Integrated study of indigenous people’ local ecological knowledge and diet analysis to understand the feeding ecology of the herbivorous serrasalmids in a dammed Amazonian River

The Xingu River is facing impacts from the recently built Belo Monte Hydropower Plant (HPP), which is jeopardizing the pacus (herbivorous fish of the family Serrasalmidae and primary food source for the Yudjá people) derived from the Big Bend of Xingu (BBX). Part of the water volume in the BBX was redirected to an artificial canal as part of the Belo Monte HPP project. Thus, this study aims to analyze the trophic ecology of pacus through diet analysis and the Local Ecological Knowledge (LEK) of the Yudjá people using a qualitative-quantitative approach on the diet of those fish and check potential changes in fish welfare (mass/total legth3) in the BBX after the construction of the Belo Monte HPP. Overall, 133 specimens of eight herbivorous serrasalmid species were sampled after the damming, and previous data on 107 fish specimens of five species were gathered from landings. Terrestrial plants, fruits, and aquatic plants have the highest dietary importance for these fish, indicating the great importance of floodplains and rapids for herbivorous serrasalmids. Well-being, body size, and total mass show that these fish are already being negatively affected by the damming. The Yudjá are thus already feeling these impacts. The current water flow in the BBX is meagre for fish maintenance, and consequently, for the Yudjá people in BBX. Therefore, the amount of water flow to the BBX needs revision to avoid irreversible impacts.