It is an attractive notion that the variations in catch rates associated with latitude are 

 a reflection of variations in the circulation of the ocean in the vicinity of the Equator in the 

 western Pacific. The attractiveness is enhanced by the knowledge that the major currents flow 

 either east or west in that area (fig. 11), resulting in rapid changes in the environment on its 

 north-south axis and little change along its east-west axis. This simple observation of the en- 

 vironment correlates rather well with the observation that within the mothership area there was 

 little consistent change in abundance with longitude, and considerable cheinge in abundance with 

 latitude, with yellowfin most abundant near the Equator. 



DECEMBER- MARCH 



150° 160° 170° 



JUNE - SEPTEMBER 



Figure 11. --Location of the major currents in the mothership 

 area of operation (after Schott 1935). 



23 



