Scuba Diving club,
Southern California
Sea Sabres
Troubled Seas
Ninety percent of the big fish have
already been caught. Will rampant overfishing cause the ocean’s ecosystems to
collapse? No one knows.
By Fred Guterl
NEWSWEEK
INTERNATIONAL
July 14 issue — Scientists aboard the research ship
Tangaroa had set out from Australia in search of a particular underwater
mountain. It was located in the Norfolk Ridge, out in the middle of the Tasman
Sea, and sonar maps suggested that it was just what they were looking for:
gentle slopes free of rocks and crags, and a peak that rose to within 2,000
meters of the water’s surface. But on day five of the voyage, the seas were
rough and the seamount was nowhere to be found. Reluctantly, they decided to explore
another underwater mountain. They lowered their “dredge”—a metal box with a net
lining—and began dragging it up the slope. Immediately it snagged. “The bottom
is very hard and deceptively flat but fractured with fissures and valleys that
are nearly impossible to tow our gear over,” reads the log entry for 11 a.m. on
May 14.
THAT
DAY THE CREW managed to pull up a small haul of creatures—spider fish and
long-legged crabs and others known to frequent seamounts. Two of them looked
especially odd: a dragonfish, less than seven centimeters long, that had a
barbel-like protrusion on its chin with a light organ at its tip, probably for
attracting prey; and a type of grenadier fish with distinctive markings and
coloration. That evening, an addendum to the ship’s log referred to “two
species new to science.”
New to science—the phrase is usually accompanied by
the sound of popping corks. But marine biologists are spoiled for diversity:
the Australians and New Zealanders on the Tangaroa came back with more than 100
possibly new species. That’s less a sign of the ocean’s profusion than of our
ignorance: scientists know shockingly little about what makes the oceans tick.
Only in the past decade or so have marine biologists taken an interest in
seamounts, where strong currents bearing precious nutrients and oxygen tend to
support abundant marine life; of thousands scattered throughout the world’s
oceans, they’ve visited only a handful.
The
problem is that what we do know is frightening. While the Tangaroa was plying
the Tasman Sea, Canadian biologists Ransom Myers and Boris Worm of Dalhousie
University in Halifax were publishing, in the journal Nature, the latest and
most comprehensive estimate of the state of the world’s fisheries. Scientists
have known for more than a decade that fish are being removed from the ocean
faster than they can replenish themselves. But Myers and Worm have now attached
a shocking figure to the debate: in the past 50 years, they say, overfishing
has removed nine of 10 large predators—the big fish like tuna and cod.
Scientists have sounded similar alarms for years, but always about this fishery
or that—the North Atlantic in the 1980s, the North Sea and the waters off Japan
in the 1990s and, more recently, western Africa. This time, the data is global.
“The beauty of the paper is that it has a nice, round number,” says Jeremy
Jackson, a scientist at the Scripps Institution of Oceanography in San Diego.
“Ninety percent of the world’s fish are gone. Anybody can understand that.”
Can we? Ask most marine biologists, and they’ll
tell you that the more they learn about the oceans, the less they know.
Eliminating predatory fish is bound to have wide-ranging repercussions. “You
can’t just remove the top layer of an ecosystem without having a knock-on
effect,” says Larry Crowder, a Duke University biologist. As a worst-case
scenario, it could eventually turn the oceans into deserts. But this is
unexplored territory, and scientists are fumbling around like the Tangaroa with
its dredge. “What would the oceans be like without predators?” says Barbara
Block, a marine biologist at Stanford University. “It’s like asking what Africa
would be without lions. What it means is almost completely unknown right now.”
What’s undisputed is the need to answer this question, and soon—not least to
build the political case for preserving the last earthly frontier.
If you didn’t know where to look, the deep oceans
might seem to be almost devoid of life. Beyond the narrow continental shelves,
the ocean bottom drops to tens of thousands of meters. At such depths,
pressures reach 1,000 atmospheres—enough to compress a human body down to the
size of a doll. Be-cause the sun’s rays can’t penetrate beyond a few meters of
seawater, energy and nutrients at the ocean floor are few and far between.
Bottom dwellers, like sea cucumbers, clams and bristle worms, live slow,
monotonous lives of minimal activity.
As if to make up for this dreary vastness, the
oceans support the occasional oasis. Warm currents—like the Gulf Stream in the
Atlantic, or the Kuroshio Current off Japan—collide with cooler water, creating
a discontinuity, like oil and water, that traps tiny phytoplankton. Zooplankton
arrive to eat them, small fish come to eat the zooplankton and the big fish,
the turtles, the seabirds follow in turn. A similar proliferation occurs on
seamounts, on the continental shelves and at upwellings of cold water from the
deep. The paucity of sunlight, nutrients and oxygen—the very thing that makes
the ocean so forbidding—also imposes a structure on marine life.
The propensity of life to congregate is one reason
scientists worry about overfishing. The oceans may be vast, but the number of
oases is finite. In the Grand Banks in the northern Atlantic, for instance, cod
were plentiful a hundred years ago. Then fishing trawlers came in the early
20th century and, 50 years later, factory trawlers—mammoth ships that can net,
fillet and freeze enormous amounts of fish. In a few decades, the fisheries
were depleted. In 1992 the Canadian government was forced to impose a
moratorium on cod fishing, but in 11 years the cod have not come back. Nobody
knows why.
