Comparative Study of Hematological and Histopathological Alterations in Oreochromis niloticus and Clarias gariepinus Exposed to Industrial Waste Effluents

In recent decades the level of foreign compounds in aquatic ecosystems such as heavy metals, pesticides and other persistent organic pollutants has increased alarmingly as a result of domestic, industrial and agricultural effluent. This research therefore examined the histopathological and haematological effects of industrial effluent on Orechromis niloticus and Clarias gariepinus. The histopathology and haematology parameters of the fishes exposed to graded doses of the effluent were assessed using conventional techniques. The results of the haematological assessment of the fishes shows a steady and significant (P < 0.05) reduction in the PCV of the tilapia from 23% (control) to 10%  and 25% (control) to 18% in catfish exposed to 6.25 ml/L of the effluent, the RBC count reduced with increase in the concentration of the effluent from 2.60 x 106/L (control) to 1.15 x 106/L (tilapia) and from 2.80 to 1.72 x 106/L (catfish) in the sample exposed to 6.25 ml/L of the effluent. Also, the values of Hb concentration reduced from 7.73 g/dL to 3.10 g/dL (tilapia) and from 8.33 to 5.17 g/dL (catfish). However, the WBC count increased from 4800.33 x 103/L to 9500.30 x 103/L (tilapia) and from 5300.30 x 103/L to 7800.50 x 103/L (catfish) in those exposed to 6.25 ml/L of the effluent. In the histological assessment of the gills of the fishes, the tilapia fish exposed to 6.25ml/L of the effluent recorded an extensive damage, distortion and thickening of the tilapia fish gill lamellae. Also, there was loss of secondary lamellae and loss of gill raker filaments of the catfish. The liver cells of tilapia had many monocytes (kuppfer cells) while there were mild increase in the number of kuppfer cells of the catfish. The kidney artery of tilapia was filled with leucocytes while there were cellular proliferation (hyperplasia) and less of melanin deposits in the kiney cells of catfish. These are indications that the industrial effluent contain toxicants that are dangerous to the fish health.