Background

 

Reports of wild Atlantic salmon (Salmo salar) returning to Scottish rivers with inflamed, swollen bleeding vents were received in early June 2007. By the end of July over 50 rivers had reported similar observations. Apart from the affected vent, the fish appear to be in good physical condition. So far, the syndrome appears to be mainly restricted to adult male and female Atlantic salmon one sea-winter fish (i.e. grilse), and particularly prevalent among ‘fresh run’ fish. A smaller number of two sea-winter fish were also reported showing signs of the condition. Neither sea trout (S. trutta) nor farmed Atlantic salmon have been affected by the condition. Investigations were carried out by Fisheries Research Services (FRS) in an attempt to establish the cause and extent of the problem.