Qualitative food-web modeling to support ecosystem-based management: A case study of California current groundfish

Background/Question/Methods

Key to the success of ecosystem-based management is appropriately matching ecosystem models with management goals. Strategic options are best explored by models that operate at scales relevant to the ecosystem condition or policy action at hand. For this reason, we have developed small-scale ecosystem models to inform ecosystem-based management in the California Current, and to provide detail in support of larger “soup-to-nuts” ecosystem models. Here, we present a case study demonstrating the use of qualitative modeling to identify key predators and prey of several California Current groundfish species.

Results/Conclusions

Using quantitative diet information, we created food webs for canary rockfish, Pacific hake, bocaccio, and sablefish. These food webs were used to generate qualitative community matrices (A), and using the adjoint(-A) we calculated the general population response (increase, decrease, or no response) of each groundfish species to an increase or decrease in the population of each other member of its food web. Based on a measure of predictability calculated from the adjoint(-A), we identify the key prey and predators of each groundfish species. We show how qualitative models can be used to explore food-web consequences of changes in climate and/or fisheries management strategies. Finally, we compare the predators and prey identified through qualitative modeling with those identified using larger ecosystem models (namely, Atlantis), and demonstrate the advantages (and disadvantages) of relatively simple qualitative models, particularly in data-poor environments.