The interaction between water currents and salmon swimming behaviour in sea cages
Journal article, Peer reviewed
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Original versionJohansson D, Laursen F, Fernö A, Fosseidengen JE, Klebert P, et al. (2014) The Interaction between Water Currents and Salmon Swimming Behaviour in Sea Cages. PLoS ONE 9(5): e97635. doi:10.1371/journal.pone.0097635 10.1371/journal.pone.0097635
Positioning of sea cages at sites with high water current velocities expose the fish to a largely unknown environmental challenge. In this study we observed the swimming behaviour of Atlantic salmon (Salmo salar L.) at a commercial farm with tidal currents altering between low, moderate and high velocities. At high current velocities the salmon switched from the traditional circular polarized group structure, seen at low and moderate current velocities, to a group structure where all fish kept stations at fixed positions swimming against the current. This type of group behaviour has not been described in sea cages previously. The structural changes could be explained by a preferred swimming speed of salmon spatially restricted in a cage in combination with a behavioural plasticity of the fish.