Resource use of great hammerhead sharks (Sphyrna mokarran) off eastern Australia

Vincent Raoult*, Matt K. Broadhurst, Vic M. Peddemors, Jane E. Williamson, Troy F. Gaston

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    25 Citations (Scopus)

    Abstract

    Great hammerhead sharks Sphyrna mokarran are the largest member of Sphyrnidae, yet the roles of these large sharks in the food webs of coastal ecosystems are still poorly understood. Here we obtained samples of muscle, liver and vertebrae from large S. mokarran (234–383 cm total length; LT) caught as by-catch off eastern Australia and used stable-isotope analyses of δ15N, δ13C and δ34S to infer their resource use and any associated ontogenetic patterns. The results indicated large S. mokarran are apex predators primarily relying on other sharks and rays for their diet, with a preference for benthic resources such as Australian cownose rays Rhinoperon neglecta during the austral summer. Teleosts, cephalopods and crustaceans were not significant components of S. mokarran diets, though some conspecifics appeared to rely on more diverse resources over the austral summer. Ontogenetic shifts in resource use were detected but trajectories of the increases in trophic level varied among individuals. Most S. mokarran had non-linear trajectories in ontogenetic resource-use shifts implying size was not the main explanatory factor. Stable isotope values of δ13C and δ34S in muscle suggest S. mokarran span coastal, pelagic and benthic food webs in eastern Australia.

    Original languageEnglish
    Pages (from-to)1430-1440
    Number of pages11
    JournalJournal of Fish Biology
    Volume95
    Issue number6
    Early online date15 Oct 2019
    DOIs
    Publication statusPublished - Dec 2019

    Keywords

    • ³⁴S
    • diet
    • ecological niche
    • MixSIAR
    • stable isotopes
    • sulphur
    • vertebrae

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