-19- 



U.S. imports of Atlantic yellowfin and bigeye tuna averaged 

 approximately 12,000 mt during 1970 to 1979 (yellowfin and bigeye imports 

 are not reported separately). The value of the 1979 imported catch (7,800 

 mt) was approximately $8 million. Virtually all domestic and imported 

 catches of Atlantic yellowfin tuna are packed and consumed in the U.S. 

 Annual total consumption of Atlantic yellowfin tuna is approximately 15,200 

 mt worth about $14 million. 



Future participation by U.S. and foreign vessels in the Atlantic 

 yellowfin fishery is difficult to determine. Based on past performance and 

 the current status of the stocks, the FISM and Spanish fleets should 

 continue to dominate surface catches, and the Korean/Panamanian and 

 Japanese fleets should dominate longline catches. New fisheries developing 

 off South Africa and Brazil may increase foreign participation. Future 

 U.S. participation is partially dependent on catches in the CVRA and the 

 outcome of regulatory measures in this area. If conditions remain as 

 present, U.S. participation should not increase from that in 1980 (6 

 vessels). The U.S. fleet in 1978 to 1980 increased their fishing activity 

 in the western Atlantic off Venezuela. Whether this increase will continue 

 in 1981 i s unknown. 



III. STATUS OF THE STOCKS 



III. A. Stock Structure 



No conclusive evidence is available on Atlantic yellowfin tuna 

 stock structure. Separate longline catch rate maxima in the eastern and 

 western Atlantic have been observed and larval studies have identified 

 important spawning areas off Brazil and in the Gulf of Guinea. Studies 

 show lower gonad indices for yellowfin tuna off Brazil than in the eastern 

 Atlantic, leading to the hypothesis of separate eastern and western stocks 

 in the Atlantic Ocean. Since this evidence is inconclusive, analyses have 

 employed both single and two stock hypotheses. 



Recent catches of yellowfin tuna off Cape Agulhas, South Africa, 

 have raised the question of whether these fish were from an Indian Ocean 

 population or an Atlantic Ocean population. Additional studies are needed 

 to answer this question. 



The hypothesis of separate yellowfin stocks available to surface 

 and longline gears has been suggested. Current evidence, although not 

 conclusive, indicates that there is a high seasonal and annual correlation 

 of CPUE indices between the two gears. Therefore, until new evidence is 

 available, fish caught by surface and longine gears are provisionally 

 thought to be of the same stock. 



