       SEDInst© 2011. All rights reserved This work by SEDInst is licensed under a Creative Commons Attribution 3.0 Unported License. 34 http://www.ejournal.sedinst.com © Science Education Development Institute, 2011 Volume 1 (Issue 2) Oct: 34 - 39, 2011 Printed in Nigeria ISSN: 2276 - 6723 PHYSIOLOGICAL RESPONSES IN TILAPIA GUINEENSIS SUBJECTED TO HANDLING STRESS Akinrotimi, O.A; Aranyo, A.A and Ibemere, I.F. African Regional Aquaculture Centre/Nigerian Institute of Oceanography and Marine Research. P.M.B. 5122, Port Harcourt, Rivers State, Nigeria. ABSTRACT Some physiological responses in Tilapia guineensis (mean length 24.64cm ± 5.21SD, mean weight 408.32g ±10.46SD), were assessed. The results obtained indicated alterations in the values of haematological parameters with significant reduction (p < 0.05) the values of red blood cell (RBC), Haemoglobin (Hb), packed cell volume (PCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC) while the value of white blood cell (WBC) and mean corpuscular volume (MCV) increased significantly (p < 0.05). For the plasma electrolytes, sodium (Na + ), Chloride (Cl - ) and Hydrogen carbonate (HC0 3 - ) levels decreased following exposed to stress, while no change in calcium (ca + ) and potassium (K + ) levels was observed in response to stress. Plasma enzymes activities which include alkaline phosphatase (ALP), alanine aminotransferase (AST), Alanine transaminase (ALT) and lactate dehydrogenese (LDH) were significantly (p<0.05) elevated after exposure to stress. The results therefore suggest that handling stress impairs the physiological status of T. guinnennsis. KEYWORDS: haematology enzymes, electrolytes, stress, aquaculture INTRODUCTION Fish are exposed to various degree of stress in culture conditions as a result of various handling procedure employed in aquacultural practice (Akinrotimi et.al., 2009). These practices may cause some biochemical and physiological change, which can lead to metabolic disturbance, enzymatic dysfunction and haematological distortions (Tavares – Dias et al., 2001; Akinrotimi et. al., 2007a). The magnitude of behavioural and physiological response to stress varies among fish species, culture system, and management practices in aquaculture (Schyolden et al., 2005; Akinrotimi, 2008). These responses to stress have been grouped broadly as primary, secondary and in some cases tertiary (Barton, 2002), primary, responses involve neuron-endocrine responses such as catecholamine release and activation of corticotrophin from interenal axis (Sumpter, 1997; Reid et al., 1998). This trigger the sequential secondary response, which involve alterations in haematological parameters (Martins et al., 2004; Akinrotimi et al., 2010a), changes in plasma metabolites and electrolytes (Iwama et al., 1998) and ultimately results in tertiary response which involves whole animal performance such as impaired growth, susceptibility to disease, reduced reproductive activity and ultimately results in mortality (Wedemeyer et al., 1990; Shreck et al., 2001). These stages of stress responses depend majorly on the magnitude and duration of stress and it can affect fish at all levels of organization, from cellular to the entire population (Adams, 1990). Alteration in blood biochemistry, plasma enzyme and haematological indices have been studied extensively in different fish species subjected to stressful conditions in aquaculture (Ellsaesser and Clem. 1986; Barcellos et al., 2004; Gabriel et al, 2007; Akinrotimi et al., 2007b). Clinical evaluation of blood cells, enzymes and electrolytes are useful indices in monitoring the physiological status of fish exposed to stress associated with various handling procedures in intensive fish culture (Akinrotimi et al., 2007c, Nikoo et al., 2010). Tilapia guineensis is an euryhaline fish species endemic to brackish water zone of Niger Delta. It is a popular fish for culture among many fish farmers in the region. Physiological responses of T. guineensis to culture conditions are not well known. Study on the physiological responses of fish species to stressful conditions leads to better understanding of its day to day management practices that will enhance optimum performance in the culture medium. The aim of the present study was to investigate the physiological responses to stress arising from handling procedures involved in the culture of T. guineensis.