Bottom trawling impacts, clearly visible from space

Boston MA: Bottom trawling, an industrial fishing method that drags large, heavy nets across the seafloor stirs up huge, billowing plumes of sediment on shallow seafloors that can be seen from space.

As a result of scientific studies showing that bottom trawling kills vast numbers of corals, sponges, fishes and other animals, bottom trawling has been banned in a growing number of places in recent years. Now satellite images show that spreading clouds of mud remain suspended in the sea long after the trawler has passed.

But what satellites can see is only the “tip of the iceberg,” because most trawling happens in waters too deep to detect sediment plumes at the surface, say scientists speaking a symposium session called Dragnet: Bottom Trawling, the World's Most Severe and Extensive Seafloor Disturbance at the American Association for the Advancement of Science 2008 Annual Meeting here 3:30-5:00 PM on Friday, February 15 in Sheraton Boston, Back Bay Ballroom D. The session was organized by Marine Conservation Biology Institute.

Speakers at the session include Dr. Elliott Norse, President of Marine Conservation Biology Institute in Bellevue WA; John Amos, President of SkyTruth in Shepherdstown WV, Dr. Les Watling, Professor of Zoology at the University of Hawaii in Manoa HI; and Susanna Fuller, Ph.D. Candidate in Biology at Dalhousie University, Halifax NS.

“Bottom trawling is the most destructive of any actions that humans conduct in the ocean,” said Dr. Watling. “Ten years ago, Elliott Norse and I calculated that, each year, worldwide, bottom trawlers drag an area equivalent to twice the lower 48 states. Most of that trawling happens in deep waters, out of sight. But now we can more clearly envision what trawling impacts down there by looking at the sediment plumes that are shallow enough for us to see from satellites,” he said.

Dr. Watling will show startling video and images of the seafloor comparing untrawled and trawled ecosystems. They are available at www.mcbi.org.

“Bottom-trawling repeatedly plows up the seafloor over large areas of the ocean” said Mr. Amos. “Until recently, the impact was basically hidden from view. But new tools – especially Internet-based image sites, like Google Earth – allow everyone to see for themselves what’s happening. In shallow waters with muddy bottoms, trawlers leave long, persistent trails of sediment in their wake.”

To see a gallery of satellite images, and take a Google Earth “virtual tour” of trawl-caused sediment plumes, go to www.skytruth.org and navigate to the “Trawling Impacts” image gallery.