Download Biodiversity Problems in Freshwater Ecosystems in China: Impact of

Biodiversity Problems in Freshwater Ecosystems in China:
Impact of Human Activities and
Loss of Biodiversity
Xie Ping and Chen Yiyu
(Institute of Hydrobiology, CAS, Wuhan 430072)
[Abstract] [Freshwater resources are fundamental] [Freshwater fishes are
important food resources]
[Lake ecosystems in the middle and lower basins
of the Yangtze River]
[Biodiversity problems of lake ecosystems]
[Conclusions]
[Literature Cited]
Abstract
This paper aimed to review present biodiversity problems in inland water ecosystems in China.
Decline in biodiversity of these inland waters is mainly caused by (1) shrinking and
fragmentation of lake ecosystems due to continuous subsidence of mud from river water and
extensive reclamation of farmland from lakes in the east regions, (2) destruction of lake-river
ecosystem by severance of lakes from the river, (3) reckless over fishing, (4) secondary
extinction following destruction of climax macrophyte communities, (5) deterioration of
ecological environment due to chemical pollution and accelerated eutrophication in urban waters.
KEY WORDS: Freshwater resources, Biodiversity problems, Basins of Yangtze River, Lake
ecosystems.
The earth's biodiversity and other natural resources provide many economic and social benefits
to mankind. Effective programs for sustainable human development must therefore incorporate
conservation objectives (Groombridge, 1992). China has abundant inland water bodies and a
relatively well developed freshwater fishing industry. The Yangtze River basin (a complex riverlakes ecosystem) is the most important fishing base in China. Over the past few decades, loss of
biodiversity has been accelerated by a series of direct and indirect effects and agencies. So, it is
badly needed to review the problems and threats that now face biodiversity
and to evaluate the potential ecological impact of the losses to mankind.
Freshwater resources are fundamental
Water and atmosphere are the most fundamental materials of the world for the existence of
humans and all other organisms. Water covers 2/3 of the earth's surface and is the most abundant
structural component of organisms. Life is essentially based on the continuous exchange of water
between an organism and its environment. Freshwater constitutes only 3% of the total water of
the world; of which 77.2% is stored as ice, 22.4% as underground and soil water, and about 0.4%
is in lakes, rivers and other water bodies (i.e., pond, bogs, etc.) (IIED, 1987). Although
freshwater is much less abundant than salt water, it is the essential material for terrestrial
organisms and fundamental to the civilization of humans. It also serves as the bridge between
terrestrial and marine ecosystems. In recent years, at least 43 countries have experienced water
shortage, and one hundred million people are confronted with worse drinking water. At present,
water shortage has become one of the most serious global environmental problems which
threatens human society.
China is poor in water supply, with the average annual supply for each person around 2,600
tons, which is only 1/4 of the world's average (IIED, 1987). The quantity of freshwater resources
is also declining, while the demand for it is increasing; moreover, about half of the lakes have
already been polluted to some extent by the increasing industrialization, human and agricultural
wastes. Because increasing freshwater shortage is becoming an important limiting factor for the
economic growth and development of China, it is important for our existence to protect
freshwater resources.
Freshwater fishes are important food resources
Fish make up the most abundant group of vertebrates, and there are in excess of 22,000
described species. Global fish production exceeds that of cattle, sheep, poultry or eggs, and is the
largest source of either wild or domestic animal protein for the world's expanding human
population (Norse, 1992). Of total world fish landings in 1989, marine landings comprised
86.2% while inland fisheries (aquaculture and capture fisheries) accounted for the remaining
13.8% (FAO, 1991). In 1990, total fish landings in China was 1,236 tons, while inland fisheries
accounted for as high as 42%. Therefore, freshwater fishes comprised one of the fundamental
elements for the existence of Chinese people. There are around 8,400 described species of
freshwater fishes in the world, which comprise approximately 40% of total fish species. Around
1,500 species of freshwater fish have been described in Asia (Nelson, 1984). In China, there are
in excess of 800 primary freshwater fishes (those confined to freshwater), among which about
500 species are endemic.
