44 
Fishery Bulletin 106(1) 
D 4 
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/ 
/ / * “v' "* 
90 110 130 150 170 190 210 90 110 130 150 170 190 210 
Carapace length (mm) 
Figure 5 
Size distribution of red king crabs ( Paralithodes camtschaticus) caught in the 
comparative fishing experiment. The four panels give the size distribution of (A) 
male crabs in square pots; (B) male crabs in conical square pots, (C) female crabs 
in square pots, and (D) female crabs in conical pots. The x-axis is divided by size 
intervals of 10-mm carapace length. Note that the minimum commercial landing 
size of male crabs is 160 mm, marked with a vertical dashed line. 
presumably due to low entry 
rates. RKC and other species 
of crabs have been shown to 
restrict their horizontal search 
movement to the area suffused 
by the odor plume from the 
bait (Miller, 1980; Zhou and 
Shirley, 1997c; Archdale et 
al., 2003). However, the dif- 
ferences in the probability of 
crabs finding their way into the 
two pots is not explained by the 
size of the horizontal entrance 
sector (area available for entry) 
because the less efficient coni- 
cal pots had an entrance sector 
of 360°, whereas only half of 
the perimeter of square pots 
led to a funnel opening. Verti- 
cal search behavior of chemi- 
cally stimulated RKC has also 
been observed to be limited to 
the extent of the odor plume 
(Stiansen, 2004). In the square 
pot, the bait and funnel were 
at the same vertical height, 
whereas the entrance of the 
conical pot was located above 
the plume. Crabs were seldom 
observed to search for the 
source of the odor outside the 
odor plume (Miller, 1978; Vien- 
neau, 1993; Stiansen, 2004), which they have to do to 
locate the entrance of conical pots. 
Although the catches in the conical pots continued 
to increase beyond two days of soak time, the catch 
appeared to stabilize in the square pots, indicating 
that the two pot types were at different phases of the 
catch cycle even after two days of soak time. An ap- 
proximately linear increase in catches with time in the 
conical pots indicates that the ratio of entries to exits 
was relatively constant throughout the period of obser- 
vation. The vertical plastic funnel used in the conical 
pots effectively prevents crabs from escaping (Miller, 
Table 2 
Catch data from the comparative fishing experiment with square and conical red king crab (Paralithodes camtschaticus) 
pots. Median and mean percentages of female red king crabs in catches taken by square and conical pots at different soak 
times are shown. Calculations were made on a string basis, i.e., the pooled catch from the two pots of the same type within a 
string was used as a single observation. The hypothesis of no difference in percentage of females in square and conical pots 
was tested by a Wilcoxon paired comparisons test. Only string settings with catch in both types of pots were used in the test. 
N is the number of strings with nonzero catches, SE is the standard error, and N b is number of strings with catch in both 
types of pot. 
Percentages of female crabs caught Statistical test 
Square pots Conical pots Paired comparisons 
Soak time 
(days) 
N 
Median 
Mean 
SE 
N 
Median 
Mean 
SE 
P value 
2 
57 
53.4 
51.0 
2.17 
52 
66.7 
63.8 
2.46 
51 
<0.001 
3 
29 
56.5 
52.0 
4.21 
27 
71.0 
66.4 
3.76 
26 
<0.005 
4-5 
8 
65.9 
58.2 
8.31 
8 
69.8 
63.3 
6.82 
8 
<0.05 
7-8 
13 
62.9 
62.2 
2.82 
13 
65.3 
67.0 
4.30 
13 
>0.5 
