Fishing Lines: Sturgeon feeding on the Loch Ness legend

I AM pleased to reassure those who fear the Queen may die from a surfeit of caviar if a submarine expedition to Loch Ness in March captures the fabled monster. The latest scientific thinking is that, far from being a plesiosaur or similar dinosaur, Nessie is merely a wandering sturgeon that has strayed into the 23-mile loch and discovered that she likes bagpipe music.

Research to be published in the scientific journal Nature claims that any monster is unlikely to weigh more than 300kg (about 660lb) because there is insufficient fish population to support a larger predator; and that a sturgeon is the most probable explanation. In fact, the first sighting of the beastie, recorded in the Inverness Courier of 1868, spoke of a huge fish.

A sturgeon in British waters may strike you as preposterous as England beating the West Indies 5-0 in the forthcoming Test series, but they have occasionally been recorded. Charles Dickens, in A Dictionary of the Thames, wrote: 'Sturgeon occasionally come up the Thames, but they were never numerous.' Thomas Pennant, in British Zoology (1812), recorded one of 460lb while a more recent book, Peter Maitland and Niall Campbell's Freshwater Fishes, lists one of 320kg (about 700lb).

But by sturgeon standards, even a 700-pounder is a tiddler. The largest of the 23 species in the family, the beluga, is estimated to grow to more than 5,000lb by Russian caviar fishermen, who regularly catch them over 2,000lb. A two-tonner would be about 25ft long.

The Nessie-is-a-sturgeon theory does have some attractions. Any landlocked sturgeon would have to come near the surface to feed on salmon and trout, its main sustenance in the loch. These fish prefer shallow water and certainly would not want to swim 700ft down, where there is no food and where they couldn't see it even if there was. Furthermore, sturgeon - which are only found in the northern hemisphere - are great travellers. Tagged specimens from North America have occasionally been captured in European waters and it is far from unlikely that a hefty beluga could have lost its way. The Worcester Journal of 1833 recorded an 8ft 6in sturgeon weighing 203lb caught in a stake net near Findhorn, Grampian.

Of course, the whole theory could have arisen because the scientists simply want to study sturgeon. They are fascinating beasts. Although mainly a marine fish, all species come into fresh water to spawn. They are almost certainly the longest-living fish (adding weight to the Loch Ness legend) though nobody seems quite sure how old they could be. A mere six-footer in North America was 82 years and still growing. Goodness knows how old a 5,000-pounder would be. Sturgeon are not good swimmers, have no scales (which is why they were at one time banned from the Jewish diet) and, of course, lay large eggs (as many as 2.5 million) that are hugely prized.

You can even catch sturgeon on rod and line. The angling writer and explorer John Bailey, from Norfolk, landed them to 400lb in Kazakhstan last year, but hooked fish four times as large. Bailey was fishing from a boat, and after several hours of being towed out to sea, with dusk descending, he wisely scorned the example of Hemingway's The Old Man and the Sea and cut the line.

The largest captured in the British Isles on tackle was taken in July 1933. It was accidentally hooked in the head by a salmon angler, fishing in the lower reaches of the river Towy, in Dyfed. The fish, weighing 388lb, was 9ft long and contained nearly 80lb of caviar. As the sturgeon was designated a royal fish the lot was offered to the Crown - but turned down.

While it is true that any captured are supposed to be offered to the reigning monarch, it is untold years since they have enjoyed their royal prerogative and tucked into sturgeon and chips at the Palace. So if you turned up at the back door with the Loch Ness Monster over your shoulder, I'm told the Royal Household would probably say: 'Thanks, but no thanks.'