U.S. Department of Commerce
Population Structure of Island-Associated Dolphins: Evidence from Photo-Identification of Common Bottlenose Dolphins (Tursiops truncates) in the Main Hawaiian Islands
Date of this Version
Management agencies often use geopolitical boundaries as proxies for biological boundaries. In Hawaiian waters a single stock is recognized of common bottlenose dolphins, Tursiops truncatus, a species that is found both in open water and nearshore among the main Hawaiian Islands. To assess population structure, we photo-identified 336 distinctive individuals from the main Hawaiian Islands, from 2000 to 2006. Their generally shallow-water distribution, and numerous within-year and between-year resightings within island areas suggest that individuals are resident to the islands, rather than part of an offshore population moving through the area. Comparisons of identifications obtained from Kaua‘i/Ni‘ihau, O‘ahu, the “4- island area,” and the island of Hawai‘i showed no evidence of movements among these island groups, although movements from Kaua‘i to Ni‘ihau and among the “4-islands” were documented. A Bayesian analysis examining the probability of missing movements among island groups, given our sample sizes for different areas, indicates that interisland movement rates are less than 1% per year with 95% probability. Our results suggest the existence of multiple demographically independent populations of island-associated common bottlenose dolphins around the main Hawaiian islands.
Published in MARINE MAMMAL SCIENCE, VOL. 25, NO. 2, 2009.