423 



ADStr3Ct.— Two cosmopolitan spe- 

 cies of frigate tunas, Auxis thazard 

 (Lacepede) and A. rochei (Risso), are 

 differentiated primarily by the width 

 of the corselet under the origin of the 

 second dorsal fin and by the anterior 

 extent of the dorsal scaleless area above 

 the pectoral fin. Auxis thazard has five 

 or fewer scales in the corselet under the 

 second dorsal fin, and the dorsal scale- 

 less area extends anterior to the tip of 

 the pectoral fin; A. rochei has six or 

 more scales and the dorsal scaleless 

 area does not reach the tip of the pec- 

 toral fin. Of nine morphometric char- 

 acters examined with ANCOVA, four 

 body depth measurements were signifi- 

 cantly different between the species. 

 Auxis rochei is a slender species with 

 each of the four body depth measure- 

 ments approximately equal, whereas 

 A. thazard is more tuna-shaped, with 

 a deeper, more robust body and with 

 more unequal body depth measure- 

 ments. For both species, eastern Pacific 

 populations differ from Atlantic and 

 Indo-West Pacific populations at what 

 we consider the subspecific level. The 

 eastern Pacific A. thazard brachydorax 

 new subspecies has more gill rakers, 

 usually 43-48 vs. usually 38-42 in 

 A. t. thazard. Body depth at anal-fin ori- 

 gin, pectoral-fin length, and corselet 

 width were also significantly different 

 between A. thazard brachydorax and 

 A. t. thazard. The eastern Pacific 

 A. rochei eudorax new subspecies has 

 an even wider corselet than that of 

 A. rochei rochei, usually more than 20 

 scales wide compared with 6-19 scales. 



Revision of the frigate tunas 

 (Scombridae, Auxis), with descriptions 

 of two new subspecies from the 

 eastern Pacific 



Bruce B. Collette 



National Marine Fisheries Service Systematics Laboratory 

 National Museum of Natural History, Washington, D C 20560 



Christopher R. Aadland 



National Marine Fisheries Service Systematics Laboratory 

 National Museum of Natural History, Washington, DC 20560 

 Present address: AsCI Inc , 7o USAE Waterways Experiment Station 

 Trotters Shoals Research Facility 

 RO. Box 533, Calhoun Falls, South Carolina 29628 



Manuscript accepted 23 January 1996. 

 Fishery Bulletin 94:423-441 (1996). 



It is not clear whether there are one 

 or two species of frigate tunas of the 

 genus Auxis. In the Indo-West Pa- 

 cific region, several investigators 

 have distinguished a narrow-cor- 

 seleted species (N) from a wide- 

 corseleted species (W): Bleeker 

 (1854, 1855) from the East Indies 

 as A. tapeinosoma (N) and A. thyn- 

 rcoicfes(W);Kishinouye(1915, 1923) 

 from Japan as A. hira (N) and A. 

 maru (W); Wade (1949) from the 

 Philippines and Jones (1958) from 

 India as A. thazard (N) and A. 

 tapeinosoma (W); and Matsumoto 

 ( 1960a) from Hawaii as A. thazard 

 (N) and A. thynnoides (W). However, 

 most Atlantic-based workers have 

 considered the frigate tunas to be a 

 single worldwide species which they 

 have identified as Auxis thazard 

 (Dresslar and Fesler, 1889; Jordan 

 and Evermann, 1896; Fraser-Brun- 

 ner, 1950; Rivas, 1951; Zavala- 

 Camin, 1983). Fitch and Roedel 

 (1963) have shown that there are 

 two sympatric species of frigate tu- 

 nas in the Indo-West Pacific: the 

 narrow-corseletedA. thazard (Lace- 

 pede) and the wide-corseleted A. 

 rochei (Risso) (Fig. 1). They used the 

 name A. rochei for the wide-cor- 

 seleted species on the supposition 



that only one species occurred in the 

 Mediterranean Sea and Atlantic 

 Ocean and that rochei was the ear- 

 liest name for it. Richards and 

 Randall (1967) have shown that 

 both species occur in the Atlantic, 

 reopening the question of the proper 

 name for Atlantic Auxis. 



Frigate tunas (Auxis) are the 

 smallest members of the tribe 

 Thunnini, the true tunas. Auxis 

 rochei reaches a fork length (FL) of 

 600 mm and Auxis thazard, at least 

 420 mm. To date, frigate tunas have 

 not been greatly exploited, partly 

 because of their small size. Of the 

 total world catch of tunas, bonitos, 

 and billfishes in 1993 (4,654,750 

 metric tons (t), FAO, 1995), only 

 4.5% (208,305 t) was Auxis. The 

 largest landings are by Asian coun- 

 tries (Philippines 110,357 t; Thai- 

 land 36,300 t; Japan 27,896 t; and 

 India 15,684 1). Auxis has soft meat 

 and is not suitable for sashimi 

 (slices of raw fish) because of its 

 strong astringent taste, probably 

 due to the high level of free amino 

 acids in the meat (Murata et al., 

 1994). At least as larvae, Auxis are 

 widespread and very abundant 

 (Yabeetal., 1963, fig. 15;Ahlstrom, 

 1971; Ramiriz-Estevez and Ornelas- 



