Table 1.— Meristic characters of the short-corseletted frigate tuna, AuxU thazard, by various investigators. 



species stems from an overlap in the width of the corse- 

 let. Klawe (1963), lacking evidence to substantiate the 

 presence of two distinct species of Auxis in the eastern 

 Pacific, noted that there were intermediate forms of the 

 short- and long-corseletted forms. Provisionally, he used 

 A. thazard for frigate tuna from this region, but empha- 

 sized the piossibility that as samples accumulate, there 

 may be sufficient evidence to substantiate the presence 

 of two separate species. From the Indian Ocean, a few 

 large adults of A. thazard from the southwest coast of In- 

 dia were recognized as having a corselet that narrowed 

 gradually somewhat as in A. rochei instead of one which 

 tapered abruptly (Fig. 2) (Jones 1963). 



In an attempt to unravel the confusion involving this 

 genus. Fitch and Roedel (1963) examined numerous 

 adult Auxis, mostly from the Pacific, but failed to find 

 any significant morphometric differences among A. 

 thazard from the western, central, and eastern Pacific 

 (Table 3). Based on gill raker counts, they concluded 

 that the eastern Pacific jwpulation seems to be separ- 

 able from those in the central and western Pacific (Table 

 4). For adult A. rochei. Fitch and Roedel found apparent 

 differences in body measurements among areas (Table 5) 

 and in the average number of scale rows in the corselet. 

 In an earlier study, Matsumoto (1960a) observed that the 

 number of scale rows in the corselet increased with fish 

 length. But Fitch and Roedel showed that in addition to 

 the p)ositive relationship between these two variables, 

 there was also an increase in the average number of scale 



-Selected measurements of Auxis thazard from three geo- 

 graphical localities (Fitch and Roedel 1963). 



rows for similar-sized fish from west to east. Auxis rochei 

 in the western Atlantic had the fewest scale rows whereas 

 those in the eastern Pacific had the most. And for A. 

 thazard, Tortonese (1965) added that the Mediterran- 

 ean forms have characters that are not entirely identical 

 to those of the Indo-Pacific forms and suggested that geo- 

 graphical variations may be involved. 



As a result of their study. Fitch and Roedel (1963) ten- 

 tatively recognized two valid species — .4. thazard and 

 A. rochei. A summary of external and internal charac- 

 ters used by several investigators to differentiate the two 

 species of Auxis is given in Table 6. 



