For a tuna the higeye has a peculiar pattern of distribution. It shows little change in 

 density with changes in latitude, but appears to be evenly and sparsely distributed all over its 

 range. Like the albacore it does not appear to enter the coastal waters and tends to become more 

 numerous as one goes offshore. It is said that the level at which it swims differs from day to 

 night and that it shows a conspicuous tendency to swim at deep levels during the day and to appear 

 at tlie surface during the night. 



Among the tunas the yellowfin is the one which most belongs to the waters of the low 

 latitudes, its density of distribution being high in an area centered along the Equator. At some 

 seasons it appears also in the waters of rather high latitudes, but these seasons are short. In 

 general it lives offshore, but it also enters enclosed bodies of water. It is taken, although rarely, 

 in the Japan Sea. As a young fish, when it is called kimeji, it enters the coastal waters and is 

 not rarely taken in fixed gear. 



Differences in the distribution of the various species of spearfishes can also be de- 

 tected. Excepting the broadbill, it appears that the other species on the whole prefer higher 

 temperatures than do the tunas, and the greater part of the catch is made in water temperatures 

 of 20 - 28 C. Except for the broadbill, all the other species in general appear to have more or 

 less of a tendency to be more abundant in coastal water areas, so that the catch seems to be 

 greater in the vicinity of islands. The broadbill has a wide range of distribution, and in Japanese 

 waters its catch pattern to some extent resembles that of the albacore. However, it is scarce in 

 the very far offshore areas frequented by the albacore. In the white marlin and the sailfish the 

 the coastal character is particularly strong and they are most abundant from the 100 fathom line 

 of the continental shelf to Taiwan and the shores of the Philippines. The striped marlin is most 

 abundant in the subtropical central Pacific and its distribution extends to the vicinity of 40 N. 

 latitude. The black marlin is abundant in the Equatorial Countercurrent and the North Equatorial 

 Current. It migrates to the north, but its range of distribution appears to be more restricted to 

 wariTi seas than that of the striped marlin. 



As stated above, the distributional pattern of these species appears to vary mainly 

 from north to south. This phenomenon is thought to indicate that temperature bears an important 

 relationship to the distribution of these fishes. Nevertlieless , the range of temperatures which 

 these fish can withstand is, as indicated above, rather broad. In the past these fish were taken 

 as representative of the so-called stenothermal fishes, however, they can be thought of as not 

 necessarily stenotherinal but as rather eurytherinal. 



As has already been said, temperature bears a very important relationship to the 

 distribution and migration of these fishes. However, the range of temperature change which they 

 can endure is rather great and in sea areas which are within tliat range there is a possibility 

 solely from the standpoint of temperature of the occurrence of these fishes. Water temperatures 

 which limit the possibility of occurrence of these species can become a controlling factor as re- 

 gards fishing grounds and fishing seasons, but in waters where the temperatures are favorable 

 for their occurrence at all times we can hardly think that temperature has a controlling influence 

 on the establishment of fishing seasons and fishing grounds. It goes without saying that the re- 

 sources of the oceans are in the last analysis controlled by the chemical characteristics of their 

 waters and the energy of the sun. But it need hardly be said that these fishes, which are living 

 things, have the instinct for self-preservation and the instinct for the preservation of the species, 

 and they act in accordance with these objectives. Studies in this field have advanced so extremely 

 little that we unfortunately have no data on which to base a discussion of the relationship between 

 the distribution and migrations of the tunas and their ecology and physiology. 



When it comes to the problem of fishing grounds, the biological distribution and the 

 potentiality of distribution are naturally different. In order that a body of water may have sig- 

 nificance as a fishing ground, it is essential that fishing operations be actually carried on in those 

 waters and that the catch be at least such as to pay the expenses of the fishermen. 



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