Project: Role of predator-prey interactions in marine ecosystem organization: development of a new toolbox and a comparison of key interactions in the Bering Sea and Gulf of Alaska ecosystems.

Climate and human perturbations of ecosystems act on species dynamics largely through predator-prey interactions. How such interactions evolve through space and time, and change from one ecosystem to another are critical aspects of understanding community dynamics. The Eastern Bering Sea (EBS) and the western Gulf of Alaska (GOA) are two adjacent marine ecosystems at about the same latitude but separated by the Alaska Peninsula. They are both inhabited by similar ecological communities, are both commercially exploited, and are both affected by similar large-scale climate forcing. However, the component species show different dynamics suggesting that the predator-prey interactions are different. These differences raise fundamentally important questions as to why these systems diverge and the consequences at the community and management levels. We propose to investigate the anatomy of key trophic interactions of the EBS and GOA. In particular, we focus our analysis on the characterization of predator-prey functional and numerical responses, basic components of predation that so often escape meaningful insight. The examined critical trophic links include interactions among adult arrowtooth flounder and juvenile pollock, as well as adult and juvenile pollock. These links form central energetic pathways, and are believed to affect the recruitment dynamics of walleye pollock in both ecosystems. An explicit focus of our analysis is on variability over space and time of predator-prey interactions. To fulfill our research objectives we propose three activities: 1) development of statistical models to examine scales of predator-prey interactions and temporally and spatially variable predator-prey relationships, 2) retrospective comparative analysis on the effects of climate change, commercial fishing and seascape of the selected marine ecosystems on the organizational structure of key species interactions, and 3) a workshop to examine methods of scaling-up from local observations, shifting processes as scale changes, and complexity and organizational structure in predator-prey interactions.