Summary 



The albacore longllne fishing grounds 

 which are formed in the North Pacific Ocean 

 every year in Novennber continue moving 

 southward until March of the next year. The 

 author has attempted to analyze the size com- 

 position of albacore landed from these fishing 

 grounds by fitting normal distributions to the 

 size composition. The results are shown in 

 figure 2. These may be summarized as 

 follows: 



1. Six size groups appear each year. If 

 we postulate that there are mutual correspond- 

 ences among the six groups, the positions of 

 the modes are approximately 57 cm. , 67 cm. , 

 78 cm., 89 cm., 100 cm., and 111 cm., with 

 approximately equal intervals between the size 

 groups. 



2. The size groups which appear in the 

 greatest numbers are those which have their 

 modal length in the vicinity of 78 cm. and 89 

 cm. , these two groups alternating in predom- 

 inance every other year. 



Through an examination of these results 

 the following may be said: 



1. A comparison was made with the 

 results of age determinations made by Uno, 

 and for groups II-IV it can neither be denied 

 nor affirmed that there is agreement between 

 the two sets of results. However, the absolute 

 values of the discrepancies are very small. 



2. It is pointed out that there is a 

 possibility that the separation of the advanced 

 age group is erroneous. Consequently, it is 

 thought that if the division into groups of the 

 albacore taken by longlines in the North Pacif- 

 ic is carried out as shown in figure 4, there 

 is no great obstacle to handling them as age 

 groups. 



Albacore Studies. II. Size Composition of the 



Albacore Teiken in the North Pacific During 



the Period of Northward Movement* 



By 



Akira Suda 

 Nankai Regional Fisheries Research 

 Laboratory 



/English title and summary/ 



Studies on the Albacore - U. Size Connposition 



in the North Pacific Ground during the Period 



of it's Northward Migration 



The area of the Kuroshio current or the 

 North Pacific current is known as the quite 

 excellent fishing ground of the Albacore. 

 Albacore in this ground migrates southward 

 during Autumn and early Spring, and is mainly 

 caught by long-line. From Spring to Summer 

 it migrates northward and is caught by rod and 

 line with live bait. As to the former catch the 

 author already reported it's size-composition 

 (Suda 1954a). In the present, the author reports 

 the analysis of the size-composition of the 

 latter. The principal informations obtained by 

 this work are as follows. 



(1) Though the range of the size is 

 confined within the limit between 50 to 100 

 cnn during the seasons of 1951 and 1954, 

 there are the remarkable annual fluctuations. 



(2) The number of length-groups are not 

 fixed by the seasons. 3 or 5 length-groups 

 appear in each season from 1951 to 1954. 



(3) The modal length of each length- 

 group shows remarkable annual fluctuation. 

 (Table 1) 



(4) The relative abundance of each length- 

 group is very unstable as shown in Table 2. 

 In most cases, the nnost dominant length- 

 group occupies the overwhelming proportion. 



Such a size-composition of the northward 

 migrating Albacore differs from that of south- 

 ward migrating one as follows. 



♦ Published in 1955 in the Bulletin of the 

 Japanese Society of Scientific Fisheries 21(5): 

 314-319. Contribution No. 66 of the Nankai 

 Regional Fisheries Research Laboratory. 



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