Florida again led the United States in shark attacks last year, with 28 incidents and no fatalities. The vast majority of the Florida incidents were minor ones in which a shark quickly bites an arm or leg in poor visibility water, releasing it as soon as the shark realizes its prey isn't a fish.

"Most of them are better called bites than attacks," said George Burgess, curator of the International Shark Attack File. "They're the equivalent of dog bites."

The five types of shark were among 21 species of shark and ray, including sawfish, granted new protection status at a convention summit in November.

Although Australia did not object to the listings in November, it is now seeking to opt out of the commitment to cooperate with other countries to ensure the five migratory shark species do not become extinct. The expanded list is due to come into effect on 8 February.

Counting "band pairs," which are series of rings that alternate between translucent and opaque within the sharks' vertebrae scientists looked at band-pair data from 77 sharks that were captured between 1963 and 2010.

Using this method, the researchers found that great white sharks were considerably older than previously thought, with the oldest individual animal in the study reaching 73 years of age.

They also found that the great white sharks — at least in the Atlantic Ocean — matured more slowly than previously thought, thus making them even more vulnerable to threats.