It is estimated that there is around 100,000km3 of water for each marine species but only 15km3
for each freshwater species; and that the population level of a marine species may be around 109.
but ranges down to around 106 for freshwater species (Groombridge, 1992). Compared with
marine ecosystems, freshwater ecosystems are usually smaller, more isolated from each other,
and the distributions of freshwater fish species are more limited. Freshwater ecosystems are also
less stable, and much more susceptible to environmental disturbance. For example, more than
one decade ago in Lake Luguhu (located in the intersectional area between Sichuan and Yunnan
provinces), local people had tried to introduce grass carp. However, by mistake they introduced
Pseudorasbora parva, which not only have little commercial value but also made three species
of Schizothoracine fishes endangered to near extinction (Liang, pers. comm.).
It is estimated that at least 20% (ca. 1,800 species) of the world's freshwater fish species are
seriously threatened or extinct, which is mainly caused by habitat modification (competition for
water, drainage, pollution), introduced species and commercial exploitation (Groombridge,
1992). In North America, nearly 1/3 of the total fish species are endangered, threatened or listed
as species of special concern (Williams et al., 1989). In China, there are 92 vulnerable of
endangered species of freshwater fishes which account for 10% of the total number of freshwater
fish; Cyprinus yilongensis, an endemic species in Yunnan Province, has become extinct, and
Psephurs gladius, Macrura reevesi and Hucho bleekeri are in danger of extinction (Le, 1995a,b).
Lake ecosystems in the middle and lower basins of the Yangtze River
The total surface area of all Chinese lakes is around 74,300km2, of which 42% is in humid
eastern China. The Yangtze River, located in the eastern plain, is the longest river in China and
the third longest river in the world. It has a total length of more than 6,300km. The middle and
lower basins of the Yangtze are one of the major distribution areas of freshwater lakes in China,
and the surface area of lakes constitutes around 1/8 of the total surface area of this region.
The Yangtze basin is the most important commercial fishing base in China with a fish yield
comprising around 2/3 of the total (Liu and He, 1992). In addition, waters of the Yangtze basins
are not only essential for water supplies (drinking water, irrigation, etc.) but also for many other
purposes such as recreation, and are therefore, very important for the economic development.
The middle and lower basins of the Yangtze River are influenced by the wet monsoon, and the
lakes of the basin were formed by flood of the river in the Late Tertiary. These lakes are shallow
(without thermal stratification), and interlaced with the main river and its branches into a unique
complex river-lakes ecosystem. These shallow lakes usually have a high productivity, abundant
vegetation cover, and a developed littoral zone communities. Because of the differences between
the river and the lakes, and the flooding caused by the wet monsoon there are obvious changes in
water level. In this environment have evolved unique migrating fish, for example:
Hypophthalmichthys molitrix, Aristichys nobilis, Ctenopharyngodon idellus, Mylopharyngodon
piceus, Ochetobius elongatus, Luciobrama macrocephalus, Squaliobarbus curriculus, and
Parabramis pekinensis. Among these are some of major commercial importance in China and
the world (The Fourth Laboratory of the Institute and the Tunghu Fish Farm, 1976). In the
Yangtze basin, there are about 300 fish species, of which more than half belong to the
Cyprinidae, the most commercially important fishes are also cyprinids (Liu and He, 1992). The
Yangtze basins are considered to be the center of origin and evolution of many freshwater fishes
in East Asia, preserving some remnant fish species (Cao and Chen, pers. comm.). Natural lakes
of the Yangtze basins, superior in water quality and abundant in species diversity, provide
essential freshwater resources for our existence.
Biodiversity problems of lake ecosystems
For several decades, inappropriate construction of dikes, dams and levees, unreasonable fishing
and fishery management, and the extremely strong pressure of the rapidly increasing human
population on lake ecosystems, have brought severe damage to the biodiversity from genetic to
ecosystem levels. This has resulted in the destruction of many natural resources of the lakes and
have posed a threat to the stability of our society and the sustainable development of the
economy.
