The paper deals with impact of toxic pollution on activity of energy and ion exchange enzymes in roach and perch. Significant changes in content of energy substrates in liver, gills and muscles of perch and roach were established depending on season and toxic load. The glycogen content in liver of perch specimens from the polluted lake (Kyrilivske) was lower than in specimens from the control lake (Babyne). Also, lower activity of SDH in muscles and gills of roach has been established. It should be noted that roach was characterized by higher variability of the studied enzymes' activity. This indicates the species specificity of the metabolic reactions of the studied fishes to counteract toxic pollution.