branch line, there were twice as many short branches as long branches used, and therefore the 

 catch rate of the long branch lines was from 5 to 6 times greater than that of the short branch 

 lines. These facts indicate that short branch lines are much less suitable than long ones as fish- 

 ing gear for this sea area. If we assunne that the sunn of the float line and branch line lengths 

 gives the depths at which the hooks are hanging, the depth was 120 feet in the case of the short 

 branches and 189 feet in case of the long branches. As there is in actuality considerable sag in 

 the main line, the positions of the hooks were deeper than this. The problem of what depth gives 

 the best catch rates cannot be settled simply by this sort of comparison of two kinds of branch 

 lines, however, in view of the length of these long branch lines it is believed that the yellowfin 

 swina at rather deep levels in this sea area. 



Because of the lack of data we have no way of knowing anything about seasonal 

 changes in fishing conditions, but it is at any rate certain that this is a rather superior fishing 

 ground from December to January. Judging by analogy with the fishing conditions in the waters 

 off Sumatra, it is probable that the good fishing continues through February and that the fishing 

 improves with the passage of time during this period. 



2. West coast of Sumatra (6° N. to 8 S. , 90 to 105 E. ) 



Most of the data for this sea area are from the operations of the Haruna Maru and the 

 HakuyS Maru. In addition a small ajnount of data has been reported by the Shonan Meiru. These 

 investigations were confined to waters very close to shore and the situation farther offshore is 

 not known. 



The pattern of the currents is roughly as follows. During the period from July 

 through September, when southerly winds blow continuously, there is a rather strong current 

 flowing eastward at 5 N. from the central portion of the Indian Ocean, The current divides into 

 two branches near the northern end of this sea area, one branch running north along the Nicobar 

 and Andannan islands, and the other flowing southeast along the coast of Sumatra. In the vicin- 

 ity of 5 S. , that is near the Sunda Strait, there is a very clear current boundary. This bound- 

 ary extends southwest from the vicinity of Sunda Strait, and from around 100 E. longitude it 

 runs west approximately along the line of 8 S. latitude. South of the boundary a strong current 

 flows west from the waters off the south coast of Java while to the north of the boundary the 

 current flows southeast as mentioned before. 



From January through March, the season when northerly winds prevail, the 

 pattern of the currents changes completely. At this season a current boundary appears running 

 east and west along the Equator; north of this boundary, the currents flow northeast and south 

 of it there is a current flowing southeast along the shores of Sumatra. The current north of the 

 Equator turns westward in the vicinity of the northern extremity of this sea area around 5 N. 

 latitude and joins the current flowing south along the Nicobar Islands. Another conspicuous 

 current boundary appears around the southern limits of this sea area. This boundary runs ap- 

 proximately east and west in the vicinity of 8 to 1 S. latitude, and on its south side the cold 

 current flowing up the west coast of Australia turns to the westward. Because of this current, 

 the current flowing southeast along the west coast of Sumatra is pressed against the coast of 

 Java, forming a narrow but strong flow to the eastward. During the season of northeasterly 

 winds, as remarked earlier, this sea area is cut off from adjacent waters by conspicuous 

 current boundaries at its north in the vicinity of 5 N. latitude and to the south in the vicinity of 

 8 S. latitude. There is another current boundary at about the center of the area near the 

 Equator. The line of this boundary runs east Eind west along the Equator, turning to the south- 

 west in the vicinity of 98 E. longitude. Accordingly, this sea area is divided into a number of 

 parts having currents of different character. 



These various currents appear to be rather strong, and according to the reports of 

 the Haruna Maru, speeds of 2 to 3 knots were frequently measured. 



45 



