Fishing trawlers scrape rock bottom

 Fishing boats in search of shrimp, flounder, and other bottom-dwelling seafood delicacies drag heavily weighted nets along the seafloor. Creatures not snared are crushed, buried, or exposed to predators. Marine researchers now say such trawling worldwide destroys a seabed area twice the size of the contiguous United States each year.

"Nobody had a clue that it was nearly this extensive," says Elliott A. Norse of the Marine Conservation Biology Institute in Redmond, Wash. The complete damage report appears in a suite of articles in the December Conservation Biology.

 Norse had long suspected that damage from bottom trawling is in the ballpark with that from clear-cutting forests on land, but his new calculations show that it's 150 times more widespread. Logging flattens an area about the size of Indiana yearly.

 Since the 1970s, new technology has allowed fishing fleets to trawl deeper. Not adapted to storm waves and other trials of shallow-water life, creatures in deep waters take longer to grow and recolonize than their near-shore relatives. Norse predicts that the deepest areas of the trawled seafloor may take as long as clear-cut forests to recover-from decades to centuries.

 Skeptics point out that such estimates stem from incomplete research. "While we know species diversity from the trawl area drops, other species tend to thrive afterward," says Scott Smullen of the National Marine Fisheries Service in Silver Spring, Md. Smullen says that before sounding an alarm, his agency is trying to find out more about trawling's long-term effects on fish habitat. Norse and others are pushing to set aside areas for immediate protection.