Table IS. — Standard length and gill raker counts of juvenile Auxi» 

 thazard and A. roehei (Wade 1949). 



'Low count possibly due to the small size of the specimen and the un 

 veloped gill rakers. 



Some investigators believe that the separation of 

 juvenile Auxis into either A. thazard or A. roehei could 

 be accomplished by gill raker counts alone (Table 15). In 

 small specimens, errors in gill raker counts are possible, 

 but in specimens 25-30 mm SL, no difficulty should be 

 experienced (Wade 1949). Schaefer and Marr (1948), 

 however, observed that in a 21 mm specimen, the gill 

 rakers are very tiny projections and are difficult to 

 count. The rakers are first apparent near the angle of the 

 arch, but as the fish increases in size, those that are near 

 the angle of the arch increase in length and new rakers 

 are added distally on each arm. Schaefer and Man- 

 judged by counts on specimens of various sizes that the 

 full complement of rakers on A. thazard is attained at 

 about 50 mm TL, but Klawe and Shimada (1959), who 

 plotted the total gill raker counts against corresponding 

 total lengths, found that the full complement is attained 

 at sizes 40 mm or larger (Fig. 27). And Wade (1949) 

 reported that in A. roehei, the full complement of gill 

 rakers can be found in juveniles as small as 32 mm. 



20 30 40 50 60 .70 80 90 100 110 

 TOTAL LENGTH (mm) 



Figure 27. — Gil raker counts of young Auxis thazard plotted 

 against total length (Klawe and Shimada 1959). 



Noting that their specimens differed in some respects 

 from observations made by Starks (1910) and Kishi- 

 nouye (1923), Schaefer and Marr (1948) suggested that 

 some of the specimens they examined may be juveniles 

 of an undescribed species. Wade (1949), on the other 

 hand, suggested that Schaefer and Marr examined 

 juveniles of two species of Auxis. Schaefer and Marr's 

 specimens, 42, 48, and 68 mm TL, had gill raker counts 

 of 39, 41, and 42, respectively; these counts fall within 

 the limits for ^4. thazard. Two other specimens — 52 and 

 54 mm — had gill raker counts of 48 and 47, respectively, 

 well within the limits of the gill raker counts for A. 

 roehei. 



Juveniles of A. thazard collected in Indian water.s 

 have also been misidentified as those of A. roehei. 

 Originally, Jones (1961) examined 26 juvenile specimens 

 collected from Vizhingam on the west coast of India and 

 called them A. roehei (Table 16). In a later paper, Jones 

 (1963) pointed out that on reexamining the material, 

 specimens measuring 44.0-132.0 mm in length cannot be 

 definitely assigned to A. roehei; rather, they could more 

 correctly be assigned to A. thazard. He concluded that 

 the remaining juveniles, from 181.0 to 209.8 mm were 

 most likely A. roehei. 



Juvenile Auxis are presumed to be relatively abun- 

 dant in the world's oceans. One published report, based 

 on the examination of juvenile tunas collected by 

 midwater trawling in Hawaiian waters, indicated that 

 the relative abundance of juvenile tunas is highest for 

 skipjack tuna, reaching 7.0 juveniles/tow during the 

 summer followed by yellowfin tuna, which was esti- 

 mated at 2.2 individuals/tow (Higgins 1970). The catch 

 rates were 1.6 individuals/tow for Auxis and below 1.0 

 individuals/tow for bigeye tuna, Thunnus obesus; alba- 

 core; and kawakawa, Euthynnus affinis. 



3.3 Adult phase 



3.32 Hardiness 



The literature contains no direct evidence in refer- 

 ence to the hardiness of Auxis. Kishinouye (1923) 

 observed that the salinity preference of scombroid fishes 

 differs widely for different species. Auxis are sometimes 

 seen in littoral waters of low density and apptirently 

 show no ill effect. 



3.33 Competitors 



Auxis compete against other tunas and tunalike fishes 

 during all stages of their lives. Food studies indicate 

 that most of the organisms consumed by Auxis also con- 

 stitute part of the diet of other tuna and tunalike fishes; 

 therefore, many species compete with them for food. 



Species that have been mentioned specifically as pos- 

 sible competitors of Auxis in Japanese waters are given, 

 by type of gear, in Table 17. In Hawaiian waters, (iosline 

 and Brock (1960) observed that sometimes Auxis and 

 kawakawa are caught in the pole-and-line fishery from 

 mixed schools indicating that those two species .-re com- 



31 



