http://story.news.yahoo.com/news?tmpl=story&u=/ap/20030116/ap_on_re_us/shark_populations_1
Study
Shows Shark Species Are Threatened
Thu Jan 16, 2003, 2:00 PM ET
By PAUL RECER, AP Science
Writer
WASHINGTON
- North Atlantic shark populations have declined by more
than 50 percent in the past 15 years, with some species approaching
the point of no return due to relentless fishing pressure and
scant
international efforts to protect the toothy ocean predator, researchers
say.
A study in Friday's
issue of the journal Science found that longline
fishermen harvesting tuna and swordfish from the Atlantic and
adjacent
waters are killing huge numbers of hammerhead, great white, tiger
and
thresher sharks. This is consistent with other studies suggesting
a
decline in shark numbers in all of the world's oceans.
A team of researchers
at Dalhousie University analyzed the logbooks
of longline fishing fleets from 1986 to 2000 and found a sharp
drop
in the number of sharks killed while harvesting tuna and swordfish.
"We estimate
that all recorded shark species, with the exception of
makos, have declined by more than 50 percent in the past eight
to
15 years," the researchers found.
"This is a worldwide
phenomenon," said Ransom A. Myers, a professor
of biology at Dalhousie and a co-author of the study. "There
are
only a few areas in the world where we have good data, but wherever
we do, they show the same thing — the shark is in serious
decline."
The study found
that hammerhead sharks declined by 89 percent in the
Atlantic, while tiger sharks were reduced by 65 percent, blue
sharks
by 60 percent and threshers by about 80 percent. The trend for
great
white sharks, the famed predator in the movie "Jaws,"
is a decline
by about 79 percent. The study found that in at least two fishing
areas, no great white has been recorded since the early 1990s.
Myers said the shark
is particularly threatened by intense fishing
pressure because the animal cannot quickly replace its lost numbers.
"They are like
humans," he said. "They take a long time to mature
and have relatively few babies. The bigger sharks have only about
four pups a year. That makes them more vulnerable than other fish
species."
Although sharks in
some parts of the world are targets of fishermen,
in the North Atlantic they fall victim to fleets seeking other
types
of catch.
"The hammerheads
concentrate in exactly the same places where the
fleets fish for tuna and swordfish so they are hit because they
are
at the wrong place at the wrong time," said Myers. The sharks
routinely
feed on the herring and squid commonly used for bait by the longliner
fishermen, he said, so catching sharks is just a routine part
of
fishing for the other species.
Myers said sharks could
be protected by changing the commercial
fishing patterns. For instance, some of the sharks migrate along
set paths at specific times of the year. Prohibiting fishing during
those periods in the migration areas could reduce the by-catch
of
sharks, he said.
Also, establishing
refuges where all fishing was forbidden would
give sharks, along with other fish, a safe haven where they could
feed and reproduce safely. This eventually would mean bigger catches
for the fishing fleets, said Myers, and protection for the sharks.
"The shark is
declining now, there is no reason to believe
they would not recover if we fished in a responsible manner,"
he said.
The United States now
forbids harvesting of shark fins for
shark fin soup, a favorite in Asia, but longline fleets from
Spain and Japan continue to harvest, said Myers. In a recent
meeting of the Convention of International Trade in Endangered
Species of the United Nations (news - web sites), Japan, a major
shark-consuming nation with a vast fishing fleet, led a successful
effort to defeat proposals that called for protection of two shark
species.
David O. Conover, a
professor at the Marine Sciences Research Center
at the State University of New York, Stony Brook, and an expert
on
fisheries, said the Dalhousie study shows "a particularly
clear and
compelling example where a group of species that are by-catch
in
commercial fishing are suffering a decline that has gone unrecorded."
Conover said the shark
is at the top of the food chain in the ocean
and if that species were to be wiped out by overfishing it could
disrupt
the entire ecosystem of the oceans.
"We
know from many examples that once you start eliminating the predators
at the top it has a ripple effect throughout the food web,"
said Conover.
"It is difficult to predict what would happen, but we know
there are
major effects in altering the food web."
