Balancing nutrients and mercury: Nutritional composition and total mercury content in fish consumed in the Bolivian Amazon (Beni River)

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Freshwater fish are important sources of essential nutrients for Amazonian communities. However, mercury (Hg) contamination poses significant health risks. Since the nutritional value of fish and the risk associated with Hg-contamination are rarely evaluated simultaneously, this study aimed to assess the proximate composition, minerals content, fatty acid profiles, and total Hg concentrations of ten fish species from the Beni River, Bolivian Amazon. Nutritional quality was assessed using the thrombogenicity index (IT), hypocholesterolemic/hypercholesterolemic ratio (HH), and omega-6/omega-3 ratio. Results revealed contrasting lipid profiles and Hg contamination above international safety thresholds in certain species. Calophysus macropterus had the highest crude fat (21.8 ± 8.0 % dry matter), unfavorable lipid profile (IT = 0.1, HH = 1.0) and high Hg concentrations (1.9 ± 1.0 ppm wet weight). Piarachtus brachypomus showed high protein (23.9 ± 8.7 % dry matter), phosphorus (24.4 g kg-1), and together with Arapaima gigas beneficial fatty acid profiles, due to elevated essential polyunsaturated fatty acids (EPA and DHA), with low Hg content (< 0.5 ppm wet weight). These patterns were linked to trophic guilds and highlight the dual role of Amazonian fish as nutritional resources and potential mercury vectors, emphasizing the need for balanced consumption guidelines and risk mitigation strategies.