Do major ecological disturbances impact resident dolphin populations?  The Sarasota Dolphin Research Program was in a unique position to evaluate this question as both Hurricane Charley in August 2004 and a severe red tide in 2005 impacted Charlotte Harbor and Pine Island Sound.  These combined events may have affected habitat health, including prey fish availability, in ways that could have short or long-term implications for the bottlenose dolphins that use this estuary.

Mangrove damage from Hurricane Charley in August 2004  is still evident on Cayo Costa in March  2007, two and a half years later.

The SDRP has been working with the dolphin population in these areas since its start in 1970, with photographic identifications since 1982, and baseline data on dolphin abundance, reproductive rates, distribution, and site fidelity from intensive seasonal surveys immediately prior to the 2004 hurricane.  Knowledge of the status of the dolphin population units inhabiting Charlotte Harbor and Pine Island Sound is important for protecting dolphin stocks in the area, and follow-up surveys would provide a unique opportunity to investigate the adaptability of these animals to large scale disturbances. 

     With funding from Harbor Branch Oceanographic Institution’s “Protect Wild Dolphins” program, we were able to conduct a comprehensive, multi-week, photographic-identification survey in Charlotte Harbor and Pine Island Sound in September 2006, at the same scale as our 2001-2003 September surveys.  This allowed us to examine trends in abundance, distribution and reproductive rates pre-and post-Hurricane Charley.  These surveys also allowed us to gather additional sighting information on distinctively marked individuals to examine long-term and seasonal site fidelity and reproductive status of females.

“SPKY” has been observed in Pine Island Sound 16 times between 1996 and 2007, both before and after Hurricane Charley.

     Hurricane Charley devastated the shoreline, terrestrial flora, and man-made structures along its path through Charlotte Harbor.  However, two years later, and one year after a major red tide event, we found no indications of impacts on the resident dolphins.  The 2006 abundance estimate was within 10% of the range of abundance estimates from previous years, by all measures.  Similarly, reproductive rates were within the previously-documented range for the area. Of the 206 identifiable dolphins seen 10 or more times, 94% were found in the same region of Charlotte Harbor two years after the storm as before.  The level of resilience documented for the Charlotte Harbor dolphins provides important perspective for evaluating the threats to dolphin populations from a variety of natural and anthropogenic sources.  Many additional funding sources contributed to this project and the earlier surveys, including: Mote Scientific Foundation, the Chicago Zoological Society, Mote Marine Laboratory, NOAA’s Fisheries Service, Dolphin Biology Research Institute, and Earthwatch Institute.