The interactions between selenium (Se) and mercury (Hg) were assessed on fish, crabs, and molluscs to assess the risks to public health associated with dietary exposure to mercury from their consumption. To this end, mass concentrations of mercury and selenium have been determined in the edible tissues of three species of fish, in crabs and molluscs taken from the rivers of the gold zones of Fizi in South Kivu in the Democratic Republic of Congo. We found values greater than 1 µg/g Hg in all fish samples regardless of the river, but also that the Kimbi River was the most polluted with an average mercury content of about 5 µg/g. Crabs and molluscs also had Hg values greater than 1.