The movements of a $5,000 satellite tag, originally attached to a gray reef shark, have baffled researchers tracking and studying the endangered species off Australia’s east coast.
the main points:
- The tracking marks came off two of the sharks prematurely
- In one case, researchers suspect, a fisherman accidentally caught the shark and removed its tag
- Conservation biologist Adam Stowe says monitoring research is vital to species recovery
“It could be in someone’s home, it could be buried in the sand, and that’s a real mystery, but someone knows more about this sign,” said marine biologist Dr. Carly Kilpatrick.
It’s one of two tracking markers that showed up prematurely from gray nurse sharks just months after they were installed as part of a program that monitors the species’ movements along the East Coast, where populations have dwindled to less than 2,000.
Dr Kilpatrick, chief conservation officer at the Queensland Department of Environment and Science (DES), said miniPAT tracking tags were initially attached to nine sharks at Flat Rock, in Moreton Bay, in September last year.
The tags help researchers from Sea World and DES document important sites used by sharks and identify any new sites used by the species as the climate changes, so they can be protected.
Two tags are missing
Tracking tags are usually attached to or near the dorsal fin and are programmed to pop up and resurface on a certain date, so that they can then send back GPS signals and be retrieved by researchers.
“We get a summary of the data from a satellite transmission, but if we get the marker back, we get the full data set,” said Dr. Kilpatrick.
The missing tag that sent up confusing location transmissions belonged to a 1.9-meter gray shark.
It appeared about 600 kilometers or so off the east coast [near the] Coffs Harbor area [on December 20] Then in a few hours I sent a signal in Pompeii Bay as well.
The marker sent its final transmission on December 22nd, but sent out strange signals from Earth before it calmed down.
Maybe someone was out on a hunting trip [trip]caught the trip back to Coffs [Harbour] Then he didn’t yet know what to do with the sign and threw it overboard,” said Dr. Kilpatrick.
Another sign appeared prematurely from a mature female measuring 2.8 meters long on December 26, and was last detected northeast of Yeppoon on the Coast of Capricorn on January 8.
“We don’t know exactly what happened, but he was floating on the surface of the water and then there was silence,” said Dr. Kilpatrick.
A common misconception
Dr. Kilpatrick said the team needs to learn more about the species to protect pregnant females during migration.
“We’re actually trying to find another lost bearing site for these sharks and make sure they are protected in these areas,” she said.
Twice a year, sharks migrate from southern New South Wales to central Queensland, said Adam Stowe, a conservation biologist who has been studying the species for about 20 years.
Approximately 1,500 to 2,000 gray sharks live on the eastern coast of Australia, but their population is about 400.
“A combination of features of their natural history and the fact that they have been overfished has resulted in them being seriously endangered,” he said.
“One of the reasons for the decline of the gray shark is that it was considered, for a brief period, as a dangerous species to people.
“They are not man-eaters, but it was definitely a misconception from a few decades ago.”
He said that gray nurse sharks have grown to about three metres, females have taken 10 years to mature, and they have two pups a maximum of twice a year.
“If you multiply the population, it takes a long time to recover because their rate of reproduction is so slow,” he said.
How can you help
Associate Professor Stowe said the monitoring program and other citizen science projects are essential to the shark’s survival.
“It’s very important, we need to know where they are [aggregation sites] And whether they change.
Since sharks were known to congregate in certain locations, people often had the “false impression” that the population was strong.
“That’s why they are such a popular species to see for ecotourism, you can dive into this site and see dozens of individuals,” he said.
“[But] The science is strong — there are generally low numbers.”
Dr Kilpatrick urges anyone with the signs, or any information about them, to contact DES on 07 3101 2085.
“Keep an eye on the tag if you see it floating in the water, if it gets caught in a net, or if anyone has this tag on their boat or has found it – please return it to us,” she said.
“When people fish outside, if you accidentally capture a gray nurse shark, whether you are a recreational fisherman, charter fisherman, or commercial fisherman, you need to know how to identify them.
“We need to release them as soon as possible, and if, unfortunately, the shark is dead, please keep the tag. If the shark is alive, leave the tag in.”