SEXUAL MATURITY AND SPAWNING OF ALBACORE IN THE 



PACIFIC OCEAN 



By Tamio Otsu and Richard N. Uchida, Fishery Research Biologists, Bureau of Commercial Fisheries 



The albacore, Germo alalunga (Bonnaterre), is 

 a commercially important tuna, valued highly for 

 its excellent canning qualities. Jn the Pacific the 

 major fisheries for this species are conducted by 

 the Japanese in an area extending from the coast 

 of Japan to the vicinity of the International Date 

 Line, and by the Americans along the west coast 

 of the United States. Tag recoveries during 

 recent years have shown that albacore undertake 

 extensive migrations across the Pacific (Ganssle 

 and Clemens 1953, Blunt 1954, Otsu and Uchida 

 1959), thus suggesting that these major fisheries 

 may be dependent on a single population. 



Albacore are also widely distributed throughout 

 the tropical Pacific, but in this region they are 

 generally taken incidental to the catch of other 

 species of tuna. It is not known whether albacore 

 of the tropics belong to the same population as 

 those of temperate latitudes, or whether they form 

 part of another population. According to present 

 knowledge, albacore do not spawn in temperate 

 waters. Information on the areas of spawning 

 might provide a clue to the general distribution of 

 the populations that support the American and 

 Japanese albacore fisheries. 



The research program of the Pacific Oceanic 

 Fishery Investigations (POFI) of the Bureau of 

 Commercial Fisheries has included a study of gon- 

 adal development and spawning in the albacore, 

 which has been financed by the Saltonstall-Ken- 

 nedy Act (Public Law 466, 83rd Congress). The 

 present report on the albacore is based on examina- 

 tion of the reproductive organs, principally the 

 ovaries, collected in three general areas: the North 

 Pacific, the Hawaiian Islands, and the central 

 equatorial Pacific. Important differences in gonad 

 development were noted for fish from these three 

 areas. The size at which albacore attain sexual 

 maturity was determined, and what appears to be 

 a major spawning locality can now be defined. 



Note.— Approved for publication January 13. 1958. Fishery Rulletin 148. 



We gratefully acknowledge the contributions of 

 the following persons: It. S. Shomura and B. 

 Wyatt who collected ovaries at the Honolulu 

 auction markets; the managements of the United 

 Fishing Agency, Ltd., and the Hawaii Fishing Co., 

 Ltd., and the several fish dealers who permitted 

 us to sample the albacore landings; Shoji Ueyanagi 

 of the Nankai Regional Fisheries Research Labo- 

 ratory in Kochi, Japan, who sent us samples of 

 ovaries; and H. S. H. Yuen for valuable suggestions 

 pertaining to sampling procedure. 



SOURCE OF MATERIALS 



NORTH PACIFIC 



A total of 126 gonads from both sexes was 

 collected between January 1955 and November 

 1956 in the North Pacific on POFI's exploratory 

 fishing cruises (table 1 and fig. 1). Most of the 

 sampled fish, ranging in length from 50 to 112 cm. 

 (weight, 6 to 65 lbs.), were taken at the surface 

 by gill nets or trolling; the few albacore larger 

 than 87 cm. were taken exclusively on longline 



Table 1. — The number of albacore gonads obtained in the 

 three areas ' in various years 



1 Fish of both sexes were sampled in the North Pacific but only females in 

 the other two areas. 



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