452 
Fishery Bulletin 107(4) 
Table 1 
Reflexes identified as useful for assessing stress in Chionoecetes spp. "Test” is the manipulation required to elicit a stereotypic 
positive response. No response was recorded when no motion was detected in response to repeated testing (modified from Stoner 
et al., 2008) 
Reflex 
Test 
Positive response 
Lost response 
Leg flare 
Lift crab by the carapace, 
dorsum up 
Legs spread wide and to near 
horizontal orientation in strong crabs 
Legs droop below horizontal, with 
no attempt to raise them 
Leg 
retraction 
While holding crab as above, 
draw the forward-most 
walking legs in the anterior 
direction 
Legs retract in the posterior direction, 
or present resistance to the motion in 
weakened crabs 
No resistance to the manipulation 
occurs 
Chela 
closure 
Observe for motion or hold the 
chelae in the fingers 
Chelae open and close with or without 
manipulation. In weakened crabs the 
chelae may close slowly, or show low 
resistance to manual opening 
No motion is detected in the 
chelae under manipulation 
Eye 
retraction 
Touch the eye stalk with a 
blunt probe, or lift the eye 
stalk from its retracted 
position 
Eye stalk retracts in the lateral 
direction below the carapace hood, 
or shows resistance to lifting 
No motion or resistance to 
manipulation occurs in the 
eye stalk 
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 to cover the 
smaller mouth parts. The maxillipeds 
droop open or move in an agitated 
manner in weakened crabs 
No motion in the maxillipeds 
occurs 
Kick 
With the crab in ventrum- 
up position, use a sharp 
dissecting probe to lift the 
abdominal flap away from the 
body 
One or more legs or chelipeds move 
quickly in the ventral direction, 
particularly in males. Motion in the 
hind most legs is retained in weakened 
crabs 
No motion in the legs or chelipeds 
occurs 
with a high degree of reliability. More importantly, a 
composite index of reflex impairment (i.e., the simple 
sum of reflex actions lost) provided a graded metric for 
the animal’s condition [0 to 6], and was a good predic- 
tor for mortality in field trials. Relationships between 
reflex impairment and mortality were first explored for 
fishes (Davis, 2002, 2007) and the results were termed 
a reflex action mortality predictor (RAMP) by Davis and 
Ottmar (2006). These recent experiments have shown 
that RAMP models, once established for a species, pro- 
vide reliable predictors independent of crab size, molting 
stage, gender, and injury. The RAMP approach has the 
added benefit of eliminating the need for holding the 
animals tested. 
The subject species of this study were C. bairdi and 
C. opilio. Landings of C. bairdi reached maximum val- 
ues (>100 million pounds) in Alaska during the late 
1970s but have been relatively low since a fisheries 
collapse in the mid-1980s (Herrmann and Greenberg, 
2007). Chionoecetes opilio is distributed more widely, 
from the Sea of Japan to Alaska in the North Pacific 
and through the Arctic Ocean to Atlantic Canada. Dur- 
ing the early 1990s landings for C. opilio exceeded 300 
million pounds in Alaska and over 100 million pounds 
in the North Atlantic (Herrmann and Greenberg, 2007). 
Peak value in Alaska occurred in 1994 at $200 million, 
then declined sharply, with Canadian fisheries in the 
Atlantic now representing >80% of the catch. 
Fishing for Chionoecetes spp. in Alaska is limited 
to baited pots and only males of minimum size may 
be retained. Consequently, all crabs captured in trawl 
fishing are returned to the sea, and large numbers of 
sub-legal-size males and all female crabs caught in 
pots must be returned to the water. Many males ex- 
ceeding minimum size are also returned. Macintosh et 
al. (1996) discussed the magnitude of discards in the 
Bering Sea fishery, noting that discards could represent 
a large source of population mortality if these inciden- 
tally captured crabs die. Because directed fisheries for 
C. bairdi and C. opilio occur primarily during winter 
months in Alaska, the crabs can experience periods of 
freezing temperature and wind chill before being dis- 
carded. For calculations of catch limits for US-managed 
crab fisheries in the Bering Sea, both the retained com- 
mercial catch and the numbers of discarded crabs which 
die due to handling mortality are considered to be part 
