Climate change projected to deplete food sources of endangered whale sharks

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As part of her Ph.D. 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, published in Science of the Total Environment, 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 categorized as endangered, Dr. Reynolds said it was imperative to understand the risk human behavior poses to its longevity and well-being.

"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 fulfill 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 behavior 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 minimize our detrimental impacts and find ways to have positive impacts on our planet."

More information: Samantha D. Reynolds et al, Effects of climate warming on energetics and habitat of the world's largest marine ectotherm, Science of the Total Environment (2024). DOI: 10.1016/j.scitotenv.2024.175832

Journal information: Science of the Total Environment

Provided by Murdoch University