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Comparison of infection risks in farm-exclusion zones (Romsdalsfjord) and farmed zones (Eresfjord/ Karlsøyfjord) for sentinel caged fish

Differences in infestation risks of salmon lice were studied by sentinel cages in three connected fjord sections of the Romsdalsfjord system, Norway. Eresfjord, in the inner part of the fjord system, is without salmon farming activity. Langfjord, in the middle part, has two farms, while Karlsøyfjord, in the outer part, is exposed to extensively salmon farming. Naive hatchery reared Atlantic salmon smolts were placed in duplicated cages in both pelagic and littoral areas of all fjords. After 14 days, salmon lice infestation on the fish was analysed. Eresfjord (no farms) had lowest infestation risks, intermediate risks were found in Langfjord (two farms), while Karlsøyfjord (extensive farming activity) had highest infestation risks. No clear differences between littoral and pelagic areas of the fjord were found. Results shows that sentinel cages can be used as an alternative method to monitor salmon lice infestation pressure in fjord systems, and confirm the relationship between extensive fish farming and risks of lice infestation. The results are therefore relevant for management of salmon farming protection zones in Europe, and the results have recently been submitted for publication.

Reported by

Norwegian Institute Fisheries and Aquaculture Research
University Campus Breivika
N-9291 Tromsø
Norway
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