456 
Fishery Bulletin 107(4) 
Table 3 
Righting behavior exhibited by crabs exposed to different levels of freezing exposure measured in degree-hours (°h, the product 
of temperature [in degrees Celsius] and time [in hours]). Values in parentheses represent the proportions of crabs attempting to 
right and righting successfully that survived. 60.9% of surviving Chionoecetes bairdi (Tanner crab) and 52.6% of surviving C. 
opilio (snow crab) made no attempt to right. 
Exposure 
level (°h) 
No. of 
crabs tested 
No. of crabs 
attempting to right 
(% survival) 
No. of crabs 
righting successfully 
(% survival) 
Range of 
righting time 
(seconds) 
C. opilio 
-2 
20 
10(90) 
7 (100) 
19-92 
-3 
10 
4(100) 
0 
— 
-4 
10 
3(67) 
2(100) 
90-98 
-5 
10 
4(50) 
2(50) 
80-88 
-6 
20 
8(25) 
0 
— 
-8 
22 
3(33) 
0 
— 
-10 
10 
0 
0 
— 
Overall 
100 
32 (62.5) 
11 (90.9) 
19-98 
C. bairdi 
-2 
20 
13 (92) 
9(89) 
5-110 
-3 
10 
2(50) 
1(100) 
12 
-4 
10 
1(100) 
0 
— 
-5 
10 
1 (100) 
0 
— 
-6 
20 
5 (40) 
0 
— 
-8 
20 
1(0) 
0 
— 
-10 
10 
0 
0 
— 
Overall 
100 
23 (73.9) 
10 (80.0) 
5-110 
exposure range. When two different temperatures (-10° 
and -20°C) were used to create fixed exposure levels 
(°h) differences in initial autotomy were not different 
for either species (ANOVA, P>0.60). In C. opilio, the 
chelipeds were infrequently lost (4.8%) and limb losses 
increased in the anterior to posterior direction (Fig. 2). 
Losses were more uniformly distributed in C. bairdi. 
Although direct comparisons with the initial limb losses 
were not possible because of high mortalities in some 
treatments, autotomies increased substantially over 
the 9-day holding period, especially in crabs exposed to 
freezing temperatures for longer periods (Fig. 1). 
Righting behavior 
Crabs of both species attempted to right themselves 
when placed in the water bath after exposure to freez- 
ing temperatures (Table 3), but the total number of suc- 
cessful crabs was relatively low (10-11%). Most of the 
crabs able to right themselves survived over the 9-day 
follow-up period (90.9% of C. opilio, 80% of C. bairdi ). 
However, neither attempts to right nor time to right were 
good predictors of subsequent survival because 52.6% 
of surviving C. opilio and 60.9% of surviving C. bairdi 
made no attempt to right. Also, crabs demonstrating fast 
righting times (e.g., 12 sec) sometimes died. Overall, 
successful righting was a relatively good predictor of 
survival, but neither the lack of righting nor attempts 
to right were good predictors of mortality. 
Limb pair 
Figure 2 
Identities of limbs autotomized by Chionoecetes bairdi 
(Tanner crab) and C. opilio (snow crab) after exposure 
to freezing conditions (all treatments combined). Limb 
pairs were numbered 1-5, from the chelipeds to the 
posteriormost walking legs. 
Cold exposure, mortality, and reflex impairment 
Crab mortality increased substantially with increas- 
ing exposure to freezing stress (Fig. 3), as expected. 
With exposures ranging from -2 to -4°h , mortalities 
