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
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
G
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
0.13 lice g-1
I Low: 0.02 lice g -1
I Controls: no lice
I Moderate:
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
Arch
Sinus
Gill
Filaments AtriumVenosus
Doppler Ventral Bulbus Ventricle
Flow Probe Aorta Arteriosus
Results
Moderate
Low
Control
Reg.
C.I.
3.0
Ucrit
(bl s-1)
2.5
2.0
1.5
r ? = 0.24
p = 0.017
0.00
0.05
0.10
0.15
Relative Infestation
-1
(lice g )
0.20
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
Lice Treatment
Control
50
Moderate
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
Ucrit
*a
A
200
b
b
150
Chloride
-1
(mg ml ) 100
50
0
6
B
a
5
Glucose
-1
(mg ml )
*
*
a
4
b
3
2
1
0
300
250
Cortisol
-1
(ng ml )
C
*
200
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