27 6 
PACIFIC SCIENCE, VoL III, July, 1949 
gether, separated by a distance 
equal to about one-fifth of head 
length 4 
The first and second dorsal fins far 
apart, separated by a distance 
equal to about one-half the head 
length or more. Frigate mackerel 
* Auxis t hazard (Lacepede) 
4 ( 3 ) . Four dark longitudinal stripes pres- 
ent on lower surface below lateral 
line of side and on belly. Aku . . 
. . . . *Katsuwonus pelamis (Linne) 
No dark longitudinal stripes below 
lateral line, about 12 dark wavy 
streaks on back. Kawakawa. . . . 
. . . *Euthynnus yaito (Kishinouye) 
5 (2). Dorsal finlets with some yellow, 
usually largely yellow . 7 
Dorsal finlets without any yellow 
markings . 6 
6(5). Spines in first dorsal fin 14 or fewer 
in number. Bluefin tuna 
. Thunnus thynnus (Linne) 
Spines in first dorsal fin 18 in num- 
ber. Bonito . Sarda 
chilensis (Cuvier - & Valenciennes) 
7 (5). Gill rakers on upper and lower 
branch of first gill arch fewer 
than 32 in number, usually fewer 
than 30 8 
Gill rakers on upper and lower 
branch of first gill arch 36 to 39 
in number; pectoral fin does not 
reach to a vertical through second 
dorsal fin insertion; anal finlets 
silvery. Black tuna, Maguro .... 
Thunnus 
orientalis (Temmnick & Schlegel) 
8 (7). Gill rakers on upper and lower 
branch of first gill arch 24 or 
more in number; air bladder 
present; pectoral fin reaches, in 
most of the species included here, 
to or beyond a vertical through 
the last spine of the first dorsal 
fin 9 
Gill rakers on upper and lower 
branch of first gill arch 23 or 
fewer in number; no air bladder; 
pectoral fin does not reach to a 
vertical through caudal end of 
first dorsal fin; size small, usually 
less than 25 pounds 
Kishinoella rara (Kishinouye) 
9(8). Anal finlets with yellow or orange 
color; a vertical line through tip 
of pectoral fin usually falls an- 
terior to end of anal fin base, at 
least in larger specimens of over 
70 or 80 pounds 10 
Anal finlets dusky without yellow or 
orange color; a vertical line 
through tip of pectoral fin usually 
falls posterior to end of anal fin 
base; size medium to small, rarely 
more than 70 or 80 pounds, 
usually much less. Albacore .... 
*Germo alalunga (Gmelin) 
10 (9). Dorsal and anal finlets a clear yel- 
low, very narrowly black edged; 
some large individuals of this 
species may have elongate second 
dorsal and anal fins, reaching 
nearly to the caudal fin or be- 
yond; number of gill rakers on 
upper and lower limb of first gill 
arch usually 30 (27 to 31); liver 
without marginal striations. Yel- 
lowfin tuna, Ahi . 
*Neothunnus ma- 
cropterus (Temmnick & Schlegel) 
Dorsal and anal finlets with a broad 
black border, anal finlets often 
with an orange rather than yel- 
low color; second dorsal and anal 
fins never greatly elongated, a 
little longer than the longest 
spines of the first dorsal fin and 
much shorter than pectoral fin; 
number of gill rakers on upper 
and lower limb of first gill arch 
usually 27 (24-29); liver with 
marginal striations. Bigeye tuna 
*Parathun- 
nus sihi (Temmnick & Schlegel) 
REFERENCES 
Fowler, Henry W. 1923. New or little- 
known Hawaiian fishes. Bernice P . Bishop 
Mus., Occas. Papers 8(7) : 3-20. 
1928. The fishes Oceania, iii + 540 
pp., 82 figs., 49 pis. Bernice P. Bishop Mus., 
Mem. 10. Honolulu. 
Godsil, Henry G, and Robert D. Byers. 
1944. A systematic study of the Pacific tunas. 
