NOTE Stone and Dixon: A comparison of catches of Xiphias gladius and other pelagic species with longline gear 
215 
Table 2 
Summary of pelagic longline catches by species and gangion type for all sets combined. Chi-square statistics ( x 2 ) and corresponding 
P-values are presented for all species. M = monofilament gangion; B = multifilament gangion. 
Species 
Gangion 
n 
% by gangion type 
Ratio (M:B) 
X 2 
P 
% of total catch 
Swordfish 
M 
260 
67.0 
2.03:1.00 
44.90 
0.000 
35.7 
B 
128 
33.0 
35.2 
Yellowfin tuna 
M 
9 
90.0 
9.00:1.00 
6.40 
0.011 
1.2 
B 
1 
10.0 
0.3 
Mako shark 
M 
58 
59.8 
1.49:1.00 
3.72 
0.054 
7.8 
B 
39 
40.2 
10.7 
Blue shark 
M 
225 
66.0 
1.94:1.00 
34.84 
0.000 
30.9 
B 
116 
34.0 
31.9 
White marlin 
M 
47 
78.3 
3.62:1.00 
19.27 
0.000 
6.5 
B 
13 
21.7 
3.6 
Dolphinfish 
M 
27 
73.0 
2.70:1.00 
7.81 
0.005 
3.7 
B 
10 
2.8 
Stingray 
M 
63 
67.0 
2.03:1.00 
10.89 
0.001 
8.6 
B 
31 
33.0 
8.5 
Loggerhead turtle 
M 
40 
60.6 
1.54:1.00 
2.97 
0.085 
5.5 
B 
26 
39.4 
7.1 
Total 
M 
729 
66.7 
2.00:1.00 
123.00 
0.000 
100.0 
B 
364 
33.3 
100.0 
than others, as evidenced by the range of catch ratios be- 
tween monofilament and multifilament gangions for the 
various species encountered during our study (Table 2). 
Although no differences in the size of swordfish >119 
cm LJFL occurred between gangion types, more swordfish 
were captured on monofilament gangions, along with oth- 
er bycatch species. Although catches of all species were 
higher on the monofilament gear, the percentage of total 
catch represented by each species for each gear type was 
very similar (Table 2, last column). Therefore, by fishing 
an extra one or two sets with the multifilament gear, fish- 
ermen would get the same amount of catch as they would 
have if monofilament gear were used, but at greater cost 
because more sets and days at sea would be required to 
yield the same catch. Furthermore, the absence of any spe- 
cies-specific trends between gangion types indicates that 
the use of monofilament gangions does not reduce the by- 
catch of other pelagic species. 
Catch-per-unit-of-effort (CPUE) indices based on com- 
mercial fishery statistics are often used in analytical mod- 
els to investigate trends in resource abundance, particu- 
larly in the stock assessments for swordfish and bluefin 
tuna conducted by the International Commission for the 
Conservation of Atlantic Tunas. Catch rates are generally 
standardized for the effects of gear, area, month, and oth- 
er factors by using general linear models (e.g. Hoey et al. 
1997). The importance of gear changes and their effect on 
commercial catch rates is clearly evident in this study and 
underscores the need to detect and account for changes 
in gear technology in the development of any commercial 
catch rate series used in analytical stock assessments. 
Acknowledgments 
The expertise and assistance of the crew of the Nova Blue 
are greatly appreciated, for without their help this study 
would not have been possible. We also thank R. Halliday, 
J. Neilson, J. Hoey, and J. Porter for their many useful com- 
ments on an earlier draft of this manuscript. We also thank 
the Canadian Department of Fisheries and Oceans for per- 
mitting the experiment to be conducted in a closed area. 
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