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iSei Whale
Image:Balaenoptera borealis 2.jpg A Sei Whale surfacing side-on Image:Sei whale size.png Size comparison against an average human
Conservation status
Image:Status iucn2.3 EN.svg Endangered (EN)<ref name="iucn">Cetacean Specialist Group (1996). Balaenoptera borealis. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 2006-11-03. Database entry includes justification for why this species is endangered.</ref> </div>
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Subclass: Eutheria Order: Cetacea Suborder: Mysticeti Family: Balaenoptiidae Genus: Balaenoptera Species: B. borealis
Binomial name
Balaenoptera borealis Lesson, 1828
Sei Whale range

The Sei Whale (pronounced: [seɪ] or [saɪ]), Balaenoptera borealis, is a baleen whale, the third largest rorqual after the Blue Whale and the Fin Whale.<ref name="mfr">S.L. Perry, D.P. DeMaster, and G.K. Silber (1999). "Special Issue: The Great Whales: History and Status of Six Species Listed as Endangered Under the U.S. Endangered Species Act of 1973". Marine Fisheries Review 61 (1): 52-58.</ref> Its name comes from the Norwegian word for pollock, a fish that appears off the coast of Norway at the same time as the Sei Whale.<ref name="acs">Sei Whale & Bryde's Whale Balaenoptera borealis & Balaenoptera edeni. American Cetacean Society (March 2004). Retrieved on 2006-11-08.</ref> The whale reaches lengths of 20 metres (66 ft) long and weights of up to 30,000 kilograms (66,000 lb).<ref name="nmfs">Reeves, R., G. Silber and M. Payne (July 1998). Draft Recovery Plan for the Fin Whale Balaenoptera physalus and Sei Whale Balaenoptera borealis (PDF), Silver Spring, Maryland: National Marine Fisheries Service.</ref> It consumes an average of about 900 kilograms (2,000 lb) of food each day, primarily marine copepods and krill.<ref name="adw">Shefferly, N. (1999). Balaenoptera borealis. Animal Diversity Web. Retrieved on 2006-11-04.</ref> It is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mi/hr, 27 knots) over short distances.<ref name="adw"/>

The Sei Whale can be found worldwide in all oceans and adjoining seas, preferring deep off-shore waters<ref name="Gambell85a">Gambell, R. (1985). “Sei Whale 'Balaenoptera borealis Lesson, 1828”, Handbook of Marine Mammals, Vol. 3. London: Academic Press.</ref> and tending to avoid polar and tropical waters and semi-enclosed bodies of water. In general, the Sei Whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter, although in most areas the exact migration routes are not well known.<ref name="nmfs"/>

Following large-scale commercial hunting of the species between the late-nineteenth and late-twentieth centuries when over 238,000 individuals were taken,<ref name="horwood87">Horwood, J. (1987). The sei whale: population biology, ecology, and management. Kent, England: Croom Helm Ltd.. ISBN 0-7099-4786-0.</ref> the Sei Whale is now an internationally protected species,<ref name="iucn"/> although it continues to be hunted to a limited extent under controversial scientific research programmes conducted by Iceland and Japan.<ref name="wwf05">WWF-International (2005-06-01). Japanese Scientific Whaling: Irresponsible Science, Irresponsible Whaling. Press release. Retrieved on 2006-11-10.</ref> As of 2006, the worldwide population of the Sei Whale was about 54,000, approximately one-fifth of its pre-whaling population.<ref name="acs"/>

Contents 1 Taxonomy and naming 2 Physical description and behaviour 2.1 Feeding 2.2 Life history 2.3 Vocalizations 3 Habitat and migration 4 Whaling 4.1 North Atlantic 4.2 North Pacific 4.3 Southern Hemisphere 4.4 International protection 4.5 Post-protection whaling 5 Population estimates 6 See also 7 References 7.1 General References 8 External links

[edit] Taxonomy and naming

The species was first described by René-Primevère Lesson in 1828, but a further description was given by Karl Asmund Rudolphi and the species is occasionally referred to as Rudolphi's Rorqual, Pollack Whale, Coalfish Whale, Sardine Whale, or Japan Finner.<ref name="whalesonnet">Sei Whales (Balaenoptera borealis). Whales on the net. Retrieved on 2006-11-29.</ref>

Sei Whales are rorquals (family Balaenopteridae), a family that includes the Humpback Whale, the Blue Whale, Bryde's Whale, the Fin Whale and the Minke Whale. The family Balaenopteridae is believed to have diverged from the other families of the suborder Mysticeti as long ago as the middle Miocene.<ref name="evolution">Gingerich, P. (2004). “Whale Evolution”, McGraw-Hill Yearbook of Science & Technology (PDF), The McGraw Hill Companies.</ref> However, it is not known when the members of these families diverged from each other.

