Sei Whale
Encyclopedia
The sei whale Balaenoptera borealis, is a baleen whale
, the third-largest rorqual
after the blue whale
and the fin whale
. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar
and tropical
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT), the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
s, krill
, and other zooplankton
. It is among the fastest of all cetacea
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
word for pollock
, a fish that appears off the coast of Norway
at the same time of the year as the sei whale.
Following large-scale commercial whaling
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken, the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
and Japan
. As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual. Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner. Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
naturalist
Roy Chapman Andrews
compared the sei whale to the cheetah
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word 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
. 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.
Sei whales are rorqual
s (family Balaenopteridae), baleens that includes the humpback whale
, the blue whale
, the Bryde's whale
, the fin whale
, and the minke whale
. Rorquals take their name from the Norwegian
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
, also called the whalebone whales or great whales, as long ago as the middle Miocene
. However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii). Their ranges do not overlap.
were slightly longer than 16 metres (52.5 ft). At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum 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 ectoparasitic
copepod
s (Penella spp.), lamprey
s (family Petromyzontidae), or possibly "cookie-cutter" sharks
(Isistius brasiliensis). It has a tall, sickle
-shaped dorsal fin
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
ation pattern, and scarring have been used to a limited extent in photo-identification
studies. The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Adults have 300–380 ashy-black baleen plates on each side of the mouth, each about 48 centimetres (18.9 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
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise 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.
This rorqual is a filter feeder
, using its baleen plate
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
, including zooplankton
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior., and analyzing fecal matter
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species. The whale competes for food against clupeid
fish (herring
and its relatives), basking shark
s, and right whale
s.
In the North Atlantic
, it feeds primarily on calanoid copepods
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
, in particular Meganyctiphanes norvegica and Thysanoessa inermis. In the North Pacific
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
, Todarodes pacificus pacificus, and small fish, including members of the Engraulis
(anchovies), Cololabis
(sauries), Sardinops
(pilchards), and Trachurus
(jack mackerels) genera.
The sei whale (icon or ˈ), Balaenoptera borealis, is a baleen whale
, the third-largest rorqual
after the blue whale
and the fin whale
.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters.
It avoids polar
and tropical
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT),
the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
s, krill
, and other zooplankton
.
It is among the fastest of all cetacea
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
word for pollock
, a fish that appears off the coast of Norway
at the same time of the year as the sei whale.
Following large-scale commercial whaling
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken,
the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
and Japan
.
As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual.
Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner.
Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
naturalist
Roy Chapman Andrews
compared the sei whale to the cheetah
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word 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
. 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.
Sei whales are rorqual
s (family Balaenopteridae), baleens that includes the humpback whale
, the blue whale
, the Bryde's whale
, the fin whale
, and the minke whale
. Rorquals take their name from the Norwegian
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
, also called the whalebone whales or great whales, as long ago as the middle Miocene
.
However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii).
Their ranges do not overlap.
were slightly longer than 16 metres (52.5 ft).
At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum 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 ectoparasitic
copepod
s (Penella spp.),
lamprey
s (family Petromyzontidae),
or possibly "cookie-cutter" sharks
(Isistius brasiliensis).
It has a tall, sickle
-shaped dorsal fin
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
ation pattern, and scarring have been used to a limited extent in photo-identification
studies.
The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Adults have 300–380 ashy-black baleen plates on each side of the mouth, each about 48 centimetres (18.9 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
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
or in groups of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise 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.
This rorqual is a filter feeder
, using its baleen plate
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
, including zooplankton
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior.,
and analyzing fecal matter
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.
The whale competes for food against clupeid
fish (herring
and its relatives), basking shark
s, and right whale
s.
In the North Atlantic
, it feeds primarily on calanoid copepods
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
, in particular Meganyctiphanes norvegica and Thysanoessa inermis.
In the North Pacific
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
, Todarodes pacificus pacificus,
and small fish, including members of the Engraulis
(anchovies), Cololabis
(sauries), Sardinops
(pilchards), and Trachurus
(jack mackerels) genera.
The sei whale (icon or ˈ), Balaenoptera borealis, is a baleen whale
, the third-largest rorqual
after the blue whale
and the fin whale
.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters.
It avoids polar
and tropical
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT),
the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
s, krill
, and other zooplankton
.
It is among the fastest of all cetacea
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
word for pollock
, a fish that appears off the coast of Norway
at the same time of the year as the sei whale.
Following large-scale commercial whaling
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken,
the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
and Japan
.
As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual.
Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner.
Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
naturalist
Roy Chapman Andrews
compared the sei whale to the cheetah
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word 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
. 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.
Sei whales are rorqual
s (family Balaenopteridae), baleens that includes the humpback whale
, the blue whale
, the Bryde's whale
, the fin whale
, and the minke whale
. Rorquals take their name from the Norwegian
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
, also called the whalebone whales or great whales, as long ago as the middle Miocene
.
However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii).
Their ranges do not overlap.
were slightly longer than 16 metres (52.5 ft).
At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum 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 ectoparasitic
copepod
s (Penella spp.),
lamprey
s (family Petromyzontidae),
or possibly "cookie-cutter" sharks
(Isistius brasiliensis).
It has a tall, sickle
-shaped dorsal fin
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
ation pattern, and scarring have been used to a limited extent in photo-identification
studies.
The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Adults have 300–380 ashy-black baleen plates on each side of the mouth, each about 48 centimetres (18.9 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
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
or in groups of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise 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.
This rorqual is a filter feeder
, using its baleen plate
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
, including zooplankton
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior.,
and analyzing fecal matter
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.
The whale competes for food against clupeid
fish (herring
and its relatives), basking shark
s, and right whale
s.
In the North Atlantic
, it feeds primarily on calanoid copepods
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
, in particular Meganyctiphanes norvegica and Thysanoessa inermis.
In the North Pacific
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
, Todarodes pacificus pacificus,
and small fish, including members of the Engraulis
(anchovies), Cololabis
(sauries), Sardinops
(pilchards), and Trachurus
(jack mackerels) genera.
Some of these fish are commercially important. Off central California
, the whale may feed on anchovies
between June and August, and on krill
(Euphausia pacifica) during September and October. In the Southern Hemisphere, prey species include the copepods Neocalanus tonsus, Calanus simillimus, and Drepanopus pectinatus, as well as the euphausids Euphausia superba and Euphausia vallentini. Sei whales also eat sardines.
occurs in temperate, subtropical seas during the winter. Gestation
is estimated to vary around 10 months,
11 months,
or one year,
depending which model of foetal
growth is used. The different estimates result from scientists' inability to observe an entire pregnancy; most reproductive data for baleen whales were obtained from animals caught by commercial whalers, which offers only a single snapshot of fetal growth. Researchers attempt to extrapolate conception dates by comparing fetus size and characteristics with newborns.
