Plague of maverick salmon

Press, 2 September 1983, Page 13

Plague of maverick salmon

Salmon hatched and reared in Scottish commercial fish farm tanks are escaping and turning up in rivers, bringing disease in with them. The Department of Agriculture and Fisheries for Scotland, where there are now 83 salmon farms, said: “We think the problem comes from fish that have escaped rather than a fish-farmer deliberately pushing diseased fish into the open sea to get rid of them.” Salmon netted by River Thurso ghillies were suspiected of being strays and sent to the Government’s marine laboratory at Aberdeen, which specialises in salmon

disease research. “We knew immediately by their appearance that the fish were not natural stock from our river,” Lord Thurso said. “The scientists confirmed this through blood-type tests. They also confirmed that the fish were infected by a number of viruses.” The main disease that affects salmon is called I.P.N. (infectious pancreatic necrosis). It produces fungus-like, growths on the fish. I.P.N. has never been a problem on the Thurso; its native fish, through natural evolution, have built up immunity. “What worries me,” said Lord

Thurso, “is that the growth of these fish farms, particularly on Scotland’s west coast, will bring about a situation where more and more strays will turn up in salmon rivers all over Britain. “No-one knows their genetic background. No-one knows what genes will be introduced into the native stock, I suspect that some fish farmer with a tank full of disease simply opens his gates and lets them loose on the world.” The Highlands and Islands Development Board said: “Disease outbreaks constitute a major commercial risk in salmon farming. The bulk of the $6.5 million we

have invested in research and development in this field has gone to support work on disease control.” Under new Government legislation, a team of inspectors have started systematic inspections of fish farms. They have powers to ban the movement of salmon in an infected area. However, with the steady growth of the commercial salmon industry, the Department of Fisheries inspectorate does not have enough staff to maintain its planned programme of four inspections every year. — ‘Sunday Times’