Almost Jill of the fish are of large size, a characteristic which 

 is in good agreement with the fishing grounds south of the Subtropical 

 Convergence. 



Table 12. --Mean weight (in kaji) 

 of albacore tcdcenonthe Okino- 

 torishima ground, by month 

 and latitude 



Table 12 shows the average 

 weight of the albacore landed from this 

 fishing ground by area and season. As 

 the fishing season progresses, the aver- 

 age size of the fish gradually becomes 

 smcdler. We cannot, however, detect 

 any nnarked difference in the size of 

 the fish in the northern and southern 

 parts of the fishing ground as we did 

 in the North Pacific fishing ground. 



When we consider the season 

 at which this ground appears, its move- 

 ments, and the size of fish taken there, 

 we cannot discover anywhere a population which would seem to be directly 

 related to the albacore that appear in this ground. It is thought that when 

 favorable conditions for the schools to accumulate obtain in this sea area, 

 they simply assemble here like a rising tide and, eifter a few months, they 

 disperse and disappear no one knows where. This is thought to be indicated 

 by the fact that even after the end of the fishing season, considerable num- 

 bers of albacore occur in this area. We do not yet have any data on the 

 gonads of albacore from this area, nor do we have any information on their 

 stomach contents, so whether their appearance here has anything to do with 

 feeding or reproduction is connpletely unknown. 



Figure 11. 

 waters. 



■ Results of an oceanographic section in Okinotorishima 



Oceanographic conditions do not seem to differ greatly from those 

 which obtained in December. Figure 11 gives the results of sec- 

 tional observations from Okinotorishima in about a southeast direction 



76 



