Infectlous pancreatlc necrosls (IPN) Is a virus dlsease that has been an Increaslng problem for Norweglan salmon farmlng lndustry. A major question is whether there Is a causal link between reduced water quality due to Intensive production and Increased frequency Of IPN-outbreaks. In the present study, we have examlned the effects of longterm exposure to three dlfferent concentrations of carbon dloxlde (CO2) and low pH on growth and susceptlbllity to IPN virus in Atlantic salmon.