Animals & Society

Chinese river dolphin

March 22, 2012, 2:25 pm
Content Cover Image

Chinese River dolphin: Source: Wang Ding

The Chinese River dolphin (scientific name: Lipotes vexillifer) is one of three species of river dolphins in the family Inia. (The other two are the Amazon river dolphin and the Franciscana.)  2002 was the last time a Chinese river dolphin, also known by the common name Baiji, was seen alive. There have been three unconfirmed sightings since then. After an intensive, but fruitless search for this rare cetacean in 2006, it is now believed that the Baiji may be extinct; which would earn this dolphin the grim record of being the first cetacean to disappear as a result of human activity.

caption Lipotes Vexillifer. Source: Alessio Marrucci
caption Size comparison of an average human against the Chinese dolphin. Source: Chris Huh

Conservation Status:

May be Extinct

Scientific Classification

Kingdom: Animalia
Phylum:--- Chordata
Class:------ Mammalia
Order:-------- Cetacea
Family:-------- Iniidae
Genus:--------- Lipotes
Species:--------Lipotes vexillifer (Miller, 1918)

Common Names:
Baiji
Changjiang dolphin
Chinese lake dolphin
Chinese river dolphin
White flag dolphin
White-flag dolphin
Whitefin dolphin
Yangtze river dolphin

The Chinese river dolphin was found in the mouth of the Chang Jiang (Yangtze River) to a point about 1900 kilometres up the river, as well as in the middle and lower regions of the Quintangjiang River and in the Dongting and Poyang lakes.

Baijis have long been recognised as one of the world's rarest mammals, and are extremely shy animals, making observation of them in the wild extremely difficult. Consequently, relatively little is known of the species. They are most active through the night from early evening to early morning . They tend to live in small groups of three to four individuals, with the largest group ever seen comprising of 16 members. One study found that they often swim with Finless porpoises (Neophocaena phocaenoides), the only other cetacean in the Yangtze River, which is also threatened (classified as Endangered on the IUCN Red List). Baijis break the surface of the water without creating a splash and breathe smoothly. They feed on a wide range of freshwater fish, which are eaten whole. It is thought that breeding occurs in the first part of the year, with most births peaking between February and April.

It is an extremely shy and graceful freshwater dolphin, with a rather stocky body, roughly the size of an adult human . It is bluish-grey in colour becoming whitish on the underside, but seems white or greyish from a distance. In common with other river dolphins, it has a very long, narrow beak with a slightly upturned tip, and small eyes placed high up on the face . The dorsal fin is positioned low on the body and is triangular in shape, and the flippers are rounded. The species displays sexual dimorphism, with females generally larger than males. The Baiji is the only species in this genus, the name of which, Lipotes, derives from the Greek word meaning left behind, referring to its limited range

In Chinese folklore, the Baiji is dubbed goddess of the Yangtze, a beneficent animal once revered by the fishing people of the river. The species was declared a national treasure of China and has been a protected species since 1975 . However, this had very little effect on the species population, which continued to decline despite conservation efforts and legal protection. It was thought that the only chance to save the species from extinction would be to remove all of the surviving individuals from the Yangtze into the Baiji Semi-natural Reserve, which was created in 1992. However, since the unsuccessful search for any surviving Baijis in 2006, it is unlikely that a captive breeding programme will now ever be possible. The World Conservation Union (IUCN) has now classified the Baiji as Critically Endangered (Possibly Extinct); it cannot be definitively classified as Extinct until further surveys are undertaken. Sadly, it seems that this goddess of the Yangtze will be the first cetacean species to become extinct in modern times as a result of human activities.

The Yangtze River is one of the world's busiest waterways, and is subject to a great range of human pressures that have had a devastating effect on the Baiji. The main threat causing the decline of this species in recent years is illegal fishing using electricity, which has accounted for 40 percent of known Baiji deaths. These dolphins have also become caught in fishing gear, and engineering explosions used to keep navigation channels open are another source of mortality. Vessels carrying pesticides or herbicides occasionally overturn, causing poisoning of the ecosystem, resulting in further deaths . An additional source of water pollution comes from the 15.6 billion cubic metres of wastewater discharged into the Yangtze every year, 80 percent of which is not treated. A huge volume of boat traffic uses the river; noise levels are high and boat strikes a possibility. Furthermore, the banks of the Yangtze have been greatly modified in order to prevent flooding of adjacent land; such projects have great impacts on the ecosystem, both during construction and from the resulting habitat changes. Dam construction has been shown to reduce the availability of fish, which is exacerbated by overfishing and water pollution. The recent construction of the Three Gorges Dam, the largest dam in the world, is likely to affect fish stocks and natural flooding patterns. For many years the Baiji population is thought to have been diminished, which in itself may have caused the species to enter an extinction vortex; small populations often suffer low genetic fitness and are often less able to adapt to environmental changes .