1. Shrinking and fragmentation of lake ecosystems
Fragmentation of lakes by continuous subsidence of mud from river water and by extensive
reclamation of farmland from the lakes is a serious problem in China. Not only are the lakes in
the western part of China shrinking, but those in the eastern part are also contracting. In the
western regions, drought has fragmented many lakes into smaller lakes (Shi, 1989). While in the
eastern regions, shrinking of lakes is mainly caused by subsidence of mud from river water, and
by reclamation of farmland from lakes. In the eastern part of China, the superior natural
conditions for agriculture has been accompanied with a rapid increase in human population, and
consequently a rapid decline in land area per capita, so conversion of lakes for farmland has
become an historical by-product. For example, the total surface area of Lake Dongtin was
4,350km2 in 1949, but declined to 2,619km2 in 1983, due to continuous subsidence of river water
and extensive reclamation of farmland from the lake. The total surface area of Lake Honghu was
about 760km2 in the early 1950's, but subsequent portioning and reclamation work in the 1960's
and 1970's around the lake caused the continual shrinkage of the surface area of the lake to
350km2 of 1979. The Gianghan Plain contained 1,066 various sized lakes (surface area of
8,300km2 ), however, by the early 1980's, only 309 lakes (surface area of 5,600km2) were left
due to similar reasons (Shi, et al., 1985).
Welcomme (1979) reported that the number of fish species present in subtropical and tropical
rivers was highly correlated with the area of the river basin. Temperate rivers showed a similar
pattern, although the number of species rises more steeply with increasing basin area in tropical
systems than in higher latitudes. Two factors are important here: (1) the area of a lake sets an
upper limit to the maximum population size of each fish species and (2) small populations are
inherently more prone to extinction than large ones. From this alone it can be predicted that
shrinking of lake ecosystems will contract the living spaces of many freshwater species, and
therefore make more and more fish species endangered or extinct.
2. Destruction of lake-river ecosystem by severance of lakes from the Yangtze River
Severance of lakes from the river by construction of sluices and dikes have led to the
impoverishment of the natural fish resource--especially of migratory fishes--causing the lakes to
be dominated by species of small size. The Yangtze basin was originally a network of water
systems, including all of the large and small tributaries of the river, and many interconnected
shallow lakes. This complex river-lakes system provided superior living conditions for many
commercially important migratory fish species (including four domestic carp) which can spawn
only in the river and regularly migrate into lakes for feeding (Fish Laboratory, 1976). Over the
past decades, most lakes have been artificially severed from the river by hydroelectric and
irrigation projects, and as a result, the migratory fish can no longer enter into these lakes from
the river. This has lead to a sharp decline of their population size in both the lakes and the river.
In the middle and lower region of the Yangtze River, there averages around a hundred fish
species in natural lakes, but only 30-40 species in severed lakes. For instance, according to a
survey of fish species made in the 1990's in Honghu Lake, there were no less than 90 species in
the lake. In 1958, a sluice was constructed in the canal linking the lake with the river, thus
severing the intercommunication between the river and the lake. The survey in 1964 listed 74
species, in 1981-1982, 54 species, of which only 33 species were obtained from the lake, while
the remaining 21 species were riverine fishes carried into the lake during the channeling of the
Changjiang River water for the purpose of irrigation.
There is also a shortage of large-sized economic fish species which are mostly migratory
between the lake and the river (Honghu Research Group, 1991). Fishery resources of the three
domestic carp (siluer, bighead and grass carp) in the Yangtze River are also decreasing: the catch
of marketable-sized fishes in the 1980's was just half as much as that in the 1950's, whereas the
catch of natural fries was only one quarter as much as that in the 1960's. Changes in composition
of the catch also occurred: proportion of migratory fishes declined, whereas that of small-sized
lake-dwelling species increased (Li, et al., 1990).
