Scientists keep tabs on great white sharks

Scientists have spent a decade studying the movements and behaviour of great white sharks in New Zealand waters.

Since 2005, in the joint Niwa and Department of Conservation project, 95 sharks have been tagged and tracked, mainly off the Chatham Islands and Stewart Island.

The project’s aim was to find out how mobile the sharks were, how far they travelled and where, and their habitat requirements, Niwa fisheries scientist and shark expert Dr Malcolm Francis said.

The data would be compared with commercial fishing distribution data to figure out where and when the sharks were at the greatest risk of being inadvertently caught by fishing gear.

Researchers found most great whites migrated to the tropics during winter.

‘‘They go between May and July and return between December and March, spending more time out of New Zealand waters than in,’’ Francis said.

New Zealand tagging showed the sharks travelled in a straight line on their migrations, averaging about 100 kilometres a day.

In the afternoons they tended to spend time at the sea’s surface, but also made regular dives of between 200 metres and 800m. The record depth a great white reached was 1246m.