Figure 14. — Assumed movement of the various stocks of skipjack tuna in the Pacific Ocean. The numerals along the migratory routes 

 represent quarters and locations of high-CPUE cells of skipjack tuna taken by the Japanese tuna longline fishery, 1964-67. Stock 

 designations are shown in parentheses. 



Central Pacific— In the central (long. 130° W to 180°) 

 North Pacific, particularly the area between Hawaii and 

 Midway, two or possibly more groups may be present. 

 One group (NCl), originating in the NEC to the south- 

 east of Hawaii, could move directly into the Hawaiian 

 fishery in the second quarter. A portion of this g^oup 

 could move farther downstream in the CCE taking a 

 longer route before entering the Hawaiian fishery in the 

 third or fourth quarter. At least part of this group 

 consists of fish that have migrated from the eastern 

 Pacific northern fishery area. A second group (NC2), 

 originating west of Hawaii, could move into the Midway 

 Islands area in the second quarter, then continue to an 

 area northeast of Hawaii in the third or fourth quarter, 

 winter there, and move into Hawaiian waters in the 

 second or third quarter of the following year. This could 

 be a purely local group, from offspring originating in 

 Hawaiian waters. Fish from a third group of the north- 

 western Pacific (NW3) could move into the Midway 

 Islands area via the Kuroshio extension and arrive in 

 the Hawaiian fishery 1 or 2 yr later. 



In the central South Pacific at least two major 

 routes, possibly representing the same g^roup of skipjack 

 tuna, are indicated. The first group (SCI), originating at 

 the equator near long. 130°W, moves westward in the 

 first and second quarters, southward in the third quar- 

 ter, passing near the Fiji Islands, and northward in the 

 fourth quarter, into the Samoa area. The second group 

 (SC2), having the same origin as the first, moves at a 



slower pace, turning southward in the second quarter 

 and passing between Samoa and the Society Islands 

 between the fourth quarter and first quarter of the 

 following year. It turns northeastward in the second 

 quarter and arrives in the Society Islands area in the 

 third or fourth quarter. Both groups could conceivably 

 swing southward and eastward during the following year 

 and end up in the southeastern sector of the Pacific 15° 

 to 20° latitude south of the equator. 



DISCUSSION 



The movement of skipjack tuna interpreted from 

 longline catches generally agrees with that hypothesized 

 by Fujino (1972) for the western Pacific and by Roth- 

 schild (1965) and Williams (1972) for the eastern Pacific. 

 In the western Pacific, movement patterns not only bear 

 out the demarcation of the two subpopulations reported 

 by Fujino (1970a), but show that the demarcation Une 

 and area of intermingling between the two subpopula- 

 tions ag^ee quite well with those described for the 

 surface fishery. The movement patterns of the groups of 

 skipjack tuna in the western Pacific subpopulation (NWl 

 and NW2) are of particular interest since they permit 

 the qualification of Kawasaki's (1965) suggestion that 

 there is an exchange of skipjack tuna populations be- 

 tween Japanese and Hawaiian waters. The possibility of 

 such an exchange is indicated in Figure 14 (dashed line 

 from Japanese offshore waters to area east of Midway). 



24 



