Synopsis [in English] 



On the basis of rifigs formed on the surface oi centrum of vertebrae, ages 

 of tunny, yellow-finned tunny, long-finned albacDre, and bonito were deter- 

 mined as follows. 



(1) Tunny - ITiunnus orientalis (T» 4 S. ) : L„(cm)-7o9^ rn(mm) - 4,8, where 

 risA.l, r2s6.A, Ty^B,^, r^»12.6, r^zl^.f^, r^sig.A, Tjz22,U, rg=25o4, and 

 rgs28cO. 



(2) Yellow- finned tunny - Neothunnus macropterus (T. & S. ) : Ln=^o^ ^n " 

 8.4., where t^-^.(>, t^zJ-^* T-^sB.Ut r.sll.A, and r5-13.6. 



(3) Long-finned albacore - GermS germo (Lac^p^de): L^sS.S rn 17f5, **ere 

 ris3.2, r2=ii.9, r3»6.4, r^s7.9, r5s9.4, r^sll.O, r7rl2.7, and r8rU.2. 



U) Bonito - Katsuwonus vagaHS (lesson): 1^=6.15 r^fS-S, where rj^=3.2. 



r2s4.5, r3r5.3, r/57.2, rrrB.5, and r6r9,6, 

 Ln is the body length in cm of the n-f 



Lq is the body length in cm of the n-aged fish, when the n-th of the radius 

 r,^ nnn was completed, 



(Translation begins] 



The age of fish was determined by using the vertebrae, just as was done in 

 the case of the bonito (D and chub mackerel V2) . There are many examples of the 

 use of this method to determine the age of fishes, not only in Japan but in 

 various foreign countries as well. With this method, just as when using scales 

 and otoliths, various sorts of critical tests are necessary. The author made 

 determinations of the ages of various species on a broad scale as a preliminary 

 study, and tried to corroborate his tentative results by a consideration of the 

 character of the length and weight groups in the catch. The author hopes to 

 establish this method on a firm basis by testing his results with a further ac- 

 cumulation of data and by a study of the way in which the annual rings are 

 formed in the vertebrae. Deep thanks are offered to i'r. Kinosuke Kimura, who 

 supplied various criticisms and valuable morphometric data for this paper. 



I. Black Tuna Thunnus orientalis (Temrlnck 4 Schlegel) 



Eight small black tuna (Izu Ajiro Fish Market, Table l) and four large 

 black tuna (TokyS riarket) caught on hook and line were obtained and an attempt 

 was made to determine their agos by means of the vertebrae. Five vertebrae 

 from No. 7 to Noo 12 were used. The vertebrae vrere split longitudinally and 

 the total radius of the centrum from the center of the vertebrae to its outer 

 edge (T mm) and the radius of each ring (r mm) were measured. (Table 2). The 

 correlation between these figures and the body length (L cm) was examined. 

 (Figure 1). 



Just as in the bonito, the development of the vertebrae is accompanied by 

 an Increase in body length. The relationship can be shown by Li/l«2 = (r^-O.^S)/ 

 (T2 - 0,4.8). Flrom the radius of n ring (rp mm) the body length at which the 

 ring was completed can be found by the following formulae 



Ln=7.94 rn-4.8 



U) Aikawa, Hiroaki; Bull. Jap. See. Scientific Fisheries 6(1), 1937, 



(2) Aikawa, H.j Bull. Jap See. Scientific Fisheries 6(1), 1937. [In English] 



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