When salmon is farmed in large-scale monocultures, the fish tend to become susceptible to disease and parasites. Researchers working for the organization Nofima have now found a way of combating the parasite salmon lice in fish farms without using any dangerous toxins. Wrasse loves to eat lice, so the researchers simply added wrasse to the salmon populations and the result was astonishing.

During the trials, the most efficient lice eater turned out to be the Ballan wrasse (Labrus bergylta). In addition to being highly efficient, it also gathered lice at lower temperatures than the other Wrasse species that took part in the experiment.

When Ballan wrasse was used, roughly 2-5% wrasse was needed for salmon living in sea cages. This means that a population of 100 000 salmon will need somewhere between 2 000 and 5 000 wrasse to stay deloused. A new larger project will now be prepared to make sure there is an adequate supply of the lice eaters in Norway. The project will go on for three years and has received funding from The Fishery and Aquaculture Industry Research Fund (FHF).

The effort which is now commencing is unique in both a Norwegian and global context. Norway is the only salmon-producing country that is using wrasse on a large scale to combat salmon lice,” says Arne Karlsen, managing director of FHF.

Removing large amounts of Ballan wrasse from the wild to keep in salmon farms could cause serious damage to the wild populations and the goal of the Norwegian project is therefore to cover at least 25% of the demand with farmed wrasse by 2013.

In addition to Nofima and FHF, the project will also involve SINTEF Fisheries and Aquaculture, the Institute of Marine Research and the Norwegian University of Science and Technology.

Several Norwegian projects are already taking a closer look at the Ballan wrasse, including a research venture concerning Ballan wrasse farming that started last year with funding totaling NOK 12 million from the Research Council of Norway, FHF and industry partners.

It is estimated that the total Norwegian effort on Ballan wrasse farming is in the vicinity of NOK 100 million,” says Kjell Maroni, research and development director at FHF

The researchers will now have to find out how to carry out large-scale wrasse farming without being plagued by the same problems with disease and parasites as the salmon farms.