ESR 55:247-259 (2024)  -  DOI: https://doi.org/10.3354/esr01368

ABSTRACT: Assessing the trophic relationships among sympatric marine predators is crucial for ecosystem and fisheries management. This study used carbon and nitrogen stable isotope analysis to elucidate resource use and sharing of dusky Carcharhinus obscurus, tiger Galeocerdo cuvier and white Carcharodon carcharias sharks in eastern Australia. The individuals included in the dataset had similar size ranges (148-400 cm total length [TL]) and migratory movements, meaning they could be used to compare patterns in resource use. Using a Bayesian inference framework, we quantify the isotopic niche of each species and estimate niche overlap to compare their roles in this ecosystem. Tiger sharks had the largest isotopic niche (1.1 ‰²), followed by dusky sharks (0.9 ‰²). The isotopic niche of white sharks is substantially smaller (0.5 ‰²), suggesting these sharks are less of a generalist predator than dusky and tiger sharks. Most white shark niches overlapped with dusky and tiger sharks (84 and 72%, respectively), indicating white sharks use resources with similar isotopic values. Sex did not influence isotopic values, and weak significant relationships existed between TL and δ¹⁵N values in tiger sharks. Given the smaller isotopic niche and associated specialised role of white sharks <400 cm TL, this species may be more vulnerable to food web perturbations than generalist tiger and dusky sharks. This study gives new insight into the trophic interactions of these co-occurring shark species in eastern Australia and is crucial for understanding the ecological role of these predators required for sound ecosystem management.

KEY WORDS: Foraging ecology · Resource sharing · Marine predators · Isotopic niche

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Cite this article as: Lipscombe RS, Raoult V, Butcher PA (2024) Top predators, shared prey: isotopic niche dynamics and trophic interactions among dusky, tiger and white sharks. Endang Species Res 55:247-259. https://doi.org/10.3354/esr01368 Export citation Share:    Facebook - - linkedIn