Fin whale - Balaenoptera physalus

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The fin whale is a large baleen whale, measuring 24 m in the northern hemisphere and 27 m in the southern hemisphere. Females grow approximately 1.5 m longer than males. The rostrum is narrow and "V" shaped. The dorsal fin, located two-thirds of the way down the back, can be up to 40 cm tall, and a distinct ridge runs from the dorsal fin to the flukes. The dorsal fin rises at a shallow angle from the animal's back. The fin whale’s coloration is noteworthy: while it is dark (brown or gray) dorsally and white ventrally, its mouth is asymmetrically colored. The right side of the mouth, including the baleen, is white, while the left side is dark. This adaptation is unique among the baleen whales.

Fin whales have 260-480 baleen plates per side. The 50-100 throat pleats are long, and reach to the navel. The blow is distinct and tall, measuring four to six meters high. Calves are 6.5 m long. Large animals may attain weights of up to 130 tons, but most probably weigh much less. Body weight varies seasonally.

The other three medium to large balaenopterids (blue, sei, and Bryde’s whales) are likely to be confused with fin whales. Careful attention to color pattern, head shape, and dorsal fin shape and position will help to distinguish them. The head of fin whales is much more pointed than that of blue whales, and the dorsal fin is set further back and rises at a shallower angle than those of sei or Bryde’s whales. The best clue to identification, however, is the asymmetrical coloration of the head.

Fin whales migrate poleward in summer to exploit rich, cold waters, and are found in warmer waters in winter, where they reproduce. They can be found from 20° – 75°N and 20° – 75°S. Fin whales are the fastest of the great whales, having been recorded traveling almost 300 km in one day. Adult females reportedly arrive at summer feeding grounds first and leave last.

In the eastern North Pacific, fin whales have been observed in the Chukchi Sea, Gulf of Alaska, Prince William Sound, off the coast of the Aluetian Islands in the north, and off the coast of Baja California in the south. One population appears to be resident to the Gulf of California. In the western North Atlantic, fin whales have been seen in the Philippine Sea, East China Sea, Yellow Sea, Sea of Japan, Chukchi Sea, and Sea of Okhotsk.

In the western North Atlantic, fin whales are common in summer from Cape Hatteras north; distributed from the coasts of Canada, Newfoundland, and Cape Cod in the north to the Gulf of Mexico and the shores of Florida and the Greater Antilles in the south. In summer fin whales are concentrated between shore and the 1800 m curve from 41^oN to 57^oN. In the east, distribution extends from the coasts of Norway, Iceland, Jan Mayen, and the Spitsbergen Archipelago in the north to the Straits of Gibraltar and the Mediterranean Sea.

Fin whales are also found in the Southern Ocean, from the Antarctic and Indian Ocean to the coasts of New Zealand, Peru, Brazil, and South Africa.

Fin whales inhabit coastal waters.

Fin whales tend to be more social than other rorquals, gathering in pods of 2-7 whales or more. Sexual maturity occurs at ages of 6-10 years in males and 7-12 years in females, depending on the population and time period. Reproductive activity occurs in winter, when whales are in warmer southern waters. Females mate every two or three years, and after an eleven month gestation, nurse their calves for six to eight months. Fin whales can live to be up to 90 years of age.

Fin whales feed by lunging at prey, feeding on the surface and at depth. The fin whale will eat both fish and krill; capelin, sandlance, and herring are of particular importance. Fin whales in the Southern Oceans feed almost exclusively on krill. Fin whales have a broad diet dominated by: Invertebrates > fish > squid

Prey species include:

Invertebrates: Euphausia superba, Thysanoessa macrura, Euphausia vallentini, Euphaushia crystallorophias, Thysanoessa raschii, Thysanoessa inermis, Thysanoessa longipes, Calanus cristatus, Calanus plumchrus, Euphausia pacifica, Thysanoessa spinifera, Calanus finmarchius, Meganyctiphanes norvegica

Cephalopods: Nototodarus sloani

Fish: Sardinella melanosticta, Theragra chalcogramma, Mallotus villosus, Ammodytes americanus, Ammodytes dubius, Engraulis mordax, Clupea harengus

Main threats to fin whales include:

• Entanglement in debris/fishing gear

• Noise pollution

• Ship strikes

The fin whale is classified as ‘Endangered’ by the IUCN. In the United States, the fin whale is on the endangered species list and is additionally protected by the Marine Mammal Protection Act. Global population might have been as high as 500,000 before commercial whaling of the species. The fin whale population today is estimated to be 14,620 to 18,630 in the North Pacific; 3,590 to 6,300 in the western North Atlantic; 10,500 in the eastern North Atlantic; and 85,200 in the Southern Oceans. The introduction of the explosive harpoon and steam-powered catcher boat in 1864 meant doom for great whales, which had previously been largely unobtainable for whalers. After whalers devastated the blue whale population, the fin whale was targeted next, hunted relentlessly in all major oceans between the 1930s and 1960s. Their numbers were severely depleted, especially in the Southern Oceans. Presently, the fin whale is hunted only off the coast of Greenland, at a subsistence level. In the 1980s the capelin stock collapsed off the coast of Canada, which may have affected fin whale numbers as well.

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• World Register of Marine Species (WoRMS)
• Encyclopedia of Life
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Barlow, J. 1994. Recent information on the status of large whales in California waters. NOAA Technical Memorandum NMFS SWFSC 203:1-27.

Boyd, I.L., C. Lockyer and H.D. Marsh. 1999. Reproduction in marine mammals. pp. 218- 287 in J.E. Reynolds III and S.A. Rommel, eds. Biology of Marine Mammals. Smithsonian Institution Press, Washington, DC.

Gambell, R. 1985. Fin whale Balaenoptera physalus (Linneaus, 1758). pp. 171-192 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 3: The sirenians and baleen whales. Academic Press.

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Perry, S.L., D.P. DeMaster and G.K. Silber. 1999. The fin whale. Marine Fisheries Review 61(1):1-8.