COMMON BOTTLENOSE DOLPHIN (Tursiops truncatus truncatus) Indian River Lagoon 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 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 areas of the southeastern United States (e.g., 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 (e.g., 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coast (Rosel et al. 2009), and between those biopsied in coastal and estuarine waters at the same latitude (NMFS unpublished data).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 reported for the west coast of Florida (Sellas et al. 2005). Multiple studies utilizing varying methods such as freeze-branding, photo-ID and radio telemetry support the designation of bottlenose dolphins in the Indian River Lagoon (IRL) as a distinct stock. Odell and Asper (1990) reported that none of the 133 freeze-branded dolphins from the IRL were observed outside of the system during their 4-year monitoring period from 1979 to 1982 and suggested that there may be an additional discrete group of dolphins in the southern end of the system. A stranded dolphin from the IRL that was rehabilitated, freeze-branded and released into the IRL was recaptured 14 years later in the IRL during a health assessment project (Mazzoil et al. 2008b). Photo-ID studies have provided evidence that some dolphins in the IRL exhibit both short-term and longterm site fidelity (Mazzoil et al. 2005; Mazzoil et al. 2008a). During a 5-year study (1996-2001) in the IRL, 67 individual dolphins were sighted 8 or more times, which included 11 dolphins freeze-branded from the Odell and Asper (1990) study that were sighted at least once (Mazzoil et al. 2005). In addition, Mazzoil et al. (2008a) suggested that at least 3 different dolphin communities exist within the IRL based on analyses of photo-ID data. Radio-tracking of 2 rehabilitated dolphins stranded in the IRL indicated that neither dolphin left the IRL from the time of release until their deaths in 100 days and 7days, respectively (Mazzoil et al. 2008b). A photo-ID study conducted from 2006-2008 provided evidence for spatial separation and minimal degree of movement between dolphins in the IRL and those occurring in the nearshore coastal waters of the Atlantic Ocean between Sebastian and St. Lucie Inlets (Mazzoil et al. 2008a). However, results from aerial surveys to estimate abundance during 20022004 (Durden et al. 2011, described under "Population Size" below) seem to contradict an exclusively resident population, and rather suggest movements of IRL dolphins between adjacent estuarine and/or coastal waters. There is still a need to better understand movement patterns between the IRL and adjacent coastal and estuarine waters. The boundaries of this stock are subject to change upon further study. The Indian River Lagoon Estuarine System (IRLES) Stock on the Atlantic coast of Florida extends from Ponce de Leon Inlet in the north to Jupiter Inlet in the south and encompasses all estuarine waters in between (Figure 1), including but not limited to the Intracoastal Waterway, Mosquito Lagoon, Indian River, Banana River and the St. Lucie Estuary. Five inlets and the Cape Canaveral Locks connect the IRLES to the Atlantic Ocean. This definition of the IRLES has been used by a number of researchers (e.g., Kent et al. 2008) and is the most expansive definition. Some researchers truncate the southern border at the St. Lucie Inlet. Dolphins residing within estuaries north and south of this stock are currently not included in any Stock Assessment Report. There are insufficient data to determine whether animals south of the IRLES exhibit affiliation to the Biscayne Bay Stock or are simply transient animals associated with coastal stocks. Similarly, there are insufficient data to determine whether animals in estuarine waters north of the IRLES exhibit affiliation to the IRLES Stock or to the Jacksonville Estuarine System Stock to the north or are simply transients. There is relatively limited estuarine habitat along the coastline south of the IRLES but some potentially suitable habitat north of the IRLES. Further research is needed to establish affinities of dolphins in these regions. It should be noted that during 2007-2011, there were 36 stranded bottlenose dolphins in the region north of the IRLES in enclosed waters. Evidence of human interactions was detected for 11 of these stranded dolphins, 3 of which involved fishery interactions with hook and line gear, including an animal disentangled from recreational gear and released alive without serious injury (Maze-Foley and Garrison in prep.). Seven of the 11 human interactions involved boat collisions, and the remaining human interaction was a stranding with signs of mutilation. There was 1 estuarine