A« the figure shows, the catch rates are highest near the Equator, falling 



off 



-._ .„^ o . ---o ^ O -1 > — o — 



sharply to the north, with the low point in the vicinity of 12 to 14 N. North of this latitude, 

 the curve slowly rises again and there is a blunt peak in the vicinity of 18 to 20 N. North of 

 this latitude, the curve again drops off steeply ajid from 30 N. latitude on to the northward the 

 catch rate is practically zero, indicating only a vestigial occurrence of the species. 



Thus the various curves taken together show a general trend, but there axe regional 

 differences of some extent in the position of the peciks and low points and also in their magnitudes. 

 There are also cases like that of the area between 120 and 130 E. longitude where the inclina- 

 tion of the curve is conspicuously gentler than In other regions. 



I I I I 1 I I I 



Ul 



< 



X 



o 



< 



5 - 



4 - 



3 - 



2 - 



I - 



-• I20°E-I30°E 



-^ I40°E-I50°E 



-o I30''E-I40''E 



-a I50''E-I60''E 



J 



CO o cvi 



J ol ol 

 ID 00 O 



2 (D 

 .1 ol 



h 



NORTH LATITUDE 



Figure 30. --Fishing conditions at different latitudes 

 (yellowfin tuna) 



As has already been stated, seasonal changes are apparent in the density of 

 occurrence of the yellowfin. The data used in this figure are not ecjually representative of all 

 seasons in all regions but show a marked tendency toward an uneven distribution. As the curve 



154 



