A new study has revealed that whale sharks are utilising both natural underwater features and artificial structures like offshore oil and gas platforms as migratory “stepping stones” during their long-distance journeys.
The research, conducted by scientists from the Australian Institute of Marine Science (AIMS) and The University of Western Australia (UWA), analysed satellite tracking data from 78 whale sharks tagged over a 14-year period at Ningaloo Reef and Shark Bay off the Western Australian coast.
Lead author Ben D’Antonio, a PhD candidate from the AIMS@UWA program, explained that the study mapped whale shark movements across the eastern Indian Ocean and the North West Shelf, an area known for its numerous oil and gas platforms.
“Whale sharks travel huge distances across the oceans, and our study illustrates that they tend to use undersea pinnacles and sea mounts as stepping stones on these journeys because the currents that flow around these features help to enhance food availability like plankton,” D’Antonio said.
Interestingly, the research found that while natural features like seamounts and pinnacles can span tens of kilometres, the much smaller oil and gas platforms could provide similar levels of prey availability.
This is partly due to plankton being attracted to the artificial lights on these structures.
The study’s findings may have significant implications for the decommissioning of oil and gas platforms.
D’Antonio noted that removing these platforms at the end of their productive life could disrupt seascape connectivity by eliminating important migratory links for whale sharks.
However, the research also highlighted potential risks associated with these artificial structures.
Dr Luciana Ferreira, an AIMS scientist and co-author of the study, pointed out that whale sharks face threats from ship strikes by service vessels and pollutants from discharges and spills around oil and gas platforms.
“There are records of fatal interactions between whale sharks and vessels, and a considerable portion of the whale shark population at Ningaloo Reef have scars attributed to vessel strikes,” Ferreira explained.
The study underscores the importance of considering both natural and artificial structures when developing conservation and management strategies for marine megafauna like whale sharks.
This includes decisions related to Marine Protected Areas and the decommissioning of industrial infrastructure.
The research, published in Diversity and Distributions, was supported by Santos Ltd and AIMS, with additional co-authors from The Australian National University, ECOCEAN, The University of Queensland, and Murdoch University.
As whale sharks continue to face risks across large areas of their distribution, including ship strikes and fishing bycatch, the researchers emphasise the need for further studies to better understand and mitigate these threats.