The sei whale (/ seɪ / SAY, [4] Norwegian: [sæɪ]; Balaenoptera borealis) is a baleen whale. It is one of ten rorqual species, and the third-largest member after the blue and fin whales. It can grow to 19.5 m (64 ft) in length and weigh as much as 28 t (28 long tons; 31 short tons). Two subspecies are recognized: B. b. borealis and B. b. schlegelii.

Sei whales occur in subtropical, temperate, and subpolar waters around the world. Often found with pollock in Norway, the name "sei" comes from the Norwegian word for pollock, "seje." Learn more about sei whales.

Sei whales (pronounced ‘say’ whales) are large, slim marine mammals, sometimes measuring up to 20m in length. They are incredibly fast swimmers and are often considered one of the fastest of all whale species.

The sei whale is one of the fastest whales, reaching speeds of up to 30 miles per hour. Sei whales inhabit all oceans and adjoining seas except in tropical and polar regions. Like other great whales, they prefer to spend the summer feeding in cooler waters before migrating to warmer waters to breed and give birth to their calves.

sei whale, (Balaenoptera borealis), species of baleen whale capable of short bursts of speed that make it the swiftest of the rorquals. Usually attaining a length of about 13–15 metres (43–49 feet), this cetacean is bluish gray or blackish above with paler underparts and a relatively large hook-shaped (falcate) dorsal fin.

The Sei whale (Balaenoptera borealis) is a baleen whale, the third-largest rorqual after the Blue whale and the Fin whale. It inhabits most oceans and adjoining seas and prefers deep offshore waters. The whale's name comes from the Norwegian word for pollock, a fish that appears off the coast of Norway at the same time of the year as the Sei whale.

The third largest whale species after blue whales and fin whales, sei whales are one of the most poorly understood of all baleen whales. Although they were heavily hunted in the modern whaling era, their current distribution, migration patterns and behaviour are not well studied.

Sei (pronounced ‘say') whales are the third largest of the baleen whales, reaching about 16 metres and 25 tonnes. While Sei whales are often pictured as uniformly coloured, they often have very subtle, beautiful swirling markings on their skin.

Sei Whales are the 4 th largest rorqual (the largest group of baleen whales) after the Blue Whale, the Fin Whale, and the Humpback Whale. The “Sei” in “Sei Whale” comes from the Norwegian word for Pollock, a type of fish.

Body: Sei whales’ bodies are primarily dark, with differing amounts of white on their pectoral fins, their bellies, and the undersides of their flukes (tails). Size: Length: 40-60 feet, Weight: Up to 50 tons. Source: International Whaling Commission. Associations: Sei whales are usually observed alone or in small groups of two to five animals.