142 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



AGE GROUP 



250 



200 



w 150 



Q 



■z. 



o 



a. 



; 100 



UJ 



50 



10 



N-m- 



15 



20 



25 



N-It- 



30 35 40 



MONTHS 



N-L— L 



45 



50 



N - 



MODAL GROUPS 



55 



N+I 



60 



G5 



70 



N+tt 



Figure 9. — Growth curve of yellowfin tuna taken in Hawaiian waters fitted to lengths and transformed into terms 



of weight. Actual modal values in weight are superimposed. 



150 I- 



u 100 



50 



AGE GROUP 

 I 1 



18 24 



MONTHS 



30 



36 



42 



Figure 10. — Lengths of dominant size groups of yellowfin 

 taken in waters off Central America by Schaefer (1948) 

 plotted against calculated growth curve of Hawaiian 

 yellowfin. 



Schaefer that the 60-cin. fish probably are 1 year 

 old and the 85-cm. fish a year older is also in close 

 agreement. 



Our growth curve indicates that the yellowfin 

 tuna grows rapidly during at least the earher years 

 of life. Group N demonstrates a gain in weight 

 of approximately 60 pounds in 1 year. Aikawa 

 and Kato (1938) and Kimura (1932) have studied 

 age and growth of the yellowfin tuna in Japanese 

 waters. Aikawa and Kato assigned ages by the 

 study of marks on vertebral centra which they 

 considered to be annuli. The resulting age-weight 

 relation is shown in figure 11. In plotting these 

 data, which are from table 3, it was assumed that 

 the ma.ximum values were representative of the 

 end of the year of life because the length and 

 weight values for age group O were maximum 

 values. As the month of June has been used in 

 our study as being the approximate center of the 



