Are shark attacks becoming more common?

Sharks have again made the headlines for all the wrong reasons.

On Tuesday a British man, Ian Redmond, was fatally attacked by a shark while he was snorkelling in the Seychelles in the Indian Ocean.

It was the second fatal attack by a shark in the area this month.

But are shark attacks becoming more common, and are more swimmers and bathers dying as a result?

According to the International Shark Attack File (ISAF), a program run by marine biologists at the Florida Museum of Natural History, the number of unprovoked shark attacks has grown at a steady pace over the past century with each decade having more attacks than the previous.

For example, in the 1900s there were, worldwide, around 20 recorded unprovoked attacks by sharks on people.

That steadily climbed to around 100 by the 1940s, passing 500 by the 1990s. By the 2000s the figure had surpassed 650.

But in many respects, this data is misleading.

The ISAF is the best current data set for shark attacks we have, yet by its curators’ own admission, this rising tally of recorded unprovoked attacks does not actually mean that sharks have in any way gained a greater taste for humans, or are attacking them at a greater rate.

That is because the media and scientists paid far less attention to shark attacks in the past than they do now.

In 1916, people along the coast of New Jersey, US were gripped by panic as a spate of shark attacks occurred in quick succession between July 1 and July 12.

The national media descended on the area to report the attacks, which killed four people and injured another. Scholars to this day debate which shark species was responsible, with a bull shark or great white being most often blamed.

But those attacks created an exceptional media storm. Most attacks went unreported and data about them was not systematically and objectively collated.

The ISAFs own records show a dip in the number of attacks occurring during the 1970s and 80s. But that, says the ISAF, is more likely due to the fact that the organisation itself didn’t keep as complete records as it did before and since.

Other factors have changed too, and must be taken into account.

The human population has grown rapidly in the past century, meaning many more people are taking to the water, and engaging in recreational activities for longer periods that put them in closer proximity to sharks.

Florida has the most unprovoked shark attacks recorded anywhere in the world. The state’s increase in shark attacks, from a handful in 1900-10 to around 190 in 2000-10, mirrors almost exactly the decade by decade increase in the numbers of human residents, from 1 million to more than 16 million today.

California, Japan and Hawaii show a similar trend. In Australia, there are no more attacks today than there were in the 1920s, 40s or 50s, and actually far less than in the 1930s or 1960s, despite the human population rising from 4 million to more than 18 million.

Another interesting statistic is that while recorded attacks have steadily climbed each decade, the proportion of people dying as a result has fallen consistently across the same period.

In the 1900s, 0.6% of unproved shark attacks on people proved fatal. By the 1960s that had fallen below 0.2% and today less than 0.1% of victims die as a result of an unprovoked attack.

There are likely to be many reasons for this decline; modern surfboards and diving gear get bitten rather than their owners, while victims reach vastly improved medical facilities much sooner.

Even identifying which sharks are most likely to attack is notoriously difficult.

Great white sharks get the most blame. This species, one of the largest of the predatory rather than filter-feeding sharks, has been recorded attacking unprovoked 182 people, killing 65.