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Marine Ecology Progress Series

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MEPS 481:225-237 (2013)  -  DOI:

Apparent resource partitioning and trophic structure of large-bodied marine predators in a relatively pristine seagrass ecosystem

Michael R. Heithaus1,*,**, Jeremy J. Vaudo1,**, Sina Kreicker2, Craig A. Layman1, Michael Krützen2, Derek A. Burkholder1, Kirk Gastrich1, Cindy Bessey1, Robin Sarabia1, Kathryn Cameron1, Aaron Wirsing3, Jordan A. Thomson1, Meagan M. Dunphy-Daly4

1Marine Sciences Program, School of Environment, Arts and Society, Florida International University, 3000 NE 151st St., North Miami, Florida 33181, USA
2Evolutionary Genetics Group, Anthropological Institute & Museum, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
3School of Environmental and Forest Sciences, Box 352100, University of Washington, Seattle, Washington 98195, USA
4Duke University Marine Laboratory, Nicholas School of the Environment, 135 Duke Marine Lab Road, Beaufort, North Carolina 28516, USA
 *Email: **These authors contributed equally to this work

ABSTRACT: 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 sharks Negaprion 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.

KEY WORDS: Food webs · Predator–prey interactions · Stable isotope · Niche overlap · Elasmobranchs · Sharks · Cetacean · Trophic redundancy · Niche partitioning

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Cite this article as: Heithaus MR, Vaudo JJ, Kreicker S, Layman CA and others (2013) Apparent resource partitioning and trophic structure of large-bodied marine predators in a relatively pristine seagrass ecosystem. Mar Ecol Prog Ser 481:225-237.

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