Physical Description

Salient morphological features include endothermic regulation and bilateral symmetry. Baiji, like other dolphins, have streamlined, fusiform bodies. They have rounded flippers and long, beaklike, upturned snouts, which are completely hairless. Their small but functional eyes sit high on their heads, and their blowholes are elliptical and oriented longitudinally. Baiji are pale blue-grey dorsally and white ventrally. They have 30-36 teeth per side of both the upper and lower jaws. Baiji have no fore-stomachs but their main stomachs consist of three chambers, and they lack ceca. The skulls of these dolphins lack maxillary crests, and the palatal portions of the maxillae contact one another. Female baiji are larger than males. Females range from 185 to 253 cm in length and weigh 64-167 kg, while males range from 141 to 216 cm in length and weigh 42-125 kg. (Nowak, 1999)

Behaviour

Summary behaviours are: natatorial; diurnal; motile; and social. Due to their cryptic habits, much of the behavior of Baiji remains a mystery. They are usually found in pairs, which aggregate to form larger social units of about ten individuals. Most of their time is spent in the vicinity of large eddies, where they search for fish during the day. At night they rest in areas of slow current. The population density in the Quintangjiang was estimated (in 1978 and 1980) at one Baiji every four km.(Nowak, 1999)

Voice and Sound Production

In the turbid waters of the Yangtze, vision is mostly useless, so Baiji use echolocation to navigate and find prey. They communicate with one another using whistles and other acoustic signals.(Nowak, 1999) Besides acoustic communication, the Yangtze river dolphin employs tactile and chemical sensory perception channels.

Distribution and Movements

In the past, this river dolphin's range extended from the mouth of the Yangtze River, China, upstream to 50 kilometres above the Gezhouba Dam. More recently, it was found only in the middle and lower reaches of the Yangtze River, between two large tributary lakes, Dongting and Poyang. In 1997, a scant 17 individuals of this extremely rare species were seen; in 1999 this number fell to just four. During an expedition in November and December 2006 an intensive search was undertaken in the Yangtze River, but scientist failed to find a single Baiji. It is now thought that the Baiji may be extinct.

caption Map of conservation efforts of the Baiji (Lipotes vexillifer) along the Yangtze. Source: Chris Huh

Habitat

The Baiji is an exclusive freshwater species. Within the Yangtze River, they are attracted to riparian areas where tributaries meet the river, particularly where there are sand bars with sizable eddies. Aquatic biomes in which the species may have historically occurred are lakes, ponds, rivers, streams and estuaries.

Baiji are freshwater dolphins that historically inhabited the lower reaches of China's Yangtze and Quintangjiang Rivers, and in the Poyang and Dongting Lakes. They prefer to stay near large eddies that form next to sandbars. (Nowak, 1999)

Feeding Habits

The diet of Baiji consists chiefly of fish. They use their long beaks to probe muddy bottoms for prey. Their dives are short, lasting only ten to twenty seconds. Baiji have poor eyesight but use a highly developed echolocation faculty to find food. These mammals seek food in the shallow water near sandbanks or close to the mouth of tributaries of the river.

Predation

Baiji are top-level consumers in the Yangtze River ecosystem. There are no reports of predation on Baiji, except by humans

Economic Importance for Humans

Baiji are important culturally, since they have long been revered by custom. In the past, the fat of accidentally killed individuals was used for medicinal purposes and the flesh consumed. The current plight of baiji--designated a national treasure "of the first order" by China--has raised awareness of the need for conservation of river systems worldwide. (baiji.org Foundation, 2006) Baiji have no known negative effects on humans. Positive impacts of the Baiji are a source of medicine as well as research and education.

Threats and Conservation Status

caption Yangtze River below the massive Three Gorges Dam. @ C.Michael Hogan

Lipotes vexillifer is probably the most endangered of all cetaceans. It is listed as critically endangered on the IUCN's Red List of Threatened Species, it is listed as endangered by the U.S. Fish and Wildlife Service, and it is in CITES Appendix I. The total population is estimated at less than 100 animals; surveys in the late 1990s put the minimum population estimate at 13. A 2006 survey of the entire range of L. vexillifer failed to find any individuals at all, and it is probable that the species is now extinct.

