Diets and Prey Items of Juvenile Chinook (Oncorhynchus tshawytscha) and Coho Salmon (O. kisutch) on the Yukon Delta

Juvenile Chinook salmon on the Yukon River undertake one of the longest fish migrations in the world, travelling over 3,000 km from spawning grounds in Canada to the marine waters of the Bering Sea. Evidence suggests that much of the variability in Yukon River Chinook salmon production occurs prior to the end of the first summer at sea, either during freshwater rearing, downstream migration, or entry into the marine environment. Prey availability and prey quality are important factors in juvenile Chinook salmon growth and condition. This research investigated spatial and temporal patterns in juvenile Chinook and coho prey consumption and availability on the Yukon River Delta. Results suggest that while there are limited spatial differences in prey availability, prey varies seasonally. Juvenile Chinook and coho exhibit similar selectivity for invertebrate prey. Comparisons of the results of this study with data from prior sampling years indicates that juvenile Chinook salmon in 2016 had lower stomach fullness and lower energy densities than Chinook from prior years. Additional years of prey sampling are needed to identify factors that affect prey availability. 2020 NMFS (National Marine Fisheries Service) AFSC (Alaska Fisheries Science Center) Submitted https://doi.org/10.25923/rjxv-v629 Public Domain 1861