SUNS 4346 Wednesday 16 December 1998



ENVIRONMENT: OCEAN TRAWLING WORSE THAN FOREST CLEARCUTTING

Washington, Dec. 14 (IPS/Danielle Knight) -- Bottom trawling and dredging, two widespread but under-studied methods of commercial fishing, are the most destructive human activity affecting the world's oceans, according to new scientific studies released Monday.

Comparing the fishing techniques to forest clearcutting, a series of articles published in the scientific journal Conservation Biology warns that the living structures of seabeds are being destroyed at a rate much greater the current rate of destruction of the earth's forests.

"Our most startling finding is that the area of seabed trawled each year is nearly 150 times the area of forest that is clearcut," says Elliot Norse, president of the Marine Conservation Biology Institute
based in Washington state, who is one of the principle authors of the studies.

"Each year, trawlers drag an area of seabed twice the size of the continental United States," he says. "We are doing more to the surface of the earth by trawling than perhaps any other human activity except agriculture."

Like a forest, the sea bed is a complex ecosystem that provide habitat and food essential for the reproduction and growth of fisheries and other marine life. Trawling and dredging destroys these structures - which can take decades and even centuries to fully recover, according to the studies.

"After trawling sponges, mussels, tube-dwelling worms and the crustaceans that live in undisturbed areas are almost all gone," says Les Watling, professor of oceanography at the University of Maine and one of the other authors of study. "Nothing humans do to the sea has more physical impact."

>From icy subpolar regions to the tropics, trawling is one of the most widespread commercial fishing methods in the world.

Bottom trawlers catch fish by dragging nets across the ocean floor - sometimes 2000 metres down - behind ships or boats. The nets are held open by heavy doors and the edge of the net has chains or metal weights that force fish or shrimp to rise off the seafloor and get caught in the net.

New, more powerful fishing equipment now allow fishing even on rough bottoms, such as rocky reefs, that in the past were free from trawling.

According to the studies, these nets kill marine organisms by crushing them, burying them, and exposing them to predators. Much of the marine life that ends up caught in the net is not just the targeted shrimp or fish and is usually just discarded.

During one experiment, Peter Auster, science director at the National Undersea Research Centre at the University of Connecticut, says he sat on the sea floor and watched a scallop dredge pass by him. He then swam into the path where the dredge had just passed to see much of the complexity of the sea floor had been removed.

"What was once a complex of sponges, shells, and other organisms was smoothed to a cobblestone street," says Auster.

What is less obvious is the long-term impact such trawling has on the marine ecosystem as a whole, he says. "Contrary to popular belief, most seafloor habitats are not barren flat deserts, they are incredibly complex and when these structures are crushed by trawls many organisms are unable to rebuild them."

When ocean floor structures like sponges and coral reefs are removed or crushed, for example, fish, crabs, starfish and marine worms all lose their habitats and die off, the scientists explain.

Such a loss of habitat diversity from trawling could be a major reason why so many fisheries are declining worldwide, says Norse.

"Many fish species require specific habitats to survive, while other simply survive better in complex habitats," adds Auster.  One study shows, for instance, how young cod fish survive better in ocean habitats with more complex seabed structures.

"Our fisheries don't live in a vacuum and they can't survive in an underwater desert," says Auster. "This means if you care about fish and seafood, you better care about tubeworms, crustaceans, and anemones too."

Internationally and domestically, bottom trawling has not been specifically regulated because scientists are just beginning to study the impact of the fishing technique, says Norse. Very little data can be found on the impact such techniques have in most regions of the world, including Asia, Africa and Latin America

"There are enormous holes in the data," says Norse. "There is virtually no information from the gulf coast of Mexico - one of the most heavily trawled areas in the world."

Despite the lack of information, scientists are beginning to call for the development of a network of protected areas in the oceans - much like the wildlife refuges on land. These areas would allow breeding, spawning, nursing habitats for fish and other marine life.

"I want to make it clear that I'm not suggesting we stop people from fishing," says Auster. " But, some areas simply must be allowed to function as they would without the widespread disturbance of bottom trawls - or fish, other marine life, fishing communities, and all of us will lose in the end."