AEI 5:221-233 (2014)  -  DOI: https://doi.org/10.3354/aei00105

Effects of salmon lice infection on the behaviour of sea trout in the marine phase

Karl Øystein Gjelland1,*, Rosa Maria Serra-Llinares2, Richard David Hedger3, Pablo Arechavala-Lopez2,3,4, Rune Nilsen2, Bengt Finstad3, Ingebrigt Uglem3, Ove Tommy Skilbrei2, Pål Arne Bjørn2

1Norwegian Institute for Nature Research, the Fram Centre, 9296 Tromsø, Norway
2Institute of Marine Research, 58171 Bergen, Norway
3Norwegian Institute for Nature Research, 7485 Trondheim, Norway
4Department of Marine Science and Applied Biology, University of Alicante, 03080 Alicante, Spain
*Corresponding author:

ABSTRACT: Salmon lice Lepeophtheirus salmonis Krøyer may affect survival and growth of anadromous salmonids through physiological stress and/or behavioural changes. Using acoustic telemetry tracking, we investigated the behaviour of 30 infected sea trout Salmo trutta throughout the summer in a fjord with very high salmon lice infection pressure. Most of the tracked sea trout adopted a movement pattern expected to suppress salmon lice infestation, as they showed a strong preference for fresh or brackish water, spending most of the time close to a river outlet or even migrating into the river. Highly infested sea trout preferred shallower depths, associated with lower salinity. The fish lost to predation stayed further away from the river outlet than non-predated fish, and were likely subjected to a stronger infection pressure. Half of the tracked group were treated with a salmon lice prophylaxis, emamectin benzoate. The effect of treatment on infestation was monitored in a separate group held in a sea cage and found to be moderate; the mortality in this group was associated with infestation by motile lice stages. In contrast, treatment was not found to have an effect on tracked fish behaviour. It is likely that some physiological and behavioural responses to high salmon lice infection pressure may be present even after a prophylaxis treatment, in particular when the treatment is given after exposure to salmon lice infection. We conclude that increased salmon lice infection pressure associated with altered salmon farming practice may have the potential to influence the marine behaviour and growth of sea trout.


KEY WORDS: Lepeoptheirus salmonis · Sea lice · Anadromy · Host–parasite interactions · Emamectin benzoate · Behavior · Tracking · Telemetry


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Cite this article as: Gjelland KØ, Serra-Llinares RM, Hedger RD, Arechavala-Lopez P and others (2014) Effects of salmon lice infection on the behaviour of sea trout in the marine phase. Aquacult Environ Interact 5:221-233. https://doi.org/10.3354/aei00105

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