Toxicity of Dizensate (Glyphosate herbicide) on Clarias gariepinus fingerlings

Abstract

Run-off containing a number of chemical solutions, which include herbicides, effluents, find their ways into the water bodies with a resultant negative effects on the aquatic ecosystem. This study sought to establish the effects of herbicide widely used in eradicating aquatic weed; Dizensate glyphosate (N- phosphonomethyl glycine) on Fingerlings of African catfish (Clarias gariepinus). The four day static bioassay was used to determine the median lethal concentration (LC50) and the value was 18.07 mg/l. Mean mortality was 0, 17, 58, 75 and 92% in the concentration of 9.6, 14.4, 19.2, 21.6 and 24.0 mg/l respectively, while there was no mortality in the control treatment. There were significant differences (P<0.05) on the effect of concentration. Fish responses to the toxicant include erratic movement, air gulping, loss of reflex, molting, barbell deformation and excessive mucus secretion. Mortality increased with increase in concentration of Dizensate glyphosate on catfish fingerlings and time of exposure. The physicochemical parameters also showed a slight increase as the concentration increased. It could be concluded that Dizensate glyphosate; an aquatic herbicide, has harmful effects on the physiology, biochemistry and histological structure of fish which in turn affects the growth rate.