Larger farms mean fewer lice, claims research

THE larger and fewer the number of fish farms, the greater the chance of reducing salmon lice!

That is the view of Norway’s Institute of Marine Research and Veterinary Institute after carrying out a joint study on a problem that has been plaguing aquaculture companies for years. It is estimated to cost the industry more than five billion kroner a year and there are additional hidden costs on top.

The two organisations say the spread of infection between fish farms can be almost halved if there are fewer but larger farms and by using closed cages in the sea. However, they concede that the findings are relatively new and a lot more research needs to be carried out, but the feedback from breeders with larger plants had been encouraging with some reporting no lice at all.

The two institutes, who have been working on behalf of the Ministry of Industry and Fisheries, carried out an analysis on the ‘effects of changing the so-called location structure’ – location and size of fish farms – in a designated production zone between Karmøy and Sotra, north of Stavanger.

The results from their tests indicate that lice infection between plants can be reduced by 46 per cent for salmon lice and 30 per cent for disease viruses (another serious problem for the industry), if the current total of 135 plants cane be reduced to 100 or under. Output should not be affected because fewer larger and less infected sites are able to produce the same biomass as the more numerous smaller ones.

IMR Research director Geir Lasse Taranger, who compiled the report, said the results were most encouraging and provided a so-called strategic move of fish from the ‘worst’ to the best sites.

His report adds:

‘Both lice and diseases are spread in the sea between the various plants, so less infection between farms makes it easier to cultivate salmon with low lice infections, thus, improving fish health and increasing sustainability’.

The IMR says it is informing the industry on its findings.

Meanwhile, the zone where the research was carried out has been given an amber reading by the authorities under the new traffic light system, which means expansion is prohibited until the level of lice infections are reduced.