Mean Annual Discharge and System Capacity for Chinook Salmon

Warkentin et al. (2022) used a time series of adult recruitment from the Nicola River to estimate the effects of August low flows in the brood year (x-axis) on returning adult recruits 4 years later (y-axis). The SR function was derived by regressing the annual residuals from the stock-recruit function on August low flows, reasoning that higher than average adult returns are correlated with higher than average flows in the brood year, and lower than average predicted flows (negative residuals) are correlated with lower flows (See figure 4e in Warkentin et al. 2022 for support of this mechanism). Average adult population size was added to the residuals to generate the final y-values (adult population response) for the final SR function, which was then standardized to a maximum of 1 (or 100% capacity; see Rosenfeld and Enright 2025).