EH YELLOWFIN LARGER THAN 5 MM. 

 ■ ALL OTHER TUNA LARVAE 



30 go 40 2° 0" 2" 4" 6° 8" 10° 12° 14" 16° 18° 20° 

 S. LATITUDE N. 



I7CPI60PI50^ 

 W. LONGITUDE 



Pacific, 



Figure 15. Distribution of Tuna Larvae in Central 

 Counts of the number of tuna larvae in a portion of our 



plankton samples show them to be most numerous in the hauls 

 taken near the Equator, not far from the places in which we found 

 the near-ripe and the recently spent females. Regrettably too few 

 of our hauls have been sorted for larvae to give a reliable distri= 

 bution diagram. Also, it is difficult to tell the different kinds 

 tuna apart when they are smaller than 5 millimeters fone-fifth of 

 an inch) long. This leaves the definite yellowfin larvae records 

 quite scanty and the indication of more larvae at 170°than_at 1S0° 

 W. longitude must be taken with reservation. However, these 

 very preliminary results give hope that the work on planktonic 

 larvae, as it progresses, will indicate whether the tuna spawn 

 over the entire east-west range of adults or whether spawning is 

 concentrated in one or nnore separated localities. This bears on 

 the question; Does the Pacific have one large interbreeding stock 

 of tuna or a number of separate self ^perpetuating stocks? 



16 