There are four major factors that threaten Baiji survival: dams and floodgates that block fish migration in the river's tributaries and lakes as well as alter the natural hydrology of the Yangtze; fishery exploitation that accidentally kills dolphins; water pollution; and boat propellers. Population numbers also declined through hunting and development of irrigation facilities. The heavy pollution and underwater noise characteristic of the Yangtze also affects the Baiji. These stresses, as well as lack of food, can inhibit reproduction.

China began providing nominal legal protection in 1975. Programs are being established to breed Lipotes vexillifer in captivity, though no one has yet succeeded at housing wild Baiji for long. In 1992 an oxbow jutting off from the main Yangtze River was set aside as a reserve where Baiji could be relocated and allowed to live under semi-natural conditions. In the face of ongoing degradation of the Yangtze river, this ex-situ conservation strategy may be the species only hope for survival. In 2006, a survey of the entire range of baiji will be carried out by the Baiji.org foundation in collaboration with Chinese administrators and the Institute for Hydrobiology. Scientists are hopeful this survey will provide a better idea of exactly how many Baiji remain and where they are located, so that they can eventually be relocated to reserves. (baiji.org Foundation, 2006; Nowak, 1999)>

IUCN Red List classifies the species as Critically Endangered (Possibly Extinct) [CR (PE)]. The United States Federal List places the species as Endangered. CITES lists the species in Appendix I.

The IUCN Red List provides additional details of the status of the species:

The first estimate of abundance based on quantitative survey data (1979-81) was made by Zhou (1982), who guessed that there were only about 400 animals all told. On the basis of surveys conducted in 1985-86, Chen and Hua (1989) made an educated guess that the total population was around 300. Surveys by Zhou and Li (1989) between 1982 and 1986 suggested that there were 100 Baiji in a 770 km segment of the lower Yangtze from Hukou to the river mouth, compared with 78 to 79 dolphins counted by Chen and Hua (1989) in the same segment in 1985-86. Repeated surveys of a 500 km segment of the lower Yangtze (Nanjing-Hukou) in 1989-91 produced a maximal count of 12 individuals, leading Zhou et al. (1998) to infer a total abundance of about 30 Baiji in that river segment. Those authors reasoned that if the species still inhabited its historical range of about 1700 linear kilometres of river, with a density similar to that found in their study area, the total population in the early 1990s would have been only about 100. Attempted comprehensive surveys of the entire species' range in 1997-99 resulted in a maximal count (November 1997) of 13 dolphins (including one calf), leading to the generally accepted view that abundance had continued to decline and that the total population was by that time very small. The sighting rate in the three years of surveys declined at an annual rate of about 10% (Zhang et al. 2003). Informed guesses in the early 2000s were that there could be only "a few dozen" (Zhou 2002) and "very likely ? less than a hundred" (Reeves et al. 2003) baiji left (also see Wang 2000, IWC 2001, Zhang et al. 2003). Although no credible time series of counts or abundance estimates is available to provide a rigorous evaluation of trends, there is an overwhelming consensus that the baiji population declined rapidly over the past several decades.

During surveys in the late 1990s Baiji were found mainly in several segments of the Yangtze between Tongling and Dongting Lakes, such as the Tongling section, the Poyang Lake mouth area, and the Honghu section (Wang 2000, Zhang et al. 2003).

More recent evidence suggests that this species might already be extinct. The last documented sighting (supported by photographic evidence) was in 2002 and the last confirmed stranding was in 2001 (Turvey et al. in prep.). In November and December 2006 a comprehensive visual and acoustic survey failed to find a single baiji in the Yangtze River (Turvey et al. in prep.). Two research vessels covered the known habitat of Baiji from Yichang to Shanghai in both the upstream and downstream directions (for quadruple coverage). In addition, one vessel towed a hydrophone to listen for baiji whistles and clicks during the downstream survey. Although Dongting and Poyang Lakes were not covered in the 2006 Yangtze mainstem survey, no baiji have been seen since 2000 by researchers studying finless porpoises in those lakes. A few undocumented sightings have been reported since 2004, but there are no photographs or physical evidence for the species continued existence. The preponderance of evidence indicates that the baiji is very close to extinction or might already be extinct.

