Tuesday, July 21, 2015

'Sharks don't like to eat people': attack statistics contradict untested theories

From The Guardian by Oliver Milman

More of us are in the water than ever before – and while we kill 100m of them every year, it seems that sharks just don’t like the way we taste

Mick Fanning’s close shave with a shark while competing in South Africa is likely to amplify mutterings from some ocean-goers over what they perceive as a dangerous escalation in shark numbers.

 Shark Attacks Mick Fanning at J-Bay Open

Any flurry of shark attacks spurs calls for something to be done.
Already in 2015, there have been 13 unprovoked attacks by sharks, causing one fatality, in Australia.
This is fairly unusual – there’s only been one year over the past decade with more than 14 attacks.
In the US, eight people have been attacked off the coast of North Carolina since the start of June.
In one incident, a 12-year-old girl had her arm and part of her leg bitten off, while a 16-year-old boy had to have his arm amputated.
These incidents have led to a string of untested theories, with the North Carolina attacks blamed upon a change in water temperature that attracted a large group of migrating warm-water sharks, such as bull and tiger sharks.

In Australia, some surfers say shark numbers are exploding and that they are looking for food closer to shore.
“Anecdotally, surfers and fishermen across the country have been reporting that the size and abundance of large sharks are ­noticeably higher than they’ve been, in some places, for 30 years,” the Australian newspaper has stated.
“Some are asking if it is time to lift the great white’s protected status.”
Humans’ fear of sharks can be seen in the shark nets erected in parts of South Africa, New South Wales and Queensland, as well as the baiting and shooting program in Western Australia that was scaled down following an outcry from environmentalists and scientists.

So far, 2015 looks set to be on the higher side in numbers of global shark attacks.
Last year, there were 72 unprovoked shark attacks in the world, leading to three deaths, according to the University of Florida, which collates shark attack statistics.
There were 83 attacks in 2012 – the highest in the past decade – but it’s unclear whether there has been a sharp increase in attacks once population growth and improved record-keeping are factored in.
Australia had 120 attacks between 2000 and 2009 – more than double that of any other decade on record since 1900.
But when attacks per million people are considered, the picture is far less scary, with the trend dipping down from the 1930s, albeit with a slight rise in the past decade.

 Distribution of shark attacks in Australia between 1900 and 2009, including total number of attacks, the total population of Australia and the shark attacks per million people.

The Taronga Conservation Society, which collated this data, states that there have been 15 incidents a year, on average, over the past decade, compared with 6.5 annual incidents from 1990 to 2000.

But this increase in attacks, the society says, “coincides with an increasing human population, more people visiting beaches, a rise in the popularity of water-based fitness and recreational activities and people accessing previously isolated coastal areas.
“There is no evidence of increasing shark numbers that would influence the rise of attacks in Australian waters.”

Further research, published in the Australian Medical Journal last year, cites an increase in whale numbers as contributing to a spate of shark attacks on people off the Western Australian coast.
The risk for bathers less than 25m from shore is, however, “likely to remain very low, and well below the risk of other recreational activities undertaken in WA”, the journal states.
Other scientists back up this view – an increase in attacks must be seen in the context of increasing numbers of people in the sea, while shark populations are hard to pin down.
The idea of hordes of vengeful sharks is fanciful.
“Your toaster is more likely to kill you than a shark,” said Culum Brown, a fish biologist at Macquarie University.
“It is extremely unlikely that you will ever be, or even know, a shark attack victim.
“I think the numbers are pretty obvious. There are more people in the water each year: it’s not that there are more sharks. In fact in all likelihood there are fewer sharks due to over-fishing and habitat damage.”

Sharks are fast moving, cryptic animals.
Studying them is expensive, but what we do know about them shouldn’t be overly alarming, Brown said.
The chances of being attacked are extremely small and those who are attacked are predominantly targeted around the legs, suggesting that sharks are exploring their potential prey rather than devouring it.
“We do know that sharks don’t like to eat people,” he said.
“Studies show they respond strongly to the smell of seals and fish, but not humans.
The trouble with sharks is that they are inquisitive and when checking out a potential prey item they typically come up and have a nibble.
“Of course, if a 4m white shark has a nibble on you, it’s likely to be life-threatening. If they don’t like what they taste they leave.”

Unlike whales, sharks are hard to count.
But most scientists doubt the idea that protecting species such as great whites has resulted in their numbers ballooning, pointing out that an estimated 100m a year are killed worldwide, often for the shark fin soup market.
“The shark attack debate is a bit like the climate change debate,” said Dr Daniel Bucher, a marine ecologist at Southern Cross University.
“You can focus on the background noise or you can look at the long-term trend.
“You’d expect the number of attacks to go down given the number of sharks that have been killed since the 1980s. There is no plague of sharks out there. There’s just a larger population that spends more time in the water, increasing the probability of an attack.”
Bucher said research shows shark attacks can be influenced by rainfall and whether swimmers or surfers are near river mouths or fish feeding areas.

The film crew tags a number of great white sharks to study their movement patterns along Australia's coast. When one of the devices washes ashore, could a killer whale be to blame? 

Interactions with sharks also vary – sharks generally pass people without a second thought, although being in a group of people and turning to face the shark rather than thrashing around wildly in an attempt to move away can help.
But sharks have been evolving as awe-inspiring predators for at least 455 million years, and much more work is required to know exactly what triggers attacks.
Bucher said two incidents – one fatal, one not – off the coast of Byron Bay in February, showed there are no hard and fast rules when it comes to shark attacks.
“The fellow taken at Byron Bay was in shallow, warm water – it broke all the rules really,” he said. “Shark research is expensive and you can only study a few individuals. So that research becomes hard when one of those individuals does something you wouldn’t expect of shark populations at large.”

Links :
  • ISAF : about shark attacks

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