The mystery of the disappearing spring salmon

The salmon in our rivers are disappearing. Why? And what can be done about it?

If the owners of a great fishing river put out a cri de coeur, something must be seriously amiss - and so it is on the Tweed, which flows out to the east coast on the borders of Scotland and England. The spring run of salmon, once the river's glory, has dwindled almost to nothing, and nobody is sure why. The River Tweed Commission has launched a major conservation programme.

Not only fishermen stand to lose if the river runs down. A survey carried out by the Deloitte Touche consulting group in 1996 showed that fishing contributes pounds 12.5m a year - more than 10 per cent of local tourist income - to the Border economy, and supports 500 full-time jobs.

Including all its tributary burns, the Tweed has nearly 2,000 miles of waterways. The natural fecundity of the system is not in doubt, as I saw when I went electro-fishing with Dr Ronald Campbell, chief biologist of the Tweed Foundation, which is charged with enhancing stocks of salmon and trout.

He was working that day in the Turford Burn, where the water was only about 6in deep, and so clear that every detail of the bottom was visible. The burn appeared to contain no life - until Dr Campbell switched on his ring anode. Then suddenly the water was alive with flashes of silver as trout fry and parr turned belly-up, temporarily stunned by the 200-volt current. Every one was netted and meticulously measured before being returned to the water; and from the morning's work we could compute that this single burn contained more than 400,000 infant fish.

The challenge is to ensure that the highest possible numbers of this huge stock survive to maturity and eventually, after going out to live at sea, return to the river to spawn. Already much has been done in the upper reaches of the system. Miles of new fences prevent sheep and cattle from eroding the land at the edges of burns, and the banks themselves have been extended into the stream, increasing the depth of water and speed of flow. Man-made obstacles have been removed, so that fish can move up to spawn, and artificial pools have been created.

Yet all this work seems to be having only a limited effect. The number of salmon taken on rod and line is generally between 9,000 and 10,000 a year, and the number netted in the estuary is between 8,000 and 9,000; but only a small proportion are caught before 1 June. Thirty years ago, spring rod catches were around 5,000 a year; now they are little more than a fifth of that.

Small wonder, then, that radical proposals have been made. From 1 February, netsmen are asked to return, and tag, all salmon caught up to 1 June (they will be compensated by a reduction in the levy they pay). Anglers are being asked to return "a majority of fish caught up to the end of June".

"In general," says the recommendation, "there will be a presumption that the first fish taken will be returned (unless it is the angler's first-ever salmon)." The second fish may be kept, but the third should be put back, and so on - and all fish returned to the water should be tagged. "The first fish is the most important. It is putting this one back that will make the difference."

Further, there will be a ban on killing any fish found to be tagged already. "A tag in a fish should be regarded as its passport to the spawning grounds." The theory is that all concerned will be encouraged to play ball by the reassurance that if they return a fish to the river, it will not be killed by anyone else.

The Commissioners have also applied for a legal ban on worms and lures with multiple hooks on the lower reaches; and they are offering a reward - a side of smoked salmon, a sweatshirt or a collection of flies - to anyone who puts back a previously untagged fish.

Clearly the scheme will depend to a large extent on personal honesty. Judith Nicol, the lively director of the foundation, concedes that there may always be cheats; but, she says, "There's tremendous enthusiasm for the idea, because it involves everybody."

So far, so good. But what is happening out to sea? Nobody can answer that key question. The Commissioners are hoping to persuade the drift- netsmen who operate in inshore waters to postpone operations until the beginning of June. Yet driftnet catches have also declined drastically, and global warming may be having a disastrous effect on salmon stocks in the Atlantic.

The theory - so far unproven - is that warm water has pushed up into the normally cold areas of ocean between Greenland and Iceland, where salmon go to feed; that higher temperatures are affecting their food, and that the fish are not attaining the size or strength they need to return to their native rivers and spawn. Smolts - second- and third-year salmon - are thought to be particularly at risk.

I, for one, would not want to fish if I could not keep what I caught; for me the whole point of the exercise is to bring home something delicious to eat. But evidently there is no longer room for such caveman attitudes on the Tweed, or on many other British rivers.