Abstract

This paper reports the population status of the endangered Chinese River dolphin or baiji, Lipotes vexillifer, the impacts of the Three-Gorges Project on this animal, and the factors causing the population decline as well as protective measures adopted in recent years, such as semi-natural reserve, studies on reproduction under captive rearing conditions and natural reserve as well as their advances.

Introduction

The Chinese river dolphin or baiji (Lipotes vexillifer), which might be the most endangered cetacean in the world, lives only in the mainstream of the middle and lower reaches of the Changjiang (Yangtze River), an overall distance of about 1600 kilometers. Since 1975, the Institute of Hydrobiology of the Chinese Academy of Sciences has carried out long-term and systematic studies on baiji. These studies preliminarily clarified the distribution, population size and movement as well as the factors causing the animal unnatural death. A live specimen of baiji has been successfully kept in captivity in the institute since 1980. Overall studies on ecology, reproductive biology, behavioral biology, physiology, biochemistry and bio-acoustics, etc. have been carried out. On the basis of this work, the institute recommended three main measures for protecting baiji, 1) establishment of semi-natural reserves, 2) intensifying studies on reproduction under captive rearing conditions and 3) establishment of natural reserves. With close coordination between departments of fisheries and environmental protection as well as local government, much work has been done on these three main measures.

The Life Habit of Baiji

According to the recent information from the IUCN Red Data Book in 1991, baiji, Lipotes vexillifer, belongs to Subfamily Lipotinae, Family Pontoporiidae, Superfamily Platanistoidea, suborder Odontoceti, Order Cetacea.

Male of four years and female of eight years can be sexually mature. The high peak of mating occurs from March to May and the pregnancy lasts 10 to 11 months. The body length of newly born calf is about 90cm and body weight is about 20kg. The body length of the mature baiji can be over Im and body weight may be over 200kg. Preliminarily estimated, the life-span of baiji is around 30 years. Baiji are frequently seen moving about in the Changjiang River in small groups, usually consisting of two to six animals. A group of 16 is the largest groups that have been seen. When they swim together, one adult is in the lead, calies or juveniles are in the middle and another adult is at the rear. Baiji swim forward in the quiet water areas of 3-4m in Departmenth when they move upstream, and swim downstream along the main course. The swimming velocities are 4­5km/hr upstream and 10-15km/hr downstream, with maximum of 40km/hr in short time. Baiji feeds on freshwater fishes. The daily intake of food in captivity averages 8-10% of body weight (Chen et al., 1989). The large counter-current eddies are the habitat of baiji. A typical large counter-current eddy consists of cast-net area, boundary area, still-water area, back-current area and cross-current area (Hua et al, 1989), where water Departmenth usually reaches over 4-6m and fish is abundant.

Status of the Population Size of Baiji

Before 1950s, baiji was widely distributed in the Changjiang. Since 1960s, its population size has rapidly declined. On the "Workshop on the Biology and conservation of the River Dolphins", which was held in Institute of Hydrobiology, Wuhan in October, 1986, we reported that there was approximately 300 baiji surviving in the river (Chen et al, 1986). Since then, we have made 15 investigations in the middle and lower reaches of the river, 330 days in total. The investigation methods have been improved. Depending on the surveying results and analysis, we estimate that the population size of baiji has fallen to approximately 200 individuals, among which half is distributed in the sections of the Middle reaches of the river (Figure1). Baiji gives birth every two years and usually has one young at each birth. Its sexual ratio is approximately 1:1. The female reaches maturity at 8 years old and pregnant females comprise about 30% of the female group. Because of this low reproductive rate and the scattered nature of the few surviving dolphins as well as the complex environment in the Changjiang, the species cannot presently increase or be maintained. The factors causing such a serious situation are mainly as follows:

1.  Heavy use of harmful fishing gears is the direct factor that causes baiji accidental injury. According to our incomplete data, among baiji deaths of 100 individuals from the 1950s to the early 1990s, half of them were accidentally killed by rolling-hook. Other fishing gear like fishing by using trap net, electricity, and explosives, etc., also killed the dolphins. Twenty individuals were accidentally killed in 1984 alone. Since then, the use of harmful fishing gears has been reduced year by year due to an extensive education program and a law for protection formulated by the Chinese government. Unnatural deaths of baiji have been reduced but still occur.

