Individual and Population Benefits of Marine Reserves for Reef Sharks

No-take marine protected areas (MPAs) are a commonly applied tool to reduce human fishing impacts on marine and coastal ecosystems. However, conservation outcomes of MPAs for mobile and long-lived predators such as sharks are highly variable. Here, we use empirical animal tracking data from 459 individual sharks and baited remote underwater video surveys undertaken in 36 countries to construct an empirically supported individual-based model that estimates the conservation effectiveness of MPAs for five species of coral reef-associated sharks (Triaenodon obesus, Carcharhinus melanopterus, Carcharhinus amblyrhynchos, Carcharhinus perezi, and Ginglymostoma cirratum). We demonstrate how species-specific individual movement traits can contribute to fishing mortality of sharks found within MPAs as they move outside to adjacent fishing grounds. We discovered that the world’s officially recorded coral reef-based managed areas (with a median width of 9.4 km) would need to be enforced as strict no-take MPAs and up to 5 times larger to expect protection of the majority of individuals of the five investigated reef shark species. The magnitude of this effect depended on local abundances and fishing pressure, with MPAs required to be 1.6–2.6 times larger to protect the same number of Atlantic and Caribbean species, which occur at lower abundances than similar species in the western Pacific. Furthermore, our model was used to quantify partially substantial reductions (>50%) in fishing mortality resulting from small increases in MPA size, allowing us to bridge a critical gap between traditional conservation planning and fisheries management. Overall, our results highlight the challenge of relying on abundance data alone to ensure that estimates of shark conservation impacts of MPAs follow the precautionary approach. •Marine protected areas must extend over 10 km to protect site-attached reef sharks•More mobile reef shark species can be protected only if MPAs are over 50 km long•Annual fishing mortality was cut by 50% for all assessed species with 15-km MPAs•Atlantic MPAs should be 2.6× larger than Pacific MPAs to protect similar abundances Global tracking networks and underwater monitoring are providing new insights into marine animal movements and local abundances. Dwyer et al. use these datasets to measure the conservation effectiveness of MPAs, showing that the majority of the world’s coral reef-based MPAs are too small to protect five globally predominant coral reef s