Abstract
Pancreas disease (PD) is a serious disease of farmed Atlantic salmon, Salmo salar L . It was first described in Scotland in 1976 and has subsequently been found in Ireland, Norway and North America. The disease primarily affects Atlantic salmon smolts during their first year at sea and losses can be as high as 50% of the yearly smolt input, but more recently it has become more common in one sea winter fish. Although there have been numerous descriptions of presenting signs or of specific lesions, there has been no complete sequential clinical and histopathological description of the disease. The present study was therefore based on detailed observations on two farms in expectation of typical outbreaks of PD during 1991 and the subsequent evaluation of these findings in the context of a wide range of diagnostic submissions to the Department of Agriculture & Rural Development, Northern Ireland laboratory from 1992 to 1996. It aims to accurately describe and set diagnostic criteria for this important economic disease of farmed Atlantic salmon.