Photo-identification of White-Beaked Dolphins and their relations with Atlantic Cod and sea surface temperature fluctuations in Skjálfandi Bay, Iceland
The master’s dissertation will take place on Monday 16th of December 2025 at 13:10 in Geitaskarði, Keldnaholti, Árleyni 22 112 Reykjavík and on Teams. Access a link to the dissertation here. The dissertation is open to all.
Supervisors
Marianne Helene Rasmussen, Director of Húsavík Research Centre, University of Iceland and Emmanuel Pagneux, Associate professor, Faculty of Environmental and Agricultural Sciences, Agricultural University of Iceland
Examiner
Katja Vinding Petersen, PhD, Lecturer in Polar biology and Biology of Marine Mammals at DIS - Study Abroad in Scandinavia. Lecturer at the University of Copenhagen, Department of Science Education.
Abstract
The present study explores the intricate ecological relationships between the White-Beaked Dolphin (Lagenorhynchus albirostris), one of its primary prey species, the Atlantic Cod (Gadus morhua), and the sea surface temperature fluctuations in Skjálfandi Bay, Iceland, over a period of ten years (2014-2024). The hypotheses suggest that an increase in sea surface temperature is expected to lead to a direct decline in the frequency of White-beaked Dolphins, and on the abundance of Atlantic Cod. Consequently, fluctuations in the abundance of Atlantic Cod may further indirectly impact the frequency and distribution of White-beaked Dolphins. The data on the White-Beaked Dolphin was collected during whale-watching tours, using photo identification and the frequency estimations were calculated using the Sighting Per Unit Effort (SPUE) index, which was analysed for potential correlation with cod landings data, collected from the national fishery database, and the mean annual sea surface temperature, which was calculated from the data collected from Grímsey Island. The results returned a clear seasonal pattern in dolphin presence, within the monthly SPUE, peaking in summer. However, the core hypotheses were not supported by the results. No statistically significant correlation was found between the yearly SPUE and either the cod landings (r = 0.212, p = 0.556) or the annual mean sea surface temperature (r = 0.230, p = 0.522), or also the dolphin identifications (r = -0.348, p = 0.294). Moreover, no further significant relationship was found between cod landings and the annual mean sea surface temperature (r = 0.410; p = 0.239). The lack of statistical significance in these relationships suggests that the ecological dynamics within Skjálfandi Bay, are more complex than initially anticipated. The findings might reflect resilience of the dolphins, possibly because of their dietary flexibility, or their belonging to a larger population that extends outside of the bay. In addition, it could also be the consequence of a temporal lag in the ecological response to the environmental change. This study highlights the crucial role of long-term monitoring in efficiently identifying and managing the impacts of the ongoing environmental changes that have and will have consequences on this fragile subarctic marine ecosystem.
