Balaenoptera omurai
Encyclopedia
Omura's whale is a species
of rorqual
about which very little is known.
The scientific description of this whale was made in the November 20, 2003, edition of Nature
(426, 278–281) by three Japanese scientists, Shiro Wada, Masayuki Oishi and Tadasu K. Yamada. The three scientists determined the existence of the species by analysing the morphology and mitochondrial DNA
of nine individuals—eight caught by a Japanese research vessel in the late 1970s in the Indo-Pacific and a further specimen collected in 1998 from a small island in the Sea of Japan
. Later abundant genetic evidence confirmed Omura's whale as a valid species and revealed it to be an early offshoot from the rorqual lineage, diverging much earlier than the Bryde's
and sei whale
s. It is perhaps more closely related to its larger cousin, the blue whale
.
The common name and specific epithet commemorates Japanese cetologist Hideo Omura.
In the third edition of Mammal Species of the World
, the "species" is relegated to being a synonym of Balaenoptera edeni. However the authors note that this subject to a revision of the genus. The database ITIS
lists this as a valid taxon, noting a caveat on the disputed systematics of this species, Balaenoptera edeni and Balaenoptera brydei
.
are smaller). Of the six specimens taken during Japanese whaling off the Solomon Islands
in 1976, the largest adult female was 11.5 metres (37.7 ft) and the largest adult male 9.6 metres (31.5 ft). Based on earplug laminations, the former was estimated to be 29-years-old and the latter 38-years-old. Its appearance resembles the larger fin whale
, both having the asymmetrical white, right lower jaw, as well as streaks radiating out from the eye region. Its dorsal fin is similar to Bryde's whale, being very falcate and rising at a steep angle; but it is more rounded than the latter species, which usually has a much more pointed fin. Unlike Bryde's, however, they appear to only have one prominent ridge on the rostrum (Bryde's usually have three). It has 80–90 ventral pleats, which extend past the navel. Its 180–210 pairs of baleen plates are short and broad, usually being yellowish-white to black (at times two-tone).
), Indonesia
, the Philippines
, the Sea of Japan, and the Solomon Sea
.
. Two individuals were also recently incidentally caught in set nets in Japan.
In addition, the Omura's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).
. In October 2010, sightseers encountered and photographed up to 15 individuals, seeing groups of three or four animals together, as well as at least two cow-calf pairs.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of 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...
about which very little is known.
The scientific description of this whale was made in the November 20, 2003, edition of Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
(426, 278–281) by three Japanese scientists, Shiro Wada, Masayuki Oishi and Tadasu K. Yamada. The three scientists determined the existence of the species by analysing the morphology and mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...
of nine individuals—eight caught by a Japanese research vessel in the late 1970s in the Indo-Pacific and a further specimen collected in 1998 from a small island in the Sea of Japan
Sea of Japan
The Sea of Japan is a marginal sea of the western Pacific Ocean, between the Asian mainland, the Japanese archipelago and Sakhalin. It is bordered by Japan, North Korea, Russia and South Korea. Like the Mediterranean Sea, it has almost no tides due to its nearly complete enclosure from the Pacific...
. Later abundant genetic evidence confirmed Omura's whale as a valid species and revealed it to be an early offshoot from the rorqual lineage, diverging much earlier than the Bryde's
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...
and sei whale
Sei Whale
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...
s. It is perhaps more closely related to its larger cousin, 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 common name and specific epithet commemorates Japanese cetologist Hideo Omura.
In the third edition of Mammal Species of the World
Mammal Species of the World
Mammal Species of the World, now in its 3rd edition, is a standard reference work in zoology giving descriptions and bibliographic data for the known species of mammals.An updated Third Edition of Mammal Species of the World was published late in 2005:...
, the "species" is relegated to being a synonym of Balaenoptera edeni. However the authors note that this subject to a revision of the genus. The database ITIS
Itis
Itis may refer to* Integrated Taxonomic Information System, a partnership designed to provide consistent and reliable information on the taxonomy of biological species...
lists this as a valid taxon, noting a caveat on the disputed systematics of this species, Balaenoptera edeni and Balaenoptera brydei
Balaenoptera brydei
Balaenoptera brydei is a species of cetacean, marine mammals, in a complex group known as the Bryde’s Whales. They are the least-known and in many ways the most unusual of the rorquals...
.
Description
Omura's whale is among the smallest of the rorquals (only the two species of Minke whaleMinke 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...
are smaller). Of the six specimens taken during Japanese whaling off the Solomon Islands
Solomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...
in 1976, the largest adult female was 11.5 metres (37.7 ft) and the largest adult male 9.6 metres (31.5 ft). Based on earplug laminations, the former was estimated to be 29-years-old and the latter 38-years-old. Its appearance resembles the larger 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...
, both having the asymmetrical white, right lower jaw, as well as streaks radiating out from the eye region. Its dorsal fin is similar to Bryde's whale, being very falcate and rising at a steep angle; but it is more rounded than the latter species, which usually has a much more pointed fin. Unlike Bryde's, however, they appear to only have one prominent ridge on the rostrum (Bryde's usually have three). It has 80–90 ventral pleats, which extend past the navel. Its 180–210 pairs of baleen plates are short and broad, usually being yellowish-white to black (at times two-tone).
Range
Omura's whale appears to be restricted to the shelf and nearshore areas of tropical and subtropical waters, with records mostly from the eastern Indian Ocean (off Cocos IslandsCocos (Keeling) Islands
The Territory of the Cocos Islands, also called Cocos Islands and Keeling Islands, is a territory of Australia, located in the Indian Ocean, southwest of Christmas Island and approximately midway between Australia and Sri Lanka....
), Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
, the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
, the Sea of Japan, and the Solomon Sea
Solomon Sea
The Solomon Sea is a sea located within the Pacific Ocean. It lies between Papua New Guinea and the Solomon Islands. Many major battles were fought there during World War II.-Extent:...
.
Hunting and other mortality
Eight Omura’s whales were taken by Japanese scientific whaling in the 1970s, six in the Solomon Sea in October 1976 and two near the Cocos Islands in November 1978. In the past, artisanal whalers in the Philippines took a sporadic number in the Bohol SeaBohol Sea
The Bohol Sea, also called the Mindanao Sea, is located between Visayas and Mindanao in the Philippines. It lies south of Bohol and Leyte and north of Mindanao...
. Two individuals were also recently incidentally caught in set nets in Japan.
Conservation
The Omura's whale is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.In addition, the Omura's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).
Possible sightings
The species may have been sighted off the northwest coast of Australia on two (possibly three) separate occasions in 2009 and 2010. On November 2, 2009 a birder sighted three individuals; the same day another sighting was made north of the Lacepede IslandsLacepede Islands
The Lacepede Islands, sometimes referred to simply as the Lacepedes, are a group of four islands lying off the north-west coast of Western Australia, about 120 km north of Broome. They are about 30 km from the Dampier Peninsula, from which they are separated by the Lacepede Channel...
. In October 2010, sightseers encountered and photographed up to 15 individuals, seeing groups of three or four animals together, as well as at least two cow-calf pairs.
External links
- http://www.pacificcetaceans.org/ Official webpage of the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region