Local ecological knowledge to assist conservation status assessments in data poor contexts: a case study with the threatened sharks of the Brazilian Northeast

The list of threatened species (Red List), established by the International Union for Conservation of Nature (IUCN), aims to provide global assessments on the extinction risk of species. However, protecting vulnerable populations requires establishing threat criteria at sub-global scales, e.g., national Red Lists. In data-poor contexts, typical of many developing countries, assessing threat status by applying IUCN criteria constitutes a major challenge, which may be one reason for mismatches between national and global Red List assessments. Despite the intense harvesting of threatened elasmobranchs species in Brazilian waters, Brazilian fisheries monitoring has ceased to exist for nearly a decade. This jeopardizes accurate assessment of species’ conservation status at a local scale. In the absence of fisheries records, local ecological knowledge (LEK) provides an alternative option to obtain reliable information on targeted species. We interviewed 186 fishers from four Brazilian Northeastern states, whose recollections spanned six decades and documented catches or sightings of 19 shark species. For eight species with sufficient data, temporal trends in maximum length of sharks caught by fishers of different age-classes were statistically tested. Four species’ maximum length declined over time, while four were primarily captured by elderly fishers, with few or no recent catches reported. Of these species, one is classified more conservatively in the national Red List vs. IUCN Red List, which is supported by LEK results. Contrastingly, two species are classified less conservatively at the national level than by IUCN, such that upgrading and matching IUCN’s conservation criteria is warranted. We suggest that LEK provides support for conservation status listing in data-poor contexts.