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The Yangtze finless porpoise (''Neophocaena asiaeorientalis'') is a species of
toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of t ...
in the family
Phocoenidae Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals an ...
. It is
endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to the
Yangtze River The Yangtze or Yangzi ( or ; ) is the longest list of rivers of Asia, river in Asia, the list of rivers by length, third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in th ...
in
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, making it the country's only known freshwater
cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
following the possible extinction of the
baiji 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 ...
(''Lipotes vexillifer''). The Yangtze finless porpoise is considered critically endangered and it is estimated that only about 1,000 remain. This small
toothed whale The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species of t ...
faces many of the same threats that caused the
baiji 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 ...
dolphin to possibly become extinct. The
Yangtze River The Yangtze or Yangzi ( or ; ) is the longest list of rivers of Asia, river in Asia, the list of rivers by length, third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in th ...
has a high traffic rate of human activity causing population declines due to
illegal fishing Illegal, unreported and unregulated fishing (IUU) is an issue around the world. Fishing industry observers believe IUU occurs in most fisheries, and accounts for up to 30% of total catches in some important fisheries. Illegal fishing takes pl ...
,
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
, vessel traffic, and
dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, a ...
construction. Due to the rapidly declining population of the species, the Chinese Government and conservation charities are working to help save it from extinction.


Taxonomy

The Yangtze finless porpoise is considered a freshwater
cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
(whales, dolphins, and porpoises that live in a variety of aquatic habitats). The finless porpoise originally inhabited salt water niches along the coast of the
Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
Ocean. However, a population dispersed into the fresh water environment of the Yangtze River. Recent studies have found that the
East Asian finless porpoise The East Asian finless porpoise (''Neophocaena sunameri'') is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise (''N. asiaeorientalis'') was formerly considered a subspecies ...
(''N. sunameri'') and the Yangtze finless porpoise (''N. asiaeorientalis'') have had separate reproduction and gene flow for thousands of years. The
East Asian finless porpoise The East Asian finless porpoise (''Neophocaena sunameri'') is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise (''N. asiaeorientalis'') was formerly considered a subspecies ...
and the Yangtze finless porpoise were formerly considered one species going by the scientific name of ''N. phocaenoides'', but genetic studies support the Yangtze finless porpoise being a distinct species, or at least an incipient one, due to the lack of gene flow.


Names

In
Mandarin Chinese Mandarin (; ) is a group of Chinese (Sinitic) dialects that are natively spoken across most of northern and southwestern China. The group includes the Beijing dialect, the basis of the phonology of Standard Chinese, the official language of ...
, it is known as jiangtun (, p ''jiāngtún'',  "river piglet")


Description

A finless porpoise can grow up to in length and weigh up to , however, most are smaller than this. The average adult is usually in length and weighs around . Adult females tend to be smaller than adult males. Flippers are curved with pointed ends and are relative large, about 20% of their total body length. The finless porpoise tends to be stocky in the middle body and slimmer towards the tail. In general they are more slender in shape than most other ''
Phocoenidae Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals an ...
''. These
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...
also have unique foreheads, with a very steep forehead and no beak. In addition, they have an unfused neck vertebrae that allows free head movement. They have 15–22 pairs of teeth on the upper and lower jaw. Body color and dorsal ridge sizes vary depending on the geographical location of the finless porpoise.


Dorsal ridge

As denoted by the name, these finless porpoises have flat backs and are completely finless. Instead of a
dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
, these porpoises have a dorsal ridge or "groove" that is covered in varying rows of
tubercles In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...
. These
tubercles In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...
are round in shape and raised. Recent studies have found that tubercles do have biological and mechanical functions that benefit the porpoise; for example, the tubercles are a sensory organ and can also help with movement through the water. The amount of rows of
tubercles In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...
and dorsal ridge sizes vary depending on the species and location of the porpoise. The
East Asian finless porpoise The East Asian finless porpoise (''Neophocaena sunameri'') is a species of porpoise native to the East China Sea, Yellow Sea, and the seas around Japan. The Yangtze finless porpoise (''N. asiaeorientalis'') was formerly considered a subspecies ...
and the Yangtze finless porpoise usually have a higher and narrower ridge with only 1 - 10 rows of tubercles, whereas the
Indo-Pacific finless porpoise The Indo-Pacific finless porpoise (''Neophocaena phocaenoides'') is one of eight porpoise species. The species ranges throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait ...
(''Neophocaena phocaenoides'') tends to have a lower and wider ridge with 10–25 rows of tubercles.


