finishedMaster ThesisAquaculture

Field study on Atlantic salmon (Salmo salar) acoustic delicing: Fish welfare and salmon lice (Lepeophtheirus salmonis) dynamics

January 2020 - June 2021

Project Summary

High density of salmon lice is one of the biggest challenges in Norwegian salmon farming. For the aquaculture industry it is important to develop methods that include high efficiency in the removal of salmon lice, low costs and minimal negative effects on fish and the environment, while avoiding wastage and labour-intensive operations. AcuLice treatment has been developed to fulfil these requirements and uses a composite acoustic sound image with low-frequency sound to remove salmon lice from Atlantic salmon. This master thesis examines and documents the stress effects on Atlantic salmon as well as the effect on salmon lice dynamics in large-scale of the AcuLice system. The stress effects of salmon were characterized by measuring the concentration of cortisol (primary stress response) and glucose, lactic acid, chloride, calcium and magnesium (secondary stress response) in the blood, as well as calculating specific growth rate (tertiary stress response). These measurements were compared with a control sample prior to AcuLice treatment (primary – and secondary response) or the reference group (tertiary response). The effect of AcuLice treatment on salmon lice dynamics was measured by weekly salmon lice counting’s at the facilities from week 30, 2019 to week 20, 2020. The number of salmon lice treatments in the same period, was also recorded and compared between the AcuLice - and reference group. In addition, numbers of weeks until the first salmon lice treatment (mechanical treatment) was compared between the two groups. The findings from the stress analyses showed no significant difference in the primary stress response measurements between the AcuLice and control group. In addition, apart from slight increase in plasma glucose, no significant difference was observed in in the secondary or tertiary stress response measured. Furthermore, a significant higher number of small salmon lice was found in the AcuLice facilities compared to the reference. For the mature female salmon lice, a significant lower number was shown for the AcuLice group. In addition, a lower number of salmon lice treatments and a longer production period before the first salmon lice treatment occurred was observed at the AcuLice facilities. The experiments suggest that AcuLice treatment does not have a negative effect on Atlantic salmon when it comes to acute stress and that the treatment has a positive effect on reduction of salmon lice pressure at the production site.