Less than 1 percent of the world's commercial fish catch comes from trawling the ocean floor of the high seas.
But the environmental impact is large – so large that many countries ban or severely restrict the practice within their territorial waters. This week, an international effort to curb bottom-trawling on the open ocean got a significant boost. In a letter to US negotiators at the United Nations on Monday, a top State Department official set out Washington's unambiguous support for a halt to the practice "until such time as conservation and management measures are adopted."
UN negotiators are trying to craft a proposal to submit to the General Assembly for a vote in early December.
Enacting the moratorium "would be a very big deal," says Joshua Reichert, who heads the environment program at the Pew Charitable Trusts in Philadelphia.
Countries have been cracking down on the practice inside their exclusive economic zones. In March, for example, the US banned bottom-trawling in waters covering some 150,000 square miles off the US West Coast. Europeans have banned the practice in the Mediterranean at depths greater than 3,200 feet. But outside the 200-mile exclusive economic zones that nations claim, bottom-trawling continues unabated.
Powerful trawlers drag nets across the ocean bottom at depths of up to 1.5 miles. This enables them to reach once inaccessible habitats such as undersea islands known as sea mounts. The nets, with yawning maws up to 200 feet across, are weighted with large steel "doors" that weigh up to 5 tons each. The idea is to "tickle" the bottom so that fish there rise into the path of the open net. But the doors, as well as rollers or wheels along the bottom of the net's opening, rip up or crush deep-sea coral reefs, colonies of sponges, and other structure-forming bottom dwellers. For instance, in 1997 during a year's fishing along a formation in the Pacific called the South Tasman Rise, 20 trawlers ripped up an estimated 10,000 tons of coral in the process of harvesting 4,000 tons of their target species, orange roughy, according to conservation groups.
"It's like clear-cutting a forest to capture squirrels," Mr. Reichert says.
Such concerns have sparked the interest in a worldwide moratorium on the practice so UN negotiators can work out rules to regulate the practice.
The administration's stance on this critical marine-conservation issue may come as a surprise to some, given what many environmentalists call a shaky White House record on other environmental issues. But the president appears to have a deep personal concern about overfishing, Reichert says. That concern was manifest most recently in June when the president set aside the world's largest marine reserve, stretching some 1,400 miles along the Northwestern Hawaiian Islands.
When President Bush issued a policy statement on bottom-trawling on Oct. 2, some opponents of the moratorium reportedly detected some leeway for a less severe alternative. Monday's letter from Claudia McMurray, assistant secretary of State for oceans and international environmental and scientific affairs, appears to remove any wiggle room, observers say.
A moratorium would have little global economic impact, supporters say. Of nearly 84 million tons of fish hauled from the oceans in 2001, bottom-trawling on the high seas accounted for only 0.2 to 0.25 percent of the total, according to a 2004 report by the World Conservation Union, based in Geneva. Members of the European Community account for the biggest share of the high-seas take, with Spain leading the list. For countries using the approach, bottom trawling appears to be the answer to declining fisheries closer to shore. And it is far more efficient – many argue ruthlessly so – than more targeted forms of fishing on the high seas.
Angst over the effects of bottom-trawling dates back hundreds of years, says Roger McManus, senior director of Conservation International's global marine division. But only within the past 10 to 15 years has technology allowed large trawlers to locate and exploit fish that thrive around deep-sea geological features such as sea mounts, underwater canyons, or deep coral reefs.
These isolated features are widely scattered through the oceans. And their ecological health affects the biological productivity of the entire column of water above them, researchers say. These biological hot spots become mid-ocean oases for large fin fish or mammals, such as tuna or whales, that migrate over vast distances and need their version of in-flight refueling. Once a trawler's net bulldozes its way across these habitats, it can take centuries for them to recover, because the organisms there are slow-growing and slow to reproduce, notes Jeremy Collie, an oceanographer at the University of Rhode Island's Graduate School of Oceanography.
Moreover, marine science still knows little about the range of creatures that thrive around these features. Efforts such as the international Census of Marine Life are trying to close the gap, but "we're still in the exploratory phase," Dr. Collie says. "The science is pretty fragmentary."
While some researchers say that the "townies" living in these oases often are species unique to that spot, others suspect that species-exchange among these isolated habitats occurs – a critical point if the UN is to develop rules to manage these ecosystems.