Comparison of Management Benchmarks Resulting from Single- and Aggregated Species Stock-Production Models

Ecosystem considerations for the management of single species stocks will require knowledge of the tradeoffs between implementing single- versus multi-species modeling techniques.  In this study we explore the effects of fitting stock production models and estimating benchmarks for single species and multiple species.  We used a multispecies Lotka-Volterra simulation program to create several ecosystem scenarios and generate species data with known dynamics for stock production models.   Scenarios included varying levels of fishing pressure, fishing pressure applied only to specific species, and scenarios in which fishing pressure was changed over time.  Time series of catch and an index of abundance from the Lotka-Volterra simulations were used as input to fit stock-production models.  Stock-production models were fit for both individual species and multiple species aggregated into one stock-production model.  Fisheries management benchmarks such as maximum sustainable yield were compared to the same benchmarks as estimated from aggregated species stock-production models.  The effects of species aggregation into a single stock-production model will be explored as well as the effects estimating maximum sustainable yield with and without accounting for species interactions.