Follow-up study on acoustic de-licing of Atlantic salmon: effect on growth and stress physiology of Atlantic salmon and cleaner fish

Acoustic lice treatment (AcuLice) is a newly developed system which uses a composite acoustic sound image with low-frequency sound to remove salmon lice (Lepeophtheirus salmonis) from Atlantic salmon (Salmo salar). The impact of the AcuLice system in Atlantic salmon and lumpfish was evaluated according to primary, secondary and tertiary stress responses in one location (Hattasteinen) with AcuLice system operating in 6-week cycles and in a reference location (Tittelsnes) without the AcuLice system. Appetite and behaviour were also recorded. Fish from Hattasteinen, both Atlantic salmon and lumpfish showed a normal growth pattern, with no alterations in biometric indexes that could be interpreted as a sign of tertiary (chronic) stress response. Atlantic salmon from the reference location exhibited a reduced appetite and slower growth at the beginning of the trial, suggesting that stock differences are much more important than any potential effects produced by the AcuLice system. There were no changes in feeding, swimming or aggressive behaviour that could be attributed to the AcuLice operation. In summary, no negative effects in Atlantic salmon or lumpfish that could be linked to the operation of the AcuLice system were observed in this trial.