| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 2014 The Bering Sea has alternated between warm and cool spring thermal regimes, as defined by May sea surface temperature, and in recent years has remained in a "cool" state. Differences in spring thermal regime influence the timing of sea ice extent in the southeastern Bering Sea (SEBS) region, with warm springs facilitating early ice retreats and cool springs resulting in later ice retreat. A recent conceptual model for relating production to higher trophic levels in the SEBS proposes that during years of early sea ice retreat, phytoplankton blooms occur in warm water and support small, lipid-poor species of zooplankton. Conversely, years of late sea ice retreat results in an ice associated bloom that supports large, lipid-rich species of zooplankton. As a consequence the energy density of prey sources available to higher trophic levels is reduced during warm years and enhanced during cool years. While the northeastern Bering Sea (NEBS) has consistently supported an ice-associated bloom, it is likely that productivity in the SEBS influences trophic-level connections in the NEBS. In order to examine this possibility, we extended this conceptual model to juvenile salmon and compared size and condition of juvenile chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in the NEBS between spring thermal regimes of the SEBS. We hypothesized that juvenile salmon would be longer in warm years and more energy dense in cool years. In years with cool springs, pink salmon were shorter and chum salmon exhibited greater energy density, but no other aspects of size and condition differed significantly between spring thermal regimes. We further examined relationships of size, growth, and condition of juvenile salmon with environmental variables within the NEBS. For both species, length increased over the time of the surveys; longer individuals were caught at stations with greater bottom depths and in cooler sea-surface temperatures, while individuals with high ...
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