Water Mass Property Associations with Juvenile Chinook Salmon in the Northern Bering Sea; a Look at Warm and Cold Years

Although commercially important fisheries are present over both the northern and southern shelf of the Eastern Bering Sea (EBS), far more attention has been focused on the southern end. The oceanography and shelf dynamics between the north and south are markedly different above and below approximately 60º N latitude. Sea ice extent and duration, and freshwater inputs from the Yukon River are substantially higher in the north compared to the south, resulting in large variations in oceanography between the northern and southern EBS, and between localized areas within the northern EBS. Generalized additive models (GAMs) were fit with environmental and biological covariates (temperature, chlorophyll a, salinity, silicate concentration, Pacific Herring, and Capelin) to look at juvenile Chinook distribution changes between warm and cold years in the northern EBS. Two categories (top 10m‘Surface’, and bottom 10m ‘Bottom’) were investigated for both warm and cold years. Distributions varied between warm and cold years, both in terms of biomass and in terms of their model fits. Both cold year categories (surface and bottom) had higher deviances explained (>50%) and significant associations with a greater number of environmental covariates. Warm years had fewer significant environmental relationships and less robust model fits (<21% deviance explained). Temperature and salinity were significant for both cold year categories, and for neither of the warm year categories. Thus water column stability or outmigration timing during summer in the northern EBS may be important factors for juvenile Chinook salmon and will spawn further investigations.