This supposition means that the 

 course of the migration differs annu- 

 ally, even in the case of the definite 

 age group, and they do, or do not, 

 nnigrate to the North Pacific Area. 



5) If these sizes corresponding to the 

 modes indicate the age groups respectively, 

 there is a close relation between the present 

 data and the growth-rate given by Aikawa and 

 Kato. 



6) Fig. 3 shows that the tendency of the 

 variation of the curves of the length composi- 

 tion of the big-eyed tuna is quite similar to 

 that of the albacore. Therefore, the hypothe- 

 ses mentioned above are considered to be 

 equally established as tenable for the big-eyed 

 tuna. 



7) These phenomena may be explained in 

 more detail by further research, but it is 

 thought to be sure that the phenomena will 

 contain many important problems relevant to 

 ecology or studies of the stocks of these fishes. 



/end of English summary;/ 



The size composition of pole-and-line- 

 caught albacore landed at the Misaki Fish 

 Market has already been reported upon by Uno 

 (1936a, b), but nothing has been reported on 

 the longline catch. The present paper is a re- 

 port of measurements by the authors of alba- 

 core and bigeye tuna taken on longlines in the 

 North Pacific fishing grounds in the autumn 

 and winter. 



1. Materials 



The data were collected in two periods, 

 the first from November 1948 to March 1949 

 and the second from October 1949 to March 

 1950. The numbers of vessels covered and 

 the numbers of fish measured by nnonths are 

 shown in table 1, 



When the operations of a vessel have ex- 

 tended into two nnonths, they have been classi- 

 fied under the month in which the majority of 

 the fish were taken, as based on their reports 

 of their fishing. The measurement taken was 

 the so-called forklength, and the measurements 

 were grouped by classes of 2 cm. in the case 

 of the albacore and 4 cm. for bigeye. No defi- 

 nite rule was set up for the selection of vessels 

 or of fish, but ^s many nneasurements were 

 nnade as conditions permitted. The North 

 Pacific fishing grounds referred to in this paper 

 include the area north of 26 N. latitude between 

 130°E. and 170°W. longitude. 



2. Size composition by species 



A. Albacore, Thunnus germo (Lacepede) 



In figure 1 the size compositions 

 for the two periods referred to above, 

 November 1948 to March 1949, and 

 October 1949 to March 1950, are shown 

 as percentages. As is clear from the 

 figure, the size ranges in the landings 

 are in very good agreement, both 

 groups being principally composed of 

 fish from 60 to 110 cnn. in length. To 



Table 1. --Number of ships and fish sannpled by month 



