" OKINAWA /-^j MARCUS I. 



/ 1 



MARIANAS 



V 



FIGURE 14. Somples of tuna blood and other specimens for im- 

 munogenctic determinotion have been collected of the locations in 

 the Pacific Ocean shown here. In addition, the Loborotory has ona- 

 lyzed samples from the Atlantic Oceon. Chief finding to dote is that 

 there arc pronounced differences in the genetic composition of tuna 

 populations in the wastern Pacific (areas enclosed by dashed lines) ond 

 those in the central and eastern Pacific (orcas enclosed by solid 

 lines). Shading indicates that numerous samples hove been token 

 from the area. The dividing line between the two subpopulotions lies, 

 in winter, somewhere near Marcus Islond. The western Pacific sample 

 shown to the northeast of Marcus Island wos collected in summer. 



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