Ecotoxicological Assessment of Mercury in Fish From a Gold-Mining-Impacted Amazonian River: Biomonitoring and Human Health Risk.

The Peixoto de Azevedo River, located in northern Mato Grosso, southern Brazilian Amazon, has a long history of artisanal and small-scale gold mining (ASGM). This study evaluated total mercury (THg) concentrations in fish tissues to assess biomagnification and potential risks. THg was determined by atomic absorption spectrometry in scales, skin, muscle, and liver of three species representing distinct trophic niches: Cichla sp. (predator), Hemiodus sp. (generalist), and Hypostomus sp. (detritivore). Predator muscle exhibited the highest THg concentrations, followed by generalist and detritivore species, confirming biomagnification along the food chain. The liver consistently showed the highest THg levels, while scales demonstrated potential as a non-invasive biomonitoring tool. Mercury was detected in all samples, underscoring the need for continuous monitoring. Risk assessment indicated elevated hazard for consumption of Cichla sp., moderate for Hemiodus sp., and low for Hypostomus sp. These findings highlight the ecotoxicological relevance of mercury contamination in mining-impacted rivers and provide methodological advances for biomonitoring strategies. Beyond toxicological implications, the results contribute to advancing biomonitoring strategies in ASGM regions and provide evidence to inform environmental management policies and public health strategies. In this context, the study supports international commitments such as the United Nations Sustainable Development Goals (SDGs 2, 3, 6, and 12) and the Minamata Convention, reinforcing the integration of ecotoxicology with sustainable development and governance.