Observed annual CPUE to abundance ratio data from Fraser River at Qualark, Mission, and Skeena River at Tyee: (A) Sockeye Salmon (2008–2019 Fraser data; 1982–2006 Skeena data) and (B) Chinook Salmon (2008–2023 Fraser data; 1984–2006 Skeena data). Also shown are the data-fitting curves to the disc model (right-hand-side of Equation 17) with black, dark gray, and light gray lines corresponding to yearly CPUE versus abundance relationships at Qualark, Mission/Whonnock, and Tyee, respectively.