High connectivity of salmon farms revealed by aggregation, residence and repeated movements of wild fish among farms.

The article presents a study that determines the farm abundance and spatio-temporal distribution of Pollachius virens in a fjord system with concentrated salmon cage aquaculture in Øksfjord, Northern Norway. It notes on the use of video counting to estimate the abundance of the saithe at various depths, of acoustic transmitters to study its movement in the farms, and of passive listening stations to monitor its spatio-temporal distribution. It reveals the abundance of the saithe in both farms during the release of tagged saithe and discloses its periodic movement from release farm to natural areas. It entails that understanding fish movements can minimise the outbreaks of disease in fish farms and in the populations of wild fish in adjacent areas.