Wednesday, February 01, 2006

New device used to track sharks

Barry first encountered Neale in March 2001 when he was caught as part of a trial of satellite tracking white sharks. The research is part of a bigger picture for understanding the behaviour of white sharks; how sharks appear in certain places at certain times and the cues that they use for movement, explains Barry.

The goal is "for us to better predict whether we are likely to have interactions with sharks so that we can learn to live with them."The scientists travelled to Ninety Mile beach east of Wilson's Promontory in Victoria. looking for small white sharks. When Neale was first brought on board, Barry was feeling a bit sorry for him. "I gave him a hug," he says tongue-in-cheek. Neale was about 4-5 years old, 2.4m long and weighed about 150kg.

The team placed him on a foam mat and removed the hook, then attached the tag to his dorsal fin. The whole operation was timed to take only a few minutes. Scientists don't like to catch sharks much bigger than Neale as it's quite dangerous for both parties. Designed to be in water, shark organs aren't well supported on land. As the operation is also dangerous for the humans, they've worked out the least stressful way to catch, tag and release.

"By the time we bring them to the boat, they (the sharks that is) are usually tired enough that they're quite will behaved and will sit still," says Barry.The type of tag used requires Neale to come to the surface in order for signal to be picked up by the satellite. The scientists are alerted but don't always wait for the computers to tell them.

"We get too excited in the mornings and we like to dial into the satellite network," says Barry.While CSIRO spends much effort and money tagging and tracking the sharks, they don't neglect what happens after the batteries run down. An important point about the electronic devices is that once they are no longer functioning, the sharks don't need them so they should come off, says Barry. "So we design components into tags that allow them to do so."


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