A newborn is wean
ed from its mother at 6–9 months of age, when it is 11–12 m (36.1–39.4 ft) long, so weaning takes place at the summer or autumn feeding grounds. Females reproduce every 2–3 years, with as many as six fetuses reported, but single births are far more common. The average age of sexual maturity
of both sex
es is 8–10 years, at a length of around 12 metres (39.4 ft) for males and 13 metres (42.7 ft) for females. The whales can reach ages of up to 65 years.
.
Many calls consisted of multiple parts at different frequencies. This combination distinguishes the their calls from those of other whales. Most calls lasted about a half second, and occurred in the 240–625 hertz
range, well within the range of human hearing. The maximum volume of the vocal sequences is reported as 156 decibel
s relative to 1 micropascal (μPa)
at a reference distance of one meter. An observer situated one meter from a vocalizing whale would perceive a volume roughly equivalent to the volume of a jackhammer operating two meters away.
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Sei whales live in all oceans, although rarely in polar
or tropical
waters. The difficulty of distinguishing them at sea from their close relatives, Bryde's whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde's whales are most common.
In the North Atlantic, its range extends from southern Europe
or northwestern Africa to Norway
, and from the southern United States
to Greenland
. The southernmost confirmed records are strandings along the northern Gulf of Mexico
and in the Greater Antilles
. Throughout its range, the whale tends to avoid semi-enclosed bodies of water, such as the Gulf of Mexico, the Gulf of Saint Lawrence
, Hudson Bay
, the North Sea
, and the Mediterranean Sea
. It occurs predominantly in deep water, occurring most commonly over the continental slope
,
in basins situated between banks,
or submarine canyon
areas.
In the North Pacific, it ranges from 20°N
–23°N
latitude
in the winter, and from 35°N
–50°N
latitude in the summer.
Approximately 75% of the North Pacific population lives east of the International Date Line
, but there is little information regarding the North Pacific distribution. Two whales tagged in deep waters off California
were later recaptured off Washington and British Columbia
, revealing a possible link between these areas,
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 and 50°S latitude, while winter distribution is unknown.
, 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 Scotia
n 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.
In the northeast Atlantic, the sei whale winters as far south as West Africa
, and follows the continental 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.
Despite knowing some general migration patterns, exact routes are not known and scientists cannot readily predict exactly where groups will appear from one year to the next.
F.O. Kapel noted a correlation between appearances west of Greenland and the incursion of relatively warm waters from the Irminger Current
into that area.
Some evidence from tagging data indicates individuals return off the coast of Iceland
on an annual basis.
The development of explosive harpoon
s and steam-powered whaling ships in the late nineteenth century brought previously unobtainable large whales within reach of commercial whalers
. Initially their speed and elusiveness,
and later the comparatively small yield of oil
and meat partially protected them. Once stocks of more profitable right whale
s, blue whales, fin whales, and humpback whales became depleted, sei whales were hunted in earnest, particularly from 1950 to 1980.
and Scotland
beginning in the late nineteenth and early twentieth centuries, and in 1885 alone, more than 700 were caught off Finnmark, Norway
.
Their meat was a popular Norwegian food. The meat's value made the hunting of this difficult-to-catch species profitable in the early twentieth century.
In Iceland, a total of 2,574 whales were taken from the Hvalfjörður
whaling station between 1948 and 1985. Since the late 1960s to early 1970s, the sei whale has been second only to the fin whale as the preferred target of Icelandic whalers, with meat in greater demand than whale oil
, the prior target.
Small numbers were taken off the Iberian Peninsula
, beginning in the 1920s by Spanish whalers,
off the Nova Scotia
n shelf in the late 1960s and early 1970s by Canadian whalers, and off the coast of West Greenland from the 1920s to the 1950s by Norwegian and Danish whalers.
Shore stations in Japan
and Korea
, processed 300–600 each year between 1911 and 1955. In 1959, the Japanese catch peaked at 1,340. Heavy exploitation in the North Pacific began in the early 1960s, with catches averaging 3,643 per year from 1963 to 1974 (total 43,719; annual range 1,280–6,053).
In 1971, after a decade of high catches, it became scarce in Japanese waters, ending commercial whaling in 1975.
Off the coast of North America
, sei whales were hunted off British Columbia
from the late 1950s to the mid 1960s, when the number of whales captured dropped to around 14 per year. More than 2,000 were caught in British Columbia waters between 1962 and 1967.
Between 1957 and 1971, California
shore stations processed 386 whales. Commercial Sei whaling ended in the eastern North Pacific in 1971.
between 1910 and 1979. Whaling in southern oceans
originally targeted humpback whales. By 1913, this 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. The catch peaked in 1964-65 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.
ic and Japan
ese whalers under the IWC's scientific research programme. Iceland carried out four years of scientific whaling between 1986 and 1989, killing up to 40 sei whales a year.
Japanese scientists catch about 50 sei whales each year for this purpose. The research is conducted by the Institute of Cetacean Research
(ICR) in Tokyo
, a privately-funded, nonprofit institution. The main focus of the research is to examine what they eat and to assess the competition between whales and fisheries. Dr. Seiji Ohsumi, Director General of the ICR, said,
He later added,
Conservation groups, such as the World Wildlife Fund
, dispute the value of this research, claiming that sei whales feed primarily on squid
and plankton
which are not hunted by humans, and only rarely on fish
. They say that the program is
At the 2001 meeting of the IWC Scientific Committee, 32 scientists submitted a document expressing their belief that the Japanese program lacked scientific rigour and would not meet minimum standards of academic review
.
In 2010, a Los Angeles restaurant confirmed to be serving sei whale meat
was closed by its owners after prosecution by authorities for handling a protected species.
The sei whale did not have meaningful international protection until 1970, when the International Whaling Commission
(IWC) first set catch quotas for the North Pacific for individual species. Before quotas, there were no legal limits.
Complete protection from commercial whaling in the North Pacific came in 1976.
Quotas on sei whales in the North Atlantic began in 1977. Southern Hemisphere stocks were protected in 1979. Facing mounting evidence that several whale species were threatened with extinction, the IWC established a complete moratorium on commercial whaling beginning in 1986.
In the late 1970s, some "pirate" whaling took place in the eastern North Atlantic.
There is no direct evidence of illegal whaling in the North Pacific, although the acknowledged misreporting of whaling data by the Soviet Union
means that catch data are not entirely reliable.
The species remained listed on the IUCN Red List of Threatened Species
in 2000, categorized as "endangered". Northern Hemisphere populations are listed as CITES Appendix II, indicating they are not immediately threatened with extinction, but may become so if they are not listed. Populations in the Southern Hemisphere
are listed as CITES Appendix I, indicating they are threatened with extinction if trade is not halted.
The Sei whale is listed on both Appendix I"Appendix I and Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009. and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS
). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them and also on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
Sei whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU)and the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas(ACCOBAMS
)
The species is listed as endangered by the U.S. government National Marine Fisheries Service
under the U.S. Endangered Species Act
.
Sei whales were said to have been scarce in the 1960s and early 1970s off northern Norway
.
One possible explanation for this disappearance is that the whales were overexploited
. The drastic reduction in northeastern Atlantic copepod
stocks during the late 1960s may be another culprit.
