Engulfed by a deadly tide

ISA is a viral infection previously unknown in Scotland. It was first identified in Norway in 1984 where it is now one of the most destructive diseases

in Norwegian fish farms. Symptoms include high fish mortality rates, darkening of the liver, severe anaemia, and visceral haemorrhage. The captive fish become lethargic, sink to the bottom of their cages, develop swollen abdomens, and bulging, blood-spotted eyes. There is no known cure for the disease.

Rod and line sport anglers believe that ISA will have a disastrous impact on wild salmonids. Many distinct

populations of West Highland salmon and sea-trout are on the verge of

extinction; displaced from their natal streams by millions of escapee farm fish and by the impact of fish farm

sea lice. The billions of sea lice which infest farm salmon also attack wild fish as they pass by. Sea lice are known to be vectors for ISA.

ISA is endemic in New Brunswick, Canada, where 25% of their fish farm industry was shut down in 1996 because of the infection. When the disease is discovered there, farmers kill quickly, process, and market the fish. Hydro Seafoods, one of the companies involved in the Scottish outbreak, is alleged to have removed diseased salmon from its Loch Nevis farm for four days after a statutory restriction order on the movement of fish was in place. Mr Hugh Allen, Secretary of Mallaig and North West Fishermen's Association, said that dead salmon had been leaving Mallaig by the lorry-load, at all times of day and night.

William Crowe, of the Scottish Salmon Growers' Association, discounted any danger to wild fish. ''We do not see ISA as being a threat to wild fish populations according to the scientific evidence we have got since 1984,'' he said. A spokesman for the Crown Estate Commissioners, who issue the planning permissions which allow marine salmon farms to operate, said: ''We share the concerns that many people feel over the impact this disease will have on some fish farms and Highland communities. We understand that Scottish Office scientists are investigating any possible future link between the disease in farm salmon and wild populations.''

Nevertheless, sport angling bodies and those concerned with the survival of wild salmonids, are greatly disturbed. Mr Michael Smith, chairman of the Tay District Salmon Fisheries Board, said: ''I am horrified by the nightmare spectre our wild fish face from both marine and freshwater fish farming.''

Chris Poupard, director of the Salmon and Trout Association, commented: ''We are very concerned about the unknown impact this disease will have on wild salmon and sea-trout in the West Highlands of Scotland, species already under enormous pressure from fish farm sea lice attack. This outbreak demonstrates, again, the need for an independent body to regulate the fish farm industry.''

This view was confirmed by Mr

Jeremy Read, of the Atlantic Salmon Trust. He said: ''The trust is concerned at the outbreak of a disease from which the UK has so far been free. It has to be assumed that there is a possibility of wild fish being infected - although there is no evidence of this from incidents in other countries . . . We have consistently argued the need for a

single, independent, regulatory body to cover all aspects of fish farm operations as well as siting. This incident stresses the need for such a body.''

The fact that the Scottish Office has acted quickly to contain the ISA outbreak will be seen by most sport anglers as simply another example of too little, too late. Anglers have warned for years that fish farming was damaging wild stocks and that the industry was inadequately regulated. They claim it is beyond reasonable doubt that the Scottish Office has failed in its duty either properly to regulate the fish farm industry or to protect Scotland's wild fish.

Salmonid numbers are now at their lowest level since accurate records began 40 years ago. During that time, rather that adopting a precautionary principle to protect wild fish, the Scottish Office has engaged in endless scientific debate and investigation. As Icelander Orri Vigfusson, of the Atlantic Salmon Fund, said recently: ''You have studied your wild fish to death.''

Salmon leukemia is here to stay, one more unwelcome present from the fish farmers to Scotland's rod and line anglers. The farmers may be able to control the disease in their salmon cages, but there is nothing that can be done to protect wild fish. Many anglers are convinced that it is only a matter of time before the even more virulent disease, Gyrodactylus salaris, so-called ''fish rabies'', also rampant in Norway, arrives in Scotland. When it does it will drive the final nail into the coffin of the salmo salar, one of God's miracle creatures.