Climate change depletes food sources and increases energy needs of whale sharks, new study finds

A new study by Murdoch University has revealed the impact climate change is projected to have on whale sharks, including those at WA’s Ningaloo Reef.

The study conducted by Murdoch University research fellow Dr Samantha Reynolds predicted warming oceans will increase energy needs of the endangered whale shark while simultaneously depleting its main food source.

As part of her PhD research at the University of Queensland, lead investigator Dr Reynolds used three future climate change scenarios from CMIP6 climate models to investigate how ocean warming could affect the world’s largest marine ectotherm.

Using 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.

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,” she 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 said ocean temperatures at Indian Ocean whale shark aggregations may rise by up to 4.9°C by 2100, increasing 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 were severe.

She said the time for action was now and 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.”