Salmon Diseases & Parasites

In 1984, infectious salmon anemia (ISAv) was discovered in Norway in an Atlantic salmon hatchery. Eighty percent of the fish in the outbreak died. ISAv, a viral disease, is now a major threat to the viability of Atlantic salmon farming.

It is now the first of the diseases classified on List One of the European Commission’s fish health regime. Amongst other measures, this requires the total eradication of the entire fish stock should an outbreak of the disease be confirmed on any farm.

ISAv seriously affects salmon farms in Chile, Canada and Europe, causing major economic losses to infected farms. As the name implies, it causes severe anemia of infected fish. Unlike mammals, the red blood cells of fish have DNA, and can become infected with viruses.

The fish develop pale gills, and may swim close to the water surface, gulping for air. However, the disease can also develop without the fish showing any external signs of illness, the fish maintain a normal appetite, and then they suddenly die.

The disease can progress slowly throughout an infected farm and, in the worst cases, death rates may approach 100 percent. It is also a threat to the dwindling stocks of wild salmon.

In the wild, diseases and parasites are normally at low levels, and kept in check by natural predation on weakened individuals. In crowded net pens they can become epidemics. Diseases and parasites also transfer from farmed to wild salmon populations. A recent study in British Columbia links the spread of parasitic sea lice from river salmon farms to wild pink salmon in the same river.

The European Commission (2002) concluded “The reduction of wild salmonid abundance is also linked to other factors but there is more and more scientific evidence establishing a direct link between the number of lice-infested wild fish and the presence of cages in the same estuary. It is reported that wild salmon on the west coast of Canada are being driven to extinction by sea lice from nearby salmon farms. The famous Sea Trout collapse of Connemara in the early 80’s was a direct effect of salmon farms placed on the irish coastline.

Sea Lice

Recent peer reviewed international scientific literature on the impacts of sea lice on salmonids show them to have devastating effects on wild salmon, accounting for up to 39% of salmon mortalities.

NSFAS does not believe that the corpus of peer reviewed international scientific literature which recognises the negative impacts of sea lice on salmonids are being adequately dealt with in BIM’s Environmental Impact Statement.

This treatment for lice also takes away from the farmed salmon been organic which is also misleading. No data has been made available regarding th