Over the weekend, Fisheries and Oceans Canada Cetacean Research Program researchers spotted a large aggregation of 25-30 sei whales (Balaenoptera borealis) while conducting a marine mammal survey 300 kilometres offshore of Vancouver Island.  The team is part of a multi-week survey to estimate marine mammal populations in Canada’s Pacific.  It was a once-in-a-lifetime event for whale researchers aboard the CCG Vessel John P Tully, one that many thought they would never get to experience. 

Brianna Wright

The Canadian Coast Guard ship JP Tully

Why was this particular sighting so significant? 

Sei whales were heavily targeted by whaling operations in the 1950s to 70s, after the preferred larger baleen whale species – such as blue and fin whales – had been depleted. From 1917 until whaling was banned in 1975, it is estimated that over 4,000 sei whales were killed and processed by Canadian, Japanese, and Soviet whalers in Canada’s offshore waters.  There have been only 10 documented sightings of sei whales in Canadian Pacific waters since the 1960s, so to encounter a large aggregation of this critically endangered species is extraordinary! The infrequency of both visual and acoustic observations suggests that their population in Canadian waters is below 250 mature individuals. 

Sei whales are the third largest of the baleen whales. They are typically 14-15m in length.  They are a dark to bluish grey, with many grey to white scars.  The dorsal fin is taller than that of a blue or fin whale and is usually falcate.  In British Columbia, they are easily confused with fin whales. Fin whales will typically have asymmetrical colouration on their lower jaw (the left side will be dark and the right side will be white), whereas the jaw of sei whale will be dark on both sides.  When a sei whale surfaces, the dorsal fin is usually visible at the same time as the blowholes, while a fin whale’s dorsal fin appears after the blowholes have submerged.   

Although they are no longer targeted by whaling in Canadian waters, there is still a long road to recovery for this species.  Threats include ship strikesunderwater noise, and climate change, which could affect the abundance of their zooplankton prey.  There is also growing concern about the increasing concentration of plastic pollution in Canadian Pacific waters, which are known to affect large baleen whales and other marine animals though ingestion or entanglement 

Fun facts about sei whales: 

  • Sei whales are the third largest of the baleen whales.  They are typically 14-15m long and weigh around 20 tonnes. Females are generally slightly larger than males.
  • They are exceptionally fast swimmers!  It has been estimated that a sei whale could reach speeds of 30 knots (~56 kilometres per hour). 
  • While sei whales are known to gulp feed like other rorqual* whales, they also employ a “skimming strategy”, filtering zooplankton from the water while swimming with their mouth open.  The fringes on their baleen plates are finer than other rorqual whales, which allows them to skim the surface for small copepods that may only be a few millimetres in length.   
  • The sei whale is a cosmopolitan species, found in all of the oceans of the world. They favour temperate, deep offshore waters. Like other baleen whales, sei whales migrate from low-latitude wintering areas to high-latitude summer feeding grounds. 
  • Sei whales are usually found in small groups of two to five, although many more may be seen together when food is plentiful.
  • The whale’s name comes from the Norweigan word for pollock, a fish that appears off the coast of Norway at the same time of the year as the sei whale.  

* Rorqual whales have long pleats from their lower jaw to their abdomen that allow the throat to expand to engulf huge amounts of food-filled water while feeding.  Blue whales, fin whales, humpback whales, minke whales, and sei whales are rorqual whales. 

Doug Davis

Humpback whales lunging up through a school of herring.  Rorqual whales, like humpbacks and sei whales, have long pleats from their lower jaw to their abdomen that allow their throats to expand and engulf huge amounts of food-filled water while feeding.

How can you help sei whales? 

  • Be Plastic Wise: Protect the ocean by reducing your consumption of single use plastics.  Take the Plastic Wise Challenge.   
  • Organize a shoreline cleanup in your community:  Check out the Great Canadian Shoreline Cleanup for more information. 
  • Send a Sighting, Save a Whale:  Sei whales and other species of whales are susceptible to ship strikes and disturbance from vessels.  You can help protect these animals, while contributing to conservation-based research, by reporting any whales you see through Ocean Wise’s WhaleReport, available online or through your app store (available for android and iOS devices).  Your reports are used to inform large ships of whales in their vicinity so that they can take measures such as slowing down or diverting course to reduce the risk of collision or disturbance.  If you think you’ve seen a sei whale, make sure to take as many pictures as you can and report the sighting immediately, providing as many details as possible.  Learn more here!  


Fisheries and Oceans Canada. 2017. Action Plan for Blue, Fin, Sei and North Pacific Right Whales (Balaenoptera musculus, B. physalus, B. borealis, and Eubalaena japonica) in Canadian Pacific Waters. Species at Risk Act Action Plan Series. Fisheries and Oceans Canada, Ottawa. iv + 28 pp. 

Ford, J.K.B. 2014. Marine Mammals of British Columbia (6th ed.). Victoria, British Columbia: Royal BC Museum. 

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