Abstract

Fish is sensitive to devastating consequences of oil contamination or deliberate discharge of chemicals to waterways. Histological changes in Clarias gariepinus fingerlings before death under exposure to different concentrations of toxicants was carried out. The study examined the effect of paraquat on the phsico-chemical parameters in water, determined the effect of paraquat on histopathology of catfish (Clarias gariepinus) and evaluation of the behavioral responses of fish at different concentration of paraquat. Three hundred and sixty Clarias garinepinus fingerlings of average weight 3.50± 0.01g and length 12 ± 0.000m was exposed to different concentrations of (0.01, 0.03 and 0.05 ml/L) of paraquat with fifteen (15) fishes per tank in two replicates. The treatment was subjected to 96 Hour bioassay test to determine its acute toxicity in a completely randomized design experiment. Changes in water quality and fish mortality in paraquat treatments for a period of six months were monitored daily in addition, behavioural and histological responses were also investigated. There was a significant difference (p<0.05) in values of temperature, electrical conductivity, salinity, pH and Dissolved Oxygen in the treatments with paraquat before and after the experiment. Mortality rate was highest (90%) in fish exposed to 0.05ml/L detergent water at 96hrs exposure. As concentration and time of exposure increased, the fish showed restlessness, rapid opercula movement, erratic swimming, discoloration and loss of reflex before death. Histological effects were hypertrophy, necrosis of hepatocyte, maliganancy, eroded gills, and degeneration of cells, hemorrhage, interstitial cell and secondary lamella of organs (kidney liver and gills).