Collette and Aadland: Revision of the frigate tunas (Scombridae. Auxis) 



427 



15 



10 



• Auxis rochet 

 Auxis thazard 









 150 200 250 300 350 400 450 500 



Fork length (mm) 



Figure 3 



Corselet width under second dorsal-fin origin vs. fork 

 length in Auxis rochei (closed circles, y = 0.005.V + 3.933, 

 r=0.09) and A. thazard (open circles, y = 0.006 - 0.673, 

 r=0.62). 



species (Wade, 1949, Philippines; Matsumoto, 1959 

 Gorbunova, 1969, 1974, Indian and Pacific oceans 

 Zhao et al., 1982, and Sun et al., 1986, China 

 Richards, 1989, western central Atlantic). Juveniles 

 have been successfully identified (e.g. Wade, 1949), 

 but larvae are more difficult to identify to species 

 because the corselet scales and gill rakers that dis- 

 tinguish the adults are not fully developed in the lar- 

 vae. For brief length intervals, pigment characters 

 are useful in distinguishing two types of larvae. 



Gorbunova ( 1974) distinguished between larvae of 

 the two species. Auxis rochei is characterized by a 

 seemingly slower rate of development and a shal- 

 lower body depth. The relative size of the eye is 

 smaller and the pigmentation on the caudal peduncle 

 is less intense. Auxis thazard is distinguished by a 

 more rapid rate of development, a greater body depth, 

 a shorter caudal portion of the body, and more in- 

 tense body pigmentation. Richards (1989) empha- 

 sized the presence of pigment along the lateral line 

 in the posterior part of the body in A. rochei and its 

 absence in A. thazard. 



Biochemical differences The first attempts to sepa- 

 rate the two species of Auxis biochemically were by 

 Matsumoto ( 1960b) who found that Hawaiian speci- 

 mens could be distinguished in a one-dimensional 

 chromatogram. Taniguchi and Nakamura ( 1970) ex- 



o 



100 150 200 250 300 350 400 450 500 

 Fork length (mm) 



Figure 4 



Body depth (BD) at anal-fin origin in Auxis rochei (closed 

 circles, y = 0.17*- 3.06, r=0.92) and A. thazard (open circles, 

 y = 0.207* - 9.58, r=0.96). 



amined muscle protein of A. thazard and A. rochei 

 by the cellulose acetate electrophoretic method. They 

 found five components in the electropherograms of 

 both species, but some components were not com- 

 mon to both. Electrophoretic patterns of the two spe- 

 cies were clearly distinguishable from each other by 

 the mobility and percentage of each component. 

 Taniguchi and Konishi (1971) used starch gel elec- 

 trophoresis to detect protein specificity between A. 

 thazard and A. rochei. No individual variation oc- 

 curred in the electropherograms of 11 specimens of 

 A. thazard, whereas all 170 specimens of A. rochei 

 fit into 1 of 3 phenotypic patterns. They hypothesized 

 that these three phenotypes are controlled by two 

 codominant alleles. Distribution of the three pheno- 

 types was independent of age and sex. 



Auxis thazard (Lacepede, 1 800) 



Frigate tuna 



Diagnosis Auxis thazard has a narrow corselet that 

 is 0.5-3.5 mm, usually 0.5-1.0 mm wide (Fig. 3) but 

 no more than five scales wide under the second dor- 

 sal-fin origin (Table 1), a greater body depth at the 

 anal-fin origin (Fig. 4), and the anterior margin of 

 the scaleless area above the corselet extends anteri- 

 orly beyond the tip of the pectoral fins (Figs. 1 and 5) 

 unlike that in A. rochei. Color pattern: 15 or more 



