Wrasse – the environmentally friendly solution Published: 26 January, 2011
AN ENVIRONMENTALLY friendly way of reducing the amount of salmon lice in Norwegian aquaculture is putting lice-eating wrasse together with the salmon. Research organisation Nofima reported a new large-scale project will be prepared for commercial aquaculture to ensure an adequate supply of the lice eaters.
When it comes to eating salmon lice from large salmon, the Ballan wrasse is the most efficient wrasse, and it also gathers lice at lower temperatures than the other species, scientists at Nofima found.
A total of 2-5 per cent of wrasse is needed in the sea cages in order to delouse the salmon, or in other words a cage containing 100,000 salmon requires 2000-5000 wrasse. The largest number of salmon lice found in the stomach of a single Ballan wrasse is 300, while the average is 70.
The Fishery and Aquaculture Industry Research Fund (FHF) is behind this heavy investment, which stretches over a three-year period and has a budget of around NOK 26 million (£2.27 million). The objective is to develop the knowledge and experience that is necessary to attain a stable and predictable commercial production of the Ballan wrasse.
The wrasse are transferred to the sea cages and eat the sea lice on the farmed salmon, avoiding the need to use chemicals to delouse the salmon. 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 managing director of the research fund, Arne Karlsen.
Until now mainly wild-captured wrasse have been used. However, there is a limited supply of wrasse in the wild, and an increase in the catch can pose a threat to the wild fish stocks. The goal of the project is to cover at least 25 percent of the requirements with farmed wrasse by 2013.
This project involves the leading industry actors and research institutions in Norway. Nofima is participating along with SINTEF Fisheries and Aquaculture, the Institute of Marine Research and the Norwegian University of Science and Technology.
Roe that has been naturally spawned in the tanks was used during the first phase of wrasse farming. As wrasse roe is surrounded by an adhesive layer, attaining good disinfection is difficult, which is a necessity in order to attain a good survival rate and hatching.
In order to gain better control of the reproduction of wrasse, Nofima will work on methods to strip roe and sperm from the broodstock, methods for fertilisation of roe, and methods to prevent the roe from becoming surrounded by an adhesive layer. Finding good ways of disinfecting the roe will also be important.
In addition, Nofima will work to find out which environments are best for wrasse at various stages of development.
Other research on wrasse is also underway, including an existing research project on Ballan wrasse farming that started last year with funding totalling 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 research and development director at FHF, Kjell Maroni.
Four commercial fish farms for Ballan wrasse are currently under development. The owners include Marine Harvest, Salmar, Nova Sea, Midt-Norsk Havbruk, Sinkaberg Hansen, Lerøy Seafood Group, Bremnes Seashore and Grieg Seafood.