Manta rays are among the most remarkable creatures of the Great Barrier Reef. Despite their size and presence, we're only beginning to fully understand the crucial role these gentle giants play in our coral reef ecosystems.
Located at the southernmost tip of the Great Barrier Reef, 80 kilometres off the coast, Lady Elliot Island is a sanctuary where manta rays gather in large numbers, providing the ideal place for researchers to uncover more about this unique species. It was here that, for the first time in Australian waters, scientists successfully used ultrasound technology to look inside wild manta rays.
The groundbreaking trial was led by Project Manta, a long-running research program that brings together scientists, industry and the wider community to advance manta ray conservation. This Australia-first ultrasound was only made possible with the support of Blue Planet Ocean Conservation Trust, the University of Sunshine Coast, Lady Elliot Island Eco Resort and the Great Barrier Reef Foundation, in partnership with the Okinawa Churaumi Aquarium and Biopixel Oceans Foundation.
Dr. Asia Haines, a University of the Sunshine Coast research fellow working on Project Manta said: "We conducted ultrasounds for seven manta rays in total: five females and two males."
"The ultrasound allows us to detect pregnancies and assess maturity in males and females. We didn't detect any pregnancies this time, but we were able to observe other reproductive markers."
While slight changes to the belly of a manta ray are visible late in pregnancy to the trained eye, it's undetectable earlier without the use of ultrasound. Credit: Kathy Townsend.
#Why ultrasound manta rays?
Understanding wild manta ray reproduction is critical for their conservation and is essential when determining management actions needed for the protection of this vulnerable species.
"We currently have very little reproductive information on wild populations of manta rays," Dr Haines said. "The majority of the information we do know is coming from the great work being done by the team at Okinawa Churaumi Aquarium."
Manta rays are a long-lived species that matures to reproductive age very late and produce a low number of offspring. In Australian waters, with no targeted fisheries, manta ray numbers are considered stable.
"This provides the perfect opportunity to investigate reproduction in a more natural state," Dr Haines said. "The information we gather here on the Great Barrier Reef can provide a reliable baseline in the global effort to improve the conservation status of these species."
This research also allows us to discover which areas of the Great Barrier Reef are used for reproduction to inform management recommendations for the conservation of manta ray populations.
A researcher swimming up behind a manta ray so as to not disturb it when performing an ultrasound. Credit: Asia Haines.
#How to ultrasound manta rays in the wild?
The Project Manta team sought out the leading experts in the reproduction of captive sharks and rays from the Okinawa Churaumi Aquarium in Japan.
SCUBA clad technicians stealthily approached the free-swimming manta rays from behind with their ultrasound equipment and glided along above them to conduct the procedure.
Holding pace with the manta ray, the technician points the ultrasound device at the body of the unassuming animal to take the scan. The whole procedure is over in 10 seconds or less and doesn't interfere with the manta ray, which happily continues on its way.
"This pilot study was able to successfully test proof of concept by ultrasounding free swimming manta rays," recounted Dr Haines. "We intend to carry out similar work in 2026, where we're hoping we will be able to see some pregnancies!"
"We are incredibly excited to be supporting this brand-new research that has never been conducted within Australian waters," said Amy Gash, the Custodian at the Lady Elliot Island Eco Resort. "Bringing together tourism, research and conservation is pivotal in protecting marine species. We're proud to have been supporting Project Manta for 18 years and we're excited to see what's to come!"
This trial was conducted by Project Manta as part of the Reef Island Initiative, which is helping restore Lady Elliot Island to a healthy coral cay ecosystem, ensuring a habitat refuge is available for turtles and other marine life. Reef Islands is an initiative of the Great Barrier Reef Foundation, Lendlease, the Australian Government, the Queensland Government and the Fitzgerald Family Foundation.
