■3V 



IV. STATUS OF CURRENT RESEARCH NEEDS AND EFFORTS 



IV. A. Major Research Problems 



1) The growth relation of yellowfin tuna, particularly during the 

 juvenile period, needs to be better defined. Age composition of the catch 

 is an important input to cohort analyses and therefore important for 

 accurate estimates of recruitment and fishing mortality. Completion of 

 this research would lead to better, more accurate estimates and, therefore, 

 better management advice. 



2) The existence of a spawner/recruit relationship for yellowfin 

 tuna needs to be investigated. Completion of this research would lead to a 

 better understanding of the status of Atlantic yellowfin tuna stocks. 



3) Verification is needed of the various stock structure 

 hypotheses: single stock of longline and surface-caught yellowfin, mixing 

 of an Indian Ocean stock with Atlantic yellowfin, and separate eastern and 

 western Atlantic stocks or a single Atlantic stock. Clarification of the 

 stock structure issue would lead to more accurate assessments of the status 

 of Atlantic yellowfin tuna. 



4) Alternative management schemes for reducing the catch of small 

 yellowfin tuna should be analyzed. Although the current management scheme 

 has increased yield-per-recruit as intended, small yellowfin tuna continue 

 to be landed by some purse seine and baitboat fisheries that are 

 experiencing difficulties in implementing the 3.2 kg size limit. 



5) Continued research on the relationship between environmental 

 parameters and abundance, availability, and vulnerability of Atlantic 

 yellowfin tuna is needed. Current abundance estimates are partially based 

 on sea surface temperature. Since production models are based on these 

 estimates, verification of the technique may be critical. 



IV. B. Current Research Efforts 



Current Atlantic yellowfin tuna research is concentrated on the 

 following subjects: 



1) Trends in fishery statistics: catch, effort, CPUE, and size- 

 frequency (SWFC) . 



2) Development of new fisheries and their relation to stock 

 structure (ICCAT). 