Surveys in the Denmark Strait
found 1,290 whales in 1987, and 1,590 whales in 1989. Nova Scotia
's population estimates are between 1,393 and 2,248, with a minimum of 870.
A 1977 study estimated Pacific Ocean
totals of 9,110, based upon catch and CPUE
data. Japanese interests claim this figure is outdated, and in 2002 claimed the western North Pacific population was over 28,000, a figure not accepted by the scientific community. In California
waters, there was only one confirmed and five possible sightings by 1991 to 1993 aerial and ship surveys,
and there were no confirmed sightings off Oregon
and Washington. Prior to commercial whaling, the North Pacific hosted an estimated 42,000. By the end of whaling, the population was down to between 7,260 and 12,620.
In the Southern Hemisphere
, population estimates range between 9,800 and 12,000, based upon catch history and CPUE. The IWC estimated 9,718 whales based upon survey data between 1978 and 1988.
Prior to commercial whaling, there were an estimated 65,000.
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, the third-largest rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
after the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
and the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
and tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT), the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, and other zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. It is among the fastest of all cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, a fish that appears off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time of the year as the sei whale.
Following large-scale commercial whaling
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken, the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
Etymology
The species was first officially described by French naturalist René Primevère Lesson in 1828, but an earlier description was given by Karl RudolphiKarl Rudolphi
Karl Asmund Rudolphi was a Swedish-born naturalist, who is credited with being the "father of helminthology"....
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual. Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner. Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Roy Chapman Andrews
Roy Chapman Andrews
Roy Chapman Andrews was an American explorer, adventurer and naturalist who became the director of the American Museum of Natural History. He is primarily known for leading a series of expeditions through the fragmented China of the early 20th century into the Gobi Desert and Mongolia...
compared the sei whale to the cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time as the pollock, both coming to feed on the abundant plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. 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.
Taxonomy
The sei was classified as Balaena rostraia, Balaena borealis, Bataenoptera laticeps, and Eulama physalus, among others, before Lesson's alternative Balaenoptera borealis was formalized.Sei whales are rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
s (family Balaenopteridae), baleens that includes the humpback whale
Humpback Whale
The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the...
, the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
, the Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
, and the minke whale
Minke Whale
Minke whale , or lesser rorqual, is a name given to two species of marine mammal belonging to a clade within the suborder of baleen whales. The minke whale was given its official designation by Lacepède in 1804, who described a dwarf form of Balænoptera acuto-rostrata...
. Rorquals take their name from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, also called the whalebone whales or great whales, as long ago as the middle Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
. However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii). Their ranges do not overlap.
Description
The sei whale is the third-largest Balaenopteridae, after the blue whale (up to 180 tonnes, 200 tons) and the fin whale (up to 70 tonnes, 77 tons). Mature adults typically measure between 12–15 m (39.4–49.2 ft) and weigh 20–30 t (19.7–29.5 ). The southern sei whale is larger than the northern. Females are considerably larger than males. The largest known sei whale measured 20 metres (65.6 ft), and weighed between 40–45 t (39.4–44.3 ). The largest specimens taken off IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
were slightly longer than 16 metres (52.5 ft). At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
Anatomy
The whale's body is typically a dark steel grey with irregular light grey to white markings on the ventral surface, or towards the front of the lower body. The whale has a series of 32–60 pleatPleat
A pleat is a type of fold formed by doubling fabric back upon itself and securing it in place. It is commonly used in clothing and upholstery to gather a wide piece of fabric to a narrower circumference....
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum to the paired blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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 ectoparasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s (Penella spp.), lamprey
Lamprey
Lampreys are a family of jawless fish, whose adults are characterized by a toothed, funnel-like sucking mouth. Translated from an admixture of Latin and Greek, lamprey means stone lickers...
s (family Petromyzontidae), or possibly "cookie-cutter" sharks
Cookiecutter shark
The cookiecutter shark , also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded from as deep as . It migrates vertically up to every day, approaching the...
(Isistius brasiliensis). It has a tall, sickle
Sickle
A sickle is a hand-held agricultural tool with a variously curved blade typically used for harvesting grain crops or cutting succulent forage chiefly for feeding livestock . Sickles have also been used as weapons, either in their original form or in various derivations.The diversity of sickles that...
-shaped dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
ation pattern, and scarring have been used to a limited extent in photo-identification
Wildlife photo-identification
Photo-identification is a technique used into identify and track individuals of a wild animal study population over time. It relies on capturing photographs of distinctive characteristics such as skin patterns and scars from the animal...
studies. The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Nail (anatomy)
A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals....
-like keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
that frays out into whitish fine hairs on the ends inside the mouth near the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
Life history
Sei whales usually travel alone or in groups of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structureSocial structure
Social structure is a term used in the social sciences to refer to patterned social arrangements in society that are both emergent from and determinant of the actions of the individuals. The usage of the term "social structure" has changed over time and may reflect the various levels of analysis...
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives. The blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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.
Feeding
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
, using its baleen plate
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
, including zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior., and analyzing fecal matter
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species. The whale competes for food against clupeid
Clupeidae
Clupeidae is the family of the herrings, shads, sardines, hilsa and menhadens. It includes many of the most important food fishes in the world.-Description and biology:...
fish (herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
and its relatives), basking shark
Basking shark
The basking shark is the second largest living fish, after the whale shark. It is a cosmopolitan migratory species, found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder and has anatomical adaptations to filter feeding, such as a greatly enlarged...
s, and right whale
Right whale
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund....
s.
In the North Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, it feeds primarily on calanoid copepods
Calanoida
Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, in particular Meganyctiphanes norvegica and Thysanoessa inermis. In the North Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
Japanese Flying Squid
The Japanese Flying Squid or Japanese Common Squid, Todarodes pacificus, is a squid of the family Ommastrephidae. This animal lives in the northern Pacific Ocean, in the area surrounding Japan, up the full coast of China up to Russia, then spreading across the Bering Straight over towards the lower...
, Todarodes pacificus pacificus, and small fish, including members of the Engraulis
Engraulis
Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis albidus Borsa, Collet & J. D. Durand, 2004* Engraulis anchoita Carl Hubbs & Marini, 1935 * Engraulis australis Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis...
(anchovies), Cololabis
Cololabis
Cololabis is a genus of sauries. The name is derived from the Greek word kolos, meaning "short", and the Latin word labia, meaning "lips". There are two species....
(sauries), Sardinops
South American pilchard
The South American pilchard, Sardinops sagax, is a sardine of the Family Clupeidae, the only member of the genus Sardinops, found in the indo-Pacific oceans. Their length is up to 40 cm...
(pilchards), and Trachurus
Trachurus
Jack mackerels are marine fishes in the Trachurus genus of the Carangidae family. The type species of the genus is the Atlantic horse mackerel, Trachurus trachurus. The name of the genus is derived from the Greek word trachys, meaning "rough", and the Greek word oura, meaning "tail"...
(jack mackerels) genera.
