# Fin whale

The fin whale (Balaenoptera physalus), also known as the finback whale or common rorqual, is a species of baleen whale and the second-longest cetacean after the blue whale. The biggest individual reportedly measured 26 m (85 ft) in length, with a maximum recorded weight of 77 to 81 tonnes (85 to 89 short tons; 76 to 80 long tons). The fin whale's body is long, slender and brownish-gray in color, with a paler underside to appear less conspicuous from below (countershading).
At least two recognized subspecies exist, one in the North Atlantic and one across the Southern Hemisphere. It is found in all the major oceans, from polar to tropical waters, though it is absent only from waters close to the pack ice at the poles and relatively small areas of water away from the open ocean. The highest population density occurs in temperate and cool waters. Its prey mainly consists of smaller schooling fish, small squid, or crustaceans, including copepods and krill. Mating takes place in temperate, low-latitude seas during the winter. Fin whales are often observed in pods of 6–10 animals, with whom they communicate utilizing frequency-modulated sounds, ranging from 16 to 40 hertz.
Like all other large whales, the fin whale was a prized kill during the "heyday" of whaling, from 1840 to 1861. It remained so into the 20th century but decades of over harvesting contributed to declining numbers through the late 20th century. Over 725,000 fin whales were reportedly taken from the Southern Hemisphere between 1905 and 1976. Post-recovery numbers of the southern subspecies are predicted to be less than 50% of the pre-whaling population, even by 2100, due to long-lasting impacts of whaling and slow recovery rates. As of 2018, it was assessed as vulnerable by the IUCN.

## Taxonomy

Balaenopteridae
B. acutorostrata (minke whale)
B. musculus (blue whale)
B. borealis (sei whale)
Eschrichtius robustus (gray whale)
B. physalus (fin whale)
Megaptera novaeangliae (humpback whale) :
A phylogenetic tree of six baleen whale species :
The fin whale was first described by Friderich Martens in 1675 and by Paul Dudley in 1725. The former description was used as the primary basis for the species Balaena physalus by Carl Linnaeus in 1758. In 1804, Bernard Germain de Lacépède reclassified the species as Balaenoptera rorqual, based on a specimen that had stranded on Île Sainte-Marguerite (Cannes, France) in 1798. In 1830, Louis Companyo described a specimen that had been stranded near Saint-Cyprien, southern France, in 1828 as Balaena musculus. Most later authors followed him in using the specific name musculus, until Frederick W. True (1898) showed that it referred to the blue whale. In 1846, British taxonomist John Edward Gray described a 16.7 m (55 ft) specimen from the Falkland Islands as Balaenoptera australis. In 1865, German naturalist Hermann Burmeister described a roughly 15 m (49 ft) specimen found near Buenos Aires about 30 years earlier as Balaenoptera patachonicus. In 1903, Romanian scientist Emil Racoviță placed all these designations into Balaenoptera physalus. The word physalus comes from the Greek word physa, meaning "blows," referring to the prominent blow of the species.
Fin whales are rorquals, members of the family Balaenopteridae, which includes the humpback whale, the blue whale, Bryde's whale, the sei whale, and the minke whale. The family diverged from the other baleen whales in the suborder Mysticeti as long ago as the middle Miocene.
Recent DNA evidence indicates the fin whale may be more closely related to the humpback whale (Megaptera novaeangliae) and, in at least one study, the gray whale (Eschrichtius robustus), two whales in different genera, than it is to members of its own genus, such as the minke whales. As of 2023, four subspecies are named, each with distinct physical features and vocalizations. The northern fin whale, B. p. physalus (Linnaeus 1758) inhabits the North Atlantic and the southern fin whale, B. p. quoyi (Fischer 1829) occupies the Southern Hemisphere. Most experts consider the fin whales of the North Pacific to be a third subspecies—this was supported by a 2013 study, which found that the Northern Hemisphere B. p. physalus was not composed of a single subspecies. A 2019 genetic study concluded that the North Pacific fin whales should be considered a subspecies, suggesting the name B. p. velifera (Scammon 1869). The three groups mix at most rarely.
Clarke (2004) proposed a "pygmy" subspecies (B. p. patachonica, Burmeister, 1865) that is purportedly darker in colour and has black baleen. He based this on a single physically mature 19.8 m (65 ft) female caught in the Antarctic in 1947–48, the smaller average size (a few feet) of sexually and physically mature fin whales caught by the Japanese around 50°S, and smaller, darker sexually immature fin whales caught in the Antarctic which he believed were a "migratory phase" of his proposed subspecies. The subspecies has not been genetically established, and is not recognized by the Society for Marine Mammalogy.

