Ecospace: Prediction of mesoscale spatial patterns in trophic relationships of exploited ecosystems, with emphasis on the impacts of marine protectedareas

Growing disillusion with the predictive capability of single species fisher ies assessment methods and the realization that the management approaches t hey imply will always fail to protect bycatch species has led to growing in terest in the potential of marine protected areas (MPAs) as a tool for prot ecting such species and allowing for rebuilding populations of target speci es and damaged habitat. Ecospace is a spatially explicit model for policy e valuation that allows for considering the impact of MPAs in an ecosystem (t hat is, trophic) context, and that relies on the Ecopath mass-balance appro ach for most of its parameterization. Additional inputs are movement rates used to compute exchanges between grid cells, estimates of the importance o f trophic interactions (top-down vs bottom up control), and habitat prefere nces for each of the functional groups included in the model. An applicatio n example, including the effect of an MPA, and validation against trawl sur vey data is presented in the form of a color map illustrating Ecospace pred ictions of biomass patterns on the shelf of Brunei Darussalam, South-east A sia. A key general prediction of Ecospace is spatial "cascade" effects, whe rein prey densities are low where predators are abundant, for example, in p rotected areas or areas where fishing costs are high. Ecospace also shows t hat the potential benefits of local protection can be easily negated by hig h movement rates, and especially by concentration of fishing effort at the edge of the MPAs, where cascade effects generate prey gradients that attrac t predators out of the protected areas. Despite various limitations (for ex ample, no explicit consideration of seasonal changes or directed migration) , the outward simplicity of Ecospace and the information-rich graphs it gen erates, coupled with the increasingly global availability of the required E copath files, will likely ensure a wide use for this approach, both for gen erating hypotheses about ecosystem function and evaluating policy choices.