From July to September, the season in which the southerly winds predominate, there 

 is a strong current flowing to the southwestward across the central part of this sea area from 

 the strait between Sangi Island and Mindanao at the eastern end of the area. After flowing across 

 this sea area, this current passes into the Flores Sea by way of the Strait of Macassar. This is 

 a current of considerable force, but its strength is said to be affected by the tide. There is 

 another weaker current flowing along the northern coast of Celebes in a direction generally oppo- 

 site that of the current already mentioned. Another weak current appears in the northern part 

 of the area flowing northward along the coast of Mindanao into the Sulu Sea. There is a weak 

 current flowing in the opposite direction to this southward along the coast of Borneo into the Sulu 

 Sea. Consequently, taking this sea area as a whole, it can be considered that there is a strong 

 current flowing across the central portion from northeast to southwest, with other currents flow- 

 ing generally in a counterclockwise direction around the edges. 



As for water temperatures, they are 28 C. to 29 C. in the surface layer, and 27 C. 

 to 29 C. at 50 meters. The water temperature at the 100-meter level differs nnarkedly from one 

 place to another, ranging from 21 C. to 26 C. with an average value of about 24 C. Water 

 color is most often I to II on the Forel scale and transparency is high, 25 to 40 meters having 

 been recorded. 



From January through March, the season when the northerly winds are strongest, 

 the current which flowed from northeast to southwest through the central portion of the area 

 during the season of southwesterly winds is remarkably reduced in strength and it beconnes im- 

 possible to find any conspicuous current throughout the area. Only the current flowing south 

 along the island of Borneo from the Sulu Sea increases somewhat in strength. 



Surface water temperature is 27 C. to 28 C. , a drop of about 1 as compared to the 

 season of southwesterlies. The 50-meter level, on the contrary, has temperatures about 1 

 higher and consequently shows temperatures somewhat higher than those of the surface water. 

 Water tennperatures at 100 meters are also in general slightly higher than during the southwest- 

 erlies, with values of 24 C. to -26 C. In some localities a rather pronounced thermocline 

 appears sometimes in the vicinity of the 100-meter level. The color of the water in the central 

 portion is generally I on Forel's scale with the frequency of II to III increasing toward the bor- 

 ders of the area. Consequently transparency is high in the central portion with values of around 

 30 meters, and with smailler values on the edges of the area. 



During this season of northerly winds rather strong winds sometimes blow 

 continuously, but it appears they would not be sufficient to interfere with operations. During the 

 season of southerly winds the sea is generally extremely calm. 



This sea area had already been developed as a fishing ground before the war. Some of 

 the large fishing vessels based at Takao in Formosa occasionally operated in this area. Boats 

 of the Borneo Fishing Company (operated by Japanese) based at Shamil Island in British North 

 Borneo and of the Filipino- Japanese Sea Food Corporation based at Zamboanga were active in the 

 area. The boats based at TaJcao were all longliners, but the others fished mainly with pole and 

 line for skipjack and small yellowfin. Investigations have been carried on in this sea area by the 

 ShBnan Maru and the Takao Maru (research vessel of the former Takao Province). The mother- 

 ship-type tuna fleet of the Tobu Suisan Company also operated experimentally in this area. An 

 exploratory fleet from Kagoshinna Prefecture also fished in this area with the objective of devel- 

 oping the skipjack pole and line fishery. The following table summarizes the data from these 

 investigations. 



For most of the data there are no records broken down by species so the catch rates 

 for each species are not known. In the cases where such data are recorded, it appears that the 

 catch of bigeye tuna is extraordinarily small. However, spearfishes (mainly white marlin) are 

 extremely abundant, the catch rates averaging 2. 37. Whether these high spearfish catch rates 

 represent normal conditions in this sea area or whether they are a phenomenon which appears 

 only at certain seasons cannot be determined because of the paucity of data. At any rate it is 



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