The sei whale (icon or ˈ), Balaenoptera borealis, is a baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, the third-largest rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
after the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
and the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters.
It avoids polar
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
and tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT),
the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, and other zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
.
It is among the fastest of all cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, a fish that appears off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time of the year as the sei whale.
Following large-scale commercial whaling
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken,
the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
.
As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
Etymology
The species was first officially described by French naturalist René Primevère Lesson in 1828, but an earlier description was given by Karl RudolphiKarl Rudolphi
Karl Asmund Rudolphi was a Swedish-born naturalist, who is credited with being the "father of helminthology"....
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual.
Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner.
Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Roy Chapman Andrews
Roy Chapman Andrews
Roy Chapman Andrews was an American explorer, adventurer and naturalist who became the director of the American Museum of Natural History. He is primarily known for leading a series of expeditions through the fragmented China of the early 20th century into the Gobi Desert and Mongolia...
compared the sei whale to the cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time as the pollock, both coming to feed on the abundant plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. 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.
Taxonomy
The sei was classified as Balaena rostraia, Balaena borealis, Bataenoptera laticeps, and Eulama physalus, among others, before Lesson's alternative Balaenoptera borealis was formalized.Sei whales are rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
s (family Balaenopteridae), baleens that includes the humpback whale
Humpback Whale
The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the...
, the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
, the Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
, and the minke whale
Minke Whale
Minke whale , or lesser rorqual, is a name given to two species of marine mammal belonging to a clade within the suborder of baleen whales. The minke whale was given its official designation by Lacepède in 1804, who described a dwarf form of Balænoptera acuto-rostrata...
. Rorquals take their name from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, also called the whalebone whales or great whales, as long ago as the middle Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
.
However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii).
Their ranges do not overlap.
Description
The sei whale is the third-largest Balaenopteridae, after the blue whale (up to 180 tonnes, 200 tons) and the fin whale (up to 70 tonnes, 77 tons). Mature adults typically measure between 12–15 m (39.4–49.2 ft) and weigh 20–30 t (19.7–29.5 ). The southern sei whale is larger than the northern. Females are considerably larger than males. The largest known sei whale measured 20 metres (65.6 ft), and weighed between 40–45 t (39.4–44.3 ). The largest specimens taken off IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
were slightly longer than 16 metres (52.5 ft).
At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
Anatomy
The whale's body is typically a dark steel grey with irregular light grey to white markings on the ventral surface, or towards the front of the lower body. The whale has a series of 32–60 pleatPleat
A pleat is a type of fold formed by doubling fabric back upon itself and securing it in place. It is commonly used in clothing and upholstery to gather a wide piece of fabric to a narrower circumference....
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum to the paired blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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 ectoparasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s (Penella spp.),
lamprey
Lamprey
Lampreys are a family of jawless fish, whose adults are characterized by a toothed, funnel-like sucking mouth. Translated from an admixture of Latin and Greek, lamprey means stone lickers...
s (family Petromyzontidae),
or possibly "cookie-cutter" sharks
Cookiecutter shark
The cookiecutter shark , also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded from as deep as . It migrates vertically up to every day, approaching the...
(Isistius brasiliensis).
It has a tall, sickle
Sickle
A sickle is a hand-held agricultural tool with a variously curved blade typically used for harvesting grain crops or cutting succulent forage chiefly for feeding livestock . Sickles have also been used as weapons, either in their original form or in various derivations.The diversity of sickles that...
-shaped dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
ation pattern, and scarring have been used to a limited extent in photo-identification
Wildlife photo-identification
Photo-identification is a technique used into identify and track individuals of a wild animal study population over time. It relies on capturing photographs of distinctive characteristics such as skin patterns and scars from the animal...
studies.
The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Nail (anatomy)
A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals....
-like keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
that frays out into whitish fine hairs on the ends inside the mouth near the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
Life history
Sei whales usually travel aloneor in groups of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure
Social structure
Social structure is a term used in the social sciences to refer to patterned social arrangements in society that are both emergent from and determinant of the actions of the individuals. The usage of the term "social structure" has changed over time and may reflect the various levels of analysis...
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives. The blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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.
Feeding
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
, using its baleen plate
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
, including zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior.,
and analyzing fecal matter
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.
The whale competes for food against clupeid
Clupeidae
Clupeidae is the family of the herrings, shads, sardines, hilsa and menhadens. It includes many of the most important food fishes in the world.-Description and biology:...
fish (herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
and its relatives), basking shark
Basking shark
The basking shark is the second largest living fish, after the whale shark. It is a cosmopolitan migratory species, found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder and has anatomical adaptations to filter feeding, such as a greatly enlarged...
s, and right whale
Right whale
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund....
s.
In the North Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, it feeds primarily on calanoid copepods
Calanoida
Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, in particular Meganyctiphanes norvegica and Thysanoessa inermis.
In the North Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
Japanese Flying Squid
The Japanese Flying Squid or Japanese Common Squid, Todarodes pacificus, is a squid of the family Ommastrephidae. This animal lives in the northern Pacific Ocean, in the area surrounding Japan, up the full coast of China up to Russia, then spreading across the Bering Straight over towards the lower...
, Todarodes pacificus pacificus,
and small fish, including members of the Engraulis
Engraulis
Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis albidus Borsa, Collet & J. D. Durand, 2004* Engraulis anchoita Carl Hubbs & Marini, 1935 * Engraulis australis Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis...
(anchovies), Cololabis
Cololabis
Cololabis is a genus of sauries. The name is derived from the Greek word kolos, meaning "short", and the Latin word labia, meaning "lips". There are two species....
(sauries), Sardinops
South American pilchard
The South American pilchard, Sardinops sagax, is a sardine of the Family Clupeidae, the only member of the genus Sardinops, found in the indo-Pacific oceans. Their length is up to 40 cm...
(pilchards), and Trachurus
Trachurus
Jack mackerels are marine fishes in the Trachurus genus of the Carangidae family. The type species of the genus is the Atlantic horse mackerel, Trachurus trachurus. The name of the genus is derived from the Greek word trachys, meaning "rough", and the Greek word oura, meaning "tail"...
(jack mackerels) genera.
The sei whale (icon or ˈ), Balaenoptera borealis, is a baleen whale
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, the third-largest rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
after the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
and the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
.
It inhabits most oceans and adjoining seas, and prefers deep offshore waters.
It avoids polar
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
and tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical
Subtropics
The subtropics are the geographical and climatical zone of the Earth immediately north and south of the tropical zone, which is bounded by the Tropic of Cancer and the Tropic of Capricorn, at latitudes 23.5°N and 23.5°S...
waters.
Reaching 20 metres (65.6 ft) long and weighing as much as 28 tonnes (27.6 LT),
the sei whale daily consumes an average of 900 kilograms (1,984.2 lb) of food, primarily copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, and other zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
.
It is among the fastest of all cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns, and can reach speeds of up to 50 kilometres per hour (31.1 mph) (27 knots) over short distances. The whale's name comes from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, a fish that appears off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time of the year as the sei whale.
