Community structure and abundance of bottlenose dolphins Tursiops truncatus in coastal waters of the northeast Gulf of Mexico

Original provider: Reny Tyson, Duke University, and Brian Balmer, Chicago Zoological Society, c/o Mote Marine Laboratory Dataset credits: Reny Tyson, Duke University Brian Balmer, Chicago Zoological Society, c/o Mote Marine Laboratory Abstract: We examined bottlenose dolphin Tursiops truncatus community structure and abundance in the northeast Gulf of Mexico coastal waters stretching from St. Vincent Sound to Alligator Harbor, Florida, USA. Photographic-identification surveys were conducted between May 2004 and October 2006 to gain an understanding of dolphin distribution in this region. Dolphins were distributed year-round throughout the region; however, individual sighting records indicate that 2 parapatric dolphin communities exist. We conducted mark-recapture surveys using photographic-identification techniques to estimate the abundance of dolphins inhabiting the 2 areas these communities reside in: St. Vincent Sound/Apalachicola Bay, western; and St. George Sound/Alligator Harbor, eastern. Sighting records of individual dolphins from 2004 to 2008 support the existence of 2 communities in these areas; only 3.5% of distinctive dolphins photographed were seen in both western and eastern areas. The 2 communities differ in their structure: the eastern area supports a more transient population with 45.7% of distinctive dolphins photo graphed only once compared with 28.3% in the west. Independent estimates of abundance (N, 95% CI = [low, high]) were calculated using the Chapman modification of the Lincoln-Petersen method for June 2007 and for January and February 2008 for the eastern area (242 [141−343], 395 [273−516]) and for the western survey area (197 [130−264], 111 [71−150]), respectively. Our results serve as a baseline that can be used by the US National Marine Fisheries Service to manage bottlenose dolphins in this region.