An example
A Storm is Brewing Over Our Oceans
by Carl Safina and Mercédès Lee
Oceans were the birthplace of life on Earth, and they harbor a
bewildering array of life forms. The seas have long seemed endless
and infinitely bountiful. But overfishing and habitat destruction are
taking their toll, and marine depletions are causing ecological
upheaval, human conflict, and impoverishment.
Overfishing: ClearÂcutting Our Oceans
The frontal assault that is most directly threatening marine life is
overfishing, the clearÂcutting of our world's oceans. Technological
advances over the past few decadesÂÂsonar, radar, satelliteÂassisted
fish finding, huge factory ships that spend months at sea, and nets
large enough to envelop a football fieldÂÂhave changed the
fundamentals of fishing. Exacerbating these overwhelming assaults is
the pressure of more and more boats chasing fewer and fewer fish.
The result is that in many parts of the world, fish populations are at
historic lows.
Fish such as Atlantic salmon, Newfoundland and New England cod,
halibut, haddock, and flounder, have been driven to commercial
extinction. Their numbers are so low that it is no longer profitable (or
legal) to fish for these species in large parts of their range. And
migratory giants such as tunas, swordfish, marlin, and sharks are
facing a similar fate.
For instance, the adult population of Atlantic giant bluefin tuna off the
U.S. east coast has fallen more than 85 percent since the 1970s, but
because they are worth tens of thousands of dollars apiece for sushi in
Tokyo, catch quotas have recently been increased. The breeding
population of Atlantic swordfish is only about 20 percent of what it
was 15 years ago, and 90 percent of swordfish are now caught
before they reach breeding age. Many shark species in the U.S.
Atlantic and Gulf of Mexico have declined 70 to 80 percent in the last
decade due to excessive fishing pressure. The good news here is that
the U.S. government has proposed cutting shark fishing allocations in
half, and if implemented, this could halt their current decline.
Instead of living off the biological interest of wild populations, we
have minedÂÂrather than managedÂÂthe capital. The emphasisÂÂin
thinking, in politics, and in fisheries lawÂÂhas been on economics over
biology. Ironically, overemphasis on shortÂterm economics has
resulted in major economic and social losses to businesses and
taxpayers. Fishery depletions in the U.S. cost $8 billion annually and
300,000 jobs, according to the federal government.
In the twentieth century, ocean fish catches increased 25Âfold,
although catch rates per ton of fishing vessel have been falling since
1970 as fleets and fishing power grewÂÂoften swollen by subsidiesÂÂat
rates greater than the ability of the fisheries to sustain them. In 1989,
the total world catch of wild fish from the seas peaked at a little over
80 million metric tons. It has generally remained static since then,
suggesting that for most areas of the world the limits of the seas have
been reached.
Bycatch: Casualties of Commerce
Virtually every kind of fishery unintentionally catches unwanted
creatures, known as bycatch. Each year, about oneÂquarter to
oneÂthird of the world's total catch is simply discarded overboard,
dead or dying. Indiscriminate fishing techniques cause this waste; this
careless practice also pits fishery against fishery. Shrimp trawlers have
more bykill than any other type of fishing gear: For every pound of
shrimp kept, anywhere from a pound and a half to eight pounds of
sea creatures, many of which are juveniles of commercially important
species such as red snapper, are discarded dead. Shrimp trawls are
the largest source of mortality in adult sea turtles, and in the U.S.,
shrimpers must now have "turtle excluder devices" in their nets to
shunt turtles out. The highest amount of bycatch occurs in the
Northwest Pacific: Nine million metric tons of catch is discarded
annually.
Aside from problems of waste, bycatch can also deplete or endanger
wildlife populations, including fish, sea turtles, birds, and marine
mammals. For example, coastal gillnets threaten certain small dolphins
and seals with extinction, and longlines set for tunas and swordfish are
endangering several albatross species.
Fish Need Habitat, Too
ThreeÂquarters of our recreational and commercial fish and shellfish
species depend on coastal ecosystemsÂÂestuaries, marshes, and
riversÂÂas breeding grounds and nurseries. Yet development
continues to degrade and destroy these essential habitats, threatening
both the health of marine fish populations and the future of fishing
communities. The federal government estimates that ongoing inshore
habitat losses cost the nation's fisheries more than $27 billion annually
in reduced catches.
Fishing practices can also alter fish habitat. In many regions of the
world's continental shelves, bottomÂdwelling animals and plants (many
of which feed and shelter fish) have been seriously damaged by
commercial trawling. Divers throughout the tropical IndoÂPacific
region use cyanide to catch fish, but this also kills their coral habitats.