The word Sei comes from the Norwegian word seje for pollock, also referred to as coalfish, a close relative of codfish. Sei Whales appeared off the coast of Norway at the same time as the pollock, both coming to feed on the abundant plankton.<ref name="acs"/> The specific name is the Latin word borealis, meaning northern. In the Pacific, the whale has been called the Japan Finner; "finner" was a common term used to refer to rorquals. In Japanese the whale was called Iwashi kujira, or Sardine Whale, named for a fish that the whale has been observed to eat in the Pacific.<ref name="natlgeo1911">Andrews, R.C. (May 1911). "Shore Whaling: A World Industry". National Geographic Magazine.</ref>

Two geographically separated subspecies have been identified—the Northern Sei Whale (Balaenoptera borealis borealis) and Southern Sei Whale (Balaenoptera borealis schleglii).<ref name="ITIS">Balaenoptera borealis (TSN 180526). Integrated Taxonomic Information System. Accessed on 10 November 2006.</ref>

[edit] Physical description and behaviour

The Sei Whale is the third largest member of the Balaenopteridae family, after the Blue Whale and the Fin Whale.<ref name="mfr"/> Mature adults typically measure between 12.2 and 15.2 metres (40–50 ft)<ref name="adw"/> and weigh 20,000 to 30,000 kilograms (44,000–66,000 lb). The Southern Sei Whale is larger than the Northern Sei Whale, and females are considerably larger than males.<ref name="nmfs"/> The largest known Sei Whale measured 20 metres (66 ft),<ref name="adw"/> and weighed between 40,000 and 45,000 kilograms (88,000–100,000 lb). The largest specimens taken off Iceland were slightly longer than 16 metres (52 ft).<ref name="martin83">Martin, A.R. (1983). "The sei whale off western Iceland. I. Size, distribution and abundance". Rep. Int. Whal. Commn 33: 457-463.</ref> At birth, a calf typically measures 4–5 metres (13–16 ft) in length.<ref name="adw"/>

The whale's body is typically a dark steel grey with irregular light grey to white markings on the ventral surface. The whale has a series of 32-60 pleats or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The snout is pointed and the pectoral fins are relatively short compared to other whales, with a length of only 9% to 10% of the total body length, and pointed at the tips.<ref name="acs"/> It has single ridge extending from the tip of the snout to the paired blowholes that are a distinctive characteristic of baleen whales. The whale's skin is often marked by pits or wounds, which after healing become white scars. These are believed to be caused by ectoparisitic copepods (Penella spp.),<ref name="ivashin">Ivashin, M.V., Yu.P. Golubovsky (1978). "On the cause of appearance of white scars on the body of whales". Rep. Int. Whal. Commn 28: 199.</ref> lampreys,<ref name="rice77">Rice, D.W. (1977). "Synopsis of biological data on the sei whale and Bryde's whale in the eastern North Pacific". Rep. Int. Whal. Commn Spec. Iss. 1: 92-97.</ref> or possibly "cookie-cutter" sharks (Isistius brasiliensis).<ref name="shevchenko">Shevchenko, V.I. (1977). "Application of white scars to the study of the location and migrations of sei whale populations in Area III of the Antarctic". Rep. Int. Whal. Commn Spec. Iss. 1: 130-134.</ref> It has a tall, sickle-shaped dorsal fin that ranges in height from 25 to 61 centimetres (10 to 24 in), and is set about two-thirds of the way back from the tip of the snout. Dorsal fin shape, pigmentation pattern, and scarring have been used to a limited extent in photo-identification studies of Sei Whales.<ref name="schilling">Schilling, M.R., I. Seipt, M.T. Weinrich, S.E. Frohock, A.E. Kuhlberg, and P.J. Clapham (1992). "Behavior of individually identified sei whales Balaenoptera borealis during an episodic influx into the southern Gulf of Maine in 1986". Fish. Bull. 90: 749-755.</ref> The tail is thick and the fluke is relatively small in relation to body size.<ref name="acs"/>

