Effects of hydrogen peroxide on reinfection success of salmon lice

The aim of the study is to investigate how a standard lice treatment using hydrogen peroxide affects reinfection success of new lice. Salmon lice infection and hydrogen peroxide treatment may cause distress. However, the concentrations of hydrogen peroxide used will be the same as current industry techniques. Fish will be infected by introducing approximately 30 copepodids of salmon lice per individual of which normally infect fish with less than 10 copepodids per individual, which is in line with ethical rules. Expected outcome will provide scientific knowledge of importance and negative effects are seen on post-infection, the industry and legislation authorities should revise future management. Experimental treatments will use multiple tanks as replicates, 30 fish per replicate and 540 Atlantic salmon postsmolts in total. There is no replacement for this type of experiment as investigations of how hydrogen peroxide affect stress, slime layer (i.e. mucous cells) and future infection success of salmon lice, the use of live fish is appropriate. The number of fish used is reduced to minimum required to achieve densities that are relevant. Refinement was carried out in order to keep relevant number of individuals during the treatment. It is known that relevant groups reduce social interactions compared to very few individuals. Most fish will be swimming constantly during the experiment, and this is likely to decrease aggression and harmful social interactions resulting in improved welfare.