### Hybrids

The genetic distance between blue and fin whales has been compared to that between a chimpanzee and human (3.5 million years on the evolutionary tree.) Nevertheless, hybrid individuals between blue and fin whales with characteristics of both are known to occur with relative frequency in both the North Atlantic and North Pacific.
The DNA profile of a sampling of whale meat in the Japanese market found evidence of blue/fin hybrids. Similarly, a whale caught by whalers off the coast of Iceland in 2018 was found to be a hybrid descended from a female blue whale and a male fin whale. A 2024 genome analysis of North Atlantic blue whales found that approximately 3.5% of their genome was derived from hybridization with fin whales. The gene flow was determined to be unidirectional from fin to blue whales. Despite their smaller size, fin whales have similar cruising and sprinting speeds to blue whales, which would allow fin males to complete courtship chases with blue females.

## Anatomy

The body is relatively thin with a slender rostrum and large hook-like dorsal fin that is situated in the posterior fourth of the body. It has an elongated ridge on its back, and around 350 to 400 baleen plates. Like all rorquals, the fin whale has grooves between the tip of the lower jaw and the navel.
Among whale species, the fin whale is exceeded in size only by the blue whale. Adults usually average 40 to 50 tonnes in weight. Males have a mean length of 21 m (69 ft), and females of 22 m (72 ft). They are sexually dimorphic, with females generally being longer and heavier than males. The largest specimens can attain lengths of over 26 m (85 ft) and weights of 77 to 81 tonnes.
The fin whale is brownish to dark or light gray dorsally and white ventrally. The left side of the head is dark gray, while the right side exhibits a complex pattern of contrasting light and dark markings. The right lower jaw is white or light gray, which sometimes extends laterally and dorsally unto the upper jaw. Dark, oval-shaped areas of pigment called "flipper shadows" extend below and posterior to the pectoral fins.
The penis size of fin whales typically reaches a length of 1.3 m (4 ft 3 in); the testes usually weigh 1–3 kg (2.2–6.6 lb) in mature individuals. The oral cavity of the fin whale has a very stretchy or extensible nerve system which aids them in feeding.

## Life history

Mating takes place during the winter months, in temperate, low-latitude waters, and the gestation period lasts between 11 and 12 months. At 6 or 7 months of age, when it is 11 to 12 m (36 to 39 ft) in length, a newborn weans from its mother, and the calf accompanies its mother to the summer feeding area. Although reports of up to six foetuses have been made, single births are far more typical. Females reproduce every two to three years. In the Northern Hemisphere, females reach sexual maturity between the ages of 6 and 12 at lengths of 17.7–19 m (58–62 ft), and around 20 m (66 ft) in the Southern Hemisphere. Calves remain with their mothers for about a year.
Full physical maturity is attained between 25 and 30 years. Fin whales have a maximum life span of at least 94 years of age, although specimens have been found aged at an estimated 135–140 years. The fin whale is one of the fastest cetaceans and can sustain speeds between 37 km/h (23 mph) and 41 km/h (25 mph) and bursts up to 46 km/h (29 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.

### Vocalizations

Like other whales, males make long, loud, low-frequency sounds. The vocalizations of blue and fin whales are the lowest-frequency sounds made by any animal. Most sounds are frequency-modulated (FM) down-swept infrasonic pulses from 16 to 40 hertz frequency (the range of sounds that most humans can hear falls between 20 hertz and 20 kilohertz). Each sound lasts one to two seconds, and various sound combinations occur in patterned sequences lasting 7 to 15 minutes each. The whale then repeats the sequences in bouts lasting up to many days. The vocal sequences have source levels of up to 184–186 decibels relative to 1 micropascal at a reference distance of one metre and can be detected hundreds of miles from their source.
When fin whale sounds were first recorded by US biologists, they did not realize that these unusually loud, long, pure and regular sounds were being made by whales. They first investigated the possibilities that the sounds were due to equipment malfunction, geophysical phenomena, or even part of a Soviet Union scheme for detecting enemy submarines. Eventually, biologists demonstrated that the sounds were the vocalizations of fin whales.
Direct association of these vocalizations with the reproductive season for the species and that only males make the sounds point to these vocalizations as possible reproductive displays. Over the past 100 years, the dramatic increase in ocean noise from shipping and naval activity may have slowed the recovery of the fin whale population, by impeding communications between males and receptive females. Fin whale songs can penetrate over 2,500 m (8,200 ft) below the sea floor and seismologists can use those song waves to assist in underwater surveys.