This rorqual is a filter feeder, using its baleen to obtain its food from the water by opening its mouth, engulfing large amounts of water, then straining it out through its baleen plates, trapping any food items inside the mouth. An adult has between 300 and 380 ashy-black baleen plates on each side of the mouth, about 48 centimetres (19 in) long. Each plate is made of fingernail-like keratin that frays out into whitish fine hairs on the ends inside the mouth near the tongue.<ref name="adw"/> The very fine bristles of the Sei Whale's baleen (about 0.1 mm, .004 in) are cited as the most reliable feature distinguishing it from all other baleen whales.<ref name="mead">Mead, J.G. (1977). "Records of sei and Bryde's whales from the Atlantic coast of the United States, the Gulf of Mexico, and the Caribbean.". Rep. Int. Whal. Commn Spec. Iss. 1: 113-116.</ref>

The Sei Whale looks similar to other large baleen whales. The best way to distinguish between it and the Bryde's Whale, apart from differences in each whale's baleen, is by the presense of lateral ridges on the dorsal surface of the Bryde's Whale's head. Large Sei Whales can be confused with Fin Whales unless the Fin Whale's asymmetrical head colouration is clearly seen; the right side of the lower jaw of the Fin Whale is white, and the left side is grey. Viewed from the side, the Sei Whale's head has a slight arch that differs from the comparatively flat profile of the Fin Whale.<ref name="nmfs"/>

Sei Whales usually move alone<ref name="edds84">Edds, P.L., T.J. MacIntyre, and R. Naveen (1984). "Notes on a sei whale (Balaenoptera borealis Lesson) sighted off Maryland". Cetus 5: 4-5.</ref> or in small groups of up to six individuals.<ref name="schilling"/> Larger groups have been seen at particularly abudant feeding grounds. They appear to not have any well-defined social structure.<ref name="mfr"/>

The Sei Whale is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mi/hr, 27 knots) over short distances.<ref name="adw"/> Although it it notable for its speed, the whale is not a remarkable diver, diving to relatively shallow depths for between five to fifteen minutes. The whale swims near the surface for a few minutes, with blows occurring at intervals of about 40 to 60 seconds followed by a "deep dive". Between shallow dives the whale stays close to the surface and remains visible in clear, calm waters. Unlike the Fin Whale, the Sei Whale tends not to roll high out of the water as it dives. The blowholes and dorsal fin are often exposed above the water surface simultaneously. The whale almost never extends its flukes above the surface, and it rarely breaches.<ref name="nmfs"/>

[edit] Feeding

The whale feeds near the surface of the ocean, swimming on its side through swarms of prey. An average Sei Whale eats about 900 kilograms (2,000 lb) of food each day.<ref name="adw"/> In the North Atlantic, the Sei Whale feeds primarily on calanoid copepods, with a secondary preference for euphausiids.<ref name="christensen92">Christensen, I., T. Haug, and N. Øien (1992). "A review of feeding and reproduction in large baleen whales (Mysticeti) and sperm whales Physeter macrocephalus in Norwegian andadjacent waters". Fauna norvegica Series A 13: 39-48.</ref> Its preference for zooplankton has been determined from stomach analyses, direct observations of feeding behaviour, and examination of feces collected near Sei Whales.<ref name="watkins">Watkins, W.A., W.E. Schevill (1979). "Aerial observations of feeding behavior in four baleen whales: Eubalaena glacialis, Balaenoptera borealis, Megaptera novaeangliae, and Balaenoptera physalus". J. Mamm. 60: 155-163.</ref><ref name="weinrich">Weinrich, M.T., C.R. Belt, M.R. Schilling, and M. Marcy (1986). "Behavior of sei whales in the southern Gulf of Maine, summer 1986". Whalewatcher 20 (4): 4-7.</ref> It competes for food with a variety of other species, including clupeid fishes, basking sharks, and Right Whales. In the North Pacific, the Sei Whale feeds on similar zooplankton, in addition to larger organisms, including pelagic squid and fish the size of adult mackerel.<ref name="nemoto">Nemoto, T., and A. Kawamura (1977). "Characteristics of food habits and distribution of baleen whales with special reference to the abundance of North Pacific sei and Bryde's whales". Rep. Int. Whal. Commn Spec. Iss. 1: 80-87.</ref> Some fish in its diet are commercially important. Off central California, it feeds on anchovies from June through August, and on krill (Euphausia pacifica) during September and October.<ref name="rice77"/>

