AGE AND GROWTH OF YELLOWFIN TUNA 



143 



AGE GROUP 



Figure 11. — Growth in weight plotted against age for 

 Hawaiian yellowfin as compared to growth curves 

 calculated by Aikawa and Kate (1938) and Kimura 

 (1932). 



spawning period, the maximum values as given by 

 Aikawa and Kato have been plotted for the 

 month of June, the assumed last month for any 

 age group. Regardless of the month of the year 

 these values are plotted against, the valu's for 

 any given age group differ greatly from the values 

 resultin£,- from our study of the Hawaiian yellowfin. 



T,\BLE 3. — Age, length, and weight range of yellowfin 

 tuna from Japanese waters, from Aikaioa and Kato 

 (1938) 



The results of Kimura's (1932) age-weight study 

 also are shown in figure 11. This study is based 

 on a few specimens taken over a long period with 

 no defined method of determining modal values 

 in frequency distributions. The presentation of 

 Kimura's data is based on values of weight taken 

 directly from his growth curve shown in figure 12. 

 Values were converted to pounds for comparison 

 with our data. This growth curve demonstrates 

 more rapid growth than the curve of Aikawa and 

 Kato hut still does not agree with the present 

 Hawaiian study. 



Figure 13 gives growth curves of other species 



of tuna taken from various areas in the world 

 compared to the growth curve of Hawaiian yellow- 

 fin. We have plotted these from the published 

 data. This graph shows no other tunas as having 

 a growth rate as rapid as that of the yellowfin tuna 

 of Hawaiian waters. The curve of bluefin tuna 

 of the Mediterranean Sea (Sella 1929) is based on 

 more than 1,500 vertebrae samples. This growth 

 curve, like the growth curve of yellowfin based on 

 vertebra-centra analysis (Aikawa and Kato 1938), 

 shows a very slow growth rate and infers a very 

 long-hved fish, for most of the plotted data are 

 below the point of inflection. 



BODY WEIGHT 

 KG. 



50 



20 



I a m IS T Tcr 



AGE GROUP 



FiatjRF. 12. — Growth curve of yellowfin tuna in Japanese 

 waters from Kimura (1932). Circles show average 

 weight of a large number of fish of roughly equal 

 weight taken at one time. Solid dots are weights of 

 single fish. 



Aikawa and Kato (1938), in addition to their 

 study of the yellowfin, determined ages and growth 

 of the black tuna {Thunnus orientalis), the bonito 

 or skipjack {Katsuwonus vagans), and the albacore 

 (Germo germo) by vertebral-centra analysis. Be- 

 cause the skipjack and albacore are smaller species 

 of tuna not comparable to the yellowfin, they have" 

 not been included in the graph. The growth 

 curve of the black tuna, a species more comparable 

 in size, indicates a more rapid growth rate but the 

 curve has only the slightest suggestion of an in- 

 flection point. The growth curve of bluefin tuna 

 (bl^ck tuna of Aikawa and Kato, Thunnus orien- 

 talis) by Kimura (1932) from weight frequencies 



