Risk of Sea Lice Infestation

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					Risk of Sea Lice Infestation

     R.S. McKinley, B. Finstad
  (NINA), P.A. Bjorn, F. Okland, G.
     Wagner and E. Thorstad.
background
 I   naturally occurring ectoparasite
 I   lice infestation levels in wild and
     farmed salmon vary
     geographically
 I   high infestation levels of lice are
     known to affect osmoregulatory
     function
 I   infestation levels vary among
     salmonids
 I   what lice level affects performance
objective


I   Determine if cardiac and swimming
    performance in adult Atlantic
    salmon is affected by increasing
    levels of sea lice infestation
         Lice Infestation

G Evidence 0.7-1.6 lice g-1 cause morbidity
G At what level is overall health at risk?
  N food acquisition

  N migration (swimming performance)

  N predator avoidance

  N reproduction
Lice levels in the wild
 I   vary considerably and among
     species from 0.002 to 2.1 lice g-1 (1
     to 200 lice per individual)
 I   susceptibility to lice appears
     related to time spent by fish in
     nearshore waters
 I   sea trout/arctic charr appear
     more susceptible than Atantic
     salmon
Levels examined
 I Moderate:  0.13 lice g-1
 I Low: 0.02 lice g -1
 I Controls: no lice
                 Methods
G   Swimming Performance Testing
     N Ucrit = V + (t ·_t -1) _v, in BL s -1



G   Cardiac Output
    N (Q) by direct measure, in ml min -1 kg-1


G   blood parameters
    N Chloride, glucose, cortisol
               Dorsal
               Aorta
  Gill      Gill             Sinus
  Arch      Filaments AtriumVenosus




 Doppler Ventral Bulbus Ventricle
Flow Probe Aorta Arteriosus
Results
                                                     Moderate
                                                     Low
                                                     Control
           3.0                                       Reg.
                                                     C.I.



           2.5
 Ucrit
(bl s-1)

           2.0


                  r ? = 0.24
           1.5    p = 0.017

                 0.00     0.05      0.10      0.15        0.20
                           Relative Infestation
                                        -1
                                 (lice g )
         2.8
         2.7
         2.6
         2.5
         2.4
 Ucrit
(bl s-1) 2.3      *
         2.2
         2.1
         2.0
         1.9



         0.0
               Moderate        Low         Control
                          Lice Treatment
                      Moderate
                50    Low
                      Control
                40

  Cardiac
               30
  Output
(ml g-1 min-1)
                20

                10

                 0

                70

                60
    Heart
    Rate
 (beats min-1) 50

                40



                 0


               0.8


                0.6
   Stroke
  Volume
(ml beat-1 g-1) 0.4

               0.2


               0.0
                       Rest                    Ucrit
                              Activity State
                                            Rest
            200
                  A
                           *a               Ucrit
                                                    b
            150
                                        b
Chloride
      -1
(mg ml ) 100

             50

              0

              6   B
              5        a            *           *
 Glucose      4                    a
       -1
(mg ml )                                      b
              3

              2

              1

              0

            300   C
            250
                                    *
Cortisol
      -1    200
(ng ml )
            150

            100

             50

              0
                      Moderate     Low        Control
                             Lice Infestation
Summary
 G Swimming performance significantly
   decreases at moderate levels of sea lice
 G Moderate levels of lice
     >   reduce swimming performance
     >   contributes osmotic imbalance
     >   chronic stress response
     >   alters heart rate