By Marina Trajkovich, ABC
Grey nurse shark populations along Australia's east coast have steadily increased. Photo: ABC / David Harasti
Grey nurse shark numbers along Australia's east coast are on the rise, in "rare good conservation news" for the critically endangered species often dubbed "the labradors of the sea".
David Harasti from the New South Wales Department of Primary Industries said the often misunderstood species was crucial for the ocean's ecosystem and harmless to humans.
"It's one of the more placid sharks, they come and look at you really inquisitively, they follow you around," he said.
"They're a very ferocious-looking shark with big pointy teeth, but they're not known to bite people."
Growing to more than three metres in length, grey nurses became the first shark species in the world to be protected in 1984.
Photo: ABC / David Harasti
Harasti said that while there was no accurate population estimate for the time, divers and researchers raised the alarm after noting their decline.
"Divers went actively searching for grey nurse sharks, and where they used to find dozens, they could only find a handful," he said.
New research from the NSW Department of Primary Industries (DPI) and the CSIRO shows the population is slowly bouncing back.
Photo: ABC / David Harasti
"The adult population is now estimated to be around 1,500 along the east coast and rising," Harasti said.
"It's increasing around five percent a year, so this is a really good thing.
"This is one of our first good news marine stories for a threatened species."
Harasti said the study used genetic modelling to estimate population size, including techniques involving "sneaking up on the sharks" to collect samples at crucial dive and aggregation sites.
Photo: ABC / David Harasti
"Quite often, underwater, you're contorting your body to get these samples," he said.
"The results back up what divers have been noticing in the wild."
Accurate population picture
CSIRO principal research scientist Toby Patterson said getting an accurate sense of endangered populations was crucial for conservation work.
"The popular view is that it's easy to see how numbers are going - the reality is it's quite hard to get that fundamental data," he said.
Photo: ABC / David Harasti
Patterson said the CSIRO was also looking to use catch-and-release tagging methods like smart drum lines on more animals and species.
"We've used it on white sharks, sawfish in the north, river sharks and also terrestrial animals in Australia," he said.
"That then supports better decision making, better management responses, and to work out where funding and resources are most needed."
Threat remains
University of the Sunshine Coast researcher Ross Dwyer said while the results of the study were exciting, there was still work to be done.
"These results are really promising, it shows the population does seem to be increasing, but the numbers are still very low," he said.
"The genetic testing is exciting, but it's still in its infancy and needs to be corroborated."
Dwyer said grey nurse sharks were slow to reproduce and remained vulnerable to both recreational and commercial fishing.
He said more research into aggregation sites would inform new green zones, and called for divers to submit sightings and photographs to research projects like Spot a Shark.
"Particularly those spot patterns on their sides … that allows us to get a better understanding of shark interactions with fishing gear and how sharks are faring in terms of population numbers," he said.
- ABC
