Harbour Porpoise Abundance in Portugal over a 5-Year Period and Estimates of Potential Distribution

• Published in: Animals
• Main Authors: Andreia Torres-Pereira, Hélder Araújo, Fábio L. Matos, Jorge Bastos-Santos, Sara Sá, Marisa Ferreira, José Martínez-Cedeira, Alfredo López, Marina Sequeira, José Vingada, Catarina Eira
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: Iberian harbour porpoise; aerial surveys; abundance and density estimates; habitat suitability; environmental variables; conservation; Veterinary medicine; SF600-1100; Zoology; QL1-991; Harbour porpoise
• Online Access: https://doi.org/10.3390/ani12151935; https://doaj.org/article/76eb903e209f4097bf53b34f5cfd05ed

The Iberian porpoise population is small and under potentially unsustainable removal by fisheries bycatch. Recently, a marine Site of Community Importance (SCI) was legally approved in Portugal, but no measures ensued to promote porpoise conservation. Information about porpoise abundance and distribution is fundamental to guide any future conservation measures. Annual aerial surveys conducted between 2011 and 2015 show a low overall porpoise abundance and density (2254 individuals; 0.090 ind/km 2 , CV = 21.99%) in the Portuguese coast. The highest annual porpoise estimates were registered in 2013 (3207 individuals, 0.128 ind/km 2 ), followed by a sharp decrease in 2014 (1653 individuals, 0.066 ind/km 2 ). The porpoise density and abundance estimated in 2015 remained lower than the 2013 estimates. A potential distribution analysis of the Iberian porpoise population was performed using ensembles of small models (ESMs) with MaxEnt and showed that the overall habitat suitability is particularly high in the Portuguese northern area. The analysis also suggested a different pattern in porpoise potential distribution across the study period. These results emphasize the importance of further porpoise population assessments to fully understand the spatial and temporal porpoise habitat use in the Iberian Peninsula as well as the urgent need for on-site threat mitigation measures.