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Spatial ecology of harbour porpoises (Phocoena phocoena): supporting conservation in an ocean under pressure
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Date
2025-06-09
Authors
Goh, Tiffany
Journal Title
Journal ISSN
Volume Title
Publisher
University College Cork
Published Version
Abstract
Marine ecosystems are under increasing pressure from a growing range of human activities, including fishing, vessel traffic, and pollution, compounded by climate-driven changes in ocean conditions. These cumulative stressors have led to habitat degradation, biodiversity loss, and shifts in species distributions. The harbour porpoise (Phocoena phocoena), a small cetacean widely distributed in the northeast Atlantic and a protected species, is particularly vulnerable to such pressures, notably incidental bycatch in gillnet fisheries. In Irish waters, however, limited understanding of the species’ spatial ecology and a lack of systematic bycatch monitoring hinder effective conservation and management.
This thesis addresses key knowledge gaps in the spatial ecology and conservation of harbour porpoises within the Irish Exclusive Economic Zone. First, it identifies the optimal spatial and temporal scales at which environmental variables influence porpoise presence, demonstrating that selecting appropriate scales enhances model performance and reduces predictive uncertainty. Second, it applies these scales to model seasonal distributions of harbour porpoises, indicating a decline in the probability of sighting harbour porpoises and evidence of a contraction in distribution to the Irish Sea. Third, it develops a risk-based framework to assess seasonal bycatch risk by integrating predicted porpoise distributions with gillnet fishing effort. This approach provides a spatially explicit means of identifying high-risk areas in the absence of direct bycatch data and highlights regions where risk persists across years. Finally, spatial prioritisation analyses were conducted to inform conservation planning, integrating ecological, legal, and socio-economic data to evaluate how porpoise conservation targets could be achieved within existing and future marine-use contexts.
Collectively, this research advances the understanding of harbour porpoise spatial ecology and demonstrates how multi-scale habitat modelling, risk assessment, and spatial planning can be integrated to inform management. The findings provide an evidence base to refine or expand Special Areas of Conservation, guide bycatch monitoring and mitigation, and support the broader goal of safeguarding marine biodiversity in Irish waters.
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Controlled Access
Keywords
Aerial surveys , Species distribution models , Harbour porpoise conservation , Spatial prioritisation , Bycatch risk assessment
Citation
Goh, T. 2025. Spatial ecology of harbour porpoises (Phocoena phocoena): supporting conservation in an ocean under pressure. PhD Thesis, University College Cork.