Sei Whales

Balaenoptera borealis

Sei whales are some of the fastest swimmers of the whale community. They're currently endangered, mainly because they were a target of commercial whalers in the 1950s and 1960s.

Sei whale mother and calf seen from the air

Sei whale mother and calf seen from the air. © Christin Khan, NOAA / NEFSC. Creative Commons.

Estimated Population: Unknown, endangered.

Ways to identify this species: slim and streamlined, bluish grey body with a white underside.

Sei Whale Biology

  • Sei whales are migratory and feed in Arctic waters during the summer and subtropical waters during the winter, where they remain mainly offshore.
  • Sei whales are the third largest baleen whales. Adult males measure up to 55 feet and weigh up to 25 tons. Females are usually a bit larger.
  • Sei whales are one of the fastest swimming cetaceans and can reach speeds of 31 mph.
  • An average sei whale eats about 1,984 pounds of food each day, eating mostly small fish and other organisms.

Threats to Sei Whales

  • After fin and blue whale populations were exhausted, Sei whales became the target of whalers in the 1950s and 1960s and the population was severely depleted.
  • Today, sei whales still face threats from hunting and entanglement in nets.

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