U.S. Fish & Wildlife Service Abundance and Run Timing of Adult Pacific Salmon in the East Fork Andreafsky River, Yukon Delta National Wildlife Refuge, Alaska, 2018 Alaska Fisheries Data Series Number 2019-2 Fairbanks Fish and Wildlife Conservation Office Fairbanks, Alaska February 2019 The Alaska Region Fisheries Program of the U.S. Fish and Wildlife Service conducts fisheries monitoring and population assessment studies throughout many areas of Alaska. Dedicated professional staff located in Anchorage, Juneau, Fairbanks, and Kenai Fish and Wildlife Offices and the Anchorage Conservation Genetics Laboratory serve as the core of the Program’s fisheries management study efforts. Administrative and technical support is provided by staff in the Anchorage Regional Office. Our program works closely with the Alaska Department of Fish and Game and other partners to conserve and restore Alaska’s fish populations and aquatic habitats. Additional information about the Fisheries Program and work conducted by our field offices can be obtained at: http://alaska.fws.gov/fisheries/index.htm The Alaska Region Fisheries Program reports its study findings through the Alaska Fisheries Data Series (AFDS) or in recognized peer-reviewed journals. The AFDS was established to provide timely dissemination of data to fishery managers and other technically oriented professionals, for inclusion in agency databases, and to archive detailed study designs and results for the benefit of future investigations. Publication in the AFDS does not preclude further reporting of study results through recognized peer-reviewed journals. Cover Photo: View upriver in the East Fork Andreafsky River valley, from a hill above the weir site, 2018. Photo courtesy of M. Larson, USFWS. Disclaimer: The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service. The use of trade names of commercial products in this report does not constitute endorsement or recommendation for use by the federal government. Alaska Fisheries Data Series Number 2019-2, February 2019 U.S. Fish and Wildlife Service Chinook and Summer Chum Salmon Abundance, Run Timing, and Age, Sex, Length Composition in the East Fork Andreafsky River, Yukon Delta National Wildlife Refuge, Alaska, 2018 Jan M. Conitz Abstract A weir was operated on the East Fork Andreafsky River from June 25 through July 29, 2018, to estimate salmon escapement and run timing. The primary target species were Chinook and summer Chum salmon, but all fish species passing the weir were enumerated. An underwater video system was used to record images of fish passing the weir 24 hours per day, every day of the operating period. Crew members counted fish, by species, from video recordings each day. For the days before and after the operation period, that fell within the historically known migration period, a Bayesian statistical procedure was used to estimate Chinook and summer Chum salmon passage. Chinook and summer Chum salmon were sampled to estimate age, sex, and length composition of the escapement. Chinook Salmon counted at the weir totaled 4,114 fish, and the total estimated escapement was 4,171 (95% Bayesian highest posterior density interval, HPDI, 4,116–4,358) Chinook salmon. Summer Chum Salmon counted at the weir totaled 36,330 fish, and the total estimated escapement was 38,250 (95% HPDI, 36,710–41,690). There were 4 age classes of Chinook Salmon present: age-1.1 (males only), -1.2, -1.3, and -1.4). The largest age-sex group of Chinook Salmon was age-1.3 males, representing about 51% of the run past the weir, followed by age-1.2 males (about 24%) and age-1.3 females (about 18%). There were also 4 age classes of summer Chum Salmon in 2018: age-0.2 (males only), -0.3, -0.4, and -0.5. The largest group of summer Chum salmon was age-0.3 males (about 31%), followed by age-0.3 females (about 29%) and age-0.4 males (about 22%). The same brood years, 2012–2015, were represented in both species sampled at the weir. Incidental counts of other species included 96,349 Pink Salmon O. gorbuscha, 1,198 Sockeye Salmon O. nerka, 12 Coho Salmon O. kisutch, and 2,270 whitefish (Coregoninae). This was the 25th consecutive year of weir operation in this lower Yukon River tributary. Introduction The Andreafsky River is a significant salmon producing tributary of the lower Yukon River, and supports some of the largest runs of Chinook Oncorhynchus tshawytscha and summer Chum O. keta Salmon in the Yukon River drainage. Located within the Yukon Delta National Wildlife Refuge, the Andreafsky River is designated a wild and scenic river, one of seven wild and scenic rivers in the National Wildlife Refuge system in Alaska.1 The Andreafsky River is also the lowest major tributary in the Yukon River drainage, entering the Yukon River main stem about 160 river kilometers (rkm) from the Bering Sea. The Yukon River extends over 3,190 rkm, from icefields in British Columbia, Canada, near the Gulf of Alaska through the Yukon Territory and Alaska