396 
Fishery Bulletin 107(3) 
Table t 
Reflex actions that were consistently present in 20 control (unstressed) Atlantic cod (Gadus morhua ) and used to measure reflex 
impairment in fish exposed to stressors (forced swimming, net abrasion, and air exposure) associated with capture by Danish 
seines. 
Reflex 
Description 
1. Body flexion 1 
Fish flexed body when placed on a flat surface (sorting table). 
2. Body flexion 2 
Fish flexed when restrained. 
3. Head complex 
Restrained fish presented alternating mouth gaping and operculum flaring, as if gasping for air. 
4. Operculum 
Restrained fish either flared operculum rigidly open or strongly clamped operculum shut when 
operculum was lifted with a probe. 
5. Gag 
Restrained fish gaged when back of throat was stimulated with a probe. 
6. Vestibular-ocular 
Restrained fish tracked observer when it was rotated around long axis. 
response (VOR) 
7. Tail flexion 
Fish held under belly flexed when tail flanks were stroked by hand along long axis. 
for additional growth and later marketing (CBA pur- 
poses). The Danish seine is the most commonly used 
fishing gear for CBA, and the stressors tested in this 
study, forced swimming, net abrasion, and air exposure, 
are typical in and inherent to this type of fishing gear. 
A series of experiments were conducted to construct a 
RAMP (Reflex Action Mortality Predictor) curve for cod 
exposed to these stressors and we broadly followed the 
three step procedures in Davis (in press) to validate 
reflex impairment as an indicator of vitality. 
First we established appropriate procedures for test- 
ing fish reflexes by determining consistent reflexes for 
testing; we established the effect of repeated reflex test- 
ing in control fish to test whether cod were distressed 
by the testing procedure; we determined the recovery 
time after exposure to a stressor; and we determined 
the effect of disturbance from repeated netting of fish 
from a holding tank. 
Second we established experimental methods for ex- 
posing fish to key stressors and conducted stress experi- 
ments to determine the effect of air exposure and the 
combined effect of forced swimming, net abrasion, and 
air exposure on reflexes and survival. 
Third after observing immediate and delayed mortal- 
ity, we correlated reflex impairment and mortality by 
producing RAMP curves for the effect of air exposure 
and the combined effect of forced swimming, net abra- 
sion, and air exposure. 
Materials and methods 
Experimental fish 
Cod were hatched and later reared in net pens at Auste- 
voll Research Station (60°05'17"N 5°15'50"E), Austevoll, 
Norway. Five months prior to the experiments, fish 
were moved (after six months in net pens) to indoor 
-1600-L green fiberglass tanks with rounded corners 
(145 cm x 145 cm x 100 cm depth, water depth 80 cm), 
supplied with aerated sea water (8.0 ±1.0°C), and fed 
standard commercial diets (Skretting Ltd, Stavanger, 
Norway) to satiation by using 24-hr disc feeders (1% 
of total biomass per day) under a continuous daylight 
regime. A total of 169 fish (31-49 cm total length [TL]) 
were tested for reflex impairment and mortality experi- 
ments. In order to maintain independence of observation 
no fish was used more than once. 
Step 1: Consistent reflexes and 
appropriate procedures for reflex testing 
A number of reflex actions in cod for potential inclusion 
in this study were identified based on previous work (e.g., 
Davis, 2007) and preliminary trial and error screen- 
ing on fishing vessels and in the laboratory. In order 
to identify the reflexes for testing and to standardize 
methods and stimuli to elicit these reflex actions, twenty 
cod were initially tested. Seven reflexes were found to be 
consistently present in control fish (Table 1). For subse- 
quent reflex impairment tests, the reflexes were scored 
as 1 (present) if a vigorous response was evident, or 0 if 
the response was not present or of weak or questionable 
strength. Reflex scoring insured consistent, high quality 
response data (Davis, in press). 
To test reflex actions, fish were initially placed on 
a flat surface, corresponding to a sorting table on a 
fishing vessel and observed for spontaneous body flex- 
ing. Then fish were placed and held in a restraining 
device (Fig. 1) consisting of two plastic pieces (60 cm 
length x 10 cm width), each lined with a sponge to con- 
tact and hold fish, and connected at one end to form a 
hinge, while the other end was secured with a Velcro 
strap. Fish were then observed for body flexion in re- 
sponse to restraint. The restrained fish were then tested 
for reflexive head movements (a spontaneous alternating 
head and operculum movement), operculum movement 
(either tight closure or flaring after having been lifted 
with a probe), gag in response to throat stimulation, 
and vestibular-ocular response (eye rotation while the 
fish was rotated around its long axis). Finally fish were 
released from restraint and tested for body flexion in 
