By Richard Black
BBC science correspondent
A coalition of leading environmental and conservation groups has called for a ban on the damaging fishing practice known as bottom-trawling.
Orange roughy: The trawler fleets chase particular species
The Deep Sea Conservation Coalition says the technique of dragging heavy nets across the seafloor is doing immense harm to fragile ecosystems.
As well as bringing up valuable fish species, such as orange roughy, the trawlers also gouge out corals.
The coalition wants the United Nations General Assembly to ban the practice.
Marine scientists and conservationists presented their case at a meeting in London, UK.
The principle of bottom-trawling is simple - drag a heavy net across the ocean floor, and any fish there will be caught. The problem is, everything else is caught, too.
It has been likened to fishing with a bulldozer.
According to one study discussed at the meeting, a single net can snare a tonne and a half of coral every hour.
Fishing with a "bulldozer": Before (top) and after (bottom) the trawlers have passed through
These are cold-water corals - not the brightly coloured reefs of the tropics, but deep-water varieties which grow very slowly.
According to Dr Alex Rogers, from the British Antarctic Survey (Bas), this makes them particularly vulnerable.
"These are very slow-growing ecosystems," he told BBC News.
"We've measured the age of some of these off Europe to 8,500 years old. If they're damaged heavily, they may take hundreds or thousands of years to recover - or may not recover at all."
The countries with deep-sea bottom-trawling fleets are few in number.
They include Spain, Russia and New Zealand, but there are other fleets operating out of Portugal, Norway, Estonia, Denmark/Faroe Islands, Japan, Lithuania, Iceland and Latvia.
The Coalition says these 11 countries took approximately 95% of the reported high seas bottom-trawl catch in 2001.
The fleets are after valuable fish species such as the orange roughy, blue ling and roundnose grenadier. These creatures hug the underwater mountains known as seamounts and it is these locations which provide such rich habitats for cold-water corals and the other animals and plants that live among them.
As a United Nations report released earlier this year made clear, these corals are far more widespread than scientists had previously believed, stretching from northern European waters to the south of Australia.
The scientists and environmentalists gathered in London fear bottom-trawling will destroy many of the reefs before researchers have had a chance to study them.
"On one seamount in the Tasman Sea, we found 850 species of which a third haven't been found anywhere else," Dr Rogers explained.
Much of the life on seamounts has yet to be catalogued
"And on the Norfolk Ridge near New Caledonia, there are a dozen seamounts which have been explored. Here there were around 1,200 species, a half of them new to science."
Currently, discussions are underway at the United Nations in New York on fisheries and ocean management. These discussions will result in resolutions being put before the General Assembly next month.
The Coalition is urging the UN to declare a global moratorium on bottom-trawling as soon as possible.
"We are advocating a short-term emergency moratorium until the international community comes to its senses and decides how to manage deep-sea fisheries," said Coalition coordinator Kelly Rigg.
In February this year, more than 1,100 marine scientists also signed a statement calling on the UN and world governments to stop the destruction of deep-sea corals.
Their statement was released at the annual meeting of the American Association for the Advancement of Science (AAAS).
"Deep-sea corals and sponges are crucial habitat elements for seafloor species," Dr Daniel Pauly, of the University of British Columbia, in Vancouver, Canada, told BBC News at the AAAS gathering.
"Allowing trawling in coral 'forests' is the worst thing we are doing in the ocean today. It should be stopped immediately until scientists can determine whether trawling in the deep sea can be justified anywhere.
"Nothing could be dumber than destroying the habitats that depleted fish populations need to recover. Governments must stop pussyfooting around and do something useful."
The Deep Sea Conservation Coalition includes Conservation International, Greenpeace International, World Conservation, the Marine Conservation Biology Institute, the Natural Resources Defense Council, and the New England Aquarium, among others.
The known locations of cold-water corals