YOSHIDA: EARLY LIFE HISTORY OF SKIPJACK TUNA 



NUMBER OF BILLFISH STOMACHS EXAMINED 

 264 373 558 442 436 507 238 303 183 279 567 418 



slightly more numerous north of lat 10° S than 

 between lat 10° and 20° S. In 1965, however, 

 juveniles were more numerous between lat 10° 

 and 20° S than north of lat 10° S. Also they 

 appeared to be more numerous in the South Pa- 

 cific than near the Hawaiian Islands. 



About 12 ''r of the billfish stomachs from 

 Hawaii contained one or more juvenile skipjack 

 tuna, while 19 ''r of the billfish stomachs from the 

 South Pacific contained one or more juveniles. 

 In both areas the largest number of juvenile 

 skipjack tuna per stomach was 11; most of the 

 stomachs from both areas had only one juvenile. 



AGE AND GROWTH 



The length-frequency distribution of juvenile 

 skipjack tuna from Hawaii and the South Pa- 

 cific is shown in Figure 5. Near Hawaii the 

 smallest juvenile taken was 5.9 cm SL (standard 



JAN FE8 MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 



FiGUBE 3. — Apparent abundance of juvenile skipjack 

 tuna in Hawaiian waters, 1962-66. 



Juveniles were taken in all months except 

 July between lat 10° and 20° S. Here also the 

 uneven sample sizes make the analysis of ap- 

 parent abundance difficult. It appears, however, 

 that juveniles were numerous from November 

 to February. No comparable data on larval skip- 

 jack tuna in this area are available. 



The apparent abundance of juvenile skipjack 

 tuna was higher in 1964 than in 1965 in the 

 South Pacific (Table 2) . In 1964, juveniles were 



Table 2. — Annual apparent abundance of juvenile skip- 

 jack tuna in the central Pacific Ocean. 



Number 



of 

 billfishes 



Number of 



juvenile 



skipjack tuna 



juveniles 

 per 100 

 billfishes 



5 60 



O 20 



"^ \ r 



NORTH OF «• S 



124) 1 ^ 



M 



(212) 



<23) 



(16) 



JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 



Figure 4. — Apparent abundance of juvenile skipjack 

 tuna in the South Pacific. The figures in the parentheses 

 are the number of billfish stomachs that were e.xamined. 



549 



