Genetic Analysis of Bottlenose Dolphin Stock Structure in Tampa Bay
By Kim Urian, MSc

Echo on 20 August 2003 near Pinellas Point in Tampa Bay.

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 interested in determining how much gene flow occurs among these five communities and how well these 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 July and August 2004. 

 

To ensure representative coverage from all communities in Tampa Bay, our goal is to collect at least 30 genetic samples from each of the putative communities.  We focused our recent efforts in northern and western Tampa Bay, including the waters of Old Tampa Bay, Hillsborough Bay, and St. Petersburg.  Thanks to Eckerd College, we were able to keep our research boat at their facility, which greatly facilitated access to these areas.  We focused on dolphins identified in previous surveys and, in particular, we targeted known members of each of these communities.  Despite inclement weather, we collected 25 samples over the course of 7 field days.  Our success was due in large part to the skill of Brian Balmer, who conducted the biopsy sampling.  Our field program supplemented the genetic samples we collected from dolphins in Tampa Bay during 2000, 2002 and 2003; 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 and 25 from Old Tampa Bay and Hillsborough Bay.  We already have more than 30 samples from each of the remaining two communities, thanks largely to the previous efforts of Anna Sellas during her Master’s degree research.  Analysis of the digital images we obtained to determine the identities of the dolphins we sampled is nearly complete, and the biopsy samples have been provided to NOAA Fisheries for genetic analyses.

 

The preliminary results of the photo-analysis of dorsal fin images of dolphins photographed during the biopsy surveys in 2003 and 2004 show that a large proportion of dolphins first identified in Tampa Bay in the late 1980’s are still found in these waters.  And, of the images of the dolphins sampled that meet our criteria for dorsal fin distinctiveness and image quality, nearly half have been matched to our Tampa Bay photo-identification catalog.  Echo, one of two dolphins returned to Tampa Bay in 1990 after two years at a research facility in California, was photographed near downtown St. Petersburg on August 20, 2003, during our biopsy surveys; his most recent sighting by the SDRP was recorded in 1992 in Old Tampa Bay.

 

Once the genetic analysis is 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 the NOAA Fisheries, through the Chicago Zoological Society.