Mullin et al.: Cetaceans of the north-central Gulf of Mexico 



777 



these species inhabited a range of water depths 

 greater than 1,300 m. However, most sperm whales 

 inhabited a very narrow range of water depths (Fig. 

 2). The mean depth of sperm whale sightings had a 

 coefficient of variation of 0.27, the lowest of any spe- 

 cies or species group (Table 3). Bottlenose dolphins, 

 Atlantic spotted dolphins, and Risso's dolphins had 

 the shallowest mean water depths (<450 m) and in- 

 habited a range of water depths less than 1,100 m. 



Cuvier's beaked whales were only sighted at depths 

 greater than 900 m. 



Cetaceans were widely distributed between sea- 

 sons (Table 4). Five species or species groups were 

 sighted in every season of the year: sperm whales, 

 bottlenose dolphins, Risso's dolphins, Atlantic spotted 

 dolphins, and SSC dolphins. Pygmy and dwarf sperm 

 whales and pantropical spotted dolphins were sighted 

 in all seasons except winter and Cuvier's beaked whale, 



