A wide range of information has been collected about the biotic components of Prince William Sound (PWS), Alaska since the 1989 Exxon Valdez oil spill. A balanced model of trophic flows, constructed using the Ecopath modelling approach, summarizes much of this information. This model is a cohesive synthesis of the overall PWS biotic community with a focus on its structure, and how it might respond to perturbations, both natural and anthropogenic. Flows of biomass (a proxy for energy) among the various components of the food web were quantified using estimates provided by a group of collaborators with expertise on PWS ecosystem components. Estimates of biomass, production/biomass ratios, consumption /biomass ratios, and diet composition, as well as migration rates, and fishery catches, were specified as (empirically-based) inputs for each defined ecosystem component. Outputs include refined biomass and flux estimates, as well as simulations of population trajectories in time and space, providing insight into ecosystem-level changes that may occur in the real Prince William Sound.