Diet overlap among top predators at the South Orkney Islands, Antarctica
In order to understand interspecific trophic relationships between top predators, we analyzed diet information for nine bird and two seal species collected in the austral summer from 1996 to 2000 at South Orkney Islands. Overall, the diet of most of the predators was mainly composed of krill and fish. The percentage of re-occurrence of prey among predators ranged from 25.3 to 36.7, and fish, krill and squid re-occurred most frequently. The re-occurrence of fish among predator pairs ranged from 8.1 to 28.1. The species that re-occurred most frequently were the nototheniid fishes Gobionotothen gibberifrons, Nototheniops nudifrons and Nototheniops nybelini, and the myctophid Electrona antarctica. Prey overlap was greatest between Chinstrap (Pygoscelis antarctica) and Adélie (Pygoscelis adeliae) Penguins. Most predator pairs had high overlap of fish prey species. Predators that could forage on demersal and water column prey had yearly variable diets. This variability may be explained by fluctuations in krill availability. In years when krill is scarce (e.g. 2000), these predators diversify their diet by increasing the consumption of fish, which increases the re-occurrence of these preys in the diets. Our samples suggest the recovery of G. gibberifrons stocks around the South Orkney Islands and draw attention to the potential increase of interspecific food competition between predators under scenarios of decreasing krill availability. This information can be used to identify the ecological consequences of fluctuations in krill availability and aid in the management of krill fisheries.
KeywordsDietary overlap Top predators South Orkney Islands Antarctica
We would like to express our appreciation to Marcela Libertelli and members of Orcadas Station for their logistic help and field assistance.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interests.
- Anon (2014) Informe del Grupo de Trabajo de Seguimiento y Ordenación del Ecosistema, Anexo 6. Punta ArenasGoogle Scholar
- Barrera-Oro ER, Casaux RJ (1998) Ecology of demersal fish species from Potter Cove. Ber Polarforsch 299:156–167Google Scholar
- Barrera-Oro E, Marschoff E, Casaux R (2000) Trends in relative abundance of fjord Notothenia rossii, Gobionotothen gibberifrons and Notothenia coriiceps at South Shetland Islands, after commercial fishing in the area. CCAMLR Sci 7:43–52Google Scholar
- Bertolin ML (2012) Análisis de las relaciones tróficas entre peces y vertebrados ictiófagos de las Islas Orcadas del Sur, Antártida: hacia el conocimiento integral del ecosistema y el manejo racional de los recursos. Doctoral dissertation, Facultad de Ciencias Naturales y Museo. La Plata, Buenos AiresGoogle Scholar
- Burger A, Piatt J (1990) Flexible time budgets in breeding common murres: buffers against variable prey abundance. Stud Avian Biol 14:71–83Google Scholar
- Croxall JP, Prince PA (1987) Seabirds as predators on marine resources, especially krill, at South Georgia. In: Croxall JP (ed) Seabirds: feeding ecology and role in marine ecosystems. Cambridge University Press, Cambridge, pp 347–368Google Scholar
- DeWitt HH, Heemstra PC, Gon O (1990) Nototheniidae. In: Gon O, Heemstra PC (eds) Fishes of the Southern Ocean. Grahamstown, South Africa, pp 279–331Google Scholar
- Green K, Burton H, Watts D (1995) Studies of the Weddell seals in the Vestfold Hills East Antarctica. ANARE Res Notes 93:1–64Google Scholar
- Kock K (1992) Antarctic fish and fisheries. Cambridge University Press, CambridgeGoogle Scholar
- Kock KH, Jones CD, Wilhelms S (2000) Biological characteristics of Antarctic fish stocks in the southern Scotia Arc region. CCAMLR Sci 7:1–41Google Scholar
- Rombolá E, Marschoff E, Coria N (2003) Comparative study of the effects of the late pack-ice break-off on chinstrap and Adélie penguins’ diet and reproductive success at Laurie Island, South Orkney Islands, Antarctica. Polar Biol 26:41–48Google Scholar
- Van Franeker JA, Williams R, Imber MJ and Wolff WJ (2001) Diet and foraging ecology of southern fulmar (Fulmarus glacialoides), Antarctic petrel Thalassoica antarctica, Cape petrel Daption capense and snow petrels Pagodroma nivea ssp on Ardery Island, Wilkes Land, Antarctica. Doctoral dissertation, University of Groningen, Alterra, TexelGoogle Scholar