In NPAFC catches for 1997-2025, warm PDO years did not raise Alaska salmon catch and the Alaska-WOC inverse pattern stopped; only the negative PDO link of WOC coho held as a forecast

We tested three published Pacific salmon catch-climate claims on NPAFC commercial catch data for 1997-2025, which the authors did not use: warm Pacific Decadal Oscillation (PDO) phases raise Alaska catch and lower Washington-Oregon-California (WOC) catch (Mantua et al. 1997), Alaska and WOC catches move in opposite directions (Hare et al. 1999), and total catch follows the Aleutian Low (Beamish and Bouillon 1993). We used 17 regional series (Alaska, Southeast Alaska, Canada, WOC), a pre-set plan, effective-sample-size intervals, random-walk forecast skill, and 1,000 surrogate PDO series. Detrended Alaska catch correlated with the marine-residence PDO in 1925-1996 (r +0.26 to +0.50 for five species) but not in 1997-2025 (-0.07 to +0.24), except sockeye (+0.43, 90% interval +0.08 to +0.68). The PDO kept its link to regional sea temperature, and regional SST also lost its link to Alaska pink and chum catch. The 1925-1996 Alaska link came from few regime contrasts and was confounded with the growth of Alaska hatchery releases after 1977. The negative link held in WOC: the year-to-year coho correlation was -0.41 (-0.64 to -0.12), and a 1925-1996 slope forecast 1997-2025 coho changes better than a random walk (skill +0.052, +0.019 to +0.088). It was the only one of 17 series that met the pre-set rule. The Alaska-WOC correlation changed from -0.47 to +0.13 (p = 0.03). The North Pacific Index gave no negative correlation with total catch in 1950-1992 and a positive one after 1992. PDO lags selected in training kept a small forward skill above the surrogate null (mean +0.016, p = 0.009), about 1.6% of the random-walk error. Limitations: catch is not abundance and depends on management; the NPI is a proxy for the ALPI; the forward period has few PDO phase changes. NPAFC data are not bundled; code, aggregate results, hashes and a retrieval script are included.