<P> The sei whale (/ ˈseɪ / or / ˈsaɪ /) (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 . It avoids polar and tropical waters and semienclosed bodies of water . The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical waters, with a lifespan of 70 years . </P> <P> Reaching 19.5 m (64 ft) long and weighing as much as 28 t (28 long tons; 31 short tons), the sei whale consumes an average of 900 kg (2,000 lb) of food every day; its diet consists primarily of copepods, krill, and other zooplankton . It is among the fastest of all cetaceans, and can reach speeds of up to 50 km / h (31 mph) (27 knots) over short distances . 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 . </P> <P> Following large - scale commercial whaling during the late 19th and 20th centuries, when over 255,000 whales were taken, the sei whale is now internationally protected, although limited hunting occurs under a controversial research program conducted by Japan . As of 2008, its worldwide population was about 80,000, nearly a third of its prewhaling population . </P> <P> Sei is the Norwegian word for pollock, also referred to as coalfish, a close relative of codfish . Sei whales appeared off the coast of Norway at the same time as the pollock, both coming to feed on the abundant plankton . The specific name is the Latin word borealis, meaning northern . In the Pacific, the whale has been called the Japan finner; "finner" was a common term used to refer to rorquals . In Japanese, the whale was called iwashi kujira, or sardine whale, a name originally applied to Bryde's whales by early Japanese whalers . Later, as modern whaling shifted to Sanriku--where both species occur--it was confused for the sei whale . Now the term only applies to the latter species . It has also been referred to as the lesser fin whale because it somewhat resembles the fin whale . The American naturalist Roy Chapman Andrews compared the sei whale to the cheetah, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives". </P>

What is the population of the sei whale