GROWTH OF BLUEFIN TUNA 



49 



Wiilford (1946) transformation of our data. As 

 we found it possible to read only a small percent- 

 age of the material available for ages beyond 10 

 years, we luive drawn the curve to that point only. 

 Average sizes at mid-summer for bluefin tuna of 

 ages 0-1 as indicated by this curve are listed in 

 table 7. 



3 40- 



FiGURE 14. — Average length.s of bluefin tuna by age 

 groups as indicated in figures 4 to 11. Curves were fitted 

 empirically. The numbers of fish in the samples for 

 all years combined are indicated. Samples consisting 

 of less than 5 fish were not shown. 



CONCLUSIONS 



Our results through the fifth summer of life for 

 bluefin tuna taken off New England are substan- 

 tially in agreement with those of Westman and 

 Neville (1942) for fish taken off Long Island. 

 Our study of the growth of these young tunas, 

 however, was based on a nmch larger sample, 



NEW JERSEY- C»«*E COO 

 MARVLAND-CAROLINAS 

 MIAUI AflEA 

 GULF OF UEIICO 



I AUGUST [sEPTEweml oc'obew | tovcwetHf ptcExatw I .lainjaB* \ 



30 £ 



-25 I 



Z 

 Ul 



- 20 o 



I 



o 

 5 



Figure 15. — Lengths of bluefin tuna less than 20 inches 

 long (young of the year), from table 4. The curve of 

 estimated growth was fitted by inspection. 



AGES AND SEASONS 



„, 4 „,. 



iO - 



 1  li i2 ; li i 3; Ij ; 4:1! 



MONTHS ANO YEARS 



Figure 16. — Estimated growth of young bluefin tuna. 

 Broken lines indicate estimated lengths in periods for 

 which data are lacking. The upper scale shows ages 

 and seasons as assumed in the text, and the lower scale 

 shows ages assuming that hatching occurs at mid- May. 



and the sampling was spread over several years 

 rather than 1 year. Differences in growth be- 

 tween year classes were found to be slight and the 

 results of the analysis of the composite sample 

 are believed to approximate the average encount- 

 ered in nature. Although it was not possible to 

 fully verify the readings of annuli for older fish 

 by the analysis of size frequencies, and difficulties 

 in reading the annuli increased with their number, 

 we have exlendcd our (let(>rminations to consider- 

 ably older ages than lias previously been done for 

 western Atlantic bluefin tuna. 



