Poisson et al.: Effects of lunar cycle and fishing operations on longline catches 
279 
reducing the market price of the fish. Shortening the 
soaking time could reduce the chance of depredation by 
large marine mammals (e.g., false killer whale [ Pseu - 
dorca crassidens ], shortfin pilot whale [ Globicephala 
macrorhyncus ]) and sharks on longline-caught fish. 
In the United States, limits on the length of a pelagic 
longline set have been proposed as a management meas- 
ure to reduce bycatch (Kerstetter, 2008). It has been 
demonstrated that such a restriction would reduce the 
interaction rate of longlines with marine mammals in 
the Mid-Atlantic Bight by approximately 26%. 1 
The survival rates for blue shark and oceanic whitetip 
shark were estimated to be 49% and 41%, respectively. 
The survival rate of blue shark at haulback after a 
soak during the night was lower than that during day 
longline sets: 100% (Boggs, 1992), 80-90% (Campana et 
al., 2005), 69% (Diaz and Serafy, 2005), and 87% (Fran- 
cis et al., 2001). Differences in survival rates among 
studies may result from hook types, leader material 
(monofilament or wire), and handling procedures, al- 
though survival rates between day and night longlining 
should be further investigated. Nevertheless, reducing 
the soaking period would increase the number of sharks 
released alive. The release of live bycaught sharks 
(Moyes et al., 2006) and billfish (Kerstetter and Graves, 
2006, 2008) is by far the best management measure 
to reduce longline fishing mortality of these species. 
From a cost benefit perspective, fishermen believe 
that chemical lightsticks improve fishing performance 
but they limit the number deployed because of the price. 
However, our data strongly indicate that the use of 
lightsticks did not increase swordfish catch by very 
much. Lightsticks are suspected to attract sea turtles 
to the vicinity of longlines (Wang et al., 2007) and thus 
may increase their incidental catch; however, light- 
sticks have a limited lifespan and are not reusable 
and thus are an environmental concern. Thousands of 
spent lightsticks are discarded at sea and constitute a 
potential toxicant to marine flora and fauna. In the case 
of Reunion Island, local fishermen were keen to retain 
used chemical lightsticks onboard, store them during 
the fishing trip, and offload them when returning to 
port after a significant awareness campaign about the 
negative environmental impact of lightsticks. In light 
of our results and for ecological concerns (Ivar do Sul 
et al., 2009; Pinho et al., 2009), the use of chemical 
lightsticks should be reconsidered. Recently, the work- 
ing group of the General Fisheries Commission for the 
Mediterranean (GFCM) has proposed a ban on chemical 
lightsticks and any light source in the pelagic longline 
fishery in the Mediterranean Sea. 2 
1 APLTRT (Atlantic Pelagic Longline Take Reduction 
Team). 2006. Atlantic pelagic longline take reduction plan, 
97 p. Submitted to the National Marine Fisheries Service 
Southeast Regional Office, St. Petersburg, Florida. 
2 Report of the transversal working group on bycatch/incidental 
catches; Rome, Italy, 15-16 September 2008, 17 p. General 
Fisheries Commmission for the Mediterranean (GFCM), 
(http://www.gfcm.org/gfcm). 
Complementary three-dimensional acoustic telem- 
etry experiments are needed to better understand the 
movements of swordfish and to test the hypothesis that 
tidal and oceanic currents may influence their foraging 
behavior and fishing operations associated with their 
foraging behavior. We also recommend additional stud- 
ies to understand the interaction of lunar luminescence 
and swordfish size because of concerns for the sustain- 
ability of swordfish stocks and for the protection of 
certain age classes (Poisson and Fauvel, 2009). 
Acknowledgments 
Funding for the PPR programme was supported by the 
European Union (FEDER), the Conseils Regional, and 
General de La Reunion. We express our gratitude to the 
fishing industry of Reunion Island for their outstand- 
ing support. We are very grateful to J. F. Reynaud, C. 
Marjolet, D. Guyomard, and M. Vanpouille for their 
work completed within the framework of the project. We 
also acknowledge R. Galzin (University of Perpignan, 
France) for his support. We thank M. Musyl for provid- 
ing helpful advice. We thank the editor and the three 
anonymous reviewers who improved the manuscript 
with insightful suggestions and P. Lopez for his input 
on the improvement of the illustrations. 
Literature cited 
Bigelow, K. A., C. H. Boggs, and X. He. 
1999. Environmental effects on swordfish and blue 
shark catch rates in the US North Pacific longline 
fishery. Fish. Oceanogr. 8:178-198. 
Bigelow, K., M. K. Musyl, F. Poisson, and P Kleiber. 
2006. Pelagic longline gear depth and shoaling. Fish. 
Res. 77:173-183. 
Bigot, L., A. Gremare, J. M. Amouroux, P. Frouin, O. Maire, and 
J.-C. Gaertner. 
2008. Assessment of the ecological quality status of soft- 
bottoms in Reunion Island (tropical Southwest Indian 
Ocean) using AZTI Marine Biotic Indices. Mar. Pollut. 
Bull. 56:704-722. 
Boggs, C. H. 
1992. Depth, capture time and hooked longevityof 
longline-caught pelagic fish — timing bites of fish with 
chips. Fish. Bull. 90:642-658. 
Bonfil, R. 
1994. Overview of world elasmobranch fisheries, 119 p. 
FAO Fish. Tech. Paper 341. FAO., Rome. 
Brill, R. W„ D. B. Holts, R. K. C. Chang, S. Sullivan, H. Dewar, 
and F. G. Carey. 
1993. Vertical and horizontal movements of striped 
marlin ( Tetrapturus audax) near the Hawaiian-Islands, 
determined by ultrasonic telemetry, with simultane- 
ous measurement of oceanic currents. Mar. Biol. 117: 
567-574. 
Campana, S. E., L. Marks, W. Joyce, and N. E. Kohler. 
2005. Catch, by-catch, and indices of population status 
of blue shark (Prionace glauca) in the Canadian 
Atlantic. Col. Vol. Sci. Pap. ICCAT 58(3):891-934. 
