DISTRIBUTION, APPARENT ABUNDANCE, AND SIZE COMPOSITION OF 

 ALBACORE (THUNNUS ALALUNGA) TAKEN IN THE LONGLINE FISHERY 

 BASED IN AMERICAN SAMOA, 1954-65 



By Tamio Otsu, Fishery Biologist, and Ray F. Sumida, Biological Technician 



Bureau of Commercial Fisheries Biological Laboratory 



Honolulu, Hawaii 96812 



ABSTRACT 



This fishery began in 1954 when tuna canning began 

 in Pago Pago, American Samoa, with fish delivered 

 by seven Japanese longline vessels. The size of the 

 fishing fleet grew rapidly. In 1963, a second cannery 

 began operating in Pago Pago. The 105-vessel fleet 

 fishing during the last quarter of 1965 had 62 vessels 

 from Japan, 30 from the Republic of Korea, and 13 from 

 the Republic of China. The fishery was close to the 

 Samoa Islands in the early years but expanded rapidly 

 to the east and south; in 1965 it covered an area of 

 about 23 million square kilometers (6.7 million square 

 nautical miles) in the central and eastern South Pacific 

 Ocean. 



Albacore is fished selectively by the fleet because it 

 commands the highest prices at the canneries. Data 

 from the American Samoa-based fishery are complete, 

 therefore, only for the albacore catches. Data on the 



other tuna species are not analyzed. The landings of 

 albacore in American Samoa have increased from 338 

 metric tons in 1954 to 15,588 metric tons in 1965. In 

 general, the annual landings have tended to be directly 

 proportional to the total amount of fishing effort. 



Various indices of apparent abundance of albacore 

 (catch per trip, catch per day, and catch per 100 hooks 

 fished) are examined. The catch per unit of effort in 

 1954-65 showed relatively little change in terms of 

 numbers of fish, but a rather marked downward trend 

 in terms of weight. This decline was due largely to a 

 decrease in the average size of the albacore. Among the 

 possible causes for the decrease in fish size are (1) fishing 

 ground selection, (2) decrease of older, larger fish in 

 the stock due to fishing and natural mortalities, (3) 

 entry into the fishery of an abundant year class, and 

 (4) change in sex ratio of the albacore taken. 



Before World War II there was almost no long- 

 line fishing for tuna in the South Pacific Ocean. 

 After the ratification of the Peace Treaty in April 

 1952, the South Pacific Ocean became accessible to 

 the Japanese. They started fishing in the western 

 South Pacific near the Solomon Islands, princi- 

 pally for yellowfin tuna (Thunnios albacares). 

 The Japanese sent fishing expeditions to waters as 

 far south as lat. 15° S. in late 1952 and extended 

 fishing to lat. 25° S. in the western South Pacific 

 Ocean in 1953 and 1954 (personal communica- 

 tions, Naiikai Eegional Fisheries Research 

 Laboratory, Kochi, Japan) . 



In 1954, the tuna fishery based in American 

 Samoa began with a small fleet of Japanese long- 

 line vessels. A base was also established by the 

 Japanese at Espiritu Santo in the New Hebrides 



Published July 1968. 



FISHERY BULLETIX, VOL. 67, NO. 1 



in 1958 and in the Fiji Islands in 1963. Many in- 

 dependently operated vessels, without the sup- 

 port of foreign land bases or of mother ships, are 

 fishing in the South Pacific and landing their 

 catches of tunas and billfishes directly in Japanese 

 ports. Unquestionably, fishing eifort in the South 

 Pacific Ocean has increased substantially over the 

 last decade. 



The fishery was conducted exclusively by the 

 Japanese in the early years, but, beginning about 

 1958, more and more vessels from the Republic of 

 Korea and the Republic of China have been par- 

 ticipating. The Japanese early discovered the value 

 of albacore {T. alahmga) as a high-quality export 

 product. Since 1956 most of the fishing eti'ort of the 

 American Samoa-based fleet has been concentrated 

 on albacore rather than yellowfin tuna. 



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