Author ORCID Identifier

https://orcid.org/

0000-0003-2129-5664 : Teah Burke

Standing

Graduate (Masters)

Type of Proposal

Oral Research Presentation

Faculty

Faculty of Science

Faculty Sponsor

Dr. Nigel Hussey

Abstract/Description of Original Work

For marine top predators which are undergoing systematic population declines, identifying intraspecific population variation in diet and movement of a species has important implications for understanding their ecological effects on community structure. White sharks (Carcharodon carcharias) are an apex predator found throughout temperate to tropical ocean regions. At the global scale, geographically isolated white shark populations have been shown to demonstrate unique behaviours from intra individual variation to distinct subpopulation movements whereby two groups of individuals reside in separate coastal regions. In Australia two discrete subpopulations of white sharks have been proposed based on satellite/acoustic tagging and population genetics, but given tagging studies are generally short term, data are limited to characterize the extent of ontogenetic divergence. To quantify subpopulation diet-habitat behaviour of white sharks, stable isotope profiles (δ15N and δ13C) conserved in vertebrae (n=82) were used to create retrospective ontogenetic trophic-habitat fingerprints for individuals sampled east and west of the Bass Strait. Preliminary results demonstrate distinct isotopic separation between sharks sampled in eastern (13.99+/- 0.78 δ15N, n=42) and western (12.47 +/- 1.17 δ15N, n=27) regions, but both populations showed strong oscillatory trends equating to similar niche variation. Data further indicate mature females could be occupying the same habitat during gestation, juvenile phases occupy distinct coastal regions and as animals mature, habitat occupied by the two sub populations converges. Elucidating lifelong feeding and movement patterns will allow informed decisions for regional management plans.

Availability

March 29 - April 1 available 12-3

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Retrospective stable isotope analysis reveals ontogenetic population subdivision among white sharks (Carcharodon carcharias) from Australia.

For marine top predators which are undergoing systematic population declines, identifying intraspecific population variation in diet and movement of a species has important implications for understanding their ecological effects on community structure. White sharks (Carcharodon carcharias) are an apex predator found throughout temperate to tropical ocean regions. At the global scale, geographically isolated white shark populations have been shown to demonstrate unique behaviours from intra individual variation to distinct subpopulation movements whereby two groups of individuals reside in separate coastal regions. In Australia two discrete subpopulations of white sharks have been proposed based on satellite/acoustic tagging and population genetics, but given tagging studies are generally short term, data are limited to characterize the extent of ontogenetic divergence. To quantify subpopulation diet-habitat behaviour of white sharks, stable isotope profiles (δ15N and δ13C) conserved in vertebrae (n=82) were used to create retrospective ontogenetic trophic-habitat fingerprints for individuals sampled east and west of the Bass Strait. Preliminary results demonstrate distinct isotopic separation between sharks sampled in eastern (13.99+/- 0.78 δ15N, n=42) and western (12.47 +/- 1.17 δ15N, n=27) regions, but both populations showed strong oscillatory trends equating to similar niche variation. Data further indicate mature females could be occupying the same habitat during gestation, juvenile phases occupy distinct coastal regions and as animals mature, habitat occupied by the two sub populations converges. Elucidating lifelong feeding and movement patterns will allow informed decisions for regional management plans.