With the decline of shallow-bottom feeders like cod
and halibut, the fishing industry has redoubled its efforts in the open oceans.
The preferred method is so-called longline fishing, which entails stringing out
lines, supported by buoys, that stretch tens of miles over the water’s surface,
and attaching other lines with baited hooks. The technique is particularly
effective for tuna, billfish and swordfish. (It also nabs sea turtles, sharks
and albatrosses, and is a major factor in the decline of these animals.) Myers
and Worm studied historical data from longline fish-ing going back more than 50
years and found that catch rates for all types of fish had dropped more
precipitously than scientists previously thought.
The report is the first documented decline of
predators throughout both coastal and deep ocean waters. Stanford’s Block
thinks that’s not merely a question of fishermen ranging farther afield. Since
1996 she has studied the migratory patterns of tuna and sharks, tracking them
with satellite transponders. She’s found that unlike cod, tuna and sharks don’t
confine themselves to any one area. Sharks off the western United States have
been observed swimming the 3,700km to Hawaii. Block once traced an Atlantic
bluefin tuna as far north as Iceland, as far south as the Caribbean, and even
to the Mediterranean. “We cannot tell you where almost any of these species go
to feed or breed,” she says.
On the one hand, that means the oceans are
interrelated—and thus that the removal of predators can have far-reaching
effects. But it reveals nothing about the lower layers of the food chain.
Scientists have only piecemeal examples of what happens when marine eco-systems
become unbalanced. The collapse of the cod fisheries in the North Atlantic has
been a boon to shrimp and sea urchins, the cod’s prey. It’s given urchins free
rein to devour the kelp forests, turning vast stretches of the sea floor into
“urchin barrens.” In a study of coastal ecosystems two years ago, Jackson found
overfishing of predators, rather than pollution and global warming, to be the
probable cause of oceanic “dead zones”—areas of complete ecosystem collapse,
where microbes fill the void left by fish and invertebrates.
Dead zones are found in the Gulf of Mexico,
Chesapeake Bay and the Baltic and Adriatic seas, and they’re spreading to the
open oceans. Coral reefs in the Caribbean have been hurt by overfishing of
algae-eating fish, such as parrot fish. Sea urchins took up the slack for
years, but when a disease outbreak wiped them out the corals grew fuzzy and
green with algae, and died.
Since so little is known about marine ecosystems,
scientists are reluctant to speculate where all this might lead. It doesn’t
take much imagination, though, to extrapolate from what we do know. If
overfishing continues for the big predators, it’s possible that many of them
may fall below a critical mass and lose the ability to reproduce, sending
populations into a downward spiral. That would throw millions of people who
depend on the fishing industry out of work. If the cod and herring fisheries
are any guide, the damage would take decades to reverse. It would be a global
crisis; treaties would be signed; —the United Nations would be granted the
power to enforce fishing bans—and we’d all wait out the decades hoping the fish
would return. But they might not, ever. The removal of so many big fish could
have a ripple effect, killing off invertebrate and microbial life forms we
haven’t even heard of yet, but which serve as essential links in the food web.
How long would it take—50 years? 100?—to find that cod, tuna, halibut,
mackerel, marlin and other big fish were creatures only of farms or museums?
This
is speculation, but it isn’t idle speculation. The Myers and Worm data may be
telling us that a global catastrophe is already underway. It sounds laughable
to put it this way. It would have been laughable, too, to suggest a hundred
years ago that fishermen would someday catch the last Atlantic cod. Cod, as
everybody knew, was as close to a limitless resource as you could get. Maybe
then. But tens of thousands of unemployed Canadian fishermen have been waiting
a decade for the cod to return to the waters of Labrador and Newfoundland.
Earlier this year, Canada put the Atlantic cod on its endangered-species list.
The public hasn’t much noticed the decline. More
fish are being raised on farms, and fishing boats have pushed farther and
deeper in chase of a dwindling catch. The dearth of tuna isn’t yet reflected in
the price of a tuna sandwich. But the decline is having some impact. Mahi-mahi
has appeared on the menus of Western restaurants, as a replacement for
swordfish. Fishing boats are plying treacherous Antarctic waters for the
Patagonian toothfish, known by its more salubrious moniker, Chilean sea bass.
Relatively simple fixes, such as enforceable quotas
on fishing nations, could halt the damage to the world’s fisheries. The problem
is, the oceans are largely a free-for-all. “We manage fish on a
species-by-species basis and we manage on a crisis basis,” says Leon Panetta,
who headed the Pew Charitable Trust’s recent report on the world’s fisheries.
“We have to approach the management of all fisheries in an ecosystem type of
approach.” And yet, neither the United Nations nor the big environmental groups
have found an effective way to address overfishing.
Barring drastic action, the world is headed for an
environmental disaster whose proportions are unknown. “What’s most depressing,”
says Jackson, “is there’s no new frontier. The ocean has had it.” And we may
never know what we’re missing.
Fish Farm Issues
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Posted July 15, 2003