Sei Whale


  • Status
  • Scientific Name
    Balaenoptera borealis
  • Weight
    About 20 tons
  • Length
    45 to 66 feet
  • Habitats

The sei whale is one of the fastest whales, reaching speeds of up to 30 miles per hour. Sei whales inhabit all oceans and adjoining seas except in tropical and polar regions. Like other great whales, they prefer to spend the summer feeding in cooler waters before migrating to warmer waters to breed and give birth to their calves.

New regulations help protect whales from entanglement in fishing gear in the Indian Ocean

WWF and other partners are working to prevent the setting of nets around whales and other cetaceans and improve the reporting of when these mammals become entangled.

A pygmy blue whale swims in a bright blue ocean

Why They Matter

  • Whales are at the top of the food chain and have an important role in the overall health of the marine environment. They are also highly vulnerable to human activities in the ocean. The sei whale became a major target for commercial whaling after the preferred stocks of blue and fin whales had been depleted. Today, although commercial whaling has been officially halted, the species is subject to "scientific whaling" by Japan—that is, killing whales for scientific research. 


  • Extinction Risk Endangered
    1. EX

      No reasonable doubt that the last individual has died

    2. EW
      Extinct in the Wild

      Known only to survive in cultivation, in captivity or as a naturalised population

    3. CR
      Critically Endangered

      Facing an extremely high risk of extinction in the Wild

    4. EN

      Facing a high risk of extinction in the Wild

    5. VU

      Facing a high risk of extinction in the Wild

    6. NT
      Near Threatened

      Likely to qualify for a threatened category in the near future

    7. LC
      Least Concern

      Does not qualify for Critically Endangered, Endangered, Vulnerable, or Near Threatened

Whaler, Norway

Whaler demonstrating how to use a harpoon gun.

While the sei whale has been hunted by humans since the 1860s, it wasn't until the 1950s and 1960s and the declining availability of blue and fin whales that the killings seriously expanded.

Since 1986, the International Whaling Commission (IWC) has officially halted all commercial whaling. However, 50 sei whales are killed annually by Japanese whalers in the North Pacific under Japan's "scientific" whaling program.

Whales are threatened by climate change and can also be harmed by pollution, shipping strikes and entanglement in fishing gear.


What WWF Is Doing

Field research, Argentina

The International Whaling Commission (IWC) is the body charged with regulating whaling and addressing the vast number of other threats to whales, dolphins and porpoises in our oceans such as shipping, climate change and bycatch. WWF works to make the IWC more effective in reducing threats to whales.


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