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VARIETY OF OCEAN'S FISH DOWN BY HALF, STUDY SAYS
By Juliet Eilperin
Washington Post
July 29, 2005

http://www.startribune.com/stories/484/5531995.html

WASHINGTON, D.C. -- The variety of species in the world's oceans has dropped
by as much as 50 percent in the past 50 years, according to a paper
published today in the journal Science.

A combination of overfishing, habitat destruction and climate change has
narrowed the range of fish across the globe, wrote biologists Boris Worm and
Ransom Myers of Dalhousie University in Nova Scotia and three other
scientists.

In some areas, such as the ocean off northwest Australia where a wide
variety of tuna and billfish used to thrive, diversity has declined
precipitously.

"Where you used to put out a fishing line 50 years ago and catch 10 species,
now you catch five species for the same amount of effort," Worm said
Thursday. "That's a recipe for ecological collapse and disaster."

The study, which marks the first worldwide mapping of predatory fish
diversity, identified five remaining spots that still have a rich variety of
species, two of them in U.S. waters: the east coast of Florida, south of
Hawaii, near Australia's Great Barrier Reef, near Sri Lanka and in the South
Pacific.

"These areas are really of global significance," Worm said. "It's really
important to protect them now, because 20 years from now they may not be
there."

The total catch for tuna and billfish has increased as much as tenfold over
the past 50 years, prompting fish diversity to plummet, researchers said.
Overfishing is the main reason, but inadvertent catches of other fish also
factors in, Worm said.

The study also found that, in the Pacific, the variety of fish increased
when the weather pattern known as El Niño swept in and brought warmer
surface water, but then contracted when temperatures dropped.

Predatory fish appear to like medium temperatures around 77 degrees
Fahrenheit, Myers said. "Like Goldilocks and the three bears, ocean animals
don't like it too hot or too cold, they like it just right."

To conduct the study, Worm and Myers -- along with Marcel Sandow and Andreas
Oschlies of Germany's Leibniz Institute for Marine Science and Heike Lotze
of Britain's National Oceanography Centre -- used data from Japanese
long-line fisheries going back to the 1950s, which they cross-referenced
with scientific observer data from the United States and Australia.

The researchers determined that tuna and billfish are indicators of wider
ocean diversity and that these species are disappearing in many areas.
Mid-size predators -- snake mackerel and pelagic stingrays -- are taking
their place.

Worm compared the diminishing range of species to a poorly distributed stock
portfolio that's ill-equipped to respond to economic and environmental
shifts.

"As [fishing] markets change, as the climate changes, you have nothing to
fall back on," he said.

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Published by David Sunfellow
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