Figure 13. — Major circulation features of the Pacific Ocean. [Based on Sverdrup, Johnson, and Fleming (1946) and [U.S.] 



Bureau of Commercial Fisheries 1 1963). | 



Western Pacific— At least three groups, perhaps 

 more, may be present in the northwestern Pacific (north 

 of the equator and west of long. 180°). The westernmost 

 groups, originating off the Philippine (NWl) and the 

 Mariana-Marshall islands (NW2) in the first quarter, 

 apparently move northward through Japanese waters in 

 the second and third quarters and return south in the 

 fourth quarter (Fig. 14). The third group (NW3), origi- 

 nating east of the Marshall Islands, moves northwest- 

 ward into the Japanese offshore waters in the second 

 and third quarters and returns southeastward in the 

 fourth quarter to the area southwest of Midway Island. 

 Part of this group could move farther downstream of 

 the Kuroshio to the area east of Midway Island. 



In the area south of the equator and west of long. 

 180°, two major movement patterns are suggested. The 

 group (SWl) off northeastern Australia moves south- 

 ward along the continent in the first quarter, then 

 eastward south of New Caledonia in the second and 

 third quarters, and returns northward either through or 

 slightly west of the Fiji Islands in the fourth quarter. 

 At or near the equator, part of this group may continue 

 northward and subsequently mix with the western 

 groups in the northern hemisphere, while the other part 

 continues westward, returning south in the following 

 season. The second major movement pattern is seen in 

 the group (SW2) originating near the Gilbert Islands in 

 the fourth quarter. This group follows a path southwest- 

 ward into waters east of New Guinea in the second 

 quarter of the following year and into waters off New 

 (ilaledonia in the fourth quarter. 



Eastern Pacific— The group (NEl) in the eastern 

 Pacific north of the equator (east of long. 130°W) likely 

 originates in equatorial waters, mainly in the NEC. Its 

 movement is toward the Mexican coast in the second 

 quarter, north along the coast in the third quarter, and 

 subsequently back to equatorial waters in the fourth 

 quarter (Fig. 14). Part of this group (NE2) branches 

 eastward toward Cocos Island (perhaps fish that form 

 part of the southern fishery) and returns westward in 

 the SEC. The proposed movements of these fish gen- 

 erally agree with the movements of fish in the surface 

 fishery as determined from tagging results by Fink and 

 Bayliff (1970), and are similar to those proposed by Roth- 

 schild (1965) and Williams (1972) for this area. Although 

 Fink and Bayliff (1970) do not show any tagging effort 

 in the Clipperton Island area, a recovery at Cocos Island 

 of a skipjack tuna tagged in the Revilla Gigedo Islands 

 (Inter-American Tropical Tuna Commission 1966) sug- 

 gests that the route of group NE2 (Fig. 14) is not 

 improbable. 



In the area south of the equator (east of long. 

 130°W), the movement suggested by the longline catch- 

 es is generally southward in the first and second quar- 

 ters and northward in the third and fourth quarters. The 

 area seems to contain several groups (SEl, 2, 3), which 

 revolve about an area midway between the Society 

 Islands and the South American coast. The movement 

 patterns of these g^roups correspond with the circulation 

 gyre formed by the South Pacific, Peru, and South 

 Equatorial Currents. The data suggest that these groups 

 may require more than a year to complete the circuit. 



23 



