Shark numbers down by 50-percent
From the Associated Press
http://capmel.com/shark_numbers_down.htm.
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.
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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, 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.''
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Shark Numbers Down by 50 Per Cent
1. What is a mako?
2. In what way are sharks like humans?
3. Which type of shark has declined the most?
4. What is the difference between the reasons for shark killings in the
North Atlantic and in other areas?
5. What is the regular food of the hammerhead shark?
6. Give two ways in which fishing methods could be changed to protect
the sharks.
7. Which country has not cooperated with the Convention of
International Trade in Endangered Species?
8. What is meant by a by-catch?
9. What could happen if the sharks were overfished?
Write:
Sharks are being overfished. What are the causes and effects of this?
4ef08b58-3e13-4e2a-a457-cca96bc4ce7c.doc 12/3/2011 5:37:00 PM