AGE DETERMINATION OF ALBACORE 



359 



cated closer to the center of the centrum than the 

 corresponding annuli in the remaining specimens 

 (60 percent). He therefore considered the 40 

 percent to belong to a different spawning season 

 and discarded them from calculations of growth 

 increments. From the above, it appears that 

 these workers also experienced some difficulty in 

 rigidly adhering to established criteria. 



The fact that we have not been able to repro- 

 duce ring counts with any reasonable consistency 

 does not in itself prove that this method of aging 

 albacore is invalid. There are other points which 

 should also be considered. As stated earlier, no 

 direct evidence has yet been presented to show 

 that the rings on the vertebral centra are "annuli." 

 Furthermore, if we examine the results presented 

 by some of the other workers, we find that the in- 

 crements that are noted do not give either a rea- 

 sonable or consistent pattern of growth. Referring 

 to Aikawa and Kato's results, Brock (1943) stated 

 that "it may be seen that the growth increment 

 from the age of one to that of eight is exactly the 

 same each year, resulting in a growth curve that 

 is absolutely linear. This is totally at variance 

 with what is known of growth curves in general 

 and in all other species of fishes that have been 

 studied. If the number of "age rings" bears this 

 relationship to the length of the fish it is probable 

 that they do not represent annuli and bear no 

 direct relationship to age." Partlo 's results are 

 somewhat similar. In figure 6 we show a plot of 

 body-length at earlier ages as calculated from 5- 

 and 6-year fish ; the data were derived from Partlo 

 (1955: table VIII, p. 57). The calculated lengths 



5 60 

 o 



I 

 I- 



o 



45 



g 30 



AGE 



Figure 6. — Calculated lengths of albacore at earlier ages 

 based on 5- and 6-year fish. (Taken from Partlo, 1955, 

 table VIII.) 



Figure 7. — Mean length at each age of albacore captured 

 off northwestern Spain as reported by Figueras (1955). 

 (Lengths given are total lengths.) 



from ages 1 to 4 based on 5-year fish and the 

 lengths for ages 1 to 5 based on 6-year fish form 

 curves which are almost perfectly linear. The re- 

 sults presented by Figueras are shown in figure 7. 

 Here again, the growth curve is remarkably linear, 

 contrary to the general concept of growth curves. 

 Another consideration is that the various esti- 

 mates do not appear to be consistent with growth 

 as evidenced by tag returns. The information 

 from this source is meager, however, and not much 

 weight should be given it at the present time. A 

 summary of albacore tag recoveries is given in 

 table 2. The 5 tag recoveries which contribute 

 information on growth are shown in figure 8. 



JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR 



Figure 8. — Growth shown by 5 tagged albacore: data 

 presented in table 2. tBody weight, in pounds, in 



parentheses.) 



