it WAS ascertained that the black tuna also occurs in the waters 

 of Formosa and the Philippine So 



The schools which inigrate into Formosan and Philippine 

 waters are markedly larger than those which appear in southern 

 KyiTshu' in the winter » and it is believed that they belong to a 

 different age groupt. The spawning season in this area is 

 thought to be about 2 months earlier than that in Japan or from 

 the middle of April to the middle of May„ The author has 

 obtained completely ripened ovaries from northwest of Lingayen 

 Gulf in the middle of Mayo Many well-ripened ovaries and testes 

 have also been collected from northeast of Luzon in Mayo 



Since the time when Dr, Kishinouye made the above-quoted 

 remarks it has been completely unknown whether or not the black 

 tuna spawns in the waters of the Formosanand Philippine areas„ 

 In recent years migration of black tuna into the waters adjacent 

 to Tanegashima has almost ceased, but there appears to have 

 been little change in the occurrence of juvenile fish in late 

 summer and early fallo If it is assumed that there have always 

 been in the past migrations into the Formosan and Luzon areasp 

 and that spawning has taken place there, Dro Kishinouye 's 

 doubts, as quoted above, can probably be easily resolvedo 



Dro Kishinouye felt some doubt concerning the proposition 

 that in the waters adjacent to Japan the juvenile fish appear 

 to the south of the waters in which spawning takes place, and 

 wrote that he found it hard to believe that the juvenile fish 

 migrated down from the north, If, however, it is assumed that 

 these fish also spawn in the Formosan and Philippine areas, 

 considering the pattern of the ocean currents there is nothing 

 at all strange_in the appearance of the juvenile fish off 

 southern Kyushu » 



As will be explained later in the section on the spawning 

 habits of the spearfishes, the spawning of these fishes extends 

 over an extraordinarily long period, and is carried on over a 

 wide area of ocean, it is believedo We say that it extends 

 over a long period of time, but this applies to the organized 

 schools in general and does not mean that the spawning of one 

 individual lasts over a long periodo As Dro Kishinouye has 

 also explained, the schools are made up of individuals having 

 their gonads in various stages of ripenesSj, and it is thought 

 that they carry on their reproductive activities successively 

 beginning with the ripest„ Spa-w.Tiing habits of this sort are 

 peculiar to these fishes, and are considered to have an impor- 

 tant significance in determining the character of the stock and 

 the fisheryo 



The ova in ripe black tuna ovaries are 0o85 mmo in diameter. 

 The eggs as a whole are clear and almost colorless with one oil 

 globule of a rather deep yellow coloro Around the oil globule 



14 



