Thesis
Broad-scale movement and diet of the tiger shark (Galeocerdo cuvier) – understanding the biology and ecology of an apex predator off the east coast of Australia
University of the Sunshine Coast, Queensland
Master of Science, University of the Sunshine Coast, Queensland
2025
DOI:
https://doi.org/10.25907/00981
Abstract
The study of migratory marine predators is often difficult due to their large home ranges including remote reef and deep-water ecosystems. As such, studies with adequate representative samples to make inferences about their biology and ecology have been limited and require extensive sampling effort to achieve. Successful studies have ascertained that these predators play a critical role in ecosystem service and function, particularly those atop the trophic hierarchy. For example, marine apex predators like the tiger shark (Galeocerdo cuvier) play a critical role shaping the tropic structure of many marine communities but remain challenging to study due to their large size at maturity, extensive home ranges, and variable breeding cycles. Over the past 10 years there have been few studies that have tracked the movement of tiger sharks and delved into related biology and ecology, particularly off the east coast of Australia. Notably, the few regional movement studies conducted have been limited to more coastally attached juveniles and mature females, focusing on size-based movement patterns. Few mature males have been captured, and therefore there is little understanding if sexual segregation is occurring in this species. Herein, to compliment the current tracking literature on tiger sharks for this region, I deployed pop-up archival (PSATs) and smart position SPLASH tags on mature male tiger sharks off QLD and NSW to ascertain if movements and preferred habitat differed from what was reported previously in juveniles and mature females. The movement of mature male tiger sharks is requisite for a comprehensive understanding of species movement, as well as for the recognition of potentially biologically important dispersal, migration, or hotspot regions of activity. Despite some individual differences, mature male tiger sharks generally migrate in similar fashion to mature females with diverging spaces use in deep off-shelf waters and difference core high-use areas, suggesting a moderate degree of regional sexualsegregation. These results have implications for the future management of these stocks, including annual game fishing exploitation in offshore waters, and coastal lethal shark management programs related to bather protection. Complementing our expanded understanding of species movement, we investigated the dietary composition of tiger sharks in this region for the first time through stomach content analysis conducted spatio-temporally from 1997-2025. Tiger shark ontogenetic shifts were identified, along with prevalent prey-switching behaviour that demonstrates the generalist feeding nature of the species as they move from warm temperate to tropical locations across QLD and NSW. These results indicate that tiger sharks actively alter their diet to locally available resources throughout their migrations. As such, this ability should aid in species adaptability and response to a range extension as climate change induced warming temperatures drive poleward expansion and prey redistribution.
Details
- Title
- Broad-scale movement and diet of the tiger shark (Galeocerdo cuvier) – understanding the biology and ecology of an apex predator off the east coast of Australia
- Authors
- Alexandra I Ikpe - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
- Contributors
- Bonnie Holmes (Principal Supervisor) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringAlexis L Levengood (General Contributor) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringJohan Gustafson (Consultant Supervisor) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringPaul A Butcher (Consultant Supervisor) - Southern Cross University
- Awarding institution
- University of the Sunshine Coast, Queensland
- Degree awarded
- Master of Science
- Publisher
- University of the Sunshine Coast, Queensland
- DOI
- 10.25907/00981
- Organisation Unit
- School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 991184845402621
- Output Type
- Thesis
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