Effects of Glyphosate Herbicide on Physiological Parameters of Koi Carp, Cyprinus Carpio (Linnaeus, 1758) Fingerlings

Background: Sub-lethal toxicity bioassay experiments were conducted to determine the toxicity of glyphosate herbicide on Koi carp, Cyprinus carpio fingerlings. Koi carp fingerlings with mean length 8.06 +/- 0.99 cm were obtained from a freshwater fish seed hatchery of the university. Methods: The fishes were exposed to sub-lethal concentrations i.e. 1/10th (3.6 mgL(-1)) and 1/5th (6.6 mgL(-1)) of glyphosate. Oxygen consumption rate, Ammonia-Nitrogen excretion rate, Oxygen:Nitrogen ratio and food consumption rate were recorded after every 7 days for a period of 28 days. Result: Results indicated significant decrease (P<0.05) in oxygen consumption in 1/10th and 1/5th of LC50 concentrations. Ammonia-Nitrogen significcantly increased in exposed fishes. Oxygen : Nitrogen ratio and food consumption rate also significantly decreased (P>0.05) in treated fishes. The results indicated that glyphosate had impacts on exposed fish, hence, the need of regulation of its usage to protect non-targeted species and the environment.