Effects of agro-chemicals on fishes: With reference to changes in circulating biochemical parameters in Clarias gariepinus induced with Paraquat dichloride

The response of Clarias gariepinus to Paraquat dichloride, a herbicide that is in high demand in the fragile Niger Delta ecological zone was investigated. The herbicide had been detected in most of the water bodies in the region. The fishes were exposed to the range of concentrations observed in the field (0, 2, 4, 6 and 8) µg/L for 28 days, conducted under the Organization for Economic Co-operation and Development (OECD) test guidelines. Signs of stress were monitored and blood samples were taken from the caudal vein located behind the backbone for biochemical study. Biochemical parameters were measured spectrophotometrically. There were moderate changes in cortisol secretion, glucose levels and fluctuation in protein levels. No mortalities occurred during the test. These findings indicate that Paraquat dichloride can be tolerated by the tropical fish. Nevertheless, it should be used with care as incessant usage can increase its concentrations in the environment. The herbicide binds rapidly and tightly to clay materials and can easily leach into water, which could be lethal to aquatic and terrestrial flora and fauna. It can also magnify along the trophic level, which could be detrimental to humans.