2.  Destruction of the existing environment is an indirect factor causing the decline of baiji. The increasing construction of dams and floodgates has resulted in blockages between the river and lakes, so that fish resources have been reduced markedly and the ecological environment which had been favorable for dolphins, such as counter-current areas around sandbars and entrances to the river by streams, has been destroyed.

3.  The rapid development of navigation business not only causes baiji unnatural deaths (kills dolphins by propeller and by explosion when clearing the navigation channel), but also leads to heavy noise which might seriously interferes the normal activities of baiji. For example, the Chenglingji section next to the mouth of Dongting Lake is an ideal environment for baiji, but, there are too many ships going up and down this narrow channel. The rumble of ship engines is deafening and the animals' normal activities are seriously altered. (Chen et al.,1987; Zhou et al.,1989).

4.  Water pollution of the Changjiang River has caused direct effect on baiji as well as on fish.

We should clearly know that human activities, along with the development of economic construction, have increasingly imperilled baiji population. Now baiji population is still declining. Therefore, conservation of baiji is urgent and arduous.

Impacts of Three Gorges Project on Baiji

What kinds of impact on baiji will be made by proposed Three-Gorges Hydroelectric Project? How to quantitively and qualitatively evaluate the degree of such impacts? Entrusted by the China National Scientific and Technological Commission, we undertook the research project named "Evaluation of the Impacts of the Three Gorges Project on Baiji and Its Conservative Strategy", which was completed in 1990. The comprehensive evaluations are highlighted as follows: 1) By the impact of the river bed scour, the distribution range of baiji will move down from Zhicheng to Shishou, 160km downstream, accounting for 10% of the present length of distribution area and 5% of the baiji there will be forced to move down. 2) Since the navigation channel conditions will be improved, the number of transportation ships will be increased after the construction of Three-Gorges Dam, the rate of baiji killed by ship propellers may increase. 3) The impact on fish resources will indirectly affect the food resources of baiji. 4) Other vast changes of the environment, such as shifting of temperature, disappearing of some large counter-current water areas, etc., will also seriously affect baiji (Chen et al., 1981; 1992).

Recent Progress of Conservation and Management of Baiji

In view of a situation of imminent danger faced by baiji, the actual status of the Changjiang, and possible impacts from the proposed Three-Gorges Project, we have been carrying out the following urgent preservation measures for baiji:

