Alexandra ‘PJ’ Ikpe (PhD Student- Holmes Lab, School of Science, Tech, and Engineering, University of Sunshine Coast)

I began my PhD journey in 2022, studying the movement and diet of tiger sharks (Galeocerdo cuvier) along the eastern coast of Australia. I was able to acquire multiple tags and diet analysis tools to attempt addressing gaps in scientific knowledge about this species. The overall goal of my research is to better understand the movement patterns of this species and identify the underlying behaviours that drive them. This information is the foundation on which to then assess the ecological role of tiger sharks along the eastern coast of Australia.

The donation of external satellite tags from the New South Wales Department of Primary Industries jump started my research and meant that I was able to immediately start my fieldwork deploying satellite tags on mature male tiger sharks. This allowed for two deployments during my first two stints of time in the field and, with the assistance of an experienced crew, I was able to double tag two male tiger sharks in Hervey Bay and Coffs Harbour in 2022. Since this time, I have had assistance from the Shark SMART program contractors who have been able to single tag multiple males for me. The highlight of this research is the double deployment tagging of two satellite tags that, when combined, can provide incredibly comprehensive positioning datasets.

ESA’s recent contribution to my project through the Holsworth Wildlife Research Endowment, has bolstered my ability to get in the field this upcoming season, and hopefully have multiple opportunities to double deploy our multiple tags, and gather that elusive comprehensive movement data. For those unfamiliar with this type of work, satellite tags track animal movement in different contexts. The tags at my disposal are PSATs which capture movement at depth, and SPLASH which capture more precise positioning data at the surface, and both record environmental variables.

I am targeting mature male tiger sharks as a review of the current literature shows a sex-bias towards females and juveniles in tracking studies. As understanding species’ ecology and biology requires an understanding of movement for all life stages of a species, including sex differences, focusing on this segment of the population for tagging will provide a comparable dataset for what is already published. The potential to discover mating grounds, sex-specific migratory routes, or male ‘hangout’ spots is exciting! Initial data from these tags has revealed interesting movement patterns, especially in comparing sub-adult and fully mature males.

Diet analysis is another key part of my research, as tiger sharks’ movements are often prey-driven. Examining stomach contents for prey composition and preferences will offer valuable insight into both small-scale foraging behaviour and broader movement patterns. I will be conducting stomach content dissections alongside cloacal swabs for eDNA sequencing and metabarcoding, which allows for precise species identification—an exciting, emerging method in ecological research. Combining the findings from both areas of research should offer interesting insight into the species.

Heading into my last year I am excited to get some last-minute fieldwork in to increase my dataset, analyse all the information I have collected, and garner some insight into such an amazing apex predator migrating along the eastern coast.

This work could not be completed without the help of various individuals and parties. I’d like to acknowledge the support of the University of the Sunshine Coast, NSW DPI, QLD DAF, NSW Shark SMART, The Shark Foundation, Australian Wildlife Society, Marine Biological Association, Australian Society for Fish Biology, Oceania Chondrichthyan Society, and of course the Ecological Society of Australia.

The work I do is on borrowed land. I would like to acknowledge the Traditional Custodians of the lands and waters on which I work, spanning the shores and marine environments of Queensland and New South Wales. I pay my respects to the Elders of these regions, past, present, and emerging, and recognize their enduring connection to these waterways, coasts, and oceans. I honour the cultural, spiritual, and ecological knowledge that First Nations peoples have maintained for thousands of generations, and I acknowledge the custodianship of the diverse Aboriginal and Torres Strait Islander communities who continue to care for and protect these waters.

Image credits:

Top left: Excited about a successful tagging of a 3.78-m (total length) tiger shark in Coffs Harbor with both a PSAT and SPLASH in December 2022 with the NSW Shark Management Program research team.

Bottom right: Attaching a PSAT onto a 2.7-m (total length) tiger shark in Hervey Bay, QLD with DAF researcher Matthew McMillan in October 2022.

Alexandra Ikpe was recently awarded a Holsworth Wildlife Research Endowment grant to help support this research.