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Fishery Bulletin 114(3) 
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250-450m 450-700m 700-850m 250-450m 450-700m 700-850m 
Depth strata 
Figure 6 
Proportion of (A) male and (B) female red deepsea crab (Cha- 
ceon quinquedens) in each of 4 categories of shell condition at 
3 depth strata sampled in the Mid- Atlantic Bight during 2011— 
2013 (years and sites combined). Shell conditions are new (light 
gray), hard (medium gray), old (dark gray), and very old (black). 
mm SW) have been previously noted (McRae, 1961; 
Haefner, 1978; Weinberg and Keith, 2003). According 
to McRae (1961), mean weights for a “random sam- 
ple” of crabs were 794 g for males, and 
312 g for non-ovigerous females, equiva- 
lent to sizes of 116.4 mm CL and 88.4 
mm CL, respectively, or 144.2 and 110.2 
mm SW (converted with the equation 
for CW from Weinberg and Keith, 2003). 
The source of this sample was not de- 
scribed, but presumably it was near 
our sampling area. Therefore, either 
mean size of red deepsea crab has de- 
clined significantly since McRae’s study 
in 1960, or his random sample was bi- 
ased toward large crab. The mean size 
of male crab reported by McRae (1961) 
was 31% larger than the mean size of 
females. This difference is similar to the 
mean size differential of 27.9% report- 
ed by Elner et al. (1987) for 3 pairs of 
crab (involving 2 males and 2 females) 
observed mating in captivity, but it is 
smaller than the differential of 50% 
between 10 mating pairs observed by 
Wahle et al. (2008) during tows with 
video cameras. Although sample sizes 
for the latter 2 studies were small, they 
indicate that the relative size of male 
and female crabs observed by McRae 
(1961) offered adequate opportunities 
for mating. 
Sex ratios are commonly used to deter- 
mine whether fishing has affected a crab 
population, but they are usually calculated 
over large geographic areas. However, function- 
al maturity (i.e., the ability of male crabs to 
mate in competitive, natural environments) is 
dependent on both size (Paul, 1984) and shell 
condition (Stevens, et al., 1993) because harder 
shells are necessary to grasp females and de- 
fend them from other males. As a result, the 
effective sex ratio of mating-capable partners 
may vary greatly over small geographic areas. 
For this reason we calculated effective sex ra- 
tio only within sampling sites, where the sam- 
ples were geographically close, and these ratios 
were calculated between abundance of females 
in 5-mm-CL bins and abundance of males that 
were 20 mm CL larger. We also ignored shell 
condition and depth because both could change 
between the time sampled and mating season, 
and we did not include year effects in order to 
preserve adequate sample sizes. 
Sex ratios were generally biased toward 
males in the smaller size intervals, but for 
intervals larger than the SM50 for female red 
deepsea crab, all ratios were <0.7, and many 
ratios were much lower. These data indicate 
that male mating partners for females be- 
come exceedingly scarce as females grow. Mating of 
male crab with multiple females has been observed 
for red deepsea crab (Elner, et al., 1987), southern 
(M 
X 
0 ) 
CO 
75.55 80.60 85.65 90.70 95.75 100.80 105.85 110.90 115.95 120.100 
Minimum size (mm CL) of pairs (M,F) 
Figure 7 
Sex ratio (M:F) of red deepsea crab (Chaceon quinquedens) at each 
of 4 sites sampled in the Mid-Atlantic Bight during 2011-2013, com- 
pared by offset 5-mm categories, for pairs in which the minimum size 
of males is 20 mm in carapace length (CL) greater than the minimum 
size of females. Missing bars indicate either a lack of males or females 
in one category. The 4 sites were Block Island Canyon (BIC), Hudson 
Canyon (Hud), Baltimore and Washington Canyons (BWC), and Nor- 
folk Canyon (Nor) 
