Genetic analyses of stock structure in Tampa Bay: Examining community structure of bottlenose dolphins in Tampa Bay using a genetic approach
By Kim Urian, MSc, University of North Carolina, Wilmington

In my Master’s thesis work I described five separate communities of dolphins in Tampa Bay, defined by their patterns of association and home ranges. We are now estimating gene flow among these communities and determining how well our observations fit the “Boundary Rank” model described by Karen Martien and associates. To address these questions, we conducted photographic identification surveys and biopsy darting for genetic sampling in Tampa Bay during August 2003, and July-August 2004. Unfortunately, we were unable to conduct surveys and biopsy sampling during our field season this year, due to the frequency of hurricanes!

To ensure representative coverage, our goal is to collect at least 30 genetic samples from each of the five putative communities in Tampa Bay. We focused on dolphins identified in previous surveys and, in particular, we targeted known members of each of these communities. Our field program supplemented genetic samples collected from dolphins in Tampa Bay during 2000 and 2002; we are now close to our goal of 30 samples from each community. We now hold 29 samples from mid-Tampa Bay, 13 from eastern Tampa Bay, 25 from Old Tampa Bay and more than 30 samples from each of the remaining two communities. The biopsy samples have been provided to NOAA Fisheries for genetic analyses.

From photo-identification images taken during 2003 and 2004, we have identified 227 individual dolphins. Of these, we matched 82 dolphins to our long-term Tampa Bay Photo-identification Catalog; 26 dolphins were photographed in both years. Nearly all the dolphins that we matched to the Tampa Bay Catalog were first identified during surveys we conducted between 1988-1993, indicating that a large proportion of these dolphins are still found in these waters.

We have now completed our photo-ID analysis to determine the identities of the 99 dolphins sampled from biopsy efforts in Tampa Bay from 2000-2004. Approximately half of the dolphins we sampled were matched to the Tampa Bay Catalog (the remaining dolphins will be new additions to the Tampa Bay Catalog, or the dorsal fin images did not meet our criteria for quality or distinctiveness). Our success in targeting individuals with longitudinal sighting histories was due to the skill of Brian Balmer and Anna Sellas, who conducted the biopsy sampling. The high number of sampled dolphins with previous sighting records is critical to our evaluation of community structure in Tampa Bay.

Once the genetic analyses are conducted, we will be able to determine how much gene flow occurs among the five communities in Tampa Bay. This will help us to better understand the fine-scale population structure of bottlenose dolphins in this region. In addition, the samples collected during these surveys will supplement the growing genetic catalog of dolphins along the west coast of Florida and provide information on population structure over a broad geographic area. This research was supported by NOAA Fisheries.