Larger cold pools were linked to a lower north-to-south ratio of flathead sole catch frequency at 113 Bering Sea stations, 1982–2025

We split regional fish catch-density ratios into positive-catch frequency and density within positive catches. We used 4,859 NOAA trawls at 113 fixed eastern Bering Sea stations in 43 survey years from 1982 to 2025. We selected six fish taxa by early mean biomass and pooled rock sole codes to address a 1996 recording change. Each log north-to-south density ratio equals the sum of its two log component ratios. Models included cold-pool area and a linear time term. For flathead sole, the positive-catch frequency ratio was 8.0% lower per additional 100,000 square kilometres of cold pool, with a nominal 95% autocorrelation-robust interval of 4.7% to 11.3% lower. The adjusted p value across all 24 reported coefficient tests was 0.000114. The relation remained negative in year-change, date, boundary, broader-station, and period checks. A four-survey residual-block interval also excluded zero. The total biomass-density slope was uncertain in the primary model and all listed checks. Pacific cod component contrasts depended on the station panel and error method. These results show that a clear species-level catch-frequency relation can occur with an uncertain biomass relation. They do not establish true occupancy, fish movement, or a causal temperature effect. The package includes source data, provenance, the local plan and correction, all estimates, code, figures, and independent and repeat checks.

Bering Sea · flathead sole · cold pool · trawl survey · species distribution · positive catch · reproducibility