Investigation of a wild fish kill on the River Tyne

A wild adult Atlantic salmon and sea trout fish kill occurred on the River Tyne in the summer of 2003. Similar mortalities have occurred in past summers on this river. The mortality in 2003 was attributed to Vibrio anguillarum and it is suggested that infection with this pathogen was most likely exacerbated by the low water flow, which impaired fish movement upstream and lead to large aggregations of fish, and high water temperatures, which increased the replication rate of the bacteria and stressed the fish. Both of these environmental conditions would have favoured fish-to-fish transmission of the bacteria, and increased the mortality rate associated with the pathogen.