Processes driving differences in major food web linkages of the Gulf of Alaska and eastern Bering Sea ecosystems

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Key food web linkages and species dynamics can diverge in seemingly similar ecosystems due to differences among physical and biological factors. The eastern Bering Sea (EBS) and western Gulf of Alaska (GoA) represent two such ecosystems. These systems are adjacent at similar latitudes, separated by the thin Alaska Peninsula; they are inhabited by similar species communities, and are affected by similar anthropogenic and large-scale forcing. However, population dynamics of some of the key species, specifically arrowtooth flounder (Atheresthes stomias) and walleye pollock (Theragra chalcogramma) are driven by the differences in their predation interactions among these regions. For example, in the GoA predation by arrowtooth flounder exerts the highest source of predation mortality on juvenile pollock. In the EBS, predation by arrowtooth flounder is less important and cannibalism is the greatest source of predation mortality on pollock. These differences within the GoA and EBS food webs inspire questions about the causes and the consequences at the community level. Here, we evaluate the spatial overlap of arrowtooth flounder and pollock in the GoA and EBS systems and explore how environmental and demographic factors influence the variability in overlap. This work is useful for identifying conditions that may facilitate strong trophic interactions between these species. Such knowledge can improve our ability to quantify the predatory impact of arrowtooth flounder on juvenile pollock in relation to alternate climate scenarios.