Not so long ago it was impossible to visit Loch Ness without tripping over somebody who claimed to have intimate knowledge of Nessie.

But in the twilight zone of Britain’s deepest freshwater loch, a strange sanity is suddenly prevailing. There have been only two reported sightings so far this year and there were only three in 2006. A decade ago the numbers were consistently in the high teens.

It is now six years since the last big expedition to find Nessie, while the number of self-appointed “monster hunters” has dwindled significantly.

“It’s becoming a potential crisis,” says Mikko Takala, 39, who runs four webcams on the loch’s northern shore and is a founder member of the Official Loch Ness Monster Fan Club.

In any other circumstances, such an outbreak of level-headedness would be applauded. But along the shores of Scotland’s most famous loch the apparent disappearance of the legendary monster has sparked frenzied speculation. Some Nessie fans claim that she has been driven into hiding by low-flying RAF fighter jets, while others blame increased pollution. Some have even dared to venture the unthinkable: that Nessie, God rest her soul, is dead.

Steve Feltham, 44, who has spent 16 years watching the loch from a converted mobile library on its southern shore, believes that there were once as many as 30 mysterious creatures in the loch but that they are gradually dying off, because of old age. “In the heyday of the sightings, back in the Sixties and Seventies, there were probably 20 or 30 of these animals but I believe that we’re now down to the last half a dozen,” he said.

Sightings of a “monster” in Loch Ness date back to AD565, when disciples of St Columba, the Irish missionary, recorded seeing a monster appear on the surface “with a great roar and open mouth”.

It was not until 1933 that popular interest was first awakened after the first picture apparently showing a monster was published.

Scientists have sought to explain the sightings as wind on the loch surface, overgrown eels or even elephants from a local circus. Declassified secret documents released last year showed that civil servants in 1979 took the sightings seriously enough to consider using dolphins fitted with cameras and strobe lights to search the loch.

Nessie tourism brings in an estimated £6 million each year for the economy of the Highlands. But without the publicity created by sightings, the tourist industry faces an uncertain future. In the era of digital cameras, camera-phones and webcams, it is perhaps surprising that there have not been more reported sightings in recent years.

Of the two this year, one was in March when an English holidaymaker saw what he thought was a head and fin in the loch below Urquhart Castle, while the other was in May, when a Yorkshireman captured video footage of what looked like a jet-black shape moving slowly beneath the surface. Although initially viewed as promising, experts now believe it was the result of a sustained draft of wind blowing down from the surrounding hills.

Adrian Shine, 58, a naturalist who has investigated the mystery of Loch Ness for 20 years, believes that one reason for the decline in sightings is that people are more sceptical about what they see. “I think we live in a more pragmatic age, and that people are becoming more aware of the sort of illusions that can occur on water,” he said.

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