Measurements of Yellowfin Tuna from the Equatorial Countercurrent Area 



The writer has previously reported in this journal how he measured yellow- 

 fin tuna (taken on longlines) from Palau waters and determined their ac^es by 

 consulting an ape-length table. The majority of the tuna taken were in their 

 seventh year; eightii-year and sixth-year fish were next most numerous. 



Past fishery investigations have shown that fish in their fourth year, and 

 some as young as the second year, are caught near the islan'is (the so-called 

 "resident fish"), but the yellowfin which migrate continually in the currents 

 of th« open sea have rarely been found to be younger than the fourth year. 



Although these facts were obtained from the results of a survey conducted 

 in the waters off Palau, they coincided in general with those obtained in the 

 later survey carried out in the waters south of the Marshall Islands. 



Since it was thought that it would be possible to get a general knowledge 

 of the morphometry of yellowfin tuna inhabiting the South Sea area by conduct- 

 ing a survey midway between the two archipelagoes, that is, in the waters south 

 of Truk, Ponape, Kusaie and Jaluit islands, we waited for an opportunity to 

 gather data in that area. When at a later date the survey ship Zuih3'Maru car- 

 ried out fishing ground surveys in that area, we measured the yellowfin taken 

 there. The results of these measurements are compiled in this article. 



As seen under the coliamn heading of current direction, every one of the 

 grounds surveyed at that time is shown to be in the area of easterly currents. 

 We can definitely assume from this fact that the fishing grormds were within 

 the Equatorial Countero'urrent. The title of this article therefore, can be 

 justified. 



The data contained in the tables which follow can be stinmariEed as f ollows j 



Table 1 



out of 2 



fth-j 

 th-j 



Table 2 



Table 3 



out of 11 



out of 9 



out of 12* 



(TN. 



1-year fish 

 -year fish 

 /7jbh to 8th-year 

 l7th-year fish 

 |6th to 7th year 

 Iffth-year fish 

 ^th-year fish 

 7th-year fish 

 '6 th to 7 th -year 

 6th-year fish 

 pth to 8th-year 

 yth-year fish 

 (sth to 6th-year 

 ^Presumed to be out of 14 with 5th to 6th-year fi 



/^th-year fish 

 7th to 8th-year 

 7th-year fish 

 6th to 7th-year 

 6th-year fish 

 5th to 6th-year 

 5th-year fish 

 7th to 8th-year 

 7th-year fish 



6th-year fish 

 "th to 7th-year 



Table 5 



out of 61 



Table 6 



out of 22 



fish 

 fish 



fish 



fish 



fish 

 sh 6) 



fish 



fish 



fish 



fish 



fish 



1 

 1 



3 

 4 

 2 

 2 

 2 

 5 

 1 

 1 

 1 

 7 

 5* 



1 



4 



38 



2 



8 



5 



3 



2 



17 



3 

 2 



