Salmon lice cause economic losses in salmonid aquaculture. The use of cleaner fish has become an important tool to fight lice. Lumpfish and several species of wrasses are used. There are extensive fisheries for wrasses, and aquaculture of ballan wrasse and lumpfish. Fisheries and use have evolved fast, but the development of a regulatory framework has lagged behind. Challenges linked to poor welfare, diseases and changes in the genetic structure have raised questions on the sustainability of the current practice, and The Norwegian Food Safety Authorities stated that if the welfare is not improved and the effect of cleaner fish better documented, the use can be reduced or terminated. This will have implications for the Swedish and potential future Danish fishery. This report presents the state-of-knowledge on biology, fisheries and how management have dealt with the fisheries and use.