Thursday, 3 November 2016

How did Sophie the shark elude scientists?

Scientists who sought to solve mysteries about hammerhead sharks were only left with another when one of the first adults ever tagged ended up eluding them.
Last week, eight months after the smooth hammerhead shark was caught and tagged in the Hauraki Gulf, the electronic pop-up tag started transmitting data back via satellite.

But they soon discovered the 3.2m shark, named Sophie, had long since shed the device.
Sophie was hooked at Simpsons Rock, near the Mokohinau Islands, by long-time research collaborators and Auckland fishers Scott and Sue Tindale.

Finding an adult smooth hammerhead shark had been a coup; while previous studies had successfully tracked juveniles, only one other adult in the species had ever been tagged with an electronic tag, and was thought to have died soon after.

"They're hard to find, they're hard to tag and they're quite susceptible to stress and handling," National Institute of Water and Atmosphere (Niwa) marine scientist Dr Malcolm Francis said.
"Elsewhere in the world, it's been found that hammerheads die a lot more easily after capture than a lot of other sharks do."

The scientists had been optimistic about Sophie, which proved a challenge to tag and appeared to be healthy and lively when released.

For Francis - whose Government-funded research has led to stunning new insights into the behaviour and range of hammerhead, mako and great white sharks - the tag presented the first real opportunity to learn where adult smooth hammerhead sharks travel over a year, and why.

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