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.
- There are six species of wrasse living in Norwegian waters.
- Goldsinny and corkwing are the most common. There are smaller numbers of ballan wrasse, rock cook wrasse, scale-rayed wrasse and cuckoo wrasse.
- The ratio between the numbers of these species varies considerably along the coast. It is the goldsinny, ballan wrasse and corkwing that are most used to remove salmon lice from farmed salmon.
The goldsinny wrasse, (Ctenolabrus rupestris), is the smallest of the wrasse species and lives along the northern coast up to Northern Trøndelag. It is brownish-red in colour, grows to a maximum of 18 cm long and has a characteristic black spot on its tail.
The ballan wrasse, (Labrus bergylta), is the largest species in the wrasse family and lives along the coast up to Trøndelag.
- It can weight up to 6 kilos and live for 25 years.
- The ballan wrasse feeds on crustaceans and mussels amongst other things.
- Its colour can vary but is typically dark brown to green.
- The ballan wrasse is an excellent fish for human consumption.
The ballan wrasse is a sought-after species to feed on lice in aquaculture cages. Ballan wrasse are farmed in several places, but it is a demanding process, amongst other things because the ballan wrasse larvae are very small and relatively underdeveloped. As warm-blooded creatures, wrasse are most effective at higher temperatures. They are less effective in the winter when temperatures are lower and if it gets cold enough, they can assume a trance-like state.
The corkwing wrasse, (Symphodus melops), grows up to 30 cm long and lives up to 30 metres below the surface of the water.
- It lives along the coast up to Trøndelag and mainly feeds on mussels and copepods.
- The corkwing wrasse is especially associated with areas of dense seaweed vegetation, and is brownish-green in colour.
Cleaner fish in aquaculture
Within aquaculture, most of the current initiatives are focusing on lumpfish. There are great expectations for the increase in the quantity produced of the helpful, lice-eating lumpfish fry. Ballan wrasse are also being farmed, although on a different scale to lumpfish.
Lumpfish are a species of cleaner fish that are increasing being used in aquaculture. Upon hatching, the lumpfish are relatively well-developed. This is one of several characteristics they make them well suited to aquaculture. The farming of lumpfish is currently at an early stage and much research is being conducted to map out the lumpfishes' specific needs in an aquaculture context.
- Lumpfish are active and effective at lower temperatures, but find it difficult to deal with temperatures above 15°C.
As one aspect of BioMar's investment in feed for cleaner fish, BioMar and Nofima have carried out a large research project to see how nutritional knowledge related to marine fish and wrasse can be applied to lumpfish. The aim is to gather knowledge regarding the nutritional requirements of lumpfish to develop better starter feed, growth feed and health feed for precisely this species. This is knowledge that forms the basis for specific lumpfish projects.
The commitment to cleaner fish is embodied in a long-term development programme and involves feed development for both lumpfish and wrasse.
- As of May 2016, BioMar can refer to over 10 different controlled feed trials with lumpfish and ballan wrasse.
- This activity has resulted in innovative products with, amongst other things, the launch of a new product line for lumpfish in spring 2016.