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Breeding Can Reduce Lice

NORWAY - Some salmon are more easily infested with salmon lice than others. Utilising this in the breeding of farmed salmon can save millions and reduce the infestation pressure of salmon lice among wild salmonids.

These are the findings of a recent Nofima research project.

Recent media coverage has indicated that salmon lice have become resistant to anti-lice medication.

However, one measure is breeding a farmed salmon that is infested by salmon lice to a lesser extent than today.

Salmon from the Trondheim Fjord attacked by salmon lice

Power of resistance

"The aquaculture industry and authorities should join forces to breed a salmon with greater powers of resistance to salmon lice," says Nofima (formerly Akvaforsk) Senior Scientist Bjarne Gjerde.

"Breeding for resistance to salmon lice should be included as a supplementary measure in the industry's and authorities' action plan against lice in the same way as there is today an order to delouse as soon as a stipulated number of lice per fish is exceeded."

Infestation of wild salmon

Salmon lice from farmed salmon is one of the threats facing wild salmonids as wild salmon may be infested by lice spread by the coastal currents.

"The responsibility to take good care of wild salmonids and the risk of developing a resistance to medication against salmon lice means that it is important to increase the farmed salmon's powers of resistance to salmon lice," says Gjerde.

"Purposeful breeding for a farmed salmon, which is infested by salmon lice to a lesser extent than today, will also reduce the infestation pressure on wild salmonids as there would be less salmon lice along the coast."


This can provide significant gains in two ways. The salmon will require fewer treatments against salmon lice and the infestation pressure on wild salmonids will decrease. The first is of major economic value to the salmon farming industry, while the latter is of major value to society.

"But it is important to emphasise that this, like with other breeding programmes, is a long-term measure," says Gjerde.

"It will be some years before we reap the big gains, so it is important to commence this work as quickly as possible."

The project is financed by the Research Council of Norway and Salmo Breed AS. The findings from a fresh project, financed by the Aquaculture Industry Research Fund (FHF) and Salmo Breed, will be available in the summer.