Nichol and Somerton: Seasonal migration of mature males of Chionoecetes opilio in the eastern Bering Sea 
317 
tion. Distributions were plotted as described 
previously for the size classes of 70-100 mm 
CW and >100 mm CW by using the data 
pooled across 1989-2011 and by using cal- 
culated relative proportions at each station. 
mean N; during years when sampling occurred. Alge- 
braically, this mean is expressed as 
v.. AT. 
N . = hl£LL t ( 3 ) 
»i 
where n; = the number of years in which CHs were 
measured at station i. 
Distribution of adolescent males 
Adolescent males were also identified as above with 
the CH-CW regression provided in the previous sec- 
Results 
Time at liberty and recapture locations 
A total of 33 male snow crabs with DSTs 
were recaptured, of which 4 individuals 
were 100-102 mm CW and the rest ranged 
in size from 106 to 126 mm CW. In addi- 
tion, 43 males with only spaghetti tags (not 
DSTs) were recaptured with sizes ranging 
from 101 to 130 mm CW (Fig. 1). 
Among males tagged with DSTs in 2010, 
22 were recaptured in 2011 after 280-333 
days at liberty and 1 was recaptured in 2012 
after 640 days at liberty. Of the males re- 
leased in 2011 with DSTs, 9 were recaptured 
in 2012 after 439-458 days at liberty. Among 
males tagged with spaghetti tags in 2010, 42 
were at liberty between 274 and 319 days 
before recapture, and 1 other male was re- 
captured after 777 days. Recapture rates for 
snow crabs released in 2010 (and recaptured 
in 2011) were 18.3% (n= 22) for those tagged 
with DSTs and 19.0% (n=42) for those tagged 
only with spaghetti tags, indicating essential- 
ly no difference in recapture rates between 
the 2 tag types. The attachment of the DSTs 
to spaghetti tags, therefore, was assumed to 
have no added effect on crab behavior or sur- 
vival. Compared with males tagged in 2010, 
those males tagged in 2011 were recaptured 
later in the year (May-June, in 2012) and at 
a lower rate (5.7%; n= 9), owing to ice condi- 
tions that limited access to the fishing area 
during winter and caused the fishing season 
to be extended (Gutierrez, 2012). Recapture 
locations of both types of tags indicate some 
site fidelity, as indicated by the low degree 
of area overlap between crabs recaptured in 
2011 and 2012 and released approximately 
100 km apart (Fig. 1). 
Occurrence and extent of inshore-offshore migrations 
Individual depth trajectories among tagged males were 
highly variable within the depth range they inhabited 
(90-172 m), indicating a wide variety of individual 
migration routes (Fig. 2, A and B). For the crabs re- 
leased in 2010, 3 general movement patterns were ob- 
served: 1) extensive upslope (i.e., inshore) movements, 
or changes in depth, >20 m to depths <120 m with- 
in 1 month after tagging; 2) very limited upslope or 
