Disentangling the influences of climate change from other stressors affecting the population dynamics of aquatic species is particularly pressing for northern latitude ecosystems, where climate driven warming is occurring faster than the global average. Chinook salmon (Oncorhynchus tshawytscha) in the Yukon-Kuskokwim (YK) region occupy the northern extent of their species’ range and are experiencing prolonged declines in abundance resulting in fisheries closures and impacts to the wellbeing of Indigenous people and local communities. These declines have been associated with physical (e.g., temperature, streamflow) and biological (e.g., body size, competition) conditions, but uncertainty remains about the relative influence of these drivers on productivity across populations and how salmon-environment relationships vary across watersheds. To fill these knowledge gaps we estimated the effects of marine and freshwater environmental indicators, body size, and indices of competition, on the productivity (adult returns-per-spawner) of 26 Chinook salmon populations in the YK region using a Bayesian hierarchical stock-recruitment model. Across most populations, productivity declined with smaller spawner body size and sea surface temperatures that were colder in the winter and warmer in the summer during the first year at sea. Decreased productivity was also associated with above average fall maximum daily streamflow, increased sea ice cover prior to juvenile outmigration, and abundance of marine competitors, but the strength of these effects varied among populations. Maximum daily stream temperature during spawning migration had a nonlinear relationship with productivity with reduced productivity in years when temperatures exceeded thresholds in mainstem rivers. These results demonstrate for the first time that well-documented declines in body size of YK Chinook salmon were associated with declining population productivity, while taking climate into account.

This is a collated dataset of various freshwater indices for Feddern et al. "Body size and early marine conditions drive changes in Chinook salmon productivity across northern latitude ecosystems". The authors of this dataset were not the original collectors of these data, but instead collated them from publicly available datasets, reports, and published papers. They are archived here for reproducibility and the original sources should be acknowledged. We are very grateful to the people who originally collected these data and developed the associated models and run reconstructions. The data were collected from: 

Freshwater Covariates

Temperature data derived from Daymet: https://daymet.ornl.gov/ accessed 2022-11-26

Streamflow derived from GloFAS: https://essd.copernicus.org/articles/12/2043/2020/  via https://doi.org/10.24381/cds.a4fdd6b9 accessed 2022-11-26

Complete code can be found at: doi.org/10.5281/zenodo.13696302