Abstract <p>Identifying specimens of artificial and natural origin in a mixed sample of fish collected in a natural environment is a key ichthyological problem. A number of methods are used to address this issue, one of which is microchemical analysis of calcified structures. This paper presents the results of an analysis of 10 isotopes of six chemical elements in a section of the marginal ray of the pectoral fin of the sterlet <i>Acipenser ruthenus.</i> The fin sections were processed using laser ablation followed by mass spectrometric analysis. The hatchery originated sterlet had lower barium isotope concentrations compared to specimens of natural origin. It has been shown that the combination of barium, magnesium, manganese, and strontium isotope concentrations in the sterlet fin ray can be used to determine the origin of sterlet from specific hatcheries from which juveniles are released into the Kama River Basin. The results demonstrate the potential of this analytical method for assessing the effectiveness of stocking of natural water bodies by such a valuable species as sterlet.</p>