Ryer et at: Depth distribution, habitat associations, and differential growth of Chionoecetes bairdi 
261 
ference varied somewhat between months (sitexmonth: 
Wald *2=12.9, df=3, P=0.005). 
We conducted limited beam trawl sampling at Pillar 
during July and August, including depths beyond those 
attempted with the scrape (Fig. 2C). The depth distri- 
bution of crabs differed between July and August (Wald 
* 2 =17.1, df=6, P=0.009). During July, crab density in- 
creased from the shallows to a peak at 25-35 m, declin- 
ing farther offshore. By August, crab density was more 
uniform across depths as overall density decreased. 
Worms tubes, principally those of S. sibirica, were 
generally more abundant at Pillar than at Holiday 
(Fig. 3A). At both sites, tubes were rare in the shallows 
but increased in abundance with depth. Therefore, the 
depth distribution of age-0 Tanner crabs mirrored the 
distribution of worm tubes. Abundance of worm tubes 
had a significant positive influence on crab density 
(Wald * 2 =233.1, df=l, P<0.001). To graphically dem- 
onstrate this association, we performed a second GLM 
analysis, leaving out the worm covariate, and plotted 
the residuals against the worm index (Fig. 3B). 
Crab densities were lower in 2011 than in 2010. 
With the addition of Womens and Kalsin sites in 2011, 
differences between study sites also became more evi- 
dent (Fig. 4, A-D). Beyond the obvious difference in 
the overall abundance of crabs, perhaps most notice- 
able was the influence of site on depth distribution 
(Wald * 2 =56.0, df=8, P<0.001). As in 2010, crab den- 
sity at Holiday and Pillar consistently was highest at 
the greatest depth. In contrast, at Womens and Kalsin, 
crabs were found at shallower depths and more evenly 
distributed among depths. There was also an interac- 
tive effect wherein depth distribution differed among 
months (depthxmonth: Wald * 2 =17.4, df=9, P=0.043). 
This effect was manifest as a “flattening” of the depth 
distribution curves, particularly during August at Holi- 
day and Pillar — an effect similar to that observed dur- 
ing 2010. 
Seasonal, or month to month, changes in crab den- 
sity also differed among sites (month X site: Wald 
* 2 =27.4, df=9, P=0.001). Most notable were changes 
in crab density subsequent to the end of settlement 
in July. Post-hoc comparisons indicated that mean 
crab density (crabs/m 2 ) declined from July to August 
at Holiday (July: 0.61 [standard error (SE) 0.18]; Au- 
gust: 0.26 [SE 0.09]; Wald * 2 =59.0, df=3, PcO.001), as 
well as at Pillar (July: 0.66 [SE 0.25]; August: 0.15 [SE 
0.07]; Wald * 2 =62.4, df=3, P<0.001) and Kalsin (July: 
0.34 [SE 0.07]; August: 0.20 [SE 0.05]; Wald * 2 =12.8, 
df=3, P=0.005). In contrast, there was no decline in 
crab density from July to August at Womens (July: 0.11 
[SE 0.02]; August: 0.12 [SE 0.02]; Wald * 2 =4.6, df=l, 
P=0.201). There was no significant 3-way interactive 
effect of site, month, and depth on crab density (Wald 
* 2 =25.4, df=18, P=0.115). 
Results from beam trawl sampling (Fig. 5) indicate 
that, unlike in July 2010 when crabs were most dense 
at intermediate depths (25-35 m), crab density during 
2011 was highest in the deepest tows (Wald * 2 =17.0, 
df=4, P=0.002). Although crab density decreased from 
