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Dr. Mark Meekan: I don't give this argument too much credit. From a science point of view, there are a lot of links in the chain for that to be true, and we've got no evidence for them. The shark's prey would have to be overfished, and there would have to not be an alternative prey for them to switch over to in order for them to turn to humans. You need some good hard data to support that argument.That's one of the big problems with white sharks, and sharks in general—there's very little hard data about populations and how they've been changing over time. Yet people like to spout these sorts of theories and the arguments tend to be very, very emotive. And without any real data, they're given airtime.
You certainly raise your risk of shark attacks in an area where you have blood and dying fish in the water. If you go spear fishing, for example, you're presenting sharks with signals of distressed and dying fish in the area. And you have to be more aware of the risks of that activity than you do if you're just wading in knee-deep water. They're two different activities that give you two different risk profiles. But does that explain the high rate of shark attacks? I don't think so.
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Well, first we need to understand where these animals are, how many we've got, and where they're moving. These are all key research projects that we're currently involved in.We know that there are just three species that are attacking humans, and they're bull sharks, tiger sharks, and white sharks, of course. And these sharks all move huge distances. We have tiger sharks moving up and down the coast of West Australia, going as far as Indonesia and South Australia. This is mirrored by white sharks that inhabit cold waters in Tasmania and South Australia in the summer months but then, during the winter, head north to West Australia. Similarly, there've been white sharks tagged off California that spend winters out in what they call "The White Shark Café" off of Hawaii. And bull sharks tagged in the Great Barrier Reef have been seen in Sydney Harbour. These animals are moving very large distances across waters off different temperatures.But the problem is that we have such poor data on the distribution and abundance of most shark species that we couldn't tell whether this is being changed by global warming. The data we have is just so poor at the moment that we don't know how many sharks we've got.
The real problem with rates of shark attacks is that you're trying to take statistical trends on very rare events. Shark attacks, although they make the news, are extremely rare events. And the problem with trying to create statistics about rare events is that they rapidly become meaningless.We can't tell if shark attacks are increasing or simply more people are getting in the water. The only thing we can conclude is that an increasing population puts more people in the water, so you're likely to have an increase in shark-human encounters.Follow Max on Twitter.