Haematological responses of the African Catfish, Clarias gariepinus (Burchell, 1822) exposed to sub-lethal concentrations of an oilfield wastewater in Nigeria

Abstract

The haematological responses of Clarias gariepinus exposed to sub-lethal concentrations of an oilfield wastewater were investigated. Twenty-eight adult C. gariepinus (mean weight, 205±12.89 g; mean length, 31.13±3.82 cm) were exposed to various concentrations (0. 10, 20, 30, 40, 50 and 60%) of the wastewater for 28 days. Parameters investigated included packed cell volume (PCV), haemoglobin (Hb), white blood cell (WBC), leucocrit, neutrophils, lymphocytes, platelets and erythrocyte sedimentation rate (ESR). Haematological indices of mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were calculated. Haematological parameters did not differ (p≤0.05) but WBC at 0%, had a higher value of 12.23±2.76 x10⁹/l; other concentrations ranged between 3.45±1.9 x10⁹/l, at 30% and 6.58±4.25 x10⁹/l, at 50%. PCV. Hb, WBC and ESR decreased with increasing concentration of the toxicant while platelets increased. Leucocrits, neutrophils and lymphocytes did not differ (p≥0.05) at the different concentrations. Similar observation was made in MCV, MCH and MCHC. These changes which could be used as indicators of stress in fish exposed to elevated levels of oilfield wastewater can lead to death and economic loss. Proper treatment of oilfield wastewater before discharge so as to reduce ecotoxicological problems and public health hazards is advocated.

Keywords: Blood parameters, oilfield wastewater, toxicity, Clarias gariepinus