Body color

Body color also varies depending on habitat location and age. Newborn Yangtze finless porpoises and East Asian finless porpoises tend to be a dark gray or black color that lightens within a few months to a lighter gray. However, the
Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
species has a reverse trend, in which newborns are light in color and get darker with age. After death Yangtze finless porpoises usually become black in color. It is also very common for there to be lighter patches of color around the mouth and genitals; however this coloration is more noticeable at a young age.


Habitat

The Yangtze finless porpoise is found in the main body of the
Yangtze River The Yangtze or Yangzi ( or ; ) is the longest list of rivers of Asia, river in Asia, the list of rivers by length, third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in th ...
and in connecting lakes. They are exclusive to fresh water, making them different from other finless porpoises. They tend to be found in shallow bay areas,
swamps A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
, and
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
year round as they are not a migratory species. However, distribution changes do occur seasonally. In the winter the highest distribution was found in the middle and lower regions of the
Yangtze River The Yangtze or Yangzi ( or ; ) is the longest list of rivers of Asia, river in Asia, the list of rivers by length, third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in th ...
. Their preferred climate is
tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...
or warm temperatures.


Diet

The diet of the Yangtze finless porpoise may vary according to the season and the dominant prey of the season. This variation in their diet suggest that the Yangtze finless porpoise may be opportunistic feeders. Among the fishes in their diet, the most common are ''Coilia brachygnathus,'' ''Pseudobrama simoni,'' ''Pelteobagrus nitidus,'' and ''Hemiculter bleekeri''.


Behavior

The Yangtze finless porpoise tends to be shy; it does not come to the surface of the water often when there is human activity nearby. They are usually most active when eating and usually spend most of their time near river banks or at the merging of two waterways. Yangtze finless porpoises travel in small groups of about three to six; however groups of 20 have been reported. A radio-tracking study confirmed that the average diving behavior consisted of one long dive followed by two shorter dives. These longer dives were more common during the day time. In the
Yangtze River The Yangtze or Yangzi ( or ; ) is the longest list of rivers of Asia, river in Asia, the list of rivers by length, third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in th ...
, finless porpoises are known to leap from the water and perform "tail stands". At night the finless porpoises tended to go into sleep cycles and be less active. Another unique behavior reported, but that is not heavily confirmed, is that mothers have been seen carrying calves on their backs.


Extinction

After the functional extinction 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 ...
and the rapid decreasing of population, the Chinese government has given this species the utmost conservation status of ''National First Grade Key Protected Wild Animal'' to ensure its survival. However, the population decrease is accelerating due to lack of food,
pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...
, and ship movement, and the species has a high chance (86.06%) of becoming
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
within the next 100 years. Another reason that they have been dropping in numbers is because of underwater noise pollution. If spectra levels in the water surpass the underwater acoustic thresholds for the porpoise, their chance of survival is greatly threatened. Global conservation agencies and charities, such as the
World Wildlife Fund The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wo ...
and
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
, have been collaborating with the Chinese government to ensure the survival of the species.


Threats


Fishing

Bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
by unwary fishermen may be a factor for the ongoing decline of the Yangtze finless porpoise. Illegal fishing and hazardous gear, like
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 ...
, is widely used in the Yangtze River. The preferred habitat of the Yangtze Finless Porpoise overlaps extensively with the usage of gillnets, which makes the species particularly vulnerable to entanglement and subsequent drowning. However, a recent large-scale interview survey conducted in fishing communities along the banks of the Yangtze, by the IUCN, suggests that mortality due to bycatch may have decreased over the past two decades as the porpoise population has declined, and have concluded that gillnetting is unlikely to be the primary cause of their decline.


