-54- 



IV. B. Current Research Efforts 



Current Atlantic bigeye tuna research is \tery limited. Research at 

 the SWFC has concentrated on evaluation of available data for cohort, 

 yield-per-recruit, and recruitment analyses; areas where small bigeye and 

 yellowfin tunas are caught are also being identified. 



IV. C. Future Research Needs 



IV.C.l. Suggested Approach and Methods 



The following projects should be undertaken in order to 

 improve management of the fishery: 



1) Re-estimate population parameters: length-weight relation, growth 

 rates (particularly for small fish), and mortality rates. 



2) Investigate stock structure to include the relationship of 

 currently hypothesized northern and southern stocks, and the relationship 

 between longline and surface-caught bigeye tunas. 



3) Evaluate the adequacy of current data to analyze yield-per-recruit 

 and spawner/ recruit. 



4) Investigate the impacts of alternate management schemes for 

 yellowfin tuna on bigeye tuna. The extent of mixing of species and sizes 

 of fish should be determined and considered in any management scheme for 

 yellowfin or bigeye tunas. 



IV. D. Status of SWFC Data Base 



All currently available Atlantic bigeye tuna data reside on SWFC 

 data bases. Available fishery data (catch, catch/effort, and size 

 composition) for the longline fishery are minimally adequate for stock 

 assessments, but those for the surface fishery are sparse and inadequate 

 for assessments. Additional biological data are needed for both longline 

 and surface fisheries in order to assess population parameters and evaluate 

 stock structure problems. Misreporting of bigeye tuna as yellowfin, 

 although improving, continues to be a problem. Species-composition 

 sampling at all landing and transshipment ports should be continued to 

 alleviate this problem. 



