Identification of major health related loss factors in wrasse farmig through improved surveillance schemes and diagnostic approaches

Successfull rearing of wrasse is looked upon as one of the major critical factors to ensure control of sea lice in salmon populations in the future through non-pharmacological environmental friendly methods. Marine Harvest Labrus (MHL) is one of four acto rs having recently started commercial farming of wrasse. Two years after onset of production, MHL now is transferring the first batch (some 4000 individuals) to a salmon site, a positive start. However, throughout the first years, major "biological bottle necks" have been identified, during which the populations have been decimated. Whereas in some cases specific disease agents or other causes have been identified, very ofter the assumingly multifactorial aetiology leading to emaciation or acute mortality remains unknown. The reason for this is partly related to the complexity of the problems. Especially in the larvae and early juvenile phase, the balancing of feed supply and water exchange is a critical factor, to ensure sufficient access to feed, withou t compromising the water quality through diluted feed components, or through the microflora introduced from the live feed cultures. Following the short history of farming wrasse, both competence and development and use of proper diagnostic measures in the health surveillane is sub-optimal. Although some experience have been gained through the rearing of other marine species, there is a need to improve both the knowledge and the diagnostic methods in health monitioring of farmed wrasse, both in the privat e sector and in the national diagnostic laboratories (National Veterinary Institute, NVI). This project aims at, through improved diagnstic methods and surveillance schemes, to identify major disease problems and to suggest preventative measures in wrass e farming. The close link between the industry and the NVI enables building of competence at both parties, also of benefit to other produces of wrasse, on short and long term.