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Marine Ecology Progress Series

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MEPS 526:169-181 (2015)  -  DOI:

Prey-field use by a Southern Ocean top predator: enhanced understanding using integrated datasets

Merel Bedford1,2,*, Jessica Melbourne-Thomas2,3, Stuart Corney2, Toby Jarvis3,4, Natalie Kelly3,5, Andrew Constable2,3

1Institute for Marine and Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7000, Australia
2Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, Tasmania 7000, Australia
3Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
4Echoview Software Pty. Ltd., GPO Box 1327, Hobart, Tasmania 7001, Australia
5CSIRO Computational Informatics and Wealth from Oceans Flagship, GPO Box 1538, Hobart, Tasmania 7001, Australia
*Corresponding author:

ABSTRACT: An important challenge for understanding and managing marine ecosystems is determining the relationship between the distributions of prey species and the foraging of top predators. We examined the diet and foraging dynamics of breeding macaroni penguins Eudyptes chrysolophus from sub-Antarctic Heard Island and related these to prey distributions derived from active-acoustics and net-derived data in the foraging zone of the penguins. Consistent with previous findings, we found that penguin diets changed between the guard and crèche stages of the breeding cycle and that this change in diet corresponded with a switch from short foraging trips in the guard stage to significantly longer, offshore foraging trips in the crèche stage. We related these differences in diet and foraging to characteristics of the prey field—specifically, a relatively uniform distribution of krill over the shelf and in deeper, offshore waters, compared with an increasing abundance of fish further from shore. We developed a simple dynamic energy budget for macaroni penguins to explore whether targeting fish during the crèche stage was an energetically favourable strategy. Finally, we extrapolated our energy budget to estimate prey consumption at the colony scale as previous work has suggested that depletion near breeding colonies could contribute to prey switching. We found that prey switching during the crèche stage was energetically favourable and was most likely related to a reduction in foraging constraints, rather than prey depletion. This study shows the value of integrating data sets to address questions surrounding variation in diet and the use of alternative prey by marine predators.

KEY WORDS: Prey-specific foraging · Prey switching · Prey-field characteristics · Prey depletion · Ecosystem function · Active-acoustics · Macaroni penguins

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Cite this article as: Bedford M, Melbourne-Thomas J, Corney S, Jarvis T, Kelly N, Constable A (2015) Prey-field use by a Southern Ocean top predator: enhanced understanding using integrated datasets. Mar Ecol Prog Ser 526:169-181.

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