TRANS-PACIFIC MIGRATIONS OF THE LOGGERHEAD TURTLE (CARETTA-CARETTA) DEMONSTRATED WITH MITOCHONDRIAL-DNA MARKERS

Juvenile loggerhead turtles (Caretta caretta) have recently been docum ented in the vicinity of Baja California, and thousands of these anima ls have been captured in oceanic fisheries of the North Pacific, The p resence of loggerhead turtles in the central and eastern North Pacific is a prominent enigma in marine turtle distribution because the neare st documented nesting concentrations for this species are in Australia and Japan, over 10,000 km from Baja California. To determine the orig in of the Baja California feeding aggregate and North Pacific fishery mortalities, samples from nesting areas and pelagic feeding aggregates were compared with genetic markers derived from mtDNA control region sequences, Overall, 57 of 60 pelagic samples (95%) match haplotypes se en only in Japanese nesting areas, implicating Japan as the primary so urce of turtles in the North Pacific Current and around Baja Californi a. Australian nesting colonies may contribute the remaining 5% of thes e pelagic feeding aggregates. Juvenile loggerhead turtles apparently t raverse the entire Pacific Ocean, approximately one-third of the plane t, in the course of developmental migrations, but mortality in high-se as fisheries raises concern over the future of this migratory populati on.