By Alex Kirby BBC News Online environment correspondent

Scientists say immediate controls on deep-sea fishing are needed to protect coral reefs in the north-east Atlantic.

They have found evidence of trawlers gouging scars four kilometres (2.5 miles) long through the coral. Boats are also bringing up large pieces of coral and reef-dwelling species in their nets.

The reefs, off Norway, Scotland and Ireland, are known to be at least 4,500 years old.

The scientists, from the UK, France and Norway, report their findings in the Proceedings of the Royal Society.

Exploration for off-shore oil reserves using submersibles has exposed the damage to the coral. It is being caused in the area where the continental shelf begins to slope down more sharply towards deep water.

Temperate treasure

The affected reefs lie between 200 metres (650 feet) and 1,300 metres (4,250 ft) down. The coral is extremely slow-growing.

The lead author of the report is Dr Jason Hall-Spencer, of the University of Glasgow and Millport Marine Station, Scotland, a Royal Society research fellow.

He said: "Most of us associate coral reefs with warm, well-lit waters off tropical coasts - it surprises many that the grey north-east Atlantic harbours these amazing reefs.

"We urgently need improved management of offshore areas worldwide, to protect both ancient deep-water habitats and the fish they support."

He and his colleagues analysed commercial catches made off Ireland and Scotland by two trawlers using otter boards - large metal plates either side of the net mouth, which plough across the seabed.

Coral trawled from off western Ireland

The nets contained a range of reef creatures, including sponges, and pieces of broken coral up to one square metre in size.

This is the first time trawler catches from the reef areas have been examined.

The team also investigated two Norwegian reefs, using a remotely operated submersible. One had been intensively trawled, but there had been no commercial trawling at the other.

The trawled reef was littered with coral rubble, and otter boards had left trenches five to 10 centimetres (two to four inches) deep. There was no sign of damage on the untrawled reef.

Finite tolerance

Dr Hall-Spencer told BBC News Online: "The fishermen don't do this intentionally - they're not vandals. But although the damage is accidental, the trawlers cover something like 33 km squared on a 15-day trip.

"It's happening day in and day out, and the coral won't last indefinitely with that sort of treatment.

"The Norwegians think they've already lost 50% of their coral, and they've just imposed a blanket ban on fishing in their largest coral area."

In 1999, a London court ruled that the UK Government broke European Union rules on wildlife protection by giving oil companies permission to explore the north-east Atlantic.

The court accepted a submission by Greenpeace and other environmental groups that the rules should have been applied to waters up to 350 km (200 nautical miles) from the British coast, not just 20 km (12 nautical miles).

Time to act

Greenpeace said oil extraction would threaten whales, dolphins and cold-water coral.

Stephen Tindale, executive director of Greenpeace, told BBC News Online: "Industrial fishing is devastating the marine environment.

"This paper vindicates everything Greenpeace has been saying about the north-east Atlantic and the urgent need to protect this fragile ecosystem.

"We defeated the government in court. It would now seem reasonable for it actually to do something to protect these endangered corals."

Trawl marks on a reef