### Breathing

When feeding, fin whales blow five to seven times in quick succession, but while traveling or resting will blow once every minute or two. On their terminal (last) dive they arch their back high out of the water, but rarely raise their flukes out of the water. They then dive to depths of up to 470 m (1,540 ft) when feeding or a few hundred feet when resting or traveling. The average feeding dive off California and Baja lasts 6 minutes, with a maximum of 17 minutes; when traveling or resting they usually dive for only a few minutes at a time.

## Ecology
### Range and habitat

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, although they can reach into the Baltic Sea, a marginal sea of such conditions. The highest population density occurs in temperate and cool waters. It is less densely populated in the warmest, equatorial regions.
The North Atlantic fin whale has an extensive distribution, occurring from the Gulf of Mexico and Mediterranean Sea, northward to Baffin Bay and Spitsbergen. In general, fin whales are more common north of approximately 30°N latitude, but considerable confusion arises about their occurrence south of 30°N latitude because of the difficulty in distinguishing fin whales from Bryde's whales. Extensive ship surveys have led researchers to conclude that the summer feeding range of fin whales in the western North Atlantic is mainly between 41°20'N and 51°00'N, from shore seaward to the 1,000 fathoms (6,000 ft; 1,800 m) contour.
Summer distribution of fin whales in the North Pacific is the immediate offshore waters from central Baja California to Japan and as far north as the Chukchi Sea bordering the Arctic Ocean. They occur in high densities in the northern Gulf of Alaska and southeastern Bering Sea between May and October, with some movement through the Aleutian passes into and out of the Bering Sea. Several whales tagged between November and January off southern California were killed in the summer off central California, Oregon, British Columbia, and in the Gulf of Alaska. Fin whales have been observed feeding 250 miles south of Hawaii in mid-May, and several winter sightings have been made there. Some researchers have suggested that the whales migrate into Hawaiian waters primarily in the autumn and winter.
Although fin whales are certainly migratory, moving seasonally in and out of high-latitude feeding areas, the overall migration pattern is not well understood. Acoustic readings from passive-listening hydrophone arrays indicate a southward migration of the North Atlantic fin whale occurs in the autumn from the Labrador-Newfoundland region, south past Bermuda, and into the West Indies. One or more populations of fin whales are thought to remain year-round in high latitudes, moving offshore, but not southward in late autumn. A study based on resightings of identified fin whales in Massachusetts Bay indicates that calves often learn migratory routes from their mothers and return to their mother's feeding area in subsequent years.
In the Pacific, migration patterns are poorly characterized. Although some fin whales are apparently present year-round in the Gulf of California, there is a significant increase in their numbers in the winter and spring. Southern fin whales migrate seasonally from relatively high-latitude Antarctic feeding grounds in the summer to low-latitude breeding and calving areas in the winter. The location of winter breeding areas is still unknown, since these whales tend to migrate in the open ocean.
It has been shown that populations of fin whales within the Mediterranean have preferred feeding locations that partially overlap with high concentrations of plastic pollution and microplastic debris. High concentrations of microplastics most likely overlap with fin whales' preferred feeding grounds because both microplastic and the whale's food sources are near high trophic upwelling areas.
The total historical North Pacific population was estimated at 42,000 to 45,000 before the start of whaling. Of this, the population in the eastern portion of the North Pacific was estimated to be 25,000 to 27,000. Surveys conducted in 1991, 1993, 1996, and 2001 produced estimates between 1,600 and 3,200 off California and 280 and 380 off Oregon and Washington. Surveys in coastal waters of British Columbia in summers 2004 and 2005 produced abundance estimates of approximately 500 animals. Fin whales might have started returning to the coastal waters off British Columbia (a sighting occurred in Johnstone Strait in 2011) and Kodiak Island. Size of the local population migrating to Hawaiian Archipelago is unknown.
Finbacks are also relatively abundant along the coast of Peru and Chile (in Chile, most notably off Los Lagos region such as Gulf of Corcovado in Chiloé National Park, Punta de Choros, port of Mejillones, and Caleta Zorra. Year-round confirmations indicate possible residents off pelagic north eastern to central Chile such as around coastal Caleta Chañaral and Pingüino de Humboldt National Reserve, east of Juan Fernández Islands, and northeast of Easter Island and possible wintering ground exist for eastern south Pacific population.
Among Northern Indian Ocean and Bay of Bengal, such as along Sri Lanka, India, and Malaysia, sightings and older records of fin whales exist.