The range contraction and the decline in Baiji abundance were caused by a combination of factors, including: possibly some level of direct exploitation historically; incidental mortality from interactions with fisheries; vessel traffic, management of navigation channels, and harbour construction; and loss or degradation of habitat by water development, land use practices and pollution.

During China's "great leap forward" the baiji's traditionally venerated status as "goddess of the river" was denounced and baiji skin was used to produce handbags and gloves (Zhou and Zhang 1991).

Entanglement in fishing gear was estimated in the 1970s to 1980s to have been responsible for at least half of observed mortality (Lin et al. 1985, Zhou and Li 1989, Chen 1989, Chen et al. 1997). Longlines with thousands of unbaited hooks used for snagging bottom fish ("rolling hooks") accounted for 7 of 13 entanglement deaths recorded in the lower Yangtze between 1978 and 1985 (Zhou and Li 1989) and 15 of 28 in the middle reaches between 1973 and 1983 (Zhou and Wang 1994, also see Chen et al. 1997). Additional deaths from entanglement in rolling hooks were documented in the 1990s (Zhou et al. 1998). Baiji often have scars and open wounds from rolling hooks, and hook remains are sometimes found in the stomachs of dead animals (Lin et al. 1985, Zhou and Li 1989). Deaths also result from entanglement in gill and fyke nets (Zhou and Wang 1994). According to Zhou et al.(1998), both rolling hooks and fyke nets are banned in the Yangtze "because both are harmful to fisheries resources, and because of incidental killing of Baiji", but enforcement of these prohibitions is "very difficult" and therefore incidental mortality is likely to continue.

Electric fishing, although "strictly banned" in the Yangtze (Zhou et al. 1998), is widely practiced, particularly in the centre of the baiji's distribution (IWC 2001). By the early 2000s this fishing method had come to be viewed as the most important and immediate direct threat to the baiji's survival (Zhang et al. 2003). The electric shocks kill baiji outright (Chen and Hua 1989, Wang Ding in IWC 2001: 276) and unselectively kill other aquatic organisms, including the baiji's prey.

Propeller strikes have killed and injured Baiji (Zhou and Zhang 1991, Chen et al. 1997) and are considered an increasing threat in view of the rapid industrial and economic growth of China, with its associated expansion of traffic on the Yangtze (Chen 1989, Chen and Hua 1989, Zhou and Li 1989, Zhou 1992, Zhou et al. 1998).

Explosives, used to deepen or widen river channels or for fishing, are another cause of baiji mortality (Lin et al. 1985, Zhou and Li 1989, IWC 2001).

Water development has transformed the baiji's habitat in important ways, e.g., by interrupting their movements upstream of dams, eliminating their access to tributaries and appended lakes, and reducing fish productivity (Liu et al. 2000). A dead baiji found at the bottom of a gate for a ship lock in a Yangtze tributary may have been killed accidentally by the structure (Liu et al. 2000). Chen and Hua (1987) predicted that the controversial Three Gorges Dam, completed in the early 2000s, would eliminate counter-current habitat for approximately 200 km downstream and degrade the existing counter-current systems for another 160 km downstream. Further, stratification in the reservoir will cause the water released below the dam to be cooler than previously, potentially affecting baiji and their prey. The downstream effects of Gezhouba Dam were not as extreme as those predicted for Three Gorges Dam because the former is a low-head, run-of-the-river structure (Zhong and Power 1996), meaning that sediment is allowed to pass through (which allows the formation of the counter-currents where baiji are generally found - see above) and no reservoir forms. Another effect of Three Gorges Dam will be to facilitate large ship traffic in the upper reaches of the Yangtze and thereby increase the amount of underwater noise and the incidence of vessel collisions with baiji (Chen and Hua 1989).

Industrial expansion and intensified agriculture (both facilitated by water development) have already caused major ecological problems in the Yangtze system. For example, Dongting and Poyang Lakes have become much shallower because of siltation from deforestation and agricultural development; in fact, it has been suggested that Dongting Lake could disappear altogether within a decade (Liu et al. 2000).

Pollutant loads in the Yangtze are expected to increase with industrialization and the spread of modern agricultural practices. Approximately 40% of China's industrial and agricultural output comes from the Yangtze basin, with more than 16 billion cubic meters of wastewater discharged into the river annually, of which more than 12 billion cubic meters is industrially polluted and largely untreated (Zhou et al. 1998).

