Western Alaska Chum Salmon Bycatch Assessment in the Shoreside
B-Season Bering Sea Aleutian Islands Walleye Pollock Trawl Fishery,
2025 Annual Report

Executive Summary

In 2025, the Bristol Bay Science and Research Institute (BBSRI) successfully implemented the second year of a project to produce weekly inseason genetic stock-composition estimates of the chum salmon (Oncorhynchus keta) bycatch in the shoreside B-season Bering Sea and Aleutian Islands (BSAI) walleye pollock (Gadus chalcogrammus) trawl fishery. The goal of the project was to provide more timely stock composition information than was currently available (i.e., post-season annual estimates) that could be used as a tool by the shoreside sector of the pollock trawl fleet to aid in the tracking and reduction of Western Alaska (WAK) chum salmon bycatch. Chum salmon bycatch caught in the shoreside sector during the 2025 B-season BSAI pollock trawl fishery totaled 73,291 fish. This was considerably lower than the most recent 5-year average (2020–2024) of 159,361 fish. For deliveries completed from June 11 to October 30, 2025, six BBSRI personnel tissue-sampled 9,253 chum salmon (12.6% of total bycatch) from 1,081 vessel offloads at five processors located in Dutch Harbor (Alyeska, Northern Victor, Unisea, and Westward) and Akutan (Trident). Of the samples collected, 6,662 (72.0%) were subsequently processed at a genetics laboratory established and operated by BBSRI in Dutch Harbor. Of the samples processed, 6,269 (94.1%) were successfully genotyped (i.e., ≥80% of 84 loc iscored) and used to produce weekly stock-composition estimates by NOAA’s Alaska Fisheries Science Center Auke Bay Laboratories (AFSC-ABL) Genetics Program in Juneau. Based on all samples analyzed in 2025 (i.e., pooling all statistical weeks [StatWks]) and a total bycatch of 73,291 chum salmon, the largest contributing genetic group was the Eastern Gulf of Alaska/Pacific Northwest (64.1%; point estimate of 47,008 fish), followed by Northeast Asia (19.5%; 14,328 fish), Southeast Asia (8.5%; 6,237 fish), Coastal Western Alaska (5.2%; 3,815 fish), Southwest Alaska (1.4%;1,004 fish), and Upper/Middle Yukon (1.2%; 899 fish). The WAK aggregate consisting of the Coastal Western Alaska and Upper/Middle Yukon stock groups comprised 6.4% of the bycatch (4,714 fish). Weekly composition estimates for the WAK aggregate of stocks ranged from a low of 1.5% (StatWk 41) to a high of 25.2% (StatWks 24–25). Weekly stock composition results were released inseason to the public via an email distribution list and BBSRI’s website (https://www.bbsri.org/inseason-data). In 2025, BBSRI conducted additional stock-composition analyses to further assist with inseason fishery management. For four statistical weeks (StatWks 29, 33, 34, and 35), stock compositions were estimated for vessel aggregations on different fishing grounds (e.g., Unimak Area, Pribilofs, and Zhemchug Canyon). For three statistical weeks (StatWks 33, 35, and 38), stock compositions were estimated for individual “lightning-strike” deliveries (i.e., offloads with unexpectedly large numbers of bycatch). Results of these analyses were provided to Sea State Inc. (Bainbridge Island, WA) and used to inform inseason management decisions. BBSRI worked closely with NOAA, Alaska Department of Fish and Game (ADF&G), industry, and regional stakeholders to implement this project. Funding was provided through a direct legislative grant from the State of Alaska, as well as BBSRI.