Diet overlap among top predators at the South Orkney Islands, Antarctica.

BERTOLIN M.; CASAUX R.

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2019 vol. 42 p. 371 - 383

0722-4060

AbstractIn order to understand interspecifictrophic relationships among top predators, we analyzed diet information on 11bird and seal species collected from the 1996 to the 2000 austral summer atSouth Orkney Islands. Overall, the diet of most of the predators was similar tothe reported for other Antarctic areas, which was mainly composed by krill,fish or penguins. The re-occurrence of prey among predators ranged from 25.3 to36.7 and the preys that most re-occurred were fish, krill and squids. There-occurrence of fish among predator pairs was low and ranged from 8.1 to 28.1,being the species that most re-occurred the nototheniids Gobionotothen gibberifrons, Nototheniopsnudifrons and Nototheniops nybelini,and the myctophid Electrona antarctica.Most of the predator species pairs presented low values of prey overlap and thehighest values were observed between Chinstrap and Adélie penguins. Regarding fish,most of the predator pairs exhibited high values of prey overlap across all thepredator pairs. The diet of some predators, mainly those capable to forage ondemersal or water column prey, varied seasonally. Such variation seems to beexplained by fluctuations in krill availability; in years of scarce krillabundance those predators diversified their diet by increasing the consumptionof littoral fish, which results in higher values of prey overlap among them. Theanalysis of the information suggest the recovery of the stocks of G. gibberifrons around the South Orkney Islandsand highlight the importance to draw the attention on the increase theinterspecific food competition among predators under scenarios of decreasingkrill availability.