6. Dotabuka, Carcharinus brachyurus (Gunther) 



This shark will grow to a length of about E - 2. 5 meters. The first dorsal fin is 

 notably small and is located mid-way between the snout and the caudad peduncle. The second 

 dorsal fin is smaller than the second anal fin and is located diametric 2illy opposite it. The snout 

 is blunt. This is one of the species of sharks commonly seen in warm seas. 



7. Yashibuka, Carcharinus sp. (gangeticus ?) 



This shark resembles the preceding one but can easily be distinguished by its re- 

 markably large first dorsal fin. This fin is the best for making dried shark fins used in Chinese 

 cooking and is of high value. This species is abundant in warm seas. They are particularly nu- 

 merous in the waters east of Formosa in February and March. 



8. Mejirozame, Carcharinus japonicus (Temminck and Schlegel) 



Characteristics peculiar to this species are the small eyes and gill openings. They 

 are said to be very abundant in Japanese waters, but it is doubtful whether all the sharks to which 

 the name mejirozame is applied are of the same species. It is thought that there is need for 

 further study on this point. 



9. Tsumaguro, Carcharinus melanopterus (Quoy and Gcdmard) 



Particularly outstanding characteristics of this shark are the intensely black tips 

 and edges of all the fins. It attains a length of 2 - 2. 5 meters. As it is abundant in southern 

 seas, it is taken in rather large qucintities. These sharks appear to be particularly numerous 

 in the South China Sea area. 



10. Tsumajiro , Carcharinus albimarginatus (Riippell) 



This species is distinguished by the white tips and edges on all of its fins. It does 

 not grow very large, the maximum size being about 2 meters long juid 30 kilograms in weight. 

 This species is very commonly seen in warm seas. There is another separate species called 

 the yogorebuka or baka, but it is not yet well known biologically. In this species the tip of each 

 fin has cloud-like irregulctr white spots. 



11. Shumokuzanne , Sphyrna zygaena (Linnaeus) 



The head is in the form of a wooden mallet with the eyes on the tips. In western 

 Japan it is generally called kasebuka or kase . One species occurs in Japanese waters, but three 

 species have been reported from the south. It is wondered whether those occurring in Japanese 

 waters should not also be separated into three distinct species. 



V. Fishing Grounds 



As has been stated earlier, the fishine grounds of the tuna longline fishery are lo- 

 cated within the area from the Equator to about 40 to 45 N. latitude in the open sea and in 

 coastal waters facing on warm currents. We do not as yet have adequate data concerning the 

 situation in the Southern Hemisphere and therefore know little about it, but it may naturally be 

 supposed not to be greatly different fronn that of the Northern Hennisphere. The occurrence of 

 many species of tuna ajid spearfish has been reported fronn Australia and the New Guinea area. 

 It appears that recently tuna fisheries are being developed in that region. 



Until recent years tuna fishing grounds were limited to coastal waters and to the vi- 

 cinity of islands and shoals (enninences in the sea floor) scattered throughout the open sea. This 



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