Climate change projected to deplete food sources of endangered whale sharks

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Australia; NSW; VIC; QLD; WA
Brad Norman
Brad Norman

New research has revealed the impact climate change is projected to have on whale shark constellations in the Indian Ocean, including those at WA’s Ningaloo Reef.

Media release

From: Murdoch University

As part of her PhD research at The University of Queensland, lead investigator Dr Samantha Reynolds, now a Research Fellow from Murdoch University’s Harry Butler Institute, used three future climate change scenarios from CMIP6 climate models to investigate how ocean warming could affect the energetics and distribution of the world's largest marine ectotherm.

Using biotelemetry, animal-borne electronic tags, Dr Reynolds and her research team were able to assess how temperatures can affect a whale shark’s metabolism and movements.

Results of the study showed the warming oceans would increase metabolic rates and energy needs of the whale shark, while simultaneously depleting its food sources.

With the species already categorised as endangered, Dr Reynolds said it was imperative to understand the risk human behaviour poses to its longevity and wellbeing.

“Whale sharks have been around for millions of years, but now, thanks to humans, they are endangered,” Dr Reynolds said.

“I want to make sure that we protect and conserve them so that they continue to fulfil their important role in the world’s oceans, and future generations can experience the wonder of swimming with the world’s biggest fish.”

Dr Reynolds’ research identified ocean temperatures at Indian Ocean whale shark aggregations may rise by up to 4.9°C by the year 2100. This will increase whale sharks’ metabolic rate and energy needs.

The changing climate will also decrease zooplankton - the whale shark’s main source of food.

Dr Reynolds said a pivotal message she hoped to convey through her research was that the repercussions of human behaviour on the world’s oceans are severe.

She said the time for action was now and that the study would help prompt this action.

“I hope that my research can help to guide protection and conservation of whale sharks, but also help people to understand that humans are having huge impacts on the world’s oceans, from the smallest organisms to the biggest fish in the sea,” she said.

“We need to minimise our detrimental impacts and find ways to have positive impacts on our planet.”

Journal/
conference:
Science of the Total Environment
Research:Paper
Organisation/s: Murdoch University, The University of Queensland, CSIRO, The University of New South Wales, University of the Sunshine Coast, Monash University
Funder: SDR was supported by an Australian Government Research Training Program Scholarship and a stipend top-up scholarship from Thyne Reid Foundation. Financial support for the research was provided by the Holsworth Wildlife Research Endowment awarded to SDR from the Ecological Society of Australia and grants to BMN from the Estate of the late Winifred Violet Scott and The Rolex Awards for Enterprise. JDE was funded by Australian Research Council Discovery Project DP190102293.
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