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Trawlers threaten ocean’s biodiversity
Written by Stephen Leahy
New Scientist
30th August 2003
Hundreds of deep-sea species new to science are disappearing before they can be identified or studied, oceanographers are warning. The organisms are being pushed to extinction by trawlers targeting undersea volcanic mountains called seamounts.
In the past two years, scientists have found that seamounts are home to an astonishing diversity of species, with 40 per cent endemic to each mountain. Thousands of new species have been discovered in recent years - 600 on just five seamounts. And with 30,000 seamounts estimated to be in the Pacific alone, a huge slice of biodiversity is at risk.
"They are hot spots for the evolution of new species," says Karen Stocks, an oceanographer with the University of California at San Diego.
Although many coastal seamounts have been fished for decades, the researchers are warning that faltering fish stocks mean fishing fleets are heading into deeper waters in search of new catches. The boats are increasingly targeting pristine oceanic seamounts, home to highly marketable species such as orange roughy, alfonsino and deep-water redfish. Trawlers are often the first to discover seamounts, which they target using sophisticated sonar equipment.
But bottom-trawling nets can do immense damage within a year or two. Studies in the Tasman Sea show that coral and crinoids, a group of suspension-feeding echinoderms, cover 90 per cent of pristine seamounts. Once fished by trawlers, that figure drops to 5 per cent, and the seamount loses half its biomass. And recovery is painfully slow. Some seamounts in the north Pacific have still not bounced back 50 years after boats first trawled them, says John Dower, a fisheries oceanographer at the University of Victoria in British Columbia, Canada.
Stocks organised an international symposium in Oregon last week to gauge the growing threat from commercial fisheries. Delegates were told that fewer than 150 of the world's seamounts had been studied in detail, and that maritime nations should cooperate to manage these habitats before it is too late.
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