COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus) Southern Georgia Estuarine System Stock

STOCK DEFINITION AND GEOGRAPHIC RANGE The coastal morphotype of common bottlenose dolphins is continuously distributed along the Atlantic coast south of Long Island, New York, to the Florida peninsula, including inshore waters of the bays, sounds and estuaries. Several lines of evidence support a distinction between dolphins inhabiting coastal waters near the shore and those present in the inshore waters of the bays, sounds and estuaries. Photo-identification (photo-ID) and genetic studies support the existence of resident estuarine animals in several inshore areas of the southeastern United States (Caldwell 2001; Gubbins 2002; Zolman 2002; Mazzoil et al. 2005; Litz et al. 2012), and similar patterns have been observed in bays and estuaries along the Gulf of Mexico coast (Wells et al. 1987; Balmer et al., 2008). Recent genetic analyses using both mitochondrial DNA and nuclear microsatellite markers found significant differentiation between animals biopsied in coastal and estuarine areas along the Atlantic coast (Rosel et al. 2009), and between those biopsied in coastal and estuarine waters at the same latitude (NMFS unpublished data). Similar results have been found off the west coast of Florida (Sellas et al. 2005). Coastal southern Georgia contains an extensive estuarine tidal marsh system, punctuated with several river drainages. There is moderate development throughout the region, along with the larger industrialized area around Brunswick, Georgia, which includes 4 sites on the Environmental Protection Agency’s National Priority List (NPL) of hazardous waste sites (EPA 2008). Balmer et al. (2011) conducted photo-ID studies between 2004 and 2009 in two field sites in south-central Georgia, one in the Turtle/Brunswick River estuary (TBRE) and the second north of the Altamaha River/Sound including the Sapelo Island National Estuarine Research Reserve and extending north to Sapelo Sound. Photo-ID data revealed strong site fidelity to the two regions and supported Altamaha Sound as an appropriate boundary between the two sites as 85.4% of animals identified did not cross Altamaha Sound (Balmer et al. 2013). Just over half the animals that did range across Altamaha Sound had low site fidelity and were believed to be members of the South Carolina/Georgia Coastal Stock. Genetic analysis of mitochondrial DNA control region sequences and microsatellite markers of dolphins biopsied in southern Georgia showed significant genetic differentiation from animals biopsied in northern Georgia and southern South Carolina estuaries as well as from animals biopsied in coastal waters >1 km from shore at the same latitude (NMFS unpublished data). In addition, bottlenose dolphins in the TBRE exhibit contaminant burdens consistent with long-term fidelity to the TBRE (Pulster and Maruya 2008; Balmer et al. 2011; Kucklick et al. 2011). Therefore, the Southern Georgia Estuarine System Stock (SGES) is bounded in the south by the Georgia/Florida border at the Cumberland River out through Cumberland Sound and in the north by the Altamaha River out through Altamaha Sound inclusive, and encompasses all estuarine waters in between, including but not limited to the Intracoastal Waterway, Hampton River, St. Andrew and Jekyll Sounds and their tributaries, St. Simons Sound and tributaries, and the TBRE system (Figure 1). Although the majority of photo-ID survey effort by Balmer et al. (2013) was conducted within the estuaries, opportunistic surveys extending along the coast and satellite-linked telemetry of three individuals suggested that animals within the SGES had ranging patterns that extended into the coastal waters of the TBRE. Thus, the nearshore (≤ 1km from shore) coastal waters from Altamaha Sound to Cumberland Sound were included in the SGES Stock boundaries. The southern boundary abuts the northern boundary of the Jacksonville Estuarine System Stock, previously defined based on photo-ID and genetic data (Caldwell 2001). The northern boundary is defined based on continuity of estuarine habitat, evidence for significantly lower contaminant levels in dolphins from the Sapleo Island area (Balmer et al. 2011) and a genetic discontinuity between dolphins sampled in southern Georgia and those sampled in Charleston, South Carolina (Rosel et al. 2009). These boundaries are subject to change upon further study of dolphin residency patterns in estuarine waters of central and northern Georgia. Dolphins residing in the estuaries north of this stock between Altamaha Sound, Georgia, and Wassaw Sound, Georgia, are not currently covered in any stock assessment report. Based on photo-ID surveys and telemetry, Balmer et al. (2013) identified dolphins with high site-fidelity to the estuarine waters from Altamaha Sound north to and including Sapelo Sound. These animals did not have extended ranging patterns outside of this region, suggesting that they may represent a separate stock and should not be included in the SGES or Northern Georgia/Southern South Carolina Estuarine System (NGSSCES) Stocks. Future research focusing on the waters north of Sapelo Sound to the southern boundary of the NGSSCES (Ossabaw Sound) is necessary to identify the ranging patterns of