174 
Fishery Bulletin 1 10(2) 
Species group 
Figure 10 
Mean predicted effect size (±standard deviation) of circle versus J hooks 
on catch rates by species or taxa group. Dolphinfish ( Coryphaena hip- 
purus) is listed twice because the predicted effect size changes slightly 
in comparisons with the “tunas” and “mackerels” taxa groups. An effect 
size greater than 1 indicates greater effectiveness of circle hooks than 
J hooks; the opposite is true for an effect size less than 1. An effect 
size equal to 1 (dashed line) indicates that the hook types are equally 
effective. The mean and variance of each effect size was calculated by 
using weighted model averages from each model with positive Akaike 
weight (w { ) at the catch level (see Materials section for details). 
quirement to use them outside of Atlantic f 
billfish tournaments. Industry willing- 1 . 2 - 
ness to refine rigging techniques and 
fishing strategies in the face of future 
hook-type regulations could help increase 
experimentation with circle hooks, and 
thus catch rates of non-billfish species 
when trolling for them in this fishery. 
The workshop we convened generated 
many novel rigging and fishing tech- 
niques with circle hooks, only a fraction 
of which we used for the field experiment 
of this project. 
We urge future studies to provide catch 
rates (numbers standardized to effort), 
strike, hook-up, and retention data for 
both hook types so that trade-offs be- 
tween catch-and-release survival and 
catch rates can be evaluated. In addition, 
the terms used when discussing these 
variables should also be standardized. 
For example, the catch rate for trolled 
baits as defined by Serafy et al. (2009) 
equals a retention rate (caught if hooked), 
but a fisherman’s interest lies in know- 
ing how many fish will be caught per 
trip which is the product of number of 
strikes, proportion hooked, and propor- 
tion retained. Without knowledge of the 
first two variables, the third variable 
only provides information about a hook’s 
effectiveness at retaining a fish on the 
line and not its overall effectiveness. 
Conclusions 
We examined three mechanisms that may have been 
responsible for the hook effect on catch rates. These were 
strike, hook-up, and retention. There was little to no 
hook effect at the strike and retention levels. However, 
the differences in catch rates we observed resulted from 
a lower hook-up rate on circle hooks compared with J 
hooks. This trend was generally consistent across analy- 
ses of data on three species and on three broader taxa. 
It is unknown whether a requirement to troll exclu- 
sively circle hooks in the offshore fishery would have an 
economic impact on either the recreational or charter 
fisheries in this region. It is likely that circle hooks 
need to catch fish at rates near, equal to, or higher 
than J hooks to gain wider acceptance among offshore 
troll fishermen (Jordan, 1999). We hope that angler 
experimentation will lead to improvements in circle 
hook catch rates for non-billfish species caught during 
trolling operations. 
Acknowledgments 
This study was funded by North Carolina Sea Grant 
Fishery Resource Grant awards 08-FEG-02 and 10-FEG- 
06, and North Carolina Sea Grant awards E/GS-6, 
FEE-1, and the Big Rock Blue Marlin Tournament. We 
thank D. Kerstetter and two anonymous reviewers for 
their constructive comments on the manuscript. 
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