Stoner et al: An assessment of discard mortality for two Alaskan crab species, based on reflex impairment 
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Table 1 
Reflexes identified as useful for assessing stress in Chionoecetes spp. The test was the manipulation required to elicit a stereo- 
typic response. Characteristic strong and weak responses are described. When no motion was detected in response to repeated 
testing a “No response” score was recorded. 
Reflex 
Test 
Strong response 
Weak response 
Leg flare 
Lift crab by the carapace, dorsum 
up. 
All legs spread wide and high, near 
horizontal orientation. 
Legs droop below horizontal. 
Leg retraction 
While held as above, draw the 
forward-most walking legs in the 
anterior direction. 
Legs respond with a strong 
retraction in the posterior 
direction. 
Leg retraction is diminished. 
Low resistance to legs pulled 
forward. 
Chela closure 
Observe for motion or hold the 
chelae in the fingers. 
Chelae open and close rapidly 
without manipulation. 
Manipulation results in immediate 
strong closure. 
Chelae close slowly and weakly 
upon manipulation, or with 
a delayed response. Low 
resistance to manual opening of 
the chelae. 
Eye retraction 
Touch the eye stalk with a blunt 
probe, or lift the eye stalk from its 
retracted position. 
Eye stalk retracts strongly in the 
lateral direction below the carapace 
hood. 
Eye stalk retracts weakly or 
demonstrates low resistance to 
lifting. 
Mouth closure 
If closed, attempt to open (extend) 
the 3 rd maxillipeds with a sharp 
dissecting probe. If open, draw the 
maxillipeds downward. 
3 rd maxillipeds retract quickly and 
strongly to cover the smaller mouth 
parts. 
The maxillipeds droop open or 
move in an agitated manner, but 
do not close tightly. 
Kick 
With the crab in ventrum-up 
position, use a sharp dissecting 
probe to lift the abdominal flap 
away from the body. 
Immediate, strong agitation of the 
legs and chelipeds. Males respond 
more strongly than females. 
Testing with the latter often 
requires greater extension of the 
entire abdominal flap. 
Response is diminished or slow. 
Motion is observed in only the 
hind-most legs. 
169°45'W) in depths ranging from 35 to 75 m. Crabs 
were collected from 22 locations where the bottom was 
relatively homogenous muddy sand. Temperature on the 
bottom and near surface ranged from -0.3° to 1.7°C and 
from 3.5° to 4.9°C, respectively. 
An important objective of the trawling operation was 
to acquire crabs in various states of stress and injury 
for assessment and monitoring. Also, we wanted to test 
crabs that had experienced the suite of stressors typical 
of those produced during encounters with fishing gear 
used in the Bering Sea bottom-trawl fishery. Therefore, 
the crabs were collected in various locations around 
a commercial trawl by means of recapture nets (see 
Rose, 1999). The main trawl was a two-seam Alfredo 
bottom trawl (with headrope and footrope lengths of 
36 and 54.6 m, respectively) similar to that used from 
many vessels in the Bering Sea. The center section of 
the footrope was composed of 46-cm diameter rounded 
cones separated by approximately 70-cm long sections 
of 20-cm diameter disks. The forward 14.2 m of the 
footrope on each wing of the trawl was made of 20-cm 
disks strung over a 19-mm long link chain. These sec- 
tions were not directly attached to the netting panel 
above them, and thus formed so-called “flying wings.” 
Extending forward from the trawl, 27.4-m bridles, made 
of bare cable, were attached to the upper wings and the 
same lengths of cable, covered with 9-cm diameter rub- 
ber disks, were attached to the lower wings. Ahead of 
these were 88 m of 4.8-cm diameter combination rope 
and 27.4 m of bare cable, leading to the trawl doors. The 
main trawl was towed with an open codend. 
The recapture nets were small 2-seam trawls with 
longer headropes than footropes (14.3 m and 12.0 m, 
respectively). The long headrope maximized escape of 
fish, and the small diameter (5-cm) footropes were used 
to enhance crab capture. These nets were fished directly 
behind the main net sweeps, wings, or footrope. In some 
cases, two recapture nets were fished simultaneously 
at different locations. As a control for damage in the 
recapture nets, the nets were also fished ahead of the 
main trawl, capturing crabs with no previous damage. 
Tows were short (15 minutes) so that the stress or dam- 
age to crabs was created by the main trawl gear, and 
less by packing within the net or handling. However, 
evaluation of gear impact was not the primary goal of 
this cruise. 
Once a recapture net was hauled on deck, the volume 
of the catch (normally comprising Gadus macrocephalus 
