Pete Bevington

31 October, 2009

A SIXTH case of the highly contagious salmon virus Infectious Salmon Anaemia (ISA) has been found off the south west coast of Shetland, almost one year after the disease was first identified.

Fish inspectors announced yesterday afternoon (Friday) that they had discovered ISA at a site owned by Skelda Salmon, within a control zone imposed last January when the disease was first identified in the area.

Skelda Salmon, a family business owned by crofter Robert Nicolson, of Twatt, Bixter, had been the only company to remain unaffected by the disease, which has cost the industry in Shetland millions of pounds this year.

“It’s very unfortunate because we thought we had done everything we could to get that fish as healthy as possible, and I think it is a credit to us that we have gone so long without ISA,” Mr Nicolson said.

The latest discovery throws a question mark over plans by fish farmers in the area to restock their cages next March under a new area management agreement, as there has to be a fallow period of six months after the disease is identified.

ISA is a notifiable disease, but though it can prove fatal to fish it does not pose any risk to human health.

Mr Nicolson had been allowed to keep growing the 250,000 salmon he had in eight cages, and had harvested half of his stock by the time scientists found a “slow moving fish” on Wednesday. They tested six fish and identified ISA yesterday afternoon.

He is being allowed to cull the rest of his stock, which he is growing on behalf of Norwegian firm Lakeland, under strict supervision.

ISA was first discovered in the area on 2 January at a salmon farm owned by Norwegian multinational Scottish Sea Farms, after government scientists from Marine Scotland carried out random samples following reports of large infestations of sea lice.

A control zone was immediately imposed containing 11 fish farming sites, with a surveillance zone extending out to include 31 sites.

A second case of ISA was found a week later on a farm owned by another Norwegian multinational, Hjaltland Seafarms. Two more Hjaltland sites were found to be infected in March and May, with experimental cages operated by NAFC Marine Centre scientists testing positive in May also.

As a result of the movement restrictions, companies were forced to cut back their stocking plans this year. Various attempts were made to activate dormant sites outside the zone to maximise production.