Haematological and Hepatic Responses of the African Catfish Clarias gariepinus to Sublethal Exposure of Industrial Effluents from Ologe Lagoon Environs, Lagos, Nigeria

The present study is on the haematological and hepatic responses of the African catfish fingerlings Clarias gariepinus to sublethal toxicity of industrial effluents (IE) from the environment of Ologe Lagoon, Lagos, Nigeria. The fish were cultured in five concentrations of industrial effluents: 0% (control), 5%, 15%, 25%, and 35%. Trials were carried out in triplicates for twelve (12) weeks. The culture system was a static renewable bioassay and was carried out in the fisheries laboratory of the Lagos State University, Ojo-Lagos. Weekly physico-chemical parameters: Temperature (°C), pH, conductivity (ppm) and dissolved oxygen (DO in mg/L) were measured in each treatment tank. Haematological parameters: packed cell volume (PCV), red blood cells (RBC), white blood cell (WBC), neutrophil and lymphocytes etc., and hepatological alterations were measured after 12 weeks. The physico-chemical parameters showed that the pH ranged from 7.82±0.25~8.07±0.02. DO ranged from 1.92±0.66~4.43±1.24 mg/L. The conductivity values increased with increase in concentration of I.E. While the temperature difference remained insignificant with mean value range between 26.08±2.14~26.38±2.28. The DO showed significant differences at p < 0.05. Though survival was 100% during the sublethal study, haematological results showed that C. gariepinus had PCV ranging from 13.0±1.7~27.7±0.6, RBC ranged from 4.7±0.6~9.1±0.1, and neutrophil ranged from 26.7±4.6~61.0±1.0 amongst others. The highest values of these parameters were obtained in the control and lowest at 35%. While the reverse effects were observed for WBC and lymphocytes, the liver shows normal liver cells in the control (0%), but at higher toxic levels, there were: vacoulation, destruction of the hepatic parenchyma, tissue becoming eosinophilic (i.e. tending towards Carcinogenicity) and severe disruption of the hepatic cord architecture. This study therefore shows that disposal of effluents into the aquatic environment affects the health of fishes by impairing normal hepatic functions and hindering vital physiological processes if exposure continues for a long period of time (sublethal effect).