spearfishea, an equeil or greater number of sharks are taJcen and considerable numbers of other 

 miscellaneous fish are also captured, so it is believed that if no error is made in selecting a 

 fishing ground and if consideration is given to the season, the grounds of this area present quite 

 advantageous conditions for nnedium-sized and small vessels. 



Table 69. --Fishing conditions by months (Nankai sea 

 area) 



The Tanegaahinna area in the extreme western part of this region is famous as a black 

 tuna ground, but at present it hzis almost entirely lost its significance and vjilue as a fishing 

 ground for this species. It is thought, however, that this condition is probably the result of 

 cyclical changes in oceanographic conditions, and it is anticipated therefore that in the future it 

 will recover its value as a fishing ground. 



12. Area east of the Izu Islands (30 



35° N. 



140° - 150° E. 



The area fronn 30 

 "sea area east of the Izu Islands. " 



o o 



35 N. , 140 - 



150 E. will be described under the designation 



There are sonne fluctuations in the currents from year to year depending on the 

 difference in the strength of the Kuroshio, but the greater part of this area is within the Kuroshio 

 Countercurrent. The main stream of the Kuroshio flows along the northern edge of the area in a 

 roughly easterly direction. As the subtropical convergence runs east and west at about the line 

 of 30 N, latitude during the summer, there is in this area as a whole a clockwise gyral formed 

 by the current flowing northward from the Ogasawara Islainds region, the Kuroshio, and the 

 Kuroshio Countercurrent. In the winter the subtropical convergence gradually moves southward 

 and around February and March it is in the vicinity of 24 - 25 N. Because of this the south- 

 eastward- or south-southeastward-flowing Kuroshio Countercurrent becomes more prominent in 

 this sea area. 



Table 70 shows oceanographic conditions in this sea area on the basis of data 

 gathered on the cross-sectional observation line southeast of Cape Nojima. In February the 

 heart of the Kuroshio is about 50 to 80 nniles off the coast and the surface water temperature is 

 about 20 C. Farther off shore the temperature is down to 17. 3 C. around 100 nniles from the 

 coast, while in the vicinity of 120 miles off shore there is a zone of fairly warm water of 1 8 C. 

 to 19 C. Farther off shore the water temperature again goes down to 1 7 C. , continuing at this 

 level to the vicinity of 260 miles off the coast. At 300 miles off shore the water tennperature 



102 



