FISHERY BULLETIN: VOL. 70. NO. 1 



DISCUSSION AND SUMMARY 



T. thynnus below 25 mm SL can be separated 

 from the other Thunnus species by the array of 

 pterygiophores of the second dorsal fin, the last 

 four positions containing 2, 2, 1, 1 pterygio- 

 phores; in T. alabmga the sequence is 2, 3, 2, 1, 

 and in T. atlanticus, T. obesus, and T. albacares 

 it is 3, 2, 1, 1, T. thynnus above 25 mm SL can 

 be separated from all other Thunnus by the 

 sharp angle (nearly 90°) which the lateral line 

 follows near the base of the pectoral fin; in all 

 other species this angle is obtuse. In juveniles 

 above 40 to 45 mm SL, T. thynnus has the highest 

 number of gill rakers on the ceratobranchial, in- 

 cluding that at the angle (Potthoff and Richards, 

 1970). 



T. alalunga below 30 mm SL can be separated 

 from other Thunnus species by the distribution 

 of pterygiophores of the second dorsal fin. Above 

 30 mm SL, T. alalunga is the only species whose 

 first elongated haemal spine is flattened laterally 

 and appears extremely winglike. 



T. atlanticus as small as 13 mm SL can be sep- 

 arated from other Thunnus species by its dis- 

 tinctive precaudal and caudal vertebral counts. 

 It is the only species having 19 precaudal and 

 20 caudal vertebrae. Above 40 to 45 mm SL, 

 this species can be separated from the others by 

 the low (12-13) gill raker count on the cerato- 

 branchial (Potthoff and Richards, 1970), in ad- 

 dition to the vertebral formula. 



T. obesus and T. albacares are the only two 

 species that cannot be distinguished from each 

 other on the basis of internal characters. Com- 

 parisons of body parts, i.e., orbit diameter, body 

 depth or preanal and postanal distances, may 

 have to be used. 



ACKNOWLEDGMENTS 



We thank John C. Marr, former Area Director, 

 BCF Biological Laboratory, Honolulu, who orig- 

 inated the idea of the workshop; Richard S. 

 Shomura, former Acting Area Director of the 

 same Laboratory, who continued with the orig- 



inal idea and organized the workshop ; and the 

 BCF Biological Laboratory, Honolulu, Hawaii, 

 for providing laboratory space and facilities. 

 The workshop was supported entirely by the 

 Bureau of Commercial Fisheries (now National 

 Marine Fisheries Service). 



LITERATURE CITED 



Matsumoto, W. M. 



1958. Description and distribution of larvae of 

 four species of tuna in central Pacific waters. 

 U.S. Fish Wildl. Serv., Fish. Bull. 58: 31-72. 



1962. Identification of larvae of four species of 

 tuna from the Indo-Pacific region I. Dana Rep. 

 Carlsberg Found. 55, 16 p. 



1967. Morphology and distribution of larval wahoo 

 Acanthocybimn solandri (Cuvier) in the central 

 Pacific Ocean. U.S. Fish Wildl. Serv., Fish. Bull. 

 66: 299-322. 

 Otsu, T., and R. J. Hansen. 



1962. Sexual maturity and spawning of the alba- 

 core in the central South Pacific Ocean. U.S. 

 Fish Wildl. Serv., Fish. Bull. 62: 151-161. 

 Potthoff, T., and W. J. Richards. 



1970. Juvenile bluefin tuna, Thunnus thynnus (Lin- 

 naeus), and other scombrids taken by terns in 

 the Dry Tortugas, Florida. Bull. Mar. Sci. 20: 

 389-413. 

 Ueyanagi, S. 



1966. On the red pigmentation of larval tuna and 

 its usefulness in species identification. [In Jap- 

 anese, English summary.] Rep. Nankai Reg. 

 Fish. Lab. 24: 41-48. 



1969. Observations on the distribution of tuna lar- 

 vae in the Indo-Pacific Ocean with emphasis on 

 the delineation of the spawning areas of albacore, 

 Thunnus alalunga. [In Japanese, English sum- 

 mary.] Bull. Far Seas Fish. Res. Lab. 2: 177-256. 

 Yabe, H., and S. Ueyanagi. 



1962. Contributions to the study of the early life 

 history of the tunas. Occas. Pap. Nankai Reg. 

 Fish. Res. Lab. 1: 57-72. 

 Yabe, H., S. Ueyanagi, and H. Watanabe. 



1966. Studies on the early life history of bluefin 

 tuna Thunnus thynnus and on the larva of the 

 southern bluefin tuna T. maccoyii. [In Japanese, 

 English summary.] Rep. Nankai Reg. Fish. Res. 

 Lab. 23: 95-129. 

 Yuen, H. S. H., and F. C. June. 



1957. Yellowfin tuna spawning in the central equa- 

 torial Pacific. U.S. Fish Wildl. Serv., Fish. Bull. 

 57: 251-264. 



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