### Predation

The only known predator of the fin whale is the killer whale, with at least 20 eyewitness and second-hand accounts of attack or harassment. They usually flee and offer little resistance to attack. Only a few confirmed fatalities have occurred. In October 2005, 16 killer whales attacked and killed a fin whale in the Canal de Ballenas, Gulf of California, after chasing it for about an hour. They fed on its sinking carcass for about 15 minutes before leaving the area. In June 2012, a pod of killer whales was seen in La Paz Bay, in the Gulf of California, chasing a fin whale for over an hour before finally killing it and feeding on its carcass. The whale bore numerous tooth rakes over its back and dorsal fin; several killer whales flanked it on either side, with one individual visible under water biting at its right lower jaw. In July 1908, a whaler reportedly saw two killer whales attack and kill a fin whale off western Greenland. In January 1984, seven were seen from the air circling, holding the flippers, and ramming a fin whale in the Gulf of California, but the observation ended at nightfall.

### Feeding

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 krill in the genera Euphausia, Thysanoessa, and Nyctiphanes, large copepods in the genus Neocalanus, small schooling fish (e.g. the genera Engraulis, Mallotus, Clupea, and Theragra), and squid. Based on stomach content analysis of over 19,500 fin whales caught by the Japanese whaling fleet in the North Pacific from 1952 to 1971, 64.1% contained only krill, 25.5% copepods, 5.0% fish, 3.4% krill and copepods and 1.7% squid. Nemoto (1959) analyzed the stomach contents of about 7500 fin whales caught in the northern North Pacific and Bering Sea from 1952 to 1958, found that they mainly preyed on euphausiids around the Aleutian Islands and in the Gulf of Alaska and schooling fish in the northern Bering Sea and off Kamchatka.
Of the fin whale stomachs sampled off British Columbia between 1963 and 1967, euphausiids dominated the diet for four of the five years (82.3 to 100% of the diet), while copepods only formed a major portion of the diet in 1965 (35.7%). Miscellaneous fish, squid, and octopus played only a very minor part of the diet in two of the five years (3.6 to 4.8%). Fin whales caught off California between 1959 and 1970 fed on the pelagic euphausiid Euphausia pacifica (86% of sampled individuals), the more neritic euphausiid Thysanoessa spinifera (9%), and the northern anchovy (Engraulis mordax) (7%); only trace amounts (<0.5% each) were found of Pacific saury (C. saira) and juvenile rockfish (Sebastes jordani).
In the North Atlantic, they prey on euphausiids in the genera Meganyctiphanes, Thysanoessa and Nyctiphanes and small schooling fish (e.g. the genera Clupea, Mallotus, and Ammodytes). Of the 1,609 fin whale stomachs examined at the Hvalfjörður whaling station in southwestern Iceland from 1967 to 1989 (caught between June and September), 96% contained only krill, 2.5% krill and fish, 0.8% some fish remains, 0.7% capelin (M. villosus), and 0.1% sandeel (family Ammodytidae); a small proportion of (mainly juvenile) blue whiting (Micromesistius poutassou) were also found. Of the krill sampled between 1979 and 1989, the vast majority (over 99%) was northern krill (Meganyctiphanes norvegica); only one stomach contained Thysanoessa longicaudata. Off West Greenland, 75% of the fin whales caught between July and October had consumed krill (family Euphausiidae), 17% capelin (Mallotus) and 8% sand lance (Ammodytes sp.). Off eastern Newfoundland, they chiefly feed on capelin, but also take small quantities of euphausiids (mostly T. raschii and T. inermis). In the Ligurian-Corsican-Provençal Basin in the Mediterranean Sea they make dives as deep as 470 m (1,540 ft) to feed on the euphausiid Meganyctiphanes norvegica, while off the island of Lampedusa, between Tunisia and Sicily, they have been observed in mid-winter feeding on surface swarms of the small euphausiid Nyctiphanes couchi.
In the Southern Hemisphere, they feed almost exclusively on euphausiids (mainly the genera Euphausia and Thysanoessa), as well as taking small amounts of amphipods (e.g. Themisto gaudichaudii) and various species of fish. Of the more than 16,000 fin whales caught by the Japanese whaling fleet in the Southern Hemisphere between 1961 and 1965 that contained food in their stomachs, 99.4% fed on euphausiids, 0.5% on fish, and 0.1% on amphipods. In the Southern Ocean they mainly consume E. superba.
The animal feeds by opening its jaws while swimming at some 11 km/h (6.8 mph) in one study, which causes it to engulf up to 70 m$^3$ (18,000 US gal; 15,000 imp gal) of water in one gulp. It then closes its jaws and pushes the water back out of its mouth through its baleen, which allows the water to leave while trapping the prey. An adult has between 262 and 473 baleen plates on each side of the mouth. Each plate is made of keratin that frays out into fine hairs on the ends inside the mouth near the tongue. Each plate can measure up to 76 cm (30 in) in length and 30 cm (12 in) in width.
The whale routinely dives to depths of more than 200 m (660 ft) where it executes an average of four "lunges", to accumulate krill. Each gulp provides the whale with approximately 10 kg (22 lb) of food. One whale can consume up to 1,800 kg (4,000 lb) of food a day, leading scientists to conclude that the whale spends about three hours a day feeding to meet its energy requirements, roughly the same as humans. If prey patches are not sufficiently dense, or are located too deep in the water, the whale has to spend a larger portion of its day searching for food. One hunting technique is to circle schools of fish at high speed, frightening the fish into a tight ball, then turning on its side before engulfing the massed prey.

