Graves and Horodysky: Conservation benefits of circle hooks in multispecies recreational billfish fisheries 
437 
A 
Q. 
Q B 
Figure 2 
Depth plots derived from pop-up satellite archival tag pressure data 
for two blue marlin ( Makaira nigricans ) caught in the western Atlantic 
recreational fishery. (A) Blue marlin no. 49 was caught on a naked 
ballyhoo bait with a circle hook. This fish survived for the ten day 
tagging period and exhibited a strong diel pattern, diving during the 
day and remaining in surface waters at night. (B) Blue marlin no. 41 
was caught on an artificial lure (Ilander) and ballyhoo combination 
bait with a J hook and was bleeding profusely from the gills at the 
time of capture. This fish died and sank to the bottom shortly after 
release. The release mechanism on the tag was activated by constant 
depth measurements for 48 hours and the tag floated to the surface 
and began transmitting data. 
nificantly lower rates of internal hooking 
locations for blue marlin, white marlin, 
and sailfish. We observed incidences of 
internal hooking locations with circle 
hooks ranging from 1.8% (blue marlin) to 
6.2% (sailfish). The value of 2.0% (;i=200) 
observed for white marlin is comparable 
to the value of 1.7% (n = 59) reported for 
white marlin caught on natural baits 
with circle hooks (Graves and Horodysky, 
2008). The incidence of internal hook- 
ing locations observed for circle hooks 
in sailfish (6.2%) is slightly higher than 
that reported by Prince et al. (2002) for 
Pacific sailfish caught on trolled natu- 
ral baits with circle hooks (1.7%) but is 
within the range reported for circle hooks 
in live baits for both Atlantic sailfish 
(6-16%; Prince et al., 2007) and striped 
marlin (5-7%; Domeier et al., 2003). 
The use of J hooks in natural baits 
resulted in incidences of internal hook- 
ing ranging from 19.1% (blue marlin) to 
44.4% (white marlin). The frequency of 
internal hooking in white marlin caught 
with natural baits rigged with J hooks 
(44.4%) is similar to the value report- 
ed for white marlin caught on J hooks 
(50%) by Horodysky and Graves (2005). 
Internal hooking locations for sailfish 
caught on J hooks rigged with natural 
baits (41.2%) are comparable to results 
for Pacific sailfish caught on trolled dead 
baits rigged with J hooks (46.8%), and 
fall within the range reported for Atlan- 
tic sailfish caught on live baits rigged 
with J hooks using a variety of dropback 
times (23-57%; Prince et al., 2007), as 
well as striped marlin caught on live 
baits with J hooks (28%; Domeier et al., 
2003). The use of J hooks resulted in 
a tenfold increase in internal hooking 
locations relative to circle hooks for blue 
marlin and a twentyfold increase for 
white marlin and sailfish — a trend also 
noted in previous studies of istiophorid billfish (Prince 
et al., 2002, 2007; Domeier et al., 2003; Horodysky and 
Graves, 2005). 
Although the frequency of internal hooking locations 
was significantly higher for blue marlin, white marlin, 
and sailfish caught on J hooks than on circle hooks, the 
rate of internal hooking locations for blue marlin caught 
on J hooks was less than half of the values observed 
for white marlin and sailfish. In a study of postrelease 
mortality in the recreational blue marlin fishery off 
Bermuda, Graves et al. (2002) reported no internal 
hooking locations for the nine blue marlin caught on 
artificial lures or artificial lure and natural bait com- 
binations rigged with J hooks. The lower incidence of 
internal hooking locations for blue marlin caught on 
natural baits rigged with J hooks than for white mar- 
lin and sailfish caught on similar terminal tackle may 
result from interspecific differences in feeding ecology. 
Many billfishes follow trolled baits for a short time 
before striking, giving alert anglers an opportunity to 
pick up the rod and drop the bait back to the fish as it 
attacks. Dropback times of 5-10 s are common in the 
white marlin fishery (Mather et al., 1975; Jesien et al., 
2006), and can be considerably longer in the sailfish 
live bait fisheries (Prince et al., 2007). By contrast, 
blue marlin are typically more aggressive feeders, often 
attacking the bait before anglers have an opportunity 
to react. When dropbacks are possible for this species, 
they are often of shorter duration than those for white 
marlin and sailfish, allowing less time for the bait to 
