Investigating high seas foraging conditions for salmon in the North Pacific: insights from a 100 year scale archive for Rivers Inlet sockeye salmon

The high seas phase of Pacific salmon life history remains particularly data limited, and the potential implications of climate impacts on ocean productivity for salmon condition and reproductive success is poorly understood. We used carbon and nitrogen stable isotopes (SI) from salmon scales to reconstruct aspects of the marine environment experienced by Rivers Inlet sockeye salmon (Oncorhynchus nerka) over the last century (1915-2016). Time series of SI compositions of salmon scale showed a greater variability after 1950, probably linked to more dynamic high seas environmental conditions. However, climate indices (e.g., PDO, ENSO) did not explain the SI variability. We assessed the time series with respect to changes in food web dynamics, including shifting trophic baselines, changes in prey / salmon diet, and changes in salmon foraging location. A significant correlation (r= 0.53) between sea surface temperature and δ13C enabled us to define the area of potential salmon distribution in the open ocean for approximately 9 months prior to sampling. This method shows high potential for stock specific high seas distribution mapping that could be combined with prey isotope values to inform stock specific foraging experience.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author