Timing is everything: Survival of Atlantic salmon Salmo salar postsmolts during events of high salmon lice densities
MetadataShow full item record
- Scientific publications 
1. Atlantic salmon in aquaculture act as reservoir hosts and vectors of parasites like salmon lice and this parasite is shown to harm wild salmonid populations. 2. In this study, n = 29,817 tagged Atlantic salmon were studied in four release trials. Half of the released fish were given prophylactic treatment against lice, the other half represented sham control fish. We used a nested design comparing years with low and high lice density and seasonal dynamics in infestation pressure. The released Atlantic salmon thus experienced highly variable lice infestation pressures, which we linked to survival and growth in returning fish. The fish were released in a protected ‘National Salmon Fjord’ and n = 559 Atlantic salmon were recaptured after spending 1–4 years at sea. 3. In most experimental groups 1%–2.5% of the fish were recaptured at return. However, survival of unprotected fish was extremely low for the trial released at the highest density of lice: only 0.03% of these Atlantic salmon returned to the river, compared to 1.86% in the protected group. 4. Synthesis and applications. We document that high lice density can cause more than 50 times higher mortality risk in Atlantic salmon on their sea migration, even in a fjord with protected status. Fine-tuned and hard-to-predict year-to-year differences in timing, both for the wild smolt migration and the population build-up of lice released from aquaculture, means life or death to wild salmon. Management actions such as spatial segregation of farmed fish and lice (e.g. closed farm pens), and/or moving farms away from vulnerable habitats for wild salmonids (fjords and coastal areas), may be needed to ensure sustainable coexistence of wild and farmed Atlantic salmon.
JournalJournal of Applied Ecology
Copyright© 2020 The Authors.
Showing items related by title, author, creator and subject.
Selection against individuals from genetic introgression of escaped farmed salmon in a natural population of Atlantic salmon Wacker, Sebastian; Aronsen, Tonje; Karlsson, Sten; Ugedal, Ola; Diserud, Ola Håvard; Ulvan, Eva Marita; Hindar, Kjetil; Næsje, Tor (Peer reviewed; Journal article, 2021)The viability of wild Atlantic salmon populations is threatened by genetic introgression from escaped farmed salmon. Farmed Atlantic salmon are genetically improved for important commercial traits and a life in captivity ...
Oppvandring og fordeling av laks i Osenvassdraget i Molde kommune: Resultater fra undersøkelser i 2014 Ulvan, Eva Marita; Bremset, Gunnbjørn; Aronsen, Tonje; Thorstad, Eva Bonsak; Solem, Øyvind; Økland, Finn; Havn, Torgeir Børresen (NINA Rapport;1184, Research report, 2015-07-01)Ulvan, E.M., Bremset, G., Aronsen, T., Thorstad, E.B., Solem, Ø., Økland, F., Havn, T. B. 2015. Oppvandring og fordeling av laks i Osenvassdraget i Molde kommune: Resultater fra undersøkelser i 2014. - NINA Rapport 1184. ...
Forseth, Torbjørn; Fiske, Peder; Thorstad, Eva B. (Rapport fra vitenskapelig råd for lakseforvaltning;2b, Research report, 2010)Anon. 2010. Vedleggsrapport med vurdering av måloppnåelse for de enkelte bestandene. Rapport fra Vitenskapelig råd for lakseforvaltning nr 2b, 516 s. Rapporten inneholder en vassdragsvis vurdering av måloppnåelse for 227 ...