Stage-dependent distribution of the critically endangered Amsterdam albatross in relation to Economic Exclusive Zones
Résumé
Long-lived animals typically exhibit several stages throughout their life cycle during which their distribution may vary substantially, which may challenge the relevance of protection measures. Here we surveyed individual movements of the Critically Endangered Amsterdam albatross from Amsterdam Island, southern Indian Ocean, throughout its life cycle. Our goal was to identify, from the areas visited by the albatrosses, which coastal states share responsibility in regulating industrial fishing in their Exclusive Economic Zones (EEZs) in order to promote the preservation of this species. Using stage-relevant tracking techniques (satellite tags, GPS and GLS loggers), we surveyed 361 at-sea trips by 93 individuals over 9 yr, covering incubation, brooding, chick-rearing, sabbatical, failed-breeding, juvenile and immature stages. Our data show that Amsterdam albatrosses exhibit a wide and variable foraging radius (from 326 ± 193 km during brooding to 5519 ± 766 km for immatures) and at-sea distribution across stages, putting them beyond the French EEZ of Amsterdam Island for all or part of the trips surveyed in each stage, and even outside the Indian Ocean when breeding. In all, the breeding versus non-breeding albatrosses visited the EEZs of 1 to 3 versus 3 to 4 countries, respectively. Only breeders visited the EEZs of Madagascar and Mauritius, while only non-breeders visited the EEZs of Australia, South Africa and Namibia. This study stresses the relevance to conservation of obtaining synoptic information on the distribution of threatened species, especially regarding the breeding versus nonbreeding categories of populations.