Shark nets used at most beaches do not protect swimmers, research suggests | Sharks
Sharks This article is more than 8 years oldShark nets used at most beaches do not protect swimmers, research suggests
This article is more than 8 years oldScientists tell ABC’s Four Corners that nets are not effective barriers and that a bigger shark population does not increase attacks
The shark nets used at most beaches might make you feel safer, but they do nothing to reduce your chance of being attacked, according to a new analysis of data.
The data, compiled over half a century by Laurie Laurenson from Deakin University, was presented on ABC’s Four Corners program on Monday night.
CSIRO shark expert Barry Bruce said a shark net is not a barrier, but rather a fishing device.
“It’s a couple of hundred metres long, there might be two at a beach which is many, many kilometres long. They are set at a depth offshore where they don’t reach to the surface so they only come up six metres or so from the bottom in 10 metres of water. In some respects you have to be an unlucky shark to get caught,” he said.
Bruce said while shark nets at Bondi Beach had caught sharks, that did not mean the nets had prevented shark attacks.
“If you’re dead you can’t bite anybody. What we don’t know is whether that shark would have ever bitten anybody and we don’t know how many sharks swam through the area that didn’t get caught,” he said.
Bruce said most of the time when sharks and people were in close proximity there was not an attack and once it was understood what made sharks bite people, then attacks could be prevented.
“I can show statistically that there is no relationship between the number of sharks out there and the number of attacks,” Laurenson told the program. “It’s just simply not there. I don’t know. I’m surprised that it’s not there but it’s not there.”
Laurenson said he looked at the human population from each area they studied over 50 years and found a clear link between the number of people and the number of attacks. But when he looked at the number of sharks, he found no correlation between the predators’ population size and the number of attacks.
Laurenson said that suggested measures like nets and drumlines that lowered shark populations were probably not making people safer.
In a three-month period in 2014, drum lines in Western Australia caught 172 sharks, of which 163 were tiger sharks and none were great whites. However Four Corners reported that tiger sharks had not killed anyone in Western Australia for more than 20 years.
Natalie Banks, a shark campaigner for Sea Shepherd Australia told the program they had seen dolphins turtles, stingrays and dugongs dying in shark nets elsewhere. “This is a marine cull as far as I’m concerned,” she said.
New shark net technology that covered the whole beach with a plastic mesh had been trialled successfully at Coogee beach in Perth, but whether it would work at larger beaches with bigger waves was unknown. A test is due to happen this year at Ballina in New South Wales.
Vic Paddemors, NSW’s chief shark scientist from the Department of Primary Industries, said although they couldn’t prove statistically that shark nets had prevented attacks, he believed they had.
“Without a question of a doubt I can definitely put my hand on my heart and say that I believe that shark nets work and I believe that you are a lot safer at a netted beach, not only because of the nets but obviously also because they are at patrolled beaches,” he said.
Rick Fletcher, a spokesperson for the Western Australia Department of Fisheries said that during the drum line program in the state, nobody was attacked. “It certainly wasn’t not successful,” he said.
Consistent with Laurenson’s work, earlier data had suggested that increases in shark attacks in recent years were mostly correlated with increases in coastal populations.
John West from Taronga Conservation Society had been tracking the number of human-shark interactions in Australia for decades. His Australian Shark Attack File found an increase in the human population and how frequently people went in the ocean was closely linked to rises in shark attacks in recent years.
West’s data showed that between 1995 and 2004 there was an average of 9.6 unprovoked shark attacks a year in Australia. In the following decade that increased to 12.3. Meanwhile, Australia’s population increased from about 17 million to more that 23 million, with most of that increase concentrated on the coast.
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