268 
Effects of lunar cycle and fishing operations 
on longline-caught pelagic fish: 
fishing performance, capture time, 
and survival of fish 
Francois Poisson 1 
Jean-Claude Gaertner 2 
Marc Taquet 3 
Jean-Pierre Durbec 2 
Keith Bigelow 4 
Email address for contact author: Francois.Poisson@ifremer.fr 
1 IFREMER - Centre de Recherche Halieutique Mediterraneen et Tropical 
B.P. 171, Av. Jean Monnet 
34203 Sete Cedex, France 
2 Centre d'Oceanologie de Marseille 
LMGEM, UMR CNRS 6117 
Station Marine d'Endoume 
Rue de la Batterie des Lions 
13007 Marseille, France 
3 Centre IFREMER du Pacifique 
B.P. 7004 
98719 Taravao, French Polynesia 
4 Pacific Islands Fisheries Science Center, NOAA Fisheries 
2570 Dole Street 
Flonolulu, Hawaii 96822 
Abstract — Commercial longline fish- 
ing data were analyzed and experi- 
ments were conducted with gear 
equipped with hook timers and time- 
depth recorders in the Reunion Island 
fishery (21°5'S lat., 53°28'E long.) to 
elucidate direct and indirect effects of 
the lunar cycle and other operational 
factors that affect catch rates, catch 
composition, fish behavior, capture 
time, and fish survival. Logbook 
data from 1998 through 2000, com- 
prising 2009 sets, indicated that 
swordfish (Xiphias gladius) catch- 
per unit of effort (CPUE) increased 
during the first and last quarter of 
the lunar phase, whereas albacore 
( Thunnus alalunga) CPLTE was high- 
est during the full moon. Swordfish 
were caught rapidly after the longline 
was set and, like bigeye tuna (Thun- 
nus obesus ), they were caught during 
days characterized by a weak lunar 
illumination — mainly during low tide. 
We found a significant but very low 
influence of chemical lightsticks on 
CPUE and catch composition. At the 
time the longline was retrieved, six 
of the 11 species in the study had 
>40% survival. Hook timers indicated 
that only 8.4% of the swordfish were 
alive after 8 hours of capture, and two 
shark species (blue shark [Prionace 
glauca ] and oceanic whitetip shark 
[ Carcharhinus longimanus ]) showed 
a greater resilience to capture: 29.3% 
and 23.5% were alive after 8 hours, 
respectively. Our results have impli- 
cations for current fishing practices 
and we comment on the possibilities of 
modifying fishing strategies in order 
to reduce operational costs, bycatch, 
loss of target fish at sea, and detri- 
mental impacts on the environment. 
Manuscript submitted 19 August 2009. 
Manuscript accepted 22 March 2010. 
Fish. Bull. 108:268-281 (2010). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Empirical studies have shown that 
surface longlines set at night are 
more productive for capturing sword- 
fish ( Xiphias gladius) than lon- 
glines set during the day (Kume and 
Joseph, 1969). Studies with ultra- 
sonic telemetry have proved useful 
for understanding habitat distribu- 
tion and for providing some insights 
into short-term horizontal and verti- 
cal movements of swordfish (Carey 
and Robinson, 1981; Carey, 1990). 
Recently, more advanced tagging 
technology devices, such as archival 
tags (Takahashi et al., 2003) and pop- 
up satellite archival tags (Canese et 
al., 2008; Neilson et al., 2009), have 
provided comprehensive information 
on the diel behavior of swordfish and 
their movement patterns, both of 
which indicate the ability of sword- 
fish to navigate to long distance feed- 
ing areas in the Pacific and Atlantic 
oceans and Mediterranean Sea. Ver- 
tical movement data obtained from 
these various studies have shown diel 
diving patterns to be very consistent, 
as have been observed in other pelagic 
fishes (Musyl et al., 2003). During the 
daytime, swordfish can spend most 
of their time at depths between 250 
and 650 m (Canese et al., 2008) and 
as deep as 900 m (Takahashi et al., 
2003). At crepuscular hours, they 
swim up and down through a consid- 
erable range of depths following the 
movements of organisms in the deep 
sound-scattering layers but restrict 
their movements to forage in the 
uniform surface mixed-layer during 
the night. They also feed during the 
day and can demonstrate basking 
behavior. Carey and Robinson (1981) 
suggested that swordfish swimming 
activity in the water column is closely 
associated with prey locations and 
concluded that lunar illumination was 
a determining factor influencing verti- 
cal migrations. Swordfish are “strike 
and return” feeders (Nakamura, 1983) 
targeting fast-moving prey. Sword- 
fish can achieve a maximum speed of 
