Blar i forfatter "Sivertsgård, Rolf"

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    • Area protection may reduce salmon louse infection risk to wild salmonids 

      Bjørn, Pål Arne; Sivertsgård, Rolf; Finstad, Bengt; Nilsen, Rune; Serra-Llinares, Rosa Maria; Kristoffersen, Roar (Journal article; Tidsskriftartikkel; Peer reviewed, 2011-05-30)
      ABSTRACT: Salmon louse <i>Lepeophtheirus salmonis</i> Krøyer infection levels in both wild sea trout <i>Salmo trutta</i> L. and sentinel Atlantic salmon <i>Salmo salar</i> 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 ...

    • Changes in swimming depths of Atlantic salmon Salmo salar post-smolts relative to light intensity 

      Davidsen, Jan Grimsrud; Plantalech Manel-la, Nuria; Thorstad, E.B; Rikardsen, Audun H.; Økland, F.; Sivertsgård, Rolf; Finstad, B; McKinley, R.S; Diserud, O. H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2008-06-22)
      Eight hatchery-reared Atlantic salmon Salmo salar post-smolts, implanted with acoustic depth sensing transmitters and manually tracked for 5-12 h in the Hardangerfjord (Norway), spent most of their time (49-99%) at 1-3 m depth during the day, whereas four of seven fish tracked were found close (<0.5 m) to the surface at night, with a strong negative cross-correlation between general swimming depth ...

    • Vertical movements of Atlantic salmon postsmolts relative to measures of salinity and water temperature during the first phase of the marine migration 

      Davidsen, Jan Grimsrud; Plantalech Manel-la, Nuria; Thorstad, E.B; Økland, F.; Sivertsgård, Rolf; McKinley, R.S; Finstad, B. (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)
      The migratory behaviour of hatchery-reared Atlantic salmon, Salmo salar L., post-smolts during the first phase of the marine migration was examined to assess their susceptibility to salmon lice, Lepeophtheirus salmonis (Krøyer), infestations. Swimming depths of eight post-smolts relative to the measured salinity and temperature were monitored for an average of 11.4 h following release outside the ...