Our study focuses on the European perch (Perca fluviatilis) regarding differences in concentrations of the biogenic (P, S, Cl, K, Ca, Mn, Zn) and metallic (Sr, Sb, Rb, Pb, Mo, Cr, Fe) elements relative to perch morphology and environmental factors at the largest dam in Slovakia. The juvenile perch were sampled at four capture sites from June to October. The highest concentration of biogenic elements and metals was found in perch caught in the site disposed to wastewater effluent (WWE). The concentrations of biogenic elements in perch decrease with the size of the fish; at most the perch affected by WWE had the smallest size. The concentration of biogenic elements in perch increased with the date from June to October and with water temperature for all sites. Lead accumulated by the perch in all sites exceeded more than five times the maximum permissible limits provided by international institutions.