The East Asian finless porpoise (''Neophocaena sunameri'') is a species of
porpoise native to the
East China Sea,
Yellow Sea
The Yellow Sea is a marginal sea of the Western Pacific Ocean located between mainland China and the Korean Peninsula, and can be considered the northwestern part of the East China Sea. It is one of four seas named after common colour ter ...
, and the seas around
Japan. The
Yangtze finless porpoise
The Yangtze finless porpoise (''Neophocaena asiaeorientalis'') is a species of toothed whale in the family Phocoenidae. It is endemic to the Yangtze River in China, making it the country's only known freshwater cetacean following the possible ...
(''N. asiaeorientalis'') was formerly considered a subspecies, but is now thought to be a distinct species.
Name
The Korean communities of the porpoise are sometimes known as sanggwaengi ( ko, 상괭이) and the
Japanese
Japanese may refer to:
* Something from or related to Japan, an island country in East Asia
* Japanese language, spoken mainly in Japan
* Japanese people, the ethnic group that identifies with Japan through ancestry or culture
** Japanese diaspor ...
communities, particularly the subspecies ''N. p. sunameri'', as sunameri ( ja, 砂滑)().
Distribution
![Neophocaena phocaenoides DSC 03](https://upload.wikimedia.org/wikipedia/commons/c/ca/Neophocaena_phocaenoides_DSC_03.jpg)
The species inhabits the coastal areas off mainland China (e.g.,
Chongming Island
Chongming, formerly known as Chungming, is an alluvial island at the mouth of the Yangtze River in eastern China covering as of 2010. Together with the islands Changxing and Hengsha, it forms Chongming District, the northernmost area of the ...
) south to the
Penghu Islands
The Penghu (, Hokkien POJ: ''Phîⁿ-ô͘'' or ''Phêⁿ-ô͘'' ) or Pescadores Islands are an archipelago of 90 islands and islets in the Taiwan Strait, located approximately west from the main island of Taiwan, covering an are ...
. The
Matsu Islands
The Matsu Islands ( or , ; Foochow Romanized: Mā-cū liĕk-dō̤), officially Lienchiang County (, ; Foochow Romanized: Lièng-gŏng-gâing), are an archipelago of 36 islands and islets in the East China Sea governed by the Republic of China ( ...
are thought to be their northern limit, and the local population in this area is physically smaller than the
Indo-Pacific finless porpoise. These two species overlap in the Matsu region. The population in coastal waters around Japan is geographically isolated by the deep waters between Japan and continental Asia. Vagrant animals can reach the
Ryukyu Islands
The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yona ...
.
Habitat
Throughout their range, the porpoises stay in shallow waters, up to deep, close to the shore, in waters with soft or sandy seabeds, or in estuaries and mangrove swamps. In exceptional cases, they have been encountered as far as off-shore in the
East China
East China () is a geographical and a loosely defined cultural region that covers the eastern coastal area of China.
A concept abolished in 1978, for economical purposes the region was defined from 1949 to 1961 by the Chinese Central Govern ...
and
Yellow
Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the ...
Seas, albeit still in shallow water.
Description
Finless porpoises can grow to as much as in length, and can weigh up to , although most are smaller. Adults grow more than 1.55 m (5 ft) in length and up to 30–45 kg (65–100 lb) in weight.
The flippers are moderately large, reaching up to 20% of the total body length. Adults are typically a uniform, light grey colour, although some may have lighter patches of skin around the mouth, or darker patches in front of the flippers. Newborn calves of the central and eastern subspecies are mostly black with grey around the dorsal ridge area, becoming fully grey after four to six months. However, newborn calves of the western subspecies are a light creamy grey, and become darker as they age.
Anatomy
The anatomy of finless porpoises has been relatively well studied, compared with that of some other cetacean species. The tubercles along the dorsal ridge are known to contain numerous nerve endings is used as a sensory function. The auditory system also appears well-developed, with numerous nerve fibres specialised for rapid communication between the ears and the brain. Sight is relatively poor, however, due to the overall cloudiness of the Yangtze River; they have a reduced lens and a limited number of fibres in the optic nerve and to the muscles moving the eyes compared to the
Indo-Pacific finless porpoise. It is speculated that their vision is somewhat better than that of the
Yangtze river dolphin
The baiji (; IPA: ; ''Lipotes vexillifer'', ''Lipotes'' meaning "left behind" and ''vexillifer'' "flag bearer") is a possibly extinct species of freshwater dolphin native to the Yangtze river system in China. It is thought to be the first dolph ...
