Frank Nilsen

Publications (71) View all

• Source

  Available from: Frank Nilsen

  Article: Salmon lice - impact on wild salmonids and salmon aquaculture.

  O Torrissen, S Jones, F Asche, A Guttormsen, O T Skilbrei, F Nilsen, T E Horsberg, D Jackson
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  ABSTRACT: Salmon lice, Lepeophtheirus salmonis, are naturally occurring parasites of salmon in sea water. Intensive salmon farming provides better conditions for parasite growth and transmission compared with natural conditions, creating problems for both the salmon farming industry and, under certain conditions, wild salmonids. Salmon lice originating from farms negatively impact wild stocks of salmonids, although the extent of the impact is a matter of debate. Estimates from Ireland and Norway indicate an odds ratio of 1.1:1-1.2:1 for sea lice treated Atlantic salmon smolt to survive sea migration compared to untreated smolts. This is considered to have a moderate population regulatory effect. The development of resistance against drugs most commonly used to treat salmon lice is a serious concern for both wild and farmed fish. Several large initiatives have been taken to encourage the development of new strategies, such as vaccines and novel drugs, for the treatment or removal of salmon lice from farmed fish. The newly sequenced salmon louse genome will be an important tool in this work. The use of cleaner fish has emerged as a robust method for controlling salmon lice, and aquaculture production of wrasse is important towards this aim. Salmon lice have large economic consequences for the salmon industry, both as direct costs for the prevention and treatment, but also indirectly through negative public opinion.
  Journal of Fish Diseases 01/2013; · 2.00 Impact Factor
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  Available from: Frank Nilsen

  Article: How does sequence variability affect de novo assembly quality?

  R Skern-Mauritzen, K Malde, F Besnier, F Nilsen, I Jonassen, R Reinhardt, B Koop, S Dalvin, S Maehle, H Kongshaug, K A Glover
  Journal of Natural History 01/2013; 47(5-12):901-910. · 0.95 Impact Factor
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  Available from: Frank Nilsen

  Article: Life history and virulence are linked in the ectoparasitic salmon louse Lepeophtheirus salmonis.

  A Mennerat, L Hamre, D Ebert, F Nilsen, M Dávidová, A Skorping
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  ABSTRACT: Models of virulence evolution for horizontally transmitted parasites often assume that transmission rate (the probability that an infected host infects a susceptible host) and virulence (the increase in host mortality due to infection) are positively correlated, because higher rates of production of propagules may cause more damages to the host. However, empirical support for this assumption is scant and limited to microparasites. To fill this gap, we explored the relationships between parasite life history and virulence in the salmon louse, Lepeophtheirus salmonis, a horizontally transmitted copepod ectoparasite on Atlantic salmon Salmo salar. In the laboratory, we infected juvenile salmon hosts with equal doses of infective L. salmonis larvae and monitored parasite age at first reproduction, parasite fecundity, area of damage caused on the skin of the host, and host weight and length gain. We found that earlier onset of parasite reproduction was associated with higher parasite fecundity. Moreover, higher parasite fecundity (a proxy for transmission rate, as infection probability increases with higher numbers of parasite larvae released to the water) was associated with lower host weight gain (correlated with lower survival in juvenile salmon), supporting the presence of a virulence-transmission trade-off. Our results are relevant in the context of increasing intensive farming, where frequent anti-parasite drug use and increased host density may have selected for faster production of parasite transmission stages, via earlier reproduction and increased early fecundity. Our study highlights that salmon lice, therefore, are a good model for studying how human activity may affect the evolution of parasite virulence.
  Journal of Evolutionary Biology 02/2012; 25(5):856-61. · 3.28 Impact Factor
• Article: Twenty‐three novel microsatellite markers developed from Atlantic cod Gadus morhua L. expressed sequence tags

  M. Delghandi, M. S. Wesmajervi, T. Tafese, F. Nilsen
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  ABSTRACT: Twenty-three novel polymorphic microsatellite markers were developed from c. 2000 expressed sequence tags of Atlantic cod Gadus morhua L. Gene identity was determined at 12 loci, confirming the associated microsatellites as type I markers. These microsatellite markers provide useful tools for studies of population genetics and reproductive ecology and for constructing linkage maps of G. morhua.
  Journal of Fish Biology 07/2008; 73(2):444 - 449. · 1.68 Impact Factor
• Chapter: Mortality of Seaward‐Migrating Post‐Smolts of Atlantic Salmon Due to Salmon Lice Infection in Norwegian Salmon Stocks

  J.C. Hoist, P. Jakobsen, F. Nilsen, M. Holm, L. Asplm, J. Aure
  11/2007: pages 136 - 137; , ISBN: 9780470995495