Global distribution, threats and population trends of the critically endangered Balearic shearwater Puffinus mauretanicus

Abstract

Knowledge of the spatial distribution and population trends of threatened species is essential to improve their conservation status. We analysed a 21-year dataset (2000-2020) with at-sea counts of the critically endangered Balearic shearwater (Puffinus mauretanicus) to understand its distribution, habitat suitability, population trends, overlap with threats such as fisheries and offshore marine renewables, and overlap with Marine Protected Areas (MPAs). Our study reveals higher densities of Balearic shearwaters along the eastern Spanish coast, Balearic Islands, and the Atlantic Iberian coast, with recent expansion into the Celtic Sea, English Channel, and southern North Sea, indicating a northward shift in distribution. Species distribution models identified distance to coast and colony, bathymetry, and sea surface temperature as key predictors of habitat suitability. Population trends indicate a concerning decline in the Mediterranean and Atlantic Iberian coast, with a recent increase in northern Europe, though insufficient to offset declines in the main areas. Fisheries, particularly gillnets and purse seines, pose significant threats across the species' range. There is a critical need for data on artisanal longline fisheries to enhance threat assessments. Emerging threats from offshore wind farms do not appear to overlap with the species' primary distribution, but further investigation is needed. Although MPAs partially cover its range, their overlap is low, highlighting the need to update protected area networks and implement management plans. This study provides a global view of the distribution, habitat suitability, key threats, and population trends of the Balearic shearwater, offering crucial insights for the conservation of this critically endangered species.