Population structure of bottlenose dolphins in and around St. Joseph Bay, Florida.
By Brian C. Balmer, MSc Student, University of North Carolina, Wilmington

During 1999 and 2004, bottlenose dolphins along the Florida panhandle experienced two unusual mortality events resulting in the deaths of more than 227 dolphins. The majority of these strandings were located near St. Joseph Bay, but it is not known which stock(s) were impacted. This project represents the first effort to identify dolphin ranging patterns in this region. We used three methods to determine these patterns: surveys that involved both photo-identification and biopsy darting for genetic samples, and radio tracking of individuals.

Photo-identification surveys were undertaken during April – May 2004 and February – July 2005. More than 250 individuals have been identified, and over one-third of these have been identified in multiple seasons. In total, 66 biopsy samples have been collected from individuals in the St. Joseph Bay area.

In April 2005, NOAA sponsored a capture-release health assessment of dolphins in the region; nine individuals were tagged with VHF radio transmitters. These dolphins were monitored daily through boat, aerial, and/or vehicle tracking for more than 50 days. Seven radio-tagged animals were located more than 10 times with five being located more than 30 times. The tracking region covered by boat and/or truck included approximately 65 km of coastline. To ensure that tagged animals were not leaving this area, extended aerial tracking was conducted five times during May and June, ranging approximately 125 km to the east and to the west of St. Joseph Bay. Individual animal’s known maximum distance from its capture-release location ranged from 15-100 km. Two animals, which were not heard for 20 or more days, reappeared within 50 km of their capture locations, suggesting that these individuals had ranged greater than 100 km. In contrast, two others had a typical daily ranging pattern of less than 10 km.

Along with this intensive radio tracking, ongoing photo-identification surveys and biopsy dart sampling for genetic analyses will help in determining the movement patterns of bottlenose dolphins in the St. Joseph Bay region of the Florida panhandle, leading to improved definitions of stock designations. This research would not be possible without funding from NOAA Fisheries and the Disney Wildlife Conservation Fund.