"Unlike other rorquals, Sei whales have a dolphin-like dorsal fin. They are also unusual in using two different methods to fill their mouths with water during feeding - they both gulp and skim-feed. During feeding, these whales can be found in large numbers, probably around concentrations of copepods, a crustacean they favor. Otherwise, they occur in smaller groups of six or less. The sei whale is endangered, and it has been protected by the International Whaling Commission since the mid-1980s. The common name, pronounced ""sigh,"" comes from the Norwegian word for codfish, which sei whales are known to eat. ""Rorqual"" is also a word of Scandinavian origin, meaning ""tubed,"" and refers to the grooved, expandable throats of the six species of whales in the family Balaenopteridae
Links:Mammal Species of the World More images, video and sound
Original description: "Lesson, René Primevère, 1828. Histoire naturelle générale et particulière des Mammifères et des Oiseaux découverts depuis 1788 jusqu'à nos jours, Baudoin Frères, Paris, 1:342,"