Foraging of seabirds on pelagic fishes: implications for management of pelagic marine protected areas

Abstract

Scientists and managers have become increasingly interested in how pelagic marine protected areas (PMPAs), or protected areas away from the coast, can be used to protect pelagic species. Subsurface-predator facilitated foraging ('facilitated foraging') between seabirds and subsurface predators, such as tunas, is a key ecological interaction in the tropical oceans where a number of large PMPAs have been created. In facilitated foraging, subsurface predators drive for- age fish to the surface, where they are made available to seabirds. Because this is a critical inter- action for seabirds, a reduction or cessation of fishing effort within tropical PMPAs may increase subsurface predator density, resulting in more foraging opportunities for seabirds closer to colonies. This interaction is well documented in the Eastern Tropical Pacific, and to a lesser extent in the Indian Ocean, but is poorly studied in the Central Tropical Pacific. Here, we review our cur- rent state of knowledge of facilitated foraging, particularly in relation to questions critical to PMPA management. We specifically consider 2 components of the foraging ecology of tropical seabird species: (1) diet and foraging methods, including flock feeding behavior, i.e. how species forage in association with other species or conspecifics, and (2) association with subsurface pred- ators. We consider the spatial scale of this interaction as it pertains to the distribution of seabirds and tunas and to PMPA boundaries. We conclude with discussion of data gaps and the implica- tions for managers. The present review of facilitated foraging will help focus future efforts and multidisciplinary collaborations on this important but understudied interaction.