52 
Fishery Bulletin 109(1 ) 
Table 1 
Summary of data documented with crab trap video (CTV), used to observe behavior of male blue crabs ( Callinectes sapidus ) in 
and around crab pots. The observation time, number of approaches, entries, escapes, and captures are shown for each mesocosm 
video trial. These data were used to create the conceptual diagram of crab trap dynamics seen in Figure 3. Kitchen= the kitchen 
section of a crab pot; parlor=the parlor section of a crab pot. 
Date 
Observation 
period (h) 
No. of crab 
approaches 
No. of crab 
entries 
No. of escapes 
(from the kitchen) 
No. of escapes 
(from the parlor) 
No. of crabs 
caught 
07 Aug 03 
17 
232 
58 
51 
2 
4 
12 Aug 03 
25 
146 
8 
5 
0 
3 
14 Aug 03 
23 
158 
22 
17 
1 
5 
15 Aug 03 
16 
113 
37 
29 
0 
8 
16 Aug 03 
23 
179 
43 
37 
0 
6 
Total 
104 
828 
168 
139 
3 
26 
24 hours; and 10% of those that escaped were from 
sublegal-size crabs. There was no sign of cannibalism 
in any of the pots. Neither depth (ANOVA, P>0.05, 
F= 0.92, df=2) nor test crab (ANOVA, P>0.05, F=1.44, 
df=2) had a significant effect on escape rate, nor was 
there a significant size-by-depth interaction on escape 
rate (ANOVA, P>0.05, F=1.97, df=4). 
There was no significant difference between the num- 
ber and size of crabs caught in the first 24 hours and 
the second 24 hours; this finding indicated that in our 
Figure 3 
Conceptual diagram of trap dynamics as observed with a 
crab trap video (CTV) camera system. Percentage values are 
means of data from Table 1. Of the blue crabs ( Callinectes 
sapidus) that approached the pots, 80% avoided them and 
20% entered them. Of the 20% that entered the pots, 85% 
escaped and 15% were caught. Of the 85% that escaped, 98% 
of the escapes occurred for blue crabs that entered the kitchen 
section only and 2% of the escapes were for blue crabs that 
entered the parlor. Overall, pots retained only 3% of all crabs 
that approached and entered the pots; the dashed curve line 
shows the final catch for those crabs that approached the pots. 
experiment, the pot submersion time did not appear to 
affect catch rate (t-test, P>0.05). 
Mesocosm experiment 
For the duration of each deployment, the approaches, 
entries, escapes, and catches of crabs were observed 
(Table 1). These data were then used to develop a 
model of trap dynamics (Fig. 3). In our analysis, the 
number of pots that were approached far exceeded those 
that were entered; only 20% of crab approaches 
resulted in an entry. The cause of pot avoidance 
in nearly 80% of approaches is unknown, but 
was not caused by conspecifics (discussed below). 
An interesting observation was the relative ease 
with which the crabs entered and exited the pots. 
During the duration of the mesocosm experi- 
ments, a total of 168 entries into the pots and 
142 escapes from the pots were observed. The 
85% escape rate in our mesocosm experiment 
consisted of 139 escapes from the kitchen, and 
three escapes from the parlor. The ability of crabs 
to exit the pot is clearly related to the section of 
the pot where the crab is located. Of the total 
escapes, 98% occurred from the kitchen and only 
2% from the parlor. 
A total of 286 intraspecific interactions were 
observed, and during 133 of these, crabs physi- 
cally touched each other. Of all 286 interactions, 
the majority (178) took place in the kitchen, 12 in 
the entrance, 78 in the parlor, and 18 outside the 
pot. Approximately 10% of all observed interac- 
tions were aggressive, 42% were agonistic, and 
48% neutral. Twelve interactions were observed 
at one of the four entrances. Of the 12 interac- 
tions, 1 was aggressive, 4 were agonistic, and 7 
were neutral. In 4 of the 12 entryway interactions 
there was physical contact between crabs; all 4 
of these interactions were agonistic. There were 
no interactions at the pot entrances that affected 
entry or exit of the pot. 
