NAFC STAFF RETURN FROM NORWEGIAN FACT FINDING MISSION18 September, 2009 – A team from the NAFC Marine Centre’s Marine Science and Technology department has just returned from a fact finding mission to Norway where some salmon farming companies are using Ballan wrasse as ‘cleaner fish’ to control sea lice levels on salmon farms in a natural and sustainable way. Head of Marine Science and Technology, Dr Martin Robinson, aquaculture development manager, Kenny Gifford, and aquaculture scientist and technician, Gregg Arthur, were very impressed to see cleaner fish in action and to hear how some large Norwegian salmon farms, by using a mixture of wrasse species as cleaner fish, don’t require any chemical treatments for delousing. The visit focused on the two main aspects of cleaner fish use: firstly, hatchery production of Ballan wrasse at the Institute of Marine Research in Austevoll (near Bergen 60°N) and, secondly, the use of cleaner fish on a commercial salmon farm at Villa Organic in Rekdal, near Vestnes (62°N). Discussing the visit, Kenny Gifford said: ‘At the Institute of Marine Research, we met with two research scientists leading the work on Ballan wrasse juvenile production, which is now in its final year of the three-year contract. They commented that the 2009 season had been quite successful: the broodstock had spawned and they had succeeded in raising a number of juveniles.Results have demonstrated that juveniles take at least one year to grow to a size ready to be used as cleaner fish and that hatchery-reared stocks were effective only a few days after being introduced to salmon pens. ‘The visit to Villa Organic was also very enlightening. The farm currently has four large cages, moored across the tidal flow, with a current stock of 450,000 200g salmon. Each cage had a mixture of wild caught wrasse added at a stocking of approximately four per cent – around 5,000 cleaner fish per cage (a mixture of Ballan, Corkwing and Goldsinny wrasse). We witnessed a lice count during the visit and were shown records from the last few months, which highlighted a fall in lice burdens to a negligible level without any treatments. This success was attributed by the operators to the work of the cleaner fish. ‘Much discussion took place on wrasse management and current Norwegian salmon farming practices during our trip. I was particularly interested in what the managing director of Villa Organic, Dr Per Gunnar Kvenseth, had to say about the resurgence of interest in using cleaner fish in Norway with around 20 per cent of farms currently using wrasse. ‘He felt that the uptake in using wrasse across the Norwegian industry would certainly increase with the introduction of new regulations that require reporting of weekly sea lice burdens to the Government and the provision of a sea lice strategy to the authorities. ‘This method of treating sea lice in a natural and sustainable way has also been tried in Shetland, albeit a long time ago. Much has changed since then and, while there are a number of challenges to using cleaner fish effectively – such as using smaller mesh sizes and having to restrict net fouling – many pockets of the Norwegian industry are reaping the economic benefits of having stocks of high quality salmon due to the biological control of sea lice through cleaner fish. On behalf of the NAFC Marine Centre, I would like to thank Shetland Aquaculture Trust for its support in funding this valuable fact finding mission.’ The NAFC Marine Centre has been holding potential broodstock Ballan wrasse for some time now and hopes that additional information gained during the trip can now be used to obtain fertilised eggs for on-growing if sufficient industry interest exists. This will however require positive support from industry in the very near future, with a clear intent to move toward the use of cleaner fish in the Shetland aquaculture sector.