Harbour porpoise
Scientific Name: Phocoena phocoena (Linnaeus, 1758).
Common Name: Harbour porpoise.
Classification: Odontoceti, family Phoeconidae.
Physical notes: Up to 2 m and 70 kg with robust bodies and rounded head. It is easily distinguished by its triangular fin and brownish pattern.
Distribution and habitat use: Found in cold temperate to sub-polar waters of the Northern Hemisphere. They are usually found in continental shelf waters (up to 200 m deep), although they occasionally travel over deeper offshore waters. They can enter ports, estuaries and large rivers. Resident species, found all year in Sagres.
Group size: Normally seen singly or in small groups of less than 8 individuals, with some records of up to several hundred animals. Group composition is relatively fluid, but usually segregated by gender, age, and reproductive condition.
Life span: 10-20 years.
Gestation period: ca. 10 – 11 months. Juveniles reach maturity at 3 – 5 years. Births take place from May till September. Juveniles are weaned after 7 – 10 months.
Diet and Feeding: Depending on the region, feed opportunistically on schooling fish, cephalopods, and small crustaceans. Usually forage near seabed. They can dive up to 220 m and hold their breath up to 12 min.
Typical Behaviour: Very “shy”, almost always avoiding boats. Usually all that is seen is the small triangular dorsal fin breaking the surface.
Population: ca. 1 million worldwide (based on available data). Population trend unknown.
Threats: Habitat degradation, prey depletion, pollution, and by-catch which mostly lead to death. It is the second species with the biggest stranding record on the Portuguese coast (after common dolphin).
IUCN status: Least concern for overall species worldwide (2020). Few European sub-populations are Critically Endangered, including Portuguese (2023), which dramatically dropped in genetic diversity in just 25 years, indicating significant risk of extinction.
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Ferreira, M., Eira, C., López, A., & Sequeira, M. (2023). Phocoena phocoena boto. In Mathias, M. L. (coord.), Fonseca, C., Rodrigues, L., Grilo, C., Lopes-Fernandes, M., Palmeirim, J. M., Santos-Reis, M., Alves, P. C., Cabral, J. A., Ferreira, M., Mira, A., Eira, C., Negrões, N., Paupério, J., Pita, R., Rainho, A., Rosalino, L. M., Tapisso, J. T., & Vingada, J. (eds.): Livro Vermelho dos Mamíferos de Portugal Continental. Fciências.ID, ICNF, Lisboa.
Shirihai, H. (2006). Whales, Dolphins and Seals: A Field Guide to the Marine Mammals of the World. Bloomsbury Wildlife. London, United Kingdom.
Still, R., Harrop, H., Stenton, T., & Dias, L. (2019). Europe’s Sea Mammals Including the Azores, Madeira, the Canary Islands and Cape Verde: A field guide to the whales, dolphins, porpoises and seals. Princeton University Press.