Western Alaska Chum Salmon Bycatch Assessment in the Shoreside
B-Season Bering Sea Aleutian Islands Walleye Pollock Trawl Fishery, 2024 Annual Report

EXECUTIVE SUMMARY

In 2024, the Bristol Bay Science and Research Institute (BBSRI) successfully implemented a pilot 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 chum salmon bycatch.

Chum salmon bycatch caught in the shoreside sector during the 2024 B-season BSAI pollock trawl fishery totaled 21,710 fish. This was considerably lower than the most recent 5-year average (2019–2023: 189,820 fish). From June 13 to October 5, 2024, six BBSRI personnel tissue-sampled 7,034 chum salmon (32.4% of total bycatch) from 941 vessel offloads at five processors located in Dutch Harbor (Alyeska, Northern Victor, Unisea, and Westward) and Akutan (Trident). Of the samples collected, 3,531 (50.2%) were subsequently processed at a genetics laboratory established and operated by BBSRI in Dutch Harbor. Of the samples processed, 3,088 (87.5%) were successfully genotyped (i.e., ≥ 80% of loci scored). Weekly stock composition estimates were produced by the National Oceanographic and Atmospheric Administration’s (NOAA’s) Alaska Fisheries Science Center Auke Bay Laboratories (AFSC-ABL) Genetics Program in Juneau.

Based on all samples analyzed in 2024 (i.e., pooling all statistical weeks [StatWks]) and a total bycatch of 21,631 chum salmon through October 5, 2024 when sampling ended, the largest contributing genetic group to the chum salmon bycatch was Eastern Gulf of Alaska/Pacific Northwest (34.7%; point estimate of 7,516 fish), followed by Northeast Asia (29.7%; 6,430 fish), Southeast Asia (19.9%; 4,306 fish), Coastal Western Alaska (7.7%; 1,673 fish), Upper/Middle Yukon (5.1%; 1,109 fish), Southwest Alaska (1.8%; 397 fish), and Kotzebue Sound (0.9%; 200 fish). The Western Alaska (WAK) aggregate consisting of the Coastal Western Alaska, Kotzebue Sound, and Upper/Middle Yukon stock groups comprised 13.8% of the bycatch (2,982 fish). Weekly composition estimates for the WAK aggregate of stocks ranged from a low of 7.8% during StatWk 31 to a high of 19.2% during StatWk 34. The estimated contribution of the WAK aggregate of stocks was comparable to that produced independently by the AFSC-ABL Genetics Program using samples collected by the North Pacific Observer Program administered by the AFSC Fisheries Monitoring and Analysis Division (15.3%).

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 and BBSRI, with additional in-kind support provided by NOAA and ADF&G.