Albatrosses are one of the iconic bird groups in the Antarctic. Almost no one can evade the fascination of these elegant birds when watching them sailing in the winds over the Southern Ocean. However, their numbers have made a significant drop over the last 35 years, especially those breeding on the sub-Antarctic island of South Georgia, according to a recent study published now in the Proceedings of the National Academy of Sciences.
The populations of wandering, black-browed and grey-headed albatrosses have halved over the last 35 years on sub-antarctic Bird Island according to a new study published in the journal Proceedings of the National Academy of Sciences. The research, led by scientists at British Antarctic Study (BAS), attributes this decline to environmental change, and to deaths in longline and trawl fisheries (known as bycatch). Overall, albatrosses are the world’s most threatened family of birds. There are 22 species; according to the IUCN Red List, 17 of these are ‘Threatened with extinction’ and the remaining five are considered to be ‘Near-threatened’. By analyzing the breeding histories of more than 36,000 individually ringed albatrosses, researchers have found decreases in the survival rates of both adults and juveniles, causing serious declines in population growth rates with long-lasting effects. Albatrosses are long-lived seabirds; the average lifespan is between 25 and 35 years, but individual birds can live to over 50 years, wandering albatross even over 60 years.
The study focused on albatross species nesting on Bird Island, next to South Georgia, where BAS has monitored the albatross since 1972. Breeding and non-breeding adults as well as chicks have been identified and ringed each year, and therefore high-quality demographic data are available to study the effects of age, sex, breeding status and year. Long-term monitoring allowed researchers to assess the population structure, breeding frequency, breeding success, and juvenile and adult survival rates of these three very long-lived albatross species in a changing environment. Currently, the populations consist of 700 pairs of wandering albatross, 3’000 pairs of grey-headed albatross, and 7’000 pairs of black-browed albatross. Lead author Dr Deborah Pardo of the British Antarctic Survey says: “Our study shows that bycatch in fisheries and environmental change both contribute to reducing the survival rates of the birds. While we know population sizes were affected by bycatch from the mid 1990s, more recent climatic changes including stronger and more poleward winds, increased sea surface temperature and reduced sea ice have worsened the impacts. We also found the grey-headed albatross population was particularly affected by the climatic event of El Niño, which coincided with increased fishing activity in their foraging areas . El Niño reduced the amount of food available so the birds probably switched to feeding on discards behind fishing vessels, increasing the number being hooked on longlines.”
This research highlights the importance of long-term monitoring data for understanding the impacts of fisheries. Despite the efforts to inform fisheries managers and operators, at present the regulations on seabird bycatch mitigation in many fisheries are not best-practice and are rarely enforced. Changing global climate is also a major threat, as it affects prey availability and foraging efficiency. Co-author Professor Richard Phillips of the British Antarctic Survey, says: “This is the first comprehensive study at South Georgia and one of the few globally to examine the impacts of both climate change and fisheries on populations of long-lived seabirds. Identifying that bycatch is having a major impact on grey-headed albatrosses was unexpected, as mortalities of this species during setting of longlines are rarely recorded by observers on board fishing vessels. The results underline how important it is to improve fisheries management. Whilst BAS has worked with Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) to introduce measures that have effectively eliminated bycatch around South Georgia, evidence from our long-term monitoring shows that more is needed elsewhere in the Southern Ocean to avoid the unnecessary deaths of tens of thousands of birds each year.”
Source: British Antarctic Survey