Small-sized and well-enforced Marine Protected Areas provide ecological benefits for piscivorous fish populations worldwide

Many piscivorous fish species are depleted and/or threatened around the world. Marine Protected Areas (MPAs) are tools for conservation and fisheries management, though there is still controversy regarding the best design for increasing their ecological effectiveness. Here, on the basis of a weighted meta-analytical approach, we have assessed the effect of 32 MPAs, distributed worldwide, on the biomass and density of piscivorous fishes. We analysed the MPA features and the biological, commercial and ecological characteristics of fishes that may affect the response of species to protection. We found a positive effect on the biomass and density of piscivores inside MPAs. This effect was stronger for the biomass of medium-sized fishes (in relation to the maximum size reported for the species) and the density of large and gregarious species. The size of the no-take zone had a significant negative impact on both response variables and differed according to the level of enforcement, with smaller no-take zones having higher levels of enforcement. Thus, MPAs help to protect piscivorous fish species, with smaller, but well enforced reserves being more effective for the protection of the local populations of piscivorous fishes throughout the world.