to its mouth on the Bering Sea coast. The escapement monitoring project on the East Fork of the Andreafsky River is a key point in a drainage wide network of salmon monitoring and assessment projects, representing lower river stocks and providing information on salmon abundance, run timing, and stock composition. Escapement estimates from the East Fork 1 https://www.fws.gov/alaska/water/wildrivers.htm Author: Jan Conitz is a fisheries biologist with the U.S. Fish and Wildlife Service, and can be contacted at the Fairbanks Fish and Wildlife Conservation Office, 101 12th Ave., Room 222, Fairbanks, Alaska 99701; or [email protected]. Alaska Fisheries Data Series Number 2019-2, February 2019 U.S. Fish and Wildlife Service Andreafsky River weir are combined with aerial survey estimates from both the East and West Forks and used by fisheries managers as in-season and post-season indices of lower river escapement. Subsistence fisheries in the U.S. portion of the Yukon River drainage are jointly managed by the State of Alaska, under the Alaska Department of Fish and Game (ADF&G), and the U.S. Fish and Wildlife Service (USFWS) under the Federal Subsistence Management program. Commercial, sport, and personal use fisheries are managed by ADF&G. Within the National Wildlife Refuge, federal managers are responsible for conserving fish and habitats in their natural diversity, fulfilling international treaty obligations, supporting subsistence resource use by local residents, and protecting water quality.2 Both state and federal managers are responsible for ensuring priority of subsistence fishing use, protecting stock diversity, ensuring equitable distribution of harvest opportunity across the drainage, and meeting Canadian border passage objectives as specified by the Yukon River Salmon Agreement. In addition, ADF&G establishes escapement goals for various salmon populations in Yukon River tributaries. Among these are East Fork Andreafsky River Chinook and summer Chum salmon (Volk et al. 2009; Fleischman and Evenson 2010). Salmon returning to the Andreafsky River contribute substantially to subsistence and commercial harvests in the lower Yukon River. Residents of some 20 communities, small villages, and fish camps located on the Yukon Delta and Yukon River below the Andreafsky River confluence harvest salmon from mixed stocks entering the Yukon River. Most residents harvest fish for subsistence use, but many also participate in small-scale commercial fisheries. Income from commercial fishing enables families to purchase the necessary gear and supplies to sustain their subsistence fishing activities. Chinook Salmon are the primary target for subsistence fisheries in the lower river, but summer and fall Chum Salmon and Coho Salmon (O. kisutch) are also harvested. Commercial fisheries harvest summer Chum Salmon during the early season, and shift to fall Chum and Coho salmon after mid-July, in the lower river.3 The Andreafsky River has been an important indicator for lower Yukon salmon runs for many years. Aerial surveys were conducted on both the East and West forks in most years since 1954.4 ADF&G experimented with sonar on the East Fork in the early 1980s (Buklis 1982) and operated a fish counting tower there from 1986 to 1988. The East Fork Andreafsky River weir in its current configuration has been operated annually by USFWS since 1994; and this year was the 25th consecutive year of operation. The escapement information from East Fork Andreafsky River is useful for in-season management because it generally lags run timing through the lower river fisheries by only a few days. Most subsistence and commercial fishing in the lower Yukon River occurs in the main stem, harvesting from mixed stocks of salmon returning to spawning areas throughout the drainage. Although individual stocks cannot be specifically targeted or avoided, in-season genetic information and daily updates from escapement counting projects are monitored closely to ensure that certain stocks are not disproportionately harvested. Genetic mixed-stock analysis (MSA) compares genotypes of harvested fish with a baseline of genotypes from known 2 https://www.fws.gov/refuge/Yukon_Delta/what_we_do/resource_management.html 3 The commercial sale of Chinook salmon has been prohibited since 2012 (Estensen et al. 2017). 4 http://www.adfg.alaska.gov/CommFishR3/Website/AYKDBMSWebsite/Default.aspx 2 Alaska Fisheries Data Series Number 2019-2, February 2019 U.S. Fish and Wildlife Service spawning populations. Genetic baselines have been developed for both Chinook5 and Chum salmon (Flannery et al. 2007) in the Yukon River. In both species, genetically distinct lower river stocks cover a broad geographic area, encompassing spawning populations in tributaries and the main stem from the Yukon River Delta up to the Gisasa River in the lower Koyukuk River drainage. All populations within the lower Yukon River Chum Salmon stock are genetically identifiable as summer Chum Salmon.