Feb 8, 2010, 10:33 GMT
Sydney - Whenever there is a deadly shark attack in Australia - on average, about once a year - the cry goes up that a rogue fish is on the loose and must be hunted and killed before it strikes again.
Local authorities usually pander to the hysteria, sending out a posse to capture and kill an animal that some say will have developed a lust for human blood and will be lurking and hoping for another victim.
All nonsense, of course. The notion of a rogue shark is as silly as a rogue snake or a rogue mosquito.
Only a tiny proportion of attacks are fatal. This is because the shark has mistaken a swimmer for its usual prey and lets go after the first bite.
Last year was a bad year in Sydney: three swimmers gored over a two-week period.
Again, the baying was for vengeance. Miranda Divine, a columnist with The Sydney Morning Herald, put a popular case when she said that 'if it comes to a choice between a shark life and a human life, there just should be no contest.'
Trying to pin an attack on a particular shark is impossible - as researchers in Sydney announced earlier this year. Sharks are on the go all the time. They don't hang around.
The researchers fixed acoustic tags to five sharks caught in Sydney Harbour and monitored their movements through 45 listening posts in enclosed waters and up and down the coast.
They picked bull sharks, a variety common in the harbour and the perpetrator in at least one of last year's attacks.
One 2.4-metre-long specimen left the harbour a week after it was tagged, heading north. Two weeks later - and after staying just a day at the place which seemed the destination of its 220-kilometre swim - it was back in the harbour.
'It was a long swim to stay just a day or less,' said Amy Smoothey, head of the Shark Tracking Research Programme. 'But we don't know why it did it. There's lots we don't know about our bull sharks.'
The programme will run for 10 years, said New South Wales Primary Industries Minister Steve Whan. The object is to help swimmers stay out of the way of sharks.
'It's really important to get a better understanding of what sort of movements and habits these sharks have,' he said. 'That gives us a better idea of not only how they move around the harbour, but also what to tell people, what advice to give people on their own swimming.'
The current advice is to stay out of the water at dusk and dawn, when sharks generally feed, and to avoid murky water, where poor visibility means sharks are even likelier to mistake humans for their usual prey.
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