•US- 



UI. B. 2. Results of Production Model Analysis 



Production model analyses have been applied to Indian 

 Ocean albacore, bigeye tuna, and yellowfin tuna data (Kume and Morita^, 

 Suzuki-^, and Wetherall et al . , see footnote 1). No assessment studies have 

 been done on skipjack tuna. 



Al bacore - A MSY (maximum sustainable yield) between 

 15,000 and 20,000 mt was suggested by production model analyses. A yield 

 curve appeared to be asymptotic and there was little change in the catch 

 although effort doubled from 1966 to 1974. 



Bigeye tuna - A production model analysis did not 

 produce a reliable prediction of MSY. The yield curve showed increasing 

 catch with effort; effort levels were not high enough to indicate a maximum 

 or asymptotic yield. 



Yellowfin tuna - Production model analyses based on 

 available data suggested an MSY of around 40,000 mt. However, because 

 total catch estimates are rather inaccurate, it may be premature to 

 pinpoint an MSY for this fishery, except to indicate that it is thought to 

 be between 40,000 and 60,000 mt. 



III.B.3. Results of Yield-per-Recruit Analysis 



A yield-per-recruit assessment of Indian Ocean albacore 

 by Suda (1973) suggested no gain in yield-per-recruit from harvesting the 

 younger fish as fishing effort moved into more southerly waters. 



III.B.4. Results of Spawner/Recruitment Analysis 



Stock size indices by age for Indian Ocean yellowfin tuna 

 have been calculated under the one- and two-stock hypotheses (Suzuki, see 

 footnote 3). No relationship between stock and recruitment was evident. 



^Kume, S., and Y. Morita. 1979. Brief review of the fishery biology 

 of bigeye tuna in the Indian Ocean and its stock assessment. Prepared 

 for the Workshop on the Assessment of Selected Tunas and Bill fish 

 Stocks in the Indian and Pacific Oceans, Shimizu, Japan, 13-22 June 

 1979. 



^Suzuki, Z. 1979. Stock assessment of yellowfin tuna in the Indian 

 Ocean exploited by tuna longline fishery. Prepared for the Workshop on 

 the Assessment of Selected Tunas and Billfish Stocks in the Indian and 

 Pacific Oceans, Shimizu, Japan, 13-22 June 1979. 



