Over-summering behaviour of Atlantic salmon Salmo salar returning to rivers in the Cromarty Firth, north-east Scotland.

ABSTRACT

In 2005, a high percentage (50%) of Atlantic salmon Salmo salar fitted with acoustic transmitters, which entered rivers in the Cromarty Firth area of north-east Scotland, dropped back to the estuary and ascended adjacent rivers after 33-80 days of freshwater residence. Fish residing in non-natal rivers generate mixed stock fisheries, and movements of fish between rivers could increase the risk of disease transmission between catchments.