Cristiane Carneiro

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.

Summary: The Neotropics have vast river catchments with untapped hydroelectric potential, but there are multiple expected negative impacts of dams, including those on local food security and livelihoods. Yet, monitoring of dam effects on subsistence is rare, particularly during initial implementation. Our study assessed changes in human fish consumption near the Belo Monte Dam in the Brazilian Amazon during the period 2012–2021, which covers construction, operation and a severe El Niño-induced drought. Over time, fish became less common and were consumed in smaller amounts, even though fewer people shared meals. The largest changes occurred between 2013 and 2016 (post-construction but prior to full operation), resulting in a downward trend in fish consumption, particularly during the drought season. Adding more fish species to the diet did not increase consumption per person. These changes in fish consumption suggest that they stem from environmental impacts of the project (e.g., reduced river level), despite secondary effects from climatic events. These findings underscore the urgent need for comprehensive assessments of the social and ecological impacts of large infrastructure projects in the Amazon, along with sustainable and equitable management strategies to ensure food security and meet the needs of local communities.

The Amazon suffers from the occurrence of mining along its hydrographic routes, which releases toxic substances into the aquatic environment. The objective of this study was to evaluate the risk of contamination by As and Hg that indigenous peoples are exposed to through the consumption of fish in an area impacted by mining activity in the basin of the Curuá and Baú Rivers, Altamira-PA. In total, 55 fish specimens and 30 surface water samples were collected. The decomposition of the fish samples was done by wet method with the use of nitric acid, hydrogen peroxide, and microwaves. The quantification of total mercury (THg) and total arsenic (TAs) was carried out by inductively coupled plasma optical emission spectrometry with vapor generation (VG-ICP OES). The methodology proposed by the U.S. Environmental Protection Agency was used. The results showed that TAs presents safe levels; however, THg presents a sample with levels up to (4.6 µg g-1), exceeding the permitted levels (1 µg g-1). The risk assessment shows that only the consumption of fish, linked to Hg, represents the existence of deleterious risks to indigenous peoples (hazard quotient (HQ)) > 1). Bioaccumulation factor (BAF) in fish represents a risk to indigenous people, because of the Hg’s presence. The study identified that illegal mining activities are responsible for Hg pollution in the Baú and Curuá Rivers. The fish species analyzed can be used as bioindicators of Hg in the rivers, which is relevant for making environmental and public health policy decisions.