Teah Burke, MSc
Population Structure, Ecological Role, and Life History of Australian White Sharks (Carcharodon carcharias)
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.
During my MSc research at the University of Windsor, I explored the use of stable isotope analysis on vertebrae to study these key ecological characteristics in Australian white sharks throughout ontogeny.
Vertebrae are really unique to work with. They grow like rings on a tree trunk, and can be sampled sequentially to investigate trends over an individuals lifetime. Whereas other tissue types like blood, liver, or muscle might only show you a snapshot (weeks to months) of an individuals life when using them for stable isotope analysis.
In the first chapter of my MSc, I investigated the population structure of white sharks in Australia. Two discrete subpopulations of white sharks (an eastern and a southwest subpopulation) have been proposed based on genetics and limited movement across Bass Strait. However, recent evidence has been challenging this assumption. In this chapter we aimed to characterise the extent of ontogenetic divergence in resource-habitat behaviour of white sharks from both regions. We found evidence for an ecological two population model, with distinct isotopic separation between juvenile-subadult white sharks sampled east and southwest of Bass Strait.
Birth
Death
In the second chapter of my MSc, we used serial sampled carbon isotope profiles (δ13C) in vertebrae as a novel technique to provide an additional metric for estimating age given individuals undertake systematic seasonal movements between two locations that are isotopically distinct. Using a collection of eastern Australia white shark vertebrae, oscillations in δ13C profiles attributed to annual seasonal movements of immature white sharks from Corner Inlet, Victoria to southern Queensland were counted using standardized thresholds to assign age. Age estimates for immature white sharks based on isotopically inferred annual movements were similar to those derived from traditional vertebral counts, contrasting the slower growth seen in bomb radiocarbon (14C).
Burke, T.G., Huveneers, C., Meyer, L., Hollins, J.P.W., Loseto, L., Werry, J., Hussey, N.E. (2025). Evidence for an ecological two-population model for white sharks (Carcharodon carcharias) in Australian waters. Wildlife Research, 52, WR24132. (doi:10.1071/WR24132).