The Fin Whale also called the finback whale, razor whale or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest animal in the world and second largest rorqual after the blue whale, growing to over 27 meters (89 ft) long and weighing nearly 74 tonnes (73 long tons; 82 short tons). The American naturalist Roy Chapman Andrews called the fin whale "the greyhound of the sea... for its beautiful, slender body is built like a racing yacht and the animal can surpass the speed of the fastest ocean steamship." There are at least two recognized subspecies: the fin whale of the North Atlantic, and the fin whale of the Southern Hemisphere.
The fin whale is usually distinguished by its tall spout, long back, prominent dorsal fin, and asymmetrical coloration. In the Northern Hemisphere, the average size of adult males and females is about 18.5 m (60 ft) and 20 m (65 ft), while in the Southern Hemisphere it is 20.5 m (67 ft) and 22 m (72 ft). In the North Atlantic, the longest reported was 24.5 m (80' 6" ft) (albeit what whalers' called a "bastard", a possible blue/fin hybrid), while the longest measured by True (1904) was 21.5 m (70' 8" ft), both females. In the North Pacific, the longest reported were 22.9 m (75 ft) for males and 24.7 m (81 ft) for females, while the longest reliably measured were 20.8 m (68 ft) and 22.9 m (75 ft), respectively. In the Southern Hemisphere, the longest reported for each sex were 25 m (82 ft) and 27.3 m (89' 6" ft), while the longest measured by Mackintosh and Wheeler (1929) were 22.4 m (73' 7" ft) and 24.5 m (80' 5" ft); although Major F. A. Spencer, while whaling inspector of the factory ship Southern Princess (1936-38), confirmed the length of a 25.9 m (85 ft) female caught in the Antarctic south of the southern Indian Ocean. The largest fin whale ever weighed (piecemeal) was a 22.7 m (74.5 ft) pregnant female caught by Japanese whalers in the Antarctic in 1948 which weighed 69.5 tonnes (68.4 long tons; 76.6 short tons), minus 6% for loss of fluids during the flensing process. It is estimated that an individual over 27 m (89 ft) would weigh in excess of 120 tonnes (120 long tons; 130 short tons). Full physical maturity is attained between 25 and 30 years. Fin whales live to 94 years of age, although specimens have been found aged at an estimated 135–140 years. A newborn fin whale measures about 6.5 meters (21 ft) in length and weighs approximately 1,800 kilograms (4,000 lb). The animal's large size aids in identification, and it is usually only confused with the blue whale, the Sei whale, or, in warmer waters, Bryde's whale. The fin whale is brownish to dark or light gray dorsally and white ventrally. It has paired blowholes on a prominent splashguard, and a broad, flat V-shaped rostrum. Two lighter-colored chevrons radiate from the eyes and curve forward, joining to form a V-shape oriented towards the head. Its lower jaw (and occasionally upper jaw) is white, while the left side of the jaw is gray or black.
It was hypothesized to have evolved because the whale swims on its right side when surface lunging and it often circles to the right while at the surface above a prey patch. However, the whales just as often circle to the left. The fin whale is one of the fastest cetaceans and can sustain speeds of 37 kilometers per hour (23 mph) and bursts in excess of 40 kilometers per hour (25 mph) have been recorded, earning the fin whale the nickname "the greyhound of the sea". Fin whales are more gregarious than other rorquals, and often live in groups of 6–10, although feeding groups may reach up to 100 animals.
The Fin whale is a filter-feeder, feeding on small schooling fish, squid, and crustaceans including copepods and krill. In the North Pacific, they feed on the krill species Euphausia pacifica, Thysanoessa inermis, T. longipes, T. spinifera, and Nyctiphanes simplex; large copepods (mainly Neocalanus cristatus); squid (Ommastrephes sloani pacificus); and schooling fish such as herring, Japanese sardine (Sardinella melanosticta), walleye pollock(Theragra chalcogramma), capelin, and anchovies (Engraulis mordax). In the North Atlantic, they prey on krill (Meganyctiphanes norvegica and T. inermis) and small schooling fish (e.g.capelin, Mallotus villosus; herring, Clupea harengus; and sand lance, Ammodytes spp.). In the Southern Ocean they mainly consume E. superba.
Like many large rorquals, the fin whale is a cosmopolitan species. It is found in all the world's major oceans, and in waters ranging from the polar to the tropical. It is absent only from waters close to the ice pack at both the north and south extremities and relatively small areas of water away from the large oceans, such as the Red Sea and the Baltic Sea. The highest population density occurs in temperate and cool waters. It is less densely populated in the warmest, equatorial regions. It prefers deep waters beyond the continental shelf to shallow waters.