Drivers and Dynamics of Salmon Bycatch in the Eastern Bering Sea Pollock Fishery

Abstract

Minimising bycatch is a pervasive challenge for sustainable fisheries management, the importance of which is amplified for non‐target species or populations that are in decline. In the eastern Bering Sea (EBS) walleye pollock (Gadus chalcogrammus) fishery, salmon—most notably Chinook (Oncorhynchus tshawytscha) and chum (O. keta)—are encountered as bycatch. Salmon bycatch in the EBS pollock fishery has become an issue of growing concern, largely due to declines in Western Alaska Chinook and chum salmon, which support directed fisheries vital to the wellbeing of regional communities. Consequently, minimising salmon bycatch is a management priority and requires information on the underlying processes driving encounters between salmon and pollock vessels. In this study, we present a broad synthesis of Chinook and chum salmon bycatch dynamics in the EBS pollock fishery. Applying a hierarchical modelling framework to nearly 120,000 catch records collected over 13 years (2011–2023), we quantify patterns of variation in salmon bycatch over space and time, and environmental drivers thereof. Our results reveal spatially structured, interannual variation in chum and Chinook salmon bycatch associated with oceanographic conditions. We also demonstrate the importance of interactions between bottom depth and local sea surface temperature anomalies in shaping bycatch rates, which vary across fishing seasons and salmon species. By advancing our understanding of the factors that contribute to encounters between pollock vessels and salmon, this study can inform ongoing management efforts aimed at minimising multispecies salmon bycatch in a changing marine ecosystem.