1. Climate change and human activities are transforming river flows globally, with potentially large consequences for freshwater life. To help inform watershed and flow management, there is a need for empirical studies linking flows and fish productivity.
2. We tested the effects of river conditions and other factors on 22 years of Chinook salmon productivity in a watershed in British Columbia, Canada.
3. Freshwater conditions during adult salmon migration and spawning, as well as during juvenile rearing, explained a large amount of variation in productivity.
4. August river flows while salmon fry reared had the strongest effect on productivity – our model predicted that cohorts that experience 50% below average flow in the August of rearing have 21% lower productivity.
5. These contemporary relationships are set within long-term changes in climate, land use, and hydrology. Over the last century, average August river discharge decreased by 26%, air temperatures warmed, and water withdrawals increased. 17% of the watershed was logged in the last 20 years. 
6. Our results suggest that, in order to remain stable, this Chinook salmon population being assessed for legal protection requires substantially higher August flow than previously recommended. Changing flow regimes – driven by watershed impacts and climate change – can threaten imperiled fish populations.

This dataset is a combination of several sources:

-Spawner and recruitment data from Fisheries and Oceans Canada, corrected for unmarked hatchery returns and fishing mortality using Regional Mark Processing Centre and Pasific Salmon Commission Chinook Technical Committee data

-Summarized hydrometric data from the Water Survey of Canada

-Smolt-to-age 3 survival data for Chinook released from Spius Creek hatchery

This dataset was used to fit Bayesian stock-recruit models. Before analysis, the hydrometric and smolt-to-age 3 survival variables were centered and scaled to mean=0 and SD=1. We also include an un-scaled data set here for reference. See https://github.com/lukewarkentin/nicola_chinook for complete analysis codes and raw data files.

Important note: For any re-analysis, contact Chuck Parken (Chuck.Parken@dfo-mpo.gc.ca) for any data revisions/updates. CWT data can have minor changes and new analysis should include most up to date data. CWT data is used to estimate smolt-to-age 3 survival and explotiation rate.