Relocating tiger sharks may reduce short-term risk of shark bites, research suggests
Tiger shark habitat use on the east coast of Australia varies by age and gender. (iNaturalist: Graham McMartin, Tiger shark, CC BY-NC 4.0)
In short:
New research suggests relocating tiger sharks away from swimming beaches could temporarily reduce risk of shark bites.
The study from Queensland’s Department of Primary Industries found relocated tiger sharks typically returned to a beach within three months.
What's next?
Researchers are planning similar studies examining the movements of bull sharks.
Tiger sharks relocated from swimming beaches generally return to a beach within about three months, new research shows.
Until now, scientists have had limited information about what happens after sharks are caught on drumlines along the Queensland coast and relocated.
A new study has analysed the behaviour of sharks relocated from the Great Barrier Reef Marine Park (GBRMP) under the Queensland Shark Control Program.
Tiger sharks are one of three shark species responsible for most shark bites globally. (supplied: DPIRD)
Researcher Tracey Scott-Holland from Queensland Department of Primary Industries (DPI) and her colleagues tagged and released sharks over the past six years.
Their study, published in the journal Ocean and Coastal Management, found tiger sharks relocated away from beaches were more likely to return to a beach than those caught in other locations.
However, on average, it took about three months for a relocated shark to reappear on a beach.
Dr Tracey Scott-Holland is part of the Shark Control Program scientific working group. (ABC Capricornia: Vanessa Jarrett)
Dr Scott-Holland said the findings suggested relocating sharks could reduce the immediate risk to swimmers and surfers, even if it did not permanently remove sharks from the area.
"We know that there's no single tool that can completely remove the risk,"Dr Scott-Holland said.
"But in this case, it's temporarily removing the risk of those individual sharks."
Catch numbers surge
The findings come amid mounting public concern about shark numbers.
Data from the Shark Control Program showed 3,430 sharks were caught in drumlines along the Queensland coast last year, double the number caught in 2024.
Sharks' mortality on traditional drumlines is higher than on smart alternatives. (Supplied: Humane Society International)
More than 40 per cent of those were caught in the Mackay and Capricorn Coast regions.
Dr Scott-Holland cautioned against assuming the figures reflected an increase in shark populations as catch numbers could vary with environmental conditions and changes to drumline equipment.
Emma Barrett from the Mackay Conservation Council said the increase in the number of sharks caught had not coincided with an increase in shark bites.
Emma Barrett says the long-term monitoring study is producing 'wonderful data'. (Supplied: Emma Barrett)
Tiger sharks, white sharks and bull sharks account for most shark bites globally.
The DPI-led study found tiger sharks detected near beaches tended to visit those areas for about 30 minutes and generally at night.
Ms Barrett said the study's "wonderful data" highlighted the importance of long-term monitoring to better understand shark behaviour.
"It shows a requirement for balance on all sides and continued monitoring, so we get real scientific data about how sharks are behaving," she said.
Concerns about shark deaths
The use of lethal methods to reduce the risk of shark attacks is contentious.
While any bull, tiger or white shark caught in the GBRMP should be tagged and released, 63 per cent of those caught in drumlines between 2021 and 2024 died before that could happen.
Whales and other species can become entangled in nets like this whale in Coledale, NSW. (Supplied: Khynan Gardner/ORRCA)
Over that three year period, 1,200 non-target species died in nets and drumlines.
Target species caught outside the marine park are euthanised.
The Queensland government has committed to an expansion of traditional drumlines and shark nets, along with trials of non-lethal methods, in its Shark Control Management Program for 2025 to 2029.
"The Crisafulli government made an election promise to only introduce changes to fisheries management based on scientific evidence and the government is delivering on that commitment," Queensland Primary Industries Minister Tony Perrett said in a statement.
The DPI began trialling catch alert drumlines along the Queensland coast in 2021.
SMART drumlines being installed. (ABC News: Charles Rushforth)
Unlike traditional drumlines, they are fitted with a mechanism that alerts authorities when a shark is caught.
Environmental scientist Daryl McPhee from Bond University said the new research showed drumlines and tiger shark relocation methods were "contributing significantly and positively to the safety of water users in the Great Barrier Reef".
Dr Daryl McPhee's research focuses on unprovoked shark bites. (Supplied: Bond University)
"[It shows] when you catch a shark and relocate it, it doesn't come straight back to the beach," Dr McPhee said.
Future research in the pipeline
Dr Scott-Holland's research team is now planning similar studies examining the movements of bull sharks.
Bull sharks prefer warmer waters and are expanding their territory to spend longer at more southern extremes. (iNaturalist: Niall McCarty, Bull shark, CC BY-NC 4.0)
She said the results of both these studies could inform a more targeted public education program.
"We can start to give some more localised Shark Smart tips so people can understand what these potentially dangerous species are doing at different times and places," Dr Scott-Holland said.
"The risk of being bitten by a shark is very, very small.
"We don't want people to be scared but there are things that people can do to reduce their risk even further."