counts and measurements, Ginsburg (1953) recog- 

 nized as species the eastern Atlantic, western Atlan- 

 tic, and eastern Pacific populations but did not con- 

 sider those from other geographic regions. Serventy 

 (1956a) recognized only a single worldwide species, 

 pointing out the ontogenetic increase in relative size 

 of the swimbladder and suggesting that other dis- 

 tinguishing characters shown by Godsil and Holm- 

 berg (1950) may also be eliminated when size differ- 

 ences are considered. Serventy (1956a) suggested, 

 however, that the populations from European seas. 

 North American Atlantic coast, South Africa, North 

 American Pacific coast, Asiatic coast of the North 

 Pacific, and Australia-New Zealand, respectively, 

 each be recognized as subspecies, largely on the 

 basis of modal differences in gill-raker counts. We 

 have previously recognized a single species with only 

 two subspecies (Collette and Gibbs, 1963). Iwai et 

 al., (1965) considered T. maccoyii and T. thynnus as 

 distinct species, with no commitment as to subspecies 

 of the latter. 



When individual and ontogenetic variations are 

 considered, almost every anatomical, morphometric, 

 and meristic character has proved to be similar in all 

 populations. The only exceptions are the number of 

 gill rakers, length of pectoral fin, a few skeletal 

 characters, the shape of the dorsal wall of the body 

 cavity, and the color of the caudal peduncle keels. 

 On the basis of these characters, we tentatively 

 recognize two species of bluefin tuna: T. maccoyii, 

 mainly from the Southern Ocean south of about 

 30° S., but including an area off northwestern Aus- 

 tralia; and T. thynnus, with one subspecies, T. I. 

 thynnus, in the Atlantic, and another, T. t. orientalis 

 in the Pacific. 



We were long reluctant to recognize T. maccoyii 

 as a separate species, and even now we do so only 

 with reservation. The only convincing characters 

 that provide evidence of species status a>e the posi- 



tion of the first ventrally directed parapophysis (on 

 the 9th vertebra in T. maccoyii, as opposed to the 

 10th, in T. thynnus) and the color of the fleshy 

 caudal keels (yellow in T. maccoyii, dark in T. 

 thynnus). The few other characters, none of them 

 affording complete separation, are given in table 5. 



The presence of T. thynnus orientalis in the south- 

 eastern Pacific and the northeastern Indian Ocean 

 (Nakamura and Warashina, 1965), and of T. thynnus 

 thynnus off Cape Town (Talbot and Penrith, 1963) 

 in the same geographical areas as T. maccoyii gives 

 biological support to considering T. maccoyii as a 

 separate species, although it is not known whether 

 the two actually spawn in the same areas. 



Differences in the configuration of the dorsal wall 

 of the body cavity are not apparent in specimens less 

 than about 1,300 mm. As described by Godsil and 

 Holmberg (1950), numerous western Atlantic speci- 

 mens (7". t. thynnus) examined by us in the field and 

 laboratory had a wide anterior bulge without a lat- 

 eral concavity and had a deep, narrow trough lateral 

 to the bulge (fig. 32). Our only large specimen of 

 T. maccoyii (1,450 mm.) was similar to the western 

 Atlantic forms. Eastern Pacific specimens of T. t. 

 orientalis, 1,390 and 1,450 mm., confirm the dif- 

 ferences described by Godsil and Holmberg. The 

 anterior bulge is comparatively narrow, with a lateral 

 concavity, and with a wide trough lateral to the 

 bulge (fig. 32). Although we have dissected no large 

 Japanese specimens, we are confident they will 

 resemble those from the eastern Pacific. 



Godsil and Holmberg (1950) eliminated a large 

 number of characters from systematic consideration. 

 We can substantiate almost all of their conclusions, 

 and our observations invalidate most of their remain- 

 ing differential characters. 



The tubules of the caecal mass of T. t. thynnus and 

 T. t. orientalis were said to be relatively large and 



T.\BLE 5. — Comparison of Thunnus maccoyii and the subspecies of T. thj'iinus 

 IMean values given in parentheses] 



AX.\TOMY AND SYSTEM.\TICS OF TUNAS 



113 



