FATTY ACIDS COMPOSITION IN SOME TISSUES OF COMMERCIALLY SELECTED FRESHWATER AND MARINE FISHES OF THE KENYAN WATERS

Abstract

Fatty acid composition analysis in some tissues of commercially available freshwater and marine fishes in the Kenyan waters was conducted. Four (4) fish species from Lake Naivasha; Largemouth bass or black bass (Micropterus salmoides), Common carp (Cyprinus carpio), Mirror carp (Cyprinus specularis) and Tilapia (Oreochromis leucostictus) and three (3) species from the Indian Ocean; Red snapper (Lutjanus campechanus), White snapper (Macolor niger) and Rabbit fish (Siganus ludridus)] were sampled and analyzed. GC-MS analysis was performed using a GC Voyager-800 series with Trio-01 MS detector in electron ionization (EI) mode to determine qualitatively the fatty acids composition in fish oils. The study revealed that freshwater fish contain essentially omega-6 (ω-6) fatty acids series of the polyunsaturated fatty acids (PUFA) while the marine fishes have more omega- 3 (ω-3) fatty acids series. The linoleic acid (LA, C18:2) was the prominent omega-6 (ω-6) fatty acid while the prominent omega-3 (ω-3) fatty acid was docosahexaenoic acid (DHA, C22:6) series. This may suggest that the dietary essential fatty acids available for marine fishes was the omega-3 polyunsaturated fatty acids which may be absent and hence unavailable for freshwater fishes Thus, the marine fish species are better providers of omega-3 fatty acids such as DHA (C22:6n-3) while the freshwater species are better providers of omega-6 fatty acids such as the linoleic acid (C18:2n-6) as well as the arachidonic acid (C20:4n-6). This study reveals that marine fish species contain appreciable levels of ω-3 polyunsaturated fatty acids and would therefore be suitable for the provision of highly unsaturated low-fat diet containing omega-3 fatty acids while freshwater fishes will provide the ω-6 fatty acids. This study however, may not explain whether the ω-3 fatty acids observed in marine fishes are derived directly from the fish diet or the fish species are good converters of the short chain ω-3 fatty acids like linolenic acid (18:3n-3) into EPA and DHA through enzyme controlled de-saturation followed by chain elongation processes.