Date of Award

12-19-2023

Publication Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

Supervisor

Nigel Hussey

Rights

info:eu-repo/semantics/embargoedAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

At the global scale top predators play an important role in regulating food webs through top-down control. As a result of anthropogenic- and climate-related declines in predator abundance, new challenges have arisen on how to effectively manage threatened populations and obtain the necessary information to facilitate their recovery. A comprehensive understanding of key ecological characteristics such as population structure, resource use, and life history are fundamental to designing effective conservation and management strategies. In this thesis, I explored the use of stable isotope analysis on vertebrae to study these key ecological characteristics in Australian white sharks throughout ontogeny. My findings in Chapter two suggest mature females are occupying similar habitats during gestation, juvenile and subadult white sharks occupy distinct coastal regions East and West of the Bass Strait and as animals mature, habitat occupied by the two subpopulations potentially converges. Within the juvenile/subadult life stage, niche width increased from size class one (small juveniles) to two (large juveniles and subadults) for sharks in the East, but not in the West. While isotopic niche overlap was high within both subpopulations, individual sharks were highly specialized. We propose white sharks are ‘apparent specialists’, i.e., they appear to be specialists when considering the diverse prey consumed by the entire population, but individuals may still have a generalist diet composed of a subset of resources available to the population. In Chapter three, age estimates based on novel indirect inference from ontogenetic stable isotope profiles tied to latitudinal isotopic gradients combined with telemetry identified faster growth in juveniles than currently accepted based on bomb radiocarbon. These data further support the two-population model for Australian white sharks and suggest separate management units may be required for the East and West populations in addition to tailoring management strategies to account for variation and fast growth in the initial life stages of white sharks.

Available for download on Tuesday, February 11, 2025

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