Recruitment hotspots boost the effectiveness of no-take marine reserves

No-take marine reserves are widely advocated as a means to conserve biodiversity and sustain fisheries. Within adequately protected reserves, the abundance, mean size and age of targeted fish and invertebrate species are often increased. However, the magnitude and rate of recovery within reserves varies among locations and species, and increases in abundance in reserves are not universal. One potential contributing factor to variability in reserve performance is spatial variability in the supply of recruits. Many reef fish species exhibit disproportionate levels of recruitment in relatively small areas (so-called "recruitment hotspots"). Here we tested the hypothesis that the presence of recruitment hotspots enhances the effectiveness of reserves for two important fishery species, coral trout (Plectropomus maculatus) and stripey snapper (Lutjanus carponotatus), on coral reefs of the Keppel Island group, Great Barrier Reef. To do this we compared fish densities in areas that did or did not contain previously identified recruitment hotspots, both inside and outside reserves. For both species, the mean densities of adult fish above the minimum legal size were approximately three times as high in reserves with hotspots than in reserves without hotspots. Furthermore, the mean densities in reserves without hotspots were similar to those in nearby areas that were open to fishing. In contrast, the densities of sub-legal size individuals of both species were primarily explained by the presence of recruitment hotspots, irrespective of reserve protection. Our results suggest that identifying and incorporating recruitment hotspots into the selection of sites for reserves could enhance both conservation and fisheries objectives