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If bottom trawling happened on land instead of at sea, someplace where we could see it and where cameras could film it, perhaps it would provoke the same sort of public outcry that strip-mining does. But unlike the raw, torn earth laid bare by strip-mining, the similar devastation of the ocean floor caused by bottom trawling is hidden beneath thousands of feet of water. In some cases, the damage could be irreparable.

Bottom trawlers drag giant weighted nets along the ocean floor, ripping up or scooping out whatever they encounter, including ancient coral forests, gardens of anemones and entire fields of sea sponges. Unwanted and undersized fish hauled up by bottom trawlers are thrown back dead or dying -- in some areas, as many as four pounds of fish are discarded for every one pound brought to market.

Today's technology is bringing bottom trawlers into areas ships couldn't reach before. Trawling nets, huge weighted bags, can be 200 feet wide and 40 feet high, weigh as much as 1,000 pounds, and can be sunk to depths of 5,000 feet or more beneath the water's surface. Heavier, stronger gear allows trawl nets to plow over rocky bottoms, destroying the underwater corals, sponges and rock structures that provide important habitat for fish. Advanced navigation technology brings trawl nets deeper and farther from shore, into areas populated with slow-growing deep-sea fish and corals, which are especially slow to recover from repeated trawling.

Bottom Trawling in International Waters

On the high seas, unregulated bottom trawlers operating in waters well off the coast are laying waste to huge swaths of the ocean floor. Seamounts -- volcanic mountains and hills that rise from the ocean floor but do not break the surface -- are being damaged by these industrial fishing practices, and the wealth of flora and fauna clustered around sea mounts is being wiped out in the process. Many rare, ancient and even unknown species -- some of which hold promise for biomedical research or are critical to undersea biodiversity -- are at risk, including:

  • Cold-water corals, which are as exotic and colorful as their warm-water counterparts. Red tree corals form ancient forests, stretching up to 7 feet tall and 25 feet wide, providing shelter for fish, shellfish, and sea stars. Corals on seamounts can live up to 8,000 years and tend to take branching, tree-like forms, making them particularly susceptible to trawl damage.
  • Sponges, which form giant fields in the deep, creating stretches of habitat up to a mile long and 50 feet high.
  • Fish, including orange roughy, which take decades to mature and can live for 125 years.
  • New species of flora and fauna tucked away on seamounts and other deep-sea habitats. Just like the creatures of the Galapagos Islands, many seamount species have evolved in isolation, resulting in unique species. Scientists studying a cluster of seamounts near New Caledonia have determined that nearly one-third of the species there have never been seen anywhere else.
  • Novel chemical compounds that hold promise for the treatment of cancer and other diseases after their discovery by scientists investigating the biomedical properties of deep-sea organisms.

Bottom Trawling in U.S. Waters

Closer to U.S. shores, bottom trawling can be just as destructive. Bottom trawlers have taken a huge toll on sport and commercial fish such as Pacific rockfish, a family of more than 60 species of colorful fish uniquely adapted to the rocky reefs, rugged canyons, pinnacles and kelp forests of the Pacific coast. Marketed as Pacific red snapper or as rock cod, they are popular with fishermen and diners. Once greatly abundant, several populations are now so depleted that scientists consider them at risk of extinction.

Rockfish have several characteristics that make them susceptible to overfishing, and particularly to bottom trawling. Some rockfish species live as long as 100 years, are slow to mature and may reproduce successfully only once a decade. Because different species school together, powerful trawl gear catches the vulnerable types along with the more productive, and these deep-dwelling fish cannot survive the trauma of being brought to the surface and then tossed overboard.


As is the case in so many areas of ocean protection, the current patchwork of state, federal and international regulations is inadequate to the challenge of preserving the species and habitat near the ocean floors from bottom trawling. NRDC is helping to advance comprehensive oceans legislation on both the federal and state level that can protect and enhance the overall health of our oceans, and is also pushing for an international moratorium on unregulated bottom trawling in the high seas. In California, for example, NRDC helped pass a law restricting bottom trawling by state-managed trawl fisheries in vulnerable habitats.

Some temporary protective measures are demonstrating that there is potential for fish populations to recover. In 2002, to rebuild depressed rockfish populations, the Pacific Fishery Management Council put large ocean areas off limits to bottom trawling and other types of fishing on the ocean floor. These area closures have created a kind of refuge for depleted populations. West coast trawlers have also initiated a program to reduce the size of their fleet by buying and retiring boats of willing sellers.

On the opposite coast, the U.S. government closed several areas of New England's Georges Bank and the Mid-Atlantic to all fishing except lobster traps in an effort to shore up plummeting cod and haddock stocks. For nearly five years, more than 6,500 square miles of Georges Bank's sea floor were undisturbed, helping key fish stocks, including several of the area's haddock and yellowtail flounder stocks, to start rebounding. Other marine species benefited as well. Once-depleted scallop stocks resurged inside the closed areas, leading to a financial bonanza for the fishing industry when some of these areas were reopened for rotational scalloping (New England scallop landings have more than doubled over the last six years). In the areas still closed, scientists have identified increases in crabs, anemones, sea urchins and other invertebrates. However, New England's signature groundfish -- the cod -- continues to struggle, particularly on Georges Bank. Restoration may take decades. Maintaining closures large enough and long enough to be effective and halting fishing when discard limits are reached will be critical in restoring healthy fish populations and the livelihoods of fishermen who depend on them, as well as fully-functioning and diverse marine ecosystems.

International waters deserve protection as well. The international high seas cover half the planet's surface, yet only a handful of international fisheries management organizations have the authority to regulate bottom trawling, and few, if any, have acted to protect sensitive ecosystems. Without adequate regulation, countless species, habitats and possibly entire ecosystems may disappear before they can even be identified.

In keeping with the recommendation of more than 1,000 scientists around the world, NRDC and other environmental groups are pressing the United Nations General Assembly and international fisheries management authorities to adopt an immediate moratorium on unregulated bottom trawling in international waters until these vital, sensitive areas can be identified and enforceable regulations to protect them can be adopted.

Photos courtesy NOAA/MBARI.

last revised 2/1/2007

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