“…However, studies considering other regions of the Amazon basin have shown that many fish species, including those that are known prey of Amazon river dolphin, 37 present high concentrations of heavy metals bioaccumulated in their tissues (e.g., cadmium, chromium, copper, lead, zinc, and mercury), both in areas with high mining activities (e.g., Madeira, Tapaj os, and Cassiporé Rivers) and in areas with low mining activities (e.g., Negro River). [43][44][45][46][47][48][49][50][51][52][53] Some studies reported that fish from floodplain lakes have high levels of Na, K, Cl, Ca, and Mg in their blood plasma and tissues (muscle, gills, and liver). 50,54 Some species and genera analyzed by Cruz et al 50 and Machado and Duncan 54 (e.g., Pinirampus pirinampu, Mylossoma duriventre, Sorubim lima, Astronotus ocellatus, Brachyplatystoma filamentosum, Cichla spp., and Colossoma spp.)…”