Coral Reefs

, Volume 35, Issue 2, pp 459–472 | Cite as

Reassessing the trophic role of reef sharks as apex predators on coral reefs

  • Ashley J. FrischEmail author
  • Matthew Ireland
  • Justin R. Rizzari
  • Oona M. Lönnstedt
  • Katalin A. Magnenat
  • Christopher E. Mirbach
  • Jean-Paul A. Hobbs


Apex predators often have strong top-down effects on ecosystem components and are therefore a priority for conservation and management. Due to their large size and conspicuous predatory behaviour, reef sharks are typically assumed to be apex predators, but their functional role is yet to be confirmed. In this study, we used stomach contents and stable isotopes to estimate diet, trophic position and carbon sources for three common species of reef shark (Triaenodon obesus, Carcharhinus melanopterus and C. amblyrhynchos) from the Great Barrier Reef (Australia) and evaluated their assumed functional role as apex predators by qualitative and quantitative comparisons with other sharks and large predatory fishes. We found that reef sharks do not occupy the apex of coral reef food chains, but instead have functional roles similar to those of large predatory fishes such as snappers, emperors and groupers, which are typically regarded as high-level mesopredators. We hypothesise that a degree of functional redundancy exists within this guild of predators, potentially explaining why shark-induced trophic cascades are rare or subtle in coral reef ecosystems. We also found that reef sharks participate in multiple food webs (pelagic and benthic) and are sustained by multiple sources of primary production. We conclude that large conspicuous predators, be they elasmobranchs or any other taxon, should not axiomatically be regarded as apex predators without thorough analysis of their diet. In the case of reef sharks, our dietary analyses suggest they should be reassigned to an alternative trophic group such as high-level mesopredators. This change will facilitate improved understanding of how reef communities function and how removal of predators (e.g., via fishing) might affect ecosystem properties.


Elasmobranch Food web Stable isotope analysis Top-down control Trophic ecology 



We thank R. Baker, B. Bergseth, J. Frisch, S. Frisch and B. Bauerle for technical assistance and N. Hussey for reviewing an earlier draft of the manuscript. Funding was provided by a Lizard Island Research Station John and Laurine Proud Fellowship (AJF) and a grant from the Save Our Seas Foundation (JRR). This research was undertaken with permission from the GBR Marine Park Authority (permit number G12/34941.1), Fisheries Queensland (permit number 152940) and the James Cook University Animal Experimentation Ethics Committee (approval number A1742).

Supplementary material

338_2016_1415_MOESM1_ESM.tif (11.9 mb)
Fig. S1 Relationship between δ13C (a–c), δ15N (d–f) and total length in (a, d) Triaenodon obesus, (b, e) Carcharhinus melanopterus and (c, f) C. amblyrhynchos. Other species are not included due to small sample sizes. Statistically significant relationships are depicted by regression lines (TIFF 12221 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Ashley J. Frisch
    • 1
    Email author
  • Matthew Ireland
    • 2
  • Justin R. Rizzari
    • 1
    • 2
  • Oona M. Lönnstedt
    • 2
    • 3
  • Katalin A. Magnenat
    • 2
  • Christopher E. Mirbach
    • 2
  • Jean-Paul A. Hobbs
    • 4
  1. 1.Australian Research Council Centre of Excellence for Coral Reef StudiesJames Cook UniversityTownsvilleAustralia
  2. 2.College of Marine and Environmental SciencesJames Cook UniversityTownsvilleAustralia
  3. 3.Department of Ecology and Genetics, LimnologyUppsala UniversityUppsalaSweden
  4. 4.Department of Environment and AgricultureCurtin UniversityPerthAustralia

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