
Western Alaskan Chum Bycatch Assessment
About
BBSRI, in collaboration with NOAA, launched the Western Alaskan Chum Bycatch Assessment as a pilot project in 2024 to produce weekly genetic stock compositions of chum salmon during the shoreside B-season pollock trawl fishery.
The goal of the project is to provide more timely stock composition information on chum salmon bycatch that can be used as a tool by the pollock trawl fleet to reduce impacts on Western Alaska chum salmon.
Bycatch Assessment Program
While NOAA estimates genetic stock compositions of bycaught chum salmon at the end of each season, BBSRI recognized the potential value of frequent in-season monitoring of chum stock proportions. Our project produced weekly estimates of chum stock proportions throughout the 2024 B-season, which demonstrated a high degree of variability in stock proportions as the season progressed. This in-season data provides a new and valuable tool to fisheries managers and trawlers to minimize the impact of the shoreside trawl fishery on western Alaskan chum.
Chum Bycatch
Chum salmon are occasionally caught in the pollock trawl fishery as bycatch. While many of these chum are of hatchery origin from East Asia, the Gulf of Alaska, and the Pacific Northwest, a proportion of those caught are wild chum from coastal western Alaska, Kotzebue Sound and the Upper/Middle Yukon River.
Many chum stocks in these western Alaska regions have seen population declines in recent years and hardship on subsistence users, which has prompted calls for the pollock fishery to minimize bycatch of Western Alaska Chum salmon.
Management efforts have focused on reducing total chum bycatch, however a decrease in total chum bycatch does not always equate to a decrease in western Alaskan chum bycatch.

Six regional groups of baseline chum salmon populations:
Red: SE Asia, Orange: NE Asia, Yellow: W Alaska/Kotzebue Sound, Light Blue: Up/Mid Yukon, Purple: SW Alaska, Dark Blue: EGOA/PNW
Port Sampling
Our technicians collect biological samples from bycaught chum that are delivered to Dutch Harbor and Akutan processors. In addition to tissue samples used for genetic analysis, technicians collect scale samples (for age data) and length measurements from each fish, which can be linked back to the fish's genetic profile. In order to sample every catch, technicians are available 24 hours a day, 7 days a week throughout the pollock B-season.


Genetic Analysis
Tissue samples are delivered to BBSRI's genetic lab in Dutch Harbor, where a subset of the sampled fish are randomly selected for analysis. DNA is then extracted from the selected samples and processed using automated rt-PCR equipment. This procedure amplifies and identifies 96 genetic markers to generate genotypes for the fish. This genotype data is then sent to NOAA's Auke Bay Lab Genetics Program, where it is analyzed and stock composition estimates are generated.
Preliminary Results
The results from the 2024 season show that the proportions of many chum genetic stocks that were bycaught in the pollock fishery fluctuated significantly throughout the sampling period, between June 13 and October 5. The E. Gulf of Alaska/PNW constituted the largest proportion of chum caught throughout the season (34.5%), and raged in proportion from a high of 69.8% of total catch in Statistical Week 24 to a low of 17.0% in Statistical Week 30. Similarly, SE Asia stocks increased from 9.2% in Statistical Week 24 to 33.1% in Statistical Week 27, remained high through Statistical Week 31, but declined for the rest of the season.
Conversely, there was no apparent pattern in the proportion of W Alaska, Up/Mid Yukon, SW Alaska, and Kotzebue Sound stocks, which remained at relatively low levels throughout the season. The differences in variation both between stocks and within each stock throughout the season demonstrate the value of frequent in-season stock composition estimates, as this information would not be available from a single post-season analysis.

Stock proportions (top) and weekly stock catch (bottom) of chum salmon bycatch from the shoreside B-season BSAI pollock trawl fishery, 2024 (Head, et al. 2025, In Prep).
Collaborators
NOAA - Auke Bay Laboratories
Assisted with project design and implementation, produced inseason stock composition estimates and verified genetics results
ADF&G - Gene Conservation Lab (GCL) and Mark, Tag and Age Lab (MTA)
The GCL provided additional verification of genetics results, and assisted in project design, training and lab trials
The MTA produced age data from a subset of sampled scales
Processors
Five processors voluntarily participated in and facilitated port sampling:
Dutch Harbor Processors - Westward Seafoods, Alyeska Seafoods, Unisea, Northern Victor
Akutan Processor - Trident Seafoods
Many Individuals and Fishing Vessels
There were many individuals and fishing vessels who helped through the lead-up to the season and throughout the 2024 feasibility year
A full report and data from the 2024 season will be available below in March 2025.