The Norwegian Directorate of Fisheries estimated on Thursday that 11,600 tonnes of salmon, worth about 720 million kroner (£65 million), had been killed by the blooms.
So far nine companies have been affected. In Troms region the companies are Northern Lights Salmon, South Rollerfish, Kleiva Fish Farm, Grantaglaks, Nordlaks and Salaks, while in Nordland it has affected Mortenlaks, Ballangen Sjofarn and Ellingsen.
The losses are expected to increase in the coming days, as the bloom spreads from the inner Ofotfjord.