100 



?no 



300 



Figure 5. --Vertical temperature section south- 

 southeast of Cape Ashizuri (1936, from Semi- 

 ann. Rpts. of Oceanog. Obs.) 



. January 

 February 



Figure 6. --Distribution of 

 isotherms in KinaJi area. 



as far as 27 N. Within the area of the main 

 flow of the Kuroshio, although there are occa- 

 sional outstanding values indicated, in general 

 the catch rates have become low. 



No southward nnovement can be detected 

 as compared with the positions of the fishing 

 grounds in January. However, there is a fur- 

 ther expansion to the west, and the grounds 

 are almost in contact with the Ryukyu archi- 

 pelago. In the overall view, the catch rates 

 are even higher than in January, with an 

 average of 2. 73 as compared with 1.95 in 

 January in this area (north of 27 N. , between 

 130 E. and 140 E. ). (In March it drops some- 



what to 2. 31. ) The average catch rates for 

 this area show considerable differences from 

 year to year, having been 3.60 in 1949, 3.39 in 1950, 4.45 in 1951, and 

 3.05 in 1952. (Since the charts of the average year's fishing conditions 

 include data from coastal operations, which are mainly aimed at catching 

 sharks, the values they show for these 4 years are all somewhat lower.) 

 Data are comparatively scarce for the period 1949 to 1951, so the values 

 shown cannot be relied on completely, but they indicate that the catch rates 

 are high and low every other year. The high catch rate in the odd-numbered 

 years agrees well with the situation in the Okinotorishima fishing ground. 

 On the other hand, it differs from the trend in the part of the North Pacific 

 fishing ground lying east of the Izu and Ogasawara archipelagoes. The 

 alternate -year phenomenon also appears to be seen in the manner in which 

 the areas of high catch rates appear, for in even-numbered years the zone 

 of high catch rates advances westward to the vicinity of 135°E., or even 

 west of that longitude, whereas in odd-numbered years it appears farther 

 east between 135 E. and 140 E. longitude. 



90 



