north-south range is considerably greater — from the coast 

 of Japan to that of Australia. 



The distribution of yellowfin tuna larvae is very different. 

 They have been taken in many localities in the eastern 

 Pacific, from Baja California to Panama, and throughout 

 the central and western Pacific. 



As for the other tuna species, data are scarce indeed. Some 

 bigeye tuna larvae have been caught in the eastern and 

 central Pacific, often very far at sea, and near the Philip- 

 pines. Bluefin tuna larvae have been reported only from 

 around Taiwan. Very young albacore have been caught near 

 Hawaii, to the east of the Philippines, and to the east and 

 west of Samoa; Matsumoto assumes that the chief spawning 

 grounds are not too far from the two latter sites. 



The material on the larvae allows the depiction of spawn- 

 ing season. In higher latitudes, skipjack tuna spawn mainly 

 from late spring to early fall, according to Matsumoto, but 

 in the equatorial region they spawn the year around. 



One of the most interesting aspects of Matsumoto's work 

 is his effort to determine the relative abundance of larvae 

 of skipjack and yellowfin tuna. Because data were few from 

 the western Pacific, he limited himself to that part of the 

 ocean east of the international date line. In a north-south 

 direction, toward the northern end of the range there were 

 far more skipjack tuna larvae at the height of the spawning 

 season than were found near the Equator, where spawning 

 takes place throughout the year. Yellowfin tuna showed no 

 such pronounced variation. 



Skipjack tuna larvae became less and less frequent from 

 west to east. The highest catches per tow, indeed, were made 

 only a few degrees east of the international date line. Beyond 

 long. 130" W., that is, within the area of the eastern 

 Pacific fishery for skipjack tuna, almost no skipjack tuna 

 larvae were found. 



Although yellowfin tuna larvae were also more abundant 

 at the date line they were also found in considerable quanti- 



FIGURE 13. Plankton tows show thot skipiock tuna larvae are wide- 

 spreod ond plentiful in the centrol Pacific, sparse in the eastern 

 Pacific. The top port of the figure shows the distribution of skipiack 

 tuna larvae. The bottom port shows the overoge number of lorvoe per 

 tow taken over severe! yeors of sampling. 



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