This sea area Is a part of the so-called winter albacore grounds, which extend on to 

 the eastward. The fishing season is, of course, during the winter. At Sonne seasons considera- 

 ble numbers of bigeye tuna are taken. In the sumnner spearfishes, principally the striped 

 marlin, are taken, and from late autumn to early winter considerable numbers of broadbill 

 swordfish are caught. 



Table 71 summarizes the data from surveys which have been made in this sea area. 



Table 71. --Fishing conditions in the sea area east of the 

 Izu Islands (30° to 35° N. , 140° to 150° E.) 



The overall average catch rate is slightly more than 5.0. The biggest catch is the 

 albacore, making up more than 80 percent of the whole. Next to the albacore most important are 

 the spearfishes, with the black tuna and yellowfin of little significamce. Bigeye tuna have a 

 catch rate little different from that of the Nankai sea area adjacent on the west. 



In table 72 this area is divided into five equal parts of 2 of longitude each, and the 

 fishing situation for each of these sections is shown separately. 



Table 72. --Fishing conditions by longitude (sea area east 

 of the Izu Islands) 



Looking at this sea area as a whole, with no consideration given to seasonal changes 

 in fishing conditions, there is a tendency for black tuna to be more abundant farther off the coast. 

 Yellowfin are vestigial, but they are taken quite uniformly, while bigeye tuna appear to show a 

 tendency to be sonnewhat less numerous in the central part and more abundant at the eastern and 

 western extremities, however, this tendency is not very conspicuous. Albacore are remarkably 

 scarce in the most westerly part and tend to increase in nun-ibers to the eastward, Spearfishes 

 are abundant in the coastal waters of the Izu Islands and scarcer off shore and they are taken 

 rather uniformly in the off-shore waters, with no great local variations in the catch. 



104 



