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.

  • Source
    1 01/2014; Benemérita Universidad Autónoma de Puebla., ISBN: 9786074878097
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A review was undertaken of information relating to historic changes to the seabed (benthos) of Pelorus Sound (Te Hoiere). Significant changes appear to have occurred to the benthos of Pelorus Sound, including; loss of extensive intertidal and subtidal green-lipped mussel reefs, loss of biogenic habitats, and contingent changes to sediment structure. Factors most likely to have driven these changes are; over-fishing of shellfish stocks (dredging and hand-picking), contact fishing methods (shellfish dredging and finfish trawling), increased sedimentation from changing land-use over time, and ongoing aquaculture and forestry developments.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rationale Individual foraging behavior is an important variable of predators commonly studied at the population level. Some hammerhead shark species play a significant role in the marine ecosystem as top consumers. In this context, stable isotope analysis allows us to infer some ecological metrics and patterns that cannot usually be obtained using traditional methods. Methods We determined the isotopic composition (δ13C and δ15N values) of dorsal muscle and vertebrae of Sphyrna lewini and Sphyrna zygaena using a continuous-flow system consisting of an elemental analyzer combined with a Delta Plus XL mass spectrometer. Foraging variability by sex and by individual was inferred from the isotopic values. Results There were no significant differences in the isotopic values of muscle samples between sexes, but there were differences between species. The trophic niche breadth of the two species was similar and overlap was low. A low niche overlap was observed between S. lewini individual vertebrae. We found differences in the δ15N values of S. zygaena vertebrae, with lower values in the first group of samples. Conclusions Despite these hammerhead shark species inhabiting the same area, there was low trophic niche overlap between species and individuals, due to different individual foraging strategies, according to the carbon and nitrogen isotopic profiles obtained. The use of tissues that retain lifetime isotopic information is useful to complement studies on trophic ecology.
    Rapid Communications in Mass Spectrometry 03/2015; 29(9):821-829. DOI:10.1002/rcm.7169 · 2.64 Impact Factor

Full-text (4 Sources)

Available from
May 19, 2014