Temporal Variation in Atlantic Spotted Dolphin (Stenella frontalis) and Bottlenose Dolphin (Tursiops truncatus) Densities on the West Florida Continental Shelf

Abstract: We surveyed Atlantic spotted dolphins (Stenella frontalis) and bottlenose dolphins (Tursiops truncatus) in an area of the west Florida continental shelf (82° to 84.5° W and 26° to 28° N) from November 1998 to December 2001. Objectives were to estimate relative abundances of these two species and test for seasonal and interannual variations in distribution. Monthly surveys were conducted over a three-year period between the coast and the 180 m depth contour. Abundances of Atlantic spotted dolphins and bottlenose dolphins were estimated using the software program Distance. Sightings from monthly surveys were pooled by years and by seasons within a year. Significant seasonal variations in Atlantic spotted dolphin densities were repeated across years, with lower abundances during the warm season (June-October), and higher densities during the cool season (November-May). Atlantic spotted dolphin densities significantly decreased during 2000, while bottlenose dolphin density trends were not apparent. These trends continued into 2001, suggesting differential species response to environmental variation may affect changes in cetacean community structure over relatively short temporal scales.

Key Words: seasonality, habitat, density, Gulf of Mexico, Atlantic spotted dolphin, Stenella frontalis, bottlenose dolphin, Tursiops truncates

Document Type: Research article

DOI: 10.1578/AM.30.3.2004.380

Page Numbers: 380-390

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