Report and Opinion 2015;7(8) http://www.sciencepub.net/report 72 Effect Of Weight And Length On Full Blood Count Of Cat Fish (Clarias Gariapinus) Adamu, N. M. And Solomon, R.J. Department Of Bilogical Sciences, Faculty Of Science, University Of Abuja, Nigeria. Johnsol2004@Yahoo.Com Abstract: This study was to investigate the effect of length and weight on Clarias gariapinus haematological parameters in commercial fish ponds in Gwargwalada Area council, in the F.C.T. 87 blood samples were collected from the 5th of March to the 10 th of April, the samples were group into three bases on their weight and length Group one ranging from10-20cm and 180-278grams, and Group two 21-30cm and 280-503grams, and Group three 31- 50cm and 509-900 grams. Each blood sample were examine for full blood count which consist of WBC, erythrocytes count (RBC), haemoglobin (Hb), hematocrits (PCV), leukocytes (WBC) differential count and blood indices such as MCV, MCH and MCH. All the calculation were evaluated using ANOVA method in the haematological evaluation the following result show no significant differences from the three group (P<0.05) PCV, RBC, WBC, MCHC, MCH, and MCV. While the rest of the result show a significant differences (P<0.05) Hb, Lymp, Neut, Eos, and Mon. from this result it could be concluded that the weight and length of Clarias gariapinus has effect on the following haematology (Hb, lymp, neut, Eos, and Mon). So it can be used to diagnose Anaemia, bone marrow disorder, viral infection and cancer. [Adamu, N. M. And Solomon, R.J. Effect Of Weight And Length On Full Blood Count Of Cat Fish (Clarias Gariapinus). Rep Opinion 2015;7(8):72-87]. (ISSN: 1553-9873). http://www.sciencepub.net/report. 13 Keywords: Effect; Weight; Length; Full Blood Count; Cat Fish; Clarias Gariapinus Introduction. Clarias gariepinus belongs to the family clariidae and is the most common Nigerian fresh water fish prominent in aquaculture practice. They are easily cultured with large economic gains because of their breathing and hardy nature, suitable reproductive strategy, nutritional efficiency and attainment of large size in a short time (Fagbenro et al., 2009). Fish are the cheapest sources of animal protein in Nigeria and constitute about 40% of animal protein intake by average Nigerian (Afolabi et at., 2003; Sadiku and Oladimeji, 2001). However, the average protein intake by an average Nigerian was estimated to be about 63.24 /day, which is below 70g/caput/day FAO minimum recommendation (Falaye and Akinyemi 2005). Fresh water fish constitutes 69.6% of the total fish supply available to Nigeria (FOS, 2000). Rest of this amount is mudfish, Clarias gariapinus burch, family clariidae, of which marketing trends predict an increase in consumer demands, because most of its production comes from artisanal fisheries. Fish production takes into account the quality of feed, which should not exceed the dietary requirements, but feed amounts to over two-thirds of the variable cost of a fish culture in an intensive management system. Haematological studies of fish or other organisms in which both the input and output substance of almost all the metabolic processes and changes can be detected using the blood profile. Blood is a very good medium of assessing the health status of animals. Its analysis is crucial in many fields of ichthyology research and fish farming. Evaluation of the haematological profile usually gives vital information on the response of the body to injury, size, weight, stress (Nussey et al, 2002). Such an evaluation is indispensably important in arriving at diagnosis, making a prognosis and also in the assessment of the efficacy of therapy and toxicity of drugs and chemical substances (Ihedioha et al, 2004). Thorough knowledge of fish blood constituent through the regular monitoring of fish blood is a very useful diagnostic tool in establishing the health status of fish farm stocks. Haematology although not used regularly in fish medicine can provide sustainable diagnostic information once reference values are established. It is based line information of the species. The pace has been set by many researchers (Blaxhall, 2009, Adedeji et al, 2000, Kori-siakpere et al, 2005). The use of haematological techniques is gaining importance for toxicological research, environmental monitoring and assessment of fish health condition (shah et al, 2004). Blood parameters are considered patho-physiological indicators of the whole body and therefore are important in diagnosing the structural and functional status of fish exposed to toxicants (Adhikari et al, 2004, Maheswaran et al, 2008). Haematological analysis will enhance fish cultivation by facilitating early detection of situations of stress and disease that could affect production performance (Rehulka et al, 2004, Tavares-diuas et al, 2005). A number of haematological indices such as haematocrit (HT), haemoglobin (HB), total erythrocyte count (TFC), packed cell volume (PCV), white blood