factor was 2J4. (Table 13). Prom this the length and weight ranges and growth 

 rates for each age group can be found, (Tabic 12), 



Uno (^»2) found that of the three groups comprised in the catch of albacore 

 from the waters east of Cape Nojima, those having an average length of 79.15 ± 

 1.30 cm were fi.f th-year fish (IV age group), those averaging 79.15*3.68 cm were 

 sixth-year fish (V age group), and those averaging 89.55*2.25 cm, were seventh- 

 year fish (VI age group),, From the results of his second survey ^2) he found 

 that the fiith-year fish averaged 69,0iiil.98, the sixth-year fish 81.56±3.82, 

 and the seventh-year fish 89.70±1,98 cm. The average lengths correspond to the 

 length rsnges which the author has established for fifth-year to seventh-year 

 fish. The albacore differ from the black tuna and the yellowfin in that the 

 weights of the middle-aged fish show the highest values in the range. 



In the fish taken from these same waters (28° - VP N, 170® - 173'' E) ftron 

 January to May of 1937 length groups could be detected which had their modes at 

 25 cm, 4.5 cm, 56 cm, 62 cm, 7A cm, and 83 cm (Figure 7 lower). These corres- 

 pond respectively to age classes from fish of the year to sixth-year fish. 

 There is another group between 90-100 cm which is thou^t to consist of seventh^ 

 year fish, but the mode is not clear. In the catch for 1936 (Figure 7 upper) 

 there are weight groups having their modes at 0.6 kan . 1.6 ^m. 2^,1 ten, and 

 3.7 k;an. and they are thought to belong to the second-year and fourth- to sixth- 

 year classes. 



Thus the length and weight groups found in the catch correspond with the 

 length and weight ranges established by means of the vertebrae and more or 

 less guarantee the coirectness of the determinations. 



Technician Shitoku Era of the Shizuoka Prefectural Fisheries Experiment 

 Station has been able to make a good-quality canned product from albacore of 

 over 2.5 kan in weight, but fish under that weight are not suitable. This 

 means that fish in their sixth-year and older are best suited for canning, 



IV, Skipjack Katsuwonus vagans (Lesson) 



Twenty skipjack taken off Palao August U, 1937 were received from Dr, 

 ShSkichi Yamamoto. Age determinations were made on these fish along with other 

 specimens from the Northeastern area. 



Measurements were made of the annual rings in the first five vertebrae of 

 the skipjack. (Table lU), The correlation between the total radius (T mm) of 

 the centrum and the body length (L cm) is shown by the formula Lj/lg a (Tx*** 

 0.53)/(T2*'0»53). (Figure 8). The body length (L cm) at which Ring No. n was 

 completed can be found from the radius (r^ mm) by the following formula. 



lift a 7*1 T^U 



Aikawa^^' made age determinations on 20 skipjack from Zunan Is. waters and 

 got a correlation between total radius of centrum (T mm) and body length (L cm) 

 of Li/lg - (Tifl.54)/(T24l,54^), and for finding from the radius of ring n the 

 length at which the ring was completed he used the formula 



Lft 3 6.2frn 5.5 



U;Uno, Michlo} Bull. Jap, See. Sei. Fish. 4(5), 1936 

 pJUno, Michio; Bull. J4p» Soo. Sci. Pish. 5U)* 1936 

 (3)Alka«a, Uiroaki; Bull. Jap. Soc. Soi, Fish. 6(1), 1937 



10 