[edit] Life history

Mating occurs in temperate, low-latitude seas during the winter, and the gestation period is estimated to be 10 3/4 months,<ref name="lockyer and martin">Lockyer, C., and A.R. Martin (1983). "The sei whale off western Iceland. II. Age, growth and reproduction". Rep. Int. Whal. Commn 33: 465-476.</ref> 11 1/4 months,<ref name="lockyer77">Lockyer, C. (1977). "Some estimates of growth in the sei whale, Balaenoptera borealis". Rep. Int. Whal. Commn Spec. Iss. 1: 58-62.</ref> or one year,<ref name="risting">Risting, S (1928). "Whales and whale foetuses". Rapp. Cons. Explor. Mer 50: 1-122.</ref> depending on what model of fetal growth is used. A newborn weans from its mother at 6 or 9 months of age when it is 11 or 12 metres (36 to 39 ft) in length,<ref name="lockyer and martin"/> so weaning takes place on the feeding grounds in summer or autumn. Females reproduce every 2 to 3 years,<ref name="lockyer and martin"/> with as many as 6 foetuses being reported, but single births are far more common.<ref name="adw"/> The average age of sexual maturity of both sexes is 8 to 10 years,<ref name="lockyer and martin"/> at a length of around 12 metres (40 ft) for males and 13 metres (50 ft) for females.<ref name="acs"/> The whales can reach ages of up to 65 years.<ref name="wwf.com">WWF (November 13, 2006). Sei whale: A global open water diver. WWF Global Species Programme. Retrieved on 2006-12-01.</ref>

[edit] Vocalizations

Like other whales, the Sei Whale is known to make long, loud, low-frequency sounds. Relatively little is known about the specific calls made by the whale, but in 2003, observers noted Sei Whale calls in addition to broadband sounds that could be described as "growls" or "whooshes" off the coast of the Antarctic Peninsula.<ref name="mcdonald05">McDonald, M., Hildebrand, J., Wiggins, S., Thiele, D., Glasgow, D., and Moore, S. (December 2005). "Sei whale sounds recorded in the Antarctic". The Journal of the Acoustical Society of America 118 (6): 3941-3945.</ref> Many of the calls consisted of multiple parts with a change in frequency between the parts, which is a distinguishing feature of the Sei Whale's call when comparing it to other whales. Most calls lasted about one half of a second in length, and occurred in the 240 to 625 Hertz frequency, well within the normal range of sounds that most humans can hear. The vocal sequences are loud, and can reach intensities of 152 to 160 decibels relative to 1 micropascal (μPa) of sound pressure.<ref name="mcdonald05"/> For reference, an observer situated one metre from a whale when it was making its call would perceive a volume roughly equivalent to the volume of a jackhammer operating two metres away.<ref>Direct comparisons of sounds in water to sounds in air can be complicated, see this description for more information.</ref>

[edit] Habitat and migration

Sei Whales are found worldwide in a band stretching from Antarctica in the south to as far north as Iceland, although it is only rarely found in tropical waters.<ref name="nmfs"/> The difficulty of distinguishing Sei Whales at seas from their close relatives, Bryde's Whales and in some cases from Fin Whales, has created confusion about their distributional limits and frequency of occurrence, especially in warmer waters where Bryde's Whales are most common.

In the North Atlantic, the range of the Sei Whale extends from southern Europe or northwestern Africa to Norway in the east, and from the southern United States to West Greenland in the west.<ref name="Gambell85a"/> The southernmost confirmed records are strandings along the northern Gulf of Mexico and in the Greater Antilles.<ref name="mead"/> Throughout its range, the whale tends to avoid semi-enclosed bodies of water such as the Gulf of Mexico, the Gulf of St. Lawrence, Hudson Bay, the North Sea, and the Mediterranean Sea.<ref name="nmfs"/> It occurs predominantly in deep water, occurring most commonly over the continental slope,<ref name="CETAP">CETAP (1982). "Final Report of the Cetacean and Turtle Assessment Program, University of Rhode Island, to Bureau of Land Management". U.S. Department of the Interior. Ref. No. AA551-CT8-48. </ref> in basins situated between banks,<ref name="sutcliffe">Sutcliffe, W.H., Jr., P.F. Brodie (1977). “Whale distributions in Nova Scotia waters”, Fisheries & Marine Service Technical Report No. 722.</ref> or submarine canyon areas.<ref name="kenney87">Kenney, R.D., H.E. Winn (1987). "Cetacean biomass densities near submarine canyons compared to adjacent shelf/slope areas". Cont. Shelf Res. 7: 107-114.</ref>

