north of 30 N. to 32 N. in the sea areas east of 150 E. are particularly 

 small, with an average weight of less than 3 kan /24. 8 lbs. /. One thing 

 that stands out is a rather conspicuous exception to the tendency for the 

 size of the fish to increase as one goes offshore to the eastward, this 

 exception showing up in the southern part of the fishing grounds around 

 160 E. As can be seen from table 4, at the latitudes of 30 N. to 32 N. , 

 east and west of 160 E. , the fish on the eastern side are conspicuously 

 smaller. The same thing is true in December. The question of whether 

 or not the albacore of the North Pacific fishing grounds form a single 

 population is extremely important for any consideration of the quantity 

 of the resource, auid it is thought that, fronn this point of view, the line 

 of 160 E. longitude should be thoroughly examined. 



51 ei ri 



Ml em 



Figure 6 shows the yearly changes 

 in the length composition of silbacore east 

 and west of 160 E. longitude. In general, 

 the fish are larger on the east side of that 

 longitude. On both sides of 160 E. the 

 length class appearing most frequently 

 differs from year to year. However, any 

 length class which is conspicuous on either 

 the east or west side of 160 E. will also 

 form a peak, or a size group very close 

 to it will form a peaik, of some degree on 

 the other side of the line. The difference 

 in the positions of the peaks on either 

 side of the line is less than the difference 

 from year to year in the positions at which 

 the peaks appear in either one of the areas, 

 and this indicates that there is a consider- 

 able relatedness between the sizes of fish 

 in the two areas. 



Furthermore, there are times 

 when a comparison of the sizes of fish 

 at 150°E. to 160°E, and at 160°E. to 

 170 E. shows that they are larger between 

 150°E. and 160°E. Nevertheless, in the 



Figure 6. --Length frequency 

 of albacore taken i n the 

 North Pacific, by years. 

 The two curves represent 

 different ranges of longi- 

 tude, but the original figure is 



too small to distinguish them. ,, . , ,. , 



overall picture, the fish are bigger the 



farther one goes from Japan. The fact that this trend is a gradual one is 



thought to indicate that all of the albacore in the northwest Pacific fishing 



grounds are under the control of one great law. Figures 7 and 8 show 



respectively for 1949 and 1950 the size composition of fish between 140 E. 



and 150 E. by nnonths and by latitude in terms of percentages. Throughout 



these two figures we see that the fish are larger the fajrther south one goes, 



66 



