254 



Fishery Bulletin 97(2), 1999 



lagic-longline vessels, although the amount of avail- 

 able data for the period is limited. 



Although the study results demonstrate that time- 

 area restrictions on the U.S. pelagic-longline fishery 

 could substantially reduce the bycatch of billfish by 

 this fishery, it is only a first step. As Murawski ( 1992 ) 

 pointed out, any bycatch reduction plans involving 

 time-area manipulation of the fishery should be eco- 

 nomically viable and the proposed program must be 

 effectively implemented and enforced. These issues 

 were beyond the scope of the present study. An evalu- 

 ation of the utility of time-area restrictions for re- 

 ducing the mortality of billfish in the longline fish- 

 ery must also consider aspects of the dynamics of 

 the fishery itself Among other considerations, the 

 present analysis assumes that the effort eliminated 

 by a time-area closure would not be redirected to 

 some other time or area. The catch associated with a 

 stratum removed by the selection of a particular 

 threshold of percent billfish in the catch was simply 

 removed from the total catch of both the billfish 

 bycatch and target species. With no restriction on 

 total effort, it seems more likely that the affected 

 effort would be redirected into some other area, and 

 the total billfish bycatch, although reduced, would 

 not be reduced by the magnitude indicated in Tables 

 2 and 3 (and of course, neither would the target spe- 

 cies ). Analyses that consider the possible redirection 

 of effort would need to include socioeconomic consid- 

 erations about the nature and dynamics of the pe- 

 lagic-longline fishery. Also catch limitations arising 

 from the U.S. allocation of total allowable catches of 

 the various target species by ICCAT could be inte- 

 grated into the analysis. The focus of such an analy- 

 sis would be to minimize the billfish bycatch by se- 

 lecting fishing areas that would maximize the catch 

 rates of target species in areas of minimal billfish 

 bycatch. This could both promote efficient use of the 

 target resources and the reduction of billfish bycatch. 

 Similarly, other management objectives could be in- 

 tegrated into the time-area question. 



Although, such extensions of the methods pre- 

 sented here should prove fruitful for the selection of 

 actual management restrictions, the results of this 

 study clearly indicate that the relative time and ar- 

 eal distributions of billfish and target species in the 

 pelagic-longline catch are different. This difference 

 can be exploited to reduce the billfish bycatch in this 

 fishery with less than a proportional effect on the 

 catch of targeted species. A next step toward identi- 

 fying realistic management measures could be the 

 characterization of reasonable, contiguous geo- 

 graphic areas where pelagic-longline closures would 

 be both practical and of the greatest benefit to in- 

 creased billfish sui"vival. However, because U.S. ves- 



sels are a small part of the total Atlantic pelagic- 

 longline fishery, greatest gains from this approach 

 would necessarily involve participation of the pelagic- 

 longline fleets from other countries. 



Acknowledgments 



This work was supported by The Billfish Founda- 

 tion. Analyses leading to the results presented in this 

 report were derived by using ICCAT task i and task 

 ii data files, and the U.S. large pelagic logbook data 

 files from the U.S. Department of Commerce, Na- 

 tional Oceanic and Atmospheric Administration, 

 National Marine Fisheries Service, Southeast Fish- 

 eries Science Center, Miami, Florida. I thank ana- 

 lysts of the Sustainable Fisheries Division of the 

 Southeast Fisheries Science Center for their assis- 

 tance in obtaining and using these databases. 



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