Integrating multiple techniques to identify stock boundaries of common bottlenose dolphins (Tursiops truncatus)

Abstract

1. Under US policy, a stock is a group of animals shown to be demographically independent from other such groups. Evidence of demographic delineations for marine mammal stocks is gained primarily through genetic analysis. However, additional techniques play an important role in determining fine-scale ranging patterns that can be used to define a stock's geographic boundaries. In cases where genetic studies have not yet been performed, movement and ranging pattern data are essential in identifying a targeted geographic region for tissue sampling and genetic studies.2. Photo-identification surveys, vessel-based radio telemetry, automated radio telemetry systems (ARTS), and satellite-linked telemetry are sampling techniques that have been used to determine common bottlenose dolphin ranging patterns and provide detailed insight into stock boundaries. The results of near simultaneous use of these sampling techniques are compared using data from a case study of bottlenose dolphins within the estuaries of southern Georgia.3. Satellite-linked and radio telemetry were determined to be useful sampling techniques for identification of shortterm ranging patterns. Satellite-linked telemetry had the second lowest cost per location ($122) and identified dolphin ranging patterns within and outside of the study area boundaries. Vessel-based radio telemetry was more costly ($195 per location) and had relatively limited tracking coverage. However, this sampling technique permitted visual observations of animal and tag condition. The combination of vessel-based radio telemetry and ARTS, which had the lowest cost per location ($34), was an effective method for determining ranging patterns of tagged individuals within and outside of the study area.4. Photo-identification surveys, relative to satellite-linked and radio telemetry, were not as efficient for determination of targeted individuals' short-term ranging patterns and had the highest cost per location of the four sampling techniques ($292). However, photo-identification is more effective than any other technique for compiling data on large numbers of individuals within a designated study area. Photo-identification surveys are essential for long-term monitoring and provide additional insight into dolphin stock structure that cannot be determined through telemetry alone.

Ranging patterns, spatial overlap, and association with dolphin morbillivirus exposure in common bottlenose dolphins (Tursiops truncatus) along the Georgia, USA coast

“…Stocks of marine mammals have been primarily delimited using genetic analyses (Rosel, Forgetta, & Dewar, 2005), but, additional sampling techniques such as photo-ID and telemetry have been used to test and assist in classification of individuals into their respective stocks (Balmer, Wells, Schwacke, et al, 2014b;Sveegaard et al, 2015). In the present study, both Estuary and Sound dolphins had small to moderate UDs (Tables 1 and 2; Figure 5b,c) and many individuals had long-term photo-ID sighting histories (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016), suggesting high site fidelity to localized BSEs and adjacent coastal waters.…”

Site fidelity, residency, and abundance of bottlenose dolphins (Tursiopssp.) in Adelaide's coastal waters, South Australia

“…Boat surveys indicate that sightings of bottlenose dolphins do occur across central and western GSV waters , as well as to areas further north of the Gulf (NZ, personal observations). The integration of multiple techniques, such as photo-identification, genetics, telemetry, and stable isotopes (e.g., Ansmann et al 2015, Balmer et al 2014, Browning et al 2014, Ansmann et al 2012 to identify population boundaries, together with survey efforts that cover a larger sampling area, will provide a better understanding of bottlenose dolphin movement patterns and home ranges within GSV.…”

Survey of antibiotic-resistant bacteria isolated from bottlenose dolphins Tursiops truncatus in the southeastern USA

“…Dolphins were sampled from estuarine populations that generally stay in localized areas without traveling great distances (Balmer et al 2008, 2014, Wells 2009, Waring et al 2011. Genetic analysis has shown distinct stock structures within various estuaries that have been sampled (Sellas et al 2005).…”

“…Genetic analysis has shown distinct stock structures within various estuaries that have been sampled (Sellas et al 2005). Additionally, some of the animals captured were tagged with radio and/or satellite-linked transmitters and showed only localized movement patterns over the duration of the tag (see Balmer et al 2008Balmer et al , 2014. Although the geographic ranges of the dolphin populations are fairly well characterized, the range of the fish that might comprise their diets is not known.…”