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Fishery Bulletin 100(4) 



tropical areas. If we compare the spatial distribution of 

 the sailfishes with the spatial distribution of the marlin, 

 we find that the bycatch of sailfishes was associated more 

 with school sets than with FAD sets (Figs. 3 and 4). How- 

 ever, the "sampling scheme" adopted for assessing these 

 incidental catches was constrained by the purse seiners' 

 fishing-effort distribution. Consequently, because purse 

 seiners move seasonally from one area to another, there is 

 a lack of information about the presence of billfishes when 

 the fishing area is temporarily abandoned. 



In both runs of the Monte Carlo simulation we used the 

 same conditional probability about the presence of each 

 billfish group by fishing mode (Table 1), as well as for the 

 observed distribution of the bycatch per set by fishing 



mode. Results indicated that the bycatch of marlins de- 

 creased during the moratorium from 396 t to 289 t (Table 3 

 and Fig. 5). This result is a consequence of the larger as- 

 sociation of marlins with floating objects than with school 

 sets. In looking at Table 1, we can see that the occurrence 

 of marlin was around 35% for FAD fishing operations com- 

 pared to only 4'7f for school sets. Marlin were also present 

 in 25% of the seamount sets but, from the small number of 

 sets made on seamounts, we could not determined any ap- 

 parent effect on the total bycatch for this group. Sailfishes 

 were more commonly observed in school sets than in FAD 

 sets (Table 1 ). Thus it appeared that the bycatch of sailfish 

 increased from about 15 t to 38 t with a moratorium on 

 FADs, as summarized in Table 3 and Figure 5. 



