172 
Fishery Bulletin 1 10(2) 
Table 5 
Candidate models fitted to retention data for three species (dolphinfish [ Coryphaena hippurus j, yellowfin tuna [Thunnus alba- 
cares], and wahoo \Acanthocybium solandri]), and taxa (dolphinfish, tunas, and mackerels) when trolling circle and J hooks in 
Gulf Stream waters off North Carolina. Quasi-Akaike information criterion (QAIC) was used to evaluate model performance, with 
the lowest value indicating the most parsimonious model. Categorical predictor variables included hook type (hook), leader type 
( leader), species or taxa, and user group ( user). Wave height was used as a continuous predictor variable. K= number of parameters 
for each model; m=Akaike weight. Base models included all predictor variables with exception of hook and any hook interactions; 
see Methods section for a full description of base models. AQAIC values ~<4 were considered models with reasonable support. 
Interaction Datatype Distribution Model 
K 
QAIC 
AQAIC 
w 
Retention: Proportion Binomial base 
10 
-876.22 
0.00 
0.63 
species base + hook 
11 
-874.19 
2.02 
0.23 
base + hook + hook*leader 
13 
-871.13 
5.09 
0.05 
base + hook + hook*species 
13 
-870.76 
5.46 
0.04 
base + hook + hook*species + hook*user 
14 
-869.35 
6.87 
0.02 
base + hook + hook*user + hook*leader 
14 
-869.16 
7.05 
0.02 
base + hook + hook*species + hook*leader 
15 
-867.10 
9.12 
0.01 
base + hook + hook*user 
12 
-857.77 
18.45 
0.00 
base + hook + hook*species + hook*leader 
23 
-854.71 
21.51 
0.00 
+ species + leader hook*species*leader 
Retention: Proportion Binomial base 
12 
-1112.66 
0.00 
0.53 
Taxa base + hook 
13 
-1110.55 
2.11 
0.19 
base + hook + hook*species 
15 
-1108.74 
3.92 
0.08 
base + hook + hook*user 
14 
-1108.74 
3.93 
0.08 
base + hook + hook*leader 
15 
-1108.54 
4.12 
0.07 
base + hook + hook*species + hook*user 
16 
-1106.71 
5.95 
0.03 
base + hook + hook*user + hook*leader 
16 
-1106.40 
6.26 
0.02 
base + hook + hook*species + hook*leader 
17 
-1104.87 
7.79 
0.01 
base + hook + hook*species + hook*leader 
23 
-1092.10 
20.56 
0.00 
+ hook*species*leader 
Table 6 
Percentage of fish caught in two anatomical locations (jaw vs. “deep” [body, gill, gut, eye]) with trolled circle and J hooks. The x 2 
test statistic and P-value from each test of independence comparing hooking locations between hook types are presented for each 
species. A x 2 test was not conducted for king mackerel because of small sample size. 
Circle hook J hook 
Species 
Jaw 
Deep 
Jaw 
Deep 
X 2 
P 
Dolphinfish ( Coryphaena hippurus) 
98.5 
1.5 
61.3 
38.7 
31.35 
<0.001 
Yellowfin tuna ( Thunnus albacares) 
100 
0 
100 
0 
— 
— 
Wahoo ( Acanthocybium solandri) 
100 
0 
91.3 
8.7 
1.82 
0.177 
Blackfin tuna (Thunnus atlanticus) 
100 
0 
92.6 
7.4 
1.13 
0.287 
King mackerel (Scomberomorus cavalla ) 
100 
0 
66.7 
33.3 
toward the shank. Having discussed the structure 
of the hooks with captains, Smith (2006) postulated 
that a greater turn in the point shank (a point shank 
that turns back towards the hook shank by >33°) re- 
duces the chances for deep hooking in billfishes. This 
outcome has yet to be determined with experimental 
fishing and would be a useful area of future research. 
We measured the angle between the point shank and 
hook shank to be roughly 25 degrees for the circle 
hooks we used (regardless of the size). Compared with 
the circle hook styles we tested, other circle hooks with 
different point shank angles that still satisfy federal 
requirements may have performed better at catching 
non-billfish species. 
The fishing tackle industry and charter boat opera- 
tors continually adapt gear and techniques to increase 
