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Still waters? 'Clear-cutting' robs the deep-sea of ancient treasures

American Association for the Advancement of Science

A school of damselfish and basslets hover above the edge of a Red Sea coral reef, feeding on plankton washed in from the open sea.

© Science/Photo by Alec Dawson Shepherd.

Click here for a high resolution copy of the image.

BOSTON, MASS. - Deep beneath the Earth's oceans, "Ancient groves of invertebrates are being clear-cut by trawling just as quickly and surely as loggers felled groves of giant redwoods," Callum M. Roberts reported today during the American Association for the Advancement of Science (AAAS) Annual Meeting.

Slow-growing fish-including 200-year-old Sebastes rockfish and orange roughy known to live 150 years-need rapid protection from deep-sea trawling, said Roberts, a scientist at the University of York in the United Kingdom. "There is probably no such thing as an economically viable deep-water fishery that is sustainable," Roberts concluded, calling for marine reserves to safeguard species from deep-sea fishing.

In the 15 February issue of the AAAS journal, Science, Roberts pinpoints 18 critical places world-wide where conservation resources would likely do the most good. Topping the list of 18 are 10 conservation "hotspots"-from the Philippines and the Gulf of Guinea to the Sunda and Mascarene Islands, and Eastern South Africa. The 10 "red zones" cover only a small fraction of the world's oceans (0.028 percent), or about one-third of all coral reefs (35.2 percent). Yet, they may shelter more than two-thirds of all vulnerable, range-restricted marine creatures. Marine species in these areas are at much greater risk of extinction than previously thought, Roberts cautioned.

At the AAAS meeting today, Roberts raised the stakes one step further, unveiling a study of deep-sea fishing impacts, being published by Trends in Ecology and Evolution. That work suggests that the reach of fishing vessels now extends deep into the sea in our hunt for seafood: Deep-sea fishing is rapidly depleting populations of the deep, where the "glacial pace of life" and extreme longevity make fish particularly susceptible to depletion and possible extinction.

"We could be losing [deep-sea] species far more quickly than we can describe them," Roberts warned.

Coral reefs are rich in invertebrate life. Sponges and gorgonians dominate the foreground of this view across an eastern Caribbean reef.

© Science/Photo by Callum Roberts

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Indeed, a world "we cannot yet imagine" lies deep beneath the seas, but undiscovered animals and microbes are increasingly threatened by commercial pressures, said AAAS speaker, Cindy Van Dover of the College of William & Mary (Williamsburg, Virginia). Whether they live in hot vents or cold seeps, deep-sea extremophiles share evolutionary histories, and ongoing research has "greatly expanded our understanding of the limits to life on Earth," said Van Dover, who has spent much of her career underwater, one of an elite few scientists certified to pilot submersibles.

The review of deep-sea ecosystems by Van Dover and colleagues, also published in Science's 15 February issue, put Roberts' call for conservation into perspective:

Some life forms in extreme deep-sea environments date to the Mesozoic Era, she noted, while others are recent invaders. Young or old, they may hold the answers to key biological and evolutionary questions. Certain vent-dwelling barnacles and primitive gastropods, for example, may be living fossils, having first emerged some 248 to 65 million years ago. Other deep-sea creatures may have originated in the Paleozoic, 540 to 248 million years ago.

According to Roberts, such curious relics, like countless important fish species, are now threatened by deep-sea trawling. These techniques emerged in the 1960s, as overfishing depleted shallow-water fish stocks. Already, key species have been dramatically reduced: Off-shore from New Zealand and southern Australia, 20 minutes of deep-sea trawling pulled in 60 tons of orange roughy in the 1980s. Today, stocks have been reduced to less than 20 percent of their prior abundance, Roberts reported. Similarly, deep-sea catches of pelagic armourhead (Pseudopentaceros wheeleri) have collapsed from 30,000 tons in 1976, to just 3,500 tons on today's average trawl. Because deep-sea fish may live many years and reach reproductive age late in life, they can disappear quickly, Roberts said. Meanwhile, trawlers are literally mowing down rich communities of deep-water invertebrates. Fishing with long lines, traps and gill nets may be less destructive, he noted, but the low productivity of deep-water environments makes sustainable fisheries less than economically viable.

A roving grouper, Plectropomus maculatus, stalks the coral groves of a lush reef in the southern Red Sea.

© Science/Photo by Alec Dawson Shepherd.

Click here for a high resolution copy of the image.

"It is clear that the biology of deep-sea organisms compels us to rethink attitudes to exploitation that we have developed from experience with organisms living in the `fast-lane' of shallow seas," he said. "We must consider deep-sea fish stocks as nonrenewable resources."

In his Science paper, Roberts urges conservation targeting 10 marine biodiversity hotspots in the following regions: The Philippines; Gulf of Guinea; Sunda Islands; Mascarene Islands; Eastern South Africa; North Indian Ocean; South Japan; Cape Verde Islands; West Caribbean; and Red Sea. Other important places identified as important to biodiversity include: New Caledonia; Great Barrier Reef; Gulf of California; Hawaii; Western Australia; Easter Island; St. Helena and Ascension Islands; and Lord Howe Island.

These conservation targets are based on range maps of 3,235 species of fish, coral, snails and lobsters. Places rich in unique species were compared and combined with a map of the world's most threatened coral reefs. "Conservation efforts could be especially effective if they target threatened marine biodiversity hotspots," Roberts said. "Our best strategy will be to combine these efforts with protection of less threatened reef `wilderness' areas, and make vigorous efforts to mitigate climate change."

Species in the sea are usually assumed to be widespread, as ocean currents can move organisms thousands of miles, Roberts noted. But, his Science study shows that more than half of all lobster species on coral reefs were confined to narrow geographic regions, while nearly a third of snails, and more than one-fourth of fish were range-restricted. Even among corals, 7.2 percent were unique to limited areas. Small geographic range size raises the risk of extinction because localized impacts can eliminate all of a species, he noted.

Map showing tropical reef, marine biodiversity hotspots.

© 2002 Conservation International

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Van Dover's Science paper describes the treasure trove of life in small underwater "habitat islands"-hydrothermal vents and cold seeps-which shelter untold numbers of ancient creatures. Since the discovery, in 1977, of steamy underwater vents teaming with invertebrates, researchers have been investigating the evolution of biogeography of these strange life forms. Like those found in cold seeps, vent-dwellers extract energy from compounds such as hydrogen sulfide or methane. For scientists studying such extremophiles, evolutionary mysteries persist: Weird tubeworms in cold seeps off southern California, for instance, are genetically similar to those found in the West Florida Escarpment seeps, yet it's unlikely they could have dispersed from one spot to the other.


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