Flooded forest environments are important for a large part of the frugivorous and omnivorous fish assemblage, which depend directly on the food items offered by these environments. The fish Brycon falcatus, popularly known as matrinxã, is a migratory characid, and is considered one of the main frugivorous species in the Teles Pires River basin, as it plays an important role in flooded forests in the dispersion of fruits and seeds that it consumes. During flood periods, the food supply becomes vast, since many species bear fruit at this time, and thus the fish have access to a great diversity of fruits. Among these fruits, there are some available that are notably not consumed by fish. In this sense, this study will determine the nutritional value of fleshy fruits belonging to the families Chrysobalanaceae, Euphorbiaceae, Fabaceae and Myrtaceae that are consumed by Brycon falcatus and evaluate possible secondary compounds in fruits that are not consumed. To this end, ripe fruits will be collected from the riparian forest of the Teles Pires river basin and laboratory analyses will be carried out based on nutritional content and secondary compounds.