Controlling for Survey Effort Is Worth the Effort: Comparing Bottlenose Dolphin (Tursiops truncatus) Habitat Use Between Standardized and Opportunistic Photographic-Identification Surveys

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Although opportunistic data collected from wild-life ecotours can provide useful information on opportumarine mammal distribution and behavior, concerns exist about whether resultant analyses have diminished accuracy due to spatial bias. To address these concerns, this study compared common bottlenose dolphin (Tursiops truncatus) habitat use results derived from standardized boat-based phopresencetographic-identification surveys and opportunistic Getisphotographic-identification surveys conducted during wildlife ecotours in Roanoke Sound, North Carolina. The main objectives of this study were to (1) identify areas of importance to dolphins, (2) identify activities (feed, mill, social, and travel) most often observed in these areas, and (3) determine the consistency of habitat use results between standardized and opportunistic surveys. Standardized survey hot spots for feeding and travel were located in southern Roanoke Sound according to the hot spot (Getis-Ord Gi*) spatial statistic. Conversely, opportunistic survey hot spots for feeding and travel were detected in central Roanoke Sound near the wildlife ecotour launch site. Opportunistic survey effort was concentrated around the ecotour launch site which introduced spatial bias by overestimating dolphin density in this area. These hot spot location differences between survey methods indicate that opportunistic survey results are affected by spagenertial bias which can lead to inaccurate conclusions about dolphin habitat use. Hot spot results of standardized data without survey effort supported the conclusion that spatial bias affected opportunistic habitat use results. This study provides direct comparison of standardized and opportumarine nistic datasets and demonstrates the importance of controlling for survey effort when examining marine mammal distribution and habitat use.

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Aquatic Mammals





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