Following large-scale commercial whaling
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
during the late-nineteenth and twentieth centuries, when over 255,000 whales were taken,
the sei whale is now internationally protected, although limited hunting occurs under controversial research programmes conducted by Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
.
As of 2008, its worldwide population was about 80,000, nearly a third of its pre-whaling population.
Etymology
The species was first officially described by French naturalist René Primevère Lesson in 1828, but an earlier description was given by Karl RudolphiKarl Rudolphi
Karl Asmund Rudolphi was a Swedish-born naturalist, who is credited with being the "father of helminthology"....
in 1822 (although he assumed it was a minke whale, Balaenoptera acutorostrala), leading to occasional references to sei whales as Rudolphi's rorqual.
Additional names include pollack whale, coalfish whale, sardine whale, or Japan finner.
Additionally, it has been referred to as the lesser fin whale because it somewhat resembles the fin whale. The American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Roy Chapman Andrews
Roy Chapman Andrews
Roy Chapman Andrews was an American explorer, adventurer and naturalist who became the director of the American Museum of Natural History. He is primarily known for leading a series of expeditions through the fragmented China of the early 20th century into the Gobi Desert and Mongolia...
compared the sei whale to the cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...
, because it can swim at great speeds "for a few hundred yards", but it "soon tires if the chase is long" and "does not have the strength and staying power of its larger relatives".
Sei is the Norwegian word for pollock
Pollock
Pollock is the common name used for either of the two species of marine fish in the Pollachius genus. Both P. pollachius and P. virens are commonly referred to as pollock. Other names for P...
, also referred to as coalfish, a close relative of codfish. Sei whales appeared off the coast of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
at the same time as the pollock, both coming to feed on the abundant plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. 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.
Taxonomy
The sei was classified as Balaena rostraia, Balaena borealis, Bataenoptera laticeps, and Eulama physalus, among others, before Lesson's alternative Balaenoptera borealis was formalized.Sei whales are rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
s (family Balaenopteridae), baleens that includes the humpback whale
Humpback Whale
The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the...
, the blue whale
Blue Whale
The blue whale is a marine mammal belonging to the suborder of baleen whales . At in length and or more in weight, it is the largest known animal to have ever existed....
, the Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, the fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
, and the minke whale
Minke Whale
Minke whale , or lesser rorqual, is a name given to two species of marine mammal belonging to a clade within the suborder of baleen whales. The minke whale was given its official designation by Lacepède in 1804, who described a dwarf form of Balænoptera acuto-rostrata...
. Rorquals take their name from the Norwegian
Norwegian language
Norwegian is a North Germanic language spoken primarily in Norway, where it is the official language. Together with Swedish and Danish, Norwegian forms a continuum of more or less mutually intelligible local and regional variants .These Scandinavian languages together with the Faroese language...
word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves below the mouth that continue along the body's underside. Balaenopteridae diverged from the other families of suborder Mysticeti
Baleen whale
The Baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
, also called the whalebone whales or great whales, as long ago as the middle Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
.
However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii).
Their ranges do not overlap.
Description
The sei whale is the third-largest Balaenopteridae, after the blue whale (up to 180 tonnes, 200 tons) and the fin whale (up to 70 tonnes, 77 tons). Mature adults typically measure between 12–15 m (39.4–49.2 ft) and weigh 20–30 t (19.7–29.5 ). The southern sei whale is larger than the northern. Females are considerably larger than males. The largest known sei whale measured 20 metres (65.6 ft), and weighed between 40–45 t (39.4–44.3 ). The largest specimens taken off IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
were slightly longer than 16 metres (52.5 ft).
At birth, a calf typically measures 4–5 m (13.1–16.4 ft) in length.
Anatomy
The whale's body is typically a dark steel grey with irregular light grey to white markings on the ventral surface, or towards the front of the lower body. The whale has a series of 32–60 pleatPleat
A pleat is a type of fold formed by doubling fabric back upon itself and securing it in place. It is commonly used in clothing and upholstery to gather a wide piece of fabric to a narrower circumference....
s or grooves along the bottom of the body that allow the throat area to expand greatly during feeding. The rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
is pointed and the pectoral fins are relatively short, only 9%–10% of body length, and pointed at the tips. It has a single ridge extending from the tip of the rostrum to the paired blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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 ectoparasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s (Penella spp.),
lamprey
Lamprey
Lampreys are a family of jawless fish, whose adults are characterized by a toothed, funnel-like sucking mouth. Translated from an admixture of Latin and Greek, lamprey means stone lickers...
s (family Petromyzontidae),
or possibly "cookie-cutter" sharks
Cookiecutter shark
The cookiecutter shark , also called the cigar shark, is a species of small dogfish shark in the family Dalatiidae. This shark occurs in warm, oceanic waters worldwide, particularly near islands, and has been recorded from as deep as . It migrates vertically up to every day, approaching the...
(Isistius brasiliensis).
It has a tall, sickle
Sickle
A sickle is a hand-held agricultural tool with a variously curved blade typically used for harvesting grain crops or cutting succulent forage chiefly for feeding livestock . Sickles have also been used as weapons, either in their original form or in various derivations.The diversity of sickles that...
-shaped dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
that ranges in height from 25–61 cm (9.8–24 in), about two-thirds of the way back from the tip of the rostrum. Dorsal fin shape, pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
ation pattern, and scarring have been used to a limited extent in photo-identification
Wildlife photo-identification
Photo-identification is a technique used into identify and track individuals of a wild animal study population over time. It relies on capturing photographs of distinctive characteristics such as skin patterns and scars from the animal...
studies.
The tail is thick and the fluke, or lobe, is relatively small in relation to the size of the whale's body.
Nail (anatomy)
A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals....
-like keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
that frays out into whitish fine hairs on the ends inside the mouth near the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
. The sei's very fine baleen bristles, about 0.1 millimetre (0.00393700787401575 in) are the most reliable characteristic that distinguishes it from other baleen whales.
The sei whale looks similar to other large baleen whales. The best way to distinguish between it and Bryde's whale
Bryde's Whale
Bryde's whales are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as...
, apart from differences in baleen plates, is by the presence of lateral ridges on the dorsal surface of the Bryde's whale's rostrum. Large individuals can be confused with fin whale
Fin Whale
The fin whale , also called the finback whale, razorback, or common rorqual, is a marine mammal belonging to the suborder of baleen whales. It is the second longest whale and the sixth largest living animal after the blue whale, bowhead whale, and right whales, growing to nearly 27 metres long...
s, unless the fin whale's asymmetrical head coloration is clearly seen. The fin whale's lower jaw's right side is white, and the left side is grey. When viewed from the side, the upper edge of the sei's head has a small arch between the tip of the rostrum and eye, while the fin whale's profile is relatively flat.
Life history
Sei whales usually travel aloneor in groups of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure
Social structure
Social structure is a term used in the social sciences to refer to patterned social arrangements in society that are both emergent from and determinant of the actions of the individuals. The usage of the term "social structure" has changed over time and may reflect the various levels of analysis...
