Abstract
The common carp (Cyprinus carpio) was exposed to diazinon to determine the lethal concentration (LC50) values at different times and effects of sub-lethal concentrations on haematological and biochemical parameters. The LC50 values at varying times were recorded as high as 18.57 mg/l (24 h), 14.87 mg/l (48 h), 12.29 mg/l (72 h) and 9.76 mg/l (96 h). Fishes exposed to sub-lethal concentrations (0.5, 1.0 and 2.0 mg/l) for four weeks revealed that the pesticide causes alterations in various blood parameters. Red blood cell (RBC) counts, haemoglobin concentration and haematocrit values increased whereas white blood cell (WBC) count decreased. Plasma glucose level, glutamate-oxaloacetate transminase (PGOT) and plasma glutamate pyruvate transminase (PGPT) activities increased in the fish exposed to diazinon. Protein level in plasma and glycogen in liver and muscles were found to decrease in treated fish with diazinon.