In the North Pacific, the Sei Whale is found from 20°N to 23°N latitude in the winter, and from 35°N to 50°N latitude in the summer.<ref name="masaki76">Masaki, Y. (1976). "Biological studies on the North Pacific sei whale". Bull. Far Seas Fish. Res. Lab. 14: 1-104.</ref> Approximately 75% of the total population of Sei Whales in the North Pacific is found east of longitude 180°W,<ref name="horwood87"/> but there is a significant lack of information regarding the overall distribution of the whales in the North Pacific. Two whales tagged off California were later captured off Washington and British Columbia, revealing a possible link between these areas,<ref name="rice74">Rice, D.W. (1974). “Whales and whale research in the North Pacific”, Schervill, W.E. (ed.): The Whale Problem: a status report. Cambridge, MA: Harvard University Press, 170-195. ISBN 0-674-95075-5.</ref> but the lack of other tag recovery data makes these two cases inconclusive. In the Southern Hemisphere, summer distribution based upon historic catch data is between 40°S to 50°S latitude, while winter distribution is unknown.<ref name="mizroch84">Mizroch, S.A., D.W. Rice and J.M. Breiwick (1984). "The Sei Whale, Balaenoptera borealis". Mar. Fish. Rev. 46: 25-29.</ref>

In general, the Sei Whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter.<ref name="nmfs"/> In the northwest Atlantic, sightings and catch records suggest that the whale moves north along the shelf edge to arrive in the areas of Georges Bank, Northeast Channel, and Browns Bank by mid to late June. They are present off the south coast of Newfoundland in August and September, and a southbound migration begins moving west and south along the Nova Scotian shelf from mid-September to mid-November. Whales in the Labrador Sea as early as the first week of June may move farther northward to waters southwest of Greenland later in the summer.<ref name="mitchell and chapman">Mitchell, E., D.G. Chapman (1977). "Preliminary assessment of stocks of northwest Atlantic sei whales (Balaenoptera borealis)". Rep. Int. Whal. Commn Spec. Iss. 1: 117-120.</ref> In the northeast Atlantic, the Sei Whale winters as far south as West Africa and follows the continential slope northward in spring. Large females lead the northward migration and reach the Denmark Strait earlier and more reliably than other sexes and classes, arriving in mid-July and remaining through mid-September. In some years, males and younger females remain at lower latitudes during the summer months.<ref name="martin83"/>

Despite knowing some general trends in the migration pattern of the Sei Whale, exact migration routes are not known<ref name="martin83"/> and it is not easy to predict exactly where groups will appear from one year to the next. A particular location may one year see an influx of many whales only for them not to return for several years afterwards.<ref name="jonsgard and darling">Jonsgård, Å., K. Darling (1977). "On the biology of the eastern North Atlantic sei whale, Balaenoptera borealis Lesson". Rep. Int. Whal. Commn Spec. Iss. 1: 124-129.</ref> F.O. Kapel noted a correlation between the occasional appearance of the Sei Whale and the incursions of relatively warm waters off the Irminger Current off West Greenland.<ref name="kapel85">Kapel, F.O. (1985). "On the occurrence of sei whales (Balenoptera borealis) in West Greenland waters". Rep. Int. Whal. Commn 35: 349-352.</ref> Some evidence from tagging data indicates that individual Sei Whales return off the coast of Iceland on an annual basis.<ref name="sigurjonsson83">Sigurjónsson, J. (1983). "The cruise of the Ljósfari in the Denmark Strait (June-July 1981) and recent marking and sightings off Iceland". Rep. Int. Whal. Commn 33: 667-682.</ref>

[edit] Whaling

Main articles: Whaling and History of whaling

The development of explosive harpoons and steam-powered catcher boats in the late nineteenth century allowed the exploitation of previously unobtainable large whales by commercial whalers. Because of their quick speed and elusiveness,<ref name="sigurjónsson88">Sigurjónsson, J. (1988). "Operational factors of the Icelandic large whale fishery". Rep. Int. Whal. Commn 38: 327-333.</ref> and later because of their comparatively small yield of oil and meat, the Sei Whale was initially not generally hunted while sufficient stocks of Right Whales, Blue Whales, Fin Whales, and Humpback Whales were available. As these stocks became depleted, Sei Whales were hunted in earnest, particularly in the 1950s through the 1970s.<ref name="mfr"/>

