Are humans to blame for shark attacks?

By AAP with AG staff | September 5, 2011

Shark attacks seem to be on the increase around the world – overpopulation and overfishing could be among the culprits.

A SEEMING INCREASE in shark attacks worldwide may well have a human cause, with low-cost air travel, but also overpopulation, overfishing and even climate change among the hidden suspects, say experts.

On Sunday a man in his 20s was killed in a shark attack off south-west WA. He was body boarding with a group of friends at Bunker Bay, near Dunsborough. Headlines were also grabbed in August by a decision to close beaches in the Seychelles after a shark savaged a British honeymooner before the horrified gaze of his spouse, in the second fatal attack there in 15 days.

The same month, in Russia’s Pacific coastal region of Primorye, a shark mauled a 16-year-old boy just one day after another man lost his forearms defending his wife. In the Caribbean, a woman vacationing in Puerto Rico received a 30cm-long shark bite as she swam in a tourist haunt, the bioluminescent bay of Vieques.

More shark attacks

But does this mean that there are an unusual number of shark attacks occurring? According to the International Shark Attack File (ISAF), compiled at the University of Florida in the US, 79 unprovoked shark assaults occurred around the world in 2010, six of which were fatal. This was the highest number in a decade. In 2009 there were 63 attacks with six fatalities, and in 2008, there were 53 recorded attacks, four of them fatal.

So far in 2011, there have been at least 61 recorded attacks and 10 deaths. However, compared to deaths from smoking, road accidents, lightning strikes or even other animal attacks, the risk is minute, say experts.

“The attention from shark attacks is completely overblown,” said Agathe Lefranc, a scientist with a French group, the Association for the Study and Conservation of Salachians (APECS), a family of species that includes sharks and rays.

Find a timeline of fatal Australian shark attacks here.

Human activities in shark habitat

Marine biologists say there is little research into the causes of shark attacks, but point to several possibilities, all linked to human activities. The first is simply the growth in mobility, with cheap air travel and package vacations enabling people to swim, snorkel, surf or dive in places that previously had little human presence.

“The growth in shark attack numbers does not necessarily mean that there is an increase in the rate of shark attacks,” says ISAF. “Rather it is most likely reflective of the ever-increasing amount of time spent in the sea by humans, which increases the odds of interaction between sharks and people.”

David Jacoby, a specialist at the Marine Biological Association (MBA) in Plymouth, England, says shark attacks are events that have local causes and are often poorly investigated, if at all.

One case that stands out occurred in the Egyptian resort of Sharm el-Sheikh, where sharks made five attacks in a week in November-December last year, one of which was fatal. The finger of blame was pointed at a passing livestock transport ship that had dumped sheep carcasses overboard and at operators who illegally fed sharks to thrill the tourists.

Overfishing and population growth a shark attack contributor

Another question – but again, lacking sufficient data to answer it – is the impact on shark behaviour from overfishing and from global warming, which affects ocean temperatures and currents.

“We know that these animals are opportunistic and they go to where food sources are available, and those resources do move, and they are dependent on currents, nutrient-rich patches,” says David. “It’s not just sharks that do this; all large pelagic predators are drawn to areas where there is high food availability. But whether this is a case of increased human activity is unclear.”

According to experts at Sydney’s Taronga Conservation Society, who keep the Australian Shark Attack File (ASAF), although Australia continues to have a bad reputation concerning the threat of shark attacks to swimmers, the statistics do not support these claims.

“In the last 50 years, there have been only 53 human fatalities in Australian waters from shark attacks. Some years there are no fatalities recorded, other years there have been up to three in a year, but the average remains around one per year,” says the ASAF website.  “Yet each year thousands of swimmer-days take place on our beaches, harbours and rivers and the number is increasing with both increasing population and tourism.”

The experts behind the ASAF argue that the enormous increase in the size of the Australian population over the last century has contributed to the increase in numbers of overall shark attacks (including non-fatal attacks).

A hugely successful fish in evolutionary terms, with a lineage dating back more than 400 million years, the shark is under relentless attack from humans themselves. A third of open-water shark species, including the great white and the hammerhead, are facing extinction, driven in part by demand in Asia for shark-fin soup, according to the International Union for the Conservation of Nature (IUCN).

Find a timeline of fatal Australian shark attacks here.

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