. Males and females may bond, but this is uncertain.
The sei whale is among the fastest cetacea
Cetacea
The order Cetacea includes the marine mammals commonly known as whales, dolphins, and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal", was more general. It comes from Ancient Greek , meaning "whale" or "any huge fish or sea...
ns. It can reach speeds of up to 50 kilometres per hour (25.5 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 40–60 seconds. Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives. The blowholes
Blowhole (biology)
In biology, a blowhole is the hole at the top of a cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but mucus and...
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.
Feeding
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
, using its baleen plate
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
s to obtain its food by opening its mouth, engulfing large amounts of the water containing the food, then straining the water out through the baleen
Baleen
Baleen or whalebone is a filter-feeder system inside the mouths of baleen whales. The baleen system works when a whale opens its mouth underwater and then water pours into the whale's mouth. The whale then pushes the water out, and animals such as krill are filtered by the baleen and remain as food...
, trapping any food items inside its mouth.
The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
to obtain its average of about 900 kilograms (1,984.2 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
, including zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
and small fish. The whale's diet preferences has been determined from stomach analyses, direct observation of feeding behavior.,
and analyzing fecal matter
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
collected near them, which appears as a dilute brown cloud. The feces are collected in nets and DNA is separated, individually identified, and matched with known species.
The whale competes for food against clupeid
Clupeidae
Clupeidae is the family of the herrings, shads, sardines, hilsa and menhadens. It includes many of the most important food fishes in the world.-Description and biology:...
fish (herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
and its relatives), basking shark
Basking shark
The basking shark is the second largest living fish, after the whale shark. It is a cosmopolitan migratory species, found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder and has anatomical adaptations to filter feeding, such as a greatly enlarged...
s, and right whale
Right whale
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund....
s.
In the North Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, it feeds primarily on calanoid copepods
Calanoida
Calanoida is an order of copepods, a kind of zooplankton. They include around 40 families with about 1800 species of both marine and freshwater copepods. Calanoid copepods are dominant in the plankton in many parts of the world's oceans, making up 55%–95% of plankton samples...
, specifically Calanus finmarchicus, with a secondary preference for euphausiids
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, in particular Meganyctiphanes norvegica and Thysanoessa inermis.
In the North Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, it feeds on similar zooplankton, including the copepod species Neocalanus cristatus, Neocalanus plumchrus, and Calanus pacificus, and euphausid species Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, and Thysanoessa spinifera. In addition, it eats larger organisms, such as the Japanese flying squid
Japanese Flying Squid
The Japanese Flying Squid or Japanese Common Squid, Todarodes pacificus, is a squid of the family Ommastrephidae. This animal lives in the northern Pacific Ocean, in the area surrounding Japan, up the full coast of China up to Russia, then spreading across the Bering Straight over towards the lower...
, Todarodes pacificus pacificus,
and small fish, including members of the Engraulis
Engraulis
Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis albidus Borsa, Collet & J. D. Durand, 2004* Engraulis anchoita Carl Hubbs & Marini, 1935 * Engraulis australis Engraulis is a genus of anchovies. It currently contains nine species.-Species:* Engraulis...
(anchovies), Cololabis
Cololabis
Cololabis is a genus of sauries. The name is derived from the Greek word kolos, meaning "short", and the Latin word labia, meaning "lips". There are two species....
(sauries), Sardinops
South American pilchard
The South American pilchard, Sardinops sagax, is a sardine of the Family Clupeidae, the only member of the genus Sardinops, found in the indo-Pacific oceans. Their length is up to 40 cm...
(pilchards), and Trachurus
Trachurus
Jack mackerels are marine fishes in the Trachurus genus of the Carangidae family. The type species of the genus is the Atlantic horse mackerel, Trachurus trachurus. The name of the genus is derived from the Greek word trachys, meaning "rough", and the Greek word oura, meaning "tail"...
(jack mackerels) genera.
Some of these fish are commercially important. Off central California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, the whale may feed on anchovies
Anchovy
Anchovies are a family of small, common salt-water forage fish. There are 144 species in 17 genera, found in the Atlantic, Indian, and Pacific Oceans. Anchovies are usually classified as an oily fish.-Description:...
between June and August, and on krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
(Euphausia pacifica) during September and October. In the Southern Hemisphere, prey species include the copepods Neocalanus tonsus, Calanus simillimus, and Drepanopus pectinatus, as well as the euphausids Euphausia superba and Euphausia vallentini. Sei whales also eat sardines.
Reproduction
MatingMating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
occurs in temperate, subtropical seas during the winter. Gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
is estimated to vary around 10 months,
11 months,
or one year,
depending which model of foetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
growth is used. The different estimates result from scientists' inability to observe an entire pregnancy; most reproductive data for baleen whales were obtained from animals caught by commercial whalers, which offers only a single snapshot of fetal growth. Researchers attempt to extrapolate conception dates by comparing fetus size and characteristics with newborns.
A newborn is wean
Weaning
Weaning is the process of gradually introducing a mammal infant, either human or animal, to what will be its adult diet and withdrawing the supply of its mother's milk.The process takes place only in mammals, as only mammals produce milk...
ed from its mother at 6–9 months of age, when it is 11–12 m (36.1–39.4 ft) long, so weaning takes place at the summer or autumn feeding grounds. Females reproduce every 2–3 years, with as many as six fetuses reported, but single births are far more common. The average age of sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
of both sex
Sex
In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...
es is 8–10 years, at a length of around 12 metres (39.4 ft) for males and 13 metres (42.7 ft) for females. The whales can reach ages of up to 65 years.
Vocalizations
The sei whale makes long, loud, low-frequency sounds. Relatively little is known about specific calls, but in 2003, observers noted sei whale calls in addition to sounds that could be described as "growls" or "whooshes" off the coast of the Antarctic PeninsulaAntarctic Peninsula
The Antarctic Peninsula is the northernmost part of the mainland of Antarctica. It extends from a line between Cape Adams and a point on the mainland south of Eklund Islands....
.
Many calls consisted of multiple parts at different frequencies. This combination distinguishes the their calls from those of other whales. Most calls lasted about a half second, and occurred in the 240–625 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
range, well within the range of human hearing. The maximum volume of the vocal sequences is reported as 156 decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
s relative to 1 micropascal (μPa)
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
at a reference distance of one meter. An observer situated one meter from a vocalizing whale would perceive a volume roughly equivalent to the volume of a jackhammer operating two meters away.
Range and migration
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
or tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
waters. The difficulty of distinguishing them at sea from their close relatives, Bryde's whales and in some cases from fin whales, creates confusion about their range and population, especially in warmer waters where Bryde's whales are most common.
