Semiquantitative determination of total mercury in Pygocentrus nattereri Kner, 1858 and sediment at the plateau of Upper Paraguai River, Brazil

•We evaluated Hg contamination in the sediment and fish along a major river, from its source.•We assess the effectiveness of simple and efficient techniques for Hg pollution estimation.•Our data evidence P. nattereri as a sentinel organism for assessing Hg redistribution.•Our previous studies support results presented; fish species studied presents THg concentrations to the Paraguay River lone.•Other studies in our group discuss mechanisms of Hg availability for the biota in the Pantanal of Mato Grosso.

In this study an environmental assessment of contamination by total mercury (THg) was carried out at the Plateau of the Upper Paraguai River. Total mercury was evaluated in sediment and muscle of the red piranha Pygocentrus nattereri Kner, 1858, a piscivorous species at the top of the food chain consumed for subsistence and commercially. THg concentrations were below national guidelines established by WHO for sediments (100 ng g−1) and fish (100-600 ng g−1) for most of the sampled sites. Two sites located downstream of artisanal diamond and gold mines had THg concentrations in fish equal or greater than 600 ng g−1.