Deep-sea and deeply vulnerable: Assessing the conservation status of the kitefin shark (Dalatias licha)

Deep-sea ecosystems harbor highly vulnerable species, yet their conservation status remains poorly understood. The kitefin shark (Dalatias licha), a large deep-sea mesopredator, exemplifies this challenge. In the Azores archipelago (Portugal), historical industrial fisheries exploited this species from the 1970s until the late 1990s. The species shows life-history traits typical of low-productivity elasmobranchs, including slow growth, late maturity, and very low intrinsic population growth (5 % per generation). Using fisheries-dependent data, including catch reconstructions (1972–2018), and catch-per-unit-effort, we applied age-structured demographic models and biomass dynamics approaches to assess population status. Our results indicate that past historical exploitation depleted the population, reducing biomass to critically low levels. Although some recovery has been observed since fishery closure, rebuilding is extremely slow, and current biomass remains at only ∼56 % of that expected for a sustainable population. These results highlight the need to recognise the kitefin shark as a highly vulnerable species and to implement precautionary conservation measures, particularly in data-limited deep-sea fisheries.