In the North Atlantic, its range extends from southern Europe
Southern Europe
The term Southern Europe, at its most general definition, is used to mean "all countries in the south of Europe". However, the concept, at different times, has had different meanings, providing additional political, linguistic and cultural context to the definition in addition to the typical...
or northwestern Africa to Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, and from the southern United States
Southern United States
The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...
to Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
. The southernmost confirmed records are strandings along the northern Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
and in the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
. Throughout its range, the whale tends to avoid semi-enclosed bodies of water, such as the Gulf of Mexico, the Gulf of Saint Lawrence
Gulf of Saint Lawrence
The Gulf of Saint Lawrence , the world's largest estuary, is the outlet of North America's Great Lakes via the Saint Lawrence River into the Atlantic Ocean...
, Hudson Bay
Hudson Bay
Hudson Bay , sometimes called Hudson's Bay, is a large body of saltwater in northeastern Canada. It drains a very large area, about , that includes parts of Ontario, Quebec, Saskatchewan, Alberta, most of Manitoba, southeastern Nunavut, as well as parts of North Dakota, South Dakota, Minnesota,...
, the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
, and the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It occurs predominantly in deep water, occurring most commonly over the continental slope
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
,
in basins situated between banks,
or submarine canyon
Submarine canyon
A submarine canyon is a steep-sided valley on the sea floor of the continental slope. Many submarine canyons are found as extensions to large rivers; however there are some that have no such association. Canyons cutting the continental slopes have been found at depths greater than 2 km below sea...
areas.
In the North Pacific, it ranges from 20°N
20th parallel north
The 20th parallel north is a circle of latitude that is 20 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean....
–23°N
23rd parallel north
The 23rd parallel north is a circle of latitude that is 23 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean....
latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
in the winter, and from 35°N
35th parallel north
The 35th parallel north is a circle of latitude that is 35 degrees north of the Earth's equatorial plane. It crosses Africa, the Mediterranean Sea, Asia, the Pacific Ocean, North America and the Atlantic Ocean....
–50°N
50th parallel north
The 50th parallel north is a circle of latitude that is 50 degrees north of the Earth's equatorial plane. It crosses Europe, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
latitude in the summer.
Approximately 75% of the North Pacific population lives east of the International Date Line
International Date Line
The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...
, but there is little information regarding the North Pacific distribution. Two whales tagged in deep waters off California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
were later recaptured off Washington and British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, revealing a possible link between these areas,
but the lack of other tag recovery data makes these two cases inconclusive. In the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
, summer distribution based upon historic catch data is between 40 and 50°S latitude, while winter distribution is unknown.
Migration
In general, the sei whale migrates annually from cool and subpolar waters in summer to temperate and subtropical waters for winter, where food is more abundant. In the northwest Atlantic, sightings and catch records suggest the whales move north along the shelf edge to arrive in the areas of Georges BankGeorges Bank
Georges Bank is a large elevated area of the sea floor which separates the Gulf of Maine from the Atlantic Ocean and is situated between Cape Cod, Massachusetts and Cape Sable Island, Nova Scotia ....
, Northeast Channel
Gulf of Maine
The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America.It is delineated by Cape Cod at the eastern tip of Massachusetts in the southwest and Cape Sable at the southern tip of Nova Scotia in the northeast. It includes the entire coastlines of the U.S...
, and Browns Bank
Gulf of Maine
The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America.It is delineated by Cape Cod at the eastern tip of Massachusetts in the southwest and Cape Sable at the southern tip of Nova Scotia in the northeast. It includes the entire coastlines of the U.S...
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 Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
n shelf from mid-September to mid-November. Whales in the Labrador Sea
Labrador Sea
The Labrador Sea is an arm of the North Atlantic Ocean between the Labrador Peninsula and Greenland. The sea is flanked by continental shelves to the southwest, northwest, and northeast. It connects to the north with Baffin Bay through the Davis Strait...
as early as the first week of June may move farther northward to waters southwest of Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
later in the summer.
In the northeast Atlantic, the sei whale winters as far south as West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
, and follows the continental slope northward in spring. Large females lead the northward migration and reach the Denmark Strait
Denmark Strait
The Denmark Strait or Greenland Strait |Sound]]) is an oceanic strait between Greenland and Iceland...
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.
Despite knowing some general migration patterns, exact routes are not known and scientists cannot readily predict exactly where groups will appear from one year to the next.
F.O. Kapel noted a correlation between appearances west of Greenland and the incursion of relatively warm waters from the Irminger Current
North Atlantic Current
The North Atlantic Current is a powerful warm ocean current that continues the Gulf Stream northeast. West of Ireland it splits in two; one branch, the Canary Current, goes south, while the other continues north along the coast of northwestern Europe...
into that area.
Some evidence from tagging data indicates individuals return off the coast of Iceland
Iceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
on an annual basis.
Whaling
Harpoon
A harpoon is a long spear-like instrument used in fishing to catch fish or large marine mammals such as whales. It accomplishes this task by impaling the target animal, allowing the fishermen to use a rope or chain attached to the butt of the projectile to catch the animal...
s and steam-powered whaling ships in the late nineteenth century brought previously unobtainable large whales within reach of commercial whalers
Whaling
Whaling is the hunting of whales mainly for meat and oil. Its earliest forms date to at least 3000 BC. Various coastal communities have long histories of sustenance whaling and harvesting beached whales...
. Initially their speed and elusiveness,
and later the comparatively small yield of oil
Whale oil
Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...
and meat partially protected them. Once stocks of more profitable right whale
Right whale
Right whales are three species of large baleen whales consisting of two genera in the family Balaenidae of order Cetacea. Their bodies are very dark gray or black and rotund....
s, blue whales, fin whales, and humpback whales became depleted, sei whales were hunted in earnest, particularly from 1950 to 1980.
North Atlantic
In the North Atlantic between 1885 and 1984, 14,295 sei whales were taken. They were hunted in large numbers off the coast of NorwayNorway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
and Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
beginning in the late nineteenth and early twentieth centuries, and in 1885 alone, more than 700 were caught off Finnmark, Norway
Finnmark
or Finnmárku is a county in the extreme northeast of Norway. By land it borders Troms county to the west, Finland to the south and Russia to the east, and by water, the Norwegian Sea to the northwest, and the Barents Sea to the north and northeast.The county was formerly known as Finmarkens...
.
Their meat was a popular Norwegian food. The meat's value made the hunting of this difficult-to-catch species profitable in the early twentieth century.
In Iceland, a total of 2,574 whales were taken from the Hvalfjörður
Hvalfjörður
Hvalfjörður is situated in the west of Iceland between Mosfellsbær and Akranes. The fjord is approximately 30 km long and 5 km wide....
whaling station between 1948 and 1985. Since the late 1960s to early 1970s, the sei whale has been second only to the fin whale as the preferred target of Icelandic whalers, with meat in greater demand than whale oil
Whale oil
Whale oil is the oil obtained from the blubber of various species of whales, particularly the three species of right whale and the bowhead whale prior to the modern era, as well as several other species of baleen whale...
, the prior target.
Small numbers were taken off the Iberian Peninsula
Iberian Peninsula
The Iberian Peninsula , sometimes called Iberia, is located in the extreme southwest of Europe and includes the modern-day sovereign states of Spain, Portugal and Andorra, as well as the British Overseas Territory of Gibraltar...
