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The findings are included in an unpublished paper which is in the process of being peer reviewed.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.
“These results are completely consistent with previous studies from Hawaii, which showed no relationship between shark abundance and incidence rates,” she said.
“[It’s] also consistent with analyses of the Queensland program that show no effect of drum lines on incident rates by reducing local abundance of sharks.”
A spokeswoman from the Queensland Department of Agriculture and Fisheries said there had been only one fatal attack on a controlled beach since 1962, compared with 20 fatal attacks on the same beaches between 1919 and 1961.
The number of shark attacks in Australia has more than doubled since the 1980s, but figures supplied by the NSW and Queensland governments show large reductions in the number of fatalities on beaches with shark mitigating equipment since it was introduced.
Great whites drawn to coast to feed
Dr Laurenson said this was explained by better medical intervention.
“If you look at how far medical intervention has come since the 1960s, they are very, very, very good at it,” he said.
“The reason there’ve been no fatalities is because of earlier responders having sufficient training, having the right equipment, knowing exactly what they want to do.
“They get there early. They get people to the hospitals quickly.”
There was a cluster of shark attacks in Ballina last year, and in Western Australia seven people were killed by great whites sharks between 2010 and 2013.
Scientists believe during those clusters, great whites were likely drawn to the coast to feed.
“If there is a link to temperature, it’s not so much that the white sharks love a particular temperature, it’s the things that they feed on,” Dr Bruce said.
“The fin fish, the other sharks, the rays have a temperature preference and their movements are related to temperature and the sharks are just following them.”
Watch “Shark Alarm” on Four Corners on ABC TV at 8.30pm tonight.
This post originally appeared on ABC News.
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