Interdecadal changes in at‐sea distribution and abundance of subantarctic seabirds along a latitudinal gradient in the Southern Indian Ocean

Abstract

Long‐term demographic studies have recently shown that global climate change together with increasing direct impacts of human activities, such as fisheries, are affecting the population dynamics of marine top predators. However, the effects of these factors on species distribution and abundance at sea are still poorly understood, particularly in marine ecosystems of the southern hemisphere. Using a unique long‐term data set of at‐sea observations, we tested for interdecadal (1980s vs. 2000s) changes in summer abundance and distribution of 12 species of Albatrosses and Petrels along a 30° latitudinal gradient between tropical and Antarctic waters of the southern Indian Ocean. There were contrasting effects of climate change on subantarctic seabird distribution and abundance at sea. While subtropical waters showed the highest rate of warming, the species that visited this water mass showed the greatest changes in distribution and abundance. The abundance of Wandering Albatrosses (Diomedea exulans), White‐chinned Petrels (Procellaria aequinoctialis) and Giant Petrels (Macronectes sp.) declined markedly, whereas the other species showed contrasting trends or did not change. With the exception of the White‐chinned Petrel, these decreases were at least partly related to regional increase in sea surface temperature. The southward shift of Wandering Albatross and Prions (Pachyptila spp.) distributions could be ascribed to species redistribution or decrease in abundance due to warming of the subtropical waters. Surprisingly, White‐chinned Petrel distribution shifted northward, suggesting more complex mechanisms. This study is the first to document a shift in species range in the Southern Ocean related to climate change and contrasting abundance changes. It suggests that some species might experience more severe impacts from climate change depending on the water masses they visit. As climate changes are predicted to continue in the next decades, understanding species responses to climate change is crucial for conservation management, especially when their conservation status is critical or unknown.

Distribution and Abundance of Antarctic and Subantarctic Seabirds Within an Offshore Transect Between Rio Grande/Rs and Rio De Janeiro/Rj

“…T. chlororhynchos presented low frequency of occurrence (FO <4.00%) in the Indian Ocean (Péron et al, 2010), whereas in the Atlantic Ocean, on the Brazilian coast, high frequency of occurrence (FO = 58.82%) was found for this species. e di erences in abundance of some species between the sampled years might be explained by variations in the distance of the observers Latitude 29° S showed the largest abundance of seabirds with 41 individuals, although the highest richness was observed at latitudes 26° S e 30º S, with ve species in each from the coast, depth, water temperature, atmospheric pressure, and wind speed (Krüger & Petry, 2011) which were not analyzed in this study.…”

Antarctic and Sub-Antarctic Seabirds in South America: A Review

“…Many species are long-range migrants, with their routes over the South American countries still under studied by marine ornithologists. Long-term demographic studies have recently shown that climate change, together with direct impacts of human activities (such as overfishing, bycatch, and pollution), are affecting population dynamics of marine top predators, including seabirds (Ormerod 2003, Ramos et al 2009, Péron et al 2010a, 2010b. Consequently, studies on seabirds migration routes over oceanic areas and coastal lands are very important for conservation and management plans.…”

“…Seabirds are important components of the marine ecosystems and are the most studied taxa in relation to long-term demographic studies on land (Weimerskirch 1997, Péron et al 2010a, 2010b. However, ecological studies in open ocean areas are rare, since logistic procedures to support field works are exceedingly difficult (Tasker et al 1984, Weimerskirch 1997.…”

Occurrence and Mortality of Antarctic and Sub-Antarctic Seabirds Along the Southern Brazilian Coast

“…Important components of the marine ecosystem, seabirds are widely distributed and have large migratory movements (Péron et al, 2010). Some species are recorded using the South Atlantic region as a resting and foraging area.…”