Even fish farms can destroy essential fish habitat for wild populations
because pens and artificial ponds often replace natural nursery
habitats and pollute local waters. Aquaculture facilities have
destroyed many mangrove tracts in Thailand, Ecuador, and other
areas. The submerged roots of these saltÂtolerant trees provide
essential spawning and larval growth habitat for shrimp and fish. Their
loss not only hurts wildlife populations, it also contributes to
malnourishment of local peopleÂÂthe shrimp and fish grown in the
tropics are almost all exported to developed countries, not used as
local food.
Ecological Effects
The effects of overfishing go beyond straightforward depletion.
Intensive removal of adults can drastically alter a population's age
structures and sex ratios and greatly reduce spawning potential. Adult
removal can even cause genetic changes, including miniaturization
through the disproportional survival and reproduction of small, early
maturing individuals.
In some parts of the world, overfishing is starving fishÂeating birds and
marine mammals. The bestÂstudied example is in Great Britain's
Shetland Islands, where extensive fishing for sandeels depleted this
prey species so severely that Arctic terns, puffins, and other birds that
prey on sandeels failed to breed for nearly a decade, beginning in the
early 1980s.
Selective depletion of marine organisms can cause profound changes
in ecosystem structure. One example can be seen on Georges Bank,
an area off the New England and Newfoundland coasts that has been
jointly overexploited by the U.S. and Canada. The area's
onceÂdominant cod, flounder, and haddock have been replaced by
skates and small sharks called dogfish, resulting in significantly
different patterns of energy flow and fears that the latter species could
suppress recovery of the overfished formerÂdominants. On the other
hand, the longÂlived, slowÂreproducing dogfish, formerly
unmarketable, are now already being rapidly depleted in a new,
unmanaged fishery.
Management Problems
Management of fisheries is fraught with problems. In many regions,
there are no data with which to manage. For example, increasing
demand for shark fins in China has driven many shark populations
around the world to low levels since the 1980s, but quantitative data
on the amount of fish caught, much less on population trends, are
spotty at best. Where data do exist, they have, for the most part,
been disregarded by managers and policymakers. The International
Commission for the Conservation of Atlantic Tunas, for instance, has
never since its inception in the 1960s been in compliance with its
charter obligation to manage for sustainable yields, despite having the
world's best data on regional population trends for tunas and
billfishes. It has made few management recommendations, has
allowed the severe depletion of western Atlantic bluefin tuna and
swordfish, has belatedly set catch limits that are too high to allow
recovery of these species, has allowed overfishing and regional
depletion of other tunas and billfishes, and still has no management or
recovery plans for any species.
A Change In the Wind?
Despite chronic problems, the sea breezes are beginning to shift. In
the U.S., more than 100 conservation, fishing, scientific, and diving
groups banded together to form the Marine Fish Conservation
Network, and at the end of 1995 they achieved a sweeping
Congressional overhaul in federal fisheries law that would have been
unthinkable only three or four years earlier. Implementation of these
major changes should fundamentally improve fisheries management
and marine resource abundance in U.S. waters.
In November 1994, mounting concern about the role that trade plays
in threatening shark species led to the unprecedented decision by
countries that are signatories to the Convention on International Trade
in Endangered Species of Wild Fauna and Flora (CITES) to review
the biological and trade status of sharks globally. This is the first time
that a truly valuable commercial fishery has been accepted into the
CITES agenda, laying the necessary groundwork for regulating trade
in sharks and shark products throughout the world.
The United Nations Food and Agriculture Organization once helped
shepherd the world into its current state of catchÂasÂcatchÂcan frenzy
by encouraging and helping countries to expand their fishing fleets as a
way of increasing economic wealth and independence. Reports from
this world fish authority now ring with ominous warnings and
recommendations, saying that 70 percent of the world's populations
of marine fish, crustaceans, and mollusks are fully fished or have been
overexploited, and that conservation measures must be implemented
to reverse these trends. The United Nations imposed a global ban on
largeÂscale driftnetting in the early 1990s. And in 1995, the U.N.
passed a new treaty on high-seas fishing, which, if implemented in
coming years, may well be the most important action ever taken for
establishing a sustainable regime for the world's fisheries.
The end of a long era of mythical limitlessness and ideological
freedom in the seas is upon us. Does this mark the beginning of better
stewardship and recovery?
Carl Safina is senior ecologist at the National Audubon Society,
and the director of its Living Oceans Program. Mercédès Lee has
been a writer and science editor for the National Audubon
Society for the last 10 years. She is currently outreach
coordinator for Audubon's Living Oceans Program.
(ZooGoer 26(2) 1997. Copyright 1997 Friends of the National
Zoo. All rights reserved.)
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