TUrning to the temperature sections along each fishing 

 line (figs. 3 and h) , it is apparent that, as might be expected from 

 the wind observations, some upwelling was taking place in the vicinity 

 of the Equator in each instance. Note especially the decreased surface 

 temperature and the doming up of the isotherms near the Equator. The 

 approximate location of the easterly flowing Countercurrent., included 

 for orientation in figures 3 and U, was determined on the three 

 western sections by a combination of ship's drifts, drifts of the 

 longline while on station, and GEK^f fixes by the H ; M Smith while 

 in close company with the fishing vessel. On the two eastern sections 

 (120° and 130°) the location of the Countercurrent was taken from 

 U. S, Pilot Charts for the appropriate months. 



Consideration of the results of the longline fishing 

 (fig. 5) with the observations on the hydrographic structure (figs. 

 3 and U), the winds observed during the fishing (table 3), and the 

 mean or average winds represented on the Pilot Charts indicates good 

 agreement with what might have been expected a priori . Each of the 

 five sections (fig. 5 and table Ii) shows a zone near the Equator 

 in which yellowfin tuna were more abundant than to the north and 

 south and which, in all likelihood, is associated with the upwelling 

 suggested in the temperature sections. The more precise latitudinal 

 location of the greatest concentration of yellowfin appears compatible 

 with the average winds recorded on the Pilot Charts and the observed 

 winds during the fishing. For instance the 120° and 130° sections 

 which were associated with southeast winds, had their peaks of 

 abundance north of the Equator, The 155° and 169° sections, which 

 were associated with variable winds, had their peak abundance of 

 yellowfin nearly centering on the Equator, and the ISO section, 

 associated with northeast winds, had its peak of yellowfin abundance 

 displaced to the south. 



Including the two sections previously reported on by Murphy 

 and Shomura (1953), there are seven sections reconcilable with the 

 theory that, through upwelling, southeast winds create a favorable 

 environment north of the Equator, northeast winds tend to create a 

 favorable environment south of the Equator, and van. ast 

 winds create a favorable environment tending to center on the Equator. 

 This is advanced with no implications as to the exact level of 

 abundance that the yellowfin will attain in the "zone of greatest 

 abundance " Predictions of the level of abundance would appear to 

 involve many more complexities than simple prediction of the loca- 

 tion of the greatest abundance on the basis of prevailing winds 

 at and near the Equator „ 



zJ Geomagneticelectrokinetograph, an instrument for measurement of 

 surface currents. 



E 



