Linking historical fishing pressure to biodiversity outcomes to predict spatial variation in Marine Protected Area performance

Abstract

Marine Protected Areas (MPAs) often have dual goals of protecting biodiversity and increasing sustainability of fisheries. To understand how MPAs are performing at these goals, evaluation of fish biomass outcomes against management targets is needed. However, the evaluation of performance should consider multiple biophysical and social drivers that vary over the seascape to inform spatially explicit targets for fish biomass. Including spatial variation when evaluating MPA performance is particularly important for MPA networks because it enables managers to set more realistic expectations for MPA outcomes and adapt management across individual areas. Here we develop a modelling approach to predict how fishing pressure and biophysical conditions affect expected recovery of fish biomass. We apply the approach to model herbivore and predator biomass at 57 sites for two MPAs in Raja Ampat, Indonesia. We then use this model to predict biomass recovery towards reference sites indicative of low-fishing pressure. We found that historical fishing pressure, wave exposure and proximity to coastal habitats were all important determinants of pre-MPA fish biomass. Our predictions therefore, indicated the implemented MPA no-take zones should have some of the highest reef fish biomass based on both their location within the MPA, and the removal of fishing pressure. We also identify sites that may be underperforming and warrant further management, for instance, further investigation of poaching as a cause of poor recovery trends. We suggest that evaluation of MPA performance needs to consider the link to historical fishing pressure and biophysical conditions with biodiversity outcomes.