If we combine the data appearing in table 9j, a - dj, we see 

 that in the Celebes Sea the depth at which tuna are taken in the 

 greatest numbers is about 100 meterso The spearfishes are shown to 

 be in general most numerous at shallower levels. This situation 

 seems to agree in the main with that encountered in the area east 

 of Formosa,, The tunas are lumped together and nothing is known 

 of the catch of each species, but it is certain that most of them 

 were yellowfino According to part d_ of table 9^, in the Celebes Sea 

 there was a catch rate for yellov/fin of as much as Q% even on branch 

 lines extending as deep as 160 meters,. This fact shows that there 

 is a possibility that^ at least in tropical waters, the vertical 

 distribution of yellowfin goes far deeper than has been believed 

 hithertoo At the same time this gives an important indication for 

 the consideration of the tuna fishery resources of the tropioso 



Table d_ alone differs somewhat from a - c^, with the maximum 

 catch rates for both tunas and spearfishes on the 76-meter brancheso 

 This is thought to be principally caused by differences m oceano- 

 graphic conditionso The Celebes Sea is homogeneous in character 

 and clearly stratified, but oceanographic conditions in the East 

 Celebes Sea are extraordinarily confused and the curves of vertical 

 distribution of water temperatures show several remarkable rises 

 and falls between 60-70 meters and 200 meters. In the Celebes Sea 

 area the water temperatures at 100 meters are in the range of about 

 24° - 26P Co , while at the 160-meter level they are within the 

 range of 18° - 22° Co 



In addition to the above, there are also some data from the 

 East Philippine Sea, the northern part of the South China Sea, and, 

 farther south, from the Banda Sea, the Flores Sea, and the vicinity 

 of Sunda Strait^ but in general they show the same tendencies that 

 appear in tables 8 and 9c Accordingly, it is considered that the 

 construction of longlines for yellowfin tuna in southern waters 

 should be planned so that the hooks will hang at about the 100- 

 meter level in order to maximise the catch ratOo 



With regard to fishing grounds in Japanese waters some data 

 have been reported by the Chiba Prefecture Fisheries Experiment 

 Station and others , but on the whole the data are scanty and cannot 

 be considered accurate enough for the planning of fishing gear, so 

 they are omitted hereo 



From a consideration of the data presented above it is clear 

 that in order to make the operation of a tuna long line fishery 

 profitable, it is not enough simply to find out the horizontal 

 distribution and paths of migration of the fisho Unless a firm 

 grasp is had of both the horizontal and vertical distribution^ the 

 former in order to avoid errors in the selection of fishing grounds, 

 and the latter in order to plan the most suitable construction of 

 gear for the area fished, it can hardly be said that enough has 



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