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Apparent Resource Partitioning and Trophic Structure of Large-Bodied Marine Predators in a Relatively Pristine Seagrass Ecosystem
Marine Ecology Progress Series
  • Michael Heithaus, Florida International University
  • Jeremy Vaudo, Nova Southeastern University
  • Sina Kreicker, University of Zurich
  • Craig A. Layman, Florida International University
  • Michael Krutzen, University of Zurich
  • Derek A. Burkholder, Florida International University
  • Kirk Gastrich, Florida International University
  • Cindy Bessey, Florida International University
  • Robin Sarabia, Florida International University
  • Kathryn Cameron, Florida International University
  • Aaron Wirsing, University of Washington - Seattle Campus
  • Jordan A. Thomson, Florida International University
  • Meagan M. Dunphy-Daly, Duke University Marine Laboratory
Document Type
Publication Date
  • Food Webs,
  • Predator-Prey Interactions,
  • Stable Isotope,
  • Niche Overlap,
  • Elasmobranchs,
  • Sharks,
  • Cetacean,
  • Trophic Redundancy,
  • Niche Partitioning

Large predators often play important roles in structuring marine communities. To understand the role that these predators play in ecosystems, it is crucial to have knowledge of their interactions and the degree to which their trophic roles are complementary or redundant among species. We used stable isotope analysis to examine the isotopic niche overlap of dolphins Tursiops cf. aduncus, large sharks (>1.5 m total length), and smaller elasmobranchs (sharks and batoids) in the relatively pristine seagrass community of Shark Bay, Australia. Dolphins and large sharks differed in their mean isotopic values for δ13C and δ15N, and each group occupied a relatively unique area in isotopic niche space. The standard ellipse areas (SEAc; based on bivariate standard deviations) of dolphins, large sharks, small sharks, and rays did not overlap. Tiger sharks Galeocerdo cuvier had the highest δ15N values, although the mean δ13C and δ15N values of pigeye sharks Carcharhinus amboinensis were similar. Other large sharks (e.g. sicklefin lemon sharksNegaprion acutidens and sandbar sharks Carcharhinus plumbeus) and dolphins appeared to feed at slightly lower trophic levels than tiger sharks. In this seagrass-dominated ecosystem, seagrass-derived carbon appears to be more important for elasmobranchs than it is for dolphins. Habitat use patterns did not correlate well with the sources of productivity supporting diets, suggesting that habitat use patterns may not necessarily be reflective of the resource pools supporting a population and highlights the importance of detailed datasets on trophic interactions for elucidating the ecological roles of predators.

Citation Information
Michael Heithaus, Jeremy Vaudo, Sina Kreicker, Craig A. Layman, et al.. "Apparent Resource Partitioning and Trophic Structure of Large-Bodied Marine Predators in a Relatively Pristine Seagrass Ecosystem" Marine Ecology Progress Series Vol. 481 (2013) p. 225 - 237
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