The waters stretching from St. Vincent Sound to Alligator Harbor in the Big Bend of Florida represent one of the least understood areas of the state in regards to bottlenose dolphins. Recent large scale mortality events, together with an increasing potential for human impacts in this area, led to studies of abundance and stock structure of dolphins in this region by Dr. Doug Nowacek at Florida State University. Nowacek’s group, working in collaboration with the SDRP and other colleagues, documented the year-round presence of dolphins throughout the area although with seasonal and annual variations. The present study implemented mark-recapture surveys using photographic-identification techniques to estimate the abundance of dolphins in this region in the summer of 2007 and winter of 2008. Because the region is large and recent work here suggests that at least two distinct communities exist in these waters, the region was divided into the two areas in which these communities appear to reside (St. Vincent Sound/Apalachicola Bay and St. George Sound/Alligator Harbor, Figure 1), and independent estimates of abundance were calculated for each area and each season.

Figure 1

        Mark-recapture estimates of abundance were similar within each survey area for each season: in the St. Vincent Sound/Apalachicola Bay survey area 182 ± 58 animals inhabited the survey area in the summer and 178 ± 77 animals in the winter; in the St. George Sound/Alligator Harbor survey area 365 ± 164 animals inhabited the survey area in the summer and 359 ± 87 animals in the winter. Results from this study provided further evidence that at least two communities reside in these waters as only 2.4% of animals identified during the study were found in both survey areas.
        The results from this study can be used by the NOAA Fisheries Service to aid in their stock assessment process and help manage animals in this region more appropriately under the Marine Mammal Protection Act. These results can also be used as a baseline from which future modifications of the ecosystem might be gauged if/when potential threats (such as disrupted flow of the Apalachicola River, increased development and activity by humans, and future UMEs, etc.) occur.
        This project was funded by the Florida State University Department of Oceanography and the HBOI Protect Wild Dolphins Grant 2004-2006 & 2005-2012. In addition, some logistical and field support and project guidance were provided by the Chicago Zoological Society through Brian Balmer and Randall Wells.