Résumé
Background: Sharks are key components of virtually all marine trophic webs, but many species are suffering from overexploitation and stock declines. The conservation of sharks and their functions in an ecosystem and the development of management strategies rely heavily on our ability to assess and monitor their distribution and abundance. However, the assessment of mobile species in marine environments remains challenging, often invasive, resource-intensive, and dependent on taxonomic expertise. The advent of parallel sequencing technologies offers new, powerful tools for biodiversity assessment. This includes the retrieval, amplification, and sequencing of fragments of environmental DNA (eDNA) shed by organisms in aquatic habitats, with the possibility to rapidly gauge vast amounts of information on taxonomy and community structure. Results: Here, we employ this novel, rapid, and non-invasive eDNA metabarcoding approach, specifically targeted to infer shark presence, diversity, and abundance across a range of impacted versus protected/remote areas in both tropical Pacific and Atlantic regions. We detect tens of shark species whose geographical distribution and relative abundance coincide with established knowledge on biogeographic patterns and levels of anthropogenic pressure and conservation effort. These findings indicate that eDNA metabarcoding can be effectively employed to study shark diversity in pelagic habitats. Significance: Further developments in this field have the potential to drastically enhance our ability to assess and monitor elusive oceanic predators such as sharks, which are particularly difficult to quantify by means of traditional-methods, and lead to improved conservation strategies.