Fingerlings of the four domestic carp used as stocking are now mainly from artificial
reproduction, but retrogression due to successive inbreeding has occurred (i.e., both growth and
mature age decline, adult fish become smaller, and incidence of diseases become higher). For
example, in natural populations of silver carp, the mature age of females is 3-4 years with an
average body weight of 4.85kg, and the mature age of males is 3 years with a average body
weight of 3.81kg. After inbreeding for five generations, the mature age of females declined to 2
years with a body weight of only 1.25kg (the minimum reached as low as 0.3kg) and the mature
age of males declined to one year with a body weight of only 0.69kg. Moreover, the inbreeding
offsprings had a higher malformation rate, a weaker constitution, and an eleven times higher
incidence of diseases. Therefore, it is harmful to inbreed for many generations, and it is essential
to restore the population by natural fingerlings. At present, adult fishes of the Yangtze River are
mainly from Lake Boyang and Lake Dongtin which have not yet been severed from the river,
and fate of these two lakes remains unclear (Liang, pers. comm). Severance of lakes from the
river by hydroelectric and irrigation projects has changed or disrupted dispersal and migration of
drastic changes in environments will accelerate distinction of remnant species, and consequently
decrease the abundant biodiversity.
3. Decline in biodiversity of fish species by reckless over fishing
Over fishing is commonly occurring in large lakes which are too large to cultivate fish and
manage fisheries efficiently. In addition to the severance of lake from the river, reckless over
fishing of natural fish populations has resulted in severe decline of species diversity, and
decreased drastically the population sizes of commercially important large-sized fish species
(mostly migratory fishes). Consequently, a lack of top consumers (carnivores) has usually caused
an explosive population increase of small-sized fishes (swamping also favors small sized
species), leading to a low fish yield, low fish quality, and low profit (Liang, pers. comm.).
For instance, fish production of Honghu Lake witnessed a steady decline. In the 1950's, the
annual fish yield was around 10,000 tons and the dominant species were the four-domestic-carp,
Cyprinus carpio and Parabramis pekinensis. However, excessive overfishing and inadequate
protection of the spawners caused the diminution both in the size of fish species and in the size
of individual fish, the lake being dominated by species of small size as well as by population of
stunted growth. In the 1980's, the annual fish yield declined to 3,000-4,000 tons, and 87% were
composed of the small-sized Carassium auratus auratus, Pseudobagrus fulvidraco and Culter
erythropterus (Honghu Research Goup, 1991).
In Lake Dongtin, the maximum recorded annual fish yield reached as high as 45,000 tons, and
the average annual yield was 30,700 tons in the 1950's, but declined to 15,000 tons in the 1980's.
The composition of fish yield also changed obviously: the proportion of migrating fishes
declined (mainly the four domestic carp), while that of lake-dwelling fishes (Cyprinus carpio,
Carassium auratus auratus and Silurus asotus) greatly increased. Of the major economic fishes
captured, the proportion of young ages increased and the average individual size of a certain age
was also decreased. A large number of young individuals and small-sized species became the
targets of fishing (Shan, et al., 1990).
A quite similar phenomenon also occur in some of the lakes of the middle and lower basins of
the Yangtze River such as in Lake Caohu, Lake Taihu and Lake Hongzhe, where three smallsized species of Coilia became dominant (Liang, pers. comm.; Shun & Huang, 1993).
4. Seconday Extinction following destruction of climax macrophyte communities
Over-stocking of plant-eating carps has usually caused severe destruction of climax
macrophyte communities, and consequently led to a series of extinction of animal species. Like
our ancestors who had advanced from collecting wild plants and animals to cultivating crops and
domestic animals, artificial breeding, stocking and cultivating fish have developed rapidly. We
have succeeded in changing the fish composition for our purposes and cultivating some
commercially important fish species. This kind of fishery has applied not only to ponds but also
to small/middle-sized lakes (especially urban lakes), and has made it possible to greatly increase
fish yield, and to lessen the danger of over-capture on natural populations of some species.
