NICKY PHILLIPS July 27, 2012
SYDNEYSIDERS have been treated to some spectacular whale watching this week, and as the giant creatures swim along the coast scientists will test whether underwater alarms reduce the number of the large mammals caught in sharks nets.
A Sydney research team, which includes scientists from Macquarie University, Taronga Zoo and the state government, have placed a test alarm, known as a pinger, in the path of migrating whales on a mooring off the coast of Cape Solander at Botany Bay.
They hope the alarm, which transmits a low frequency beep the whales can hear, will warn the animals to avoid nets and other man-made obstacles.
Every year tens of whales become entangled or trapped in nets as they migrate from the Southern Ocean to warmer waters in northern Australia. Such collisions often result in serious injury and sometimes death for the animal.
Rob Harcourt, the research leader, said fishing net entanglement was one of the top two causes of whale mortality worldwide.
''Stopping entanglement is much more important for conservation than stopping whaling,'' Professor Harcourt, from Macquarie University, said.
A marine biologist with Taronga Zoo, David Slip, said while the number of entanglements had been reduced where the devices had been deployed in Queensland, the test alarm, which was turned on and off periodically, would establish whether the whales responded to the device.
''What we hope doesn't happen is they think 'what's that' and move towards it,'' Dr Slip said.
Each day, research assistants, including Vanessa Pirotta, stand on the cliff tops at Cape Solander to count and track the movement of the creatures, mainly humpback whales, as they migrate north.
''I sight the animal with my naked eye then use my instrument, a theodolite, and pinpoint the animals and that tells my computer where the whale is in position to the whole area,'' Ms Pirotta said.
''I'm looking at the animals and what kind of behaviours they exhibit, but I don't know if the alarm is on, so I am blind to it,'' she said.
As whale populations have steadily increased since whaling was banned in Australian waters in 1979, so has the number of entanglements along the east and west coasts.
Earlier this month, it took rescuers three hours to free a young female humpback whose head and pectoral fin became wrapped in a shark net on the Gold Coast.
If the alarms do work, they could be deployed on any type of fishing gear, including lines, lobster pots and shark nets, said Dr Slip, who hopes to have results by the end of this migration season.