.
[
The skeleton is light, accounting for only 5% of the total weight of the animal. There are between 58 and 65 vertebrae, about half of them in the tail, and with the first three cervical vertebrae fused into a single structure. This reduces flexibility of the neck while increasing stability in the water. There are ten to fourteen pairs of ribs in the chest, and an additional set of vestigial ribs has sometimes been reported in the neck, in association with the seventh cervical vertebra.][ There are 44 sets of spinal nerves. Like all porpoises, they have spade-shaped teethed designed for catching small fish and shrimp.] Their skeletal design allows them to leap from the water and perform " tail stands".[
The nasal passage contains nine or ten air sacs, which are capable of sealing off all air within the passage. Behind these are an additional set of ]vomeronasal
The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth (the hard palate) in various tetrapods. T ...
sacs. The trachea
The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from the ...
, however, is short, with only four cartilaginous rings.[ The stomach has three chambers, with no ]caecum
The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body (the same side of the body as the appendix, to which it is joined). The wo ...
, and no distinct difference between the small and large intestine
The large intestine, also known as the large bowel, is the last part of the gastrointestinal tract and of the digestive system in tetrapods. Water is absorbed here and the remaining waste material is stored in the rectum as feces before bein ...
s.
Sexual maturity is thought to occur around six years, with only one calf born at a time. Gestation is approximately one year, and lactation lasts for over six months.[
]
Behavior
In Chinese coastal waters, finless porpoises are generally found in groups of three to six, although aggregations of up to about fifty have been reported. In Japanese waters, groups appear to be smaller, with pairs being typical, and even rare aggregations being no larger than thirteen individuals.
Diet
They are reported to eat fish
Fish are aquatic, craniate, gill-bearing 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. Approximately 95% of ...
, shrimp and squid in the Yellow Sea
The Yellow Sea is a marginal sea of the Western Pacific Ocean located between mainland China and the Korean Peninsula, and can be considered the northwestern part of the East China Sea. It is one of four seas named after common colour ter ...
/Bohai area. In Japanese waters, they are known to eat fish, shrimp, squid, cuttlefish and octopuses
An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...
.
Conservation
The primary danger to the species is environmental degradation. Except for being briefly hunted after World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
due to the lack of seaworthy fishing boats, finless porpoises have never been widely hunted in Japan. It is a species protected since 1930 at the area around Awajima Island, Takehara
is a city located in Hiroshima Prefecture, Japan. The city was founded on November 3, 1958.
As of 2016, the city has an estimated population of 26,035 and a population density of 220 persons per km2. The total area is 118.30 km2.
Ōkun ...
and this coverage had since been extended to all Japanese coastal waters. A decline of over 50% over the last three generations has been noted in the species, and it is thus classified as Endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...
. This decline is largely thought to be a consequence of intensified fishing activity, which has caused large amounts of porpoises to be entangled in gillnets
Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...
. Habitat loss and pollution are also thought to be major threats.
Local conservation groups in Korea, such as at Yeosu
Yeosu (; ''Yeosu-si''), historically also Yosu, and known to the Japanese as Reisui during the period when Korea was under Japanese rule, is a city located on the southern coast of the Korean Peninsula in South Jeolla Province, South Korea an ...
, have started campaigning for the protection of the local populations.
In captivity
Finless porpoises have commonly been kept in Japan, as well as China and Indonesia. Ninety four in total have been in captivity in Japan, eleven in China, and at least two in Indonesia. Japan has had three establishments designated for breeding them, and there have been five recorded births. Three, however, died moments after birth, but two survived for several years.
See also
*List of cetaceans
Cetacea is an infraorder that comprises the 94 species of whales, dolphins, and porpoises. It is divided into toothed whales (Odontoceti) and baleen whales (Mysticeti), which diverged from each other in the Eocene some 50 million years ago (m ...
References
{{Taxonbar, from1=Q61887197, from2=Q22286308
Porpoises
Mammals described in 1975
Mammals of China
Mammals of Korea
Cetaceans of the Pacific Ocean
Mammals of Japan
Taxobox binomials not recognized by IUCN