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Aquaculture Environment Interactions

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AEI 1:233-244 (2011)  -  DOI:

Area protection may reduce salmon louse infection risk to wild salmonids

Pål Arne Bjørn1,2,*, Rolf Sivertsgård3, Bengt Finstad4, Rune Nilsen1,2, Rosa Maria Serra-Llinares1,2, Roar Kristoffersen3

1Nofima Marine, 9291 Tromsø, Norway
2Institute of Marine Research, 58171 Bergen, Norway
3Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway
4Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway

ABSTRACT: Salmon louse Lepeophtheirus salmonis Krøyer infection levels in both wild sea trout Salmo trutta L. and sentinel Atlantic salmon Salmo salar L. smolts were investigated inside and outside a temporary protected zone with limits on fish farming in the intensively farmed Romsdalsfjord system. Wild sea trout outside the protected zone had higher prevalence and significantly higher abundances than those inside the zone. Furthermore, sentinel caged Atlantic salmon smolts confirmed significant ­differences in infection pressure: Eresfjord (non-farmed inner part of the protected zone) had the lowest infection risk, a moderate risk was found in Langfjord (intermediately farmed middle part of the protected zone), while Karlsøyfjord (intensively farmed area outside the protected zone) had the highest infection risk. No clear bias between the near-shore and pelagic areas of the fjord were found, although significant differences between pelagic and near-shore cages were occasionally observed. Results show that small sentinel cages can be used as an alternative method to monitor the infection pressure in a fjord system. Overall, our results indicate that wild salmonids may benefit from the protection zone. However, the infection level on wild sea trout inside the temporary protected zone was higher compared to completely farm-free fjords in Norway, and infection levels likely to have a negative physiological impact on wild sea trout were found. This may indicate that the zone is too small to have the necessary protective effect against salmon lice.

KEY WORDS: Wild salmonids · Salmon lice · Norwegian salmon fjords · Management · Aquaculture

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Cite this article as: Bjørn PA, Sivertsgård R, Finstad B, Nilsen R, Serra-Llinares RM, Kristoffersen R (2011) Area protection may reduce salmon louse infection risk to wild salmonids. Aquacult Environ Interact 1:233-244.

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