Movements and dispersal of farmed Atlantic salmon following a simulated-escape event
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One of the major challenges for understanding the ecological impact of escaped farmed Atlantic salmon (Salmo salar L.) is predicting their dispersal patterns after an escape event. Here, we quantify the behaviour of escaped farmed salmon using a simulated-escape experiment within a Norwegian fjord system. Thirty-seven individuals were tagged with acoustic transmitters and their spatial distribution, horizontal movements and diving behaviour was monitored throughout the fjord and accompanying rivers using 29 acoustic receivers. A rapid movement away from the release site occurred. There was no movement into the rivers feeding the fjord and there was no preference for residence at the fish farms: nearly a third of the individuals had a final detection in the outer part of the fjord and no detections occurred from approximately 2 months after release. As it is unlikely that all fish died or remained undetected within the study area it is reasonable to assume that a substantial proportion of the fish moved out of the fjord system. If a recapture program is not implemented immediately after an escape event, we recommend spreading potential recapture efforts over a relatively large area.
KeywordsFish farms Atlantic salmon Escape patterns Acoustic telemetry
This study was funded by the Fisheries Directorate and the Directorate for Nature Management and was conducted as collaboration between the Norwegian Institute for Nature Research (NINA) and Norwegian Institute for Water Research (NIVA). We would especially like to thank Aqua Gen Marine for very helpful collaboration. They supplied farmed Atlantic salmon, premises for tagging the fish, and deployed out receivers on some of their farms in the fjord. We would also like to thank Marine Harvest Norway AS and Lerøy Hydrotech AS for placing out receivers at some of their farms. Finally, we would like to thank Jo Arve Alfredsen, NTNU, for assistance under field work spring 2011.
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