Mercury levels of fish in Tucuruí hydroelectric reservoir and in River Mojú in Amazonia, in the state of Pará, Brazil

High mercury (Hg) levels were found in fish of Tucurui reservoir and River Moju polluted by mercury due to gold mining activities. The highest Hg concentrations were measured in predatory fish (1.3 ± 0.89 mg/kg, N = 121), intermediate values in planktivorous and omnivorous fish (0.32 ± 0.20 mg/kg, N = 89) and the lowest values in herbivorous fish (0.11 ± 0.11 mg/kg, N = 14). Tucurui reservoir is thoroughly polluted by mercury. Only the side basin of Caraipe had a little less mercury in fish. Tucunare (Cichla temensis) and pescada (Plagioscion squamosissimus) seemed to be good indicator species for mercury pollution in Tucurui reservoir. In Tucurui reservoir and in River Moju, 92% and 100%, respectively of the predatory fish samples contained more than 0.5 mg Hg/kg, which is the safety limit for Hg in Brazil. The consumption of large predatory fish from the study area should be restricted to avoid the risk of methylmercury poisoning in humans.

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