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Science 30 March 2007:
Vol. 315. no. 5820, pp. 1846 - 1850
DOI: 10.1126/science.1138657
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Reports

Cascading Effects of the Loss of Apex Predatory Sharks from a Coastal Ocean

Ransom A. Myers,1 Julia K. Baum,1* Travis D. Shepherd,1 Sean P. Powers,2 Charles H. Peterson3*

Impacts of chronic overfishing are evident in population depletions worldwide, yet indirect ecosystem effects induced by predator removal from oceanic food webs remain unpredictable. As abundances of all 11 great sharks that consume other elasmobranchs (rays, skates, and small sharks) fell over the past 35 years, 12 of 14 of these prey species increased in coastal northwest Atlantic ecosystems. Effects of this community restructuring have cascaded downward from the cownose ray, whose enhanced predation on its bay scallop prey was sufficient to terminate a century-long scallop fishery. Analogous top-down effects may be a predictable consequence of eliminating entire functional groups of predators.

1 Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada.
2 Department of Marine Sciences, University of South Alabama, and Dauphin Island Sea Lab, 101 Bienville Boulevard, Dauphin Island, AL 36528, USA.
3 Institute of Marine Sciences, University of North Carolina (UNC) at Chapel Hill, Morehead City, NC 28557, USA.

* To whom correspondence should be addressed. E-mail: baum{at}mscs.dal.ca (J.K.B.); cpeters{at}email.unc.edu (C.H.P.)

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