It is 85 years since a slightly built young woman called Georgina Ballantine, fishing on the banks of the River Tay, hooked and landed what was then, and remains today, the largest salmon caught in British waters. It weighed in at 64lb, and there is a delightful picture of Miss Ballantine, immaculately dressed in a smart tweed suit and hat, standing beside the massive fish that looks almost as big as the lady herself.

It is a record that is unlikely ever to be beaten. These days the salmon that swim back into our rivers after their long sojourn at sea are fewer in number, smaller in weight and apparently more uncertain about their future than they have ever been. A cri de coeur from the Salmon at Sea project, published this week, claims that a combination of climate change and illegal trawling has reduced this most glamorous of game fish to a shadow of its former self, and that unless steps are taken to save it, not only will a famous species face extinction, but the multimillion pound angling industry will also be placed at risk.

As with all conservation-disaster stories, there is an element of hype in all this — behind every anguished call for help lies a research project seeking funds. But the story of the salmon and its apparent decline tells us a great deal about the state of our conservation industry and contains a paradox that it would be wrong to ignore. The fact is that, far from facing extinction, the salmon has made a remarkable comeback — in some rivers at least.

On the Tweed, one of the most famous of all salmon rivers, catches last year were at near-record levels, with more than 14,000 salmon caught, the second-best year since continuous records began in 1952, only outperformed by the results in 2004. Others report the same kind of improvement. Rivers that were once empty of fish have been experiencing rising numbers. Reports coming in this spring are optimistic about the prospects for 2007. The figures may not quite match the miraculous catches that were sometimes recorded 50 years ago, but they are very far from the disaster that was once predicted for the Atlantic salmon — and fly in the face of those who predicted that farmed salmon would rapidly wipe out the wild variety.

The improvements have been brought about entirely by man, not nature. Huge amounts of money have been invested in buying out offshore commercial fisheries that were catching salmon returning from their feeding grounds at sea, thus preventing them breeding in freshwater rivers. Drift nets have been banned, river mouths are no longer netted as they once were, millions of pounds have been invested in cleaning river water, repairing banks and fencing them off from cattle and sheep. Further afield, the extraordinary efforts of one man, Orri Vigfússon, chairman of the North Atlantic Salmon Fund (NASF), have succeeded in mobilising international opinion and raising millions of dollars to buy out commercial fishing around the coasts of Iceland, Norway and Greenland, thus protecting the feeding grounds and migration routes of wild salmon and ensuring that they return to the rivers from which they first set out.

This has meant persuading commercial fishermen to hold back from putting to sea, paying Danish trawlermen to stop fishing for sand eels, and pointing out the impact on the food-chain of overfishing in sensitive parts of the North Sea. Vigfússon’s campaign to save the salmon is by no means ended, but it has achieved remarkable results. Speaking from his headquarters in Reykjavik, he says: “The future of the Atlantic salmon is looking brighter with every passing month. There is no doubt in my mind that we have the answer to the salmon’s problems. All we have to do is put them into practice.”

The salmon is by no means saved — climate changes could yet overwhelm the best efforts of the NASF — but the irony is that this massive rescue operation has been brought about not by conservationists but by those whose interest lies in catching the very species they are determined to save. Those who have invested time, money and enormous diplomatic expertise in preserving the salmon have done so because they have a passion for sport rather than for nature. That salmon fishing is the basis of a multimillion-pound industry, employing several thousand people in rural areas where there is not much alternative work, has obviously contributed to the campaign, but it is probably less important than the passion that anglers the world over have for standing on the banks of rivers and devising every means at their disposal to haul out of the water the creatures they have been so tirelessly helping to nurture.

Andrew Wallace, director of the Association of Salmon Fisheries Boards, describes this as “controlled exploitation”, and agrees that the self-interest of the angling industry is the best guarantor of the salmon’s future. It is, he says, “a virtuous circle” — the enjoyment of the sport brings in the money, which is then invested in conserving the fish.

That message will not be particularly welcome to conservation purists, who regard blood sports as unacceptable, and lose no opportunity in attacking hunting and fishing enthusiasts for what they describe derisively as “recreational killing”. But if they, too, are interested in restoring the king of fish to Britain’s rivers, then they may have to accept that it is the hunters rather than the protectors who have done most to achieve it. Miss Ballantine, I fancy, would approve.

Times Recommends

• An historic attack on democracy
• We must not lose sight of true enemy
• Showbiz shock: we're not in it for cash