Including species interactions in the design and evaluation of marine reserves: Some insights from a predator-prey model

Conservation of marine species through fisheries management and no-take marine reserves have focused primarily on single species, but such protection may influence the target species' predators, prey, competitors, or mutualists. Conversely, successful protection may depend on responses of these other species. Empirical data and previous theory indicate that fisheries status and life-history attributes strongly influence species' responses to protection. Both direct effects and indirect effects of protection (through species interactions) have been documented. A predator-prey model depicting the dynamics of two species in a two-patch habitat (a no-take reserve and a fished area) revealed conditions under which the predator and prey may decline after reserve establishment. Not surprisingly, model results suggest that management scenarios and life-history traits leading to high predator population growth are more likely to produce prey declines following reserve establishment. Interestingly, trade-offs between enhancing predator and enhancing prey occurred at low fishing intensities regardless of the prey and predator life-history traits. At high fishing rates, reserve establishment generally outweighed predation effects and resulted in increased abundance of both predator and prey. Simple spatial models can help determine the range of possible responses of interacting species to protection and can yield some general insights for their management.