OTOLITH CARBON AND OXYGEN ISOTOPIC SIGNATURES OF JUVENILE CHUM SALMON (ONCORHYNCHUS KETA)

To investigate the role of carbon (<italic>δ</italic>¹³C) and oxygen (<italic>δ</italic>¹⁸O) stable isotopes in juvenile otoliths for identifying chum salmon (<italic>Oncorhynchus keta</italic>) groups, this study analyzed cultured and wild juvenile chum salmon groups (under 1 year old) using stable isotope mass spectrometry. The results showed that the mean <italic>δ</italic>¹⁸O and <italic>δ</italic>¹³C values in otoliths of the cultured group were (−10.33±0.30)‰ and (−8.60±0.45)‰, while those of the wild group were (−9.90±0.34)‰ and (−11.76±0.65)‰, respectively. Significant differences in otolith stable isotopes were observed between the two groups, primarily attributed to distinct freshwater habitat conditions experienced during their early life stages. By analyzing the correlation between <italic>δ</italic>¹⁸O and <italic>δ</italic>¹³C in juvenile chum salmon otoliths, cultured and wild juveniles were successfully discriminated, demonstrating the feasibility of juvenile otolith isotopes for tracing the origin of migratory adult chum salmon. This approach also provides a scientific basis for evaluating the effectiveness of artificial stock enhancement and its ecological impact on wild groups.