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

Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada.
Science (Impact Factor: 31.48). 03/2007; 315(5820):1846-50. DOI: 10.1126/science.1138657
Source: PubMed

ABSTRACT 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.

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Available from: Julia K Baum, Jul 31, 2015
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    • "Ocean acidification and temperature stress from climate change are expected to further reduce the resilience of reefs worldwide (Hoegh-Guldberg et al. 2007). Tipping points have also been tied to single, intense stressors, most often intense harvest of a key predator (Estes et al. 1998, 2011, Myers et al. 2007, Baum and Worm 2009, Ferretti et al. 2010). Otter removal is the singular cause of rocky reef shifts from kelp forest to urchin barrens in the northeast Pacific (Estes and Palmisano 1974, Estes and Duggins 1995, Dean et al. 2000). "
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    • "Recent studies have revealed very high levels of marine litter in the Mediterranean (Pham et al., 2014; Suaria and Aliani, 2014), and impacts of coastal activities, especially with regard to litter distribution and biodiversity loss, are likely to be high. Severely declining numbers and losses of key species have been documented for species including fish and shark and especially predatory species due to human impact activities (Myers et al., 2007). "
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    • "Usually they are large-bodied vertebrates that can move over large areas, thus interacting with different communities. Most importantly, apex predators are pivotal in maintaining ecosystem stability, and their elimination can produce cascading effects throughout entire food webs (Myers et al. 2007; Terborgh et al. 2010; Estes et al. 2011). Accordingly , the extinction of C. megalodon potentially affected the structure and function of ancient ecosystems (Pimiento and Clements 2014). "
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