Sei Whale

Latin: Balaenoptera borealis
English: Sei whale

The sei is the middle whale in sizes in the series of balaenopterid rorquals. (From smallest to largest: minke, Bryde's, sea, fin, blue whale). It looks like a typical rorqual, with the characteristic narrow snout; the erect, curved-back dorsal fin, and the slender flippers.

At a distance, sei whales are easily confused with the rorquals closest to it in size: Bryde's whales and fin whales. However, Bryde's whales have three ridges on top of the head, while the sei whale has a single ridge from the tip of the rostrum to the blowhole.

Doc - 30 dec. 2012 11-48

Bryde's whale Sei whale

The sei whale is smaller then the fin whale, and unlike the fin, has symmetrical coloring on either side of its head.

Feeding behavior is varied. Like right whales, sei whales skim for copepods, swimming steadily through the water to catch their food, rather than lunging and gulping like other rorquals.

Sometimes great numbers of sei whales follow prey into prime fishing areas. They usually travel in groups of two to five individuals, altough on good feeding grounds, many more, often well spaced, are observed.
Sei whales are rarely seen because of their preference for offshore waters.

North Atlantic Society 2012