Tuesday, 06 August 2019
Charles Darwin University
E-news
Northern Australia is a refuge for threatened Rhino Rays such as the Bottlenose Wedgefish. Source: Arnaud Brival
Northern Australia is a refuge for threatened Rhino Rays such as the Bottlenose Wedgefish. Source: Arnaud Brival

Top End waters a lifeboat for threatened rays

By Jon Taylor

New research from CDU has found the waters of Northern Australia to be a lifeboat for species collectively known as Rhino Rays.

Named after their distinctive pointy snouts, Rhino Rays comprise two families – giant guitarfishes and wedgefishes. This special group of rays was identified recently as the most threatened marine fish families, with numbers decreasing by more than 80% over the past 30 to 45 years.

Senior Research Fellow at CDU’s Research Institute for the Environment and Livelihoods, Dr Peter Kyne has been leading a research project into the extinction risk of Rhino Rays globally.

“Four species of Rhino Rays can be found in good numbers in the waters off Northern Australia. These waters seem to be offering a refuge of sorts from the intense fishing pressures on Rhino Rays to our north,” Dr Kyne said.

The fins of Rhino Rays are prized for shark fin soup. The meat is also valued and in some countries the gelatinous filling around the snout is considered a delicacy. The rays also have a naturally low reproductive rate that leaves them susceptible to overfishing in waters around Indonesia and Southeast Asia more generally.

While Rhino Rays are being overfished to the north, some are actually common in Australia’s northern waters.

Dr Kyne said it’s even possible to see the Giant Guitarfish in the shallows of Darwin Harbour.

“They can be seen in the harbour and around Casuarina Beach, swimming in the shallows with their fins sometimes seen sticking out of the water,” he said.

“It’s amazing to think that a species that’s under so much threat globally can be seen on the shores of an Australian capital city,” he said.

Rhino Rays are not a target species of the Australian commercial fishing industry and many of the strategies undertaken to reduce bycatch by the Australian fishing industry help keep Rhino Rays from being caught by accident.

“This highlights the importance of managing our marine environment. In the future, it’s not beyond imagination that the waters around our coast become the only location where Rhino Rays can be found in any numbers, a situation we are already seeing with the closely related sawfishes.

“The more we understand about these species, the better decisions we can make about marine environmental management and ensure that the biodiversity of our coastal waters are maintained,” Dr Kyne said.

This research was part of the Global Shark Trends Project, a partnership between Simon Fraser University, Charles Darwin University, James Cook University and the Georgia Aquarium, and was funded by the Shark Conservation Fund.