Table 6. --Regular station observations at Garanbi (1935) 



Among the foregoing oceanographic data, the figures for the line from Suo toYonakuni 

 Island are averages for the past 12 years. In general, the waters east of Taiwan ordinarily 

 show high specific gravities in the winter and low specific gravities in the summer, but the 

 changes are not regular as they are in the case of the changes in water temperature. The spear- 

 fishes are said to swim in comparatively shallow layers of the sea, and the construction of the 

 air bladder is suitable for this. At Hokasho there is comparatively little influence from the 

 mainland so that the water temperatures and specific gravities observed there should not differ 

 greatly from those of the waters farther off shore. It must be said that on the basis of these 

 oceanographic data it is difficult to give an accurate explanation of the presence of the spear- 

 fishes during half the year in the waters east of Formosa. Consequently, it is difficult to explain 

 the migrations of the spearfishes in terms of the direct effect of seasonal changes. 



As will be set forth in a later section, it is clear that, except in the case of the sailfish 

 and the shortnosed spearfish, the spearfishes which migrate into Formosan waters do not do so 

 with the objective of spawning. 



It being thus difficult to account for the migration of spearfishes in Formosan waters as 

 being controlled by spawning or seasonal changes, it is necessary to consider some other cause. 

 This cause, which, of course, will be subject either directly or indirectly to seasonal effects, 

 is that at this season in this area the fishes upon which the spearfish feed are present in abun- 

 dance. From October to March great schools of scad and mackerel are scattered through the 

 waters east of Taiwan. The mackerel in particular fornn a great concentration from the Suo bcmks 

 to the Kisanto region, and during the peak season of February and March they are taken in very 

 large quantities by longline boats based at Suo, the catch for one day not infrequently exceeding 

 100,000 fish. According to the statistics for 1934, the yearly catch amounted to 2,477,600 kin 

 with a value of 115,459 yen . These mackerel are not only in themselves an important objective 

 of a fishery, but they are also utilized as bait for the longline fishery, and it is thought that they 

 also play cin importsmt role in keeping the spearfishes in this sea area over a long period of time. 

 It is known that if we investigate the stomach contents of the spearfishes taken during this fishing 

 season, they are almost completely made up of mackerel (see plate 10). 



The species which have been known to occur around this island since ancient tinnes are the 

 sailfish, white marlin, black marlin, and striped marlin, and the broadbill swordfish, little 

 having been known about the distribution of the shortnosed spearfish. It was in 1935 that it became 

 known that the shortnosed spearfish also occurs in the vicinity of this island. In investigations 

 carried on in that year from October to December by the research vessel Sbonan Maru of the 

 Taiwan Government-General, two shortnosed spearfish were taken in the waters east of the island. 

 It thus became clear that this species also occurs in Formosan waters. Investigation was made 

 to find out whether they were ever landed in the various markets, and it turned out that they were 



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