[edit] North Atlantic

14,295 Sei Whales were captured in the North Atlantic Ocean between 1885 and 1984.<ref name="horwood87"/> They were hunted in large numbers off the coast of Norway and Scotland beginning in the late nineteenth and twentieth centuries,<ref name="jonsgard and darling"/> and in 1885 alone, more than 700 Sei Whales were killed off Finnmark, Norway.<ref name="andrews16">Andrews, R.C. (1916). "The sei whale (Balaenoptera borealis Lesson)". Mem. Am. Mus. Nat. Hist. New Ser. 1: 291-388.</ref> Sei Whale meat was a popular food in Norway, and it was the value of the meat that made the hunting of this difficult-to-catch species economically feasible in the early twentieth century.<ref>Ingebrigtsen, A. (1929). “Whales caught in the North Atlantic and other seas”, Rapports et Procès-verbaux des réunions, Cons. Perm. Int. L’Explor. Mer, Vol. LVI.. Copenhagen: Høst & Fils.</ref>

In Iceland, a total of 2,574 whales were taken from the Hvalfjörður whaling station between 1948 and 1985. Since the late 1960s or early 1970s, the Sei Whale has been second only to the Fin Whale as a preferred target of Icelandic whalers, with the demand for high-quality meat taking precedence over that for whale oil.<ref name="sigurjónsson88"/>

Small numbers of Sei Whales were taken off Spain, Portugal, and in the Strait of Gibraltar beginning in the 1920s.<ref name="aguilar and lens">Aguilar, A., and S. Lens (1981). "Preliminary report on Spanish whaling operations". Rep. Int. Whal. Commn 31: 639-643.</ref> In North America, a total of 825 Sei Whales were taken off the Nova Scotian shelf by whalers operating out of Blandford, Nova Scotia between 1966 and 1972,<ref name="mitchell and chapman"/> and small numbers of Sei Whales were taken by Norwegian and Danish whalers off West Greenland from the 1920s to the 1950s.<ref name="kapel85"/>

[edit] North Pacific

In the North Pacific, the total reported kill of Sei Whales by commercial whalers was 72,215 between 1910 and 1975,<ref name="horwood87"/> and 61,500 between 1947 and 1987.<ref name="barlow97">Barlow, J., K. A. Forney, P.S. Hill, R.L. Brownell, Jr., J.V. Carretta, D.P. DeMaster, F. Julian, M.S. Lowry, T. Ragen, and R.R. Reeves (1997). "U.S. Pacific marine mammal stock assessments: 1996" (PDF). NOAA Tech. Mem. NMFS-SWFSC-248. </ref> At shore stations in Japan and Korea, 300 to 600 Sei Whales were taken each year by whalers between 1911 and 1955. In 1959, the Japanese catch peaked when 1,340 whales were taken. Heavy exploitation by pelagic whalers in the North Pacific began in the early 1960s, with total catches averaging 3,643 per year from 1963 to 1974 (total 43,719; annual range 1,280 to 6,053).<ref name="tillman77">Tillman, M.F. (1977). "Estimates of population size for the North Pacific sei whale". Rep. Int. Whal. Commn Spec. Iss. 1: 98-106.</ref> In 1971, after a decade of high Sei Whale catch numbers, the species became scarce in Japanese waters.<ref name="CFWS42">Committee for Whaling Statistics (1942). International whaling statistics. Oslo: Committee for Whaling Statistics.</ref><ref name="mizroch84"/>

Off the coast of North America, Sei Whales were hunted by Canadians in British Columbia from the late 1950s to the mid 1960s, when the number of whales captured dropped to around 14 per year.<ref name="mfr"/> More than 2,000 were killed in British Columbia waters between 1962 and 1967.<ref name="pike69">Pike, G.C, and I.B. MacAskie (1969). "Marine mammals of British Columbia". Fish. Res. Bd. Canada Bull. 171.</ref> Between 1957 and 1971, California shore whalers captured 386 whales.<ref name="rice77"/> Commercial whaling for Sei Whales ended in the western North Pacific in 1975, and in the eastern North Pacific in 1971.

[edit] Southern Hemisphere

A total of 152,233 Sei Whales were taken in the Southern Hemisphere between 1910 and 1979.<ref name="horwood87"/> Whaling in the southern oceans originally targeted Humpback Whales. By 1913, this target species became rare and the catch of Fin and Blue Whales began to increase. As these species likewise became scarce, Sei Whale catches increased rapidly in the late 1950s and early 1960s.<ref name="mizroch84"/> The catch peaked in 1964 at over 20,000 Sei Whales, but by 1976, this number had dropped to below 2,000 and commercial whaling for the species ended in 1977.<ref name="mfr"/>

