Fin whales are found world wide except in polar waters. Three separate populations, one in the Northwestern Atlantic, the North Pacific, and the Southern Hemisphere, do not interbreed. The speculation is winter migration to the water of the subtropics for mating and calving and to colder areas for summer feeding and dispersing in deep ocean waters.
The fin whale is streamlined with a v-shaped, asymmetrical head and light gray to brownish black on its back and sides. The underside of the body, flippers, and fluke are white. The lower jaw is creamy white on the right side and gray or black on the left. There is asymmetrical coloration to the baleen plates and it is reversed on the tongue. A long thin body with a slightly curved dorsal fin located far back on the body, the whale has small tapered flippers and the pointed wide fluke is notched in the center. There are fifty to one hundred throat grooves, which expand during feeding, on the lower jaw. A sleek fast animal whose huge size, fifty-nine to eighty-eight feet and thirty to eighty tons, is exceeded only by that of the blue whale.
Fin whales are sexually mature at six to ten years, happening before reaching physical maturity. Calves are born during the winter season at three to four year intervals. Gestation is twelve months; born they are fourteen to twenty feet in length and weigh two tons. Calves nurse for six to eight months and weaned when they reach thirty to forty feet in length. Primary solitary animals, groups of three to four are common. Their sounds carry far, and use this to stay in touch with one another. A sequence of five to eight blows seventy seconds apart is followed by a long dive up to eighteen hundred feet.
The fin whale feeds on a wide variety of small schooling fish, notably herring, capelin, and sun lance, with some krill. Observed circling schools of fish at high speed, rolling the fish into compact balls, and feeding by lunging, mouth agape, to engulf the fish. Some of these lunges may involve bursts of speed of up to twenty-five knots. They can consume up to two tons of food a day.
The speed of the fin whale and the open sea gave protection from the early whalers. Once whalers had virtually depleted the blue whales the whaling industry turned to the abundant fin whale as a replacement. Today, it is thought there are fifty-five thousand worldwide, and they have been placed under full protection. Still, threats exist, such as fish net entanglement and the possible resumption of whaling.