GPS tracks shark's 1100km journey

SHANE COWLISHAW

ON THE MOVE: Grim, a tagged great white shark is helping scientists learn about its movements at sea.

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The deep-sea secrets of the great white shark are being revealed through a tagging system which has tracked one predator more than 1100 kilometres in 11 days.

Grim, a 2.8-metre great white shark, is the first of its kind to be successfully tagged with a hi-tech GPS system. A Department of Conservation team placed the tag on him off Stewart Island in March.

Late last month he decided to abandon his island lifestyle, bolting into the South Pacific.

Marine biologist Clinton Duffy, who has led the team on Stewart Island for the past five years, said the data being received from Grim's transponder was amazing.

Grim became the second shark to be fixed with a SPOT5 tag after the first attempt in 2007 failed after 18 days.

The tag is drilled into the first dorsal fin and provides accurate position data to 350m every time it breaks the surface.

Duffy said Grim left Stewart Island late on May 28 and by yesterday had travelled 1147km, putting him 350km northeast of the Chatham Islands.

Grim was travelling much farther east than other sharks studied.

While the reason for that remained unknown, the data being received from the tag meant theories about the great white's migration habits could be confirmed or thrown out, Duffy said.

"He's certainly gone a long way east compared to our other sharks and what we don't know is if he's going to turn around out there."

The data would also allow the team to study where the shark stopped on its trip, its speed and its feeding habits, he said.

During the research 46 individual sharks have been identified at Stewart Island.

Many of these were tagged with $5000 pop-up archival tags that are attached to the shark using a long pole.

The chip stores data on depth, temperature and light levels and is useful for long-distance mapping, but cannot record precise locations.

- © Fairfax NZ News