AUTHORSHIP
J.M., I.T., and Y.O. conceived this study; K.T., A.Y., K.S., K.H., H.M., and S.N. provided copepod samples and contextual information; J.M. and T.N. provided chum salmon samples and contextual information; J.M. performed sectioning of salmon vertebrae and collagen extraction from bone samples; J.M., N.O.O., N. F. I., N.O., and I.T. performed bulk and compound-specific stable nitrogen isotope analysis; C.Y provided data for nitrate utilization and phytoplankton stable nitrogen isotope ratios in the North Pacific; Y.O. developed a statistical model to estimate salmon migration routes; J.M., Y.O., and C.Y. wrote the first draft of the paper; all authors were involved in interpreting the results and contributed to the final draft of the paper; J.M. and Y.O. contributed equally to this work.