicide varied from 2.46 × 10-1 to 2.46 × 10-4 mgL-1. Exposed fish showed uncoordinated behavior such as erratic and jerky swimming, jumping out of water, gulping of air, loss of equilibrium status, hyperactivity, decreased opercula movement and subsequently death. Mortality increased with increase in concentration of glyphosate and time of exposure. The study indicated that glyphosate has toxic effects on the Clarias gariepinus. The herbicide should be prudently used in both terrestrial and aquatic eco systems to avoid ecotoxicological hazards.

Keywords: Clarias gariepinus; Glyphosate; Toxicity; LC50; Behavioural changes; Safe level