Different scuscpetibilities of salmonids to Paramoeba perurans infection and AGD development

The purpose of this study is to determine the relative susceptibility of farmed and wild strains of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) post-smolts to infection with Paramoeba perurans and the development of amoebic gill disease. Although fish will be infected with a parasite, the level of disease and selected humane endpoints limit the level of distress for the fish. The study will involve a common garden challenge of the fish (all three species in the same tank) to maximise the efficiency of the challenge that will occur at different levels of challenge with infective amoebae (0, 10 100 and 1000 cells/L). This ensures that all fish receive the same challenge dose and so true susceptibility can be determined. This minimises the number of fish to be used, refines and optimises the experimental design and gives greater relevance and reliability in the data being obtained. The experiment proceeds to a gill score of 2 which is a clinical score at which most commercial treatments for the disease occur. Appetite and fish well being are not affected up to this score. This study will inform on the susceptibility of different salmonid strains and species and provide data that will be directly relevant to the national risk assessment for the effects of fish farming on wild salmonids.
In this experiment 320 salmon (160 farm strain + 160 wild strain) and 160 brown trout will be used.