446 
PACIFIC SCIENCE, Vol. XIX, October 1965 
TABLE 1 
Counts and Measurements Made on Juvenile Albacore 
(Measurements in millimeters) 
SPECIMEN NUMBER 
LHAKAUtK 
3 
4 
6 
7 
8 
11 
12 
Standard length 
— 
— - 
88 
74 
184 


Head length 
— 
— 
— 
19 
48 
— 
- — 
Postorbital length of head 
— 
— 
— 
8 
22 
■ — 
— 
iris diameter 
— 
— 
— 
6 
— 
— 
— 
Interorbital width 
— 
— 
6 
6 
14 
— 
— 
Snout length 
— 
— 
6 
5 
— - 
— 
— 
Maxillary length 
— 
— 
10 
8 
21 
— 
— 
Snout to first dorsal origin 
— 
— 
— 
21 
___ 
— 
— 
Snout to pelvic base 
— 
— 
— 
— 
59 
— 
— 
Longest pectoral ray 
— 
— 
— 
— 
12 
— 
— 
Gill rakers (number) 
Upper arch 
7 
7 
7 
9 
8 
8 
7 
Angle 
1 
1 
1 
1 
1 
1 
1 
Lower arch 
20 
20 
19 
19 
21 
20 
20 
Total 
28 
28 
27 
29 
30 
29 
28 
First dorsal fin 
— 
— 
— 
13 
14 
— 
— 
ally, starting with the anteriormost and ending 
with the parapophysis on the eighth vertebra. 
Actually, the tip of the parapophysis on the 
ninth vertebra projects ventrally and does not 
completely straighten out even in adults. 
The first haemal arch in adult albacore makes 
an angle of 45° or less with the axis of the 
vertebral column, and the bones of the arch are 
flattened dorso-ventrally (Godsil and Byers, 
1944). In juveniles the first haemal arch makes 
an angle of approximately 75-90°, with the 
greater angles generally occurring in the smaller 
specimens. The bones of the arch are flattened 
laterally. Evidently, as the albacore grows, the 
angle that the arch makes with the axis of the 
vertebral column becomes more acute. At the 
same time the posterior margins of the arch 
move forward and inward so that in adults the 
bones are compressed dorso-ventrally (Fig. 4). 
Godsil and Byers (1944:84) state that the 
posterior margin of the parasphenoid and basi- 
occipital, when viewed laterally, makes a prom- 
inent acute angle in adult albacore. However, 
a few paragraphs later (p. 85) they state that 
this margin may make an angle varying from 
slightly acute to somewhat obtuse. For our pur- 
pose, this character is perhaps best described as 
the angle the posterior margin of the basioccipi- 
tal makes with the axis of the vertebral column. 
When the cranium is viewed from the side, this 
angle is acute in adult albacore. In small juve- 
niles this angle is obtuse, but with growth it 
changes to approximately 90° and finally to 
an acute angle (Fig. 5). A juvenile measuring 
257 mm already possessed a skull similar to an 
adult. However, in a 184 mm specimen, the 
angle was still 90°. Therefore, it appears that 
this character becomes definitive in albacore at 
a standard length somewhere between 184 and 
257 mm. 
Yabe et al (1958) found that juvenile tunas 
occurred more frequently in stomachs of spear- 
fishes than of tunas. However, they also found 
that this varied according to area. Juvenile tunas 
occurred in stomachs of spearfishes and yellow- 
fin tuna caught in low-latitude waters, but not 
in bigeye tuna. North of 30° N, however, juve- 
nile tunas were also found in bigeye stomachs. 
Yabe and his colleagues suggested that this was 
due to a difference in vertical distribution of 
tunas and spearfishes, which in turn was related 
to the hydrography of the different areas. Al- 
though our sampling program was not designed 
to make such a comparison, most of our juve- 
nile albacore were found in stomachs of spear- 
fishes (Table 2). Six were found in the stom- 
achs of five blue marlin, three in the stomachs 
of three striped marlin, two in the stomach of 