### Parasites, epibiotics, and pathology

Fin whales suffer from a number of pathological conditions. The parasitic copepod Pennella balaenopterae—usually found on the flank of fin whales—burrows into their blubber to feed on their blood, while the pseudo-stalked barnacle Xenobalanus globicipitis is generally found more often on the dorsal fin, pectoral fins, and flukes.
Other barnacles found on fin whales include the acorn barnacle Coronula reginae and the stalked barnacle Conchoderma auritum, which attaches to Coronula or the baleen. The harpacticid copepod Balaenophilus unisetus (heavy infestations of which have been found in fin whales caught off northwestern Spain) and the ciliate Haematophagus also infest the baleen, the former feeding on the baleen itself and the latter on red blood cells.
The remora Remora australis and occasionally the amphipod Cyamus balaenopterae can also be found on fin whales, both feeding on the skin. Infestations of the giant nematode Crassicauda boopis can cause inflammation of the renal arteries and potential kidney failure, while the smaller C. crassicauda infects the lower urinary tract. Out of 87 whales taken and necropsied from the North Atlantic, infection from Crassicauda boopis was found to be very prevalent and invasive, indicating high probability that it was responsible for causing death in these whales. C. boopis was found in 94% of the whales examined. The worms were usually enveloped by "exuberant tissue reactions which in some whales obstructed multiple renal veins". The parasite was most likely by environmental contamination, involving shedding of larvae in urine. Major inflammatory lesions in the mesenteric arteries suggested that the worm larvae were ingested and migrated to the kidney.
These observations suggest that infection from C. boopis can be "lethal by inducing congestive renal failure". Injury to the vascular system is also a result of moderate infections. Therefore, the implication can be made that the feeding migration of fin whales every year in circumpolar waters can be associated with pathologic risk.
An emaciated 13 m (43 ft) female fin whale, which stranded along the Belgian coast in 1997, was found to be infected with lesions of Morbillivirus. In January 2011, a 16.7 m (55 ft) emaciated adult male fin whale stranded dead on the Tyrrhenian coastline of Italy was found to be infected with Morbillivirus and the protozoa Toxoplasma gondii, as well as carrying heavy loads of organochlorine pollutants.

