Santos et al.: Effects of leader material on catches of longline fisheries in the Indian Ocean 
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Monofilament 
Wire 
Leader material 
Hooking location; □ Mouth or jaw 
Hooking mode: ■ Deep □ Externally hooked 
Figure 4 
Hooking location by leader material for the main species (no. >30) captured in 
2013-2014 in the southwest Indian Ocean. Food and Agriculture Organization 
of the United Nations species codes are used: SWO^swordfish (Xipliias gladius); 
BSH=blue shark (Prionace glauca); DOL=dolphinfish (Coryphaena hippurus); 
ALX=longnose lancetfish {Alepisaurus ferox); GES=snake mackerel (Gempylus 
serpens); and LEC=escolar {Lepidocybium flavobrunneum). The bars refer to the 
percentage of each hooking location for each leader material: 2.5-mm monofila¬ 
ment nylon and 1.2-mm multifilament stainless wire. 
ence the catch and could contribute to the differences 
between studies. Specifically, Vega and Licandeo (2009) 
used J hooks similar to those used in our study and as 
such the results are more directly comparable, whereas 
Ward et al. (2008) used Japanese tuna hooks with 10° 
offset. Another factor causing differing results may be 
related to the bait. Vega and Licandeo (2009) used a 
mix of squid and mackerel as bait on sets with nylon 
leaders and just mackerel on sets with wire leaders, 
whereas we used squid bait exclusively, which is the 
most commonly used halt in this fishery for targeting 
swordfish. Finally, it should also be noted that there 
was a difference in effort in terms of the number of 
sets conducted in each study, specifically 82 sets in our 
study, 37 sets in Vega and Licandeo (2009) and 177 sets 
in Ward et al. (2008). 
Leader type also had a significant effect in terms 
of relative catchability in both number and weight for 
some of the species or species groups (or combination of 
both) in this pelagic longline fishery. The use of mono¬ 
filament leaders trended toward higher catch rates of 
swordfish (although not statistically significant) and 
