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Fish Diversity Declines in the Deep Oceans

From The Globe and Mail (Canada)

http://www.theglobeandmail.com/servlet/ArticleNews/TPStory/LAC/20050729/PRED
ATOR29/TPEnvironment/

'Hot spot' fish areas being depleted

Dalhousie University researchers release study showing marine-life stocks
declining

By MARK HUME

Friday, July 29, 2005

New research by a Canadian university has brought previously unknown parts
of the world's oceans into focus and is raising new concerns about the
global decline of big species.

The study, released yesterday by the journal Science, found that the ocean
contains a small number of "hot spots" where marine life concentrates and
where stocks are declining dramatically.

But the finding has also opened a new window of hope because it points to a
few key areas, in a vast, featureless ocean, where conservation efforts
could be targeted for maximum effect.

By looking at 50 years of international fishing data for tuna and billfish,
co-authors Boris Worm and Ransom Myers, both of Dalhousie University in
Halifax, were able to map five hot spots of species richness and density in
the world's oceans.

These zones of concentration are clustered mostly in the subtropics where
ocean temperatures, currents, oxygen concentration and food sources
converge, drawing in the bigger predator species.

The five different hot spots are off the coast of Florida, off Australia's
east coast, south of the Hawaiian Islands, east of Sri Lanka and in the
southeastern Pacific.

"The open ocean covers two-thirds of the planet and people usually envision
it as a big, blue area on the map, where you see life only when you come
close to the coastal rims," Dr. Worm said in a telephone interview.

"That's certainly not true. We've shown that the species that you find in
the open ocean, like tuna and billfish, sharks and turtles, they appear to
aggregate in certain areas, we call hot spots."

Dr. Worm said that two years ago he and Dr. Myers noticed areas of richness
in the northwest Atlantic, off Canada's East Coast.

They wondered if that was a phenomenon they would find in other places.

Using decades of fishing data collected by commercial fishing fleets that
were roaming globally, they were able to zero in on the five areas "of great
global importance" that they are now calling hot spots.

"The second thing that astounded us was when we looked back in time, 50
years, using a unique global long lining data set collected by the Japanese
fleet, was that those hot spots are the remnants of much larger areas," Dr.
Worm said.

He said the five hot spots are shrinking, species diversity within them has
declined by 50 per cent, and other hot spots that once existed have
vanished, apparently because of overfishing .

"We could not identify a factor other than fishing that may plausibly
explain long-term, global-scale declines," the researchers state in their
paper.

"It's like a slow-motion disaster," Dr. Worm said of what is happening to
fish stocks in the world's oceans.

"You know, a silent catastrophe which is beyond our reach because we can't
really see it."

Dr. Worm said he hopes the discovery of hot spots will now help the public
focus on the plight of the world's oceans.

"What we're trying to do with this idea of global hot spots is bring it to
people's imaginations in a similar way that rain forests and coral reefs
are," he said.

He said his findings were presented to the United Nations recently and he
was encouraged by how interested fisheries experts were in the hot-spot
data.

"They have a clearly defined goal to put high-seas marine parks into place.
They just don't know where to put them. This points the way.

"This says . . . if you act now you can do something for our common global
heritage . . . It is a hopeful message after all. Some areas are still
there."

In addition to finding that big fish such as tuna aggregate in key areas,
the researchers also discovered that zooplankton concentrates in specific
zones.

Dr. Worm said that new zooplankton discovery came as a shock.

"Well, this was an amazing surprise to us . . . These are the tiniest
animals in the ocean," he said.

"They are single-celled organisms, related to amoeba. They have nothing to
do with large tuna and billfish we studied in the first place - and yet they
showed the same patterns of diversity . . . So that tells us there are some
very general features in the oceans that make certain places extremely
interesting to a wide range of species."

He said it's vital to protect those areas while they still have high
biodiversity.
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