Sei Whale
Balenoptera borealis


Scientific Name: Balenoptera borealis

Other Names: Pollack Whale, Coalfish Whale, Sardine Whale, Japan Finner, Rudolph's Rorqual

Suborder: Mysteciti

Family: Balaenopteridae

The Sei Whale is slender with a dark bluish-grey to black upperbody and a white underside. Lower jaw sometimes darker but this is not often visible. Head V-shaped with a single, central rostrum ridge and dorsal fin tall and set well back.

Maximum Length
Adult: 12 - 21 m
Calf: 4.5 - 5 m

Maximum Weight
Adult: 15.2 - 30.4 tons
Calf: 0.65 tons

Sei Whale Ecology

Range: Tropical, temperate and subactic oceans

Usual Habitat: Generally found in deep oceanic waters but in some areas, including Trinidad and Tobago, they are also found in shallow coastal waters.

Usual group size: Alone or in pairs, sometimes up to 5 and rarely groups of 30 - 50.

Main Diet: Zooplankton, small schooling fish and squid

Local population: Unknown 

 Global range of the Sei Whale

Sei Whales are likely to be found in the dark blue areas

 Conservation Information

Protection and Conservation Status

IUCN Conservation Status: 
Sei Whales are listed as "Endangered" on the IUCN red list.

SPAW Protocol:  Sei Whales are cetaceans, which are listed under Annex II of the SPAW protocol. As such they require total protection under article 11 of this protocol which prohibits the "taking, possession, killing and commercial trade of the species, their parts or products". The SPAW protocol was created to help with the implementation and promotion of the Ramsar Convention and the Convention on Biological Diversity. The Annexes of the SPAW protocol can be found here.

Local Laws: Cetaceans are protected under the Conservation of Wildlife Act of Trinidad and Tobago which offers protection to all species not listed under the second or third schedules of this act.    

Reports of Sei Whales in Trinidad and Tobago
There are currently no reports of this species in Trinidad and Tobago.

The above information was obtained from the following sources:

  • A Princeton Field Guide: Whales Dolphins and Other Marine Mammals of the World by Hadoram Shirihai and Brett Jarrett (2006)
  • Smithsonian Handbooks: Whales Dolphins and Porpoises by Mark Carwardine and illustrated by Martin Camm (2002)
  • The Whale and Dolphin Conservation Society's Species Guide at
  • The IUCN Redlist at
  • The SPAW protocol Annexes with links available at,83

We would like to thank the following people for the use of the art work and photographs:

  • Al√ęsha Naranjit (Illustration of Sei Whale)
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