Spatial and temporal variation in the occurrence of bottlenose dolphins in the Chesapeake Bay, USA, using citizen science sighting data

Chesapeake DolphinWatch sightings data (2017-2022): Citizen science reports of bottlenose dolphins observed in the Chesapeake Bay, USA

Atlantic bottlenose dolphins are extensively studied, though little has been published regarding their occurrence patterns in the large and highly urbanized estuary of the Chesapeake Bay, USA. To address this knowledge gap, the Chesapeake DolphinWatch project was initiated in the summer of 2017. Utilizing a citizen science (also known as volunteer science) methodology, members of the public were encouraged to report dolphin sightings through a specialized mobile (iOS and Android) and web-based (https://chesapeakedolphinwatch.org) application. This approach ensured extensive, yet non-invasive and financially-efficient, data collection. The dataset presented here includes bottlenose dolphin sighting reports submitted to Chesapeake DolphinWatch by citizen scientists over five years; from June 28, 2017 through December 9, 2022. These data have been quality checked by researchers at the University of Maryland Center for Environmental Science's (UMCES) Chesapeake Biological Laboratory (CBL) in Solomons, Maryland (USA). This dataset holds potential for various applications, such as analyzing the spatiotemporal patterns of dolphin presence within the Chesapeake Bay, investigating the behavior and movements of bottlenose dolphins in the mid-Atlantic, and serving as a comparative benchmark for studies in other estuarine systems. By integrating community engagement with technological platforms, the provided data showcases the invaluable role of citizen science in advancing marine ecological research.

Vocal signatures affected by population identity and environmental sound levels

Passive acoustic monitoring has improved our understanding of vocalizing organisms in remote habitats and during all weather conditions. Many vocally active species are highly mobile, and their populations overlap. However, distinct vocalizations allow the tracking and discrimination of individuals or populations. Using signature whistles, the individually distinct calls of bottlenose dolphins, we calculated a minimum abundance of individuals, characterized and compared signature whistles from five locations, and determined reoccurrences of individuals throughout the Mid-Atlantic Bight and Chesapeake Bay, USA. We identified 1,888 signature whistles in which the duration, number of extrema, start, end, and minimum frequencies of signature whistles varied significantly by site. All characteristics of signature whistles were deemed important for determining from which site the whistle originated and due to the distinct signature whistle characteristics and lack of spatial mixing of the dolphins detected at the Offshore site, we suspect that these dolphins are of a different population than those at the Coastal and Bay sites. Signature whistles were also found to be shorter when sound levels were higher. Using only the passively recorded vocalizations of this marine top predator, we obtained information about its population and how it is affected by ambient sound levels, which will increase as offshore wind energy is developed. In this rapidly developing area, these calls offer critical management insights for this protected species.