Examination of Bottlenose Dolphin (Tursiops truncatus) Abundances in Relation to Environmental Factors and Risks

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Huther, Kevin David
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The bottlenose dolphin (Tursiops truncatus ) is the most abundant marine mammal in coastal regions of the southeastern U.S. and Gulf of Mexico. Population abundances vary throughout their range and may be influenced by various environmental factors, including food availability and environmental quality. This study measured bottlenose dolphin abundances in Charleston, South Carolina against a variety of environmental factors. Metrics measured during 420 transects in the Ashley River and Wando River included dolphin abundances, boat traffic, water quality, sediment quality, and fish abundance. Three Multiple Linear Regression (MLR) Models were used to determine if environmental factors significantly affected dolphin abundance rates. A preliminary MLR (n=263 transects) revealed that dolphin abundance rates/study block were significantly related to boats/ study block and surface salinity. A Standardized MLR analysis (n=299) used dolphin and boat observations on a survey unit of effort basis , plus water temperature class categorizations and found that dolphin abundance rates/hour were significantly related to study blocks, surface water temperature class, and sediment quality. A Maximum Likelihood ANOVA (n=300) compared categorical classification of dolphins observation rates/hour, boat traffic rates/hour, sediment quality, and mean fish abundances/net, plus each environmental water quality metric. Dolphin abundances were only significantly related to water temperature class using this categorical MLR model.
Bottlenose dolphin -- Population viability analysis -- South Carolina -- Charleston; Bottlenose dolphin -- Effect of environment on -- South Carolina -- Charleston; Bottlenose dolphin -- Effect of temperature on -- South Carolina -- Charleston; Bottlenose dolphin -- Effect of water quality on -- South Carolina -- Charleston