title: Critical assessment and ramifications of a purported marine trophic cascade.
abstract: 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.
authors.affiliation: Florida State University Coastal and Marine Laboratory, 3618 Hwy 98, St. Teresa, FL 32358, USA.
authors.forename: R Dean
authors.initials: RD
authors.lastname: Grubbs
authors.affiliation: NOAA/National Marine Fisheries Service, Southeast Fisheries Science Center, 3500 Delwood Beach Road, Panama City, FL 32408, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Carlson
authors.affiliation: U.S. Geological Survey, Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA 98605, USA.
authors.forename: Jason G
authors.initials: JG
authors.lastname: Romine
authors.affiliation: NOAA/National Marine Fisheries Service, Greater Atlantic Regional Fisheries Office, 55 Great Republic Drive, Gloucester, Massachusetts, 01930, USA.
authors.forename: Tobey H
authors.initials: TH
authors.lastname: Curtis
authors.affiliation: NOAA/National Marine Fisheries Service, Northeast Fisheries Science Center, 166 Water Street, Woods Hole, MA 02543, USA.
authors.forename: W David
authors.initials: WD
authors.lastname: McElroy
authors.affiliation: NOAA/National Marine Fisheries Service, Northeast Fisheries Science Center, 28 Tarzwell Drive, Narragansett, RI 02882, USA.
authors.forename: Camilla T
authors.initials: CT
authors.lastname: McCandless
authors.affiliation: Florida State University Coastal and Marine Laboratory, 3618 Hwy 98, St. Teresa, FL 32358, USA.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Cotton
authors.affiliation: Virginia Institute of Marine Science, 1208 Greate Rd., Gloucester Point, VA 32062, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Musick
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D049872:Bivalvia / Q000502:physiology; D017753:Ecosystem; D005247:Feeding Behavior; D020387:Food Chain; D011157:Population Dynamics; D011235:Predatory Behavior; D012098:Reproduction; D012754:Sharks / Q000502:physiology; D012860:Skates, Fish / Q000502:physiology*