Assembly Rules for Aggregate-Species Production Models: Simulations in Support of Management Strategy Evaluation

A key aspect of ecosystem-based fisheries management is assessing sustainability at multiple levels of organization beyond single target species. For this, appropriate biological reference points (BRPs) for aggregated groups of species need to be developed. But what are the potential risks and benefits of applying aggregate management measures to the individual species in the ecosystem? We used multispecies surplus production models to determine the potential consequences of applying alternative aggregate BRPs to a simulated fish community (based on Georges Bank). Population trajectories of individual interacting species in the community were simulated in manner that included predation and competitive interactions among species. Species trajectories were then binned into aggregates by functional feeding guild, taxonomy, habitat association, and at the entire community level. We derived BRP’s (e.g., MSY) by estimating production model parameters based on each type of aggregated time series. We then applied the MSY fishing rates associated with these aggregations as alternative fishing strategies to the simulated community and compared equilibrium biomass and yield under each strategy. In general, species aggregated with similarly productive species fared well under an aggregate fishing strategy, with little loss in yield and with similar equilibrium biomass compared to a single species strategy. However, less productive species were at risk of extinction when grouped with highly productive species. We propose a set of guidelines as operational advice for developing aggregate reference points based upon these results.