By Geoff Thompson, Mary Fallon and Elise Worthington.
The shark nets used on Sydney beaches in New South Wales do nothing to reduce the chance of attacks, a statistical analysis has found.
Associate Professor Laurie Laurenson from Deakin University’s School of Life and Environmental Sciences has analysed 50 years of data about shark mitigation programs and coastal populations in NSW and South Africa.
He told Four Corners reducing the density of local shark populations did not reduce the likelihood of shark attack.
“I can show statistically that there is no relationship between the number of sharks out there and the number of shark attacks,” he said.
“It’s just simply not there … I’m surprised that it’s not there, but it’s not there.”
It is the first time a comprehensive analysis has been done in an effort to link populations of sharks and people and the number of attacks in netted areas.
The findings are included in an unpublished paper which is in the process of being peer reviewed.
“We could not demonstrate a statistically significant relationship between the density of the sharks and the number of attacks in the localised area around Sydney where there have been historically large numbers of attacks and there’ve been large numbers of mitigation programs,” Dr Laurenson said.
Shark mitigation programs work by reducing the density of local shark populations by catching them in nets or on baited hooks called drum lines. Drum lines are not used on NSW beaches.
“Intuitively, you would expect if there are fewer sharks out there, there’s going to be fewer attacks. We can’t show that,” Dr Laurenson said.
The paper is the result of three years of research by Dr Laurenson and his Deakin University colleagues Dr Jacquomo Monk and Dr Fredrik Christiansen.
CSIRO expert backs shark nets
NSW chief shark scientist Dr Vic Peddemors disputed the findings and said a comparable statistical analysis was being completed by the NSW Government.
“We’ve been working on that literally for the last six months, trying to also bring in the human population growth, so it’s taken a lot of time and effort to go way back,” he said.
“Unfortunately it’s taking longer than what we had hoped. But I’m confident — without the super serious stats — I’m absolutely confident that shark nets have worked.”
The CSIRO’s top great white shark expert, Dr Barry Bruce, believes shark nets reduced risk in particular areas.
“Shark nets certainly reduce risk because they catch and kill sharks that have the potential to bite people,” he said.
“I guess what we don’t know — we may never know — is to what extent the overall risk has been reduced by losing that shark.
“From a ‘whole of’ perspective the answer is probably ‘no’, but do they reduce risk at the particular areas that they’re put in? The answer’s probably ‘yes’, but we don’t know by how much.
“Shark meshing and drum line programs only occur in a very minor fraction of Australia’s coastline and sadly there are attacks that are spread in all sorts of other areas.”
Dr Laurenson’s findings are supported by the director of the University of Western Australia’s Centre for Marine Futures, Professor Jessica Meeuwig.