Figure 20. --Percentage of yellowfin catch by hook 

 number (hence relative depth) on North American 

 cruise 1, illustrating the prevalence of higher 

 catch rates on the deeper hooks. 



Figure 21. --Surface temperature and vertical temperature section along 120 W. and 109°W. 

 longitude, February-March ( Charles H. Gilbert cruise 15). Upper panel—surface tem- 

 peratures as read at each bathythermograph lowering. Lower panel- -temperature section 

 based on bathythermograph lowerings; isotherms at 2°F. intervals, depth of lowering 

 shown by horizontal dashes. 



32 



