Satellite Tags Show White Sharks Migrate Far and Fast

PERTH, Western Australia, October 13, 2003 (ENS) - The recent stranding of a pod of sperm whales off the southern coast of Western Australia attracted white sharks and also attracted scientists from the country's government research branch eager to try a new method of tagging.

Six white sharks were tagged by scientists using new tagging poles that allowed them to place tags on the fish while they were in the water next to the vessel. Previously, scientsts had to capture sharks and bring them aboard a vessel for tagging.

"We receive reports of white sharks from several locations in Western Australia, but the trick is to be in the right place and at the right time," said CSIRO's Barry Bruce of the Commonweath Scientific, Industrial Research Organization (CSIRO).

"It's sad to see the death of a whale pod," said Bruce, "but sharks play an important role in returning the energy and nutrients from the carcases back to the marine ecosystem and are naturally attracted to such an event."

"The sharks ranged from two meters to more than four meters," says project leader John Stevens of CSIRO, who is now waiting to receive signals from the electronic tags.

Shark with a tag attached to its fin (Photo courtesy CSIRO)

Two pop-off archival (PAT) tags and two satellite tracking tags were attached to sharks. PAT tags store information on shark movement and behavior for several months before releasing from the shark, floating to the surface and transmitting their information via satellite.

Satellite tags transmit a unique signal to polar orbiting satellites fitted with ARGOS receivers - a network developed for scientific animal tracking studies. The tags are fitted to the shark’s triangular dorsal fin and transmit when the fin is clear of the water.

Satellite fixes can be accurate to within 150 meters (500 feet) and the sharks can be tracked worldwide. Signals from the satellite tags can generally be decoded to provide a position for the shark about two to six hours after it surfaces.

The shark tagging team - assisted by staff from the Aquarium of Western Australia (AQWA) and local cinematographers David Riggs and Jennene Paris - spent three days east of Bremer Bay, the site of a recent stranding of sperm whales. They were aboard Quadrant, a commercial fishing vessel.

"Getting a tag onto a thousand kilogram shark is quite a task," said Stevens, "even though technology to track animals by satellite has been around for more than a decade. And there are many things that have to go right even after tags are placed on sharks."

"The tag has to stay on, delicate electronics need to survive the rigors of being on a shark during its daily activities, and the sharks need to surface so that the tags can transmit signals," he said.

A three meter (10 foot) long female white shark PAT tagged this year by the team was estimated to have travelled at least 1,300 kilometers (800 miles) along the southern coast of Western Australia between May and June.

The tagging was funded by the AQWA Research Foundation, as part of a project on white shark movement patterns off southern Australia.

This was the team's third attempt to locate and tag white sharks in Western Australia. The tagging trip was carried out under permits from the Western Australia Department of Conservation and Land Management and Western Australia Fisheries.

The CSIRO team achieved a world first two years ago when tracking tags were successfully attached to two small white sharks off eastern Australia and traced for up to four months.

The scientists want to learn how far and fast white sharks travel, what areas are important to them and why, when they visit particular areas, and how long they stay.

The researchers also are attempting to determine whether their movements are linked to those of other species, such as whales or snapper.

White sharks exist worldwide, but despite their widespread distribution little is understood about their biology and ecology, and their populations are known to be dwindling.

In response to these concerns, white sharks are protected in Australia, South Africa, California, Florida, the Maldives, Namibia, the Mediterranean Sea, and Malta.