A thermal imaging camera was used by coastguards

But the search for Mr Dziok, which had been taking place over an area of about 90 square miles, has now been called off.

The 33m state-of-the-art trawler is believed to have snagged its nets on the sea bed and overturned rapidly.

The six crewmen managed to get into a life raft but Mr Dziok, who had been working on the vessel for about a month, was lost when the raft overturned.

He was wearing a lifejacket but it appears it did not inflate and coastguards said his chances of surviving in the cold water were fading.

Despite poor visibility and moderate to heavy seas, the life raft was spotted by the crew of the Stornoway Coastguard helicopter who lifted the men to safety.

Problems caused

Chief pilot Captain Alan Elphinstone said he and crew members Captain Alun Tink, winch operator Mike Birley and winchman Steve Branley faced an "extremely difficult" task.

He said: "Conditions during the rescue were not good, with poor visibility in heavy rain, complete darkness, with a moderate to heavy sea state - causing problems whilst trying to lower the winchman into the life raft.

"He ended up in the sea for a brief period of time, prior to reaching the life raft.

The fishermen were winched to safety

"The winchman remained in the life raft to secure the survivors - two at a time - to the rescue hoist, for recovery to the helicopter, then he was winched up with the last survivor.

"During the winching phase, the life raft was in the helicopter downwash and was constantly blown behind and under the helicopter, making the winching phase extremely difficult."

Mr Elphinstone added: "The crew said the vessel went down very quickly and that gave them an immediate problem.

"The life raft capsized and they had some difficulty righting it and that is when unfortunately they lost contact with the sixth crew member who couldn't hang onto the life raft and as he drifted away his life jacket failed to inflate."

The Radiant was a twin rig trawler built by the La Parilla Shipyard in northern Spain and delivered to Peterhead in April 2001.

The Marine Accident Investigation Branch inquiry will want to know how the new trawler got into trouble and capsized.

It will also want to find out why life jackets appeared not to inflate.