Marine hotspots of activity inform protection of a threatened community of pelagic species in a large oceanic jurisdiction

Remote oceanic islands harbour unique biodiversity, especially of species that rely on the marine trophic resources around their breeding islands. Identifying marine areas used by such species is essential to manage and limit processes that threaten these species. The Tristan da Cunha territory in the South Atlantic Ocean hosts several endemic and globally threatened seabirds, and pinnipeds; how they use the waters surrounding the islands must be considered when planning commercial activities. To inform marine management in the Tristan da Cunha Exclusive Economic Zone (EEZ), we identified statistically significant areas of concentrated activity by collating animal tracking data from nine seabirds and one marine mammal. We first calculated the time that breeding adults of the tracked species spent in 10 × 10 km cells within the EEZ, for each of four seasons to account for temporal variability in space use. By applying a spatial aggregation statistic over these grids for each season, we detected areas that are used more than expected by chance. Most of the activity hotspots were either within 100 km of breeding colonies or were associated with seamounts, being spatially constant across several seasons. Our simple and effective approach highlights important areas for pelagic biodiversity that will benefit conservation planning and marine management strategies.Supporting information: Figure S1. A three‐dimensional model of the bathymetry in Tristan da Cunha EEZ highlighting the seamounts. Figure S2. Plot of the raw tracking data of all 10 species considered in our analysis of marine hotspots within the Tristan da Cunha EEZ (indicated by the solid black line). Table S1. Plot of the raw tracking data of all 10 species considered in our analysis of marine hotspots within the Tristan da Cunha EEZ (indicated by the solid black line). Table S2. Phenology of the seabird species breeding in the Territory of Tristan da Cunha. Tristan Table S3. Proportion of the time‐at‐sea spent by different species inside and outside the Tristan EEZ based on tracking data of pelagic megafauna activity in the Tristan da Cunha Exclusive Economic Zone. Figure S3. The tracks of three Blue Shark (Prionace glauca) tagged during the National Geographic’s Pristine Seas expedition to Tristan da Cunha (January to February 2017), using MiniPAT tags (Wildlife Computers).Darwin Plus Programme, South African Agency for Science and Technology Advancement, South Africa and UK (RSPB) BirdLife International partners and South African National Antarctic Programme (SANAP).https://zslpublications.onlinelibrary.wiley.com/journal/146917952021-03-25hj2021Mammal Research InstituteZoology and Entomolog