Afr. J. Environ. Pollut. Health 10: 19-24 *2013* Received November 9, 2012; Revision accepted December 13, 2012 ISSN = 1596-7425 = Haematological profile of Clarias gariepinus in a lacustrine ecosystem in Niger delta region, Nigeria L Etim 1 , JP Udoh 1 *, AO Udoh 1 & A Enebeli 2 1 Department of Fisheries and Aquatic Environmental Management, University of Uyo, Akwa Ibom State, Nigeria. 2 Department of Fisheries, Asaba Campus, Delta State University, Asaba, Delta State, Nigeria. *Corresponding author: jjamesphilip@gmail.com Abstract: We established the haematological profile of Clarias gariepinus from Ona Lake in Delta State, Southeast Nigeria. Sexes were used without discrimination. Mean value and standard deviation were obtained for each parameter and were recorded as follows: Length (39.65 ± 8.94) cm, Weight (409.7 ± 94.79) g, Haematocrit (41.2± 8.94) %, Plasma protein (10.2 ± 2.44) g100ml -1 , Erythrocyte (1.56 ± 0.27) 10 6 mm -3 , Leucocyte (2.53± 3.10) 10 6 mm -3 , Haemoglobin (6.67± 1.98) g 100ml -1 . The derived haematological indices were computed: mean erythrocyte hemoglobin (MEH) (45.10 ± 16.60) g, Mean erythrocyte haemoglobin concentration (MEHC) (17.30± 6.80) % and Mean erythrocyte volume (MEV) (282.04 ± 86.46) µ 3 . Length correlated positively with haematological parameters except Erythrocyte, Leucocyte, plasma protein and Mean erythrocyte haemoglobin concentration (MEHC). Significant relationship (P< 0.05) was established in weight and Plasma protein. Weight correlated negatively with haematological parameters except Haematocrit and Mean erythrocyte volume (MEV). Factors which affect the haematological characteristics of the fish are discussed. Keywords: blood parameters, lentic system, Ona Lake. Introduction Haematological parameters are considered patho-physiological indication of the whole organism, that aid in ascertaining the health status of a fish (Shah and Altindag, 2004). The greatest challenge in the assessment of the health status of fish population has been the paucity of information of what the normal condition should be. In view of this, some fish physiologists have considered haematological studies as a tool for diagnosis and evaluation of the health of fish (Kori-Siakpere et al., 2005). The study is focused on Clarias gariepinus, a species of catfish (order: Siluriformes) of family clariidae. Clarias gariepinus is a highly valued fish species. C. gariepinus live in fresh water lakes, rivers, swamps, brooks as well as man-made ponds. Studies have shown that physiological changes are indicated in one or more haematological parameters of fish (Anderson and Klontz, 1965). Fish blood parameters indicate internal and external environmental conditions in time and space depending on fish size, age and diseases (Gabriel et al, 2004). Previous hematological studies on effects of Zinc (Anunne et al., 1994) and health status (Gabriel et al., 2004) on C. gariepinus blood parameters revealed that erythrocytes are the main blood components which indicate normal or adverse conditions in fish. The aim of this work is to establish and provide reference information on the normal hematological profile of African mudcatfish C. gariepinus living in natural lacustrine environment; to identify the sensitive haematological indicators of both internal and external environmental conditions, and to provide a basis for future comparative survey. This investigation will also provide the tool to monitor the growth, propagation status and effective management of this and other related fish species in inland natural lacustrine environments in Southeast Nigeria and elsewhere. Data collection and analyses Thirty live specimens of C. gariepinus were caught individually from Ona Lake (6 o 41’E, 6 o 15’N) in Oshimili South Local Government Area of Delta State, Nigeria. A tributary of River Ase, Lake Ona lies west of River Niger and has its source from Utto spring. It is 2,250.01m long, 516,197.2m 2 in area with a volume of 4,413,804.12m 3 (Ekelemu and Samuel, 2006). The physico-chemical parameters of River Ase are reported as: water temperature (30.40 ± 0.24 o C), Dissolved Oxygen (6.36 ± 0.44 mg l -1 ), Biological Oxygen Demand (3.60 ± 0.23 mg l -1 ), pH (6.36 ± 0.28), Conductivity (18.95 ± 13 µS cm -1 ), Alkalinity (2.46 ± 0.79 mg l -1 ), Phosphate (0.029 ± 0.002 mg l -1 ) and Nitrate (2.66 ± 0.18 mg l -1 ) (Arimoro et al., 2007).