Sei Whales

The sei whale is a sleek, fast-swimming baleen whale found in oceans worldwide, closely related to the fin and Bryde's whale.

Classification

Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Cetacea
Family	Balaenopteridae
Genus	Balaenoptera
Species	borealis

Description

Sei whales are dark steel-gray with a lighter underside, sleek and streamlined, with a tall, curved dorsal fin set well forward compared to other rorquals. Their name comes from the Norwegian word for pollock, "seje," because the whales were often seen in Norwegian waters alongside pollock shoals.

Size & speed

Sei whales measure 40 to 60 feet in length and weigh 20 to 30 tons. They are one of the fastest cetaceans, capable of short bursts over 30 miles per hour.

Habitat

Sei whales are found in all major oceans, generally favoring deep offshore waters and avoiding both polar ice and the warmest tropical waters.

Diet

Unlike many rorquals that lunge-feed, sei whales often skim the surface with their mouths open to strain copepods and other tiny crustaceans, though they also take krill and small schooling fish.

Social structure

Sei whales are usually seen alone or in small groups of two to five, occasionally gathering in larger numbers on rich feeding grounds.

Conservation

Sei whale populations were sharply reduced by 20th-century whaling and the species remains endangered, with slow recovery since international whaling protections took effect.