Pete Bevington

4 January, 2009

A HIGHLY infectious disease which can decimate salmon populations has been discovered on a fish farm in Shetland.

Government health inspectors are flying to the islands to help contain the outbreak of Infectious Salmon Anaemia (ISA), on one salmon farm site off Burra, which has been empty of fish for two weeks.

Two other sites are suspected of having the virus, one of which has also been clear of fish for some weeks.

The infected and suspected sites belongs to Scottish Sea Farms.

ISA does not affect human health, but it can wipe out salmon stocks where it is found.

The government has set up a National Disease Control Centre, banning the movement of all fish, fish eggs, materials and equipment without permission on the infected site and 11 others in a ‘control zone’, six of which are fallow.

Another 31 sites are in a ‘surveillance zone’ measuring 2.8km from the infected site, where all fish will be subject to surveillance and health inspections.

Two other companies have fish in the surveillance area – Skelda Salmon Farms and Hjaltland Seafarms.

The government’s Fish Health Inspectorate is to conduct detailed site inspections and a sampling regime of all fish and sites in the control zone. It will also try and identify the source of the disease.

The last ISA outbreak in Scotland was 10 years ago when it affected 123 sites off the northern and western isles, costing the industry an estimated £100 million and 200 jobs. The government set up a £9 million scheme matched by the industry over three years to help salmon firms deal with the crisis.

Environment minister Mike Russell stressed that much had been learned from the previous outbreak. “We will be applying those lessons vigorously with the clear aim of containing and then eradicating the disease from the current affected site,” he said.

"To prevent the spread of any disease present, the harvesting of fish from neighbouring sites will be conducted under biosecure conditions and supervised by the Fisheries Research Services."

Mr Russell stress that the disease did not affect humans. An infection of the red blood cells, ISA has a high mortality rate on farms where it is found. Symptoms include darkening of the liver, severe anaemia and visceral haemorrhage.

Local MSP Tavish Scott said he was “dismayed” to hear of the outbreak. “I vividly recall the difficulties for the Shetland salmon industry 10 years ago when ISA caused enormous financial problems for fish farmers,” he said.

“But the industry today in Shetland is very different. The lessons of the previous outbreak have been learnt and I hope that quick and decisive action by the farms concerned working with the regulatory authorities can deal with this incident effectively.”

Some fish near the infected site are almost fully grown, and these may be authorised for harvesting without loss to the farmer. Smaller fish will either be grown on or may have to be slaughtered.