Yet the Beauly is not only beautiful, it is also the scene of a fascinating experiment in river management, which began in 1990 when the Lovat estate sold the fishing rights, together with the 30,000-acre Braulen deer forest, to the specially formed River Beauly Fishings Company. The price was astronomical - rumour said pounds 14.5m - but the new company recovered pounds 4.5m by selling off the deer forest, leaving themselves with a net outlay of some pounds 10m, which was raised from equity investors and bank loans.
The longer term objective is to generate funds by syndicating the fishing rights - that is, selling individual 'rods' in perpetuity. From a low point of about pounds 20,000 for a week in April, the price of a rod rises to pounds 70,000 at the peak in July, when salmon are moving up-river in huge numbers to their spawning grounds, before falling back to pounds 20,000 in the autumn. Such is the demand for top-class fishing that all but two of the peak-period rods have gone already - although plenty are available earlier and later.
From its inception, the company has aimed to rehabilitate the river, to spread good fishing more evenly through the season and, in particular, to restore the spring run of salmon for which the Beauly used to be famous. To this end, it commissioned a feasibility study by scientists from Aberdeen University and launched vigorously into a programme of improvement.
Apart from the river itself, one of the aces the company holds is its managing director, William Midwood. Practically a human otter, with nearly 1,000 salmon to his own rod, and a man of infectious good humour, he has set about the restoration of the Beauly with a rare combination of enthusiasm and common sense. Fishing under his tuition is a dream. 'Look at this]' he cries as he scans a promising pool. 'We're going to fill our BOOTS with salmon here]'
Although the main river is only a dozen miles long, together with its two main tributaries - the Farrar and the Glass - it has a vast catchment area extending through the mountains almost to the west coast of Scotland, and in its lower stretches it is 100 yards wide. One essential task has been to create more pools in which fish may be caught - and this has been achieved by the construction of new croys, or breakwaters, jutting out at angles from the banks. These increase the flow of water in some areas and slow it in others, making salmon more inclined to pause as they head upstream.
At the same time the banks have been stabilised in places where erosion had set in, and large single rocks placed at strategic points in the stream, to create places for salmon to lie. Not that tampering with a river of this size is easy: after one new croy had been made with gabions - rectangular steel-mesh baskets packed with stones - the current began scouring away the river-bed downstream of the obstruction, and 1,000 tons of big rocks, at pounds 8 per ton, had to be brought in to stabilise the structure.
On the banks the company has built three fine Norwegian fishing huts, made of solid timber, furnished with running water, gas cookers and wood-burning stoves. A full-time river watcher now supplements the team of ghillies, most of them members of the Matheson family, who have worked on the river for more than 100 years.
The greater challenge, however, was - and is - to increase the number of fish coming up the river in spring, and the aim here is to augment the salmon's extraordinary method of reproduction. In November each hen fish lays her spawn in hollows that she scoops out of the gravel in the beds of tributary-burns. A cock fish fertilises the deposits, and the eggs incubate through the winter, hatching in April or May.
The infant salmon, known first as alevins, gradually develop into fry two or three inches long. The essential characteristic of these tiny fish is that they are loners: each takes up a territory of its own, hiding under a large stone and feeding on organisms that come past in the current, but avoiding contact with others of its kind.
At the next stage of their growth they are known as parr; but only when they metamorphose into smolts do they become gregarious. Then, at the age of probably two years (in Highland waters) they turn more silver, lose their red spots, break contact with the bottom and start to feed on top of the water. Thus set free, but still weighing only a few ounces, they drift downriver and out to sea.
There they grow at astonishing speed: those that return to the river after one sea-winter are known as grilse, and often reach 10lbs by midsummer; others may not come back for four or five years.
Like other experts, William Midwood believes that the higher up a river a salmon is reared, the more likely it is to return early in the season, to give itself the maximum chance of reaching its native haunts. He has therefore put much effort into improving the habitat in the Beauly's upper reaches, especially by clearing out the mouths of tributary-burns, many of which had been choked by fallen trees.
He had also conceived an ambitious scheme for restocking the upper river, and work on this began in 1991. Last autumn, in a pool far upstream, he and his eight-man team caught 50 brood fish, and these produced more than 200,000 eggs, which spent the winter incubating in the company's new hatchery.
Now wriggling alevins, the tiddlers will be put out as fry next month in the highest suitable burns. Yet this will be no mass bombardment: every fish will be placed in position individually by a man wielding a tiny net, at the rate of 75 to every 100 square metres. Each will thus land in a little territory of its own, and will have the best possible chance of forming a life-bond with that particular cranny of the environment. As Mr Midwood puts it: 'This is a precision operation, like direct drilling of corn, rather than broadcasting: you place each seed in a particular spot, knowing that it will grow.'
Under the new regime, the number of salmon caught in the Beauly has already jumped from 842 a year to 1,270. Cynics may say that this reflects nothing more than an increase in the amount of time and effort being put into the fishing; but it seems certain that the physical improvements in the river have made some difference.
Yet the real test will come early in 1996, the first year in which the company's own carefully planted fry should start to return. If the spring run does revive as hoped, Mr Midwood and his clients will be able to fill their boots with salmon in March, April and May, as well as in the glut of high summer.
More information from: River Beauly Fishings Company offices at Broomy Bank, Hampton Heath, Malpas, Cheshire SY14 8LT (0948 85393).