CHARACTERIZATION OF BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) USE OF RESTRICTED AREAS IN THE PAMLICO SOUND, NC

Abstract

In two areas of the Pamlico Sound, NC, the U.S. Marine Corps and other branches of the military conduct training activities that involve airborne deployment of ordnance. Entry into these areas is restricted, and as such, they have not been included in previous surveys for marine mammals or other protected species. Since July 2002, however, we have been contracted by the Marine Corps to conduct photo-identification surveys for bottlenose dolphins in two bombing ranges (BT-9 near Brandt Island Shoal and BT-11 in Rattan Bay) and waters surrounding the ranges. We observed 261 dolphins (in 10 sightings) during eight surveys conducted between July and December, 2002. Of the 261 animals photographed, 100 met our criteria for distinctiveness; these 100 identifications represent 96 individual dolphins, as four were seen on two occasions. We matched 39 dolphins to the Duke University Marine Laboratory/University of North Carolina at Wilmington dorsal fin photo-identification catalog, and we made 57 new identifications. Many dolphins (185) were sighted inside the bombing range boundaries, sometimes in close proximity to the bombing targets. The BT-9 range had a daily occupancy of 0.17 sightings/survey day and an hourly occupancy of 0.09 sightings/hour; BT-11’s daily occupancy was 0.38 sightings/survey day and its hourly occupancy was 0.31 sightings/hour; waters adjacent to the bombing ranges had a daily occupancy of 0.88 sightings/survey day and an hourly occupancy of 0.45 sightings/hour. The combined (bombing ranges and adjacent waters) mean dolphin group size was 26.1 ± 27.4 SD. The mean density of BT-9 (75 km2) was 0.11 dolphins/km2 and the mean density of BT-11 (11 km2) was 1.50 dolphins/km2. This work represents the first systematic survey effort for bottlenose dolphins in restricted areas of the Pamlico Sound.