This study evaluated the fatty acid composition and the nutritional profile of Brycon cephalus and Brycon microlepis, fish species from the central Amazon basin, by different methods of quantification. The methods applied were: area normalization (MAN), internal standard (MIS), alternative theoretical (MAT) and alternative experimental (MAE). Significant differences were observed between the methods applied and the species studied. MAN supplied poor information about fatty acids composition and diet formulation, presenting only fatty acid profiles. MIS, MAT and MAE supplied fatty acids composition information on a mass basis. MAT and MAE overestimated results, whereas MIS presented the most accurate results. B. cephalus and B. microlepis showed high contents of approximately 65 mg g-1 of n-3 fatty acids. Eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) content totaled, 104.37 mg 100 g-1 and 117.89 mg 100 g-1 for B. cephalus and B. microlepis, respectively. The nutritional profile of both fish species showed favorable indices for nutritional quality of the lipid fraction, indicating that both Brycon species are healthy dietary choices.

Fish from the Amazon Basin are affected by oscillations in the river water volume, which influences the diet of animal species. This study was aimed at evaluating seasonal variations in lipid content, fatty acid composition and nutritional profiles of five fish species from the Amazon Basin. The lipid contents of all fish species were observed to be lower in flood periods than in drought periods; Brachyplatystoma flavicans showed the largest variation (6.75–15.43 %) between these periods, while Colossoma macropomum showed no significant difference (p > 0.05). The fatty acid composition in the five fish species varied throughout seasonal periods; saturated fatty acid (SFA) contents decreased in flood periods, whereas polyunsaturated fatty acid (PUFA) contents significantly (p < 0.05) increased for all the species in the same period. Leporinus friderici showed the highest content of α‐linolenic acid, (LNA 14.86 mg g−1) and Colossoma macropomum presented the highest content of docosahexaenoic acid (DHA 26.13 mg g−1) in flood periods. Prochilodus nigricans showed the lowest content of arachidonic acid (AA) in both periods, while Brachyplatystoma flavicans showed the greatest amount of AA, 18.77 mg g−1 in drought period and 22.10 mg g−1 in flood period. All the fish species presented favorable indices of nutritional quality of lipid fraction, suggesting that consumption of these species could be considered beneficial to human health.

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Gamma‐linolenic acid (GLA) plays an important role in the prevention and/or treatment of certain diseases. In this work, we investigate the incorporation of GLA from supplemented feed diets with borage oil (BO) and evening primrose oil (EPO) as substitutes for soybean oil (SO) into the composition of tilapia fillet lipids. High contents of PUFA and n‐6 fatty acids were quantified in fish fillet after 30 days of treatment with SO, BO, and EPO. Feed diets containing BO and EPO were efficient in the incorporation of GLA into fish. Compared to the initial day of the experiment, the increase of GLA was significant (from 6.43 to 13.99 and 15.12 mg g−1, in lipids of fish treated for 30 days with BO and EPO, respectively). The increase of GLA was also observed in fish which were fed with SO diet (6.43–11.43 mg g−1). Principal component analysis (PCA) allowed the separation of the treatments and discriminated BO and EPO in a group of fish that received the GLA supplemented diet. In addition to GLA, n‐3 fatty acids were important in the characterization of SO diet and affected the separation of BO and EPO from SO in the PCA score plot.