However, it has been accompanied with serious problems. In order to get short-term profit overstocking of fish has led to overgrazing of prey organisms, which has conversely exerted great
impact on the whole ecosystem. The most significant events are the destruction of vegetation
cover, especially submerged macrophytes, and the dominance of increased r-selected organisms.
In many lakes, the over-stocking of plant-eating carp (especially grass carp) has usually led to
destruction of macrophyte communities, and led to the shift of dominant primary producers from
macrophytes to phytoplankton. For instance, in the Guozheng area of Lake Donghu, the biomass
of macrophytes was as high as 1,779.8g/m2, but declined to 5.8g/m2, which was mainly due to
over-stocking of the grass carp. The high destructive power of grass carp on macrophytes is not
only due to their low digestion of macrophytes but also because the grass carp suppress the
recovery of macrophytes by grazing on new shoots. To macrophytes, algae are r-selected species
with a small body and a high turnover rate, and their ability to store nutrients is low. Therefore,
in lakes dominated by macrophytes, since a lot of nutrients are stored in macrophytes, the growth
of algae is suppressed, and the water is clear. This process is sometimes referred to as the
cleanup ability of macrophytes. As the abundance of macrophytes declines, nutrients stored in
macrophytes are released into lake water by grazing and excretion of the grass carp. This favors
the growth of phytoplankton. Moreover, increased phytoplankton biomass decreases both water
transparency and compensative depth of macrophytes, which in return decreases living extent of
the macrophytes. Such a vicious circle usually leads to less and less macrophytes of even their
extinction. Now, in the Guozheng area of Lake Donghu, the climax macrophyte community in
the 1950's has disappeared completely, and consequently, it is followed by secondary succession
of the primary producer community in which the dominants are r-selected algae, which is just
like the consequences of deforestation for agriculture (Liang, pers. comm.).
Secondary extinction. Macrophyte communities are associated with many periphyton and
mollusc, and also serve both as living space and as the substrata for the spawning of many fishes.
Therefore, an abundant macrophyte community is accompanied with a high biodiversity of the
whole community of plants and animals. The destruction of macrophytes not only leads to the
crash of the grass carp populations, but also causes secondary extinction of those organisms
depending on these macrophytes and of those fish associated with these directly-related
organisms. For example, with the disappearance of macrophytes, many periphytons and molluscs
are prone to extinction. This causes the spawning substrata of Cyprinus carpio, Carassium
auratus and Ophicephalus argus to also be decreased. The destruction of living environments for
molluscs then results in the decline of the available food for Cyprinus carpio and
Mylopharyngogon piceus. The dominance of grass carp is then replaced by filter-feeding
planktivorous fishes, and so on.
Decline in stability of ecosystems. Disappearance of macrophytes not only causes increase in
nutrient concentrations, but also leads to obvious decline in biodiversity of plankton community.
In four lake areas (with different nutrient levels) of Lake Donghu, three biodiversity indicies
(Margalef, Sympson and Shannon-Weaver) and the number of species of diatoms showed
obvious negative relationships with nutrient levels (Lei Anping, Unpubl.). In two sampling
stations of Lake Donghu, the Margalef Index of rotifers in 1991 (with high nutrient levels) was
only 1/3 that in 1992 (with low nutrient levels). A similar decline in species number was also
observed, and eutrophication of the lake decreased the biodiversity of rotifers (Zhuge Yan,
Unpubl.). Similar phenomenon might have occurred to other groups of plankton.
However, it remains unknown why eutrophication decreases biodiversity of plankton
communities. On the other hand, in hypertrophic waters (probably due to low biodiversity)
stability of the systems declines severely, and an outbreak of a few algal species, typically the
cyanobacterium water bloom, frequently occurs. In recent years, the frequent outburst of blood
poisoning fish disease by bacteria in the lakes of the middle and lower regions of the Yangtze
River is probably related to the simplification of the aquatic community (it is also possibly
attributed by too high fish stocking density and decreasing water quality). This is very similar to
the frequent outburst of insect or disease in the highly-simplified agricultural ecosystems with
only one or a few crops.
