Rudershausen et al.: A comparison between circle hook and J hook performance in the troll fisheries off North Carolina 
161 
Table t 
Number of fish caught on circle and J hooks from 39 recreational and 36 charter trips trolling both hook types with natural and 
combination baits offshore of North Carolina, 2006-10. Each number (no.) and percent (%) column is specific to user group (rec- 
reational vs. charter) and hook type (circle vs. J ). Each column of % values adds up to 100%. 
Species 
Recreational 
Charter 
Circle 
J 
Circle 
J 
No. 
% 
No. 
% 
No. 
% 
No. 
% 
Dolphinfish (Coryphaena hippurus) 
35 
63.6 
71 
77.2 
45 
40.2 
73 
38.8 
Yellowfin tuna ( Thunnus alhacares ) 
7 
12.7 
5 
5.4 
25 
22.3 
47 
25.0 
Wahoo ( Acanthocybium solandri ) 
0 
0.0 
1 
1.1 
20 
17.9 
22 
11.7 
Blackfin tuna (Thunnus atlanticus ) 
0 
0.0 
0 
0.0 
14 
12.5 
26 
13.8 
King mackerel ( Scomberomorus cavalla ) 
8 
14.5 
3 
3.3 
0 
0.0 
4 
2.1 
Barracuda (Sphyraena barracuda) 
1 
1.8 
0 
0.0 
1 
0.9 
3 
1.6 
Spanish mackerel ( Scomberomorus maculatus) 
0 
0.0 
3 
3.3 
0 
0.0 
0 
0.0 
False albacore ( Euthynnus alletteratus) 
2 
3.6 
6 
6.5 
4 
3.6 
5 
2.7 
Greater amberjack (Seriola dumerili ) 
0 
0.0 
1 
1.1 
0 
0.0 
1 
0.5 
Bluefish (Pomatomus saltatrix) 
0 
0.0 
1 
1.1 
0 
0.0 
0 
0.0 
Atlantic sailfish ( Istiophorus platypterus) 
1 
1.8 
0 
0.0 
2 
1.8 
4 
2.1 
White marlin (Tetrapturus albidus) 
0 
0.0 
1 
1.1 
0 
0.0 
0 
0.0 
Blue marlin (Makaira nigricans) 
0 
0.0 
0 
0.0 
0 
0.0 
1 
0.5 
Skipjack tuna (Euthynnus pelamis) 
0 
0.0 
0 
0.0 
1 
0.9 
2 
1.1 
Bullet mackerel (Auxis spp.) 
1 
1.8 
0 
0.0 
0 
0.0 
0 
0.0 
Results 
Catch composition 
The three most abundant species captured on recre- 
ational trips were dolphinfish, yellowfin tuna, and 
king mackerel, which together constituted 91% of the 
catch on circle hooks and 86% on J hooks. The three 
most abundant species captured on charter trips were 
dolphinfish, yellowfin tuna, and wahoo, which together 
constituted 80% of the catch on circle hooks and 76% 
on J hooks. Blackfin tuna were commonly caught on 
charter trips, constituting 13% of the catch on circle 
hooks and 14% of the catch on J hooks. Billfishes made 
up 1% of the catch on recreational trips and 3% of the 
catch on charter trips (Table 1). Pooling across both 
user groups, we found that 74% of dolphinfish were 
caught on monofilament leaders, 96% of yellowfin 
tuna were caught on fluorocarbon leaders, and 98% of 
wahoo were caught on wire leaders; that is, the vast 
majority of individuals from each species were cap- 
tured on the respective directed leader type. Species 
identity could not be determined in 14.0% of strike 
and 2.9% of hook-up interactions over the course of 
the study. 
Comparisons of catch and examination 
of mechanisms influencing catch 
Hook type influenced catch rate (Fig. 2). For the three- 
species analysis of catch rate, the base model plus a 
hook main effect received majority support (Table 2). 
For directed leaders, J hooks caught more dolphinfish 
than circle hooks for both recreational and charter 
groups. Higher catches on J hooks were also observed 
in the charter group for yellowfin tuna; however, there 
was no clear hook effect within the recreational group 
for yellowfin tuna or wahoo or charter group for wahoo. 
Partial support for models containing hook-user and 
hook-species interactions confirms these observations 
(Table 2). The hook-leader interaction also had support 
and was most obvious in the dolphinfish data where 
the hook effect was not consistent across leader types 
(Fig. 2). Model fitting to numbers-caught data with 
taxa (i.e., dolphinfish, tunas, and mackerels) provided 
similar results to those for species data (Table 2; Fig. 
3); the base model plus a hook main effect received 
majority support as the best fitting model and models 
that included hook-user, hook-leader, and hook-species 
interactions had QAIC values within four units of the 
best fitting model. Tunas were caught more often on J 
hooks and fluorocarbon leaders than other hook-leader 
combinations. Mackerels were caught slightly more 
often on J hooks than circle hooks, and most often on 
wire leaders (Fig. 3). 
The first mechanism contributing to catch was strike. 
Hook type had little effect on strikes for each of the 
three species examined (Fig. 4). No single model re- 
ceived majority support when fitted to strike data for 
the three species and the base model with a hook factor 
received only slightly greater support than the base 
model without the hook parameter (Table 3). Models 
