Abstract
AbstractRemote 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.
Highlights
Remote oceanic islands provide breeding grounds for pelagic predators such as seabirds and pinnipeds, which have to return to land to breed, and disperse widely across ocean basins to forage for marine resources (Block et al, 2011; Dias et al, 2017; Harrison et al, 2018)
The extent of the Exclusive Economic Zone (EEZ) used by tracked animals varied among seasons, with 75% of the EEZ used in spring, 68%
Our analysis highlights that these mobile marine predators are not uniformly distributed throughout the EEZ
Summary
Remote oceanic islands provide breeding grounds for pelagic predators such as seabirds and pinnipeds, which have to return to land to breed, and disperse widely across ocean basins to forage for marine resources (Block et al, 2011; Dias et al, 2017; Harrison et al, 2018). Protecting the pelagic areas on which these wide-ranging species depend can be challenging because many of these areas lie in waters beyond national jurisdiction where the establishment and enforcement of protection regimes is complex (Game et al, 2009; Game et al, 2010; Oppel et al, 2018). Among the most important islands for pelagic predators in the South Atlantic Ocean is the UK Overseas Territory of Tristan da Cunha, which constitutes one of 62 global marine provinces (Spalding et al, 2012), but its biodiversity is currently not adequately represented in marine protected areas. An effectively managed protected area in this marine province could, play a significant role in ensuring adequate representation of biodiversity in the global network of protected areas (Venter et al, 2018)
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