Ecology of the short-beaked common dolphin (Delphinus delphis) along the north-west coast of Spain
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Full Text E-thesis
Date
2020
Authors
Giralt Paradell, Oriol
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Publisher
University College Cork
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Abstract
Studying the ecology of a species requires a comprehensive approach encompassing several techniques aimed at understanding different aspects of their ecology such as distribution and habitat, their role in the ecosystem and interactions with the other species. In a constantly changing world, in which (coastal) marine ecosystems are consistently being impacted by human activities, the improved knowledge on marine top predators ecology is of key importance in order to develop effective conservation measures and management plans. In this regard, this thesis uses different approaches to better understand the ecology of a marine top predator, the short-beaked common dolphin (Delphinus delphis, Linnaeus 1758) in Galician waters, North-West Spain, and explores its conservation needs. To do so, the study combines data collected during 273 days at sea, covering a total distance of 9,417 km between March 2014 and October 2017, with information gathered by several studies conducted in the area in previous years. The data collected over four years contributed to improving our understanding of the environmental, topographic and anthropogenic factors influencing the dolphins distribution, and highlighted the areas entailing the most and least suitable habitats for the species and the areas with a higher degree of overlap with fishing activities. This information was combined with regional fisheries information to build an Ecopath with Ecosim framework to study the role of common dolphins in the ecosystem and its relationships with the other species. Furthermore, the approach provided information about the ecological impacts of fisheries on common dolphins and other cetacean species in the area. Results point out the importance of the continental shelf waters for the species and highlight the species vulnerability to direct and especially indirect impacts caused by fisheries, principally trawling activities. In this regard, the study predicts an important population decrease for common dolphins if fishing effort is increased. An interdisciplinary approach combining distribution and habitat use studies with the analysis of trophic food webs was used to explore the overlap between common dolphins and fisheries and the direct and indirect impacts caused on this cetacean species, providing new information on the indirect effects of fisheries on common dolphins, which will be of great value in the development of effective conservation measures and fishing management plans.
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Keywords
Delphinus delphis , Short-beaked common dolphin , Ecology , Modelling , SDMs , ENFA , GAMs , Ecopath with Ecosim , Fisheries impact , Galicia , NW Spain , NE Atlantic
Citation
Giralt Paradell, O. 2020. Ecology of the short-beaked common dolphin (Delphinus delphis) along the north-west coast of Spain. PhD Thesis, University College Cork.