Finless Porpoise (Neophocaena phocaenoides)
Range Description:
The type specimen was from the Yangtze River, Kiangsu
[=Jiangsu] Province, China, ~129 km (=80 miles) northwest of Shanghai (Pilleri
and Gihr 1972).
In general, the species occurs in a narrow strip of shallow (usually et al.
2010), but it probably represents an extralimital stray rather than an extension
of the species range.) The distribution also includes a few estuaries and
rivers (e.g., the N. a. asiaeorientalis subspecies appears to be found
exclusively in the Yangtze River system; Gao 1991; Gao and Zhou 1995). Human
coastal development and other activities already may have substantially reduced
and fragmented the distribution of finless porpoises (Reeves et al. 1997).
N. a. sunameri Coastal waters from the Taiwan Strait, including the
western coast of Taiwan (mainly the Matsu and Chinmen Islands), through the East
China Sea north to the Bohai/Yellow Sea in China and the waters of Korea and
Japan (Gao 1991, Gao and Zhou 1995). Korean and Japanese populations are
geographically separate (Shirakihara et al. 1992,Yoshida et al. 2001, Yoshida
2002).See in Thailand
N. a. asiaeorientalis Middle and lower reaches of the Yangtze River (=
Chang Jiang), where it ranges (or did until recently) to 1,600 km upstream, i.e.
to the gorges above Yichang (200 m above sea level). The range includes Poyang
and Dongting lakes and their tributaries, the Gan Jiang and the Xiang Jiang (Gao
1991, Gao and Zhou 1995). The subspecies is thought to be restricted to fresh
water.
Countries: Native:
China; Japan; Korea, Republic of; Taiwan, Province of China
Narrow-ridged Finless Porpoises are found mainly in coastal
waters, including shallow bays, possibly mangrove swamps, estuaries, and some
large rivers. However, they can also occur in shallow waters (
In Japanese waters, finless porpoises prefer shallow depths.
Systems: Freshwater; Marine
Description
The finless porpoise (Neophocaena phocaenoides) is one of six porpoise species. In the waters around Japan, at the northern end of its range, it is known as the sunameri (砂滑). A freshwater population found in the Yangtze River in China is known locally as the jiangzhu (江猪) or "river pig". There is a degree of taxonomic uncertainty surrounding the species, with the N. p. phocaenoides subspecies perhaps representing a different species from N. p. sunameri and N. p. asiaeorientalis.
Physical description
The finless porpoise almost completely lacks a dorsal fin. Instead there is a
low ridge covered in thick denticulated skin.
Adults are a uniform, light grey colour. Newborn calves are mostly black with
grey around the dorsal ridge area, becoming fully grey after four to six months.
Adults grow more than 1.55 m (5 ft) in length and up to 3045 kg (65100 lb) in
weight. Males become sexually mature at around four to six years of age, and
females at around six to 9 years of age.
Diet
The finless porpoise, subspecies Neomeris kurrachiensis, in the vicinity
of Karachi, British India, now Pakistan, as drawn by R. A. Sterndale, in the
Journal of the Bombay Natural History Society, volume 1, number 1, 1886.
Finless porpoises are reported to eat fish and shrimp in the Yangtze River, and
fish, shrimp and squid in the Yellow Sea/Bohai area and off Pakistan. In
Japanese waters, they are known to eat fish, shrimp, squid, cuttle fish and
octopuses. They are opportunistic feeders using various kinds of available food
items available in their habitat. Seasonal changes in their diets have not been
studied. They also apparently ingest some plant material when living in
estuaries, mangroves, and rivers, including leaves, rice, and eggs deposited on
vegetation.
Schooling
Finless porpoises are generally found as singles, pairs, or in groups of up to
12, although aggregations of up to about 50 have been reported. Recent data
suggest the basic unit of a finless porpoise pod is a mother/calf pair or two
adults, and schools of three or more individuals are aggregations of these units
or of solitary individuals. Social structure seems to be underdeveloped in the
species, and the mother/calf pair is probably the only stable social unit
Behaviour and reproduction
Like other porpoises, their behaviour tends to be not as energetic and showy as
that of dolphins. They do not ride bow waves, and in some areas appear to be shy
of boats. In the Yangtze River, finless porpoises are known to leap from the
water and perform "tail stands". Breeding occurs in late spring and early
summer, after a gestation period of 1011 months. The calf clings to the
denticulated area of skin on their mother's back and is carried by her as she
swims. Calves are weaned at 615 months.
Swimming style
Although they show no acrobatics in the water, finless porpoises are believed to
be very active swimmers. They typically swim just beneath the surface of the
water and roll to one side when surfacing to breathe. This rolling movement
disturbs very little water on the surface, so they are often overlooked when
rising to breathe. Surfacing generally lasts for one minute, as they take three
to four quick successive breaths, then quickly submerge into the water. They
often surface a great distance from the point where they dive beneath the
water's surface.
Conservation
On the IUCN "red list" database of endangered species, the finless porpoise is
listed as "vulnerable" due to apparent declines in the best studied populations
in the Sea of Japan, and the Yangtze river basin. The fresh water subspecies in
the Yangtze river is characterized as endangered. Since this species remains in
coastal waters, it has a high degree of interaction with humans, which often
puts the finless porpoise at risk. Like other porpoises, large numbers of this
species are killed by entanglement in gill nets. Except for being briefly hunted
after World War II 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 and this coverage had since been
extended to all Japanese coastal waters. The primary danger to the species is
the environmental degradation. In addition, unlike other members of this family,
finless porpoises have lived in captivity for over 15 years.
There are no well-established estimates of the animals' abundance. However, a
comparison of two surveys, one from the late 1970s and the other from 19992000,
shows a decline in population and distribution. Scientists believe this decline
has been ongoing for decades, and the current population is just a fraction of
its historical levels. A 2006 expedition estimated fewer than 400 animals
survived in the Yangtze River.
At the end of 2006, an estimated 1400 porpoises were left living in China, with
between 700 and 900 in the Yangtze and another 500 in Poyang and Dongting Lakes.
The 2007 population levels were less than half the 1997 levels, and the
population is dropping at a rate of 7.3% per year. Current conservation efforts
were undertaken alongside those for the recently functionally extinct baiji. In
1990, five individuals were relocated to the Tian-e-Zhou Oxbow Nature Reserve,
and now a population of 28 currently inhabit the lake.
Sand dredging has become a mainstay of local economic development in the last
few years, and it is an important source of revenue in the region that borders
Poyang Lake. At the same time, though, high-density dredging projects have been
the principal cause of the death of the local wildlife population.
Dredging makes the waters of the lake muddier, and the porpoises cannot see as
far as they once could, and have to rely on their highly developed sonar systems
to avoid obstacles and look for food. Large ships enter and leave the lake at
the rate of two a minute, and such a high density of shipping means the
porpoises have difficulty hearing their food, and also cannot swim freely from
one bank to the other.
The Finless porpoise is listed on Appendix II[6] of the Convention on the
Conservation of Migratory Species of Wild Animals (CMS). It is listed on
Appendix II[6] as it has an unfavourable conservation status or would benefit
significantly from international co-operation organised by tailored agreements.