Estimating Population Abundance of Atlantic Bottlenose Dolphins (Tursiops truncatus) in the Coastal Waters of Palm Beach County, Southeastern Florida

Atlantic bottlenose dolphins (Tursiops truncatus) are frequently observed in the coastal waters of Palm Beach County, Florida. In this study, mark -recapture surveys using photo-identification tech-niques were used to estimate population abun-dance of Atlantic bottlenose dolphins in this area for the first time. Surveys were conducted for 11 years, between 2005 and 2016, during which 384 individuals were identified and catalogued from distinctive nicks and notches on their dorsal fins. Each marked individual was documented an aver-age of 2.4 times (range 1 to 19). Low resighting rates and a constant rate of encounter with pre-viously unmarked individuals suggest that the population is open, comprising both residents and transients. The Jolly-Seber method was used to estimate population abundance. Estimates of abundance varied greatly in time with an overall average of 264 individuals and a 95% confidence interval of 162 to 366 (SE = 51.3), indicating a variable population size. As threats in the region continue to rise, such as overfishing, toxic algae blooms, and environmental pollutants, this under-studied population may be vulnerable to decline. A better understanding of the population dynam-ics could facilitate more effective conservation action.Peer reviewe

Site Fidelity of Coastal Bottlenose Dolphins (Tursiops truncatus) off Southeast Florida, USA

The coastal bottlenose dolphin is well studied throughout its natural range, though most research focuses on wide, well-protected habitats such as bays and estuaries rather than on narrow coastal sand banks. This study identifies a residential group of coastal bottlenose dolphins utilizing the northwestern Atlantic waters off the coast of Palm Beach County, Florida. From 2014 to 2020, 313 boat surveys were conducted, and 585 individual dolphins were identified using photo-identification. Using seasonal and annual resighting ratios, 24 dolphins were considered full-time residents, 66 dolphins were considered part-time residents, and 478 dolphins were transient. The presence of individuals with high site fidelity indicates that the region is used as a permanent habitat for some individuals, while the presence of transient animals may indicate a possible bridge between populations living to the north and south of the region

Abundance, Site Fidelity, and Association Patterns of Coastal Bottlenose Dolphins (Tursiops truncatus) off the Coast of Southeast Florida

The coastal ecotype of Atlantic bottlenose dolphins is one of the most thoroughly studied marine mammals, however a majority of these studies have occurred in protected habitats such as bays and estuaries. Very little work has been done on the population structure or site-fidelity in open-ocean habitats, and none has been done on the narrow, open-ocean sandbanks of South Florida, USA. Using photo-identification techniques, we analyzed the site-fidelity and association patterns of coastal bottlenose dolphins encountered along the coast of Palm Beach County, Florida. Between 2014 and 2019, we conducted 293 boat-surveys in the region, resulting in 226 encounters with coastal bottlenose dolphins. In total, we identified 727 unique individuals. Based on resighting ratios, 53 of these individuals were determined to be residential, using the study area year-round, 97 were regular or seasonal visitors, and 577 were sporadic visitors. These findings suggest that a small, permanent population exists within the study area, which shares the habitat with transitory individuals from other nearby populations. Preliminary association analysis indicates that there is a high level of social interaction between residential animals and visitors, making genetic or informational transfer likely. Many residential animals were also observed with neonates and calves, suggesting that the study area may serve as a nursing ground