Dear colleagues,

We are pleased to share our latest publication on the environmental drivers of bottlenose dolphin occurrence in a dynamic river-estuarine ecosystem.

Beyond improving our understanding of bottlenose dolphin ecology in estuarine environments, the study illustrates how long-term passive acoustic monitoring can reveal predator–prey relationships that are difficult to detect through visual surveys alone. The association between dolphin occurrence and European eel migration is also consistent with long-standing observations from local fishers, providing an interesting example of convergence between quantitative ecological data and local ecological knowledge.

Authors: Olga Mosca, Severine Methion, Xose Antonio Padin, Adrian Martinez-Fernandez, Miguel Gilcoto, Bruno Diaz Lopez (2026). Passive acoustic monitoring reveals seasonal bottlenose dolphin (Tursiops truncatus) presence in coastal estuarine waters, Estuarine, Coastal and Shelf Science, Volume 341,110159

https://doi.org/10.1016/j.ecss.2026.110159.

Abstract: Understanding how animals use their habitat range is central to ecology, particularly for behaviourally plastic species. For coastal top predators such as bottlenose dolphins, estuaries are important as productive, prey-rich environments that may serve as key areas for calving and foraging. Simultaneously, estuaries are focal points of human activity, exposing marine fauna to anthropogenic stressors, making it essential to understand how dolphins use these habitats for effective conservation planning. This study uses Passive Acoustic Monitoring (PAM) to investigate factors influencing bottlenose dolphin acoustic presence in a high-impact coastal estuary. Acoustic recordings were collected from a fixed monitoring platform at Ulla River mouth (Galicia, NW Spain) between 2017 and 2022. Dolphin whistle presence was used as a proxy for acoustic activity and analysed in relation to a suite of environmental, oceanographic, temporal, and biological variables. In total, 22,241 h of recordings were processed using PAMGuard and analysed using Generalised Additive Models (GAMs) with penalised (shrinkage) variable selection. Results show that dolphin acoustic presence occurred year-round throughout the study period, with significant predictors including water temperature, wave power, chlorophyll-a concentration, and diadromous fish landings. Many of these covariates displayed strong seasonal patterns, suggesting that dolphin acoustic presence in the estuary is plausibly linked to the seasonal availability of prey, potentially including diadromous fish. By integrating long-term acoustic data with environmental variables, this study provides new insights into dolphin acoustic presence in a riverine habitat that is otherwise difficult to monitor, offering valuable information for conservation in a human-impacted location.

The paper is available (free access) here:
https://authors.elsevier.com/c/1nYeF~1MBywvm

We hope you find it of interest.

Best regards,

Bruno (on behalf of the authors)

Bruno Díaz López Ph.D

Chief biologist and Director

The Bottlenose Dolphin Research Institute BDRI - www.thebdri.com

Avenida Beiramar 192, O Grove 36980, Pontevedra, Spain

Tel. 0034 684248552

he/him/his

ResearchGate - GoogleScholar -https://orcid.org/0000-0002-0388-3289

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