Stevens and Guida: Biological parameters of Chaceon quinquedens in the Mid-Atlantic Bight 
347 
egories for red deepsea crab: 1) new-shell crab were 
relatively soft, clean, and brightly colored, had sharp 
dactyls, and indicated that the crab had molted (prob- 
ably) within the last 1-2 months; 2) hard-shell crab 
had harder shells with some discoloration and scratch- 
es but were still glossy and may have molted within 
the last 6-12 months; 3) old-shell crab had lost their 
glossy, reflective sheen, had numerous dark patch- 
es, scratches, and dull dactyls, and probably had not 
molted for 2 or more years; 4) very-old-shell crab were 
much darker and discolored, indicating these crab had 
not molted for 4-6 years. 
Electronic calipers were used to measure different 
dimensions of the crab. We used CL instead of CW as 
our standard dimension of size, measured from the rear 
margin of the right eyesocket to the rear midline of 
the carapace. Carapace length is a more accurate mea- 
surement because spines are usually included in CW, 
and spines can wear down over time. In addition, we 
redefined the width measurement between spine tips 
as spine width (SW), as opposed to CW, which is often 
measured across the carapace in front of the spines. 
For comparative purposes, we also recorded SW for 
48% and CW for 12% of the measured crab to allow 
for conversions between them. Time constraints pre- 
vented taking all measurements on all crabs, but ad- 
ditional measurements were taken for a subset of the 
sampled crabs that were systematically selected to fill 
out size categories for reproductive studies. Additional 
measurements included chela propodus length (ChL), 
ChH (males only), abdomen width (AW) at the wid- 
est point (females only), and presence and condition of 
eggs (females). 
Haefner (1977) reported that abrasion and discol- 
oration (blackening) around the gonopores (which he 
termed “vulvae”) of female red deepsea crab were indi- 
cations of previous mating, and he demonstrated that 
87% of 67 female red deepsea crab with open, discol- 
ored gonopores contained sperm, whereas none of the 
38 crabs with immature (closed) gonopores contained 
sperm. Therefore, in 2012 and 2013, in our surveys 
maturity of females was estimated on the basis of 
gonopore condition; females with closed and unabraded 
gonopores were classified as immature, whereas those 
with open or discolored gonopores (or external eggs) 
were considered mature. 
Data analysis 
For subsampled tows, the average weight of crab was 
calculated separately for males and females, and the 
proportion of each sex by weight was determined. Total 
catch for each sex (Cggx) was calculated by multiplying 
the total catch weight (Wt) by the weight proportion 
(Pgex) dividing the result by mean weight (MWsex) 
of each sex in the subsample: 
Csex = Wt • Pg,x • MWgex-l • 
Density of crab was calculated as the catch (total 
number) of each sex divided by the area towed and 
expressed as the mean number of crab-per hectare, 
for comparison with results reported by Wahle et al. 
(2008). 
Because replicate tows were not made at each sta- 
tion, density of each sex was compared separately be- 
tween years, sites, and depth strata by using single-fac- 
tor analysis of variance (ANOVA), and P-values <0.05 
were considered significant. If factor effects were signif- 
icant, pairwise comparisons were made with the Bon- 
ferroni correction. Likewise, differences in mean size 
(CL) were compared between sexes, sites, and depth 
strata with a weighted ANOVA, where the sampling 
factors were used as weights to account for unequal 
subsampling. Weighting had little impact on post-hoc 
pairwise comparisons; therefore, post-hoc comparisons 
were unweighted. Proportions of male and female crab 
within 0.5°C categories were also compared by using 
ANOVA and a Kruskal- Wallis test. 
Sex ratios were calculated after summing the catch 
of crab in bins of 5 mm CL. Comparisons were made 
between sites (with depths as replicates) because sites 
were geographically separated. Red deepsea crab may 
make seasonal vertical migrations for reproduction, 
and crab at different depths would comingle; there- 
fore, they were considered to represent a single local 
mating pool. In most brachyuran species, males are 
larger than females, and assortative mating is com- 
mon: females pair with males up to 40% larger, as re- 
ported for snow crab {Chionoecetes opilio; Sainte-Marie 
et al., 1999) and southern Tanner crab (C. bairdi; Ste- 
vens et al., 1993). Male red deepsea crabs in 10 mat- 
ing pairs observed by Wahle et al. (2008) were 50% 
larger than their female partners, and males in 3 mat- 
ing pairs observed in another study were 28% larger 
than their female counterparts (Elner et al., 1987). 
Therefore, in our study, sex ratios were calculated be- 
tween numbers of crab in offset size categories. Given 
that the mean size of females was about 75 mm CL, 
the number of females in each 5-mm bin was com- 
pared with the number of males in bins that were 20 
mm larger (e.g., number of females in the bin of 50-55 
mm CL was compared with that of males in the bin of 
70-75 mm CL). 
Relationships between morphometric characters, 
such as CL, ChL, ChH, and AW were determined for 
selected crabs by using analysis of covariance, with sex 
as a categorical factor. Data were linear and therefore 
were not transformed, but the slopes of the log-trans- 
formed relationships were calculated to determine the 
allometry coefficient. The size at 50% maturity (SM50) 
for females was calculated by using logistic regression 
with maturity (0, 1; determined on the basis of gono- 
pore condition) as the dependent variable, and CL as 
the independent variable. Standard error (SE) of SM50 
was calculated with a bootstrap analysis with 1000 rep- 
etitions. Shell conditions and proportion of mature crab 
with eggs were determined and plotted. All data analy- 
sis was conducted with R, vers. 3.0.2 (R Core Team, 
2013). Most mean values are presented with standard 
deviations (SDs), and a few are noted with SEs. 
