Patterns of Activity and Space Utilization of Lemon Sharks, Negaprion Brevirostris, in a Shallow Bahamian Lagoon

In an initial telemetry study we examined patterns of activity and space-utilization by the lemon shark, Negaprion brevirostris, using manual ultrasonic tracking. Nine sharks were tracked intermittently for periods of 1–8 days: The longest continuous tracking segment lasted 101 h. Total activity space per individual ranged from 9–93 km², as determined by the maximum-area polygon method. All sharks tracked at Bimini showed some degree of site attachment. The two largest sharks tracked elsewhere, did not remain in the area of tagging but made deepwater excursions. At Bimini, sharks tracked during the day were located eastward of their nighttime activity spaces. They moved westward over the flats at sunset and back eastward at sunrise. These sharks appeared to use the sun as an orientation cue. The tracks of two sharks fitted with speed-sensing transmitters demonstrated that swimming speeds were two times faster than the corresponding point-to-point rates of movement. The highest rates of movement were recorded at evening and morning twilight periods: the average nighttime rate was higher than the daytime rate—although statistical significance could not be established. Underwater and aerial observations showed lemon sharks to be associated with each other, with other sharks and with teleosts. Findings are interpreted in light of current information on space utilization, diel activity, social grouping, and energetics.