Ulcerative dermal necrosis, a disease of migratory salmonid fishes in the rivers of the British Isles

Abstract

An account is given of the spread and current incidence of ulcerative Dermal Necrosis (UDN), a disease affecting the skin of mature wild salmonid fishes returning from the sea to spawn. It is estimated that Scottish losses—almost exclusively, Salmon and Sea Trout—were in excess of 51,000 and 38,000 fish, representing 5·7 and 6·0 per cent of the catch in Scotland during 1967 and 1968, respectively. Records show that what appears to have been the same disease last caused heavy losses in the period 1877–1890. Current scientific evidence favours a virus aetiology with secondary fungal infection as the commonest cause of death. At the present level of incidence the disease is unlikely to affect brood stocks seriously—which is as well, because no measures of control are known.