Spatial Assessment of Bottlenose Dolphins (Tursiops truncatus) in Charleston Harbor, South Carolina: Influence of Biotic and Abiotic Factors
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The Charleston Estuarine System Stock (CESS) of bottlenose dolphins (<i>Tursiops truncatus</i>) has been the focus of long-term population monitoring for the past twenty years with an added emphasis on health assessment research for the past ten. Through a series of photo-identification studies, abundance and survivability estimates have been determined for this population, which is known to exhibit high site fidelity within this area. However, fine-scale distribution, movement patterns, and the driving forces behind these patterns have been left largely uninvestigated. Furthermore, high levels of both legacy persistent organohalogen contaminants (POCs) and emerging POCs have been reported in dolphins in this population and less than 50% of dolphins examined were considered healthy. Using historical photo-id data and GIS analysis, the present study identified areas of high residency within the harbor, as well as movement patterns across sexes and seasons. Multiple hot spots were identified for this population, with the most significant being an area of great overlap near the mouth of the harbor. Fine-scale distribution varied across sexes as well as seasons. Significant correlations between distribution and salinity, temperature, and depth were identified, with the direction of these correlations varying by season. Additionally, the fine-scale distribution of dolphins with known health statuses and contaminant levels was identified and correlated to sediment contaminant levels throughout the estuary. While distinct high residency areas were identified between groups with varying health statuses, no significant distinctions in distribution or correlations with environmental contaminants were found. Understanding the distribution patterns and contaminant exposures of these highly mobile marine predators requires complex analyses, but may provide insight into the health of the estuary as a whole.