Justus Kwetegyeka
Department of Chemistry, Makerere University, PO Box 7062 Kampala, Uganda
G Mpango
Department of Chemistry, Makerere University, PO Box 7062 Kampala, Uganda
O Grahl-Nielsen
Department of Chemistry, University of Bergen, Allegt 41, N-5007 Bergen, Norway
Abstract
The fatty acid composition in the heart tissue and muscle tissue of the Nile perch, Lates niloticus, and Nile tilapia, Oreochromis niloticus populations from Lakes Kioga and Victoria was determined by methanolysis and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate principal component analysis. The most abundant individual fatty acids were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n9), vaccenic acid (18:1n7), arachidonic acid (20:4n6) and docosahexaenoic acid (22:6n3). Due to high levels of both n6 and n3 fatty acids, the ratios of n3 to n6 were between 1 and 2, typical for freshwater fish species. Two Lake Victoria and one Lake Kioga populations of Nile tilapia and Nile perch were distinguished by the fatty acid profiles in their heart and muscle tissue. The heart tissue showed better separation than muscle tissue, due to dominance of polar phospholipids. It is rationalised that genetics are more important than diet in determining the fatty acid composition of the tissues.
Keywords: dietary factors; gas chromatography; genetic factors; multivariate statistics; principal component analysis; tissue analysis
African Journal of Aquatic Science 2006, 31(2): 297–304