214 
Fishery Bulletin 99(1 ) 
Table 1 
Summary of pelagic longline catch by species and gangion type for sets 1 through 10. Chi-square statistics (% 2 ) and corresponding 
B-values are presented for comparisons of catch by gangion type for species where total catch exceeded 10 individual per set. M = 
monofilament gangion; B = multifilament gangion. 
Species caught 
Set 1 
Set 2 
Set 3 
Set 4 
Set 5 
M 
B 
X 2 
P 
M 
B 
X 2 
P 
M 
B 
X 2 
P 
M 
B 
X 2 
P 
M 
B 
X 2 
P 
Swordfish 
22 
6 
9.14 
0.003 
31 
26 
0.44 
0.508 
23 
9 
6.13 
0.013 
27 
14 
4.122 
0.042 
44 
23 
6.58 
0.010 
Yellowfin tuna 
0 
0 
— 
— 
0 
0 
— 
— 
1 
0 
— 
— 
0 
0 
— 
— 
2 
0 
— 
— 
Mako shark 
5 
1 
— 
— 
7 
7 
0.00 
1.000 
11 
6 
1.47 
0.225 
5 
5 
0.000 
1.000 
11 
5 
2.25 
0.134 
Blue shark 
9 
3 
3.00 
0.083 
10 
7 
0.53 
0.467 
39 
19 
6.90 
0.009 
12 
5 
2.882 
0.090 
9 
6 
0.60 
0.439 
White marlin 
4 
1 
— 
— 
8 
1 
— 
— 
4 
0 
— 
— 
7 
3 
1.600 
0.206 
5 
2 
— 
— 
Dolphinfish 
2 
0 
— 
— 
4 
3 
— 
— 
2 
0 
— 
— 
6 
1 
— 
— 
1 
2 
— 
— 
Stingray 
13 
4 
4.77 
0.029 
7 
9 
0.25 
0.617 
3 
3 
— 
— 
7 
1 
— 
— 
4 
1 
— 
— 
Loggerhead 
turtle 
3 
4 
— 
— 
4 
0 
— 
— 
6 
4 
0.40 
0.527 
3 
1 
— 
— 
4 
0 
— 
— 
Total 
58 
19 
39.00 
0.000 
71 
53 
18.00 
0.106 
89 
41 
48.00 
0.000 
68 
30 
38.0 
0.000 
80 
39 
41.00 
0.000 
Set 6 
Set 7 
Set 8 
Set 9 
Set 10 
Species caught 
M 
B 
X 2 
p 
M 
B 
X 2 
P 
M 
B 
X 2 
P 
M 
B 
X 2 
p 
M 
B 
X 2 
p 
Swordfish 
31 
12 
8.40 
0.004 
19 
8 
4.48 
0.034 
11 
4 
3.27 
0.071 
27 
14 
4.122 
0.042 
25 
12 
4.57 
0.033 
Yellowfin tuna 
0 
0 
— 
— 
1 
1 
— 
— 
1 
0 
— 
— 
2 
0 
— 
— 
2 
0 
— 
— 
Mako shark 
3 
3 
— 
— 
6 
2 
— 
— 
7 
4 
0.82 
0.366 
1 
4 
— 
— 
2 
2 
— 
— 
Blue shark 
30 
20 
2.00 
0.157 
51 
26 
8.12 
0.004 
47 
19 
11.88 
0.001 
13 
5 
3.556 
0.059 
5 
6 
0.09 
0.763 
White marlin 
1 
1 
— 
— 
5 
0 
— 
— 
1 
0 
— 
— 
7 
3 
1.600 
0.206 
5 
2 
— 
— 
Dolphinfish 
2 
1 
— 
— 
2 
0 
— 
— 
0 
0 
— 
— 
3 
2 
— 
— 
5 
1 
— 
— 
Stingray 
11 
1 
8.33 
0.004 
12 
4 
4.00 
0.046 
1 
0 
— 
— 
1 
4 
— 
— 
4 
4 
— 
— 
Loggerhead 
Turtle 
4 
4 
— 
— 
5 
2 
- 
— 
2 
2 
— 
— 
5 
6 
0.091 
0.763 
4 
3 
— 
— 
Total 
83 
42 
41.00 
0.000 
101 
43 
58.00 
0.000 
70 
29 
41.00 
0.000 
59 
38 
21.00 
0.033 
52 
30 
22.00 
0.015 
some sets. Although only the upper half of the multifil- 
ament gangion was made from braided nylon material 
(based on a configuration used by fishermen in the past), 
the differences in catches for these two species between 
this gangion and one constructed entirely of monofilament 
nylon were striking. A similar trend for the other pelagic 
species was not as evident on a set-by-set basis owing to 
lower catches; however, for combined sets, more captures 
occurred on the monofilament gear overall. Although these 
results clearly indicate differences in catches between gan- 
gion types, the influence of oceanographic conditions off 
Georges Bank, such as water temperature and thermo- 
cline depth, likely influence the availability and catchabil- 
ity of all species. Therefore, it is important to point out 
that results could differ among geographic areas with dif- 
ferent oceanographic regimes. 
Reports of higher catches on monofilament gear have al- 
so been made for other species. Monofilament snoods (gan- 
gions) give higher catch rates for cod and haddock com- 
pared with multifilament snoods, and thinner snoods tend 
to give better catch rates than thicker ones (Bjordal and 
Lokkeborg, 1996). Under good light conditions, monofila- 
ment lines were observed to catch as much as three times 
more cod than multifilament lines (Bjordal and Lokke- 
borg, 1996). Over the past decade, Canadian bluefin tuna 
fishermen have gradually shifted to finer gauges of mono- 
filament nylon line (i.e. from 400 lb to 120 lb test) for 
use on rod and reel gear because it is their perception 
that bluefin tuna have learned to recognize and avoid the 
heavier monofilament nylon line. The lower visibility of 
monofilament gangions used on longline gear is common- 
ly used to explain why they give better catches than gan- 
gions made of multifilament nylon; however, the reason for 
the difference in catching power is unclear. Some pelagic 
fish species may be able to detect multifilament nylon gan- 
gions more readily because of their thicker diameter (5 
mm versus 2 mm for monofilament) and darker color, and 
can make this distinction even during periods of darkness 
(i.e. when the pelagic longline gear is fishing). The higher 
visibility of multifilament lines may cause a restrained re- 
sponse towards attacking the baited hooks. 
Whether multifilament nylon gangions are more easily 
detected by some species, likely depends on the role that 
vision plays as the dominant sensory mechanism. Some 
pelagic species have large eyes (i.e. yellowfin tuna, sword- 
fish, white marlin, mako and blue shark) and are efficient 
visual predators even in dim light. Becuase visual acuity 
or resolution of detail improves with the size of the eye 
(Blaxter, 1980), some pelagic species may be better at de- 
tecting and avoiding the multifilament nylon gangions 
