Using an aggregate production simulation model with ecological interactions to explore effects of fishing and climate on a fish community

Ecosystem-based fishery management requires operating models that are capable of evaluating the effects of a triad of drivers (exploitation, ecological interactions, and the physical environment) on fish populations. We present a simple operating model, AGG-PROD, that takes into account these drivers. AGG-PROD aggregates species into functional groups and applies exploitation rates to these groups, while accounting for the interactions between these groups and the environment. We loosely modeled the Northeast US Large Marine Ecosystem fish community, exploring a range of harvest, ecological interactions (competition and predation), and climate effects scenarios. We examined the independent effects of each of the triad of drivers at their base levels on the 3 main functional groups. We then explored the effects of targeted harvest on specific functional groups as well as different levels of total system harvest, both with and without climate effects. Our results indicate that the triad of drivers can lead to unanticipated, indirect effects on groups of species, and that all 3 should be taken into account by an operating model in a Management Strategy Evaluation context. Harvest tends to affect groups with a slower overall growth rate the most, while groups affected by strong ecological interactions often exhibit strong competitive or predatory release when other groups are reduced in biomass. Climate effects reduce primarily the biomass of groundfishes in our model, indicating the need for more conservative exploitation under future climate projections.