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Science 22 June 2007:
Vol. 316. no. 5832, pp. 1743 - 1746
DOI: 10.1126/science.1141412
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Reports

Culling Prey Promotes Predator Recovery—Alternative States in a Whole-Lake Experiment

Lennart Persson,1* Per-Arne Amundsen,2 André M. De Roos,3 Anders Klemetsen,2 Rune Knudsen,2 Raul Primicerio2

Many top-predator fish stocks in both freshwater and marine systems have collapsed as a result of overharvesting. Consequently, some of these communities have shifted into seemingly irreversible new states. We showed, for predators feeding on prey that exhibit food-dependent growth, that culling of fish prey may promote predator recovery. We removed old stunted individuals of a prey-fish species in a large, low-productive lake, which caused an increase in the availability of small-sized prey and allowed the predator to recover. The shift in community state has been sustained for more than 15 years after the cull ended and represents an experimental demonstration of an alternative stable state in a large-scale field system. Because most animals exhibit food-dependent growth, shifts into alternative stable states resulting from overcompensating prey growth may be common in nature and may require counterintuitive management strategies.

1 Department of Ecology and Environmental Science, Umeå University, S-901 87 Umeå, Sweden.
2 Department of Aquatic BioSciences, Norwegian College of Fishery Science, University of Tromsø, N-9037 Norway.
3 Institute of Biodiversity and Ecosystems, University of Amsterdam, Post Office Box 94084, NL-1090 GB Amsterdam, Netherlands.

* To whom correspondence should be addressed. E-mail: lennart.persson{at}emg.umu.se

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