Foraging range and habitat associations of non‑breeding Tristan albatrosses: overlap with fisheries and implications for conservation

Abstract

The Tristan albatross Diomedea dabbenena is Critically Endangered: > 99% of adults breed at Gough Island, central South Atlantic Ocean, where chicks are threatened by introduced predators. At sea they mostly remain within the South Atlantic Ocean, where they are threatened by incidental capture in longline fisheries. Conservation measures to reduce seabird mortality in pelagic longline fisheries are confined largely to fishing effort south of 25°S. This covers the core range of breeding Tristan albatrosses, but the distribution of non-breeding adults and immature birds is unknown. We tracked 14 non-breeding adult Tristan albatrosses from Gough Island for up to 3 yr, from 2004 to 2006, using geolocating loggers. All birds remained in the South Atlantic or southern Indian Oceans, and showed distributions centred on the Sub-Tropical Convergence. They used the SW Atlantic during the austral summer and the SE Atlantic and Indian Oceans as far east as Australia during the austral winter. Foraging effort was concentrated in areas of upwelling and increased productivity. The distribution of the tracked birds overlapped with a range of pelagic longline fisheries, especially off southern Africa. Of particular concern was that 2 birds spent several months off the coast of Namibia and in adjacent high seas north of 25°S, where there are currently no regulations to prevent seabird bycatch during pelagic longline fishing operations.KEY WORDS: Atlantic Ocean · Indian Ocean · Longline · Bycatch · Diomedea dabbenena · Namibia Resale or republication not permitted without written consent of the publisherEndang Species Res 22: 39-49, 2013 of reliable data on bird bycatch. In addition, many species of seabirds range over vast areas and are thus likely to encounter multiple threats at sea in a variety of management jurisdictions (both national Exclusive Economic Zones [EEZs] and high seas areas) and to interact with fleets that vary widely in terms of compliance with conservation measures where these are in place.The Tristan albatross Diomedea dabbenena breeds almost exclusively on Gough Island in the central South Atlantic Ocean. It is classified as Critically Endangered by the IUCN because of population declines caused by mortality on longlines and predation of chicks by introduced mice Mus musculus (Wanless et al. 2007, BirdLife International 2012. The population is estimated to be decreasing by almost 3% yr −1 , with annual mortality from longline fishing estimated to be around 250 individuals (Wanless et al. 2009). Tristan albatrosses have been killed by pelagic longline fisheries off Brazil (Olmos 1997, Cuthbert et al. 2005) and southern Africa (Petersen et al. 2009). A recent assessment conducted under the auspices of the International Commission for the Conservation of Atlantic Tunas (ICCAT) concluded that the Tristan albatross was one of the species most at risk from longline fishing within the ICCAT area of jurisdiction (Tuck et al. 2011). A qualitative risk assessment for seabirds in the area managed by ...

167 individuals versus millions of hooks: bycatch mitigation in longline fisheries underlies conservation of Amsterdam albatrosses

“…Two factors would support this inference. First, the higher bycatch rate used here may over‐estimate Amsterdam albatross bycatch risk, since it was measured off southern Africa, where many seabirds in general and albatrosses in particular (including the Amsterdam albatross, Thiebot et al ., ) aggregate during their non‐breeding period (Phillips et al ., ; Petersen et al ., ; Reid et al ., ). Consequently, albatross bycatch rates may be higher in this region (see the very high figures given in Ryan et al ., ) compared with other oceanic regions where Amsterdam albatrosses occur.…”

“…This latter contrast demonstrates the need to account for the specificities of each fishing area (i.e. the spatio‐temporal dynamics of fishing effort) to assess seabird bycatch risks in fisheries (Tuck et al ., ; Baker et al ., ; Trebilco et al ., ; Reid et al ., ; Jiménez et al ., ). The results obtained in this study for the non‐breeding stages, when the birds may wander at sea for more than 1 year, demonstrate the prime effect of fishing effort in producing this seasonal figure.…”

Identification of candidate pelagic marine protected areas through a seabird seasonal‐, multispecific‐ and extinction risk‐based approach

“…We used geolocator (global location sensor or GLS) tracking data from 14 seabird species, occurring at the southwest Atlantic Ocean during part or all of the annual cycle (Table ). Deployment and other details are provided elsewhere (Grémillet et al ., ; Croxall et al ., ; Phillips et al ., ; González‐Solís, Croxall & Afanasyev, ; González‐Solís et al ., ; Mackley et al ., ; Quillfeldt et al ., ; Ramírez et al ., ; Reid et al ., ; Missagia et al ., ; Krüger et al ., , ). The data were modelled in three different periods: summer (October–March), winter (April–September) and year‐round (January–December).…”

Marine debris ingestion by albatrosses in the southwest Atlantic Ocean

“…Wandering and Tristan albatrosses breed in South Georgia and Tristan da Cunha, respectively, and both breeding and nonbreeding birds use the southwest Atlantic; Wandering albatrosses forage over an extensive region from oceanic waters to the shelf break, whereas Tristan albatrosses forage almost exclusively in oceanic waters in the subtropical region (Nicholls et al 2002;Cuthbert et al 2005;Reid et al 2013). The reported plastic accumulation area for the subtropical south Atlantic gyre (Cózar et al 2014;Ryan 2014) matches very well with the distribution of Tristan albatross, at least during breeding, suggesting a greater susceptibility in this species to plastic ingestion.…”