The main purpose of the study is establishment how radioactive contamination with different exposures affect aquatic living organisms by means of the fluctuating asymmetry determination. Studies are also aimed for the assessment of relative contamination of the water bodies by man-made radionuclides taking into account biological aspects. Represented results of studies are the pilot researches towards to the estimation of bilateral asymmetry of aquatic organisms in conditions of long-term radioactive impact and can be the part of complex radioecological monitoring of aquatic ecosystems within the Chernobyl accident Exclusion Zone in future.