Investigation on types and levels of omega- 3 polyunsaturated fatty acids in four fish species from lake Victoria, Tanzania

Fatty acids (FAs) particularly ω-3 and ω-6 Polyunsaturated fatty acids (PUFAs) are among the most important molecules transferred across the plant- animal interface in aquatic food webs. It plays a critical role to human health, fish and ecological aspects, and its primary source is microalgae. The microalgae diversity and richness in the lake are threatened due to the increase of pollution that affects the quality and quantity of ω-3 PUFAs in the food chain. This study aimed to investigate the types and levels of selected ω-3 PUFAs such as Alfa Linolenic Acid (ALA), eicosapentanoic acid (EPA) and docosapentanoic acid (DPA) in four commercial fish species; Lates niloticus, Oreochromis niloticus, Tilapia zillii and Rastrineobola argentea from Mwanza Gulf in Lake Victoria. Gas chromatography mass spectrometer (GC-MS) was used to analyze the composition of FAs together with levels of the selected ω-3 PUFAs. 36 types of FAs with different saturation levels were detected. The dominant FAs were; palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1ω9), docosahexaenoic acid (DHA, C22:6n3), (EPA, C20:5n3), (DPA, C22:5n3), eladic acid (C18:1), arachidonic acid (C23:0) and palmitoleic acid (C16:1). The results further showed that O. niloticus had the highest composition of FAs (34) compared to L. niloticus (27), T. zillii (26) and R. argentea (21).The levels of EPA differed significantly among the four fish species (F = 6.19, P = 0.001). The EPA levels were significantly higher in R. argentea compared to O. niloticus (P = 0.001), T. zillii (P = 0.036) and L. niloticus (P = 0.009). The DPA levels showed no significant difference in the four fish species (P > 0.05). The study concluded that, the four fish species are good for human health but R. argentea is the best for consumption due to its high levels of ω-3 PUFAs mainly EPA.