What are cleaner fish?
Cleaner fish are certain species of fish that, amongst other things, feed on the sea lice that live on farmed fish. In common with salmon lice, the cleaner fish also live freely in nature. Lice-eating species are now caught and farmed on a large scale to control salmon lice in a chemical-free, biological manner.
The salmon louse is a parasite that lives freely in seawater in all areas of the sea in the northern hemisphere. It attaches itself to the fish as a copepodite and remains stuck there until it can move and change position on the fish.
The salmon louse sustains itself by feeding on skin cells and mucus. The salmon louse represents the greatest challenge for the aquaculture industry today, although they do not affect food safety or the quality of the salmon.
Why cleaner fish?
The salmon louse is the most common parasite on farmed salmon, and one of the biggest challenges for the aquaculture industry. Cleaner fish, which from nature's perspective are designed to feed on such parasites, are used in the cages to feed on lice from farmed fish.
Under the right conditions, this represents an effective form of biological delousing that can prevent chemicals entering the environment and saves a lot of money for the farmer.
Biological delousing with cleaner fish is a forward-looking method and represents a continuous, preventive treatment for salmon louse. After a slow start with the use of wild-caught wrasse, we see today that the farming of lumpfish is the most popular measure to combat salmon lice.
There have also been positive developments in the farming of ballan wrasse, although on a different scale than lumpfish.
Until a few years ago, it was not common that cleaner fish in cages were fed maintenance feeds. This practice has now changed however as research has identified that insufficient access to the correct nutrients makes for less healthy and less functional cleaner fish.