[MARMAM] New publications on Steno & Pseudorca in Hawaii
Robin W Baird
RWBaird at cascadiaresearch.org
Tue May 20 07:52:03 PDT 2008
Two publications on site fidelity, movements, and association patterns of two species of poorly-known odontocetes in Hawaiian waters are now available from the Marine Mammal Science OnlineEarly Articles website. Any subscribers to MMM can download pdfs through the Online Journal link on the Society for Marine Mammalogy members website at www.marinemammalogy.org/members/
For those who are not MMS subscribers or otherwise are not able to download the papers on-line, please contact me for pdfs. For more information on this research see www.cascadiaresearch.org/robin/hawaii.htm
Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden, M.H. Deakos, A.D. Ligon, G.S. Schorr, J. Barlow and S.D. Mahaffy. 2008. False killer whales (Pseudorca crassidens) around the main Hawaiian Islands: long-term site fidelity, inter-island movements, and association patterns. Marine Mammal Science 24. doi: 10.1111/j.1748-7692.2008.00200.x
Despite their world-wide distribution throughout the tropics and subtropics, false killer whales (Pseudorca crasssidens) are one of the lesser-known large odontocetes. Genetic evidence indicates a demographically isolated population around the main Hawaiian Islands. We examine site fidelity, movements and association patterns in this population using data from directed surveys and opportunistic photographs from 1986 to 2007. This species was only infrequently encountered, and while found in depths from 38 to 4,331 m, sighting rates were greatest in depths > 3,000 m. We photo-identified 152 distinctive individuals. Resighting rates were high, with an average of 76.8% of distinctive individuals within groups documented on more than one occasion. Most (86.6%) were linked by association into a single association network; only one large group (16 distinctive individuals) documented the farthest offshore (42-70 km), did not link by association into that large network, and may be part of an offshore population. Individual movements of up to 283 km were documented, with a large proportion of individuals moving among islands. Individuals were resighted up to 20.1 yr after first being documented, showing long-term fidelity to the islands. Repeated associations among individuals were documented for up to 15 yr, and association analyses indicate preferred associations and strong bonds among individuals.
Baird, R.W., D.L. Webster, S.D. Mahaffy, D.J. McSweeney, G.S. Schorr, and A.D. Ligon. 2008. Site fidelity and association patterns in a deep-water dolphin: rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago. Marine Mammal Science 24. doi: 10.1111/j.1748-7692.2008.00201.x
In the Pacific, rough-toothed dolphins (Steno bredanensis) are typically found in the open ocean and in deep water around oceanic islands. We examine habitat use, site fidelity, movements, and association patterns of this species in the main Hawaiian Islands. Sighting rates were highest in depths > 1,500 m. There were frequent within- and between-year resightings off the island of Hawai'i, indicating a small population size with high site fidelity. Resighting rates were lower off Kaua'i/Ni'ihau, indicating a larger population size, but with some site fidelity. Two individuals were documented moving from Kaua'i to Hawai'i, a distance of 480 km, but were not seen to associate with dolphins off Hawai'i. Observed movements were consistent with at most 2% dispersal per year between these two areas. Differences in group size, habitat use, and behavior imply that movements amond the islands may be limited. Little is known about the diet of rough-toothed dolphins in Hawai'i, but they are thought to feed primarily on near-surface species. High fidelity to deep-water areas off the island of Hawai'i likely reflects an increase in the predictability of prey associated with upwelling due to the island mass effect, wind stress curl and cyclonic eddies that form off the island.
Robin W. Baird, Ph.D.
Cascadia Research Collective
218 1/2 W. 4th Avenue
e-mail: rwbaird at cascadiaresearch.org
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