THE fish disease Infectious Salmon Anaemia (Isa) was yesterday confirmed on a farm in St Magnus Bay, Shetland, bringing the total number of Scottish farms infected to nine.

It is the first time the disease has been identified in Shetland. It is also feared that another farm in the same area may be infected.

The infected farm has been issued with a statutory notice requiring the immediate slaughter of all its fish.

It will then have to be disinfected and left fallow for a period. Fish and shellfish farms in the area will be subject to movement restrictions and regular inspection.

Lord Sewel, Scottish Fisheries Minister, said: ''Evidence suggests a possible link, involving wellboats, between the confirmed Shetland site and one of those already identified as infected on the West Coast.

''In these circumstances, this latest outbreak may not be altogether surprising but it is certainly very disappointing.

''One of the major problems is that we are dealing with a virus which incubates for several months before expressing symptoms. Inevitably, this creates difficulties for managing the disease.

''Rigorous controls have been put in place. These will continue and I expect to announce shortly further restrictions on wellboats, equipment, and personnel.''

Two other salmon farms off the Isle of Mull have also been placed under official suspicion. This brings the total number of fish farms suspected of being infected to 12.

Isa has previously been identified in Norway and Canada, where it is controlled, but this is the first outbreak in the European Community.