Predator-Prey Spatial Overlap in Relation to Demographic and Climate Variables in the Eastern Bering Sea and Gulf of Alaska

The rising trend of arrowtooth flounder (Atheresthes stomias) biomass in eastern North Pacific ecosystems has raised concern over their predatory impact on the ecologically and economically valuable walleye pollock (Theragra chalcogramma). Arrowtooth flounder is a top predator in the Gulf of Alaska (GoA) and exerts a large source of mortality on pollock. In the eastern Bering Sea (EBS), arrowtooth flounder consume pollock, but the predation interaction is considered less important in this system. However, this interaction could intensify with higher abundances of arrowtooth flounder, and increased removals of pollock could have adverse consequences on other food web components. We are interested in better understanding the predation interaction of adult arrowtooth flounder on juvenile pollock. Because the strength of this trophic linkage is likely to depend on the degree of spatial overlap, we aim to evaluate the extent and magnitude of their overlap in relation to climate and demography. Specifically, we develop spatial overlap indices and use spatially explicit variable coefficient GAMs to evaluate the predator-prey horizontal overlap. Here we present our findings on the locations of greatest overlap within in the EBS and GoA and how the magnitude of overlap varies with changes in demographic and environmental conditions. We also discuss the potential implications of our findings on the trophic interactions between these key species. This work provides a strong foundation for quantifying arrowtooth flounder predation on pollock and evaluating how this trophic linkage may change under alternate climate scenarios.