Albacore— Otsu 
263 
method, several workers have analyzed albacore 
size frequencies. Brock (1943) found two reg- 
ularly occurring modal groups in the California 
length frequencies for the years 1924 to 1928 
inclusive. The consistency in the appearance of 
these groups indicated that they were year 
classes. A more uniform relation was seen in 
the "lagged difference,” or the difference in the 
modal size of group A in 1 year with that of 
group B in the following year, rather than be- 
tween the two modal groups of the same year. 
The- modal lengths ( lagged ) of both California 
and Oregon albacore are reproduced in Table 4. 
The lagged modal values for the California 
albacore fall in nearly perfect agreement with 
the growth shown by the tagged fish, indicating 
that the distinctly bimodal distribution rep- 
resents two age groups, one a year older than 
the other, as postulated by Brock. The growth 
of the Oregon albacore, on the other hand, was 
somewhat less than that estimated for the Cal- 
ifornia albacore, and consequently lower than 
the growth shown by the tagged fish. 
Suda (1954) has examined the size distribu- 
tion of albacore taken in the Japanese winter 
long-line season and has traced six different size 
groups which appear yearly. The modes of these 
groups were: 57 cm., 67 cm., 78 cm., 89 cm., 
100 cm., and 111 cm. The spacing of the in- 
tervals is uniformly 10 or 11 cm., thus rep- 
resenting a straight-line growth if these length 
groups are assumed to be age classes. The author 
concluded that these length groups may be con- 
sidered as age groups if they are handled as five 
groups consisting of ages I to IV and an ad- 
TABLE 4 
Modal Lengths of California and Oregon 
Albacore, in Centimeters 
(Reproduced from Table 7, Brock, 1943) 
GROUP A 
| GROUP B 
DIFFERENCE 
CALIFORNIA ALBACORE (1924 to 1928) 
1924, 64.89 
1925, 77.18 
12.29 
1925, 64.87 
1926, 77.16 
13.29 
1926, 68.84 
1927, 81.04 
12.20 
1927, 65.80 
1928, 78.27 
12.47 
OREGON ALBACORE (1938 to 1940) 
1938, 66.18* 
1939, 74.19 
8.01 
1939, 64.02 
1940, 74.26 
10.24 
* Only a single small sample was taken in 1938 after the 
season was underway. 
N N+l N+2 N+3 N+4 N+5 N+6 N+7 N+8 N+9 
AGE IN YEARS 
Fig. 8. A comparison of the growth curves obtained 
by the vertebral method with the Walford curve ob- 
tained in this study. Specific ages are disregarded in 
the plotting of these curves. 
vanced age group which includes the last two 
modal groups. If these modal lengths are com- 
pared with the results obtained from tagging, 
it is seen that as in the case of the results ob- 
tained by the vertebral method, the yearly 
growth increments do not differ greatly, but 
there is a marked difference in the curvatures 
of the two curves. Suda pointed out that since 
growth of most living organisms is logistic, it 
may be unreasonable to postulate these length 
groups as age groups. However, he advanced 
the possibility that these age groups fall within 
the relatively straight portion of the growth 
curve. This is not indicated by the data pre- 
sented in this paper. 
DISCUSSION 
The tag recoveries have shown that albacore 
migrate considerable distances, and from one 
fishery to another, suggesting that there is a 
single population of albacore in the temperate 
North Pacific, exploited seasonally by Amer- 
icans off the West Coast during the summer 
and fall, by the Japanese in mid-ocean during 
the winter, and also by the Japanese in the 
western Pacific during the spring and summer. 
While no recoveries of albacore tagged off 
Japan have yet been reported in the American 
fishery, there are suggestions of movements in 
that direction. For example, recoveries 11 and 
12 were of fish tagged within a week of each 
