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.
