Browsing by Subject "Western North Atlantic"

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    Estimating the Lower Temperature Limit of Bottlenose Dolphins Along the North Carolina Coast
    (2004) Shoemaker, Mandy
    During winter, the coastal ecotype of bottlenose dolphins are at the northern limit of their range off the coast of North Carolina. In this study, the distribution of coastal bottlenose dolphins in North Carolina was evaluated in response to variation in sea surface temperature to determine whether the distribution of dolphins was limited directly or indirectly by winter temperature minima. Observations of dolphin distribution were obtained from monthly aerial surveys conducted along the North Carolina coast during February 2000 through July 2001. Sea surface temperatures were obtained for each survey from NOAA’s Pathfinder satellite, using PO.DAAC Ocean ESIP Tool (POET). Where necessary, the sea surface temperature data was interpolated (krigged) over areas of cloud cover. The northern latitudinal and lower temperature distribution was determined for each survey. During winter months bottlenose dolphins were not distributed throughout their known range of 10-32 °C. Dolphins may be limited directly by temperature, due to the limits of their thermal neutral zone, or indirectly by temperature, through distribution of their prey. To determine how temperature is affecting dolphin distribution in the Western North Atlantic, future research should focus on determining the thermal neutral zone of dolphins in this region. In addition, it would be useful to build a model including other dynamic factors that may affect dolphin distribution. Although results suggest that more research is necessary, there is potential for using results from this type of analysis for management.
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    ItemOpen Access
    Population Genomics of Bottlenose Dolphins (Tursiops truncatus) in the Northwest Atlantic
    (2021-04-30) Shintaku, Nikki
    Bottlenose dolphins (Tursiops truncatus) are widely accepted as belonging to one of two ecotypes: offshore or inshore. These ecotypes exhibit remarkable differences in ecology, morphology, and genetic diversity. However, regional patterns of genetic differentiation and stock delineation remain poorly defined for both ecotypes. To improve our understanding of the population structures among these groups we investigated genome-wide genetic variation from 96 biopsy samples collected from bottlenose dolphins in inshore and offshore waters of the northwest Atlantic from North Carolina to Florida using restriction site associated DNA sequencing to infer population structure. Analysis of 14,783 single nucleotide polymorphisms revealed at least three genetically differentiated populations. Our results suggest an inshore population along North Carolina’s Outer Banks (n=32), an offshore population off the continental shelf break from North Carolina to Jacksonville, Florida (n= 38), and a shelf population off Jacksonville, Florida (n=26). Bayesian clustering showed significant admixture between the North Carolina and Jacksonville populations, providing potential evidence of historical or current gene flow. Most of the offshore samples were collected off Cape Hatteras, but this population also includes four individuals sampled beyond the continental shelf break off Jacksonville, FL, in close spatial proximity to shelf animals. This suggests a sharp distinction between shelf and offshore individuals structured by the shelf break itself. Such habitat heterogeneity is likely a driver in diversifying populations through influences on social behavior and foraging strategies. Our analyses provide fine-scale genetic resolution of bottlenose dolphin population differentiation in the Western North Atlantic. These results help inform conservation management and advance our understanding of processes that may drive the evolution of population genetic structure.