Marine Mammal Research & Conservation

Sei whale


Sei whale (Balaenoptera borealis)

Group formation: Solitary (mother-calf pair, small groups 2-5)

Size: males 17 m, females 19.5 m, calf 4.5 m

Weight: 45 t, calf 1 t

Spout: 3-4 m, “bushy”

Age: 50-70 yrs

Sexual maturity: unknown ca 6-12 yrs

Gestation: 10-13 mths, with 2-3 yrs in between

Weaning: 6-9 months

Diet: small schooling fish, krill, copepods, and zooplankton

Distribution: Worldwide in all oceans, but rarely in polar or tropical waters

Chile: seen along the coast of Chile (feeding grounds in Aysen), not well known

Population size: unknown

Conservation Status: Endangered A1ad ver 3.1, Pop. trend: unknown

Threats: Vessel collisions, chemical and plastic pollution, man-made noise impacts (seismic surveys, military sonar), entanglement in fishing gear, over fishing

Vocalizations: voicesinthesea-sei-whale