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

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 a...

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Bibliographic Details
Published in:Journal of fish biology 2019-12, Vol.95 (6), p.1430-1440
Main Authors: Raoult, Vincent, Broadhurst, Matt K., Peddemors, Vic M., Williamson, Jane E., Gaston, Troy F.
Format: Article
Language:English
Subjects:
34S
Animals
Aquatic crustaceans
Australia
Benthos
Carbon Isotopes - analysis
Cephalopods
Coastal ecosystems
Conspecifics
Crustaceans
Diet
Diet - veterinary
ecological niche
Ecosystem
Food Chain
Food chains
Food webs
Male
Marine fishes
MixSIAR
Muscles
Nitrogen Isotopes - analysis
Ontogeny
Predators
Resources
Sharks
Sphyrna mokarran
Spine
Spine - chemistry
Stable isotopes
sulphur
Summer
Trajectories
Trophic levels
Vertebrae
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Summary: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.
ISSN:0022-1112
1095-8649
DOI:10.1111/jfb.14160