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STATUS REPORT: TUNAS IN THE INDIAN OCEAN 



by 



Fletcher V. Riggs 



Southwest Fisheries Center 

 Honolulu, Hawaii 



ABSTRACT 



The status of stocks of four species of tuna (albacore, bigeye, 

 yellowfin, and skipjack) in the Indian Ocean were analyzed. Since 1962 

 estimated annual catch of albacore in the Indian Ocean has fluctuated 

 widely between 10,000 and 28,000 mt. The estimated catch for 1978 was 

 14,600 mt. MSY lies between 15,000 and 20,000 mt. A yield-per-recruit 

 assessment suggests no gain in yield-per-recruit from harvesting the 

 younger fish as fishing effort moved into more southerly waters. This 

 stock appears fully harvested and there appears to be no reason for concern 

 over the future of the stock at this time. 



Estimated annual catch of bigeye tuna in the Indian Ocean reached a 

 high of 48,600 mt in 1978. A production model analysis did not produce a 

 reliable prediction of MSY. The yield curve showed increasing catch with 

 effort and did not reach an asymptote. This stock appears to be only 

 1 ightly exploited. 



Yellowfin tuna in the Indian Ocean are fished by surface and longline 

 gears. Estimated annual catch fluctuated widely from 1952 to 1978 but 

 exhibited a general upward tend. The estimated total catch for 1978 was 

 62,500 mt. Production model analyses based on available longline fishery 

 data suggest an MSY for that fishery of around 40,000 mt. Due to rather 

 inaccurate total catch estimates, however, MSY may be higher. It is 

 unlikely that longline catch could be increased appreciably above the 

 current level. However, it is generally felt that there is a potential for 

 increased landings of yellowfin tuna by surface fisheries. 



The surface skipjack tuna fishery in the Indian Ocean is relatively 

 undeveloped. Catches have fluctuated from 1965 on a generally rising 

 trend. Estimated catch for 1978 was 32,600 mt. There have been no 

 quantitative assessments of the Indian Ocean skipjack tuna stock. 



