Retrospective stable isotope analysis of chum salmon
All sampled individuals shared common trends inδ 15NBulk along the vertebral axis (Fig. 2): δ 15NBulk values were almost identical (mean ± SD: 10.5‰ ± 0.3‰) in Section 1 (closest to the middle of the centrum) among sampled individuals, then gradually decreased from the center to middle sections, increased rapidly in the marginal sections, and finally reached the highest value in the last section (12.7‰ ± 0.7‰; Table S4).
The δ 15NAAs showed that the TP in the bone sections of OK2 and OK8 ranged from 3.0 to 3.5 and from 3.0 to 3.4, respectively, and no clear trends along the growing axis of vertebral sections were found (Table S4). Theδ 15NBase andδ 15NBulk values of vertebral sections of the two salmon individuals were highly correlated (r 2 = 0.754 for OK2 and 0.916 for OK8).