Spatial scale and conservation options for carpet sharks

Although there is considerable momentum for expanding protected area coverage, a key criticism is the lack of connection to species-specific conservation outcomes. Conservation action needs to be tailored to species characteristics, such as behaviour, life-history traits, migratory range, as well as the scale and intensity of existing threats. Due to their small average size (<10 km²), Marine Protected Areas (MPAs) are likely to be more beneficial for species with smaller geographic ranges than for larger pelagic migratory species. We developed a conservation classification scheme for the 28 Critically Endangered (n = 1), Endangered (n = 4), Vulnerable (n = 12), Near Threatened (n = 6) and Data Deficient (n = 5) carpet sharks (Order: Orectolobiformes) based on their distribution, biology, and threats. Carpet sharks exhibit large diversity in their life histories and ecology; ranging from the Halmahera Epaulette Shark that reaches a 70 cm (total length, TL) with a geographic range of 14,446 km² to the Whale Shark that reaches 21 m TL and geographic range of 171,000,000 km². We find that none of these carpet sharks would benefit exclusively from a single site-scale MPA protection; instead MPA networks or a combination of MPAs with broad-scale threat mitigation measures are needed for over half of the species due to the broad geographic ranges and widespread overfishing. The choice of measures would depend on (a) fraction of the population moving between sites, (b) how diffuse are the inter-site movements, and (c) the presence or otherwise of significant barriers or threats to connectivity. Hence, MPAs on their own will not solve widespread overfishing, and instead diagnosis and a tailored treatment is likely to be more effective than a single cure-all. Fishing mortality will also need to be reduced around, as well as eliminated within, MPAs to ensure maximum conservation benefit.