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Fishery Bulletin 113(3) 
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2010 
201 1-2012 
Month and year 
Figure 3 
Timed depth (black line) and temperature (gray line) recordings from a data 
storage tag attached to a 100-mm (carapace width) morphometrically mature 
male snow crab (Chionoecetes opilio ) released in the eastern Bering Sea in 2010. 
This crab was at liberty for 640 days, although the depth sensor ceased to func- 
tion approximately 5 months before its recapture. 
downslope movements (depth changes <10 m), remain- 
ing in depths >120 m; and 3) initial downslope move- 
ments of more than 20 m followed by extensive upslope 
movements, remaining in depths >120 m (Fig. 2A). For 
crabs released in 2011 (north of 2010 releases), all 9 
of the males that were recovered moved upslope im- 
mediately after release in the spring, but their depth 
changes were less extensive than those of tagged males 
released in 2010 (Fig. 2B), with changes ranging from 7 
to 16 m (mean: 10.5 m). Of the 5 males that were still 
at liberty during the following spring, in 2012, only 1 
appeared to move upslope during the second spring. 
Two of the 4 small tagged males (100-102 mm CW) 
undertook relatively long inshore migrations of -100 
km, in depths ranging from 120 to 90 m (Fig. 1) during 
the spring and summer followed by an offshore migra- 
tion during fall and winter. They did not migrate to- 
gether because the timing of their inshore and offshore 
movements was offset by about 1 month (Fig. 2A). A 
third small individual (100 mm CW), released in 2010 
and at liberty 640 days, undertook inshore and offshore 
migrations in both 2010 and 2011, but it did so dur- 
ing different months and to differing extents (Fig. 3). 
During successive spring periods, it resided at different 
depths (by approximately 20 m) and different locations 
(separated by a distance of approximately 50 km), in- 
dicating that individuals can undergo variable migra- 
tions from year to year. The fourth small male ( 100 mm 
CW), released in 2011, migrated inshore but not to the 
extent of the other 3 small tagged male snow crabs. 
Temperatures encountered 
Temperatures encountered by the tagged males ranged 
from -0.5°C to 4.5°C (Fig. 4, A and B), although those 
males that were released at the 
more northern location in 2011 
(n= 9) experienced temperatures 
about 1°C colder (mean: 2.3°C) 
than the temperatures experi- 
enced by males (n= 24) released 
farther south in 2010 (mean: 
3.3°C). Seasonally, tagged males 
encountered the warmest tem- 
peratures during winter (~No- 
vember-January) and the cold- 
est temperatures during spring 
(~February-June). Annual dif- 
ferences in ambient temperature 
were apparent from DST data ob- 
tained from 2011 released males 
that were at liberty for more 
than 14 months (Fig. 4B); spring 
temperatures averaged 2.3°C 
in 2011 compared with 1.3°C in 
2012. The coldest temperatures 
(<1°C) were encountered by the 
2 males that, in 2010, migrated 
farthest inshore to a depth of 90 
m (Fig. 4A), where, on the basis 
of the spatial distribution of bottom temperatures of 
the eastern Bering Sea shelf measured during the sum- 
mer bottom trawl survey (Lauth, 2011), each of them 
migrated to the edge of the cold pool before initiating 
a return offshore migration. Both crabs remained at 
these colder temperatures for approximately 1 month 
before migrating offshore. 
Proximity of mature females to tagged males 
On the basis of the 2010, 2011, and 2012 data of the 
summer distributions of mature females, multiparous 
females were in close proximity (< 10 km) to the loca- 
tions where tagged males were released (Fig. 5, B, D, 
and F). In addition, the inshore migrations of tagged 
males during spring (Fig. 2) indicated that there was a 
broad overlap with multiparous females at the time of 
multiparous mating (March-April). The increase in the 
abundance of multiparous females in the vicinity of the 
tag release areas from 2010 to 2011 indicates that more 
females were available to tagged males for breeding in 
2011 than in 2010. In contrast, primiparous females 
were found much farther east (by distances >50 km) of 
the tagged males during all 3 years (Fig. 5, A, C, and E). 
Bathymetric overlap of tagged males and mature females 
The extent of cross-shelf inshore migrations by tagged 
males, defined here as the minimum depth reached dur- 
ing their time at liberty, increased (e.g., decreasing min- 
imum depth) with decreasing crab size (Fig. 6; linear 
regression: n- 33, coefficient of determination [r 2 ]=0.39, 
P<0.001). Considering the depths where multiparous 
females were found during the NMFS summer bottom 
trawl surveys (Fig. 5), all tagged males occupied ar- 
