48 
Fishery Bulletin 11 HI) 
Table t 
Number of crabs assessed and size ranges for each species and sex combination after they were captured behind 3 sections 
of bottom trawl gear, or with a control net. Size ranges, carapace width for snow ( Chionoecetes opilio) and southern Tanner 
crabs (C. bairdi) and carapace length for red king crab ( Paralithodes camtschaticus ) are given in millimeters. The three gear 
components were the footrope wings or extensions, the center of the footrope, and the sweep. For red king crab only, a fourth 
component was added, a sweep raised off of the seafloor (Rose et al., 2010). 
Snow crab Southern Tanner crab Red king crab 
Male 
Female 
Male 
Female 
Male 
Female 
No. Size range 
No. Size range 
No. Size range 
No. Size range 
No. Size range 
No. Size range 
Control 
467 
50-130 
154 
54-92 
567 
62-148 
157 
56-100 
448 
53-183 
433 
82-145 
Sweep 
407 
47-126 
218 
52-93 
281 
60-147 
518 
59-98 
370 
64-188 
226 
63-150 
Raised sweep 
321 
63-179 
278 
68-148 
Footrope center 
991 
46-140 
353 
50-85 
677 
50-145 
756 
49-102 
753 
69-189 
393 
68-164 
Footrope wing 
696 
48-130 
540 
50-110 
288 
51-143 
494 
52-97 
203 
61-167 
263 
70-156 
Most southern Tanner and snow crabs captured be- 
hind the main trawl components had all reflexes pres- 
ent (76-93% reflex score of 0, Fig. 3), and the next 
most frequent category was dead crabs (reflex score of 
6, no reflexes present) upon capture (2-17%). Similarly, 
a substantial majority (66-83%) of red king crab cap- 
tured behind the trawl gear was uninjured and had all 
reflexes present. Very few of these animals died during 
holding. Of the red king crab, 6% were dead upon cap- 
ture, making up 71% of mortalities. Therefore, nearly 
all of the observed crabs were either extremely likely to 
survive or moribund; relatively few crabs displayed an 
intermediate condition where the holding and RAMP 
results were critical to estimation of their probability 
of mortality. 
For both red king and southern Tanner crabs, the 
control net yielded 97% uninjured crab with all reflexes 
present and no crabs were dead upon capture. Snow 
crab had more immediate mortalities in the control net 
(2%) and only 88% had all reflexes present. Mortality 
estimates for crabs from the control nets (snow crab 
7.1%, southern Tanner crab 8.5%, and red king crab 
2.9%) were significantly lower than the estimates for 
crabs captured behind trawl components. 
Estimates of the rates of mortality due to contact 
with the trawl gear, adjusted for capture and handling, 
were below 16% (Fig. 4), with the exception of red king 
crab that encountered the wing section of the footrope, 
for which mortality was estimated at 31%. Overall, 
estimated mortality rates for all 3 species were sig- 
Table 2 
Number of crabs held to observe delayed mortality and resulting mortality rates by reflex score (number of 
reflexes missing; 6 reflexes were assessed) and species for snow crab ( Chionoecetes opilio), southern Tanner 
crab (C. bairdi), and red king crab (Paralithodes camtschaticus). Crabs from Stoner et al. (2008) were included 
for both Chionoecetes species. 
Number of reflexes missing 
None 
missing 
None 
missing + 
injury * 
1 
2 
3 
4 
5 
All 6 
missing 
Snow crab 
500 
— 
78 
70 
57 
79 
67 
61 
Southern Tanner Crab 
375 
— 
53 
35 
37 
47 
38 
18 
Red king crab 
367 
145 
49 
55 
60 
38 
21 
1 
Mortality rate (%) 
Snow crab 
1.4% 
— 
20.5% 
30.0% 
43.9% 
75.9% 
88.1% 
100.0% 
Southern Tanner Crab 
7.2% 
— 
32.1% 
51.4% 
86.5% 
91.5% 
92.1% 
100.0% 
Red king crab 
1.9% 
23.4% 
81.6% 
94.5% 
98.3% 
100.0% 
100.0% 
100.0% 
* This category was used only for red king crab. 
