Effect of delousing strategies on salmon welfare and lice removal
1 Purpose: The salmon aquaculture industry in Norway currently faces challenges in the control and prevention of salmon lice (Lepeophtheirus salmonis) epidemics; recent years has seen a shift away from use of chemotherapeutants towards non-chemical methods, such as delousing with freshwater, mechanical applications or thermal treatments. However, there is not a wealth of data available on the efficacy of these methods, and there has been concern for their negative effects on mortality rates and welfare. This project will use a controlled and robust experimental setup at research facilities to compare the efficacy of three delousing strategies (thermal, mechanical, freshwater) in terms of lice removal, when used alone or in combination. Subsequent fish welfare impacts will be described by current state-of-the-art operational and laboratory-based indicators. This will be followed by another set of experiments investigating factors (fish size, ambient temperature, and use of sedation during treatments) that could influence efficacy and/or welfare.
2 Distress: Fish expect to undergo moderate distress with mild sea lice infections and delousing experience. However, fish in treatment groups with thermal delousing and combination delousings are likely to experience severe distress at the single timepoint when they undergo treatment.
3 Expected benefit: The uncertainty around the best practice protocol for using these strategies necessitates the improvement and optimisation of methods, so that they are more effective thus requiring fewer delousing events per cage in commercial contexts. There is a need for systematic comparison between the single and combined use of methods, to understand how efficacy can be improved whilst maintaining positive fish welfare. This is particularly important as these methods are being widely used in industry currently, with varying effectiveness and welfare impacts.
4 Number of animals, and what kind: Thermal, mechanical, and freshwater delousing will be tested alone and in combinations to be able to compare delousing efficacy and welfare impact. In a follow up experiment, three methods will be further tested for different factors that may influence these parameters. Total 1530 Atlantic salmon to be used across two experiments. This will cover a total of 51 treatment groups (including procedural controls and negative controls), with 30 salmon per treatment. Salmon of ~700g and 3kg will be used.
5 How to adhere to 3R: Because the parameters of lice removal efficacy and impact on host welfare, live Atlantic salmon must be used to give accurate results of impacts and cannot be replaced. The number of fish will allow for statistically-robust results while minimising the number across the numerous treatments. Methods used will be conducted by personell experienced with the procedure to ensure standardised treatment and welfare-centred handling of fish.
2 Distress: Fish expect to undergo moderate distress with mild sea lice infections and delousing experience. However, fish in treatment groups with thermal delousing and combination delousings are likely to experience severe distress at the single timepoint when they undergo treatment.
3 Expected benefit: The uncertainty around the best practice protocol for using these strategies necessitates the improvement and optimisation of methods, so that they are more effective thus requiring fewer delousing events per cage in commercial contexts. There is a need for systematic comparison between the single and combined use of methods, to understand how efficacy can be improved whilst maintaining positive fish welfare. This is particularly important as these methods are being widely used in industry currently, with varying effectiveness and welfare impacts.
4 Number of animals, and what kind: Thermal, mechanical, and freshwater delousing will be tested alone and in combinations to be able to compare delousing efficacy and welfare impact. In a follow up experiment, three methods will be further tested for different factors that may influence these parameters. Total 1530 Atlantic salmon to be used across two experiments. This will cover a total of 51 treatment groups (including procedural controls and negative controls), with 30 salmon per treatment. Salmon of ~700g and 3kg will be used.
5 How to adhere to 3R: Because the parameters of lice removal efficacy and impact on host welfare, live Atlantic salmon must be used to give accurate results of impacts and cannot be replaced. The number of fish will allow for statistically-robust results while minimising the number across the numerous treatments. Methods used will be conducted by personell experienced with the procedure to ensure standardised treatment and welfare-centred handling of fish.