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Fishery Bulletin 97(2), 1999 



been attained with only a 1 to 2.3% reduction 

 in the catch of target species, depending on the 

 spatial resolution employed. This reduction 

 would have been achieved by eliminating the 

 effort in months and areas where the reported 

 billfish bycatch exceeded the threshold percent- 

 age of billfish in the combined catch in Table 2. 

 Similarly, a 509c reduction in the 1986-91 bill- 

 fish bycatch would have been achieved by elimi- 

 nating the effort in cells where the reported bill- 

 fish bycatch exceeded the table values with cor- 

 responding reductions of 13.9 to 19.2% in the 

 harvest of target species. A 95% reduction in 

 the 1986-91 billfish bycatch would have been 

 achieved by eliminating all effort in cells with 

 reported catches of more than 1.2, 1.15, or 1.26% 

 billfish for 1°, 2°, or 5° cells, and there would have 

 been a concomitant reduction in target species 

 catch of 56.1, 61.5, or 65.1%, respectively. 



The same type of analysis was conducted with 

 only blue and white marlin as the billfish spe- 

 cies of concern. The results are presented in 

 Figure 2 and Table 3. As with billfish combined, 

 the initial slope of the relation between the per- 

 cent catch of marlin bycatch and of target species is 

 much less than 1.0. This result also indicates that 

 the combined marlin bvcatch can be reduced by the 



(/) o 





o 



Q. 



(D 



10 20 30 AO 50 60 70 60 90 



Billfish percentage reduction 



Figure 1 



Percent reduction in target species and marlin bycatch associ- 

 ated with the removal of effort in time-area cells above the indi- 

 cated threshold percentage of all billfish in the catch for cell sizes 

 of V, 2", and 5= of latitude and longitude. 



elimination of select time-area strata and that the 

 catch of target species would not be proportionately 

 affected. The data from Table 3 indicate that a 10% 