5. Chemical pollution and accelerated eutrophication in urban lakes
In terrestrial ecosystems, human agricultural activities usually lead to decline in soil nutrients.
From southern to northern parts of China, nutrient concentrations in the soil cultivated for 200500 years, are only half that in the original soil covered with primary vegetation (Heilongjiang
Term, 1982). However, during the ontogeny of a lake, organic and inorganic nutrients from the
surrounding terrestrial ecosystems accumulates continuously. Trophic status of the lake changes
from oligotrophic to eutrophic, and the lake finally appears as land. The process of natural
eutrophication is very slow, usually on the time scale of centuries or more. But in recent decades
(especially in many urban lakes) the rapid increase in the human population around lakes has
resulted in outpouring of untreated industry and organic wastes into the lakes. Also because of
unreasonable fishery management, eutrophication in these lakes have been accelerated at an
extremely fast rate (i.e., it only needs decades, or even several years to change the lakes from
mesotrophic to hypertrophic levels). Lake Donghu in Wuhan City and Lake Xuanwu in Nankin
City are good examples of this. The water in lake ecosystems is directly comparable to the soil in
terrestrial ecosystems. Soil is important because it supports terrestrial animals and plants.
However, water in freshwater ecosystems is important not only because it provides aquatic food
but also because it supplies freshwater resources. Severe eutrophication in aquatic ecosystems
results in destruction of water supply, and although productivity of the ecosystem may be high,
decreasing water quality may be a great threat to human health.
At present, nearly all urban lakes have been seriously eutrophicated. This is not only due to the
rapid increase in surrounding human population, but also related with unreasonable fish
cultivation. Overstocking of plant-eating carp has resulted in the destruction of submerged
macrophytes. This practice is more or less intentional because it is thought that the deforestation
by grass carp not only makes people get high fish yield, but also increases the fish yield of the
planktivorous silver and bighead carp (as more nitrogen and phosphorous change into plankton
biomass). For example, in 1963 in the Guozheng area of Lake Donghu, the biomass of
macrophytes was 1779.8 g/m2, and phytoplankton production was only 1 g/m2/day. However, in
1975, the biomass of macrophytes declined to 5.8 g/m2, while phytoplankton production
increased to 4.1 g 0.2/m2 (Chen, 1989). During the same period, fish yield of Lake Donghu
increased from 93.8 to 276.0kg/ha (Liu, 1984), and proportion of silver and bighead carp was
83% (Section of Fish Ecology, 1976) (now more than 98%). On the other hand, water quality of
Lake Donghu became worse and worse: low transparency, outburst of cyanobacterium water
bloom, stinking odor of the polluted lake water (Jao & Zhang, 1980). These decreased the lakes
multi-functions such as providing drinking water supply and recreation.
Recent studies further indicate that algal blooms (specifically, microcystins) a symptom of lake
eutrophication, are harmful to the human liver (Falconer, 1983; Hasser, 1989; Mirura, 1991;
Runneger, 1987, 1991). Microcystins not only inhibits the activity of protein phosphates, but also
acts as a tumor promoter (Erikson, 1990; Honkanen, 1990; Matsushima, 1990; NishiwakiMatsushima, 1991; Yoshizawa, 1990), and is a health threat to humans..
Conclusions
Habitat loss, modification or fragmentation, reckless overfishing, overstocking of plant-eating
carp and deterioration of the ecological environment appears to be the most serious current
threats to biodiversity in freshwater lakes and species are faced by several of these threats
operating simultaneously. Generally, aquatic ecosystems have received little attention in
comparison with terrestrial ecosystems, and only a few scattered surveys (mainly on fish) have
so far been conducted. Severe decline in species diversity of fish, coupled with inadequate
knowledge of freshwater faunas, indicates that biological diversity in aquatic systems require
increased conservation attention.
Acknowledgments
We wish to express deep thanks to Prof. Liang Yangling who kindly provided the unpublished
manuscript titled: "On the current status and the future of Chinese fisheries from ecological
viewpoint." Thanks are also to Mmes Lei Anping and Zhuge Yan for the kind provision of their
unpublished data.
