maximum depth of 120 m (Map 57). For 84% of these observed groups, water depth was 

 also less than 50 m. The two leatherback turtles seen during August were in water with a 

 depth of 50 to 60 m (Map 58). The four green turtles recorded in SFLA during August 

 were in waters 20 to 50 m deep (x = 45.0 m). 



During November loggerheads were most common (80%) in nearshore waters (i.e. 

 to 30 m deep) in the eastern and northeastern extremes of the survey subunit. Some 

 individuals, sighted in deeper waters (30 to 70 m) near the southwestern corner of the 

 subunit may have been transients between the Florida coast and the Dry Tortugas. 



GROUP SIZE 



Mammals 



The mean group size for mammal species apparently varied on a geographic and 

 seasonal basis. Tables 21 through 24 list the mean group sizes of mammals seen in the 

 various survey subunits. 



The mean group size for bottlenose dolphins (x = 17.4 individuals per group) was 

 higher in NTEX during August than in all other subunits and seasons. Mean group sizes 

 for other subunits ranged from 3.2 to 11.7. Group sizes of bottlenose dolphins, and to a 

 lesser extent other dolphins, tended to be lower in November than in August. 



Saddleback dolphins and those of the genus Stenella tended to occur in large 

 groups whereas other mammals were in noticeably smaller groups. During August striped 

 dolphins in the NFL A subunit were observed in larger groups (x =32.4) than those in SFLA 

 (x = 1.4). 



The only sperm whales observed were seen in the western Gulf of Mexico during 

 August. A pod of three adults and one young was seen in NTEX, and a single adult was 

 noted in STEX. 



Birds 



The group sizes of birds varied widely depending on the species, subunit, and 

 season. Some species such as gulls and shearwaters tend to feed in large groups when 

 food is abundant or concentrated in patches. Group sizes for Cory's shearwaters and 

 unidentified gulls were noticeably high in STEX during August. Black terns also occurred 

 in large groups (x = 38.9) in STEX during August. Shearwaters and black terns were not 

 observed during November surveys in STEX. The mean group size of royal terns did not 

 increase when the number of sightings quadrupled in NFLA from August to November, 

 but did increase in SFLA during the same period. Many species of birds move and feed as 

 solitary individuals and in small groups but accounted for a high number of sightings. 

 Tables 25 through 28 list the mean group sizes of birds seen in the various survey 

 subunits. 



The relationship of group size to individual environmental variables such as fish 

 schools, sargassum windrows, and ocean depth is an important investigative perspective 

 that requires repeated observations over a seasonal time span. Additional analyses of 

 group size data are essential to estimation of abundance and movements. 



49 