The Baiji is designated in the First Category of National Key Protected Wildlife Species and has full legal protection throughout its range. Protection from deliberate killing or injury appears to be effective but, as noted above, prohibitions on harmful fishing methods are generally not very effective and there is no evidence that baiji are protected in any way from the mortality, injury, and health impairment caused by the other threats listed above.

Since the late 1980s, the primary strategy to prevent the baiji's extinction was to capture as many dolphins as possible and to introduce them into "semi-natural reserves", one of which (Tongling) was approved by the Chinese government in the 1980s, and the other (Shishou) in the 1990s. The approach of using semi-natural reserves as components of a broad-based conservation strategy was endorsed by international panels of scientists in 1986 (Perrin and Brownell 1989) and 1993 (Ellis et al. 1993, Zhou et al. 1994). It was premised on the assumption that the total dolphin population in the 1980s was approximately 300 and declining. Importantly, it was also premised on the expectation that an ex situ breeding population, preferably housed at two or more sites, would provide surplus animals for replenishment or reestablishment of the wild population, and not be viewed as an end in itself (Perrin and Brownell 1989, Ralls 1989, Perrin 1999).

However, the expectation that sufficient numbers of Baiji could be caught and placed in the reserves to establish a viable ex situ population has proven unrealistic. Six capture expeditions, each lasting two to three months, were conducted between Chenglingji and Gongan in the 1990s. In 1995 a female baiji was caught and released in the Shishou Reserve, a 21 kilometre oxbow channel of the Yangtze River (Liu et al. 1998). Less than seven months later her carcass was found entangled in the escape-prevention net at the outlet of the reserve. At that time, one other baiji was in captivity - a male (Qi Qi) that had been rescued from fishing gear and rehabilitated in 1980. This animal remained in its dolphinarium tank at the Institute of Hydrobiology of the Chinese Academy of Sciences in Wuhan until it died in 2002. At the time of this writing (August 2004; update in April 2007), no Baiji were in either of the semi-natural reserves or in the dolphinarium at Wuhan.

Scientific opinion has been divided on how to proceed with baiji conservation efforts. The Scientific Committee of the International Whaling Commission reviewed the status of the baiji in 2000, but members were unable to reach consensus on whether further attempts at live-capture should or should not be made (IWC 2001). The IUCN SSC Cetacean Specialist Group recommended in 2003 that: available resources should be devoted to eliminating the known threats to the species in its natural habitat; immediate action should be taken at national, provincial and local levels to fully enforce the bans on rolling hooks and electric fishing; and if the capture/translocation effort continues, capture operations should be improved to prevent dolphin injury or mortality, water quality in the reserve should be kept at a high standard and finless porpoises should be removed to ensure against deleterious interactions between them and the dolphin(s) (Reeves et al. 2003). The Chinese Ministry of Agriculture has developed a baiji conservation plan emphasizing the ex situ approach (Ministry of Agriculture 2001, Wang and Zhang 2002).

With the intention of improving the status of fishery resources, the central Chinese government has, since 2001, banned fishing in the entire middle and lower reaches of the Yangtze River (including appended lakes and tributaries) between 1 April and 30 June. This measure, if effective, could give some seasonal relief to baiji from one of the more serious lethal threats to their survival. In addition, serious efforts have been made in recent years to protect baiji and improve their habitat in the Xin-Luo National Baiji Reserve (established in 1992) and in two smaller reserves run by provincial governments (Zhenjiang and Tongling sections). In the Xin-Luo Reserve patrol boats monitor fishing activity, collect baiji sightings, rescue injured animals, and investigate dolphin deaths. Several shore-based monitoring sites have been established in the reserve to observe baiji. Perhaps the most important work carried out by reserve staff is that of enforcing the ban on electric fishing.

Further Reading

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  9. Chen, P. and Hua, Y. 1987. Projected impacts of the Three Gorges Dam on the Baiji, Lipotes vexillifer, and needs for conservation of the species. In: Translated by C. H. Perrin, Editted by W.F.Perrin (ed.), A Collection of Articles on the Impacts of the Three-Gorges Dam Project on Aquatic Ecosystem Along the Changjiang and Research on their Countermeasures, pp. 31-41. China Scientific Press, Beijing, China.
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Citation

Life, E. (2012). Chinese river dolphin. Retrieved from http://www.eoearth.org/view/article/51cbf0f17896bb431f6a3a48

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