18 



In the South Pacific, annual landings varied from 0.4 to 1.0 

 million fish for the Japanese tropical longline fishery and 

 from 1,300 to 93,000 fish for the Chilean fishery. 



Four age groups were represented in the U.S. west coast 

 albacore catch with the 3-year-olds constituting roughly 68 

 percent of the landings by weight. 



For the small Chilean fishery the catch was estimated to 

 be composed of about seven age groups with the 3-year-olds 

 contributing about 80 percent of the total. 



In the Japanese spring live-bait fishery, seven age groups 

 were represented, and, though the dominant age group differed 

 from year to year, the 4- and 5-year-olds usually dominated 

 and contributed nearly 85 percent to the catches. The Japanese 

 winter longline catches were comprised of 10 age groups, 

 among which the 4-year-olds and the 5-year-olds were the 

 most important groups, accounting for 29 and 27 percent of 

 the catches. Seven age groups made up the catches of the 

 South Pacific Japanese tropical longline fishery where the 

 dominant group of 6-year-olds constituted 40 percent of the 

 total landings. 



To learn more about the early life history of albacore, we 

 have continued to collect and examine juveniles from the 

 stomachs of large predatory fishes. Although only a few speci- 

 mens have been obtained in this way it has been by far the 

 most successful collection method we have found to date. 

 Between June 1960 and November 1962, a total of 12 juvenile 

 albacore, rangingfrom 61 mm. to 283 mm. in standard length, 

 was found in the stomachs of predators taken between the 

 Hawaiian Islands and longitude 170° E. in the North Pacific 

 and between longitude 163° W. and 179° E. in the South Pacific. 

 The fact that these juveniles were taken at such widely scat- 

 tered points of the Pacific strongly supports the findings of 

 our earlier studies on albacore spawning habits, which had 

 indicated spawning in a broad area of the North and South 

 Pacific. 



Juvenile albacore were identified by the presence of the 

 uniquelaterally flattened shape of the haemal spine of the first 

 caudal vertebra (fig. 21). This character, which is definitive 



tUllU|llil|illl|llti l)li|llll ilil|litl llll|iill|llil|ill 



5 6 7 8 9 90 



Figure 21. --Portion of axial skeleton of juvenile 

 albacore showing laterally flattened haemal 

 spine. 



early in the life of the albacore, was found to be useful for 

 differentiating this species from other tuna. Its presence 

 was recognized in a specimen as small as 61 mm. in standard 

 length. 



As is to be expected, we also found that some other charac- 

 ters which distinguish adult albacore were not definitive in the 

 juveniles in our collection because these characters change 

 with growth. The configuration of the first haemal arch appears 

 to be such a character. 



The information accumulated from albacore studies made to 

 date at the Biological Laboratory suggests strongly that all 

 North Pacific albacore belong to a single intermingling popu- 

 lation; also that the South Pacific albacore population is con- 

 fined to the Southern Hemisphere and is discrete from that of 

 the Northern Hemisphere. Tagging studies have been of prime 

 importance in reaching these conclusions. 



