Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


A study of channel utilization and behavior of subadult loggerhead turtles was conducted in the St. Mary's River entrance channel area, Georgia. A total of 38 loggerheads were captured by trawling and instrumented with radio and depth sensitive sonic tags from April to November 1993. Turtles were monitored for 6 to 36 hours continuously for approximately 30 days in the spring (13), summer (13), and fall (14). On a daily basis turtles generally confined their diving activity to one location for one to twelve hours in 10 to 20 m water depths then moved 1 to 5 kilometers to a new location. Overall the turtles spent only a small percent of time in/near the channel. Duration of diving variables varied widely among and between individuals. The loggerhead turtles spent a small percent of time and short durations at the sea surface and large percent of time and long durations associated with the sea floor. A turtle would typically surface 1-4 times per hour. In general, bottom durations, submergence durations, and dive cycle durations were longer at night than during the day, with twilight durations intermediate between the two. Turtles surfaced more frequently during the day than at night. No day/night pattern was observed for surface duration, descent duration, ascent duration, ascent rate, and descent rate. Ascent duration was longer and ascent rate slower than descent duration and descent rate, respectively. Mean surface durations were greater in the spring than summer and fall. Surface/submergence frequency was less in the fall than in spring and summer. Bottom durations, submergence durations, and dive cycle durations were longer in the fall than in the spring or summer. Surface durations, descent durations, ascent durations, ascent rates, and descent rates did not differ seasonally. In the spring, summer, and fall loggerhead turtles spent most of their time on the sea floor outside the channel, dove more actively during the day than at night, and remained in one location for up to 12 hours at 10-20 m water depths.



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