Eutrophication process affects the entire basis of the food chain in water bodies, so that there is usually a replacement of phytoplankton organisms rich in omega-3 long chain fatty acids, such as diatoms and dinoflagellates, with poor organisms in these molecules, as cyanobacteria. This change results in deficiency of omega 3 fatty acids to higher trophic levels, which may interfere with various physiological processes of these animals. We investigated the trophic transfer process of the fatty acids in two species of fish, an omnivorous and a carnivorous, from two reservoirs with different degrees of eutrophication, a mesotrophic and a hypereutrophic (Billings). Our results refuted the initial hypothesis, since both species from hypereutrophic environment showed high percentages of omega 3 fatty acids in the stomach contents and also in the tissues analyzed compared to the species from mesotrophic reservoir. The presence of a high prevalence of dinoflagellates, rich in omega 3 long chain fatty acids, beyond the constant bloom of cyanobacteria, explains the data found for these animals, contributing to the transfer to higher trophic levels.