## Human interaction
### Whaling

In the 19th century, the fin whale was occasionally hunted by open-boat whalers, but it was relatively safe, because it could easily outrun ships of the time and often sank when killed, making the pursuit a waste of time for whalers. However, the later introduction of steam-powered boats and harpoons that exploded on impact made it possible to kill and secure them along with blue and sei whales on an industrial scale. As other whale species became overhunted, the whaling industry turned to the still-abundant fin whale as a substitute. It was primarily hunted for its blubber, oil, and baleen. Around 704,000 fin whales were caught in Antarctic whaling operations alone between 1904 and 1975.
The introduction of factory ships with stern slipways in 1925 substantially increased the number of whales taken per year. By 1962–63, sei whale catches began to increase as fin whales became scarce. From the late 19th century until the 1960s, fin whales were a major target of whaling in the Sea of Japan. Japan took 300 to 400 fin whales per year in the Sea of Japan and East China Sea in the 1910s and 100 to 200 per year in the 1920s. After World War II, Korean whaling companies began hunting fin whales in these waters, and China and North Korea may have joined the hunt, but by the 1960s, the number of whales caught declined sharply due to population decline, and minke whales became the primary target in these waters.
The IWC prohibited hunting in the Southern Hemisphere in 1976. The Soviet Union engaged in the illegal killing of protected whale species in the North Pacific and Southern Hemisphere, over-reporting fin whale catches to cover up illegal takes of other species. The fin whale was given full protection from commercial whaling by the IWC in the North Pacific in 1976, and in the North Atlantic in 1987, with small exceptions for aboriginal catches and catches for research purposes. All populations worldwide remain listed as endangered species by the US National Marine Fisheries Service and the International Conservation Union Red List.
The IWC has set a quota of 19 fin whales per year for Greenland. Meat and other products from whales killed in these hunts are widely marketed within Greenland, but export is illegal. Iceland and Norway are not bound by the IWC's moratorium on commercial whaling because both countries filed objections to it.
In the Southern Hemisphere, Japan permitted annual takes of 10 fin whales under its Antarctic Special Permit whaling program for the 2005–2006 and 2006–2007 seasons. The proposal for 2007–2008 and the subsequent 12 seasons allowed takes of 50 per year. In 2019, Japan left the International Whaling Commission (IWC) and resumed commercial whaling. Japan reported a catch of 212 total whales in both 2020 and 2021; however, no fin whale catches have yet been reported.

### Ship interaction

Collisions with ships are a major cause of mortality. In some areas, they cause a substantial portion of large whale strandings. Most serious injuries are caused by large, fast-moving ships over or near continental shelves.
A 60-foot-long fin whale was found stuck on the bow of a container ship in New York harbour on 12 April 2014. Two dead fin whales, one 65 feet and one 25 feet, were discovered stuck to the Australian destroyer HMAS Sydney in May 2021 when the ship arrived in Naval Base San Diego.
Ship collisions frequently occur in Tsushima Strait and result in damage done to whales, passengers, and vessels. In response the Japanese Coast Guard has started a surveillance program to monitor large cetacean activity in Tsushima Strait to inform operating vessels in the area.

### Whale watching

Fin whales are regularly encountered on whale-watching excursions worldwide. In Monterey Bay and the Southern California Bight, fin whales are encountered year-round, with the best sightings between November and March. They can even be seen from land (for example, from Point Vicente, Palos Verdes, where they can be seen lunge feeding at the surface only a half mile to a few miles offshore). They are regularly sighted in the summer and fall in the Gulf of St. Lawrence, the Gulf of Maine, the Bay of Fundy, the Bay of Biscay, Strait of Gibraltar, and the Mediterranean. In southern Ireland, they are seen inshore from June to February, with peak sightings in November and December.

### Conservation

As of 2018, the global fin whale population is estimated to be 100,000 mature individuals. There are an estimated total of 70,000 individuals in the North Atlantic, 50,000 in the North Pacific, and 25,000 in the Southern Hemisphere.
The fin whale is listed as a vulnerable species on the IUCN Red List. They are also included in the Endangered Species Act of 1973. The fin whale is listed on both Appendix I and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). Commercial whaling of the species was officially banned in 1976, both in the North Pacific and Southern Hemisphere. Post-whaling populations have steadily increased. The fin whale is still hunted off the waters of West Greenland, and in the Antarctic Ocean by Japanese researchers.
They may also become entangled in fishing gear in some rare instances. Military sonar may effect the behavioral patterns of fin whales, which can lead to population decline. Similarly, whale watching may cause fin whales to alter their behavior and foraging habits.
The fin whale is covered by the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).