An evaluation of the relative risks of infectious salmon anaemia transmission associated with different salmon harvesting methods in Scotland

In aquaculture, harvesting presents an unavoidable risk of disease transmission. The spread of the disease infectious salmon anaemia appears to have been associated with harvesting in both Scotland and Norway. An assessment is made of the relative risks of disease transmission associated with various different means of harvesting farmed salmon based on the assumption that best practice is followed for each harvest method. The assessment is qualitative, quantitative data being absent for most of the processes involved. Slaughter on the farm risks the spread of infection to adjacent farms, whereas, infection at a processing plant may be rebroadcast by well-boats. The risks associated with transporting live fish in cages and of storing live fish near centralised processing plants are discussed. Provided the vessel does not release contaminated water in the vicinity of salmon farms, transport of live fish directly to the processing plant for immediate slaughter by sea may be the safest means of collecting harvest.