444 
small as 12.4 cm in standard length. This char- 
acter is the laterally flattened shape of the hae- 
mal spine of the first caudal vertebra (first 
elongate haemal spine) which is unique to al- 
bacore. It is interesting to note that although 
several investigators have studied the anatomy 
and morphology of albacore in great detail, the 
significance of this character was not recognized 
by them. Recently, Matsumoto (1963) investi- 
gated this structure in detail and showed con- 
clusively that among the tunas it is only found 
in albacore. 
The 12 juvenile albacore reported on here 
were identified on the basis of this character 
(Fig. 3). The flat haemal spine was readily 
observable in all of the specimens, the smallest 
of which measured an estimated 61 mm in 
standard length. The width of the spine was 
from about 1.3 to 2.3 times the width of the 
haemal spine following it. Furthermore, the 
juveniles possessed other albacore characters. As 
PACIFIC SCIENCE, Vol. XIX, October 1965 
in adults, the juveniles had 7-9 + 1 + 19-21 
= 27-30 gill rakers and 39 vertebrae ( 18 pre- 
caudals and 21 caudals). 
DESCRIPTION OF JUVENILE ALBACORE 
Although the specimens were partially dam- 
aged by digestion, counts and measurements 
were made on the juveniles whenever they 
could be made accurately (Table 1). 
The shape of the juveniles is more or less 
fusiform. Each jaw has a single row of small 
teeth. Villiform teeth are present on the pala- 
tines and vomer. The snout is short and some- 
what pointed; the mouth is moderate. The ver- 
tebrae number 18 -j- 21 = 39, including the 
urostyle. The first closed haemal arch is on 
the 10th vertebra. In two specimens the bones 
producing the arch on the 10th vertebra are 
in contact but not fused; in three specimens the 
arch is damaged. The angle made by the first 
closed haemal arch and the vertebral axis is 
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liijiffliliraiiiii uuliiii 
rnilnii 
unlit 
ttufntt 
iiuttiiJjiiiliitJmiliMJ iiitliniiiiil 
' 
* 
: : . ' ■ : ^ ^ \. 
Fig. 2. Juvenile albacore 184 mm in standard length found in the stomach of a blue marlin caught off Kona, 
Hawaii, August 1, 1962. (The last few vertebrae became detached from the rest of the fish subsequent to 
measurement and are not shown in the photograph.) 
