Poisson et al.: Effects of lunar cycle and fishing operations on longline catches 
275 
Table 2 
Number and percentage of catch per species during experimental sets conducted from commercial vessels 
Island-based longline fishery between June 1998 and November 2000. 
in the domestic Reunion 
Common name 
Species 
Number of individuals 
Percentage 
Swordfish 
Xiphias gladius 
389 
47.8 
Blue shark 
Prionace glauca 
92 
11.3 
Bigeye tuna 
Thunnus obesus 
86 
10.6 
Albacore 
Thunnus alalunga 
79 
9.7 
Yellowfin tuna 
Thunnus albacares 
66 
8.1 
Common dolphinfish 
Coryphaena hippurus 
48 
5.9 
Oceanic whitetip shark 
Carcharhinus longimanus 
17 
2.1 
Pelagic stingray 
Pteroplatytrygon violacea 
12 
1.5 
Indo-Pacific sailfish 
Istiophorus platypterus 
7 
0.9 
Hammerhead sharks 
Sphyrna spp. 
4 
0.5 
Indo-Pacific black marlin 
Makaira indica 
3 
0.4 
Escolar 
Lepidocybium flavobrunneum 
3 
0.4 
Indo-Pacific blue marlin 
Makaira mazara 
2 
0.2 
Wahoo 
Acanthocybium solandri 
2 
0.2 
Shortfin mako shark 
Isurus oxyrinchus 
2 
0.2 
Barracuda 
Sphyraena spp. 
1 
0.1 
Leatherback turtle 
Dermoclielys coriacea 
1 
0.1 
Total hook timers triggered 
2115 
Hook timers triggered with catch 
814 
Hook timers triggered without catch 
1301 
Table 3 
Decomposition of inertia between and within groups according to the lightstick den- 
sity factor for centered principal component analysis (CPCA), factorial correspon- 
dence analysis (FCA), and associated permutation tests. 
Between lightstick density 
CPCA 
Between lightstick density 
AFC 
Total inertia 
3.234 10 2 
1.597 
Between groups 
2.046 10 1 (6.32%) 
1.391 10- 1 (8.7%) 
Within groups 
3.030 10 2 (93.68%) 
1.458(91.3%) 
Permutation test 
P<0.05 
P<0.05 
ship between prey biomass and 
lunar phase but found that prey 
size significantly increased with 
swordfish size and that this in- 
crease coincided with a dietary 
shift from fish to cephalopods 
(Palko et al., 1981). This finding 
indicates that swordfish have the 
ability to forage at considerable 
depth and temperature, which 
are afforded by a suite of physi- 
ological adaptations to enable 
opportunistic feeding within the 
deep sound-scattering layer (DSL) 
(Josse et al., 1999; Musyl et al., 
2003), Gilly et al. (2006) depicted lunar influence on the 
vertical migration of squid, which, in turn, would have 
a direct effect on the distribution and vulnerability of 
swordfish. 
We found that higher swordfish CPUE correlated 
with small tides. Moreover, at a finer scale, we found 
that higher swordfish CPUE occurred with lower tidal 
fluctuations which coincided with the possible genera- 
tion of low-velocity oceanic currents. These results were 
consistent with the results obtained when applying 
GAMs on similar scales (Guyomard et al., 2004), where 
the meridional component (V) of geostrophic currents 
derived from sea level anomaly (SLA) data was the 
most significant environmental factor within one of the 
models tested. It was likely that the low positive V val- 
ues (i.e., low velocity currents to the north) were more 
beneficial for catch rates, whereas the trend became 
clearly negative for higher velocity values. 
We assumed that the influence of the tide and associ- 
ated local current velocities would be complex and affect 
the dispersion of organisms within the DSL and other 
associated organisms of the mixed layer. In addition, 
current could affect turbidity by advecting organisms 
and particulate matter and alter the shape and depth 
obtained by the longline (Bigelow et al., 2006). To gain 
insights into swordfish behavior during complex pat- 
terns of current velocities, acoustic telemetry could be 
used to provide short-term horizontal movement data 
that could help in elucidating the effect of the tide on 
the foraging behavior of large pelagic fish. Analysis 
