Sharks on trail of whales behind attacks

The University of WA emergency medicine professor analysed 40 years of Department of Fisheries and Global Shark Attack File shark bite data for the Australasian Medical Journal.

The data was available to the State Government before it started its shark cull last month.

‘I can’t understand why the Government would be using (cull) drum lines which are likely to catch species that have not attacked anyone off Perth in 40 years,’ Professor Sprivulis said.

The specialist in snake and other dangerous species’ bites found great whites were responsible for 10 of the 12 fatal attacks in the four decades, with 22 of the 30 fatal and non-fatal bites occurring in spring.

The 11th fatal attack’s species was unknown and the 12th’s was a tiger shark. At least five sharks of this species, ranging in length from 2.5-2.9m, were caught and released off Leighton and Cottesloe beaches, where drum lines are installed, in the past fortnight.

The bulk of great whites’ food is humpback whales, whose population is increasing about 10 per cent annually while the sharks, protected since 1997, could be increasing up to 12 per cent each year.

‘Great white sharks are known to migrate large distances between breeding grounds and feeding habitats, with research indicating that white sharks, some from as far afield as South Africa, migrate up the WA coast in spring, returning to southern waters, such as the Great Australian Bight, in early summer,’ Prof Sprivulis said.

He found the threat of attack to Perth swimmers 25m from shore in summer was at least 50 times less than recreational cycling.

He said people needed accurate data to make informed decisions on how to reduce danger in the sea, and the Government needed to educate about the true risks.