Spatial and temporal variability in foraging patterns of krill predators at Signy Island and South Georgia

While constrained by the requirement to feed their young, land-based marine predators act as central-placed foragers with movements between their breeding colony and their food resource. In a system where the distribution and abundance of prey is highly variable, foraging behaviour must be highly adaptable. In this paper we consider the behaviour of seal and seabird krill-dependent predators foraging to provision their young and to feed themselves. We examine data from a variety of species to determine whether foraging is more intense close to the colony, or whether it is more widely distributed within the wider potential foraging range.
During the breeding season, parents are able to forage for increasingly long periods and over much greater areas as their offspring develop. Their potential foraging range increases as the breeding season advances, potentially affecting local levels of predation. We look to determine whether foraging areas are different at different times of the breeding season; we also look to see whether differences are apparent between years.
We use this information about where and when marine predators forage to identify candidate ‘small-scale management units’, these are areas where potential resource competition could exist between krill-dependent predators and the commercial fishery for Antarctic krill, Euphausia superba. The criteria used to identify these units are described as an example of how they could be used in other locations where the fishery operates.