Researchers with the Alaska Fisheries Science Center (AFSC) say they’re speeding up the process of gathering data to share with the fisheries managers and others on the decline of Chinook and chum salmon runs, particularly in western Alaska.
The AFSC, which is collaborating with state and federal researchers, as well as those at the university level, reported in late August that the center has developed models to better understand and help resource managers address bycatch impacts.
“These models, after accounting for natural mortality, produce estimates of the number of adult fish that would be expected to return to their natal rivers to spawn if they hadn’t been taken as bycatch in the Eastern Bering Sea Pollock fisheries,” their report states.
Salmon bycatch levels vary year to year, due to changing environmental conditions, run sizes, fleet behavior and other factors. In 2021, the directed Pollock fishery in the Bering Sea/Aleutian Islands had bycatch mortality estimated at 546,043 chum salmon, plus 13,783 Chinooks in the Pollock-directed fisheries and 15,895 Chinooks in all groundfish fisheries, the report said.
Genetic analysis indicated that 51,510 of the 545,883 chum salmon caught as bycatch in 2021 originated from rivers in Western Alaska, including the Yukon and Kuskokwim. The Western Alaska fish represented 9.4% of the total chum bycatch.
In 2020, 18,195 of the 32,294 Chinook salmon caught in the Bering Sea/Aleutian Islands groundfish fisheries were from western Alaska stocks including the Kuskokwim and Yukon. Those fish represented 56.4% of the total Chinook salmon bycatch.
Now NOAA Fisheries is working to determine if there are certain ties and areas where Pollock harvesters are more likely to encounter Western Alaska chum salmon. Research to date shows that in general the proportion of Western Alaska chum salmon caught as bycatch is greater early in the summer and further east, but NOAA researchers caution that these are initial estimates and further modeling is needed to determine if these patterns are supported by available data.
Data results showed that in 2020 an estimated 32,294 Chinook salmon were caught as bycatch by Pollock trawlers in the Bering Sea/Aleutian Islands. That bycatch estimate was 6% below the historical average of 34,589 Chinooks between 1991 and 2019. In recent years the Bering Sea Chinook salmon bycatch has stabilized near 20,000 fish. Researchers said regulatory changes have contributed to this demise in bycatch, with incidental harvest between 1991 and 2010 averaging 40,976 fish and after implementation of Amendment 91 between 2011 and 2019 the average dropped to 19.328 kings.
Amendment 91 is described as an innovative approach to managing Chinook salmon bycatch in the Bering Sea Pollock fishery that combines a prohibited species catch limit on the amount of Chinook salmon that may be caught incidentally with an incentive plan agreement and performance standard designed to minimize bycatch to the extent practicable in all years. Amendment 91 is intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the fishery management plan and other applicable laws.
Western Alaska was the largest contributor to the 2020 bycatch at 52%. Other amounts included 15% from British Columbia, 13% from the North Alaska Peninsula and 7% from the west coast of the Lower 48 states. Since 2017 the contribution of British Columbia and the west coast of the U.S. has been decreasing, while the proportion from Western Alaska stocks has been increasing, according to the report.
Researchers anticipate that the number of Western Alaska Chinook salmon caught as bycatch in 2021 will be consistent with 2012-2018 data, which were consistently below 8,000 fish.
Wes Larson program lead for the AFSC’s genetics program, said the center is collaborating with the commercial fishing industry to identify new ways of fishing and to explore fishing gear modifications and new technologies to minimize bycatch in commercial trawl fisheries.
Researchers in the genetics program are also working with partners from universities, state agencies and industry to develop stock-specific distribution models, in hope of predicting where certain important stocks, including those of Western Alaska, are found.
Center staff are also working on other studies in collaboration with the state of Alaska and indigenous communities to learn more about salmon ocean survival, disease and how warming ocean temperatures are affecting salmon growth, development and survival in Yukon-Kuskokwim river systems, the report said.