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| Azorean Species | Sei whale - Balaenoptera borealis - Baleia sardinheira

Scientific Name: Balaenoptera borealis (Lesson, 1828).

Common Name (UK, FR, PT, ES, DE): Sei whale. Rorqual de Rudolphi. Baleia sardinheira. Rorqual boreal. Seiwal. (Carwardine 1995, Jefferson et al. 2015).

Short Species description: In this rorqual (baleen whale) the dorsal fin rises at a steep angle and it is big. Sei whales have a pointed rostrum with a single and prominent ridge. Coloration is dark-grey with a whitish area on the belly. Their size can be up to 18 m and 45.000 kg. They have an average of 350 baleen plates hanging from the upper jaw that they use to filter the food. They produce a blow up to 3 m. They live at least 50 years. (Carwardine 1995, Jefferson et al. 2015).

Population status: Endangered by IUCN status. (Jefferson et al. 2015).

Occurrence in the Azores (including season): July-September.

Usually found in pairs or groups of 3 animals but sometimes alone. Mostly transiting or sometimes feeding during summertime. Rarely stop.

Habitat Use: their distribution is poorly understood as they can be confused with Bryde's whales. The species appears to occur largely unpredictable patterns called "irruptive". What is known is that they are largely open ocean whales and they occur from the tropics to polar zones in both hemispheres and in all three major oceans. (Jefferson et al. 2015). In the Atlantic, they seem to migrate from the coasts of Mauritania off Africa, towards the Atlantic coasts of North America.

Pod Size: 1-5 individuals.

Typical Behavior: Fast swimmers (25 km/h). When they move slowly, they show the blowhole and dorsal fin often visible at the same time but they never show the tail while diving. (Jefferson et al. 2015).


Cerwardine, M. (1995). Baleias Golfinhos e Botos; O guia com imagens de todos os cetáceos do mundo. London: Bertrand Editora.

Jefferson, T.A., Webber, M.A., Pitman, R.L. (2015). Marine Mammals of the World; A Comprehensive Guide of Their Identification. 2nd edition. London: El Sevier.


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