Studies on population structure in this species indicate both broad-scale (between-ocean) limits on gene flow (e.g., Kitchener et al. 1990), and limited gene flow on smaller (within-ocean) scales (Chivers et al. 2007). Abundance has been estimated for the coastal waters of China and Japan (16,000, CV=26%; Miyashita 1993), the northern Gulf of Mexico (1,038, CV = 71%; Mullin and Fulling 2004), and the U.S. EEZ of Hawaii (268, CV=108%; Barlow 2006). Abundance in the eastern tropical Pacific has been estimated as 39,800, CV=64%; Wade and Gerrodette 1993). There is no information on global trends in abundance.
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