2.2 Differential distribution 



2.21 Spawn, larvae, and juveniles 



The larvae ofAuxis, like the eggs which precede them, 

 are displaced from the area of spawning due to drift of 

 the ocean currents (Matsumoto 1958, 1959). Except in a 

 few areas where currents are swift, the actual displace- 

 ment of eggs and larvae appears to be relatively insig- 

 nificant. 



Whereas the distribution of adult Auxis is usually as- 

 sociated with land masses, that of the larvae has been 

 described as not only coastal but also oceanic. Figure 9 

 shows the localities of capture of Auxis larvae in the 

 world's oceans. The actual differences in larval and 

 adult distributions, however, may not be real. The 

 adults are usually reported to occur in coastal waters 

 because most of the fishing is done there. But plankton 

 hauls conducted in waters far from land masses have 

 shown that larval Auxis occur in oceanic as well as 

 coastal waters. Matsumoto (1958, 1959) suggested that 



the localities where larvae of about 3 mm occur prob- 

 ably represent actual spawning sites; therefore, it can be 

 expected that adult Auxis also occur in the oceanic 

 regions of the world's oceans. Watanabe (1964), on the 

 other hand, studying tuna and billfish stomach con- 

 tents, concluded that Auxis are coastal dwellers. 



The distribution of juvenile Auxis, 10-20 cm SL (stan- 

 dard length), agrees well with that of the larvae, es- 

 pecially near land masses, but in the oceanic regions the 

 presence of juveniles have not been well documented 

 (Fig. 10). Yabe et al. (1963) pointed out that the usual 

 method of using a midwater trawl to collect juveniles 

 has not been successful quantitatively; rather, more in- 

 formation can be obtained through examination of 

 stomach contents of large tunas and billfishes. 



That juvenile Auxis occur mostly in waters close to 

 land masses is brought out in Table 7 which shows the 

 number of juvenile Auxis taken by midwater trawl in 

 Hawaiian waters. Higgins (1970) observed that in July- 

 September 1967, the catch rate of juvenile Auxis 

 reached 3.5 individuals/tow, the highest among all the 



20* <0* 60* 90* 100* 120* 



20* 40* eo* 



120* MO- teo* lao* i6o* iw 120* 



Figure 9.— Localities of capture of larval Auxia (Yabe et al. 1963). 



Figure 10.— Localities of capture of juvenile (10-20 cm SL) Auxis (Yabe et al. 1963). 



13 



