Concentrations of Ag, Pb, and Hg in samples of aquatic insects and feeding sources such as algae and leaves were determined at four sites along the Ginzan River, Which receives drainage from a mined land. Nitrogen (δ¹⁵N) and carbon (δ¹³C) isotope analyses of the samples were carried out to assess whether feeding sources or the trophic level influenced metal accumulation in each faunal taxon. The individual dry mass was also measured to examine the effect of body size on metal accumulation. The relationship between metal concentrations and level of δ¹⁵N in fauna indicated biodilutions for Pb (3 sites) and Ag (1 site) through the food webs. This must be caused by high concentrations of metals in algae and fine particulate organic matter (FPOM) as the main feeding sources for harvivores and detorivores. The relative contribution of autochthonous and allochthonous energy sources to each taxon's biomass had no effect on the concentrations of Ag, Pb, and Hg in the fauna. The individual dry mass was negatively correlated with the concentrations of Ag (3 sites), Pb (1 site), and Hg (4 sites) in fauna.