1.  Establishment of Tian-E-Zhou semi-natural reserve.
In view of the difficulty of controlling open waters of the river, we selected Tian-E-Zhou which is a bypassed semicircular bend or so called oxbow in the middle reaches of the Changjiang near Shishou City, Hubei Province and covers 2666 ha of water area to make thorough studies (fig.2). The oxbow maintains a natural environment suitable for baiji existence; in fact, some dolphins used to move around there before it separated from the main stream of the river. From 1987 to 1988, we made investigations of geographical conditions, physio-chemical feature of aquatic environment and fish resources in Tian-E-Zhou oxbow (Zhang et al., 1992). That results show that it has the advantages of abundant fish resources, less human activities, no industrial pollution, and easy artificial control. After we clarified background data of water quality, food resources and hydrogeology of the oxbow (Tables 1, 2), we submitted the proposal " For Establishment of a Semi-Natural Reserve at Shishou for Conservation and Management of Baiji", in December, 1988, which had been approved by a group of scientists from Universities and Institutions and officers from the National Ministry of Agriculture and the National Bureau of Environment Protection. In March and April, 1990, we moved five black finless porpoises, Jiangzhu (the Chinese name, which means river pig), Neophocaena phocaenoides, among them 4 females and 1 male, into the oxbow to test if this area was indeed suitable for baiji. Two females were pregnant when they were caught and had two calves in May in the oxbow. Before long, one calf and the adult male were accidentally killed by rolling hooks (This kind of fishing gear will be prohibited to use after the establishment of the reserve). The remained four females and one calf have been healthy to the present, and they even did not try to leave the area when the oxbow was connected to the main stream during the flood seasons of 1990 and 1991. These test results show that the oxbow can provide sufficient suitable conditions for baiji living there. Now we have a mature and reliable plan to solve the key problems for establishing this semi-natural reserve such as the management of the reserve, transporting of baiji safely, and design of facilities for preventing the escape of baiji, etc. This plan has been approved by the government and the Ministry of Agriculture will conduct this plan soon (Zhang et al., 1992). Another smaller semi-natural reserve in Tongling in the lower reaches of the river is already under construction.
As the population number of baiji is so small, it does not allow for error in the protection work. Therefore, we suggest establishing the proposed semi-natural reserves as a test model for preserving baiji and enlarge such reserves when experience improves. We believe that if 2 to 3 groups numbering 10 to 20 individuals can be introduced into the oxbow mentioned above, it may be possible to effectively protect this endangered animal.

2.  Artificial reproductive conservation.
There are many examples showing that rare and endangered species can effectively be protected under captive rearing conditions. Though it is much more difficult to protect baiji by this method, it still is one of the effective measures, especially if we can apply what we learn from dolphins in captivity to the conservation and management of the population in wild and in semi-natural reserve. We have reared 4 baiji early or late, and one male among them named Qi Qi has been kept in captivity since 1980 and is still healthy (Chen et al., 1986, 1989). We completed basic studies on reproduction and accumulate much data. For example, we have been monitoring the serum testosterone (T) level of a captive male named Qi Qi for 3 years since 1988, ne sampling per month. The results show that T level of Qi Qi has obviously cyclical changes. It reaches its maximum from March to July, over 300ng/dl and minimum from August to September, below 100ng/dl. Meanwhile, we have been training Qi Qi for artificial collection of sperm, and up to now, Qi Qi can finish the necessary process for this collection following trainer's order, i.e. swims to and stops by the trainer, lies on its side or its back and, exposes its penis. We hope that a bank of sperm and body cells of baiji can be established in the near future.
In order to improve the conditions of rearing baiji in captivity and start a breeding program, we are building a new much improved rearing and reproductive facility, which includes a main hall (30m in diameter) consisting of one main pool and two auxiliary pools, a hall for reproduction (15m in diameter), a laboratory building, a guest house for visiting scientists, and a outdoor simulated ecological pool as well as control systems for water cycling, filtration, sterilization and temperature conditions. This facility, which will be formally operated by the end of this year, can keep 2-3 pairs of baiji in good rearing conditions for research and breeding program.
To keep animals healthy is critically important for breeding project. From our experiences by rearing baiji in captivity, we have know that: 1) Diseases of respiratory tract can be diagnosed by observing behavior, listening respiratory sound, smearing mucus from the blow hole, and measuring the body temperature and blood phase. It can be effectively prevented and cured by the combination of some Chinese traditional and western medicines. 2) Diseases of digestive tract can cause symptoms' such as poor appetite, decreasing feeding capacity, slow swimming, bad smell, and abnormal coloration on the coating of tongue and on the mucosa of the oral cavity. This can usually be treated by using Chinese traditional medicines. 3) Summer heat is very difficult to deal with for dolphins in Wuhan. With many year experiences, we now know how to help dolphins in a pool to safely pull through the horrible heat by using some kinds of Chinese medicines and changing the food composition.

