Satellites Spy on Lives of Great White Sharks

September 22, 2003

Last May, a small fishing boat plied the waters of Mossel Bay, South Africa, in pursuit of great white sharks. Scientists hooked a seven- footer, fought the fish for a couple of minutes until it calmed, then towed it towards the 100-foot (30-meter) research vessel that waited nearby. The team onboard guided the shark into a metal crib, and hoisted it on deck with a hydraulic lift.

Marine biologist Ramon Bonfil and four South African colleagues leaped into the crib with the shark, steering clear of its fearsome jaws. After quickly covering its eyes, they power-drilled small holes in the animal's dorsal fin and bolted on a small satellite transmitter.

A veterinarian pumped water over the animal's gills and administered antibiotics and vitamins to counteract the stress of capture. Others measured and sexed the animal—and in under five minutes, the shark was back in the water, swimming away.

"We were like a Formula One pit crew," said Bonfil, a shark expert with the Wildlife Conservation Society in New York City who heads the project.

The team tagged eight sharks with "real time" transmitters. These instruments track the sharks' day-to-day movements for three to six months, sending the data to Bonfil's laptop via email each time their fin breaks the surface. "They're very large animals, so potentially they can swim very long distances, but do they?" asks Bonfil.

Mysterious Fish

The great white shark is the largest predatory fish, much-feared and greatly maligned by humans. But despite their notoriety, little is known about their basic biology or habits, their numbers, where they go—where they mate and birth their young remains a mystery.

To answer these questions, scientists are using two types of satellite transmitters to track the whereabouts of great white sharks from each of the world's hotspots: South Africa, California, and Australia.

In 2002, he began tagging sharks in collaboration with the South African government and the Universities of Cape Town and Pretoria, originally fitting 16 sharks with pop-up tags. The team will return in November to fit another 26 sharks with both types of transmitters.

A second type of transmitter, a pop-up archival tag, is easier to attach and gives scientists different information. From aboard ship, it is darted into a shark's back. This tag collects data on water temperature, dive depth, and light levels once every minute for up to 12 months. Then it is electronically detached from the shark. When it floats to the surface, it uploads the data, along with its position, to a French satellite—which is then beamed to scientists' computers.

State of the White

Shark populations have declined over recent decades. Sharks first appeared in ancient oceans 400 million years ago, evolving into apex predators, but they are not able to withstand predation today by humans.

Continued on Next Page >>




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