A Storm is Brewing Over Our Oceans
by Carl Safina and Mercds 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: Clearcutting Our Oceans
The frontal assault that is most directly threatening marine life is overfishing, the clearcutting of our world's oceans. Technological advances over the past few decadessonar, radar, satelliteassisted fish finding, huge factory ships that spend months at sea, and nets large enough to envelop a football fieldhave 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 minedrather than managedthe capital. The emphasisin thinking, in politics, and in fisheries lawhas been on economics over biology. Ironically, overemphasis on shortterm 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 25fold, although catch rates per ton of fishing vessel have been falling since 1970 as fleets and fishing power grewoften swollen by subsidiesat 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 onequarter to onethird 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
Threequarters of our recreational and commercial fish and shellfish species depend on coastal ecosystemsestuaries, marshes, and riversas 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, bottomdwelling animals and plants (many of which feed and shelter fish) have been seriously damaged by commercial trawling. Divers throughout the tropical IndoPacific 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 salttolerant 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 peoplethe 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 fisheating birds and marine mammals. The beststudied 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 oncedominant 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 formerdominants. On the other hand, the longlived, slowreproducing 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 catchascatchcan 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 largescale 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. Mercds 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.)
