Abstract: Management and conservation decisions affecting coastal bottlenose dolphins (Tursiops truncatus) benefit from consideration of population parameters such as population size, stability, distribution, habitat use, and gene flow, as well as social organization patterns. Long-term study of bottlenose dolphins in inshore areas suggested population units are based on the social structure and habitat use of resident dolphins, but little is known about dolphins in open coastal waters just offshore. This study examined the stock structure of bottlenose dolphins in an open coastal habitat, made comparisons to adjacent inshore population units, and evaluated interactions between dolphins in these two regions. We conducted a 14-mo boatbased photographic identification study along 93 km of the west coast of Florida, extending 9.3 km offshore. We identified 580 individual dolphins in the study area and designated these individuals as "Inshore" (long-term bay residents) or "Gulf" (observed predominantly in Gulf waters) regional population units. Dolphins used the Gulf habitat differently, depending on season and regional designation. Sighting frequencies of "Gulf" dolphins suggested patterns of seasonal residency, extended geographic range out of the study area, or transience, with fewer individuals displaying yearround residence. In general, dolphins in this coastal region appear to divide into overlapping communities defined by preferred geographic ranges, habitat use patterns, and social associations.

Key Words: bottlenose dolphin, Tursiops truncatus, Florida, Gulf of Mexico, stock structure, habitat use, distribution

Document Type: Research article

DOI: 10.1578/AM.32.2.2006.212

Page Numbers: 212-222

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