Sulu Sea, but it gradually extends over the whole area and fishing becomes 

 good from the vicinity of Dangerous Ground to the Annam area. 



The greater part of the catch is yellowfin, making up 90 per cent of 

 the tuna and spearfish taken. There are few big-eyed tuna, and albaccre 

 appear only in the northeastern part of this area. All of the species of 

 spearfish are found, but M. marlina, M. mazara, and M. mitsukurii are most 

 abundant. 



From the middle of March to May active migration of spearfishes is 

 seen from the waters off Annam to the Hainan I. area. The main species 

 is M. marlina . The sailfish is most abundant in the summer, just as it 

 is on the Pacific side. 



From the middle of March to the first part of June the black tuna 

 appear in the northeastern part of this area and the fishery for them 

 becomes active at the same time that it does in the Pacific northeast of 

 Luzon. 



The area under the South Seas Government-General will be discussed 

 later. 



In what follows I will attempt a brief outline of the distribution of 

 a number of the important species. 



(a) maguro / black tuna, T. orientalis / 



According to Dr. Kishinouye, the southern limit of the distribution 

 of this species is around 32°N and it does not occur in the Ryukyus, 

 Ogasawaras, and Taiwan. Its northern limit is given as approximately 

 46°N, and its range of distribution with regard to water temprature is 

 5 - 20'-'C, with 15°C the optimum. It likes lower temperatures than any 

 other species of tuna„ Fish which are in the vicinity of 32°N begin 

 their gradual northward movement in the spring, a part of them going 

 through the Tsushima Strait into the Sea of Japan while the majority 

 migrate along the Pacific coast. In the course of this migration the fish 

 come in very close to the coast. In the autumn they move south again, 

 but their course is thought probably to lie through the offshore waters. 



It was in 1935 that it became clear that this species also occurs in 

 Formosan waters, and in that year 50,000 yen worth of these fish were 

 landed. Thereafter the catch increased from year to year, and in recent 

 years it has amounted to more than one million yen. Ordinarily the first 

 catches are made in the middle of March, and the peak is reached in April 

 and May. In the early part of June many of the fish are seen leaping on 

 the surface, and thereafter they suddenly disappear. In normal years 

 the first catch is made in the vicinity of the 100-fathom line in the 

 northern part of the South China Sea, the fishing grounds rapidly extend 

 over all of the northern part of the South China Sea, through the Bashi 

 Strait, and into the Pacific northeast of Luzon, and at the end of the 

 season fish are taken even in the vicinity of Yonakuni I, These fish 

 appear suddenly and disappear suddenly, and at present their migratory 

 routes are completely unknown, 



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