POLACHECK: YELLOWFIN TUNA CATCH RATES 



Philippine surface tuna fishery has increased 

 dramatically and there is a suggestion that over- 

 fishing has occurred there (Floyd and Pauly 

 1984). 



It is not possible with existing knowledge to dis- 

 tinguish between these hypotheses while available 

 data suggest that all of the above may be contrib- 

 uting to the observed results. Thus, for example, 

 very limited tagging data from the western Pacific 

 suggest that the yellowfin tuna stocks may be very 

 large and that yellowfin tuna caught by longliners 

 in the Pacific can travel long distances from their 

 initial place of captxire. Ten yellowfin tuna tagged 

 by the SPC were recaptured by longliner and trav- 

 eled an average distance of 1,280 miles from their 

 point of release (unpubl. data). Tag experiments 

 from the Atlantic yielded no returns by longliners 

 which suggests that yellowfin tuna cannot be con- 

 sidered as a single homogeneous stock in that ocean 

 with respect to the different gears (Fonteneau 

 1981). Yet, the fact that surface tagged fish have 

 been recaptured by longliners in the Pacific means 

 that they are not totally distinct. A better under- 

 standing of the interactions between longline and 

 purse seine fisheries is dependent upon both a more 

 complete set of catch and effort statistics and a 

 longer time series of data, plus biological informa- 

 tion from other sources. The present low longline 

 catch rate and the importance of longline fisheries 

 in the South Pacific make this a question of imme- 

 diate concern. 



ACKNOWLEDGMENTS 



The catch and effort data base used in the anal- 

 yses in this paper would not exist without the coop- 

 eration and help of the fisheries officers from the 

 individual island states of the western Pacific. Their 

 efforts are gratefully acknowledged. In addition, 

 present and past staff of the Tuna and Billfish 

 Assessment Programme of the South Pacific Com- 

 mission were instrumental in the creation and main- 

 tenance of this data base and also provided useful 

 reviews and comments on drafts of this manuscript. 

 I also wish to thank Veronica van Kouwen for her 

 help in the preparation of this manuscript. 



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