Core subject To quantify the Hg content of sediment and fish collected along the Purus River (Acre State, Amazon) in order to identify if those samples could be a potential route of Hg exposure to the population of Manoel Urbano (a riverside community). Methods The total mercury (THg) was quantified using the Cold Vapor Atomic Absorption technique. Results We collected 06 samples of sediment and 264 samples of fish. The Hg in sediments ranged between 0.038 and 0.065 µg.g–1.The results indicate that sediment is in agreement with “uncontaminated” Amazonian rivers. The carnivorous species presented the highest level of Hg on muscle (mean 0.927 μg/g–1), followed by piscivorous (mean 0.873 μg.g–1), planktophagus (mean 0.566 μg.g–1), omnivorous (mean 0.533 μg.g–1) and detritivorous (mean 0.176 μg/g–1). Fourty four percent (44%) of the total species collected presented mean levels of THg on muscle, a percentage greater than the threshold recommended by WHO. Conclusion Some species may be a route for Hg exposure. The sediment is within the normality. The authors suggest that other factors, such as culture and society, should be considered for future researches in order to promote the population healths.

This study provides new length‒weight (LWR) and length‒length relationships (LLR) for 25 indigenous fish species from Xingu River basin. Overall specimens were collected in different aquatic habitats in the Xingu River basin in quarterly collections between 2012 and 2018. The collections were carried out using distinct fishing gears, such as gill nets (20 to 180 mm mesh), seines (3 mm mesh), sieves (1 mm mesh), and casting nets (20 to 60 mm mesh). The present study shows the LWRs for 25 species, and the LLRs for 23 species. In addition, presents the new maximum total lengths for 20 species.

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Ecological traps occur when species choose to settle in lower-quality habitats, even if this reduces their survival or productivity. This happens in situations of drastic environmental changes, resulting from anthropogenic pressures. In long term, this could mean the extinction of the species. We investigated the dynamics of occurrence and distribution of three canid species (Atelocynus microtis, Cerdocyon thous, and Spheotos venaticus) considering human threats to their habitats in the Amazon Rainforest. We analyzed the environmental thresholds for the occurrence of these species and related to the future projections of climatic niches for each one. All three species will be negatively affected by climate change in the future, with losses of up to 91% of the suitable area of occurrence in the Brazilian Amazon. A. microtis appear to be more forest-dependent and must rely on the goodwill of decision-makers to be maintained in the future. For C. thous and S. venaticus, climatic variables and those associated with anthropogenic disturbances that modulate their niches today may not act the same way in the future. Even though C. thous is least dependent on the Amazon Forest; this species may be affected in the future due to the ecological traps. S. venaticus, can also undergo the same process, but perhaps more drastically due to the lower ecological plasticity of this species compared to C. thous. Our results suggest that the ecological traps may put these two species at risk in the future. Using the canid species as a model, we had the opportunity to investigate these ecological effects that can affect a large part of the Amazonian fauna in the current scenario. Considering the high degree of environmental degradation and deforestation in the Amazon Rainforest, the theory of ecological traps must be discussed at the same level as the habitat loss, considering the strategies for preserving the Amazon biodiversity. K E Y W O R D SAtelocynus microtis (short-eared dog), Cerdocyon thous (crab-eating fox), ecological traps, general linear model (GLM), niche modeling, Speothos venaticus (bush dog)