Orca scare test for sharks

Armed with the longest audio of killer whales recorded in Australian waters, WA researchers hope to test the long-held theory that orcas' calls deter great white sharks.

Esperance documentary maker David Riggs this year ran the first research expeditions to what is believed to be the biggest seasonal gathering of killer whales in the southern hemisphere.

Hundreds of killer whales appear to congregate in a relatively small area of the Southern Ocean, 70km off Bremer Bay, for several weeks in late summer every year.

Mr Riggs and researchers from the NSW-based Marine Mammal Research unit recorded three hours of marine mammal audio, including an hour of killer whale calls.

The team spent hours observing killer whales off Bremer Bay with an underwater microphone deployed beneath the surface.

"There are a whole heap of different behaviours that have been recorded and now the challenge is to work out what mood the killer whales were in at the time," Mr Riggs said.

Mr Riggs, fellow documentary maker Jennene Riggs and the other researchers hope to work with WA Fisheries to broadcast killer whale audio in areas to which sharks are attracted, such as when whales have beached or a whale carcass is found.

Mr Riggs said he hoped the research would help determine which sounds were a deterrent to sharks. University of WA scientists are also looking at whether killer whale calls deter sharks.

The West Australian

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