Alternate Title

Distribution, Habitat Partitioning, and Abundance of Atlantic Spotted Dolphins, Bottlenose Dolphins, and Loggerhead Sea Turtles on the Eastern Gulf of Mexico Continental Shelf


We surveyed cetaceans and marine turtles from Nov. 1998 to Nov. 2000 along a series of prescribed transects between Tampa Bay and Charlotte Harbor, Florida, and between the coast and the 180-m isobath. Vertical profiles of temperature, salinity, and chlorophyll concentration were collected at 65 stations, and continuous surface data on these variables and transmittance were collected while underway. Habitat partitioning among Atlantic spotted dolphins (Stenella frontalis), bottlenose dolphins (Tursiops truncatus), and loggerhead sea turtles (Caretta caretta) was examined by canonical correspondence analyses of environmental characteristics at sighting locations. Environmental characteristics and primary productivity of S. frontalis and T. truncatus habitat on the eastern Gulf of Mexico continental shelf significantly differed. In shelf waters shallower than 20 m, T. truncatus were the dominant cetacean species, whereas S. frontalis were the most common shelf species at depths of 20-180 m. Environmental preferences of C. caretta were intermediate between the two dolphin species and showed no apparent relationship with depth. The continental shelf in the eastern Gulf of Mexico is broad, with distances from coast to slope as great as 200 km. Although S. frontalis habitat has elsewhere been described as ubiquitous over the shelf, our data suggest that S. frontalis in the eastern Gulf of Mexico prefer midshelf habitat.