Abundance and Run Timing of Adult Salmon in the Gisasa River, Koyukuk National Wildlife Refuge, Alaska, 2023: Alaska Fisheries Data Series Number 2024-3

A resistance board weir was operated by the U.S. Fish and Wildlife Service, Northern Alaska Fish and Wildlife Field Office to collect information on abundance, run timing, and biology of returning adult Chinook Salmon Oncorhynchus tshawytscha and summer Chum Salmon O. keta in the Gisasa River. The weir has been operated at this location since 1994 except for 2018, 2020, and 2021. This is the sixth-year video technology has been incorporated into the project since 2015. In 2023, the weir was operated from the end of the day on July 4 through August 2 during which an estimated 477 Chinook Salmon and 16,921 summer Chum Salmon passed through the weir. Other species enumerated through the weir, in order of abundance, were Northern Pike Esox lucius (N = 69), Sockeye Salmon O. nerka (N = 23), Longnose Sucker Catostomus catostomus (N = 6), Humpback Whitefish Coregonus pidschian (N = 4), Dolly Varden Salvelinus malma (N = 2), Arctic Grayling Thymallus arcticus (N = 1), Broad Whitefish Coregonus nasus (N = 1), and Pink Salmon O. gorbuscha (N = 1). A total of 33 Chinook Salmon and 288 summer Chum Salmon were sampled for age, sex, and length (ASL) data. The sample size goal was not met for Chinook Salmon and ASL analyses could not be performed for this species. The summer Chum Salmon ASL samples were divided into four strata (July 4 through 9, July 10 through 18, July 19 through 26, and July 27 through August 2). The estimated percent female based on weighted strata totals was 58. There were two primary age classes identified for summer Chum Salmon: 0.3 and 0.4. Length-at-age of male summer Chum Salmon was larger than females.