Literature Cited
Chen, H. D. 1989. Acta Hydrobiol Sinica 13:359.
Eriksson, J. E., et al.. 1990. Biochem Biophys Res Comm 173(3): 1347.
Falconer, I. R., et al. 1983. Med J Austral 1: 511.
FAO. 1991. FAO Yearbook Fishery Statistics: Catches and Landings 1989. Vol. 68, Rome: FAO.
Fish Laboratory, Institute of Hydrobiology, Hubei Province. 1976. Fishes in the Yangtze River
(in Chinese). Science Press, Beijing.
Fourth Laboratory, 1976. Institute of Hydrobiology and the Tunghu State. Fish Farm in Wuhan
(in Chinese). Acta Hydrobiol Sinica 6:5.
Groombridge, B. 1992. Global Biodiversity, Status of the Earths Living Resources. Chapman &
Hall, London.
Hasser, S. B., et al.. 1989. Vet Pathol. 26: 246.
Heilongjiang Term, Nangjiang Soil Research Institute. 1982. Soil Resources in HeilongJiang
Province and North-Eastern part of the Inner Mongolia Autonomous Region (in Chinese).
Science Press, Beijing.
Honghu Research Group, Institute of Hydrobiology, Academic Sinica. 1991. Studies on
Comprehensive Exploitation of Aquatic Biological Productivity and Improvement of Ecological
Environment in Lake Honghu (in Chinese with English abstract). China Oceanogr. Press, Beijing.
Honkanen, R. E., et al.. 1990. J. Biol Chen 256: 19401.
IIED (The International Institute for Environment and Development and World Resources
Institute). 1987. World Resources 1987. Basic Books, Inc., New York.
Jao, C. C. & Z.S. Zhang. 1980. Acta Hydrobiol Sinica 7:1.
Le, P.Q. 1995a. Freshwater fishery 25:22.
Le. P.Q. 1995b. Lake Science 7:271.
Le, S.F., et al. 1990. Comprehensive Genetic Study on Chinese Carp (in Chinese with English
abstract). Shanghai Scientific & Technical Publishers, Shanghai.
Liu, J. K. 1984. Lakes of the middle and lower basins of the Changjiang (China). In: F. B. Taub
(ed.): Lakes and Reservoirs: 331.
Liu, J. K. & B.W. He. 1992. Cultivation of the Chinese Freshwater Fishes (3rd ed., in Chinese).
Science Press, Beijing.
Matsushima, et al.. 1990. Biochem Biophys Res Comm. 171(2):867.
Mirura, G. A. 1991. Toxicon 29(3): 337.
Nelson, J. S. 1984. Fishes of the world (2nd ed.). John Wiley and Son, New York.
Nishiwaki-Matsushima, R. Jpn 1991. J Cancer Res 82: 993.
Norse, E. A. 1992. Marine biological diversity strategy and action plan, Center for Marine
Conservation, Washington, D. C.
Runneger, M. T. C. 1987. Toxicon 25(11):1235.
Runneger, M. T. C. 1991. The uptake of the cyanobacterial hepatotoxin microcystin by isolated
rat hepatocytes, Toxicon 29: 43.
Section of Fish Ecology, Fourth Laboratory, Institute of Hydrobiology, Hupei Province. 1976.
Acta Hydrobiol sinica 6: 16.
Shi, C. X. (ed.). 1989. A General Outline of Chinese Lakes (in Chinese). Science Press, Beijing
Shun, S. C. & Y.P. Huang (ed.). 1993. Taihu Lake (in Chinese). China Ocean Press, Beijing.
Welcomme, R. L. 1979. Fisheries ecology of floodplain rivers. Longman, London & New York.
Williams, J. E. et al., 1989. S. fisheries (Bethesda) 14(6):2.
Yoshizawa, S, et al.. 1990. J Cancer Res. Clin. Oncol. 116:609.