A "genetically unique" population of sharks that can walk on seabeds and land has been discovered at Lady Elliot Island, near the central Queensland coast.
The bottom-dwelling epaulette shark (Hemiscyllium ocellatum), which commonly lives in shallow reefs, has evolved to use its fins as feet and can stay out of the water for up to two hours.
Its name comes from the large black spot behind each pectoral fin, which resemble the shoulder pieces worn on military uniforms.
Marine biologist Jacinta Shackleton said she was working as a master reef guide in 2021 when she noticed that the epaulette sharks from Lady Elliot Island had different spot patterns from those in the northern Great Barrier Reef.
"The ones up north have that big dominant, white halo [around the spot], but the ones in Lady Elliot have brown shading," she said.
This casual observation formed the basis of her peer-reviewed genetic study at the University of Sunshine Coast, which was completed in July and showed there were distinct populations of walking sharks along the Queensland coast.
"We're quite close to looking at, potentially, a different type of species [in the southern Great Barrier Reef]," Ms Shackleton said.
"We've got a really big genetic gap between the ones that we looked at off of Cairns, for example, compared to the ones we looked at off of Lady Elliot."
A new species?
Ms Shackleton says her research, which is pending publication, establishes that the Lady Elliot sharks are genetically unique, but she still needs to analyse more samples to confirm whether they are distinct enough to be considered a new species.
"These insights can now be used to better inform management and conservation," she said.
"It's really important because they are pretty popular sharks at aquariums, and if we're just heavily harvesting sharks from one particular area we might deplete that whole genetic stock."
Ms Shackleton said the conservation of epaulette sharks was more critical than ever because they were a highly adaptable.
"When we do come into a warmer climate, they're going to be potentially one of the species that's going to survive better than others," she said.
The epaulette shark's ability to walk on land and withstand low oxygen by switching off non-essential brain functions is part of what helps it survive the harshest ocean conditions.
'Tough little shark'
Professor Jodie Rummer, who has spent the past 10 years researching these "quirky little walking sharks" at James Cook University, said Ms Shackleton's "groundbreaking" study would form the basis for future research.
"What's really important in terms of her findings … is could we have geographically distinct populations that might be able to cope with climate stressors a little bit differently?" Dr Rummer said.
She said epaulette sharks were a great indicator species for understanding the impacts of climate change.
"The Great Barrier Reef has got really, really warm temperatures up in the north and a bit cooler temperatures in the south," Dr Rummer said.
"So that's a really great gradient for us to look at some of the traits in geographically distinct populations that might help us understand what's necessary to cope with climate change."
Dr Rummer said a recent James Cook University research published in the Scientific Reports journal found that baby epaulette sharks were born smaller, undernourished and exhausted in warmer waters.
"That's a big wake-up call for us," she said.
"Because if they can't hack it then how will other sensitive species survive out there?"
Dr Rummer said epaulette sharks were also important because they were in the middle of the food chain and acted as the "glue" that held ecosystems together.
"We've got to give it credit, this tough little shark species — it's doing really, really well under a lot of challenging conditions," she said.
"But we've already seen its limits."