Development

Increased traffic, pollution, and habitat degradation of the river have contributed to population declines. The increased vessel traffic may cause death from propeller strikes, and the boat noise may mask the porpoise's ability to communicate with other porpoises, as well as hindering their
biosonar Echolocation, also called bio sonar, is a biological sonar used by several animal species. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these ...
which compromises foraging and locomotion. Porpoise mortality associated with vessel collisions has increased substantially in recent years, in contrast to mortality from by-catch. Widespread
sand mining Sand mining is the extraction of sand, mainly through an open pit (or sand pit) but sometimes mined from beaches and inland dunes or dredged from ocean and river beds. Sand is often used in manufacturing, for example as an abrasive or in concret ...
of the river and lake beds and banks has destroyed important habitats for porpoises and food items, as well as other environmental issues. This problem is especially serious in the
Dongting Dongting Lake () is a large, shallow lake in northeastern Hunan Province, China. It is a flood basin of the Yangtze River, so its volume depends on the season. The provinces of Hubei and Hunan are named after their location relative to the la ...
and Poyang Lakes. There are currently four hundred million living along the river basin as well as thousands of factories, which together discharge tremendous quantities of domestic sewage and agricultural and industrial waste. It has not been proven that this impacts the Yangtze finless porpoise's health, fertility, or population. In April 2004, five porpoises died in Dongting Lake within a single week due to short-term exposure to pesticides, possibly in combination with long-term exposure to
mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...
and
chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...
. Dams have major effects on river and
lake ecology A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems (''lentic'' ref ...
, and inhibit access between the river and adjoining lakes or tributaries in the Yangtze, as well as affecting migrating prey items. The
Three Gorges Dam The Three Gorges Dam is a hydroelectric gravity dam that spans the Yangtze River by the town of Sandouping, in Yiling District, Yichang, Hubei province, central China, downstream of the Three Gorges. The Three Gorges Dam has been the world ...
in particular has altered and will continue to alter, downstream conditions in the Yangtze River and its connected/adjoining lakes. Construction of the
Poyang Lake Dam The Poyang Lake Dam, referred to as the ''Poyang Lake Water Conservancy Project'', is dam proposed to maintain water levels at Poyang Lake in Jiangxi Province, China. The lake is China's largest freshwater resource but has significantly decreased ...
likely to damage the remaining population severely.


Conservation

As of 2014, 505 porpoises remain in the main section of the
Yangtze The Yangtze or Yangzi ( or ; ) is the longest river in Asia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains (Tibetan Plateau) and flows ...
, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of the porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. A 2012 survey by the
World Wildlife Fund The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wo ...
indicated the rate of decline had accelerated to 13.7% per year. By 2017, the number in the Yangtze had increased to 1,012. Due to ongoing protection efforts, the porpoises have reappeared in places like
Nantong Nantong (; alternate names: Nan-t'ung, Nantung, Tongzhou, or Tungchow; Qihai dialect: ) is a prefecture-level city in southeastern Jiangsu province of China, province, China. Located on the northern bank of the Yangtze River, near the river mouth. ...
, where sightings had been rare in recent years. A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately environmental degradation. Some of these can be seen in damming of the river as well as illegal fishing activity. To protect the species, China's Ministry of Agriculture classified the species as being National First Grade Key Protected Wild Animal, the strictest classification by law, meaning it is illegal to bring harm to a porpoise. The
Tian-e-Zhou Oxbow Nature Reserve The Tian-e-Zhou Oxbow Nature Reserve is an area of wetland in the Yangtze basin near Shishou, Hubei province, People's Republic of China. Inside the reserve is the Tian'e-Zhou lake which was an intended sanctuary for the baiji (Yangtze river dolph ...
has worked for years to protect the porpoises. The reserve, which is sponsored by the
Chinese government The Government of the People's Republic of China () is an authoritarian political system in the People's Republic of China under the exclusive political leadership of the Chinese Communist Party (CCP). It consists of legislative, executive, mili ...
,
World Wildlife Fund The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wo ...
, the
Coca-Cola Company The Coca-Cola Company is an American multinational beverage corporation founded in 1892, best known as the producer of Coca-Cola. The Coca-Cola Company also manufactures, sells, and markets other non-alcoholic beverage concentrates and syrups, ...
, and others, increased its porpoise population from five to forty in twenty-five years. By 2017, there were 80 individuals, nearing the total capacity of 100. The
Chinese Academy of Science The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Republic ...
's Wuhan Institute of Hydrobiology has been working with the
World Wildlife Fund The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the Wo ...
to ensure the future for this subspecies, and have placed five porpoises in another well-protected area, the He-wang-miao oxbow. Five protected natural reserves have been established in areas of the highest population density and mortality rates with measures being taken to ban patrolling and harmful fishing gear in those areas. There have also been efforts to study porpoise biology to help specialize conservation through captivation breeding. The Baiji Dolphinarium, was established in 1992 at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan which allowing the study of behavioral and biological factors affecting the finless porpoise, specifically breeding biology like seasonal changes in reproductive hormones and breeding behavior. The first Yangtze finless porpoise was born in captivity on July 5th, 2005, in Baji Dolphinarium in
Wuhan Wuhan (, ; ; ) is the capital of Hubei, Hubei Province in the China, People's Republic of China. It is the largest city in Hubei and the most populous city in Central China, with a population of over eleven million, the List of cities in China ...
.


References

{{Taxonbar, from1=Q61887190, from2=Q22286308 Porpoises Endemic fauna of China Mammals of China Yangtze River Mammals described in 1972