A White House letter on Monday underscored firm US support for a UN moratorium on bottom-trawling.
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.