In recent years, sturdier winches, stronger cable and more powerful engines have allowed fishing trawlers to extend their reach to depths of 3,000 feet and beyond, biologist Callum Roberts said in Boston at the annual meeting of the American Association for the Advancement of Science. At those depths, growth is so slow that harvested fish can take decades to be replaced and damaged coral may require centuries or more to grow back.

``The pace of life in the deep sea is virtually glacial,'' said Roberts, a professor of environment at the University of York in Britain. ``What we are destroying now will take centuries to recover.''

In a study published in the journal Trends in Ecology & Evolution, Roberts compared the current situation in the deep oceans to last century's clear-cutting of ancient redwood forests in the western United States.

In the Pacific off New Zealand, trawling has cut orange roughy populations to one-fifth their original levels. Because those fish live to be 150 years old and do not reproduce until they are in their 20s, even under optimal conditions they would take decades to recover.

Sea-bottom coral, sponges and seafans also suffer greatly when trawls scrape across the ocean bottom. A recent study by Australian scientists found that 95 percent of the trawled bottom in deep water off Tasmania are bare rock, compared with 10 percent of untouched areas.

``You can go with ROVs (remotely operated vehicles) and take pictures before and after a trawl's gone through and see the devastation,'' said Cindy Lee Van Dover, an oceanographer at the College of William and Mary in Williamsburg, Va.

Roberts said only a worldwide network of marine reserves can protect orange roughy, Nassau grouper and other deep-dwelling fish from extinction.