NOTE Kilgour and Shirley: Distribution of Chaceon quinquedens by size and sex in the Gulf of 
319 
Table 1 
Carapace width (mm) and numbers of females and males of red deepsea crab Chaceon quinquedens found on four shipwrecks in 
the Gulf of Mexico. 
Shipwreck 
Depth (m) 
Carapace width (mm) 
Sex 
Average 
Minimum 
Maximum 
Female 
Male 
Gulf Penn 
533 
24.1 
21.2 
31 
0 
4 
Robert E. Lee 
1428 
95.0 
56.5 
141.1 
27 
21 
U-166 
1428 
116.0 
61.5 
136.5 
18 
6 
Alcoa Puritan 
1950 
66.5 
43.7 
120.3 
22 
26 
the largest crabs were found at intermediate depths. 
The four smallest specimens were collected with the 
suction arm of the ROV (all at the Gulf Penn shipwreck) 
and one crab was collected with the manipulator arm 
of the ROV. All other samples were collected in the fish 
traps. No crabs were collected in the minnow traps, and 
crabs were rarely observed on the shipwrecks. Although 
slightly more than half of the crabs were collected close 
to the shipwrecks (74 ±7 m), insufficient data were 
collected to compare wreck effects on crab size or sex 
distribution. 
Males and females did not have significantly different 
distributions. A total of 67 females and 57 males was 
collected (three of unknown sex collected at the U-166 
site) and no depth pattern could be attributed to sex 
(Table 1; P=0.059). 
Discussion 
Previous reports of the distribution of C. quinquedens 
have been contradictory to our findings, which were 
influenced by the addition of a different sampling tech- 
nique, the ROV. Without the ROV, the four smallest 
crabs would not have been observed or collected at the 
shallowest depth. Red deepsea crabs are typically found 
on silt substrate, and although their abundance on the 
shipwrecks was not analyzed in our study, we noted 
that crabs were rarely found on the shipwrecks (see also 
Kilgour, 2007). 
A strong correlation of crab size with depth has been 
reported in some studies of C. quinquedens (Wigley et 
al., 1975; Lockhart et ah, 1990; Lindberg and Lock- 
hart, 1993; Waller et al., 1995; Trigg et al., 1997), but 
not in others (Wenner et ah, 1987). The variation in 
results may have been caused either by a temporal 
variation in sampling, or a sampling bias from gear. 
In our study, the smallest crabs were found at the 
shallowest site and this result was contrary to that 
of previous reports (Lockhart et al., 1990; Lindberg 
and Lockhart, 1993; Waller et al., 1995; Trigg et al., 
1997). A linear relationship between crab size and 
depth was not observed in our study, but this result 
may have been due to the ROV collections which were 
composed of the smallest crabs; crabs of a similar small 
size were not collected with traps at the same site. 
An almost equal ratio of females to males occurred 
in our study and our sampling did not occur during the 
reported mating season (Wigley et al., 1975; Haefner, 
1978; Biesiot and Perry, 1995). Female C. quinquedens 
were found only at the three deepest sites, whereas 
males were found at four of the six sites; this find- 
ing contradicts that of previous studies where depth 
segregation by sex was observed (Wigley et al., 1975; 
Lockhart et al., 1990). Sampling methods to date may 
have been inadequate because the use of traps has been 
the primary method for obtaining information for this 
species. Sampling biases often result in more males 
being collected, particularly when females are oviger- 
ous, because females tend to avoid traps while brooding 
eggs (Howard, 1982; McDonald et al., 2004; Taggart et 
al., 2004). Additionally, sampling bias exists for larger 
males and for smaller males and females; smaller crabs 
are less likely to enter traps when large males are pres- 
ent (Taggart et al., 2004). Chaceon quinquedens is diffi- 
cult to study because of its deep distribution; techniques 
other than trap and trawl sampling may be necessary to 
accurately understand the movements, spatial distribu- 
tion, and life history of this species. 
The bathymetric distribution of many deepwater crab 
species is suspect because the methods by which these 
patterns were determined may be biased. We used two 
different techniques, an ROV and traps; the bathymetric 
distribution of C. quinquedens was different from that 
of previous studies where a single sampling technique 
was used. The best data available are used for fishery 
management, but many times these data represent 
sampling techniques that may not provide a complete 
distribution of the species in question. Our study, in 
spite of a small sample size, demonstrates the impor- 
tance of using more than one technique for observing 
the life history and distribution of a deepwater species 
to reduce the biases of sampling techniques. Both the 
ROV and the trap surveys have sampling biases, but in 
combination, may reveal a more accurate picture of the 
bathymetric distribution of red deepsea crab. The use 
of multiple sampling gears to gain knowledge of the life 
history of deepwater crabs is necessary. 
