Baird, R.W., A.M. Gorgone, D.J. McSweeney, A.D.
Ligon, M.H. Deakos, D.L. Webster, G.S. Schorr, K.K. Martien, D.R. Salden, and
S.D. Mahaffy. Population structure of island-associated dolphins: evidence from
photo-identification of common bottlenose dolphins (Tursiops truncatus) in the
main Hawaiian Islands. Marine Mammal Science. DOI:
10.1111/j.1748-7692.2008.00257.x
Abstract
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 near-shore among the main Hawaiian Islands.
To assess population structure, we photo-identified 336 distinctive individuals
from the main Hawaiian Islands, from 2000-2006. Their generally shallow-water
distribution, and numerous within-year and between-year re-sightings 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
inter-island 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.
Robin