Endogenous and environmental factors can influence the lipid contents of fishes among which, in the Amazon River, seasonal dynamics influences stand out. Herein, nine most consumed Amazonian fish species had their lipid composition evaluated in terms of effects of tissue, season and eating habits. Higher amounts of lipids were obtained from fish livers than dorsal muscles. Statistical analysis has shown that Amazonian fishes presented different lipid profiles according to their eating habits, which mainly comprised saturated fatty acids to distinguish detritivorous livers, and linolenic acid, cholesterol, polar lipids for carnivorous and piscivorous fish muscles. Furthermore, in Amazonian fish, some very important lipids for human nutrition were found, such as w-3 and w-6 fatty acids whose availability depended on the tissue metabolism and fishes’ eating habit along with the seasonal periods. For example, our findings indicated that the piscivorous fish C. monoculus presented higher levels of linoleic acid for livers than linolenic acid and the opposite occurred for muscles. The w-6 and w-3 fatty acids ratio was influenced by the season dynamic of the Amazon River and availability of food according to each specific eating habit, pointing mainly to the piscivorous fishes as the healthiest fish for human consumption.

This article reports on an easy-to-follow methodology for fish lipids analysis, including the biological sample collection, lipid extraction, sample preparation, nuclear magnetic resonance (NMR) spectroscopy analysis and statistical data analysis, with details on parameters used for the NMR analysis and the care needed in each step execution. As an example of the biological matrix of lipids, for the entire procedure, we have used two Amazonian fish samples. Phenotype factor was taken into account when lipid contents of the Amazonian fish samples were evaluated, such as fish-eating habits in distinct Amazon seasonal periods, the flood and the drought. Results demonstrated the applicability of NMR as a powerful and useful tool for fish oil analysis. The omnivorous (T. elongatus) and the piscivorous (C. monoculus) Amazonian fish differ in composition and distribution of lipids, which show differences not only because of the different eating habits between the two species, but also by the availability and quantity of food along the year, i.e., during the flood and drought Amazon periods.