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Critical assessment and ramifications of a purported marine trophic cascade

February 15, 2016

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decisions.

Publication Year 2016
Title Critical assessment and ramifications of a purported marine trophic cascade
DOI 10.1038/srep20970
Authors R. Dean Grubbs, John K Carlson, Jason G. Romine, Tobey H Curtis, W. David McElroy, Camilla T McCandless, Charles F Cotton, John A. Musick
Publication Type Article
Publication Subtype Journal Article
Series Title Scientific Reports
Index ID 70168660
Record Source USGS Publications Warehouse
USGS Organization Western Fisheries Research Center