3.  Establishment of Natural Reserve in Xin-Luo section.
Xin-Luo section (i.e. Honghu section) in the middle reaches of Changjiang is one of the two sections of the river representing the main distribution of baiji (the other one is Anqing section in lower reaches). it is possible to retard declination of baiji by setting up natural reserve by establishing administrative agencies, prohibiting the use of harmful fishing gear, and protecting the ecological environment in these sections.
Xin-Luo section of the Changjiang River is in the middle reaches, from Xintankou of Honghu to Luoshan of Honghu in Hubei Province, 135.5km in total length. This section of the river broadens out and meanders. Water Departmenth is about 25m and current velocity is 0.8-lm/sec. Banks are shallow and bars are numerous. There are many tributaries in this section. Projecting rocks along the banks control the water current direction. All these form a number of deep pools and large counter-current eddies which are frequented by baiji. The distribution density of baiji is much high than that in any section. The distribution of baiji in this section is relatively stable, too.
Xin-Luo section is established as a natural reserve for baiji, to conserve the existing population and habitat. This natural reserve has been approved and established by the government. Now two signboards with 14m high are set up at both ends of the section. One patrol boat with 150h/p is working in the section.
In short, much progress has been made on three measures we proposed for the conservation of baiji in recent years. As a direct result of this, a meeting called" An Overall Plan For Conservation of Baiji", convened by the Ministry of Agriculture, was held in Wuhan in December, 1991 for discussing an nationwide comprehensive programme and immediate actions to save baiji. The construction of semi-natural reserve and natural reserve was discussed in particular. The government would offer part of financial support.
There are still some difficulties for the conservation of baiji, for example, to safely catch dolphins, which is necessary for research like radio-tracking, and for moving dolphins into the semi-natural reserve and artificial rearing facility. Even we successfully captured two baijis before, we must use much man power and material resources since the environment conditions in the river are complicated, the number of baiji is few and catching methods are backward. In addition, we feel we need more and more exchanges of the information and ideas as well as personal between us and our colleague at home and abroad. This is extremely important since baiji is on such a fragile situation, we cannot make any mistake for the conservation work. As the way it always is, money is always a big problem. All these bring difficulties for the protection of baiji. Fortunately, the Chinese government lays great stress on protection of baiji and many people and organizations at home and abroad also show more and more concern for protecting this species. With more and more intensive international collaboration and much effort, we hope that this endangered species can be effectively preserved.

Note: TB = Total Bacteria; BB = Biomass of Bacteria; TC = Total Coliforms; PP =Phytoplankton; ZP = Zooplankton; DBe = Density of Benthon; BBe = Biomass ofBenthon; AP = Aquatic Plant; C - <= Chlorophyll-<; DMC = De-magnesium ChloropgyU; DOOWS = Day output of Oxygen at Water Surface (as O2 ); DOOCW =Daily output of Oxygen in the Column of Water (as O2).

Conclusion

The population of baiji is approximately 200 individuals at present and is continuously declining. Such a situation causes people to be seriously worried. The factors causing the rapid decline of its population are mainly from human activities which accidentally kill it. Although baiji has been listed as the protected animal of the first grade by the Chinese government and the appropriate law has been drawn up, it is difficult to avoid these factors causing its unnatural death and such situation will continuously be getting worse. Therefore, the establishment of semi-natural reserves and artificial rearing for protecting this endangered species is imperative. During the past twelve years, in order to protect baiji, department of scientific research, fisheries and environmental protection have done much work. Although the protective work has many difficulties, as long as the government attaches importance to this matter, management will be intensified and cooperative research strengthened; there still is hope for protection of this animal. On the contrary, it will be a serious mistake if there is any delay as baiji is in such an endangered situation. We hope that conservation of baiji will be concerned and supported by people in the world and all organizations of animal conservation.

Figure 1. Map of the middle and lower reaches of the Yangtze River, showing distribution and protected areas of the baiji.

Figure 2. The map of proposed semi-natural reserve at Tian-e-zhou Oxbow (Swan Oxbow)

References

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