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lationship, we hypothesized that recently settled Tan- 
ner crabs were preferentially using the habitat created 
by S. sibirica. Juvenile flatfish, principally northern 
rock sole and Pacific halibut (Hippoglossus stenolepis ), 
are also attracted to this type of habitat (Ryer et ah, 
2013). Although fish avoid areas where worms were so 
dense as to preclude burial, fish aggregate along the 
sparse and patchy edges of this habitat type (Ryer et 
ah, 2013). In 2010, when both worm tubes and crabs 
were relatively abundant, there was a significant posi- 
tive effect of worm abundance on crab density, after the 
effect of depth was factored out. However, during 2011, 
when both worms and crabs were less abundant, worm 
abundance had no effect on crab density. This differ- 
ence in effects indicates that the habitat created by S. 
sibirica tubes has only a modest influence on distribu- 
tion of age-0 Tanner crabs. 
In a manner analogous to the refuge function of eel- 
grass (Zostera marina L.) (Wilson et ah, 1987; Ryer, 
1988), the physical structure of the worm tube habitat 
may provide age-0 Tanner crabs refuge from fish preda- 
tors. Predation by Pacific cod ( Gadus macrocephalus ) 
is thought to regulate Tanner crab recruitment in the 
Gulf of Alaska and Bering Sea (Livingston, 1989). Ju- 
venile Tanner crabs may also consume S. sibirica di- 
rectly or the associated invertebrate species supported 
by the worm tube habitat (senior author, personal ob- 
serv.). Alternatively, both species may be attracted to 
the same depth and sediment characteristics, possibly 
explaining their association. This interpretation is sup- 
ported by results from our quadrat surveys, which were 
conducted by divers at a finer scale than that of the 
scrape tows and which indicated there was no rela- 
tionship between crab density and worm tube density. 
Resolving the nature of this association could be ad- 
dressed though controlled laboratory experimentation 
that might reveal whether age-0 Tanner crabs show 
an attraction for the structure provided by S. sibirica 
and whether an association reduces predation on age-0 
Tanner crabs. 
Growth in crustaceans is a function of molt incre- 
ments, typically expressed as percent increase in size, 
and a function of the frequency with which those molts 
occur. Knowledge of the age distribution of a popula- 
tion can be important information in stock assessment. 
In practice, aging commercially harvested North Pa- 
cific crabs species relies upon imprecise estimates of 
the number of molts that occur during each year. Our 
data indicate that age-0 Tanner crab, around Kodiak 
Island, pass through between 3 and 5 molts from settle- 
ment through August. By May of the next year, crabs 
have gone through 6 or more molt stages. Although no 
other studies have documented growth during the first 
year for this species, Donaldson et al. (1981) reported 
a strong size mode at 18 mm (C6 instars) during May- 
June in Prince William Sound, northern Gulf of Alaska. 
Therefore, it appears that crabs in the northern Gulf 
of Alaska, including near Kodiak, typically go through 
roughly 6 molt stages in their first year. On the basis 
of various samples from areas in the Gulf of Alaska, 
these authors concluded that Tanner crabs typically un- 
dergo 3 more molts in their second year and 2 molts in 
their third year, after which molting occurs annually. 
Donaldson et al. (1981) found that 50% of females were 
mature at 83 mm and 50% males were mature at 90 
mm, indicating that age at maturity for this species is 
approximately 5 years for females and 7 years for males. 
Variance in this age-growth schedule will result 
from differential growth rates between localities and 
years. Temperature plays an important role in modu- 
lating growth in crustaceans (Hartnoll, 1982). After 60 
days, red king crab and blue king crab reared at 1.5°C 
were mostly still Cl instars, whereas those reared at 
8°C for 60 days were mostly C3 instars (Stoner et al., 
2010, 2013). This finding indicates that crabs settling 
into habitats with differing ambient temperatures may 
experience vastly different growth rates. Using pub- 
lished, temperature-dependent growth rates, Stevens 
(1990) estimated growth and years to maturity for red 
king crabs from areas with varying temperature re- 
gimes in Bristol Bay, Alaska. He concluded that growth 
varies greatly between areas, such that crabs recruit- 
ing to the pot fishery in the eastern Bering Sea in any 
given year may be derived from up to 4 or 5 year class- 
es. This conclusion indicates that it would be advanta- 
geous for Tanner megalopae to preferentially settle in 
shallower water where temperatures are supportive of 
accelerated growth. Naturally, such an outcome would 
require that other factors, such as forage base and pre- 
dation risk, do not compromise the enhanced growth 
for crabs settling in shallower water. 
Data from out study indicate that growth rates dif- 
fer among sites. During both 2010 and 2011, crabs from 
Womens were generally 1 molt stage larger by the end 
of August than crabs from Pillar and Holiday. There 
are several possible explanations for this observed size 
difference. Crabs may simply recruit earlier at Womens 
than at the other sites. However, this notion is not con- 
sistent with results from our May 2011 sampling which 
indicated that crabs at Womens may actually have re- 
cruited slightly later. Temperature may play a role. We 
did document minor differences in mean ambient bot- 
tom temperature (at a depth of 15 m MLLW) between 
sites; temperature was greatest at Womens. However, 
the difference in mean temperature between sites was 
only 0.5°C, and we are skeptical that this difference 
would result in the greater size observed for crabs at 
Womens. Age-0 Tanner crabs molt approximately once 
every 873 degree days in the laboratory, and a temper- 
ature shift of 0.5°C would only marginally increase the 
frequency of molting (Long et al., 2013b). Furthermore, 
temperature was lowest at Kalsin, yet crabs at Kalsin 
were closest in size to those at Womens and generally 
were larger than those at Pillar and Holiday. It is per- 
haps more important to note that bottom temperature 
at 15 m may not be representative of temperatures for 
an entire embayment. For example, at both Womens 
and Kalsin where high growth was seen, crabs tended 
to be found at shallower depths, where temperatures 
are expected to be higher. 
