Stevens and Guida: Biological parameters of Chaceon quinquedens in the Mid-Atlantic Bight 
355 
Figure 8 
Proportion of female red deepsea crab (Chaceon 
quinquedens) that were mature (as defined by presence 
of eggs or condition of the gonopores) in each size group 
classified in intervals of 5 mm in carapace length [CL] 
(circles) and predicted maturity from logistic regression 
(line). The estimated size at 50% maturity (SM50) was 
61.57 mm CL 
Tanner crab (Paul, 1984), and snow crab (Rondeau 
and Sainte-Marie, 2001). Male southern Tanner crab 
may mate with as many as 10 partners, but usu- 
ally with less than 5 (Paul, 1984). Guarding time 
and the amount of sperm transferred by male snow 
crabs declines with sex ratio because males try to 
conserve sperm and, therefore, may leave 
females with inadequate supplies to fertil- 
ize a clutch of eggs (Rondeau and Sainte- 
Marie, 2001). Blue crab (Callinectes sapi- 
dus) show a marked decline in the rate 
of courtship initiation at sex ratios below 
2 (Jivoff and Hines, 1998). The minimum 
sex ratio for successful fertilization of all 
females in a crab population is unknown, 
but may lie between 0.1 and 0.5; a con- 
servative estimate would be 0.25, indicat- 
ing that most females above the mean size 
in our study do not have access to an ad- 
equate number of males. 
The crab in our study were considerably 
smaller than C. affinis from the Canary 
Islands (mean sizes of males and females 
were 130 and 120 mm CW) (Fernandez-Ver- 
gaz et al., 2000) or the Azores (107 and 91 
mm CL) (Pinho et al., 2001); however, crab 
in the Canaries and Azores were captured 
by traps, which are highly size selective; 
only 3 crab <80 mm CW were caught by 
Fernandez-Vergaz et al. (2000). 
Morphometries 
Sexual maturity in our sample of red deepsea crab can- 
not be inferred from morphometric characteristics. A 
variety of methods have been proposed for determin- 
ing the maturity of crabs. Somerton (1980) described 
a computer technique that determined SM50 for male 
crabs by fitting morphometric data with a logistic re- 
gression. He defined 4 patterns of allometric growth, 
based on the relationship between chela and carapace 
measurements, and applied those relationships to de- 
termine size at sexual maturity for male snow crab 
in the Bering Sea (Somerton, 1981) and later for blue 
king crab (Paralithodes platypus', Somerton and Ma- 
cintosh, 1983). Allometric patterns in species of Chi- 
onoecetes are curvilinear, and variation increases with 
size, but patterns become linear when log-transformed. 
The slope of the log-transformed relationship is defined 
as the allometry coefficient. 
The relationship between ChL and CL for our male 
red deepsea crab was linear, did not show increased 
variance with size, and did not require transformation. 
It has an allometry coefficient of 1.09, indicating iso- 
metric growth and has no inflection point that could 
be used to define the onset of sexual maturity. The 
relationship between ChL and CL for female crabs, 
however, indicated clear sexual dimorphism and was 
negatively allometric. The relationship between male 
ChH and CL was also isometric, with an allometry co- 
efficient of 1.06. Similar to that of males, the relation- 
ship between female AW and CL was linear, had no 
apparent inflexion point corresponding to maturity, and 
did not differ between maturity types. 
Similar results were obtained for C. affinis in the 
Azores; no inflections were found in the relationships 
between CL and CW, ChW (height), or female AW, and 
CO 
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 
Carapace length (mm) 
Figure 9 
Proportion of mature female red deepsea crab (Chaceon quinque- 
dens) with external eggs and captured in the Mid-Atlantic Bight in 
January 2012 and July 2011. Each size group is classified by inter- 
vals of 5 mm in carapace length (CL). Maturity was not recorded 
in 2011. 
