Exploitation of mesoscale oceanographic features by grey-headed albatrossThalassarche chrysostomain the southern Indian Ocean

• Published in: Marine ecology. Progress series (Halstenbek) 2001-07, Vol.217, p.15-26
• Main Authors: Nel, D. C., Lutjeharms, J. R. E., Pakhomov, E. A., Ansorge, I. J., Ryan, P. G., Klages, N. T. W.
• Format: Article
• Language: English
• Subjects: Birds; Breeding; Diet; Foraging; Marine fishes; Ocean currents; Oceanography; Oceans; Sea birds; Squid
• ISSN: 0171-8630; 1616-1599

Breeding grey-headed albatrossThalassarche chrysostoma, tracked from Marion Island (Prince Edward Islands) during November–December 1997 and January–February 1998, showed a strong association with mesoscale oceanographic features, as identified by sea surface height anomalies, in the southern Indian Ocean. During incubation, most birds foraged to the north of the island, at the edges of anomalies created by the Agulhas Return Current in the Subtropical Convergence and the Subantarctic zones. In contrast, during chick-rearing all tracked birds foraged to the southwest of the island, at the edges of anomalies along the South-West Indian Ridge. Previous work in this area has shown that these anomalies are in fact eddies that are created as the Antarctic Circumpolar Current crosses the South-West Indian Ridge. Diet samples taken during the chick-rearing period showed a predominance of fresh specimens of the predatory fishMagnisudis prionosaand the squidMartialia hyadesi. Myctophid fish and amphipodsThemisto gaudichaudii, both known prey ofM. hyadesi, were also well represented in our samples. Diet samples taken from tracked birds showed birds feeding at edges of positive anomalies returning with fresh specimens ofM. prionosaandM. hyadesi. Predatory fish and squid are thus presumably concentrated at these features. Eddies formed at the South-West Indian Ridge have also been shown to drift closer to Marion Island, within the foraging range of penguins and seals breeding on Marion Island. We therefore suggest that these mesoscale oceanographic features may be an important component of the ‘life-support’ system enabling globally significant populations of seabirds and seals to breed at the Prince Edward Islands.