430 



Fishery Bulletin 94(3). 1996 



Figure 7 



Distribution of Auxis rochei and A. thazard. Solid lines show approximate limits of distribution; symbols indicate localities of specimens 

 examined. 



year; although off Costa Rica spawning is heaviest 

 from December through April, whereas in Japanese 

 waters it peaks in July as expressed by the index of 

 sexual maturity. In the southern Indian Ocean, the 

 spawning season extends from August to April; north 

 of the equator it is reported from January to April. 

 Fecundity was estimated at about 1.37 million eggs 

 per year in a 44.2-cm-long female. Fecundity offish 

 in Indian waters ranged between approximately 

 200,000 to 1.06 million eggs per spawning in corre- 

 lation with size of females. 



Size Maximum fork length from drift net records 

 in the Indian Ocean is 510 mm, but off Sri Lanka it 

 is 580 mm; common lengths range between 250 and 

 400 mm FL depending on gear type and may also 

 vary seasonally and by region. Size at first maturity 

 is reported at about 290 mm FL in Japanese waters 

 but at about 350 mm around Hawaii. Auxis thazard 

 grows to be larger than A. rochei. 



Subspecies The eastern Pacific population of A. 

 thazard has more gill rakers, leading us to describe 

 it as a separate subspecies. Linear regression analy- 

 ses of morphometric characters for A. thazard showed 

 significant differences between the eastern Pacific 

 and the remaining combined populations in four char- 