, beginning in the 1920s by Spanish whalers,
off the Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
n shelf in the late 1960s and early 1970s by Canadian whalers, and off the coast of West Greenland from the 1920s to the 1950s by Norwegian and Danish whalers.
North Pacific
In the North Pacific, the total reported catch by commercial whalers was 72,215 between 1910 and 1975; the majority were taken after 1947.Shore stations in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
, processed 300–600 each year between 1911 and 1955. In 1959, the Japanese catch peaked at 1,340. Heavy exploitation in the North Pacific began in the early 1960s, with catches averaging 3,643 per year from 1963 to 1974 (total 43,719; annual range 1,280–6,053).
In 1971, after a decade of high catches, it became scarce in Japanese waters, ending commercial whaling in 1975.
Off the coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, sei whales were hunted off British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
from the late 1950s to the mid 1960s, when the number of whales captured dropped to around 14 per year. More than 2,000 were caught in British Columbia waters between 1962 and 1967.
Between 1957 and 1971, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
shore stations processed 386 whales. Commercial Sei whaling ended in the eastern North Pacific in 1971.
Southern Hemisphere
A total of 152,233 were taken in the Southern HemisphereSouthern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
between 1910 and 1979. Whaling in southern oceans
Southern Ocean
The Southern Ocean comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica. It is usually regarded as the fourth-largest of the five principal oceanic divisions...
originally targeted humpback whales. By 1913, this 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. The catch peaked in 1964-65 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.
Post-protection whaling
Since the moratorium on commercial whaling, some sei whales have been taken by IcelandIceland
Iceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population...
ic and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese whalers under the IWC's scientific research programme. Iceland carried out four years of scientific whaling between 1986 and 1989, killing up to 40 sei whales a year.
Japanese scientists catch about 50 sei whales each year for this purpose. The research is conducted by the Institute of Cetacean Research
Institute of Cetacean Research
The is a Japanese government-sponsored institution. It took over from the Whale Research Institute , which grew out of the Nakabe Scientific Research Centre ....
(ICR) in Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, a privately-funded, nonprofit institution. The main focus of the research is to examine what they eat and to assess the competition between whales and fisheries. Dr. Seiji Ohsumi, Director General of the ICR, 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."
He later added,
- "...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."
Conservation groups, such as the World Wildlife Fund
World Wide Fund for Nature
The World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...
, dispute the value of this research, claiming that sei whales feed primarily on squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
and plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
which are not hunted by humans, and only rarely on fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
. They say that the program is
- "nothing more than a plan designed to keep the whaling fleet in business, and the need to use whales as the scapegoat for overfishing by humans."
At the 2001 meeting of the IWC Scientific Committee, 32 scientists submitted a document expressing their belief that the Japanese program lacked scientific rigour and would not meet minimum standards of academic review
Peer review
Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...
.
In 2010, a Los Angeles restaurant confirmed to be serving sei whale meat
Whale meat
Whale meat is the flesh of whales used for consumption by humans or other animals. It is prepared in various ways, and is historically part of the diet and cuisine of various communities that live near an ocean, including those of Japan, Norway, Iceland, and the Arctic...
was closed by its owners after prosecution by authorities for handling a protected species.
Conservation status
International Whaling Commission
The International Whaling Commission is an international body set up by the terms of the International Convention for the Regulation of Whaling , which was signed in Washington, D.C...
(IWC) first set catch quotas for the North Pacific for individual species. Before quotas, there were no legal limits.
Complete protection from commercial whaling in the North Pacific came in 1976.
Quotas on sei whales in the North Atlantic began in 1977. Southern Hemisphere stocks were protected in 1979. Facing mounting evidence that several whale species were threatened with extinction, the IWC established a complete moratorium on commercial whaling beginning in 1986.
In the late 1970s, some "pirate" whaling took place in the eastern North Atlantic.
There is no direct evidence of illegal whaling in the North Pacific, although the acknowledged misreporting of whaling data by the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
means that catch data are not entirely reliable.
The species remained listed on the IUCN Red List of Threatened Species
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
in 2000, categorized as "endangered". Northern Hemisphere populations are listed as CITES Appendix II, indicating they are not immediately threatened with extinction, but may become so if they are not listed. Populations in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
are listed as CITES Appendix I, indicating they are threatened with extinction if trade is not halted.
The Sei whale is listed on both Appendix I"Appendix I and Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009. and Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS
Bonn Convention
The Convention on the Conservation of Migratory Species of Wild Animals aims to conserve terrestrial, marine and avian migratory species throughout their range...
). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them and also on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
Sei whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU)and the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas(ACCOBAMS
ACCOBAMS
ACCOBAMS, the Agreement on the Conservation of Cetaceans in the Black Sea,Mediterranean Sea and contiguous Atlantic area is ‘a cooperative tool for the conservation of marine biodiversity in the Mediterranean and Black Seas’....
)
The species is listed as endangered by the U.S. government National Marine Fisheries Service
National Marine Fisheries Service
The National Marine Fisheries Service is a United States federal agency. A division of the National Oceanic and Atmospheric Administration and the Department of Commerce, NMFS is responsible for the stewardship and management of the nation's living marine resources and their habitat within the...
under the U.S. Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
.
Population estimates
The current population is estimated at 80,000, nearly a third of the pre-whaling population. A 1991 study in the North Atlantic estimated only 4,000.Sei whales were said to have been scarce in the 1960s and early 1970s off northern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
.
One possible explanation for this disappearance is that the whales were overexploited
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
. The drastic reduction in northeastern Atlantic copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
stocks during the late 1960s may be another culprit.
Surveys in the Denmark Strait
Denmark Strait
The Denmark Strait or Greenland Strait |Sound]]) is an oceanic strait between Greenland and Iceland...
found 1,290 whales in 1987, and 1,590 whales in 1989. Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
's population estimates are between 1,393 and 2,248, with a minimum of 870.
A 1977 study estimated Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
totals of 9,110, based upon catch and CPUE
Catch per unit effort
In fisheries and conservation biology, the catch per unit effort is an indirect measure of the abundance of a target species. Changes in the catch per unit effort are inferred to signify changes to the target species' true abundance...
data. Japanese interests claim this figure is outdated, and in 2002 claimed the western North Pacific population was over 28,000, a figure not accepted by the scientific community. In California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
waters, there was only one confirmed and five possible sightings by 1991 to 1993 aerial and ship surveys,
and there were no confirmed sightings off Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
and Washington. Prior to commercial whaling, the North Pacific hosted an estimated 42,000. By the end of whaling, the population was down to between 7,260 and 12,620.
In the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
, population estimates range between 9,800 and 12,000, based upon catch history and CPUE. The IWC estimated 9,718 whales based upon survey data between 1978 and 1988.
Prior to commercial whaling, there were an estimated 65,000.
External links
- US National Marine Fisheries Service Sei Whale web page
- ARKive – images and movies of the sei whale (Balaenoptera borealis)
- IUCN Redlist entry
- World Wide Fund for Nature (WWF) - species profile for the Sei Whale
- Official website of the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area
- Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region