Habitat use by iberian harbour porpoises: ecological and human factors

The Iberian harbour porpoise (Phocoena phocoena meridionalis) population faces unique challenges, characterized by low population size and limited genetic diversity, underscoring the urgency of conservation efforts. However, a dearth of ecological information on this population hampers targeted conservation measures. This study addresses this knowledge gap by assessing the environmental and anthropogenic factors influencing the habitat use of Iberian harbour porpoises. Utilizing data collected from 195 daily boat surveys spanning 8 years along the north-western coast of Spain, we observed 287 harbour porpoise groups comprising 1383 individuals. Our analysis revealed a wide distribution of harbour porpoises along the continental shelf of the north-western Iberian Peninsula. Notably, this species exhibited a preference for areas characterized by high productivity, influenced by seasonal coastal upwelling phenomena and tidal flow. Our results emphasize the positive correlation between the presence of fishing boats and porpoise habitat use, highlighting the risks associated with bycatch in gear such as bottom-set gillnets and trammel nets, and the need for comprehensive mitigation measures. Additionally, our findings underscore the necessity for comprehensive conservation strategies to address risks associated with marine traffic and habitat alteration due to the expanding development of offshore wind farms in the region. This research also establishes a baseline for future environmental monitoring programs, contributing to the long-term conservation and management of the Iberian harbour porpoise population.