Last Updated: January 02, 2002 05:54 PM ET
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By Andrew Quinn
SAN FRANCISCO (Reuters) - The great white shark,
immortalized as one of the world's most awesome predators in the
movie "Jaws," has long been considered a relative homebody --
hunting in a narrow band of coastal waters and rarely venturing far
from shore.
Now, a new study
released on Wednesday shows that these massive sharks are actually
world travelers, with some swimming thousands of miles into the open
ocean on mysterious migrations that broadly expand the powerful
carnivores' range across the globe.
"I was shocked by the results," said Burney Le
Boeuf, a biologist at the University of California-Santa Cruz and
one of the authors of the new study published in the Jan. 3 edition
of the journal Nature.
"Going
in to this, what we expected was that white sharks were just coastal
animals that breed in Southern California, then migrate a few
hundred miles north to feed on seals. But it turns out they've got a
life at sea, and when they're in the open ocean, they're diving very
deep at times."
The study by
scientists at UCSC and Stanford University used electronic tagging
to track six adult sharks via satellite -- revealing a surprisingly
broad range for one of the most feared and misunderstood creatures
of the deep.
One male shark
tagged by the team swam all the way from the California coast to the
warm waters off Hawaii, a journey of some 2,280 miles.
The world's largest predatory fish,
the great white can grow up to 21 feet in length and weigh as much
as 4,800 pounds.
Usually
found in temperate offshore waters ranging from California to
Australia, Southern Africa and beyond, the great white has been
tracked most frequently around coastal colonies of seals and sea
lions which form the basis of its diet.
But the migration patterns and environmental
preferences of the sharks have remained elusive, increasing the
mystery surrounding the giant hunter sometimes dubbed "white
death."
"Terrestrial
creatures have a lot of trouble understanding these big fish," said
Barbara Block, a professor of biology at Stanford University's
Hopkins Marine Station.
"But
what we are seeing is that this is a cosmopolitan species ... they
go where they want to go."
The California scientists attached "pop up"
satellite archival tags to the backs of six adult sharks as they fed
near seal rookeries in coastal California in 1999 and 2000.
The electronic tags recorded data
every two minutes on the sharks' environment, including water depth,
temperature and light, giving researchers the ability to pinpoint
its location at any given time.
Each tag was programmed to detach from the animal
on a specific date and "pop up" to the surface, where its data was
transmitted via satellite to scientists onshore.
HEADING FOR WARMER WATERS
The initial data on the sharks'
movements confirmed that they remained close to shore during the
North American autumn, arriving at California seal habitats just as
young elephant seals gather -- making them easy prey.
During this period, the tagged
sharks rarely dove more than 90 feet below the surface and remained
in temperate waters ranging between 50 and 57 degrees
Fahrenheit.
The surprise came
in the winter, when four of the tagged sharks headed away from the
coast.
One male shark
migrated all the way from the Farrallones off San Francisco to near
the Hawaiian island of Maui -- where great whites have been rarely
sighted -- traveling at least 43 miles per day and remaining in the
warm Hawaiian waters until the Spring. It then swam all the way
back.
Three other tagged
sharks migrated to subtropical waters in the eastern Pacific
hundreds of miles west of Baja California, and then remained in the
open ocean for months.
"What
they were doing out there is a mystery," Le Boeuf said, adding that
the trip may represent part of the sharks' mating process or search
for new prey.
Block said the
shark data would be supplemented by a broader tagging program in
which scientists working with the Global Census of Marine Life will
monitor some 4,000 fish, birds, mammals and large squid to gain a
clearer picture of migration patterns in the deep.
"This is just the tip of the
iceberg," Block said. "We don't know where these predacious fish go,
where they breed or where they feed. This technology gives us a new
view."
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