The fin whale has firstly been described in 1675 by Frederik Martens and secondly in 1725 by Paul Dudley. Linnaeus then followed these previous descriptions and created Balaena physalus in 1758. Balaenoptera physalus was later named by Lacépède.
Size, shape and distinctive characteristics
Fin whales are the second-largest animals on Earth. At birth, they are between 6-6.5 metres (20-21 feet) long. An adult typically grows to 18-22 metres (59-72 feet), but in the southern hemisphere, females may reach 26 metres (nearly 86 feet). Weight: 2-3 tonnes when born. Adults can weigh from 30-80 tonnes, though southern females may weigh up to 120 tonnes. Fin whales are large, long and streamlined with silvery grey, dark grey or brownish black skin. They have a V-shaped head which is flat on top; a single ridge extends from the blowhole to the tip of the rostrum (upper jaw). The fin whale has a prominent, slightly falcate (curved) dorsal fin located far back on its body. Its flippers are small and tapered, and its fluke is wide, pointed at the tips, and notched in the center. Despite its size, the fin whale is sometimes called the ‘greyhound of the sea' because of its fast swimming speed; average cruising speed ranges between 5-8 nautical miles per hour, but may reach 23 knots for short period of time. They have asymmetrical pigmentation on their heads. On their right sides their lower lip, mouth cavity and baleen plates are white, whilst the left side is dark. Their backward-sloping dorsal fins are more pronounced than in other baleen whales and set far behind the centre of the body. Fin whales have baleen with fine bristles which are brownish grey to grey-white. Their baleen can be up to 70cm long.
Fin whales are cosmopolitan animals and can be found in all oceans of the world, from Polar Regions to the Equator. They may migrate to subtropical waters for mating and calving during the winter months and to the colder areas of the Arctic and Antarctic for feeding during the summer months; although recent evidence suggests that during winter fin whales may be dispersed in deep ocean waters. There are at least three main isolated populations: North Atlantic, North Pacific and southern hemisphere.
Ecology and Behaviour
Fin whales are found most often alone, but groups of 3-7 individuals are common, and association of larger numbers or concentrations may occur in some areas at times. Because their powerful sounds can carry vast distances, fin whales may stay in touch with each other over long distances. The fin whale's blow is tall and shaped like an inverted cone, and the dive sequence is 5-8 blows approximately 70 seconds apart before a long dive. They rarely raise their flukes as they begin their dive, which can be as deep as 1,800 feet (550 m). Since fin whales are large and fast animals, they do not have significant predators, apart killer whales that sometime attack these mysticetes. Evidence of killer whales attacks have been reported on the pectoral and caudal fins, and on the flanks of fin whales. The vocalizations of fin whales are rather simple and consist mainly of low frequency moans and grunts and high-frequency pulses, apparently with a social function. These low frequency sounds may travel in water for hundreds of kilometers.
Females are thought to reach sexual maturity between the ages of six and 10; reaching up to 95% of their maximum body size. Calves may be born every two to three years with gestation lasting for just over 11 months, with usually one calf measuring 6-7 m in length and 1-1.5 metric tons in weight. Mating period ranges between December-February in the Northern Hemisphere and May-July in the Southern Hemisphere. Weaning takes place after six to eight months. They may live for 80-90 years. The number of pregnant females in relation to that of adult females (gross pregnancy rates) typically ranges between 38-49%.
The fin whale mainly feeds during summer, when adults may consume up to 2 tons of krill per day, and fasts during the winter months, even if some exceptions may exist. Fin whales' diet may vary with season and locality; they have been described to feed on a wide variety of organisms, depending on its availability. Preferred prey in the Northern Hemisphere is likely krill, mainly composed of the euphausiid Meganyctiphanes norvegica, although other planktonic crustaceans, schooling fishes and small squids may be consumed. In the Southern Hemisphere, the diet is almost exclusively krill, mostly the euphausiids Euphausia vallentini and Euphausia superba.
Once one of the most abundant of the large whales, the fin whale was soon heavily exploited and its population became severely depleted. As many as 30,000 fin whales were slaughtered each year from 1935 to 1965; in total, 723,000 were killed in the southern hemisphere alone in the twentieth century. The most recent population estimates counts about 15,200 fin whales in the Southern Hemisphere. The abundance estimates from the Northern Hemisphere number about 65,000 individuals: 25,800 in the central North Atlantic, 4100 in the northeastern North Atlantic, 17,400 in the Spain-Portugal-British Isles area, 1,700 off West Greenland, 1,000 off Newfoundland, 2,800 off the east coast of North America south of the Gulf of St Lawrence, 5,700 in the Bering Sea, Aleutian Islands, and Gulf of Alaska, 3,300 off the west coast of the United States and 3,500 in the Mediterranean Sea.
The species was assessed as endangered in 2008. The analysis in this assessment estimates that the global population has declined by more than 70% over the last three generations (1929-2007), although in the absence of current substantial catches it is probably increasing. Most of the global decline over the last three generations is attributable to the major decline in the Southern Hemisphere. The North Atlantic subpopulation may have increased, while the trend in the North Pacific subpopulation is uncertain.
Before modern whaling in the late 1900s, fin whales were largely unthreatened by human pressure, since they were rather difficult to catch. Successively, they were severely depleted worldwide by commercial whaling in the 20th century. Fin whales have been protected in the Southern Hemisphere and North Pacific since 1975, and catches ceased in the North Atlantic by 1990, except for small "aboriginal subsistence" catches off Greenland. Commercial catches resumed off Iceland in 2006. A Japanese fleet resumed experimental catches of fin whales in the Antarctic in 2005. Acoustic pollution, presence of detrimental manmade compounds in the marine food web, increased human disturbance, interaction with fisheries, depletion of living resources and loss of biodiversity, are among the main problems that may affect fin whales worldwide. In addition, the fin whale is one of the most commonly recorded species of large whale reported in vessel collisions all over the world's oceans. Fin whales are also occasionally caught in fishing gear as a by-catch.
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