Spinner dolphins in Hawai‘i

Two spinner dolphins (Stenella longirostris) off the island of Hawai‘i. Photo by Annie Douglas. In our study spinner dolphins are the fourth-most frequently encountered species, in part because the area outside of the harbor that we leave from on the island of Hawai‘i is a traditional resting site for this population. Of the 138 "on-effort" sightings, 70% of them are within a kilometer of shore, and 88% of them are in less than 100 m water depth. Overall in 10 years of research we've spent about half of our time in water depths of >1,000 m, yet we have only seen spinner dolphins once in depths > 1,000 m, a group that was likely transiting from Kaua‘i to Ni‘ihau during the afternoon.

Spinner dolphin group. Photo by Robin Baird. Since so much research has been undertaken on spinner dolphins in Hawai‘i they are our lowest-priority species for research. We have collected and contributed genetic samples to population structure studies through the University of Hawai‘i and also photographs for a collaborative study of spinner dolphins coordinated through the Pacific Islands Photo-identification Network.

Spinner dolphin spinning. Photo by Robin Baird. Group sizes of spinner dolphins encountered in our study have ranged from three individuals to an estimated 185 individuals, with a mean group size of 42 and a median group size of 27 individuals.

Spinner dolphin spinning. Photo by Robin Baird

Spinner dolphin spinning. Photo by Robin Baird

For more information on our sightings of spinner dolphins see the following:

  • Baird, R.W., G.S. Schorr, D.L. Webster, S.D. Mahaffy, A.B. Douglas, A.M. Gorgone, and D.J. McSweeney. 2006. A survey for odontocete cetaceans off Kaua‘i and Ni‘ihau, Hawai‘i, during October and November 2005: evidence for population structure and site fidelity. Report to Pacific Islands Fisheries Science Center, NOAA Fisheries, under Order No. AB133F05SE5197 with additional support from the Marine Mammal Commission and Dolphin Quest. Download PDF copy
  • Baird, R.W., D.J. McSweeney, D.L. Webster, A.M. Gorgone and A.D. Ligon. 2003. Studies of odontocete population structure in Hawaiian waters: results of a survey through the main Hawaiian Islands in May and June 2003. Report prepared under Contract No. AB133F-02-CN-0106 from the National Oceanic and Atmospheric Administration, Western Administrative Support Center, 7600 Sand Point Way N.E., Seattle, WA 98115 USA.Download PDF copy

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