-74- 



IV. A. Major Research Problems 



1) Improved skipjack tuna fishery statistics must be collected to 

 allow accurate assessment of stock condition and development of management 

 strategies. This applies to traditionally fished areas as well as areas 

 with developing fisheries (such as off Brazil and Ascension Island). 



2) No reliable index of abundance currently exists for eastern 

 Atlantic skipjack stocks. CPUE indices computed from data for FISM and 

 Tema-based fleets use different units of effort and therefore cannot be 

 compared. In addition, CPUE for the FISM fleet is not thought to be 

 proportional to skipjack abundance because vessels fish for this species 

 only in times of lowyellowfin availability. No viable abundance index 

 exists for eastern or western Atlantic skipjack fisheries. 



3) Minimum size regulations for bigeye and yellowfin tuna affect 

 skipjack tuna fisheries because all three species may be captured in the 

 same time/area. The impact of these regulations on skipjack fisheries 

 needs to be assessed. Such assessment can be used to infer the efficacy of 

 alternate management schemes for conserving yellowfin and bigeye (e.g. 

 time/area/closures) . 



IV. B. Current Research Efforts 



1) Improved estimates of the skipjack length/weight relation, 

 natural mortality, and growth have been developed. 



2) A preliminary assessment of the effects of minimum size 

 regulations for bigeye and yellowfin on skipjack catch has been performed. 



3) Sex ratios and age at maturation of skipjack landed at Dakar 

 (1977-79) have been determined. 



4) Migration patterns for skipjack dart- tagged and tetracycl ine- 

 marked in the Canary Islands (1979-80) have been examined. 



5) Skipjack caught south and southeast of Brazil between 1978 and 

 1980 have been examined to determine length/weight and gilled-gutted 

 weight/weight relationships. 



6) School species composition and aggregation phenomena 

 associated with tuna schools in the Gulf of Guinea (1979-80) have been 

 examined. 



7) Current status of Atlantic skipjack stocks have been assessed 

 using production model analysis techniques. 



