Abstract
Cetaceans are critical indicators of ecosystem health, yet face significant threats from overfishing, habitat loss, and climate change. Key conservation strategies in the EU include Marine Protected Areas (MPAs), the Natura 2000 network, and Important Marine Mammal Areas (IMMAs). This study investigates cetacean distribution along the Portuguese coast from 2004 to 2020, focusing on their presence inside and outside three protected areas, the Sites of Community Importance (SCI) of Maceda-Praia da Vieira and Costa Sudoeste, the Arrábida MPA. We analyzed five cetacean species— bottlenose dolphin (Tursiops truncatus ), common dolphin ( Delphinus delphis ), Risso’s dolphin ( Grampus griseus ), striped dolphin ( Stenella coeruleoalba ) and pilot whale ( Globicephala spp.)—modeling their total number of sightings and individuals using Generalized Additive Models (GAMs). Through these models, we assessed the impact of habitat-based, geographical, and MPA-related predictors on cetacean presence. Findings showed higher cetacean prevalence in non-protected areas, followed by Maceda-Praia da Vieira and Costa Sudoeste SCIs, with no sightings in Arrábida SCI. Habitat variables had a stronger impact on encounter rates than MPA status. These findings underscore the need to identify and protect specific, data-driven areas of special importance for cetacean communities.