LONDON • A man who has spent 24 years scanning Scotland's Loch Ness for its legendary monster reckons that Nessie is most likely a giant catfish - although he is not prepared to give up looking just yet.

Mr Steve Feltham, who holds a Guinness World Record for the longest continuous Nessie vigil, says it is the most probable explanation for the enigmatic beast.

"The current front-runner is the Wels catfish. It is the most likely explanation," the 52-year-old said.

"I am not saying it is the final explanation. It ticks most of the boxes with sightings - but it doesn't tick them all."

Mr Feltham left his home and girlfriend in 1991 to go look for Nessie and has spent the years since in a caravan on the lake shore.

Media reports this week suggested that Mr Feltham had given up his vigil after favouring the catfish theory, but he insisted that he would keep searching for the answer.

"We still have this world-class mystery and, for the next several decades, I hope to carry on trying to find the answer," he said.

Catfish are native to central and eastern Europe, but he believes the Victorians might have introduced them to the deep freshwater lake so they could catch them for sport.

Wels catfish can grow up to 4m long and weigh more than 400kg - though they are rarely more than half this size. The scaleless fish can live for at least 30 years.

Mr Feltham said other hardened Nessie hunters have reached different conclusions from the same available evidence.

"Others say sturgeon, giant eels, plesiosaurs. A couple believe there's a spaceship on the bottom of the loch; one woman thinks there's a porthole to a hollow Earth," he said. "Many people think it is a non-physical phenomena."

He added: "I hope it turns out to be something far more exciting than a catfish. It is a mundane creature, even though it's massive."

AGENCE FRANCE-PRESSE