Satellite Tags Keep Track of Great White Sharks

November 11, 2002

When Sean Van Sommeran was a boy, out for a day's fishing with a family friend near Ano Nuevo Island, a mile off the coast northwest of Santa Cruz, California, they saw a great white shark devour an elephant seal.

"That left an impression," said Van Sommeran, a former commercial fisherman and now founder and CEO of the Pelagic Shark Research Foundation in Santa Cruz. "It was back in the mid-seventies, and I'd just seen the movie Jaws and read the book."

Now, in the same area, Van Sommeran comes face to face with great white sharks almost every day in season. His mission is to help scientists better understand the behavior of Carcharadon carcharias by tagging the animals and documenting their movements.

During late summer and early fall, when a large breeding colony of northern elephant seals gathers at Ano Nuevo, great whites—at about 21 feet long and 4,800 pounds—come to feed.

Van Sommeran and his six-person team head out in a launch and maneuver close enough to a shark to reach out with a pole, pierce the skin behind its dorsal fin and attach a metal acoustic or satellite transmitter.

Enticing the Great White

Waves around Ano Nuevo can reach 12 feet. "So, you're in a small boat, big swells, big sharks, you know, what could go wrong?" Van Sommeran said.

"One of the main goals is to find out what the population structures are and where the home bases are," said Heidi Dewar, a marine biologist at the Southwest Fisheries Science Center in La Jolla, California.

"It helps us to know what the sharks are encountering in the wild and if they are going to waters controlled by countries where there's no protection afforded them," she said.

Conservation rules offer limited protection to sharks off California and in some other countries, including Australia, Mexico, and South Africa. Elsewhere, sharks are fair game for fishermen and poachers, some of whom take the animals only for their fins, valued in Asia for shark-fin soup.

Van Sommeran's team entices the white sharks with plywood lures designed to look like a seal from below. "They come up slowly and just sort of nudge the lure," he said. At just the right moment a tagger makes his move.

"Between mid-October and mid-November, sharks spend a lot of time near the coast looking for seals but they really only kill very few before they move on," said Peter Klimley, a marine biologist at the University of California–Davis.

Continued on Next Page >>




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