| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2023 Chinook Salmon Oncorhynchus tshawytscha have experienced population declines across their range in recent decades, including Alaska where they are a critical subsistence, commercial, and sport fish species. The Alaska Board of Fisheries has listed Yukon River Chinook salmon as a "stock of yield concern" since 2000 prompting the implementation of escapement goals for key spawning tributaries in 2001. Additionally, research efforts across the basin have increased to better understand potential mechanisms behind these declines and provide information to facilitate management decisions. To help fill a critical data gap in the overall understanding of the fishery, this research investigated various freshwater juvenile life history factors including patterns in post-emergence summer body size, movement, and fish size during spring outmigration in the Chena River, Alaska. This research also identified links between these biological factors and freshwater processes that are affected by climate change, including stream temperature and discharge, with the intention of documenting benchmark information as conditions continue to change. Juvenile Chinook Salmon movement among four key rearing areas was observed during summer and fall 2019 and early spring 2020. Despite differences in early summer size patterns, by the end of September mean fork lengths were not statistically different among all rearing areas (ANOVA; all P > 0.05). Additionally, mean September weight varied among six years of empirical data and ranged from 3.19 g in 2018 (0.03 SE) to a maximum of 5.10 g in 2009 (0.05 SE). September weight was simulated across years with variable stream temperatures and discharge (2003 to 2020) using a bioenergetics model, and compared to observed data. Weight simulations were within <0.40 g of observed mean end of summer weight for all years except in 2019 when the predicted weight was 1.38 g greater than the observed mean September weight. Generally, both observed ...
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