[edit] International protection

Image:Members of the International Whaling Commission.PNG

The Sei Whale did not have meaningful protection at the international level until 1970, when catch quotas for the North Pacific began to be set on a species basis by the International Whaling Commission (IWC). Prior to that time, the kill was limited only by whalers' ability to find the whales.<ref name="allen80">Allen, K.R. (1980). Conservation and Management of Whales. Seattle, WA: Univ. of Washington Press.</ref> The Sei Whale was given complete protection from commercial whaling in the North Pacific in 1976, and quotas on Sei Whales were introduced in the North Atlantic in 1977. With the moratorium on commercial whaling taking effect in the Northern Hemisphere in 1986, all legal whaling for Sei Whales stopped.<ref name="nmfs"/>

In the late 1970's, some "pirate" whaling took place in the eastern North Atlantic.<ref name="best92">Best, P.B. (1992). "Catches of fin whales in the North Atlantic by the M.V. Sierra (and associated vessels)". Rep. Int. Whal. Commn 42: 697-700.</ref> There is no direct evidence of illegal whaling in the North Pacific, although the acknowledged misreporting of whaling data by the Soviet Union<ref name="yablokov94">Yablokov, A.V. (1994). "Validity of whaling data". Nature 367: 108.</ref> means that catch data are not entirely reliable.

The species remained listed on the IUCN Red List of Threatened Species in 2000, categorised as "endangered".<ref name="iucn"/> Populations in the Southern Hemisphere are listed as CITES Appendix I, indicating that they are threatened with extinction if trade is not halted. Populations in the Northern Hemisphere are listed as CITES Appendix II, indicating that they are not necessarily threatened with extinction, but may become so if they are not listed.<ref name="adw"/>

[edit] Post-protection whaling

Since the moratorium on commercial whaling, some Sei Whales have been taken by Icelandic and Japanese whalers under the IWC's scientific research programme. Iceland carried out four years of scientific whaling between 1986 and 1989, catching up to 40 Sei Whales a year.<ref name="wwf-Iceland">WWF-International (2003-08-07). WWF condemns Iceland’s announcement to resume whaling. Press release. Retrieved on 2006-11-10.</ref>

Japanese scientists kill approximately 50 Sei Whales each year for this purpose. The main focus of the research is to examine what Sei Whales eat and to determine the level of competition between whales and fisheries. Dr. Seiji Ohsumi, Director General of the Institute of Cetacean Research in Tokyo, said "It is estimated that whales consume 3 to 5 times the amount of marine resources as are caught for human consumption, so our whale research is providing valuable information required for improving the management of all our marine resources."<ref name="icr02a">The Institute of Cetacean Research, Tokyo, Japan (2002-03-01). Japan not catching endangered whales. Press release. Retrieved on 2006-11-10.</ref> He later added that "...Sei Whales are the second most abundant species of whale in the western North Pacific, with an estimated population of over 28,000 animals. [It is] clearly not endangered."<ref name="icr02b">The Institute of Cetacean Research, Tokyo, Japan (2002-05-20). Japan's senior whale scientist responds to New York Times advertisement. Press release. Retrieved on 2006-11-10.</ref>

Environmental campaigners dispute the necessity of the research, saying that it is known that Sei Whales feed primarily on squid and plankton not hunted by humans, and only rarely on fish. They claim that the programme is "nothing more than a plan designed to keep the whaling fleet in business, and the need to use whales as the scapegoat for over-fishing by humans."<ref name="wwf05"/> The scientific quality of the research obtained under the scientific whaling programme has been criticised as being very poor; at the 2001 meeting of the IWC Scientific Committee, 32 scientists submitted a document expressing their belief that the Japanese programme lacked scientific rigour and would not meet minimum standards of academic review that are widely used in science world-wide.<ref name="clapham02">Clapham, P. et al. (2002). "Relevance of JARPN II to management, and a note on scientific standards. Report of the IWC Scientific Committee, Annex Q1". Journal of Cetacean Research and Management (supplement): 395-396.</ref>

