Foraging habitat suitability of black-browed albatrosses Thalassarche melanophris wintering in the South-west Atlantic Ocean: Acknowledging age class to improve conservation management

Abstract

Seabirds, particularly albatrosses, are among the most threatened birds as a result of their continuous exposure to anthropic pressures including interaction with commercial fisheries, climate change and pollution. Several studies that have focused on the spatial distribution of foraging seabirds have identified a certain level of segregation between age classes. The black-browed albatross Thalassarche melanophris is the most abundant albatross species in the South-west Atlantic Ocean and the main pelagic seabird interacting with a range of fishing fleets. There is a considerable lack of knowledge about the biology of immature individuals and on habitat suitability of the species during non-breeding season (winter). The aim of this study was to assess the foraging habitat suitability of the black-browed albatross in the South-west Atlantic during the austral winter, analysing differences between adults and immatures individuals. Habitat suitability models were based on foraging locations recorded by 15 satellite transmitters deployed on six adults and nine immature individuals between 2011 and 2015. Remotely sensed oceanographic data were used to characterize suitable foraging habitat for the albatrosses. Differences were found in foraging habitat suitability by age class, with adult selecting areas located in deeper waters over the continental shelf break as well as in neritic zones under cooler water temperatures, whereas immature individuals foraged chiefly off coastal waters having more moderate temperatures. Knowing habitat suitability and segregation patterns within-species is key for the conservation of critical marine habitats given that, by only considering one age class, other important habitats would be neglected and not considered in conservation efforts to mitigate threats such as incidental mortality. It is important to include all age classes when studying patterns of associations with threats, such as fishing activity as a proxy of risk of bycatch, and for the development of Marine Protected Areas.