[edit] Population estimates

The global population of the Sei Whale is estimated at only 54,000, about one fifth of the population before the era of commercial whaling.<ref name="acs"/> In the North Atlantic, a 1991 study that reviewed the history of catches and catch per unit effort (CPUE) data produced a population estimate of 4,000.<ref name="braham92">Braham, H. (1992). "Endangered whales: Status update". Alaska Fisheries Science Center, Seattle, WA. </ref> This low-precision estimate is not considered a true scientific index of abundance.<ref name="blaylock95">Blaylock, R.A., J.W. Haim, L.J. Hansen, D.L. Palka, and G.T. Waring (1995). "U.S. Atlantic and Gulf of Mexico stock assessments". U.S. Dept. of Commerce, NOAA Tech. Memo NMFS-SEFSC-363. </ref> Sei Whales were said to have been scarce in the 1960's and early 1970's off northern Norway, where plentiful numbers were taken at the end of the nineteenth century through the Second World War.<ref name="jonsgard74">Jonsgård, Å. (1974). “On whale exploitation in the eastern part of the North Atlantic Ocean”, The whale problem. Cambridge, MA: Harvard University Press, 97-107.</ref> One possible explanation for this disappearance is that the whales were overexploited,<ref name="jonsgard74"/> while an alternative explanation is that a drastic reduction in copepod stocks in the northeastern Atlantic during the late 1960's caused a change in Sei Whale distribution.<ref name="cattanach">Cattanach, K.L., J. Sigurjonsson, S.T. Buckland, and Th. Gunnlaugsson (1993). "Sei whale abundance in the North Atlantic, estimated from NASS-87 and NASS-89 data". Rep. Int. Whal. Commn 43: 315-321.</ref> Surveys in the Denmark Strait found 1,290 whales in 1987, and 1,590 whales in 1989.<ref name="cattanach"/> Population levels off Nova Scotia are estimated to be between 1,393 and 2,248, with a minimum estimate of 870.<ref name="mitchell and chapman"/>

A study in 1977 produced a population estimate for the Pacific Ocean of 9,110, based upon the history of catches and CPUE data.<ref name="tillman77"/> This figure is disputed as outdated by Japanese whaling interests, who in 2002 claimed that the population of Sei Whales in the western North Pacific was over 28,000 whales,<ref name="icr02b"/> but this figure has not been accepted by the scientific community.<ref name="wwf05"/> In California waters, there was only one confirmed and five possible sightings from 1991,<ref name="hill92">Hill, P.S. and J. Barlow (1992). "Report of a marine mammal survey of the California coast aboard the research vessel "MacArthur" July 28 - November 5, 1991." (PDF). U.S. Dept. Commerce, NOAA Technical Memo NMFS-SWFSC-169. </ref><ref name="carretta93">Carretta, J.V. and K.A. Forney (1993). "Report of two aerial surveys for marine mammals in California coastal waters utilizing a NOAA DeHavilland Twin Otter aircraft: March 9 - April 7, 1991 and February 8 - April 6, 1992" (PDF). U.S. Dept. Commerce, NOAA Technical Memo NMFS-SWFSC-185. </ref> 1992,<ref name="carretta93"/> and 1993<ref name="mangels94">Mangels, K.F. and T. Gerrodette (1994). "Report of cetacean sightings during a marine mammal survey in the eastern Pacific Ocean and the Gulf of California aboard the NOAA ships "MacArthur" and "David Starr Jordan" July 28 - November 6, 1993" (PDF). U.S. Dept. Commerce, NOAA Technical Memo NMFS-SWFSC-211. </ref> aerial and ship surveys, and there were no confirmed sightings off Oregon and Washington aerial surveys. Prior to commercial whaling activities, there were an estimated 42,000 Sei Whales in the North Pacific.<ref name="tillman77"/> By the end of the period of exploitation (1974), there numbers had been reduced to between 7,260 and 12,620.<ref name="tillman77"/>

In the Southern Hemisphere, Sei Whale abundance estimates range between 9,800 and 12,000 whales, based upon the history of catches and CPUE in the southern oceans.<ref name="braham92"/> The IWC reported an estimate of 9,718 whales based upon survey data between 1978 and 1988.<ref name="IWC96">IWC (1996). "Report of the sub-committee on Southern Hemisphere baleen whales, Annex E". Rep. Int. Whal. Commn 46: 117-131.</ref> Prior to commercial whaling, there were an estimated 65,000 Sei Whales living in the Southern Hemisphere.<ref name="braham92"/>

[edit] See also

</div>

• List of whale species
• Whaling in Japan
• Whaling in Iceland

[edit] References

[edit] General References

[edit] External links

• ARKive - images and movies of the sei whale (Balaenoptera borealis)
• News report on Japanese whalers hunting Sei Whales in 2002/2003ms:Ikan Paus Sei

zh-min-nan:Sei Hái-ang da:Sejhval de:Seiwal es:Balaenoptera borealis fr:Rorqual boréal nl:Noordse vinvis pl:Sejwal pt:Baleia-sei sv:Sejval